Sep W8^ Biological Report 89(22) September 1989 h and Wildlife Service MARSH MANAGEMENT IN COASTAL LOUISIANA: EFFECTS AND ISSUES Proceedings of a Symposium DOCUMENT LIBRARY Woods Hole Oceano^rapfiic Institution Baton Rouge, LA June 7-10, 1988 Coastal Management Division J. Department of the Interior Louisiana Department of Natural Resources o" is 5= Ji eo- 1? t-D ! □ : r^ ■ m \ o . m - o = a _ a - m = □ Co-sponsored by: Louisiana Land and Exploration Company Tenncco Oil Company USDA Soil Conservation Service New Orleans District U.S. Army Corps of Engineers Louisiana Geological Survey LSU Governmental Services Institute Biological Report 89(22) September 1989 MARSH MANAGEMENT IN COASTAL LOUISIANA: EFFECTS AND ISSUES- PROCEEDINGS OF A SYMPOSIUM Edited by Walter G. Duffy U.S. Fish and Wildlife Service National Wetlands Research Center 1010 Gause Boulevard Slidell, LA 70458 and Darryl Clark Louisiana Department of Natural Resources Coastal Management Division P.O. Box 44487 Baton Rouge, LA 70804 U.S. Department of the Interior Fish and Wildlife Service Research and Development Washington, DC 20240 and Louisiana Department of Natural Resources Coastal Management Division Baton Rouge, LA 70804 DISCLAIMER The opinions, findings, conclusions, or recommendations expressed in this report do not necessarily reflect the views of Research and Development, Fish and Wildlife Service, U.S. Department of the Interior. The mention of trade names or commercial products does not constitute endorsement or a recommendation for use by the Federal Government. Duffy, W.G., and D. Clark, editors. 1989. Marsh management in coastal Louisiana: effects and issues-proceedings of a symposium. U.S. Fish and Wildlife Service and Louisiana Department of Natural Resources. U.S. Fish Wildl. Serv. Biol. Rep. 89(22). 378 pp. PREFACE This document is one of the U.S. Fish and Wildlife Service Biological Reports providing critical information to operational personnel, natural resource managers, and decisionmakers. The objective of this report is to present the proceedings of a symposium on "Marsh Management in Coastal Louisiana," held in Baton Rouge, LA, in June 1988. The symposium brought together a diverse group of more than 300 individuals to discuss the topic of marsh management in coastal wetland habitats, particularly the coastal wetlands of Louisiana. Speakers of the symposium represented many of the Federal and State agencies having scientific and regulatory responsibility for Louisiana's coastal wetlands; also present were public and private marsh managers, university scientists, consultants, and private citizens. Speakers for the symposium were solicited in an effort to realistically present the variety of views, opinions, and ideas presently surrounding the topic of marsh management in Louisiana. Papers were reviewed and edited with care to retain the views, opinions, and ideas of the speakers. Readers are encouraged to compare the sometimes contrasting opinions presented and draw their own conclusions. The opinions, views, and ideas presented in this report do not necessarily represent those of either the Louisiana Department of Natural Resources or the US. Fish and Wildlife Service. in CONVERSION TABLE Metric to U.S. Customary Multiply By To Obtain millimeters (mm) 0.03937 inches centimeters (cm) 0.3937 inches meters (m) 3.281 feet meters 0.5468 fathoms kilometers (km) 0.6214 statute miles kilometers 0.5396 nautical miles 2 square meters (m ) square kilometers (km ) 10.76 square feet 0.3861 square miles hectares (ha) 2.471 acres liters (L) cubic meters (m ) 0.2642 gallons 35.31 cubic feet cubic meters 0.0008110 acre-feet milligrams (mg) 0.00003527 ounces grams (g) 0.03527 ounces kilograms (kg) 2.205 pounds metric tons (t) 2205.0 pounds metric tons 1.102 short tons kilocalories (kcal) 3.968 British thermal units Celsius degrees (° C) 1.8(°C) + 32 U.S. Customary to Metric Fahrenheit degrees inches 25.40 millimeters inches 2.54 centimeters feet (ft) 0.3048 meters fathoms 1.829 meters statute miles (mi) 1.609 kilometers nautical miles (nmi) 1.852 kilometers square feet (ft2) 0.0929 square meters square miles (mi ) 2.590 square kilometers acres 0.4047 hectares gallons (gal) 3.785 liters cubic feet (ft ) 0.02831 cubic meters acre- feet 1233.0 cubic meters ounces (oz) 28350.0 milligrams ounces 28.35 grams pounds (lb) 0.4536 kilograms pounds 0.00045 metric tons short tons (ton) 0.9072 metric tons British thermal units (Btu) 0.2520 kilocalories Fahrenheit degrees (° F) 0.5556 (° F - 32) Celsius degrees IV CONTENTS Page PREFACE iu CONVERSION TABLE iv ACKNOWLEDGMENTS vii The Geological History of the Marshes of Coastal Louisiana, R. LeBlanc 1 Processes of Wetland Erosion in the Mississippi River Deltaic Plain, S. Gagliano and K. Wicker 28 Accreting Mudflats at the Mississippi River Delta: Sedimentation Rates and Vascular Plant Succession, D. White 49 Soils of Louisiana's Coastal Marsh, K. Murphy 58 Modeling Sediment Delivery to Louisiana Coastal Salt Marshes: Natural Processes and Options for Management, D. Reed 67 Response of Louisiana Gulf Coast Marshes to Saltwater Intrusion R. Pezeshki, R. DeLaune, W. Patrick, Jr., and B. Good 75 The Effect of Drying and Electrical Conductivity on Urease Activity in a Brackish Marsh, G. Sigua and W. Hudnall 86 Research and Policy Issues Regarding Coastal Wetland Impoundments: Lessons Learned in South Carolina, M. DeVoe and D. Baughman 98 Regulatory Procedures Impact Landowners' Management Programs, A Ensminger 107 Marsh Impoundments for the Management of Wildlife and Plants in Louisiana, R. Chabreck and G. Junkin 112 Vegetation and Salinity Changes Following the Installation of a Fixed Crest Weir at Avery Island, Louisiana (1982-86), B. Craft and D. Kleinpeter 120 Comparisons of Salinity, Hydrology, and Vegetation Characteristics Between Free-Flowing and Semi-Impounded Intermediate-to-Brackish Tidal Marsh Systems, J. Meeder 131 The Effects of Weirs on Plants and Wildlife in the Coastal Marshes of Louisiana, R. Chabreck and J. Nyman 142 Weirs and Their Effects in Coastal Louisiana Wetlands (Exclusive of Fisheries), R. Turner, J. Day, and J. Gosselink 151 Effects of Drawdown and Water Management on a Seriously Eroded Marsh, B. Lehto and J. Murphy 164 A Comparison of White Shrimp Production Within Actively Versus Passively Managed Semi-Impounded Marsh Nurseries, R. Paille, T. Hess, Jr., R. Moertle, and K. Guidry 170 Marsh Management and Fisheries on the State Wildlife Refuge- Overview and Beginning Study of the Effect of Weirs, M. Konikoff and H. Hoese 181 Threats to Coastal Fisheries, W. Herke and B. Rogers 1% Page Recreational Use of Management Units in Brackish Marsh, R. Davidson and R. Chabreck 213 Vegetative Marsh Management in Louisiana: Long-range Recommendations, B. Good 222 Introduction of Smooth Cordgrass on a New Site, F. Talbot and A. Ensminger 235 Vegetative Propagation of Giant Cutgrass for Fresh Marsh Erosion Control, J. Cutshall, R. Glennon, and L. Biles 239 One Company's Experiences with Wetlands Conservation, W. Berry and G. Voisin 242 Ecological Characterization of Jean Lafitte National Historical Park, Louisiana: Basis for a Management Plan, N. Taylor, J. Day, Jr, and G. Neusaenger 247 Results of an Intensive Marsh Management Program at Little Pecan Wildlife Management Area, T. Hess, Jr., R. Paille, R. Moertle, and K. Guidry 278 Cameron-Creole Watershed Management, B. DeLany 311 An Evaluation of the Tenneco LaTerre Mitigation Bank Management Plan, R. Simmering, B. Craft, J. Woodard, and D. Clark 319 Geographic Information System Applications for Marsh Management Plans, P. Bourgeois, J. Barras, B. Blackmon, and D. Clark 330 Experimental Marsh Management Impoundments, R. Turner, J. Cowan, I. Mendelssohn, G. Peterson, R. Shaw, C. Swarzenski, and E. Swenson 344 The Use of Basic Research in Wetland Management Decisions, I. Mendelssohn and K. McKee 354 A Legal Review of Some Louisiana Wetland Management Activities, J. Wilkins and M. Wascom 365 VI ACKNOWLEDGMENTS The symposium coordinators acknowledge the following for making significant contributions to the success of the conference and this proceedings: Mike Adams Jim Allen Horace Austin John Barras Bill Berry Bo Blackmon Don Boesch Pierre Bourgeois Col. Kent Brown Mark Chatry Coastal Management Division Staff Gary Couret John deMond Greg DuCote W.P. (Judge) Edwards Allan Ensminger Gaye Farris Dave Fruge Larry Handley Bill Hardeman Bill Herke Rocky Hinds Rebecca Howard Ted Joanen Peggy Keney Kirk Kilgen Sue Lauritzen Kelly McGuire Kai Midboe Ronnie Paille Edward Pendleton Joyce Rodberg JoAnn Rogers Peggy Rooney Rick Ruebsamen Rick Simmering Karen Sims Daisy Singleton Tenneco-LaTerre Staff Norm Thomas Billie Tripp Mike Tulles Beth Vairin Clark Vega Ron Ventola Deborah Wells Cam Wiik Jimmy Winston John Woodard vu THE GEOLOGICAL HISTORY OF THE MARSHES OF COASTAL LOUISIANA Rufus J. LeBlanc Owner, Rufe LeBlanc School of Clastic Sediments 3751 Underwood Street Houston, TX 77025 ABSTRACT The marshes of coastal southeast Louisiana occur over an area of about 6,600 mi2, and they constitute about 60% of the Mississippi River Deltaic Plain complex, the newest land added to the Gulf Coastal Region during the past few thousand years. Any local, State, or Federal program concerned with the management of these deltaic plain marshes must be based upon a firm understanding of the natural geological processes which created them. Part I of this paper consists of a brief description of the deltaic plain complex. Part II is con- cerned with the description of the coastal bays, sounds, transgressive barrier islands, and offshore shoals which are related to the delta complex. Part III discusses 51 significant papers on the delta complex which have been written during the past 58 years. Part IV is a brief summary of the origin and development of the coastal region of southeast Louisiana based upon the research outlined above. Illustrations show how the mighty Mississippi River created about 14,000 mi2 of new land in the Gulf of Mexico, in the form of a series of deltas, during the past 7,000 years. Attention is also focused on the natural processes of river diversion, delta abandonment, and compaction and subsidence of abandoned delta sediments, which permitted the gulf to move inland and reclaim about 7,000 mi2 of this new land. In spite of the massive research effort at Louisiana State University over a period of 58 years, there are still many citizens of coastal Louisiana who do not understand the basic principles of natural deltaic sedimentation and the concurrent loss of land that had been previously created by the deltas. Over 80% of the shorelines of coastal Louisiana are and should be under natural transgressive conditions today. Wherever humans choose to live upon the large deltas of the world they must be prepared to suffer the inevitable consequences of natural river diversions, delta abandonment, compaction and subsidence, and the great loss of land as the seas transgress over large portions of the deltas. INTRODUCTION The Mississippi River, one of the largest rivers of the world, drains all or part of 32 States stretching from Yellowstone National Park on the west to New York on the east, and from Min- nesota on the north to the Gulf of Mexico on the south. This river also drains parts of southern Alberta and Saskatchewan, Canada. This 1,300,000-mi2 drainage basin is shown on Figure 1. During the past 7,000 years, the sediments transported southward by this great river, under natural conditions, have created thousands of square miles of new land in the Gulf of Mexico which comprise the southeast part of Louisiana. The Mississippi River has changed its course, also under natural conditions, several times and as a result has constructed four deltas in the region B V 0X1 09 a 1 St a "3 V) s if between Vermilion Bay on the west and the Chandeleur Islands on the east (Figure 2). Most of this very extensive deltaic plain complex is presently known as the Louisiana Wetlands. DESCRIPTION OF THE DELTAIC PLAIN COMPLEX1 Each of the four large deltas (Teche, St. Bernard, Lafourche, and present delta shown on Figure 2) is characterized by distinct landforms, or components, which have their own unique character (Figure 2-A). Bayous and Natural Levees The highest land in southeast Louisiana is about 25 ft above sea level and occurs along the major bayous, which are remnants of much larger channels of the Mississippi River. Through the years river waters and sediments spilled over the banks of these channels to create natural levees which consist of well-drained soils. Swamps The second major component of the deltaic plains is the swamps which occur at lower elevations between the bayous and natural levees. The swamps cover an area of about 2,000 mi2 and include a large variety of trees and wildlife. Freshwater Marshes Seaward of the swamps the land is covered with freshwater marshes which lie only a few feet above sea level. These marshes are occasionally covered with brackish water; hence they are devoid of trees. There are over 1,600 mi2 of freshwater marshes in southeast Louisiana. Brackish and Saltwater Marshes The coastal part of the deltaic plain complex consists of brackish and saltwater marshes which comprise the most significant portion of the wetlands. These marshes cover an area of about 4,300 mi2 and they rise only a few inches above sea level. They include hundreds of small lakes, ponds, and small bayous. Inland Lakes Southeast Louisiana is well known for its beautiful lakes. Nine of the largest lakes, which are indicated on Figure 2 (by capital letters A through I), all originated in the same manner. About 30,000 years ago ice accumulated on North America as far south as southern Illinois and the level of the sea in the Gulf of Mexico dropped about 450 ft. Over 100 mi of the Continental Shelf off south Louisiana was exposed "under the sky" (Figure 3). About 15,000 years ago, as the ice began to melt, sea level began to rise. About 4,000 years ago sea level reached its present stand and most of southeast Louisiana was transgressed by the Gulf of Mexico to as far north as the latitude of Baton Rouge. When the Teche Delta was formed, it isolated what is now Grand Lake and Lake Verret from the gulf (Figure 2). The subsequent development of the St. Bernard Delta to the east isolated Lake Maurepas and Lake Pontchartrain from the gulf. Four other lakes (Lac des 1 Reader should refer to the Geological Map of Louisiana published by the Louisiana Geological Survey, Baton Rouge. a a a S 1 s a a. "5 43 (A o ©\ ^_- ~* §> •o < CI 3 to cS ■> . ^ u & \y c O 03 &ec.. a TV -~m a CO i •** 3 '<*> ** V I 3 s •m e 8 .a g a e a t 3 3 3 1 (A a 3 M Allemand, Lake Salvador, Lake Cataouatche, and Little Lake) are also portions of the gulf which were cut-off from the gulf by the formation of the St. Bernard, Lafourche, and present Mississippi Deltas. In summary, constructional processes of sedimentation have created these lakes. In contrast, major destructional processes created the coastal bays described below. PART II. DESCRIPTION OF COASTAL BAYS, SOUNDS, TRANSGRESSrVE BARRIER ISLANDS AND OFFSHORE SHOALS Coastal Bays The origin of the coastal, shallow water bays and sounds of southeast Louisiana was very different from the origin of the inland lakes. These coastal water bodies were developed during the past few thousands years as gulf waters transgressed over the abandoned, subsiding deltas. They are the products of nature's destructional forces. The compaction of delta sediments, following delta abandonment, caused the shorelines of Louisiana to move inland for about 50 mi over the Teche Delta, 35 mi over the St. Bernard Delta, and about 15-20 mi over the Lafourche Delta. Transgressions of the seas upon abandoned deltas are a perfectly natural geological process that has occurred all over the world for millions of years. Coastal Barrier Islands Coastal barrier islands are very common features in the world. Unfortunately, there is a great deal of confusion in the geological literature on barriers. It is very important to recognize that there are two basic types of barrier islands. One group, such as Galveston Island and Matagorda Island of the Texas coast, are "constructional features." This type of barrier is fed by longshore transport of sand and over a long period of geological time grows seaward by the process of "shoreface accretion." The second type of barrier island, such as the ones along the Louisiana coast shown on Figure 2, are the products of destructional processes. The Isles Dernieres and the Timbalier and East Timbalier Islands have been moving inland and westward since the Lafourche Delta was abandoned. Grand Island is moving northeast because of local eastward longshore currents along the west margin of the present Mississippi Delta. The Chandeleur Islands have been moving westward over the St. Bernard Delta. Offshore Shoals and Sounds There is a very significant relationship between the presence of nearshore shoals and sounds off the Louisiana coast and the abandoned deltaic plains. Recent sediment research during the early 1950's revealed that these broad sandy shoals and sounds are submarine topographic features which mark the former seaward portions of the Teche and St. Bernard Deltas. The bottom sediments within much of the shoal areas consist of transgressive marine sands and silts overlying organic-rich deltaic plain sediments. The south Louisiana deltaic plains and the adjacent shoals mark the results of a major battle between river power and ocean power. As will be demonstrated in the next part of this paper, while the mighty Mississippi River constructed about 14,000 mi2 of new land in the gulf waters, the gulf has in turn reclaimed about 7,000 mi2 of coastal marshlands according to the basic principles of deltaic sedimentation. PART III - SIGNIFICANT PAPERS ON THE MISSISSIPPI RT^ER DELTAIC PLAIN COMPLEX On the basis of 48 years of experience studying the geology of my native land, I have selected 37 papers on the geology of the Mississippi River Deltaic Plain Complex which I consider to be most significant. These selected references, together with my annotations, are included herein. I suggest that the reader should examine these references and annotations prior to reading the remaining portion of this paper. 1930 To 1952 There were only 10 significant papers published during this period (Figure 4). Eight of these 10 papers were written by geology professors associated with the School of Geology of Louisiana State University (LSU). 1953 To 1988 During this period, 27 additional significant papers were published by several LSU geology professors and geologists who received their educations from the LSU School of Geology. Most certainly, no one can fault this famous school for neglecting research on one of the largest deltaic systems in the world. No other delta system in the world has received this much attention. 50 40 (0 CC uj 30 Q. < 0- u. ° 2a • o z 10 19 30 '40 '50 '60 '70 1980 '8 YEARS 8 Figure 4. Cumulative number of significant geological papers on the Mississippi River Deltaic Plain complex published during the period 1930 to May 1988. Refer to text for discussion and analysis. 8 Why was this research conducted and who funded the research? The answers to those ques- tions lie in an analysis of references included herein. The first significant paper on "Building of the Mississippi Delta" was written by Professor Trowbridge of the State University of Iowa and funded by the U.S. Army Corps of Engineers. The next five significant papers were written by LSU professors, published by the Louisiana Geological Survey, and funded by the State of Louisiana. In June 1941, Dr. Harold N. Fisk and his associates at Louisiana State University began to conduct a geological investigation of the Mississippi Valley and its deltas for the Mississippi River Commission. This basic, early research was aimed at flood control and navigational problems within the vast Mississippi River system from Cairo, IL, to the gulf. This originally 2-year project continued for 7 years (Fisk 1944, 1954) and was funded by the U.S. Army Corps of Engineers. Something very interesting happened in the spring of 1948, 7 years after the Fisk project started: The Humble Oil Co. of Houston, TX, employed Fisk to conduct research on Recent sediments and the writer was invited to join the famous Shell Oil Co. research laboratory in Houston. Thus the type of research which was initiated for flood control and river navigational problems in 1941 now continued as two very impressive research projects aimed at the establishment of criteria for recognition of the depositional environments of ancient sandstone petroleum reservoirs. My former professor, and boss for 7 years, now became my tough competitor. This sandstone research effort by two major oil companies continued for over 25 years. Beginning in the mid-1950's several other oil companies also conducted research on the Mississippi Delta complex over a period of many years. However, Humble and Shell were well ahead of the pack. While the petroleum industry was busy studying the Mississippi Delta, research on the delta complex continued at LSU. Beginning in about 1952 the Coastal Studies Institute, funded by the U.S. Navy, was created. Dr. R. J. Russell was Director of this Institute. Many LSU geology graduates associated with this Institute published many papers. This group of scientists included R.S. Treadwell, J.R. Van Lopik, W.G. Mclntire, C.R. Kolb, W.A Welder, J.M. Coleman, S.M. Gagliano, J.P. Morgan, R.J. Shlemon, L.J. Rouse, I.L. van Heerden, and a few others. The Louisiana State Geological Survey, which funded and conducted the early research on the Mississippi River in the early 1930's, did not produce additional reports on the delta for many years. However, beginning in the mid-1980's several geologists associated with the Survey, such as S. Penland, J.R. Suter, R. Boyd, R.A McBride, R.S. Tye, and E.C. Kosters, conducted some very significant research on the Mississippi delta complex, especially on the very important processes of marine transgressions over the abandoned deltas. PART IV - STAGES IN THE DEVELOPMENT AND PARTIAL DESTRUCTION OF THE MISSISSIPPI RIVER DELTAIC PLAIN COMPLEX The following discussion of how the coastal marshes of southeast Louisiana were formed and partially destroyed is based on my research in this region over a 48-year period and an analysis of 51 significant papers written during 1930-88. I was indeed very fortunate to have been associated with this impressive research effort and believe that I am qualified to write a story about how my beloved native land came to be. Maringouin Delia As the ice on the continent began to melt about 15,000 years ago, sea level began to rise and much of what is now south Louisiana was inundated by the gulf waters as far north as the latitude of Baton Rouge. According to Frazier (1967) and Penland et al. (1987), there was a pause in the rise of sea level about 7,000 years ago. When sea level was about 6 m below its present level, the Mississippi River created a huge delta which extended as far south as Trinity, Tiger, and Ship Shoals in the gulf. This delta was referred to as the Maringouin Delta by Frazier (1967) and Penland et al. (1987) (Figure 5). The location of the upstream trunk channel of the Maringouin Mississippi River is now buried and unknown. A post Maringouin Delta sea level rise resulted in the transgression of gulf waters over this old delta. From about 5,500 to 3,500 years ago, the Mississippi River was flowing in the western part of the valley and it developed the Teche Delta over a portion of the Maringouin Delta (Figure 6). St Bernard Delta There was a major change in the course of the Mississippi River about 3,500 years ago and the Mississippi River built the St. Bernard Delta at New Orleans and east of New Orleans. As this new delta continued to grow eastward, the older abandoned Teche Delta far to the west gradually compacted and subsided and the gulf water encroached upon the Teche marshlands. Figure 7 shows the maximum development of the St. Bernard Delta and the transgression over the Teche Delta. Lafourche Delta About 2,500 years ago a portion of the Mississippi River waters was diverted southward at Donaldsonville and the river began to form the Lafourche Delta. As shown in Figure 8, the St. Bernard Delta was gradually abandoned and transgressed by the gulf, and the Lafourche Delta developed to its full extent. The Present Mississippi Delta As the Mississippi River established its present course and delta between the St. Bernard (Figure 5) and Lafourche Deltas, the Lafourche Delta was gradually abandoned (Figure 9). The older Teche, St. Bernard, and Lafourche Deltas were constructed within the broad, relatively shallow waters of the Continental Shelf. For the first time in its past 7,000-year history, the river is presently building its delta at the outer margin of the Continental Shelf and sediments are slumping into the deep waters of the gulf. Thus the seaward growth of the present delta has been extremely slow. The Atchafalaya River Deltas Within historic time, part of the Mississippi River waters began to flow southward into a new channel which developed at the junction of the Red River with the Mississippi, about 50 mi northwest of Baton Rouge. Since that time this new Atchafalaya River has captured more of the Mississippi waters each year. A report for the Mississippi River Commission by Fisk (1952) predicted that by about 1980 the Atchafalaya River would have captured all of the Mississippi waters. As a result of this report the U.S. Congress authorized the U.S. Corps of Engineers to construct the Old River Control Structure (ORCS) to prevent this river diversion. 10 11 12 13 a Q "2 E as ■o e es a © e a cs 3 "«> Q i> JS 't s ,3 -= 5 a .Sf 14 s a u 2 s I I — s a cs 3 a L. >■ a a •— B (A V K 3 J- 15 During its early stages of development, the Atchafalaya River began to construct a new delta in Grand Lake (the Atchafalaya Basin), north of Morgan City (Figure 9). By 1952, the Grand Lake region was nearly full of sediments and the lower Atchafalaya River south of Morgan City began to transport muds into Atchafalaya Bay. By 1972, the lower Atchafalaya River began to transport sand into the bay and a new subaerial delta was born. Several papers have been writ- ten on the Atchafalaya Deltas (Shlemon and Gagliano 1972; Shlemon 1975; Rouse et al. 1978; Gagliano et al. 1981; van Heerden 1983; Roberts 1986; and van Heerden and Roberts 1988). Maximum Development of Deltaic Plain Complex The total amount of new land formed by the Mississippi River during the past 7,000 years was about 14,000 mi2 (Figure 10). Stages in Development of the Deltaic Sequence of Sediments Each of the four large deltas which make up the Mississippi River Deltaic Plain complex is underlain by very characteristic vertical sequences of sediments. The stages in the construction of deltaic sequences were discussed by LeBlanc (1972) and are summarized by six diagrams shown on Figures 11A 11B, and 11C. Partial Destruction of the Deltaic Plain Complex Geologists have been aware for over 50 years that the loss of coastal deltaic marshes, and the transgression of the marine environments over these marshes, can occur as a result of channel diversion upstream of the delta. Russell and Russell (1939), LeBlanc (1972, 1977), and Morgan (1973) discussed the processes of delta shifts, loss of land, and marine transgressions. However, the detailed documentation of these processes and partial destruction of deltaic marshes did not occur until research geologists with the Louisiana Geological Survey, under the direction of State Geologist G.C. Groat, began a new phase of research on the delta complex. The best papers on this topic were published since 1985 by the following members of the Survey research staff: Shea Penland, J.R. Suter, Ron Boyd, and R.A McBride of the Louisiana Geological Survey. Penland et al. (1987) and Penland and Boyd (1985) described and illustrated three important stages in the transgressive depositional history of an abandoned Mississippi River Deltaic Plain complex (Figure 12). For additional information on the processes of loss of land, the reader should study these papers and also an earlier paper by J.P. Morgan (1973). Total Amount of Land Lost by Transgression Figure 13 shows that about 7,000 mi2 of coastal land have been lost by natural, transgressive marine processes during the past 7,000 years. SUMMARY Research on modern deltas and ancient delta deposits during the past 110 years has established the basic principles of deltaic sedimentation (LeBlanc 1975). The natural processes of upstream river diversions and the abandonment of deltas are now well documented and understood by geologists. It is also well documented that once a delta is abandoned, its sediments continue to compact and subside, under perfectly natural conditions, and this permits the marine environments to transgress over the abandoned delta marshes and a great loss of coastal land results. Forty-four of the 51 significant papers on the Mississippi River Deltaic Plain Complex cited herein were written by professors of geology at LSU and geologists who received their geological 16 17 3 to > 73 3 to C 4-1 O .: fl O ■a o t: 3 to >, 4-> fl tr >i -o c m fl c 0 M ja <— t a E ai p u to a 4-1 to 0 m 0) m ^H s o c Oi 0 3 -H c > M 4-) l-l -^H a> 0) fl M 73 > •H .c g 4-1 73 (-4 p i — i U C o fl 1> fl 4-1 m E 4-1 to O £ M 3 ■w i — i 4-1 O O B 01 <1) C V c 0> >1 ■a s c 1< ■-H u c fl fl c x: a 1 0 .c u fl 4-1 to to g a. 73 1/1 >! -H m p «— o M a to g fl -H m 4J 3 M c fl 4-1 it w a 0 u * o , ■H fl .Q -H 01 M ja 4-1 73 4> 4J 0) U O s to l: c 0 u z •H 4J 4-1 [/) a 73 3 to 0 to 01 >, 14-4 e u] C ja U O o O M 1-1 c 1 c 1> o •- -H o > fl fl to "3 -H ■H r— | >1 4J ^ t/1 M fl fl 4J 10 0 s fl 01 u a o u C e c >, Qi ■H •H c c 4-1 r o 4-1 -o fl 0) ^H u (U o> s: 01 •H a> :\, 73 to o .; to > it JS (1) CO i ■ 1 r: c o I) -H (ii ■H 4-> .*: 4J •H 4-1 -H (0 to o H 0 [I o u. 0) u 01 n 4-1 73 73 1-1 c 4-1 fl fl c ■? 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() a 4H c. m i — i o o TI in C x: -H ■J t) 4J tn 4J >1 (> •H 3 x: t. a •rH 4-> !) u (1) > -T1 1 3 1/1 in 01 'i n T) M U M R H M a 3 0) c ■ 0 Uh > M i "8 u 42 •■« Cfl s. u ■o "8 -5 a g 42 as 1 a eg •c e 1/3 3 s Oil J2 •c = I S t u ^ a — ■ a 2 tf s O GS a "8 ** V a J3 •o ** JJj <— o e !/> a in a 8 V >. a ■> 1 1 E o av yi a 1 — _■ • 0 ft A 3 t !A s T5 OJJ a u, 03 35 levels within the enclosed areas. The natural levee barriers restricted movement of ground water as well as surface runoff. Anaerobic conditions between the ridges were favorable for preservation of organic matter and formation of peat deposits. Peat and organic soils were able to accumulate vertically because of natural subsidence. Radiocarbon dates of buried peat deposits indicate that over the past 1,000 years this area has subsided approximately 0.18 cm (0.060 ft) per year (Gagliano et al. 1979). Auger borings taken by the authors demonstrate that peat accumulations in the area range up to 3 m in thickness. Geologists have long been interested in Mississippi Delta peat deposits because they provide modern analogs for ancient coal beds and because they are important in dating and unraveling the late Quaternary geological history of the deltaic plain. Following the 1958 lead of the master deltaic geologist, Harold N. Fisk, a number of important papers concerning the distribution and character of peats and other organic-rich wetland deposits have been published. Among the most relevant of these are papers by Frazier and Osanik (1969) and Coleman (1966). Building on these earlier studies, Kosters et al. (1987) concluded that "true peat and organic-rich beds in the Mississippi Delta are of freshwater forested swamp or herbaceous marsh (floating) origin. Saline marshes produce only organic-poor sediments." A considerable part of the total study area was occupied by trembling prairie or floating marshes in the 19th and early 20th centuries. In his study of the marshes of Louisiana, O'Neil (1949) indicated that there were approximately 101,000 ha of floating marshes, and classified a large part of the present study area as floating marsh. Floating marshes are made up of thick (up to 1 m) mats of cane-like root stalks and other plant materials that float. The mats support a diverse flora of emergent freshwater species dominated by Panicum hemitomon (paille fine or canouche). Two different explanations have been offered for the origin of the mats. Russell (1942) suggested that they formed by floating aquatic vegetation extending out into lakes from the shoreline. O'Neil (1949) noted that small mats may form in this way, but he thought that the extensive mats formed from marshes that were originally anchored into the underlying clay pan (mineral sediment substrate). He reasoned that as subsidence lowered the clay pan, the buoyant nature of the mats caused them to eventually break away and adjust to fluctuating water levels. Geological data favor O'Neil's hypothesis (see, for example, Fisk 1958; Frazier and Osanik 1969). The natural levee ridges and the mineral substrate between them formed large, shallow vessels that contained the peat and organic muck deposits. The soft, poorly consolidated, supersaturated organic deposits and soils were literally held in place by the natural levee ridge, analogous to a pie- shell configuration. The organic sediments made up the soft filling of the pie and the mineral deposits formed the shell which held them in place. Within this shell there was considerable variation in the consistency of organic soils, ranging from firm, woody, and grassy peats to organic ooze lying below floating marsh mats. The authors conclude that the skeletal framework and hydrologic effects of natural levee ridges and lake rims are essential components for the formation of peat and organic deposits and for maintaining the types of vegetation that sustain them. These ridges are essential to the formation of floating marshes. Some researchers consider tidal introduction of sediment to be necessary for marsh accretion to occur at a high enough rate to keep up with subsidence (Mendelssohn et al. 1983; Gosselink 36 1984). In the Bayou l'Ours area tidal introduction of sediment was prevented by the natural levee ridges, but the marsh thrived. Fresh marshes, even in locations that are remote from overbanlc flooding, are able to maintain themselves through accumulation of organic material and through development of floating mats. ABILITY OF THE LIVING SURFACE TO HEAL AND ENDURE Since its origin as a subdelta, and during the 250 years that it has remained in the abandoned stage, the Bayou l'Ours area has been periodically subjected to natural transgressive processes. The most active of these destructive processes are subsidence, hurricanes, and animal eat-outs. Subsidence rates during modern decades have increased dramatically. Dozier et al. (1983) indicated that subsidence rates for the Barataria Basin from 1945 to 1956 were 0.29 cm/yr. From 1956 to 1980 they had increased to 1.27 cm/yr. The 1956-80 rate is more than 7 times the long- term geological rate. Using 137C dating, DeLaune and Smith (1984) determined that the annual rate of peat accumulation in the Barataria Basin averaged 0.85 cm/yr for a freshwater site and 0.95 cm/yr for a brackish site. Their research indicates that peat accumulation at the locales studied has been able to keep pace with accelerated subsidence, which they estimated to be on the order of 0.6 to 1.0 cm/yr. The stabilizing effect of the natural levee ridges continues as long as they remain unbreached. In some places, ridges have subsided so that they are at or slightly below marsh level, but the firmer soils form a solid substrate. Marsh vegetation is tightly knit over the ridges and the marsh floor is firm. These ridges are often the sites of the most successful invasion by brackish and saline marsh vegetation species. During the late 19th and early 20th centuries, several ditches were dug through the marshes from Little Lake to trappers' settlements of the Bayou l'Ours ridges. These were initially hand- dug and only large enough for small skiffs and pirogues. They were too shallow to navigate during low water and were often clogged with vegetation. They were hydrologically inefficient and had little impact on the hydrology or the wetlands they traversed. This area has been in the path of severe hurricanes during historic times (1893, 1909, 1915, 1947, 1965, 1985, and others) and has been subjected to animal eat-outs from muskrat (Ondatra zibethicus rivalicius) and nutria (Myocastor coypus). As long as the skeletal system of natural levee ridges and firmer marshes of the lake rims remained intact, organic marsh soils stayed in place and the living wetland surface had a remarkable ability to mend itself, to build up and across disturbed areas, and to endure. POST-CANAL CONDITIONS Beginning in the 1940's, a system of dredged pipeline and drilling rig access canals was superimposed upon the Bayou l'Ours wetlands. These canals allowed rapid drainage of the impounded and semi-impounded hydrologic units. They created avenues of saltwater intrusion and tidal movement into the marshes that altered vegetation and scoured out poorly consolidated sediment. 37 One canal has been chosen to illustrate the processes (Figure 6). A major north-south cut through the ridge system was created by a pipeline canal dredged in 1956. The canal originated in Lake Enfermer, which was tidally interconnected to Caminada Bay. There were no weirs or dams placed across the canal to block the flow of water. The canal cut through three separate natural levee ridges and created an avenue of tidal movement into the naturally impounded fresh marshes lying between the ridges (Figure 7a). The 1987 photograph in Figure 7a shows the place where the pipeline canal cuts through the natural levee ridges of the West Fork of Bayou l'Ours. Note the three dead oak trees marking the crest of the natural levee ridge. The linear feature trailing off to the background is an old trappers' ditch dug in the 1920's. This ditch originally had a cross-sectional area of less than 1 m2. In contrast, the cross-sectional area of the canal, which was typical of a new canal network, was more than 100 times the cross-sectional area of the trappers' ditch. Unlike the shallow trappers' ditches, this deep canal completely altered the hydrologic regime of the area (Figure 7b). An aerial photo taken in 1945, before any of the canals were dredged, shows well-defined, natural levee ridges with relict channel remnants and largely unbroken marsh with a few small ponds (Figure 8a). This is, in part, a floating marsh and, in part, a marsh rooted in and anchored to the natural levee ridges. When mapped on a small scale map by O'Neil in the 1940's, this was classified as a brackish, three-cornered grass marsh. However, early aerial photographs from the 1940's and 1956 clearly indicate fresh-to-intermediate vegetation in the portions of these interdistributary basins and high concentrations of muskrats, as evidenced by their mounds. An aerial photo taken in 1959 shows the newly cut canal (Figure 8b). It was dug with a dragline and was originally 21 m wide and 24 cm deep. Spoil was placed in a staggered, discontinuous pattern along each side of the canal. Spoil mounds were approximately 150 m long. The canal formed a continuous connection with the upper reaches of Caminada Bay. The dark pattern on this photo is largely the result of a marsh burn. The marsh had been burned as a form of management to enhance the growth of three-corner grass, which is favored by muskrats. Aerial photographs show that by 1970 small marsh ponds had become interconnected and a tidal drainage network was developing (Figure 8c). The tidal network extended outward from the canal into the marshes. It was probably formed through enlargement of animal trails between the various ponds. Relict sections of the distributary channels had become exhumed and reactivated where they were crossed by the canal. They were also interconnected with the marsh ponds. This area was mapped as brackish marsh by Chabreck et al. in 1968. A photograph taken in 1982 shows that the tidal system had expanded and the marsh ponds had enlarged (Figure 8d). Not only had the vegetation died back, but active tidal scouring had occurred, removing the organic substrate. In their 1978 survey of the coastal marshes Chabreck and Linscombe (1978) mapped this area as salt marsh. Field inspection in 1987 indicated that the marsh was in very poor condition. It had a mottled appearance on current aerial photographs. There had been extensive die-back and the ponds had enlarged considerably. Even after marsh die-back, the organic substrate remains as mud flats until it is scoured by the tides. Water depths in the scour areas near the channel were found to be 1.5 m. Widespread scouring to a depth of about 1 m was found in most of the open water areas, and most of the peat and organic material had been removed. 38 ke Bayou '''' 'i 0 ' T 1 1 -I- mi km N ***** BRACKISH MARSH Figure 6. Post-canal hydrology of the Bayou 1'Ours ridge complex, circa 1987. 39 LJ 3 Figure 7a. Looking northeast across the pipeline canal where it cuts through the natural levee ridges of the West Fork of Bayou 1'Ours (1987): 1) pipeline canal; 2) natural levee ridge; 3) staggered spoil banks; 4) trappers' ditch. - 6 Figure 7b. Looking east across the pipeline canal along the Middle Fork of Bayou l'Ours: 1) relict distributary channel; 2) natural levee ridge; 3) pipeline canal; 4) spoil pile; 5) gap; 6) tidal scour pond; 7) drilling rig access canal. 40 -V- m 0. * •< a. 1945 b. 1959 ft - 1*^ L c. 1970 d. 1982 Figure 8. Sequential aerial photographs showing effects of pipeline canal on hydrologic subunit between the natural levee ridge of unnamed distributary of Bayou l'Ours (north) and Middle Fork of Bayou l'Ours (south). 41 When the natural levee ridges are breached by a deep canal, one of the most immediate effects is partial drainage and lowering of water levels in the impounded and semi-impounded hydrologic subunits between the ridges. The level of the floating marsh mat is actually lowered. A hummocky topography may result where clumps of firmer substrate hold the marsh at the higher level of the pre -canal, unbreached system. The canal provides an avenue through which bi-directional tidal movement occurs. The hydroperiod of the marsh is abruptly changed. It is subject to more frequent rises and falls. While mean monthly salinity values may not be greatly increased, higher highs and lower lows occur. These changes in hydrology and water chemistry stress the vegetation, resulting in marsh die-back. The inflow and outflow of the tide through gaps in the spoil bank has a pumping effect to which the organic sediment is highly susceptible. The most fluid and poorly consolidated material (usually under the floating marsh) is subject to early removal. Organic material exposed by marsh die-back is also vulnerable to erosion. As the tidal network evolves, other biological and chemical processes contribute to erosion of the organic sediments. As the ponds increase in size, wave action becomes a factor in the rates of further marsh loss. The rate of erosion is related to energy levels. The higher the velocities and the longer the duration of water movement, the greater the erosion. Thus, the greater the volume of water moving in and out of a tidally invaded hydrologic unit, the greater the amount of erosion and sediment transport. Once initiated, feedback causes the tidal erosion process within a hydrologic subunit to accelerate. Highest energy conditions occur during storms (winter storms and hurricanes) when water initially moves into the hydrologic subunits through canal breaches. Under severe weather conditions, water levels are elevated above the surface of the marsh and above the natural levee ridges. When these storm tides subside, the water ultimately drains through the gaps in the canal spoil banks and the canal channel through the natural levee ridges. Under natural conditions, most of the return is in the form of sheet flow, and velocities are reduced by vegetation. Under human-altered landscape conditions, erosion and development of the tidal channel network are accelerated during such high energy events. The erosive process is selective. Mineral sediment, whether directly exposed along the canal cut or exposed as redeposited spoil banks, is more resistant to erosion than the organic materials. Further, landforms and near-surface deposits that are composed predominantly of mineral sediment make up only 10% to 15% of the surface and near-surface features that are exposed to erosion. Thus, most of the sediment liberated by erosion is predominantly organic. Because the organic material is subject to breakdown by biological and chemical processes, the volume available for redeposition is very small. Localized redeposition of eroded organic material is evident in some instances where lake-rim features, spits, and canal plugs of reworked organic materials ("coffee grounds") have been observed. Figure 9 shows the evolution of the tidal network that originated in one hydrologic subunit from a gap in the spoil bank along the pipeline canal. This figure illustrates how the drainage network has expanded through time, removing the soft organic substrate by the tidal scouring process and destroying the marsh fabric. Comparative cross sections in Figure 10 illustrate some of the major effects of the pipeline canal on the marshes and organic sediments lying between the natural levee ridges. Note 42 a a a • — 1. a> 00 9 B "8 u 3 •c & VI u "3 s T3 ;►» «■• o «►« c> O 3 ** Si) 3 e (/5 2 •c s ■c 3 71 £ 3 3 1. O o 3 O 1/ >> *• 3 ■a OS <— E o ■«-< a a. J2 O 3 « O ■a U ■si ■o S s T3 ■c ** e s ■a e 3 e 3 c V /I J= 8 B £ £ Si 43 CROSS-SECTION, NEARSURFACE GEOLOGY, SEDIMENTS, AND HYDROLOGY ^ PBE-CAHAL GONDII Trappers Ditch 'i'iJIllfJJH' Trappers Ditch g \ ;;:•■' -Root Mat U mM\ / W ' ma ' '"■' "•' ' '^ ft o- •5 - •10 Isolated Pond Animal Runs ,fc,i!W — 6 — 3 •v:MS:;:i;v:;.^ ^g MARSH DEPOSIT k\^f»o| i.;^s5(peat & organic muck) Flit j^=" ■•.-.•• NATURAL LEVEE.'. •.•;••.• /.■:: W^-^^^^^Wm^llllllilllllllllll/lllli^h- //////// — 0 m _ -3 'CHANNEL FILL DEPOSITS I (clay, sand & silt) /////////////////// :/f3 POST-GANAl GONDII Tidal • /^ Scour ^^ Ponds Interconnected by Tidal Channels Marsh Mudflat Remnant Tidal Scour Channel .v.-MS&ft:]: :.:.-. NATURAL LEVEE f.v.v •;•'.• (silt & clay) ;•;•;•'.•'. CHANNEL •;'•'••' FILL ffl DEPOSITS 100 ft i i ■=. 25 m ■ ■ i i ■ i MARSH DEPOSIT (peat & organic muck) Wlllllll BAY OR LAKE FILL // (clay, sand & silt) ////////////////// VERTICAL EXAG. 5X OS Organic Sediment MS Mineral Sediment Figure 10. Diagrammatic cross sections illustrating pre-canal and post-canal conditions in a naturally impounded marsh. 44 particularly the difference in depth and cross-sectional area of natural ponds and trappers' ditches in the post-canal condition versus the size of the canals. The canals provide conduits for tidal action which suck the poorly consolidated organic sediments out of the protecting shells provided by the mineral sediment ridges. The geometry of the pipeline canals and associated spoil banks has also changed during the more than 30 years since its construction (Figure 11). Where the canal cuts through the natural levee ridges there has been little tendency to widen, but in the areas between the ridges the canal is now more than twice its original width. Spoil banks composed of mineral sediment remain elevated and vegetated with small trees and shrubs, while those composed of organic materials have diminished in width and elevation and support marsh vegetation. Under natural conditions tidal invasion of fresh marshes is slow, and mineral sediment accumulation along tidal channels and lake rims protects organic soils. Canals cause rapid invasion of tidal processes and massive marsh die-back followed by rapid tidal scouring of organic soils. The overall canal system superimposed on the Barataria Basin has created a sieve effect which has completely destroyed the natural hydrology of this basin. Today, the leading edge of marine tidal influence is now far into the upper end of this basin, in areas that were occupied by freshwater swamps 100 years ago. IMPLICATIONS FOR WETLAND MANAGEMENT A number of conclusions that have important implications for management can be derived from this study: 1. Peats and high organic soils form, and the vegetation communities which produce them persist, in fresh, nontidal, enclosed, and semi-enclosed hydrologic units with anaerobic conditions. 2. Under natural conditions in the deltaic plain, fresh and floating marshes are impounded and semi-impounded and are not subjected to tidal inflow and outflow, and ingress and egress of estuarine organisms. 3. Continuous spoil banks along tidally influenced canals protect adjacent high organic substrate marshes from saltwater intrusion and tidal scour. 4. When a tidal regime is abruptly imposed on a high organic substrate marsh (that formed as a freshwater swamp or marsh), the integrity of the marsh is destroyed and a high percentage of the total wetland area reverts to open water. 5. Some researchers advocate tidal inflow to maintain subdelta marshes. This position, derived largely from studies of Atlantic coast tidal marshes, fails to recognize the high susceptibility of peat and organic-rich marsh soils to the erosive forces of the marine tidal zone. When tidal fluctuations are allowed to persist, they may increase rather than decrease marsh deterioration and erosion. 6. In deltaic marshes located away from active distributary outlets, the primary source of sediment is that which is liberated by erosion. Since a high proportion of the near-surface deposits consist of peats and highly organic materials, erosion produces very little mineral material for accretion. 45 CROSS-SECTION, RELATIONSHIPS OF CANALS TO NEARSURFACE ALTERATIONS PIPELINE CANAL AT Til IF 10 _j 5- It 0 — -5 - •10 Marsh Grass 21 m \-ai;-;,'!m:3 Trappers Ditch Isolated Pond Animal Run \ \ ^5r~.^ (70|f0 /.^.^I'^^^fe. ^ Act - 6 - 3 MARSH DEPOSIT (peat & organic muck)I , wiiiiiiiiiiiiiiiiiiiiiiiiiiiiim. W.'L BAY OR LAKE FILL'' (clay, sand & silt) — o m 10. 5- ft 0- -5 -10 -I Marsh Grass / Spoil Deposits CANAL - PR IT C< T Trappers Ditch Isolated Pond MARSH DEPOSIT Upeat & organic muck) =^ AS~.4j^ milllllllllllllllMMM, 100 ft ■ ■ ■ ' i i - 25 m VERTICAL EXAG. 5X (?!«% . ?and 1 . silt) ////////////////// M,S, /// OS Organic Sediment MS Mineral Sediment - 6 - 3 - o m _-3 --6 Figure 11. Diagrammatic cross sections illustrating changes in pipeline canal and spoil banks during a 30-year period since construction. 46 The results of marine tidal invasion of marshes with high organic soil content are predictable. Early symptoms of the process are detectable. Remedial measures can be taken. 8. This study confirms the obvious-the larger the cross-sectional area of a canal, the greater the inflow and outflow of tidal water and the greater the potential for erosion. ACKNOWLEDGMENTS This paper has resulted from work done on behalf of private owners of wetlands in their efforts toward conservation management. LITERATURE CITED Chabreck, R.H., and G. Linscombe. 1978. Vegetative type map of the Louisiana coastal marshes. Louisiana Wildlife and Fisheries Commission, Baton Rouge, LA Chabreck, R.H., T. Joanen, and AW. Palmisano. 1968. Vegetative type map of the Louisiana coastal marshes. Louisiana Wildlife and Fisheries Commission, New Orleans, LA Coleman, J.M. 1966. Recent coastal sedimentation; central Louisiana coast. Coastal Studies Series No. 17, Louisiana State University Press, Baton Rouge. 73 pp. DeLaune, R.D., and C.J. Smith. 1984. The carbon cycle and the rate of vertical accumulation of peat in the Mississippi River Deltaic Plain. Southeast. Geol. 25(2):61-69. Dozier, M.D., J.G. Gosselink, C.E. Sasser, and J.M. Hill. 1983. Wetland change in southwestern Barataria Basin, Louisiana, 1945-1980. LSU-C9L-83-11. Coastal Ecology Laboratory, Center for Wetland Resources, Louisiana State University, Baton Rouge, LA. 102 pp. Fisk, H.N. 1958. Recent Mississippi River sedimentation and peat accumulation. In Ernest Van Aelst, ed. Congres pour l'Avancement des Etudes de Stratighique et de Geologie du Carbonifere, 4th Heerlen 1958, Compte Rendu 1:87-199. Frazier, D.E., and A Osanik. 1969. Recent peat deposits, Louisiana coastal plain. Pages 63-85 in E.C. Dapples and M.E. Hopkins, eds. Environments of coal deposition. Geol. Soc. Am. Spec. Pap. No. 114. Gagliano, S.M., R.A Weinstein, E.K. Burden, K.L. Brooks, and W.P. Glander. 1979. Cultural resources survey of the Barataria, Segnette, and Rigaud Waterways, Jefferson Parish, Louisiana. Prepared for New Orleans District, U.S. Army Corps of Engineers, Contract No. DACW 29- 77-D0272, Coastal Environments, Inc., Baton Rouge, LA 2 vols. Gosselink, J.G. 1984. The ecology of delta marshes of coastal Louisiana: a community profile. U.S. Fish Wildl. Serv. FWS/OBS-84/09. 134 pp. Kosters, E.C., G.L. Chmura, and A Bailey. 1987. Sedimentary and botanical factors influencing peat accumulation in the Mississippi Delta. J. Geol. Soc. (Lond.) 144:423-434. Mendelssohn, E.A, R.E. Turner, and K.L. Mckee. 1983. Louisiana's eroding coastal zone: management alternatives. J. Limnol. Soc. South Afr. 9(2):63-75. Moore, EG., ed. n.d. General instructions to U.S. Deputy Surveyors. Department of Natural Resources, State Land Office, Baton Rouge, LA 48 pp. O'Neil, T. 1949. The muskrat in the Louisiana coastal marsh. Louisiana Wildlife and Fisheries Commission, New Orleans, LA 152 pp.+ maps. 47 Russell, R.J. 1942. Flotant. Geogr. Rev. 32:74-98. Turner, R.E. 1987. Relationship between canal and levee density and coastal land loss in Louisiana. U.S. Fish Wildl. Serv. Biol. Rep. 85(14). 58 pp. Weinstein, R.A., and S.M. Gagliano. 1985. The shifting deltaic coast of the Lafourche country and its prehistoric settlement. Pages 122-149 in P.D. Uzee, ed. The Lafourche country: the people and the land. Center for Louisiana Studies, University of Southwestern Louisiana, Lafayette, LA. 48 ACCRETING MUDFLATS AT THE MISSISSIPPI RIVER DELTA: SEDIMENTATION RATES AND VASCULAR PLANT SUCCESSION David A. White Loyola University New Orleans, LA 70118 ABSTRACT Geologically, the Mississippi River Delta is an extremely dynamic environment. Its interior marshlands have subsided to form huge (1,000's ha), shallow (<1 m) ponds, where once (1940's- 1950's) vast freshwater marshes existed. The creation of crevasses in the levees which border these ponds has allowed river water to flow into the ponds and consequently sediment deposition has formed large "inner delta splays." I have been monitoring the rate of sedimentation and the vascular plant succession on the developing mudflats at three sites for 4 years. Sedimentation rates across the sites averaged 0.0189 cm/d or 6.9 cm/yr for 3 years. Vascular plant colonization and succession were rapid; by the third year total live standing crop averaged 1,194 g/m2. A total of 62 vascular plant species have been collected at the sites. Scirpus deltarum (three-square grass) became the dominant herb the second or third year on the lower regions of the mudflats. This species is particularly significant for its value as a wildlife food. Salix nigra (black willow) was prevalent on the highest flats. Several species of sedges and grasses made up the majority of the remaining plant biomass. The amount of belowground organic material (live and dead) increased to 1,212 g/m2 by the third year. Herbivory by large mammals did affect succession. INTRODUCTION The coastal marshes of Louisiana are one of the most productive habitats in North America. Here the production of fish and wildlife is directly related to the abundance and diversity of photosynthetic plants (Chabreck 1982). Louisiana's wetlands are winter habitat for the largest percentage of the North American duck and goose populations. The wetlands also produce the largest fur harvest in North America, principally muskrat and nutria. The continued high production of these primary consumers requires freshwater marshes since only in these marshes are their food plants abundant. Unfortunately the entire State of Louisiana is losing freshwater marshes from land loss and saltwater intrusion (Fruge 1982; Baumann and DeLaune 1982) at an alarming rate (Craig et al. 1979; Wicker 1980). The management of the remaining marshes for wildlife is of paramount importance (Weller 1978). The present Mississippi River Delta encompasses over 1,400 km2 and is a composite of numerous lobes formed during the past 1,000 years (Figure 1). The delta's biotic character exists because of sheet flow of freshwater towards the saline Gulf of Mexico waters, creating a horizontal stratification of salinity. Plant species distributions (marsh types) at the delta must be governed by water depth and salinity as Penfound and Hathaway (1938), Chabreck (1972), and Weiss et aL (1979) found in other Louisiana marshes. Therefore, the central portion of the delta supports tremendous areas of freshwater marshes, while the peripheral portions support saline marshes. The freshwater marshes of the Mississippi River Delta are not unique in that they, too, have been disappearing at a rapid rate. Due to human-induced factors, between 1956 and 1978 nearly 400 km2 of wetlands have been lost here (U.S. Fish and Wildlife Service 1982). Levees have 49 t N 4 8 12 16 _i i i I KILOMETER PASS A LOUTRE SOUTH PASS SOUTHWEST PASS Figure 1. Study area within the Mississippi River Delta. Star marks the area of the large, shallow, freshwater pond just south of Octave Pass in which the splays are developing. 50 prohibited sedimentation within the central delta, forcing silt-laden waters to the Outer Continental Shelf. Thus, subsidence within the central delta has not been counterbalanced by sedimentation, so large shallow freshwater bays have been created. In addition, channelization and canal dredging have diverted the sheet flow from the freshwater areas and allowed saltwater intrusion from the Gulf of Mexico, accelerating the decline in the freshwater marshes. Aerial photographs of the central delta taken during the past 10 years show that downstream from levee breaches there has been rapid land buildup in limited areas within several of the large freshwater ponds and bays. Rapidly these inner delta splays become colonized by various local freshwater plants, some of which are highly desirable wildlife food. The Fish and Wildlife Service, which manages most of the northeastern delta, has seen dramatic use of these splays by wildlife. So, during October 1983 a levee crevasse was made along Octave Pass to further induce land buildup within a huge freshwater pond that had formed from subsidence since 1956. This study monitored plant colonization and succession on the inner delta splay that formed as a result of the levee breach. Also, this study measured the rate of sedimentation on this artificial splay. For comparison, this study also monitored the sedimentation rate, plant colonization, and succession on a nearby splay near Brant Pass that formed naturally in 1978 from another levee breach. METHODS AND MATERIALS Plant colonization, succession, and sedimentation on these two inner delta splays were monitored for a period of 3 years. Both splays are located within the Delta National Wildlife Refuge, which occupies most of the northeastern quadrant of the Mississippi River Delta. Both splays receive water in sheet flow from Octave Pass and are located within 4 km of the river. Three study sites were established at the very down flow end of one finger or lobe of the splays. In the summer of 1984, one site was located on the Octave Pass splay and another on the south end of the Brant Pass splay. Because of their age differences, the Brant Pass splay is many times larger than the Octave Pass splay, so a third site was chosen on the Brant Pass splay in spring 1985, approximately 2.5 km north of the first site. At each of the three sites, sedimentation rates were quantified by using the procedures of Baumann (1980). Beginning in the fall of 1984 and periodically thereafter, white silica marker horizons were placed in transects parallel and perpendicular to the developing mudflat to mark mudflat levels. Cores through the horizons months and years later gave estimates of the amounts of sedimentation. To study plant colonization and succession, vegetation was sampled by using 0.25-m2 plots, placed along transects perpendicular to the long axis of the mudflat. The vegetation in each plot was sorted by species, oven-dried, and weighed to determine biomass. In addition, an estimate of belowground growth and organic matter accumulation was determined by collecting the sediment within 0.25-m? plots well below rhizome growth; washing the mud away; and drying and weighing the remaining live and dead organic material. No attempt was made to separate roots and rhizomes from dead material, or to separate species. With each new growing season additional transects of five 0.25-m2 plots were established at the leading edge of mudflat development. Each August from 1984 to 1987 the plots along the new 51 and old transects were sampled so that in August 1987 a total of forty 0.25-m2 plots had accumulated and were clipped of vegetation. Throughout the study, the sites were surveyed for any new plant colonizers. Voucher collections were made and deposited in the Herbarium of Tulane University, New Orleans, LA. RESULTS At the start of this study (1984) the sites had an exposed (at mean sea level) mudflat area of approximately 5,000 m2. By the summer of 1985, about 30,000 m2 of new land had accreted and had been vegetated. Currently (spring, 1988) over 60,000 m2 of land has developed and has been colonized by vascular plants. Sedimentation rates vary tremendously and are dependent upon annual flood and sediment load cycles. Rates per site varied from 8.4 cm/4 mo to as little as 0.2 cm/5 mo. The average rate was 0.0189 cm/d for 3 years or 6.9 cm/yr. Typically the most rapid sedimentation occurs seasonally during spring floods. When flood waters recede (April-May) large newly developing mudflats are left exposed, particularly during low tides. A total of 62 plant species from 21 families have been collected and identified from the accreting flats (Table 1). The graminoids (grasses and sedges) comprise the largest number of species (21), of which Scirpus deltarum (delta three-square grass) is the most common. The only woody species is Salix nigra (black willow). Primary plant colonization is very rapid on the exposed mudflats. By the end of £he first summer, 133 g/m2 of aboveground plant biomass were present. Two species predominated: Sphenoclea zeylanica on the lower flats and Salix nigra (14 g/m2) on the highest flats. Two graminoids were common; usually they occurred along with several other species: Eclipta alba, Lindemia dubia, Ammania coccinea, and Cyperus difformis. By the end of the second summer (12 months after colonization) 553 g/m2 of plant biomass were present. At this time Scirpus deltarum had colonized the mudflats with an average biomass of 55 g/m2. Scirpus deltarum, along with several other sedges (Cyperus erythrorhizos, Cyperus Table 1. Plant species (by family) collected at three sites on developing splays within the Delta National Wildlife Refuge. ALISMATACEAE Alisma subcordatum Raf. Sagittaria platyphilla Engelm. Sagittaria graminea Michx. Sagittaria latifolia Willd. AMARANTHACEAE Acnida cuspidata Sprengl. Amaranthus tamariscina Nutt. ARACEAE Colocasia esculenta (L.) Schott CAMPANULACEAE Sphenoclea zeylanica Gaertn. (Continued) 52 Table 1. (Concluded). COMPOSITAE Bidens laevis (L.) BSP Eclipta alba (L.) Hassk. Helenium quadridentatum Labill. Mikania scandens (L.) Willd. Pluchea odorata (L.) Cass Spilanthes americana (Mutis) Hieron. CASSULACEAE Penthorum sedoides L. CRUCIFERAE Rorippa sessiliflora (Nutt.) Hitchc. CYPERACEAE Cyperus aristatus L. Cyperus difformis L. Cyperus erythrorhizos Muhl. Cyperus strigosus Rottb. Cyperus surinamensis Rottb. Eleocharis obtusa (Willd.) Schultes Fimbristylis vahlii (Lam.) Linh. Scirpus americanus Persoon Scirpus deltarum Schuylar Scirpus validus Vahl. LEGUMINOSAE Daubentonia drummondii Rydb. Vigna luteola (Jacq.) Benth. LYTHRACEAE Ammania coccinea Rottb. Lythrum lanceolatum Ell. ONAGRACEAE Ludwigia decurrens Walt. Ludwigia leptocarpa (Nutt.) Hara Ludwigia octovalvis (Jacq.) Rava Ludwigia peploides (HBK) Raven POLYGONACEAE Polygonum densiflorum Meisn. Polygonum pensylvanicum L. PONTEDERIACEAE Heteranthera dubia (Jacq.) Macm. Heteranthera reniformis Ruiz & Paven PRIMULACEAE Samolus parviflorus Raf. RANUNCULACEAE Ranunculus scelerotus L. GRAMINAE Echinochloa crusgalli (L.) Beauv. Echinochloa walteri (Purch.) Heller Eragrostis glomerata (Walt.) Dewey Eragrostis hypnoides (Lam.) BSP Leersia oryzoides (L.) Swartz Leptochloa panicoides (Presl.) Hitchc. Panicum capillare L. Panicum dichotomiflorum Michx. Paspalum fluitans (Ell.) Kunth Phragmites australis (Cav.) Trin. ex Steud. HYDROPHYLLACEAE Hydrolea uniflora Raf. JUNCACEAE Juncus difussisimus Buchl. SALICACEAE Salve nigra Marshall SCROPHULARIACEAE Bacopa rotundifolia (Michx.) Wettst. Leucospora multifida (Michx.) Nutt. Lindemia anagallidea (Michx.) Penn. Lindemia dubia L. Mimulus alatus Aiton Mimulus ringens L. TYPHACEAE Typha domingensis Pers. UMBELLIFERAE Hydrocotyle verticillata Thumb. Ptilimnium capillaceum (Michx.) Raf. 53 strigosus, Cyperus difformis, Cyperus aristatus, and occasionally Cyperus surinamensis; total biomass equals 157 g/m2), dominated the mudflat. The black willow (Salix nigra) had grown to 87 g/m2 by the second summer's end. Twenty-four months after colonization or by the end of the third summer Scirpus deltarum increased tremendously in importance to 483 g/m2, comprising nearly 50% of the 1,098 g/m2 total aboveground biomass. Also, the formerly abundant Cyperus species declined considerably and were replaced by the numerous grasses listed in Table 1, of which Panicum dichotomiflorum, Leptochloa panicoides, and Echinochloa walteri are the most abundant. Salix nigra continued to increase in biomass to 167 g/m2. At the head (upstream end) of the developing mudflats (islands), Salix nigra dominated from the start. However, browsing of the willow by nutria and deer can greatly retard the willow's potential for long-term local dominance. Some areas were heavily browsed to the virtual elimination of willow, and various herbs became established in the years after initial colonization. After several years, within these heavily browsed regions of the splays, the assortment of herbs was less diverse and eventually the browsed areas became dominated by Scirpus deltarum. By the end of the fourth summer, the direction of secondary plant succession was clearly toward two perennials: Scirpus deltarum on the lower and heavily browsed higher flats and Salix nigra on the less browsed higher flats (Figure 2). By this time the total aboveground biomass was 1,194 g/m2 of which 600 g/m was Scirpus deltarum and 222 g/m2 was Salix nigra. Other sedges, grasses, and herbs had a combined total of only 257 g/m2. Monotypic stands of Colocasia esculenta (elephant ear) were found on portions of the Octave Pass and Brant Pass splays where very fine silt had been deposited. Usually these stands were adjacent to and down flow from stands of Salix nigra (Figure 2). Throughout this successional process, the total amount of belowground organic material increased to 1,212 g/m2 by 36 months after colonization. Most of this material was living roots and rhizomes of Salix nigra and Scirpus deltarum. DISCUSSION If one takes into account that this study was restricted to splays, well removed from uplands and dredged spoil, the plant species on the developing mudflats within the Mississippi River Delta are not significantly different from those described by Montz (1978) for the Atchafalaya Delta or from Howard and Penfound's (1942) description of areas of sedimentation from crevasse formation in the Bonnet Carre floodway on the Mississippi River above New Orleans. Of the 62 species of vascular plants identified from the three sites, only 14 incidentals were not listed by Montz (1978). Quantitatively, however, the composition of the vegetation on the developing splays at the Mississippi River Delta is quite different from similar areas in the Atchafalaya River Delta. According to Johnson et al. (1985), the developing islands there are dominated by Salix nigra at their heads, and vast areas of Sagittaria latifolia make up the majority of the remaining vegetation. Between these two community types exists a relatively small area of a Typha latifolia community and pockets of a "seasonal" community of several species, including Cyperus difformis, Eleocharis parvula, Ammania coccinea, and Sphenoclea zeylanica. 54 CO >- q: QL LU < M Q Z z > O 0 QL (J _l < LU 0 21 CO 0 OL 00 Q. U. Q.J5 55 Surprisingly, Scirpus deltarum or any other Scirpus species is not found in any abundance in the Atchafalaya Delta. It may be that the fine sediment composition favors the colonization of Sagittaria latifolia in the Atchafalaya Delta. The sediments are much coarser in the Mississippi River Delta. This study has shown the abundance of Scirpus deltarum on the splays at the River Delta 2 and 3 years after mudflat emergence, which is of considerable importance to wildlife. During the first two winters, the majority of the 80,000 plus geese that overwintered in the delta fed on this sedge, particularly at the Brant Pass splay. During the plant growing season (May-October), the aboveground stems of Scirpus deltarum are a major food of nutria and muskrat. Many of the seeds from the other sedges and grasses are important in the diets of the overwintering ducks. Salix nigra is the only significant plant with aboveground living tissue during the winter. As a result, its presence sustains the local deer population and provides food to the nutria and muskrat during winter. CONCLUSIONS 1. Within the Mississippi River Delta more than 60,000 m2 of new land development was monitored at three sites on two splays located within a huge, shallow, freshwater pond. This represents only a small fraction of total land buildup on these splays and within the delta itself. 2. The average rate of sedimentation at the three sites for 3 years was 0.0189 cm/d or 6.9 cm/yr. The month-by-month rate fluctuates considerably depending upon the river's sediment load and volume of flow. 3. Qualitatively, the three sites supported a diverse flora typical of freshwater alluvial deposits within southeastern Louisiana. Sixty-two plant species from 21 families have been identified. 4. Quantitatively, the three sites supported a much less diverse flora. Salix nigra, Scirpus deltarum, and Colocasia esculenta are quite common in their own microhabitats, and often comprise more than 80% of a community's plant biomass. 5. Successionally, Salix nigra on the highest land and Scirpus deltarum on the lower land dominate most of the mudflats' surface area 2-3 years after initial colonization. First- and second-year colonizers include an assemblage of herbs, particularly grasses and sedges. ACKNOWLEDGMENTS I thank personnel of the Fish and Wildlife Service for allowing me free access and water transportation to the study sites. I thank Dr. Steven Darwin for his patient taxonomic labors. To the many biology students at Loyola University who were laboratory and field assistants, I extend special thanks. This research was supported by the Louisiana Sea Grant College Program, a part of the National Sea Grant College Program maintained by the National Oceanic and Atmospheric Administration, U.S. Department of Commerce. 56 LITERATURE CITED Baumann, R.H. 1980. Mechanisms of maintaining marsh elevation in a subsiding environment M.S. Thesis. Louisiana State University, Baton Rouge. 91 pp. Baumann, R.H., and R.D. DeLaune. 1982. Sedimentation and apparent sea-level rise as factors affecting land loss in coastal Louisiana. Pages 2-13 in D.F. Boesch, ed. Proceedings of the conference on coastal erosion and wetland modification in Louisiana: causes, consequences, and options. U.S. Fish Wildl. Serv. Biol. Serv. Program FWS/OBS-82/59. Chabreck, R.H. 1972. Vegetation, water, and soil characteristics of the Louisiana coastal region. La. State Univ. Agric. Mech. College Bull. No. 664. 72 pp. Chabreck, R.H. 1982. The effect of coastal alterations on marsh plants. Pages 92-98 in D.F. Boesch, ed. Proceedings of the conference on coastal erosion and wetland modification in Louisiana: causes, consequences, and options. U.S. Fish Wildl. Serv. Biol. Serv. Program FWS/OBS-82/59. Craig, N.J., R.E. Turner, and J.W. Day, Jr. 1979. Land loss in coastal Louisiana. Pages 227-254 in J.W. Day, Jr., D.D. Culley, Jr., R.E. Turner, and A.J. Mumphrey, Jr., eds. Proceedings of the third coastal marsh and estuary management symposium. Louisiana State University Division of Continuing Education, Baton Rouge. Fruge, D.W. 1982. Effects of wetland deterioration on the fish and wildlife resources of coastal Louisiana. Pages 99-107 in D.F. Boesch, ed. Proceedings of the conference on coastal erosion and wetland modification in Louisiana: causes, consequences, and options. U.S. Fish Wildl. Serv. Biol. Serv. Program FWS/OBS-82/59. Howard, J. A., and W.T. Penfound. 1942. Vegetational studies in areas of sedimentation in the Bonnet Carre floodway. Bull. Torrey Bot. Club 69:281-289. Johnson, W.B., C.E. Sasser, and J.G. Gosselink. 1985. Succession of vegetation in an evolving river delta, Atchafalaya Bay, Louisiana. J. Ecol. 73:973-986. Montz, G.N. 1978. Vegetational characteristics of the Atchafalaya River Delta. Bull. La. Acad. Sci. 41:71-84. U.S. Fish and Wildlife Service. 1982. Louisiana coastal wetlands: a vanishing landscape. Map. U.S. Fish and Wildlife Service, Slidell, LA Penfound, W.T., and E.S. Hathaway. 1938. Plant communities in the marshlands of southeastern Louisiana. Ecol. Monogr. 8:1-56. Weiss, E.T., D.A. White, and L.B. Thien. 1979. Seasonal dynamics of salt marsh plant associations in Louisiana. Contrib. Mar. Sci. 22:41-52. Weller, M.W. 1978. Management of freshwater marshes for wildlife. Pages 267-284 jn R.E. Good, D.F. Whigham, and R.L. Simpson, eds. Freshwater wetlands: ecological processes and management potential. Academic Press, New York. 378 pp. Wicker, K.M. 1980. Mississippi deltaic plain region ecological characterizations: a habitat mapping study. A user's guide to the habitat maps. U.S. Fish Wildl. Serv. Biol. Serv. Program FWS/OBS-79/07. 57 SOILS OF LOUISIANA'S COASTAL MARSH Kenneth Murphy U.S. Department of Agriculture Soil Conservation Service Crowley, LA 70526 ABSTRACT The vast and unique coastal area of Louisiana was formed through thousands of years of geological change which included sea-level changes, subsidence, and sediment deposition. The 1.3 million ha area of coastal marsh is a very delicate ecosystem composed of two slightly different areas: the Deltaic marsh of southeast Louisiana and the Chenier marsh located along the southwest coastline of the State. All of Louisiana's coastal marsh soils have the common characteristics of wetness, flooding, low elevation, and low relief. They vary widely in many other characteristics, however, that are important to their use and management. Unfortunately, these characteristics are not evident from surface features or vegetation and require soil borings and examination to determine their nature. Soil surveys made by the Soil Conservation Service, U.S. Department of Agriculture, in cooperation with the Louisiana Agricultural Experiment Station are based upon subsurface examinations and can provide much vital information for land-use decisions on these fragile soils in the coastal marsh. INTRODUCTION The Louisiana Coastal Region encompasses an area of nearly 3.2 million ha. About one-half of this is water, one-third is natural marsh, and the remainder is beaches, cheniers, spoil deposits, and artificially drained marshes. Some 40% of the coastal marshes in the continental United States are located along Louisiana's Gulf of Mexico coastline. The coastal region has been divided into two segments on the basis of origin and physiography. The area east of Vermilion Bay and occupying two-thirds of the coastal region has been designated as the Deltaic Plain. The Deltaic Plain is the site of the various delta systems. The area west of Vermilion Bay has been named the Chenier Plain and was formed from river sediment swept westward by long shore currents in the Gulf of Mexico (Coleman 1966). The coastal marshes are a product of the Mississippi River. During the Recent Epoch, seven Mississippi River Delta systems have developed because of diversions in the river channel. The large number of deltas has caused considerable variation in the physiography of the area. During coastal development, prairie formation deposits of Pleistocene age were overlain with a wedge of recent sediment primarily from the Mississippi River (Kniffen 1968). The developmental process of the Chenier Plain was considerably different from that of the Deltaic Plain. Silt and clay sediment from the Mississippi River was carried westward by currents in the Gulf of Mexico and gradually accumulated as mud flats against the shoreline. The amount of material carried and the duration of flow determined the extent of the buildup. The mud flats soon became occupied by salt-tolerant vegetation and new marsh was thus created (Coleman 1966). 58 The building process in the Chenier Plain continued until a change in the river's course resulted in a loss of sedimentary material. Once the building process ceased, the new marsh came under attack by wave action. Shoreline retreat then followed, with a corresponding formation of local beach deposits. The beach deposits remained along the point of wave attack until another change in the river's course caused a resumption in the buildup along the shoreline. This process caused marshes to again advance seaward, leaving the beaches stranded (Russell and Howe 1935). The stranded beaches (cheniers) extend in an east-west direction and have a strategic role in the drainage patterns of the Chenier Plain. In contrast, topographic features of the Deltaic Plain, such as the natural levees of past and present drainage systems, generally run in a north- south direction. The areas of marsh in Louisiana have water tables at or near the soil surface most of the time. Many of the soils are subject to occasional or frequent inundation by tidal action. Until recently, coastal lands were included on soil maps as miscellaneous land types, such as tidal marsh, tidal flats, or included in broadly defined soil series. However, recent interests in wildlife, marine biology, land loss, recreation, and urban development have promoted a more detailed inspection of the coastal region and more detailed mapping. METHODS AND PROCEDURES The primary objective of the National Cooperative Soil Survey (NCSS) program in the State of Louisiana is to obtain through soil surveys an inventory of the State's soil resources, record the location of soils, predict soil performance under defined use and management, facilitate the transfer of soil information from one location to another, and contribute to the knowledge, understanding, and proper use of our land resources. This is a cooperative effort of the Soil Conservation Service, the Louisiana Agricultural Experiment Station, and the Louisiana State Soil and Water Conservation Committee. Soil surveys of coastal areas in Louisiana are designed to meet specified objectives. In most survey areas it is not difficult to identify the potential users of the survey. The refinement in map units, purity of delineations, and map scale are then formulated to meet the needs of the users. When the field work is complete, a soil report is published for the survey area. This report contains soil maps showing the geographic distribution of soils and a text that describes, classifies, and interprets the soils. Soil maps are prepared on aerial photographs. A soil map consists of soil lines and soil map unit symbols that delineate and identify areas of the soils. Cultural features are also shown. In Louisiana, soil maps have a scale of 1:20,000. Generally, the information provided in a soil report is considered to be adequate for most users' needs for a period of about 20-25 years. However, where there are dramatic changes in land use, land composition, or in the needs of users, the information may need to be updated much sooner. As of June 1988, field mapping has been completed in 13 of 15 coastal parishes in the State (U.S. Department of Agriculture, unpubl.). About one-half of the completed survey areas are published (U.S. Department of Agriculture 1973, 1977, 1983, 1984). Field work is scheduled to commence in St. Mary and Terrebonne Parishes in early 1991. Access to the marshes is difficult, even by boat. Most of the surveys of marsh lands have utilized helicopters for transportation. The aircraft provided by contract with a privately owned 59 helicopter service was a Bell Model 406-B Jet Ranger equipped with pontoons. Polyvinylchloride tubes were provided on the pontoons to contain the soil augers in flight. The field work was accomplished by two teams. Each team consisted of a soil scientist and a biologist The teams were leap-frogged along transects to the sites, with one team traveling while the other team was sampling. Examinations and sampling sites were predetermined and plotted on the maps. Sites were aligned into transects which were perpendicular to expected soil and vegetation changes. The sites were spaced roughly one per 2.6 km2 on continuous land areas. Many islands were examined less intensely and a few small islands were not examined. Site numbers were placed on the base maps and on note sheets. Examination was to a depth of 2 m. Soil properties were recorded and a profile description was made that documented all data needed for classification and correlation of the soil. The plant community was analyzed and each plant species was listed and percent composition was estimated. Other data recorded at each site included percentage of open water within a specified diameter of the site, water depth and flooding characteristics, water salinity, and wildlife activity. Soil boundaries were located on the basis of field observations, photo interpretation, and transect data. These boundaries were delineated on aerial photographs at a scale of 1:20,000. Telescoping Belgian mud augers and McCauley augers were used to examine organic soils and clayey soils. Bucket augers were used to examine soils in areas dominated by loamy material. A "split-tube" sampling device proved to be the most useful tool for collecting samples for detailed descriptions and laboratory studies from below the water table. The tube was driven to the desired depth and removed with considerable effort assisted by additions of compressed air placed at the tip of the tube. Samples of wet soils required special handling and were refrigerated to below biological zero (5 °C) for storage. DISCUSSION Physical and Chemical Properties Water content under field conditions is an important attribute of wetland soils. Even when soils are continuously saturated, the water content may differ markedly in relation to soil properties or qualities. The percentage of mineral or organic content, the percentage of fiber, and whether or not the soil material has ever become air dry since deposition seem to be the most important factors. As fiber content increases, the water content increases. As mineral content increases, the water content decreases. Studies have shown that soil samples with 25% mineral (75% organic matter on a dry weight basis) contained 625%-l,700% water relative to soil. Soil samples with 75% mineral (25% organic matter on a dry weight basis) contained 80%-250% water. The water content is proportional at intermediate levels of mineral content. Water content of the mineral layers of a Larose soil (Typic Hydraquent) are typically 80%- 225% while by comparison an upland soil such as Sharkey (Vertic Haplaquept) has water content of about 50%. Sharkey soils are below field capacity at some time during most years, have a firm consistency when moist, and are plastic when wet. The higher water content of the Larose soil is attributed to deposition of the soil material under water and the assumption that it has never dried below field capacity at any time during its history. Mineral soils with water content above 100% undergo significant loss of volume when drained. Permanent open cracks form and extend 60 for considerable depth into the subsoil. Once dried and rewet, they never regain the high water content of undried samples. An organic soil such as Kenner (Fluventic Medisaprist) has water content in the organic layers of about 590%-l,000%. Water content of 113% and 226% was measured in two thin mineral layers that were present in the Kenner soil profile. The Lafitte soil (Typic Medisaprist) is also organic and has a water content of about 763%-l,240%. When the organic soils are drained, they shrink and large volume changes result (U.S. Department of Agriculture 1977, 1983, 1984, unpubl.). In general the organic soil material contains 2 to 8 times more water in the field state than mineral soils. Mineral soils of clay texture that have never dried hold up to twice as much water as clays that have undergone cycles of wetting and drying. Mineral content is defined as the percentage of ash remaining after ignition of an oven-dried sample. The mineral content includes both mineral particles and ash residue from the organic component. The material lost on ignition is considered as organic matter. The amount of ash from the organic component contributes very little to the total mineral content. Mineral content is the distinguishing characteristic between mineral and organic soil materials. Organic soil material contains more than 18% organic carbon (dry weight basis) if the mineral fraction is more than 50% clay. If the mineral fraction has no clay, a soil with more than 12% organic carbon may be classified as organic (Figure 1). In Louisiana, 18% organic carbon is necessary to classify the soil material as organic since the mineral component is considered to be more than 50% clay. The mineral content in the organic layers of Lafitte and Kenner soils ranges from 21% to 50%. Mineral layers of the Larose and Sharkey soils range from 75% to 98% mineral (U.S. Department of Agriculture 1984, unpubl.). Fiber content is used in classification of organic soils. A fiber is a piece of plant tissue large enough to be retained on a sieve having 0.15-mm openings. The degree of decomposition of organic material is related to content of fibers. If highly decomposed, fibers are nearly absent. If only slightly decomposed, most of the volume normally consists of fibers. If the organic materials are moderately decomposed, the fibers may be largely preserved, but are easily broken down by disturbance. For this reason, the percentage of fibers that do not break down with rubbing gives the most realistic field estimate of the degree of decomposition. Unrubbed-fiber percentage is determined on undisturbed samples. As the percentage of fiber increases, there is only a slight decrease in bulk density of the soils sampled in Louisiana. Except for the surface mat of live roots, most of the organic soil materials have rubbed-fiber contents of less than 15% indicating a high degree of decomposition. Bulk density is the mass of soil, exclusive of the liquid phase, per unit volume. It is calculated by the general formula Db = weight of soil (exclusive of water) divided by volume of soil. Bulk density of organic soils is lower than mineral soils. Bulk density is relatively constant at mineral contents of 9%-70%. Above 70% mineral content, the bulk density increases markedly as the mineral content increases (Figure 2). The attributes of soil material that are expressed by the degree and kind of cohesion and adhesion or by the resistance to deformation or rupture are termed consistence. The consistence of fluid mineral soils can be expressed as the n-value. The n-value can be calculated for mineral 61 OM. 35 30 25 20 15 10 oc. 21 18 - 15 ~ 12 - 9 - 3- Organic Soil Materials .-$** ^^ AM ^ \&3 Nonorganic Soil Materials 10 20 30 40 50 Percent clay Organic soil materials thai are never saturated lof more than a lew days and containing more*than 20 percent organic carbon are also Included. Figure 1. Organic carbon requirements for organic soil materials. soil materials that are not thixotropic by the formula n=(A-0.2R)/(L+3H), where A=% water in a soil at field condition, calculated on a dry weight basis; R=% silt plus sand; L=% clay; and H=% organic matter (organic carbon X 1.724). Most soil materials deposited under water and never dried below field capacity have n-values of 1 or more (Figure 1). The n-value is helpful in indicating whether you can walk on the soil in the undrained state and the degree of subsidence that would occur following drainage. Contact with brackish or saline water affects soil properties and plant communities that grow on the soil. Chabreck (1972) reported a salinity classification related to the salt tolerances of 62 06 • o rgamc Soil ^ ■* Mm ;ral Soil Ma / enal — *- 05 E n a / Ifl £ 0.3 a 3 a • • ■/.. • • • • / 0.2 • • • • • • • • •• — 1 • • • • » * • 0.1 • • • • • • 10 20 30 40 50 60 70 Percent Mineral (Ash Percent of Oven Dry Weight) BO 90 100 Figure 2. Relationship of bulk density and mineral percentage. natural plant communities in Louisiana marshes. Freshwater marsh ranges from 0.0 to 6.66 ppt salt; intermediate marsh from 0.39 to 9.80 ppt salt; brackish marsh from 0.42 to 28.08 ppt salt; and saltwater marsh from 0.62 to 51.88 ppt salt. In addition to containing more soluble salts, the soils have a population of exchangeable cations that reflect the ionic composition of seawater. Seawater has an approximate cation composition of 3.4% calcium, 17.6% magnesium, 77.4% sodium, and 1.6% potassium. The anion composition is approximately 0.4% bicarbonate, 9.2% sulfate, and 90.2% chloride. Soils influenced by seawater soon equilibrate to have higher proportions of exchangeable sodium and magnesium than surrounding upland soils or soils in freshwater marshes. The salinity of the soil solution in the surface layer remains essentially in equilibrium with that of tidewater. Salinity of soil water varies because of variations in rainfall, storm tides, evaporation, and other features. Researchers have found a wide range in salt content in the soils of the coastal marshlands of Louisiana (Lytle and Driscoll 1970; Lytle 1971; Brupbacher et al. 1973). Soil salinity classes based on the electrical conductivity of the saturation extract are given below. Salinitv class Conductivity (ixS/cm) Salinitv ppt None <2.0 <1.25 Low 2.0- 4.0 1.25-2.5 Moderate 4.0- 8.0 2.5-5.0 High 8.0-16.0 5.0-10.0 Very High >16.0 >10.0 The loss of surface elevation after a soil with organic or fluid layers is artificially drained is termed subsidence (Stephens and Speir 1969). Subsidence of organic soils after drainage is attributed mainly to shrinkage due to desiccation, consolidation by loss of the buoyant force of ground water and by loading compaction, and biochemical oxidation. Elevation loss due to the 63 first two factors is termed initial subsidence and is normally accomplished in about 3 years after lowering the water table. Oven-dried samples of organic layers of a Kenner soil lost 85% of the original volume. Artificial drainage, however, does not reduce water content to that extent, and volume change under field conditions is less. Initial subsidence of organic soils is estimated to result in a reduction of thickness of the organic materials above the water table by about 50%, and it is accompanied by permanent open cracks that do not close when the soil is rewet. After initial subsidence, shrinkage will continue at a fairly uniform rate due to biochemical oxidation of the organic materials. This is termed continued subsidence and progresses until mineral material or the water table is reached. The rate of continued subsidence depends upon temperatures, the mineral content, and depth to water table. The rate increases with depth to the water table. Mineral soils with the fluid layers (n-value of 1 or more) have a potential for initial subsidence due to loss to water and consolidation after drainage. Classification of the soils is based upon selected chemical and physical properties as defined in Soil Taxonomy (U.S. Department of Agriculture 1974). The soils in Louisiana's coastal marsh may be classified as Aqualfs, Aquents, Saprists, or Aquepts. Aqualfs are mineral soils that have subsurface horizons that have formed structure and contain alluvial silicate clay. They have poor natural drainage and ground water stands close to the surface at some time during the year, but not during all seasons. Regional subsidence of coastal lands relative to mean sea level causes progressive inundation of former uplands. This class of soils is presumed to have developed in a previous weathering regime and subsequently submerged. This class constitutes about 3% of the coastal marsh. Aquents are mineral soils that have little or no evidence of development of pedogenic horizons. They are gray and permanently saturated with water. They have never dried; consequently bulk densities are low (about 0.6 g/cm3) and water contents are high (over 100%). Because of the high water content, soil strength is low, commonly too low to support grazing animals. The soil material is fluid. This class constitutes about 36% of the coastal marsh. Saprists are soils that are dominantly organic material. The organic layers contain more than 18% organic carbon if the mineral fraction is more than 50% clay, or more than 12% organic carbon if the mineral fraction has no clay. In addition to the required organic carbon content, saprists are organic soils that, except for thin mineral layers, extend from the surface to a depth of 40 cm and the organic material has a bulk density of 0.1 g/cm3 or more. The organic carbon consists of almost completely decomposed plant remains and the rubbed-fiber content is less than 15%. They are saturated with water most of the year, but fluctuation has allowed aerobic decom- position of some of the fibrous material. This class constitutes about 59% of the coastal marsh. Aquepts are mineral soils that have subsurface horizons that also have formed structure, but lack illuvial horizons enriched with silicate clay. Water stands close to the surface at some time of the year, but not during all seasons. These soils are on low ridges in the Chenier Plain. This class constitutes about 2% of the coastal marsh. SUMMARY AND CONCLUSIONS Although the soils of Louisiana's coastal marshland have a common characteristic of wetness, other generalizations are impossible unless the location and characteristics unique to each soil are 64 known. Important considerations in use, management, and understanding of the soils are water content, load-bearing capacity, subsidence potential, thickness and composition of organic layers, bulk density, and chemical properties. Data presented in soil survey reports establish relationships between soil characteristics which in turn are predictable through use of the soil classification system. Soil surveys provide a means for establishing a resource base. They are the vehicle by which knowledge of soils is transferred from one location to another. The criteria for classes (U.S. Department of Agriculture 1974) are useful and practical as a basis for developing soil series concepts. However, the need for new taxa to adequately classify soils of the coastal marsh has been recognized. Special equipment, such as air boats or helicopters, is needed to traverse marshes to prepare soil surveys in sufficient detail for intensive land use planning. A great need exists for the creation of a geographic information system for Louisiana's coastal zone. This system would serve as a primary data base for a comprehensive coastal plan and would include resource data such as edaphic features, land cover, hydrology, topography, and hydrography. There is also a pressing need to accelerate the soil survey of Terrebonne and St. Mary Parishes. They are now the only missing links in our chain of soil resource data of the coastal area. LITERATURE CITED Brupbacher, R.H., J.E. Sedberry, Jr., and W.H. Willis. 1973. The coastal marshlands of Louisiana. La. State Univ. Agric. Exp. Stn. Bull. No. 672. Chabreck, R.H. 1972. Vegetation, water, and soil characteristics of the Louisiana coastal region. La. State Univ. Agric. Exp. Stn. Bull. No. 664. Coleman, J.M. 1966. Recent coastal sedimentation: central Louisiana coast. Coastal Studies Series No. 17, Louisiana State University Press, Baton Rouge. Lytle, S.A 1971. The soils of Terrebonne Parish. La. State Univ. Agric. Exp. Stn. Bull. No. 651. Lytle, S.A, and Driskell, B.N. 1970. The soils of St. Mary Parish, Louisiana. La. State Univ. Agric. Exp. Sta. Bull. No. 645. Kniffen, F.B. 1968. Louisiana, its land and people. Louisiana State University Press, Baton Rouge. 196 pp. Russell, R.J., and H.V. Howe. 1935. Cheniers of southwestern Louisiana. Geogr. Rev. 25: 449-461. Stephens, J.C., and W.H. Speir. 1969. Subsidence of organic soils in the USA Assoc. Int. D'Hydrol. Sci. Extract Publ. No. 89, Colloque de Toyko. U.S. Department of Agriculture. 1973. Soil survey of St. James and St. John the Baptist Parishes, Louisiana. USDA Soil Conservation Service and Louisiana Agricultural Experiment Station. U.S. Department of Agriculture. 1974. Soil taxonomy: a basic system of soil classification for use in making and interpreting soil surveys. Agriculture Handbook No. 436, USDA Soil Conservation Service, Washington, DC. U.S. Department of Agriculture. 1977. Soil survey of Iberia Parish, Louisiana. USDA Soil Conservation Service and Louisiana Agricultural Experiment Station. U.S. Department of Agriculture. 1983. Soil survey of Jefferson Parish, Louisiana. USDA Soil Conservation Service and Louisiana Agricultural Experiment Station. 65 U.S. Department of Agriculture. 1984. Soil survey of Lafourche Parish, Louisiana. USDA Soil Conservation Service and Louisiana Agricultural Experiment Station. U.S. Department of Agriculture. [1988.] Soil survey of Calcasieu, Cameron, Orleans, Plaquemines, St. Bernard, St. Charles, St. Tammany, Tangipahoa, and Vermilion Parish, Louisiana. USDA Soil Conservation Service and Louisiana Agricultural Experiment Station. Unpubl. MS. 66 MODELING SEDIMENT DELIVERY TO LOUISIANA COASTAL SALT MARSHES: NATURAL PROCESSES AND OPTIONS FOR MANAGEMENT Denise J. Reed Louisiana Universities Marine Consortium Chauvin, LA 70344 ABSTRACT Loss of Louisiana's coastal salt marshes is frequently attributed to insufficient sedimentation to keep pace with the rapidly rising sea level. Loss of sediment input caused by controlling Mississippi River flow has reduced natural sedimentation rates but some sediment, both organic and inorganic, is still being actively deposited on the marsh surface. This study attempted to elucidate the natural process of sediment delivery to the marsh surface and identify the role of events of differing magnitudes in contributing sediment. Sediments samples were collected and water levels monitored during the winter and spring of 1987 near the Louisiana Universities Marine Center in Cocodrie, LA Short-term sediment deposition rates are compared to the amount of water flooding the marsh surface during monitoring periods. The results show a clear relationship between the amount of sediment deposited and the depth and duration of marsh flooding. Regular astronomical tidal flooding contributes very little sediment to the marsh compared to flooding associated with the passage of a cold front. The identification of this relationship allows existing tide-gauge records to be used to model the development of the present marsh, in terms of the frequency and magnitude of sediment deposition. Plans to manage and restore salt marshes subjected to sedimentation deficit frequently involve increasing the sediment input to the marsh areas. The results of this study show that sedimentation may not be limited by sediment availability but by mobilization and mechanisms of delivery to the marsh surface. Increasing available sediment in coastal salt marshes will not necessarily promote increased sedimentation, which will be dependent upon natural sediment delivery processes unless marsh flooding is also manipulated. Therefore, large-scale management plans for Louisiana's salt marshes should consider both the input of sediment necessary to overcome the sedimentation deficit and mechanisms of sediment distribution. INTRODUCTION One of the main causes of Louisiana's wetland loss, currently estimated at 0.86% per year (Turner and Cahoon 1987), appears to be insufficient sedimentation on the marsh surface. This sediment is required to maintain the marsh surface elevation in the face of a rising relative sea level and to provide nutrient stimulus to plant growth, itself a contributor to marsh accretion and soil development. Although studies have identified the marsh surface sedimentation in many areas as insufficient for these needs, some sedimentation is still occurring on the marsh surface in saline, brackish, and fresh environments. These sediments are being transported onto the marshes by natural processes, frequently operating in channels and canals altered by humans, and in areas which are not actively being managed. 67 Plans to divert sediment from the Mississippi River into marsh areas to alleviate the problem of sedimentation deficit must aim to manipulate these natural processes of sediment transport to enhance surface deposition. This study attempted to elucidate some of the natural processes which transport sediment onto salt marshes in east Terrebonne Parish and to develop a simple model of the delivery of sediments to the marsh surface. This model can be used to identify the potential role of events of differing magnitudes in contributing to marsh accretion, and how those events can be manipulated and managed to increase marsh surface sedimentation. METHODS Short-term variations in sediment deposition on the marsh surface were identified by using a filter paper sediment trap technique outlined by Reed (1987) in studies conducted near the Louisiana Universities Marine Center at Cocodrie, LA The results of those studies for December 1986 to April 1987 show great variation in the sediment deposition between different periods (Figure 1). The results are expressed as mean sediment deposition per day for periods varying from 1 to 4 weeks, the dates shown being the limits of the sampling periods. Reed (1987) attributed these variations to sediment availability for transport onto the marsh surface, and opportunity for sediment transport onto the marsh. The passage of winter cold fronts was seen to be especially important in both mobilizing sediment and transporting it onto the marsh surface. These data were used to develop a regression model relating the amount of sediment deposited to the magnitude of the inundation event producing the deposition. To do this, the data were reduced to the total amount of sediment deposited during each sampling period and the total "area" of the inundation peaks during each period. Water-level records were taken from the National Ocean Service (NOS) tide gauge at Cocodrie, LA, within 200 m of the sampling site. The inundation-peak area was calculated by using graphs of water-level variation and summing the areas above the line representing the general level of the marsh surface at the sampling site (Figure 2). The area of an individual tidal peak over the marsh surface reflects both the depth and duration of the inundation event. The sediment deposited during each period was regressed against the total area of the inundation peaks by using a simple regression model (Starview, Brainpower, Inc.). RESULTS The results, which include 44 individual inundation events, show a clear relationship between the amount of sediment deposited and the depth/duration of marsh flooding (Figure 3). Variation in "inundation area" explains 83% of the variation in sediment deposited. The results of the regression analysis confirm that regular tidal inundation during the winter months contributes very little sediment to the marsh surface, while the passage of cold fronts increases the inundation of the marsh and the amount of sediment deposited. This experiment was limited to the winter months of 1 year, but examination of water-level variations over other periods allowed the importance of these deposition events to be assessed as part of longer-term marsh-surface accretion. A similar model was applied to December-April water-level records in 1984-85 and 1985-86, and to records from January-December 1985, a year which included the passage of hurricanes Danny, Elena, and Juan. These data were obtained from the U.S. Army Corps of Engineers tide gauge at Cocodrie, LA, and the records converted to the same datum as that of the NOS gauge. The regression model was similar to that described above but used high- tide elevations rather than inundation-peak area for ease of data acquisition from the charts supplied 68 co oo co oo > o o c o CD cu ra Z Q Q ~> o i- co N CO t- CNJ oo c CO -J en co c CO —) m oo oo oo co co .a n CU CO c\j o i- CM CO CO a. S 2 < t ^ w CNJ a. a. < < co co T" CM o co Figure 1. Mean daily sediment deposition for sampling periods December-April 1985. > CD "5 13 -1 — 15 1 1 i 17 19 21 December — i — 23 r 25 Figure 2. Water level graph for period in December 1986 showing threshold line for flooding the marsh surface, above which inundation peak area was measured. 69 y = .101x + .017, R-squared: .826 E £ o Q. Q E T3 (D O 2.6. 6 8 10 12 Area of inundation peaks (mhrs) Figure 3. Regression analysis of total sediment deposited vs. area of inundation peaks. by the Corps. The regression on the 1987 data using high-tide elevation instead of inundation- peak area produces an r2 value of 0.77. This shows that variation in high-tide elevation explains 77% of the variation in total sediment deposited. In 1987, six tides reached elevations of over 0.8 m above datum, whereas none did during winter 1985, and only two reached such elevations during winter 1986. The modal high-tide elevation is the same for all 3 years. The marsh surface floods at approximately 0.6 m above datum and Figure 4 shows that fewer tides flooded the marsh surface in 1986 than in either of the other years. Although part of a frontal event in late March 1987 produced high tide, comparison with the distribution of high-tide elevations for 1985 shows that this event was small in relation to the effect of hurricanes (Figure 5). The maximum water level reached at Cocodrie during Hurricane Juan, October 1985, was underestimated because the water level reached the table level of the tide gauge and the float was unable to rise any higher for a period of several hours. Table 1 summarizes the results obtained from application of the model to winter 1985 and 1986 and calendar year 1985. These data indicate higher winter deposition during 1985 than 1986 associated with an increased frequency of overmarsh flooding and an increase in the magnitude of the greatest inundation event, shown by the height of the high tide. However, comparison of these figures for 5 months of the year with the results for a complete calendar year do not show, as frequently suggested (Baumann 1980; Baumann et al. 1984; Cahoon and Turner 1987; Reed 1987), that deposition in salt marshes primarily occurs during winter frontal passages. Initially, 1985 may be thought to be an anomalous year that includes the effects of several hurricanes. However, detailed examination of the figures shows that "hurricane tides," defined here as those reaching a greater elevation than that of the highest cold front measured during 1987, contribute only 6.6% 70 >» o c a? CT Q) v- ■ 1985 0 1986 B 1987 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 Height of winter high tides, December - April (m) 1.2 Figure 4. Frequency distributions for winter (Dec-Apr.) high tide elevations in 1985, 1986, and 1987. 30 o CT *S 10 0 A • ■ 1985 Jan - Dec m 1987 Winter 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 Height of high tides (m) Figure 5. Distribution of high tide elevations for winter 1987 and calendar year 1985. 71 Table 1. Summary of results for application of model to high tide data from 1985 and 1986 winters, and calendar year 1985. No. inundation Highest high Deposition events tide (m) (g) 1986 Winter 11 1985 Winter 36 1985 Jan.-Dec. 149 0.77 0.116 0.82 0.369 2.23 1.654 of the deposition for the whole year. The most important aspect according to the model appears to be the high frequency of inundation during the 1985 calendar year, which the model uses to accumulate sediments on the marsh surface. DISCUSSION The results shown above suggest that the model overestimates sediment deposition on the marsh surface during the summer months. It is important to note that the model is based upon data collected during winter months. Thus, the high-magnitude inundation events shown in the original data are those associated with cold fronts, when sediment is both mobilized by strong southerly winds and transported onto the marsh surface as the water is forced up into the marshes from the bays (Reed 1987). Examination of continuous water-level records for Cocodrie, LA, during analysis of these data indicated an increase in the mean height of tides during the summer and fall and a corresponding increase in the frequency of low-magnitude marsh inundation. Only 24% of tides which flood the marsh during the complete calendar year occur between January and April 1985. The model assumes that all inundation events are the same in terms of their potential to deposit sediments on the marsh surface. This is an inappropriate assumption when applied to all seasons of the year. Although the marsh may be frequently flooded during the summer months even in years without significant hurricane activity, sedimentation will not necessarily occur if floodwaters have low suspended-sediment concentrations. The effect of pre-frontal winds in producing onshore waves and water-level set-up has also been identified by using remote-sensing data (Roberts et al. 1987). Effects will be similar during the passage of hurricanes, and the precise effects, as with cold fronts, will depend upon the orientation to the coastline. Thus, the model of sediment deposition, which assumes available suspended sedi- ment for deposition during marsh flooding, may be applicable to the high- magnitude inundation events associated with the hurricane passage in 1985. However, it is not applicable to low- magnitude summer tidal inundations associated with prevailing onshore winds which produce insuffi- cient wave activity to significantly suspend bay-bottom sediments and transport them into the marsh. The implications of these results for managing sedimentation in Louisiana's coastal marshes are that sediment will not be deposited on the marsh surface unless it is available for deposition and 72 the opportunity for transport onto the marsh surface occurs. These conditions frequently coincide during the passage of winter frontal systems. Increasing sediment deposition requires an increase in sediment availability for deposition, by increasing the suspended-sediment concentrations at times when it would otherwise be low, but also at times when it can be transported onto the marsh surface. Under natural conditions, suspended-sediment concentrations increase during periods of strong southerly winds. Increasing suspended-sediment concentrations in marsh floodwaters, other than by these natural processes, is one of the keys to increasing marsh-surface sedimentation. Diverting sediments from the Mississippi River into coastal basins will achieve an increase in suspended-sediment concentration over the basin as a whole while sediment is actively being diverted. Such sediments will, however, be readily deposited unless sufficient hydraulic gradients can be maintained as sediment-laden waters diffuse throughout the basins. Deposition will only occur on the marsh surface if increased sediment suspensions coincide with marsh inundation events. The natural processes and patterns of marsh flooding should be incorporated into plans to divert sediments for increasing marsh-surface accretion. Increasing sediment concentrations without consideration of sediment delivery processes will merely increase sediment storage within basins, coastal bays, and deeper channels. This sediment will only be available for deposition on the marsh surface when mobilized by natural sediment transport processes. Where marsh inundations are actively managed and, thus, the opportunity for marsh-surface deposition exists, it may be possible to allow sediment inputs to a marsh area and gain some nutrient stimulus to plant growth and soil development, while minimizing the incursion of saltwater. Careful assessment of individual events and high-tide elevations could allow water-control structures to allow maximum sediment input in short periods. Similarly, identifying those events which increase suspended-sediment concentration, and excluding them, is an important management concern for areas where reduced turbidity is considered desirable. CONCLUSIONS Marsh-surface sedimentation appears to be limited by suspended-sediment availability in flood waters rather than by inundation events. Optimal natural conditions for marsh-surface deposition occur during the passage of cold fronts and tropical storm or hurricane conditions. This has frequently been observed by workers studying seasonal variations in salt marsh accretion. While it is important to recognize that suspended-sediment availability is the limiting factor in natural depositional processes, the role of inundation events in delivering that suspended sediment to the marsh surface should not be dismissed. Techniques to increase suspended-sediment availability may be more readily available than those which successfully manipulate marsh-surface flooding. Understanding the combination of the two processes and their coincidence under certain natural conditions can assist management schemes at all scales which attempt to either minimize or maximize sediment delivery to the marsh surface. ACKNOWLEDGMENTS This study was completed with the support of the Louisiana Universities Marine Consortium and its facilities. Daniel Lee assisted with data analysis and presentation. 73 LITERATURE CITED Baumann, R.H. 1980. Mechanisms of maintaining marsh elevation in a subsiding environment. M.S. Thesis. Louisiana State University, Baton Rouge. 90 pp. Baumann, R.H., J.W. Day, Jr., and C.A. Miller. 1984. Mississippi deltaic wetland survival: sedimentation versus coastal submergence. Science 224:1093-1095. Cahoon, D.R., and R.E. Turner. 1987. Marsh accretion, mineral sediment deposition, and organic matter accumulation: clay marker horizon technique. Pages 259-275 in R.E. Turner and D.R. Cahoon, eds. Causes of wetland loss on the coastal central Gulf of Mexico. Volume 2: Technical narrative. Minerals Management Service, New Orleans, LA OCS Study/MMS 87- 0120. Reed, D.J. 1987. Short-term variability in salt marsh sedimentation, Terrebonne Bay, Louisiana. Pages 221-234 in N.V. Brodtmann, ed. Fourth water quality and wetlands management conference proceedings. New Orleans, LA, September 24-25. Roberts, H.H., O.K. Huh, L.J. Rouse, and D. Rickman. 1987. Impact of cold-front passages on geomorphic evolution and sediment dynamics of the complex Louisiana coast. Coastal Sediments 87:1950.1963. Turner, R.E., and D.R. Cahoon, eds. 1987. Causes of wetland loss on the coastal central Gulf of Mexico. Volume 2: Technical narrative. Minerals Management Service, New Orleans, LA. OCS Study/MMS 87-0120. 400 pp. 74 RESPONSE OF LOUISIANA GULF COAST MARSHES TO SALTWATER INTRUSION S.R. Pezeshki, R.D. DeLaune, W.H. Patrick, Jr., and B.J. Good Laboratory for Wetland Soils and Sediments Center for Wetland Resources Louisiana State University Baton Rouge, LA 70803-7511 ABSTRACT A review is presented of carbon assimilation response of wetland vegetation from brackish marsh, freshwater marsh, and bottomland hardwood to flooding and salinity for several species representative of wetland habitats from the Louisiana coastal area. The combination of salinity and soil anaerobiosis adversely affected photosynthetic rates for many wetland plant species. Results suggest that saltwater intrusion and brine discharge, common problems along the Louisiana coast, will adversely affect normal plant physiological functions. Reduction in carbon assimilation, leaf tissue death, and other responses will lead to stressed plants with decreased productivity followed by habitat changes. Plant successional patterns and marsh management strategies in relation to changes in salinity and marsh soil physicochemical properties are also discussed. INTRODUCTION Louisiana contains vast (3.2 million ha) coastal marshes representing 41% of those in the continental United States (Turner and Gosselink 1975). The marshes extend inland from the Gulf of Mexico for distances ranging from 24 to 80 km (Figure 1) and reach their greatest width in southeastern Louisiana (Chabreck 1972). Features of the Louisiana coast are closely related to the geological history of the Mississippi River. Deterioration of the coastal wetlands began in the early 20th century when the Mississippi River was leveed. In this century, decreased sedimentation has resulted partly from efforts to maintain the Mississippi River in its present channel. This loss of sediment and compaction of existing sediment is a primary factor in the loss of Louisiana wetlands. Currently marshes are deteriorating at the rate of over 130 km2/yr (Gagliano 1981). The marshes of the coastal wetlands, both deltaic and chenier plains, exhibit a striking zonation of emergent plants (Figure 2). Vegetation types range from saline near the Gulf of Mexico to brackish, then freshwater, then bottomland hardwood with increasing distance from the gulf. Water levels in the marshes are affected by rainfall, tides, and local drainage patterns. Vegetation types are influenced by hydrology, salinity, and the type of sediment involved. The mixing of saltwater from the gulf and freshwater from inland sources provides a spatial zonation in water salinities. Water salinities are high (20 to 25 ppt) near the coastline and gradually decline inland until a zone of freshwater is reached along the northern perimeter of the marsh region (Chabreck 1981). The vegetation is confronted with progressively rising water levels (submergence) in many wetland habitats of the Louisiana coast primarily because of the rapid subsidence. Water-level 75 CO T3 C ♦^ 0) (A (0 o O (0 c CO w 3 O c 2 SJ O O S3 a JS H 9 ex 76 Si. '/ ■A . O C ID 3 U £3 "8 § i 3 OJ) nj m a. S3 a a •— 09 amb sylv us s = 8 ® •p* a .sr>>5 IjZ O E 3 5(8 w.y WHZ 2 c'c o ^ jus! CO AS n « o 5 " E o to nj*^ ^ -C m E»-'S|E OWhCOQ-Q- I e a a V *- X V I •3 e & a g a "3 ■o c 3 3 s ** . I*5 Cl sc «~ 2 o -* *.£* 03 s - js 3> w JS B • N st 3 S U- 3 77 increase along the coast is several times faster than eustatic sea level change for the Gulf of Mexico, which has been estimated to be 0.23 cm/yr (Barnett 1984). Salinity increases occur simultaneously in the coastal marshes. Marsh surfaces developing in rapidly subsiding, sediment-deficient environments, such as those in coastal Louisiana, are maintained in the intertidal zone through plant growth, organic detritus accumulation, and limited mineral sediment deposition (DeLaune et al. 1983). The depth of organic layer is determined by the amount of real and local subsidence, eustatic sea level change, organic matter oxidation, and vegetative growth. As plant growth tends to keep pace with the relative rise of sea level, both organic detritus and mineral sediments are entrapped, resulting in the gradual aggradation of the surface (DeLaune et al. 1978). The two processes can be viewed as working in a synergistic manner. Any salinity increase can reduce plant growth and then indirectly affect marsh formation. Marsh deterioration along the Louisiana coast is a complex problem and is seemingly the result of numerous factors including salinity. In addition to geological factors, human activities such as canal construction and leveeing are also cited as having an indirect effect on land loss (Craig et al. 1979) by accelerating rates of water-level and salinity increase and storage. In addition to salinity increase resulting from subsidence, brine or produced water being discharged into coastal Louisiana can also potentially affect vegetation, marsh stability, and wetland deterioration in regions of discharge. It is estimated that more than 75 million gallons of brine water produced as by-products of petroleum recovery operations is discharged in coastal Louisiana marshes per day. This method is a practice widely used in oil and gas fields in south Louisiana. The produced waters are highly saline, sometimes in the range of 100 to 200 ppt salt concentration, i.e., as much as 5 times greater salt concentrations than the salinity of sea water. Such concentration is likely to be toxic to plants including the most salt-tolerant coastal vegetation. In freshwater areas, brine discharge with salinity levels of less than 5 ppt may be detrimental to vegetation and water quality of the marsh. RESPONSE OF LOUISIANA WETLAND PLANT SPECIES TO SALINITY Saltwater intrusion and brine discharge along the Louisiana coast can impact survival and growth of wetland species within various habitats. In salt marsh species such as Spartina altemiflora, indirect evidence suggests an adverse effect of high salinity on photosynthesis and growth of this species (Gosselink et al. 1977; Drake and Gallager 1984). In a study of response of S. patens, a dominant brackish marsh species, to salinity, it was found that salt concentrations in the range of 22 ppt caused up to 60% reduction in net carbon assimilation rates (Pezeshki et al. 1987b). Results of this study indicated that elevated salinity could potentially reduce productivity of brackish marshes. The impact of saltwater intrusion in Louisiana freshwater marshes is expected to be greater than in brackish marshes, assuming comparable salt concentrations since freshwater marshes are composed of highly salt-sensitive species. For example, in Panicum hemitomon, a dominant freshwater marsh species, exposure to saltwater containing 5 ppt salt reduced net carbon assimilation rates 74% and 76% (Pezeshki et al. 1987c). Salt concentration of 12 ppt caused tissue death within 4 days of salt exposure. In Sagittaria lancifolia, another important gulf coast freshwater marsh species, saltwater treatment caused substantial decrease in net carbon assimilation (Table 1). The stomatal limitation of photosynthesis, however, was relatively small, ranging between 78 Table 1. Summary of available data on reduction of carbon assimilation in response to increased salinity for selected wetland species of the Louisiana gulf coast (modified after Pezeshki et al. 1989). Reduction percentages are based on the average diurnal values compared to pre-stressed levels. Species Salinity level (PPt) No. of days exposed Reduction in carbon assimilation Morphological responses Reference Taxodium distichum 2 and flooding 30-40 58% Yellowish color leaves by 20th day of exposure to salt Pezeshki et al. 1986 4 and flooding 30-40 74% Leaf burning by the 8th day of exposure to salt Pezeshki et al. 1986 6-7 and flooding 30-40 84% Extensive leaf burning by 8th day of exposure Pezeshki et al. 1986 Nyssa aquatica 3 and flooding 30-42 18% Yellowish color leaves by 15th day of salt exposure Pezeshki et al. 1988a Panicum hemitomon 5 and flooding 7 76% Slight leaf burning Pezeshki et al. 1987c 12 and flooding 7 data unavailable Plant died after 4th day of exposure Pezeshki et al. 1987c Sagittaria lancifolia 3 and flooding 30-40 45% Leaf burning Pezeshki et al. 1987e Scirpus olneyi 3 and flooding 80 No reduction Slight leaf discoloration Meeder et al. 1989 7 and flooding 80 18% Leaf burning Meeder et al. 1989 10 and flooding 80 50% Severe mortality Meeder et al. 1989 (Continued) 79 Table 1. Concluded. Species Salinity level (PPO No. of days exposed Reduction in carbon assimilation Morphological responses Reference Spartina patens 9-12 and flooding 7 48% none Pezeshki et al. 1987b 14-22 and flooding 7 60% none Pezeshki et al. 1987b 12% and 18%. This finding indicated that, in addition to diffusional limitations, photosynthetic capacity was reduced through metabolic factors (Pezeshki et al. 1987e). In Scirpus olneyi plants, salinities of 7 ppt and 10 ppt caused immediate reduction in carbon fixation (Meeder et al. 1989). Nevertheless, in this species, some photosynthetic recovery was noted in all treatments including those plants which survived the 10-ppt saltwater treatment. This recovery indicated that some photosynthetic acclimation occurred in this species especially at these salinity concentrations. Many tree species respond to soil flooding by stomatal closure and reduction of net photosynthesis (Kozlowski and Pallardy 1979; Newsome et al. 1982; Tang and Kozlowski 1982; Zaerr 1983; Pezeshki and Chambers 1985a,b). However, few studies have been conducted to assess carbon assimilation responses of bottomland tree species to saltwater intrusion. Coastal tree species are more susceptible to salinity than flooding alone or there may be a synergistic effect of combined flooding and salt on photosynthetic process. In Fraxinus pennsylvanica seedlings, carbon assimilation rates declined following salt application in the absence of flooding. Net carbon assimilation was reduced as much as 86% in response to soil salinity. The study demonstrated the high level of sensitivity of green ash, a flood-tolerant species, to soil salinity; however, it did not examine the effect of combined stresses and their possible interaction on carbon assimilation rates of this species. Recent studies on baldcypress (Taxodium distichum) seedlings showed a 58% to 84% reduction in net assimilation rates when plants were exposed to saline water which contained salt concentrations in the range of 2 to 7 ppt (Pezeshki et al. 1986, 1987a). The impact was evident for all salinity levels and was closely related to the salinity of flood water (Table 1). In an experiment conducted on tupelo-gum (Nyssa aquatica) seedlings, it was found that floodwater containing 3 ppt salt caused substantial reduction in net assimilation throughout the day, and the effects persisted for the entire 12 weeks of the experiment. Furthermore, the interaction of salt and flooding was significant (Pezeshki et al. 1988a). Although the gas exchange rates are different depending on the species, leaf age, and the time of measurement during a growing season, diurnal patterns for non-stressed plants appear to be similar in marsh plants. Generally, saltwater intrusion causes stomatal closure as well as reduction of carbon assimilation rates throughout the day, altering normal gas exchange patterns, and consequently reducing the net diurnal carbon Fixation (Pezeshki et al. 1986, 1987a, b, c, d, e). 80 The overall response of wetland species from coastal Louisiana to saline water treatment is a relatively long-lasting reduction in net carbon assimilation rates (Table 1). This response agrees with studies reporting the effects of salt stress on coastal plants from other wetland regions (Longstreth and Strain 1977; Drake and Gallagher 1984; Pearcy and Austin 1984). The response ranges from decline in gas exchange rates under low salt concentrations to complete tissue death under high salinity, especially in freshwater marsh species. The overall effect of decline in daily rates of gas exchange is reduced carbon fixation leading to inhibition of growth and productivity. The reported studies of selected wetland species from the Louisiana gulf coast shows that saltwater intrusion causes reduction of net photosynthesis in wetland plants. The effect is dependent on vegetation type and concentration of salt. The observed impacts are at salt levels similar to those currently occurring in coastal Louisiana because of saltwater intrusion and brine discharge from oil recovery operations (Salinas et al. 1986). Results suggest that many of these species continue to encounter an increasingly greater level of stress as a result of saltwater intrusion. The stress-induced reduction in photosynthetic rates adversely affects carbon fixation and net primary productivity of brackish species which are experiencing saltwater intrusion. Freshwater habitats including freshwater marshes and bottomland forests will also be affected as saltwater intrusion continues inland. Reduction in productivity of wetland species will affect estuarine carbon cycling as well as organic matter pools, the important governing factors for vertical marsh accretion (DeLaune et al. 1978). Organic carbon accumulation is essential in maintaining intertidal marshes. Smith et al. (1983) reported that approximately 292 g C/ma are accumulated through processes of vertical marsh accretion in brackish marshes in Louisiana. The source of this organic carbon is mainly from primary production of marsh macrophytes. Reduction in this source will adversely affect the ability of these marshes to remain intertidal, causing further marsh degradation. Similar effects on net primary productivity, carbon allocation, and nutrient cycling are expected in lowland coastal forests where the effect of these stresses are beginning to appear. Further research is needed to study the long-term responses of other important wetland species from the gulf coast region to gradual increases in flooding and salinity under field conditions and to examine the effects on survival, productivity, and nutrient cycling of major ecosystems. MANAGEMENT IMPLICATIONS The general consequences of hydrologic changes resulting from canalization, subsidence, and sediment deprivation are a net movement of marine water northward into Louisiana's coastal wetlands. This is characterized by an overall increase in reducing conditions, increased salinities, and increased hydrogen sulfide production in marsh soils. Many emergent marsh communities have apparently disappeared due to the detrimental effects of these stress factors. Increased open water exacerbates the problem because this causes greater edge exposure and erosion. There is a general consensus that the continuing loss of this wetland resource base is unacceptable. Responsible management must be directed to the extent possible toward finding cost-effective means to reverse or slow down the effects of marine water encroachment, and aid impacted wetland communities to adapt to these changes. To reduce the amount of marine water in our wetland systems, additional freshwater must be introduced or marine water must be physically prevented from entering the system. The freshwater diversion project at Caernarvon is an excellent example of management designed to add freshwater 81 to dilute marine water with freshwater. Given the estimated cost of these projects (25 million dollars for the Caernarvon project alone) and the limited number of suitable sites for such projects, this approach is not generally feasible. Currently proposed methods to prevent saltwater intrusion rely on physical barriers such as weirs and levees to control water exchange rates. Strenuous objections to this approach have been raised on the grounds that the altered hydrology may result in diminished overall estuarine productivity, increased marsh break-up, and limited sediment input to the enclosed area. On the other hand, proponents of this approach counter that these problems are preferable to complete loss of the resource and that for the most part there are not enough sediments available for input to compensate for the amount that will be lost as a result of the wholesale marsh erosion that follows the death of the emergent vegetation. Research is now in progress that we hope will shed some light on this controversial issue. The question of facilitating the adjustment of our wetland communities to the above-mentioned changes also needs to be seriously investigated. In the case of forested wetlands, the work mentioned dealing with cypress, tupelo gum, and green ash indicated that unless freshwater conditions are maintained, these species will not survive. There are no known tree species that will tolerate prolonged flooding and high salinities at Louisiana latitudes. Louisiana is on the northern fringe of the range of black mangrove, Avicennia germinans, and it is only represented by underdeveloped individuals in the southernmost part of the State. A cold-hardy variety would have application to this problem. In the case of herbaceous marsh communities, the situation is not as bleak as in the case of the forested wetlands. There are several species capable of tolerating various degrees of flooding and salinity stress. Among those tolerant of saline marsh conditions are Juncus roemerianus, Distichlis spicata, Spartina alterniflora, Batis maritima, and Salicomia spp. Those tolerant of brackish conditions include Spartina patens, Scirpus olneyi, and Scirpus robustus. By far the most important of these species in terms of management potential is Spartina alterniflora because of its unique ability to withstand extreme levels of flooding and salinity. Spartina alterniflora marshes are traditionally restricted to the coastal areas characterized by greater concentrations of mineral soil than the brackish and intermediate marshes interior to them (Chabreck 1972). Thus, as marine water moves farther northward, edaphic conditions may prove unsatisfactory for large scale colonization by Spartina alterniflora. Data regarding this question are inconclusive to date, and further research is needed. For instance (Figure 3), it has been documented that salt marsh soil with bulk densities below 0.20 g/cm3 will not support growth of Spartina alterniflora (DeLaune et al. 1979; DeLaune 1988). Mineral sediment associated with higher bulk densities is a source of iron and manganese which can precipitate sulfide formed from the reduction of sulfate in seawater which inundates the salt marsh near the coast. Pezeshki et al. (1988b) demonstrated that sulfide can reduce photosynthetic activity of Louisiana wetland plants under certain soil conditions. Much of Louisiana brackish marsh soil contains soil bulk densities of 0.20/g cm3 or less (Hatton et al. 1983; DeLaune 1988). Thus, it is questionable if Spartina alterniflora can colonize lower density brackish marsh due to the above-mentioned soil-plant chemistry relationships. It would be possible only if the transition is gradual and accompanied by sufficient sediment deposition to increase the soil bulk density to the level which will support growth of Spartina alterniflora. If Spartina alterniflora will successfully reproduce in selected areas and it is infeasible to sufficiently reduce the effects of marine water, then the management objective of erosion prevention would probably best be fulfilled by introducing this species into those areas which possess the characteristics to promote its regeneration. 82 CM £ a C (0 a a 4) > a ^.3\J\J • • • • • • 2000 • • 1500 • • •• • • 1000 • • • 500 • 0 I • V i . i ll 0 0.10 0.20 0.30 0.40 0.50 Soli Density Figure 3. Relationship between soil bulk density and standing crop biomass of Spartina alterniflora (from DeLaune et al. 1988). It should be noted that continuing subsidence will eventually increase water depths beyond the threshold that even Spartina alterniflora will endure. Unless organic production by emergent species can keep up with the accretion deficit, the adaptation alternative will serve only to increase the life expectancy of our mashes. Given the highly organic nature of our soils, the historic significance of plant production to accretion rates is obviously important. Therefore, it is critical that a model of projected subsidence rates be developed on a coast-wide basis that can be adjusted 83 for changes in sea-level rise, and that the interaction of plant productivity with the chemical processes that occur in various marsh soils when impacted by marine water be better understood. Only then will we be in a position to adequately assess the management alternatives available, the trade-offs they represent, and their implications for Louisiana's wetlands. ACKNOWLEDGMENT Funding for this study was provided by the Louisiana Education Quality Support Fund, LEQSF(1987-90)-RD-A-7. LITERATURE CITED Barnett, T.P. 1984. The estimation of "global" sea level change: a problem of uniqueness. J. Geophys. Res. 89(C5): 7980-7988. Chabreck, R.H. 1972. Vegetation, water and soil characteristics of the Louisiana coastal region. La. State Univ. Agric. Exp. Stn., Bull. No. 664. Baton Rouge. Chabreck, R.H. 1981. The effect of coastal alterations on marsh plants. Pages 92-98 in D.F. Boesch, ed. Proceedings of the conference on coastal erosion and wetland modification in Louisiana: causes, consequences and options. U.S. Fish Wildl. Serv. FWS/OBS-82/59. Craig, N.J., R.E. Turner, and J.W. Day, Jr. 1979. Land loss in coastal Louisiana (USA). Environ. Manage. 3(2):133-134. DeLaune, R.D. 1988. Processes of formation and degradation of marshes along the Louisiana gulf coast. Ph.D. Dissertation. Wageningen University, Wageningen, The Netherlands. 170 pp. DeLaune, R.D., R.J. Buresh, and W.H. Patrick, Jr. 1978. Sedimentation rates determined by 137Cs dating in a rapidly accreting salt marsh. Nature (London) 275:532-533. DeLaune, R.D., R.J. Buresh, and W.H. Patrick, Jr. 1979. Relationship of soil properties to standing crop biomass of Spartina altemiflora in a Louisiana salt marsh. Estuarine Coastal Mar. Sci. 8:477-487. DeLaune, R.D., R.H. Baumann, and J.G. Gosselink. 1983. Relationship among vertical accretions, coastal submergence and erosion in a Louisiana gulf coast marsh. J. Sediment. Petrol. 543(1):147-157. Drake, B.G., and J.L. Gallagher. 1984. Osmotic potential and turgor maintenance in Spartina altemiflora. Oecologia (Berl.) 62:368-375. Gagliano, S.M. 1981. Special report on marsh deterioration and land loss in the deltaic plain of coastal Louisiana. Presented to Frank Ashby, secretary, Louisiana Department of Wildlife and Fisheries. Coastal Environments, Inc., Baton Route, LA. Gosselink, J.G., C.S. Hopkins, and R.T. Parrondo. 1977. Growth physiology of marsh plants. U.S. Army Corps Eng., Waterways Exp. Stn., Vicksburg, MS. 49 pp. Hatton, R.H., R.D. DeLaune, and W.H. Patrick, Jr. 1983. Sedimentation, accretion, and subsidence in marshes of Barataria Basin, Louisiana. Limnol. Oceanogr. 26(3):494-500. Kozlowski, T.T., and S.G. Pallardy. 1979. Stomatal responses of Fraxinus pennsylvanica seedlings during and after flooding. Physiol. Plant. 46:155-158. Longstreth, D.J., and B.R. Strain. 1977. Effects of salinity and illumination on photosynthesis of Spartina altemiflora. Oecologia (Berl.) 31:191-199. 84 Meeder, J.F., R.D. DeLaune, and S.R. Pezeshki. [1989.] Scirpus olneyi response to changes in salinity regime: field and laboratory documentation. Mar. Biol. (In Press). Newsome, R.D., T.T. Kozlowski, and Z.C. Tang. 1982. Responses of Ulmus americana seedlings to flooding of soil. Can. J. Bot. 60:1688-1695. Pearcy, R.W., and S.L. Austin. 1984. Effects of salinity on growth and photosynthesis of three California tidal marsh species. Oecologia 62:68-73. Pezeshki, S.R., and J.L. Chambers. 1985a. Stomatal and photosynthetic response of sweetgum (Liquidambar styraciflua) to flooding. Can. J. For. Res. 15:371-375. Pezeshki, S.R., and J.L. Chambers. 1985b. Response of cherrybark oak (Quercus falcata van pagodifolia) seedlings to short-term flooding. For. Sci. 31(3):760-771. Pezeshki, S.R., and J.L. Chambers. 1986. Effect of soil salinity on stomatal conductance and photosynthesis of green ash (Fraxinus pennsylvanica). Can. J. Forest Res. 16:569-573. Pezeshki, S.R., R.D. DeLaune, and W.H. Patrick, Jr. 1986. Gas exchange characteristics of baldcypress: evaluation of responses to leaf aging, flooding, and salinity. Can. J. For. Res. 16:1394-1397. Pezeshki, S.R., R.D. DeLaune, and W.H. Patrick, Jr. 1987a. Physiological response of baldcypress to increases in flooding salinity in Louisiana's Mississippi River Deltaic Plain. Wetlands 7:1-10. Pezeshki, S.R., R.D. DeLaune, and W.H. Patrick, Jr. 1987b. Response of Spartina patens to increasing levels of salinity in rapidly subsiding marshes of the Mississippi River Deltaic Plain. Estuarine Coast. Shelf Sci. 24:389-399. Pezeshki, S.R., R.D. DeLaune, and W.H. Patrick, Jr. 1987c. Response of the freshwater marsh species, Panicum hemitomon, to increased salinity. Freshwater Biol. 17:195-200. Pezeshki, S.R., R.D. DeLaune, and W.H. Patrick, Jr. 1987d. Effects of salinity on ion uptake, leaf ionic content, and photosynthesis of baldcypress (Taxodium distichum L.). Am. Midi. Nat. 119:185-192. Pezeshki, S.R., R.D. DeLaune, and W.H. Patrick, Jr. 1987e. Effect of flooding and salinity on photosynthesis of Sagittaria lancifolia. Mar. Ecol. Prog. Ser. 41:87-91. Pezeshki, S.R., W.H. Patrick, Jr., R.D. DeLaune, and E.B. Moser. 1988a. Effects of waterlogging and salinity interaction on Nyssa aquatica seedlings. For. Ecol. Manage. 27:41-51. Pezeshki, S.R., S.Z. Pan, R.D. DeLaune, and W.H. Patrick, Jr. 1988b. Sulfide-induced toxicity: inhibition of carbon assimilation in Spartina alterniflora. Photosynthetica 22:437-442. Pezeshki, S.R., R.D. DeLaune, W.H. Patrick, Jr. 1989. Assessment of saltwater intrusion impact on gas exchange behavior of Louisiana gulf coast wetland species. Wetlands Ecol. Manage. 1:21- 30. Salinas, L.M., R.D. DeLaune, and W.H. Patrick, Jr. 1986. Changes occurring along rapidly submerging coastal area; Louisiana, U.S.A. J. Coastal Res. 2(3):269-284. Smith, C.J., R.D. DeLaune, and W.H. Patrick, Jr. 1983. Carbon dioxide emission and carbon accumulation in coastal wetlands. Estuarine Coastal Shelf Sci. 17:21-29. Tang, Z.C., and T.T. Kozlowski. 1982. Physiological, morphological, and growth responses of Platanus occidentals seedlings to flooding. Plant Soil. 66:243-255. Turner, R.E., and J.G. Gosselink. 1975. A note on standing crops of Spartina alterniflora in Florida and Texas. Contrib. Mar. Sci., Univ. Tex. 19:113-118. Zaerr, J.B. 1983. Short-term flooding and net photosynthesis in seedlings of three conifers. For. Sci. 29(l):71-78. 85 THE EFFECT OF DRYING AND ELECTRICAL CONDUCTIVITY ON UREASE ACTIVITY IN A BRACKISH MARSH1 G. C. Sigua and W.H. Hudnall Department of Agronomy, Louisiana Agricultural Experimental Station, LSU Agricultural Center Baton Rouge, LA 70803 ABSTRACT Surface horizons of brackish marsh soils collected at Hackberry, LA were studied to determine the effect of soil drying and electrical conductivity on soil properties that are related to urease activity. Soil drying significantly reduced urease activity and increased the conductivity and concentration of water-soluble Na, Fe, Mn, Mg, and Ca. There was a significant decrease in soil pH at the end of 3 months drying. These soils and soil-related factors were significantly correlated to soil moisture. There was a general reduction in urease activity as levels of conductivity increased. Addition of gypsum did not result in any significant increase of urease activity, but there was a numerical increase of 50% in urease activity of soil treated with 20 Mg/ha more than the control. An equation is presented that best accounts for variation in urease activity in brackish marsh soil. INTRODUCTION Wetland loss in Louisiana is a widely recognized problem. Each year, Louisiana loses approximately 50 mi to natural subsidence, erosion, and human intervention (Louisiana Department of Natural Resources 1986). Marshes, as part of our land and natural water regime, are irreplaceable natural resources that must be preserved. One of the possible solutions for saving wetlands from natural and accelerated losses is through restoration of vegetation. Restoration with suitable marsh vegetation usually requires some elaborate management practices that include soil drainage, fertilization, and various other cultural practices. Soil drainage and fertilization are the two most important components for two reasons: a) soil drainage, which is especially important at the seedling or early stage of growth establishment, is likely to affect the microbial and physicochemical properties of the soil, and b) although most marsh soils in Louisiana contain considerable amounts of organic carbon (OC), the marsh is most limited in N (Broome et al. 1975; Patrick and DeLaune 1976; Mendelssohn 1979; Smart and Barko 1980). The work reported here identifies some of the probable effects on soil properties associated with drying brackish marsh for an extended period. Data are presented on the causes of low N availability in the marsh and the relationships between soil urease activity and soil properties at different soil moisture contents. Although there are several studies limited to well-drained soils (Conrad 1940; Stojanovic 1959; Zantua and Bremner 1975, 1976; Pettit et al. 1976; Zantua et al. 1977; Savant et al. 1985) and a few from waterlogged rice soils (DeLaune and Patrick 1970; Islam and Parsons 1979; Sahrawat 1980), the general principles and concepts of N availability and losses are applicable to N availability in the marsh environment. The ongoing research and the results Approved for publication by the Director of Louisiana Agricultural Experiment Station as Manuscript No. 88-09-2372. 86 reported here will have paramount importance to the revegetation plans for brackish and salt marsh soils. The objective of this investigation was to determine the effect of soil drying, gypsum addition, and electrical conductivity (EC) on soil properties that are related to urease activity. MATERIALS AND METHODS Soil and Sampling Procedures Soil samples were obtained from Clovelly soil series (clayey, montmorillonitic, euic, thermic Terric Medisaprists) at a depth of 0-25 cm from an open area presently inundated by brackish water located at Black Ridge, Hackberry, LA Eight composite samples were taken at intervals covering a total area of 0.40 ha. Each sample was mixed, divided into three subsamples and stored at 10-15 °C until the different treatments were applied. Soil Amendments and Treatments To evaluate the effects of soil drying, gypsum additions, and salinity on soil properties that are related to urease activity, three experiments were conducted (Table 1). Experiment I The purpose of the first experiment was to determine the effect of drying on urease activity. Triplicate 5-g samples were treated with 5 ml of 2,000 mg/L urea solution and incubated at 30 °C for 5 hours. These samples were analyzed for urease activity following the procedure outlined by Tabatabai (1982). The soil was extracted with 50 ml of 2 M KC1-PMA (Phenylmercuric acid) solution as a urease inhibitor. The unhydrolyzed urea recovered in the KC1-PMA extract was determined colorimetrically. The amount of hydrolyzed urea was calculated as the difference between the urea added and the urea remaining. The effect of soil drying on some soil properties related to urease activity was also determined. Triplicate 5-g samples of the two air-dried soil samples and one undried soil sample were analyzed to determine soil pH, EC, and water-soluble cations. An automatic soil extraction apparatus was Table 1. Experimental variables and treatments. Experiment Treatments Incubation conditions and urea addition I. Soil drying None - DO Air drying (1.5 months) - D1.5 Air drying (3.0 months) - D3.0 II. Gypsum additions 0, 5, 10, 20 mg/ha III. Salinity level 0.1, 0.4, 0.8, 1.6 S/m (1:1 NaCl-CaC12 mixtures 30 °C, 2000 mg/kg urea 30 °C, 2000 mg/kg urea 30 °C, 2000 mg/kg urea 30 °C saturated, 10 days, 2000 mg/ha urea 30 °C, saturated, 10 days, 2000 mg/ha urea 87 used to extract the water-soluble cations. Concentrations of these cations were analyzed by using an inductively coupled plasma spectrophotometer. Experiment II The objective of Experiment II was to determine the effect of gypsum additions on urease activity. Triplicate 5-g samples of saturated soil were treated with four rates of gypsum (0, 5, 10, 20 mg/ha) and incubated at 30 °C for 10 days. After incubation, the samples were treated with 2000 mg/L of urea solution. Urease activity of the soil was determined by following the same procedures used in Experiment I. Experiment III The purpose of Experiment III was to determine the effect of different levels of EC on urease activity. Saturated samples were split into 12 subsamples and EC was adjusted to 0.1, 0.4, 0.8, and 16 S/m by adding artificially salinized water that contained 1:1 NaCl-CaCl mixture, and incubated at 30 °C for 10 days. An application of 2,000 mg/L urea was added to each soil. Urease activity was determined following the procedures outlined in Experiment I. RESULTS AND DISCUSSION Soil and Water Analyses Some properties of the representative soil profile are given in Table 2. Surface soils (Oal + Oa2) or the organic horizons have a pH of 6.50 to 6.62; OC ranged from 20.23% to 33.72%; and EC ranged from 0.21 to 0.36 S/m. A general increase in the concentration of water-soluble cations was observed with depth. A water sample from the study area had a pH of 6.8, EC of 0.7 S/m, 0.49 mg/L Fe, 897 mg/L Na, 189 mg/L Mg, 85 mg/L Ca, and 145 mg/L S. Urease Activity and Soil Related Properties Urease activity of brackish marsh soil as affected by soil drying is given in Figure 1. A significantly higher rate of urease activity was observed in the samples dried for 1.5 months, the Table 2. Selected soil chemical properties of undried soils. Hori- Depth OC EC Concentration in mg/kg zon (cm) PH % (S/m) Fe* Mn Mg ; Na S Oal 0-10 6.6 20.2 0.2 0.6 0.02 8.3 66.6 9.4 Oa2 10-25 6.5 33.7 0.4 0.4 0.04 10.5 99.5 7.2 A 25-35 6.7 5.2 0.3 38.5 0.20 16.7 73.2 4.5 Cgl 35-60 7.0 2.5 0.2 56.2 0.20 21.1 67.9 4.5 Cg2 60 + 7.4 1.2 0.2 13.7 0.30 7.3 7.0 4.3 * Water soluble. 88 3.2 2.8H h X Von. J 2.0 £l.6 > ul.2 UJ 20.8H 0.4 0.0 1.40 0 1.5 3. 0 DRYING PERIOD (months) Figure 1. Effect of soil drying on urease activity. lowest for the samples dried for 3 months, and an intermediate rate for the undried samples. With an extended drying period, many changes occur in the soil system. Ponnamperuma (1972) and DeLaune et al. (1976) showed that there was a significant increase of oxygen flux within the interstitial lattice during the development of aerobic conditions. This result would have occurred immediately with drying when the moisture was drastically lowered from 437% (undried) to 21% (3 months) (Table 3). It would appear, however, that aerobiosis as a result of soil drying in brackish marsh soils did not favor urease activity. At the low moisture level of 21%, the lack of free water in the soil apparently limited the contact between urea and soil urease while at the higher water content of 437%, urea hydrolysis is reportedly less dependent on soil moisture (DeLaune and Patrick 1970; Vlek and Carter 1983). Reports on the effects of soil submergence and air drying on urease activity are divergent for wetland soil system. The actual processes are not completely understood. Zantua and Bremner (1977) found that air drying of field-moist soils had no effect on urease activity. Bremner and Mulvaney (1978) noted that there was a difficulty in accounting for the effect of water content on urease activity in soils. Overrein (1963) reported that oxygen had a significant effect on the rate of hydrolysis of urea added to Indian soils. Conversely, Zantua and Bremner (1977) found that oxygen had no effect on the results obtained from the assay of urease activity in Iowa soils. The findings reported here differ from those of Savant et al. (1985), who disclosed that the order of urease activity of the wetland soil system was: oxidized > reduced > flooded. Data on the influence of soil drying on some soil properties measured to evaluate their relationship to urease activity are presented in Figures 2, 3, and 4. The 89 Table 3. Effect of soil drying on some soil and soil related properties of brackish marsh soil. Drying time EC (mo) pH (S/m) MC% Na mg/kg Mn Fe Mg Ca 0.0 1.5 3.0 7.06a 0.4a 437.3a 102.8a 6.24b 1.7b 167.6b 493.4b 6.06c 3.9c 21.4c 853.7c 0.1a 0.6a 13.8a 5.4a 0.2b 1.0b 57.5b 23.4b 0.7c 2.0c 235.6c 99.3c * Means followed by the same letter are not significantly different at p = 0.05. MC = Moisture content. A.5i 4.0- ~3.5- £3. (H 02.5- a O2.0- < 1.5- ujO.5- 0.0 V. a ae A 3.8B 1.88 0 1.5 DRYING PERIOD (months) Figure 2. Effect of soil drying on electrical conductivity. 3.0 90 2.4 2.1 J1.5H Si.« < Ul (_) oO.fr o 0.3^ ao 2.00 a 89 a is YZ2l Iron 1.5 DRYING PERIOD (months) 3.0 Figure 3. Effect of soil drying on Mn and Fe concentrations. EC and the concentrations of water-soluble Na, Mn, Fe, Mg, and Ca increased as the time of soil drying increased. Electrical conductivity increased from 0.39 to 3.88 S/m for an 895% difference between undried soils containing 437% water and soils that were air dried for 3.0 months containing 21% water. The impact of soil drying on the concentration of water-soluble Na, Mn, Fe, Mg, and Ca was noted as an increase of 730%, 1,700%, 245%, 1,606% and 1,736%, respectively, when compared with undried soil. This higher salt concentration resulting from drying brackish marsh soil for 3.0 months could intensify the problem of nutrient toxicity and detrimentally affect native vegetation and revegetation. Although all mechanisms involved are not well understood, the significant reduction of urease activity at the end of a 3.0-month drying can be partially attributed to the behavior of organic and inorganic colloids. Several workers have suggested that the urease in soils is protected by humus or clay colloids (Conrad 1940; McLaren 1963, 1975). Similarly, Pettit et al. (1976) suggested that soil urease is usually immobilized within the organic matter of the organo-mineral complex during humus formation. The organic matter at sufficient moisture has pores large enough to allow the passage of substrate (urea and water) and product (ammonia and carbon dioxide) molecules. If the same soils were subjected to irreversible drying, the pore spaces would be blocked and this would tend to trap urease within the crystal lattices. The escape of the urease itself is then prevented. This blocking mechanism associated with irreversible drying of marsh soils rich in organic matter will partially or totally prevent the contact between the soil colloid and the applied urea, ultimately decreasing the amount of urea hydrolysis. 91 An attempt was made to establish a relationship between the reduction of urease activity and other measured properties in a brackish marsh during long-term drying (Table 4). Variation in the urease activity data (r^=0.74) was best accounted for by the following multiple regression equation: Urease Activity (UA) = 29.64 - 4.598 pH - 0.041 EC + 0.008 MC - 0.002 Na [1] It is noteworthy that soil pH, EC, and Na had significant effects on the level of urease activity. It is likely that high salinity can partially or totally block the mechanism of urea hydrolysis because of increased energy expenditures required for the hydrolysis of urea at increasing ionic strength in the soils (Tanji 1969; Ponnamperuma 1972; DeLaune et al. 1976). Soil EC and soil pH were also significantly affected by soil and soil-related factors. Regression equations developed to explain variation in EC and pH were: EC = 6.234 - 0.016 MC + 0.008 Mg [2] r2 = 0.96 pH = 6.451 - 0.016 EC + 0.001 MC + 0.003 Na - 0.069 Mn - 0.0001 S - 0.039 Fe + 0.003 Mg [3] r2 = 0.89 Table 4. Numerical coefficients (b-values) of soil and soil-related properties in equations and significance of these coefficients. Source b-value Urease Activity (r = 0.74**1 Intercept 29.640 PH -4.598* EC (Electrical Conductivity) -0.041* MC (Moisture Content) 0.008* Na -0.002** Electrical Conductivity (r2 = 0.96**1 Intercept 6.234 MC -0.016** Na 0.008* Mg 0.088** Son pH (r2 = 0.89**) Intercept 6.451 EC -0.016* MC 0.001* Na 0.003* Mn -0.069** S -0.0001* Fe -0.039** Mg 0.003* Significant at p = 0.05 ** Significant at p = 0.01 92 lOOOi 800- X V. 07 J 6001 z o < UJ y 5 u 200- 103 14 6 493 ! % 58 854 Sodium CZZZ3 Magnesium 236 23 JZZL 1 tM» Calcium [XXX] 1.5 DRYING PERIOD (months) 3.0 Figure 4. Effect of soil drying on Na, Mg, and Ca concentrations. Urease Activity and Gypsum Additions Gypsum (CaS04»2H20) is used as a source of soluble Ca for reclaiming sodic soils, preventing soil crusting, and ameliorating water quality (Gobran et al. 1982; Oster, 1982; Gobran and Miyamoto 1985). A favorable positive interactive effect of gypsum and NPK fertilization on saline soils was reported by Rankov (1967). He stressed that gypsum + dung + NPK increased the numbers of ammonifying and nitrifying bacteria and also increased ammonification and nitrification. Similar effects were reported by Carter et al. (1978) on the combined application of ammonium nitrate and gypsum. In the work reported here (Figure 5), gypsum additions did not result in any significant increase of urease activity of soils. Nonetheless, there was a 50% increase in urease activity of soil treated with 20 mg/ha gypsum compared with the control. Earlier findings of Rankov (1967) showed that application of gypsum alone, particularly at the rate of 25 mg/ha, tended initially to decrease the number of nitrifying bacteria and inhibit ammonification and nitrification. Bower (1969) reported that application of gypsum followed by leaching is the most common method to replace adsorbed Na. Leaching with successive dilutions of highly saline water having 30% or more Ca + Mg salts is an effective means of removing adsorbed Na while maintaining soil permeability. 93 Urease Activity and Electrical Conductivity Changes in urease activity in response to different salinity levels is shown in Figure 6. The highest urease activity of 0.82 mg/kg/hr was obtained from the sample at salinity level of 0.1 S/m and the least was observed at salinity level of 0.8 S/m with a mean of 0.53 mg/kg/hr. It is likely that high salinity can partially or totally block the mechanism of urea hydrolysis because of the increased energy expenditures required for the hydrolysis of urea to ammonium-urea as expected from the increasing ionic strength of the soils (Tanji 1969; Ponnamperuma 1972; DeLaune et al. 1976). It should be recalled that urease activity is negatively related to the increasing concentration of Na (Equation 1). Because of the increased Na and other salt components, it is concluded that these soils have established protective mechanisms that lead to the destruction or inactivation of enzymes (Zantua and Bremner 1975; Zantua and Bremner 1976; Zantua et al. 1977). This depressing effect of increasing levels of EC on urease activity is in agreement with the work of Sankhanyan and Shukla (1976) and Myers and McGarity (1968), who found that the rate of hydrolysis of urea was slower in soil samples with high EC. SUMMARY AND CONCLUSIONS The results are summarized as follows: 1. Na, Fe, Mg, and Ca toxicity may develop during long-term drying and detrimentally affect native vegetation and revegetation establishment. 2. Addition of gypsum did not result in a significant increase of urease activity in dried soils. 3. General reduction of urease activity was observed as EC increased. These results reaffirm the importance of N fertilization and water management for the restoration of suitable marsh vegetation. Because N transformation decreased with increasing salinity and because of the probable increase of N losses via denitrification during soil drying, N fertilization should be included in the revegetation plans for brackish and saline marsh soils. In an open area like the marsh where there are few growing plants, the fate of fertilizer N added to the soil as urea is likely controlled by soil urease. Therefore, draining and drying the soil to a maximum (20% MC) should not be practiced because of the reduced urease activity that may eventually lead to lower N availability and fertilizer efficiency. Soil drying also altered the physicochemical properties which were found to be detrimental to the overall productivity of the area. 94 0.7 otO.6- en 30.5] £o.4 > o0.3^ < UJ <£0. 2r i±j S =>0. H 0.0 a ae a 53 0.50 a 87 0 5 10 20 GYPSUM LEVEL (Mg/ha) Figure 5. Effect of gypsum addition of urease activity of brackish marsh soil. \ en ~o.&| ^0.4 < UJ to uj0.2 a: 0.Q a 82 0.1 0.77 a 5e a 53 0. 4 0. 8 SALINITY LEVEL (S/m) Figure 6. Effect of salinity on urease activity of brackish marsh soil. 95 LITERATURE CITED Bower, C.A. 1969. Origin, properties and amelioration of sodic soils. Agrokem. Tanji 69-72. Bremner, J.M., and R.L. Mulvaney. 1978. Urease activity in soils. Pages 149-1% in R.G. Burns, ed. Soil enzymes. Academic Press, London. Broome, S.W., W.W. Woodhouse, and E.D. Seneca. 1975. The relationship of mineral nutrients to growth of Spartina altemiflora in North Carolina. II. The effects of N, P, and fertilizers. Soil Sci. Soc. Am. Proc. 39:301-307. Carter, M.R., R.R. Cairns, and G.R. Webster. 1978. Surface application of gypsum and ammonium nitrate for amelioration of a black solonetz soil. Can. J. Soil Sci. 58:279-282. Conrad, J.P. 1940. Hydrolysis of urea in soils by thermo-labile catalysis. Soil Sci. 49:119-134. DeLaune, R.D., and W.H. Patrick. 1970. Urea conversion to ammonia in waterlogged soils. Soil Sci. Soc. Am. Proc. 34:603-607. DeLaune, R.D., W.H. Patrick, and J.M. Brannon. 1976. Nutrient transformations in Louisiana salt marsh soils. Louisiana State University, Center for Wetland Resources, Baton Rouge. 38 pp. Gobran, G.R., and S. Miyamoto. 1985. Dissolution rate of gypsum in aqueous salt solutions. Soil Sci. 140:89-93. Gobran, G.R., J.E. Duffy, and H. Laudelout. 1982. The use of gypsum for preventing soil sodification: effect of gypsum particle size and location in the profile. J. Soil Sci. 33:309-316. Islam, M.S., and J.W. Parsons. 1979. Mineralization of urea derivatives in anaerobic soils. Plant Soil 51:319-330. Louisiana Department of Natural Resources. 1986. Coastal use permit program bulletin. Coastal Manage. Div., Private Project Devel. Mclaren, A.D. 1963. Enzyme activity in soils sterilized by ionizing radiation and some comments on microenvironments in nature. Recent Prog. Microbiol. 8:221-229. Mclaren, A.D. 1975. Soil as a system of humus and clay immobilized enzymes. Chem. Scri. 8:97- 98. Mendelssohn, LA. 1979. The influence of nitrogen level, form, and application method on the growth responses of S. altemiflora in North Carolina. Estuaries 2(2):106-112. Myers, M.G., and J. W. McGarity. 1968. The urease activity in profiles of five great soil groups from northern New South Wales. Plant Soil 28:25-37. Oster, J.D. 1982. Gypsum dissolution usage in irrigated agriculture: a review. Fert. Res. 3:78-89. Overrein, L.N. 1963. The chemistry of urea nitrogen transformations in soils. Pages 197-200 in R.G. Burns, ed. Soil enzymes. Academic Press, London. Patrick, W.H., and R.D. DeLaune. 1976. Nitrogen and phosphorus utilization by S. altemiflora in a salt marsh in Barataria Bay, Louisiana. Estuarine Coastal Mar. Sci. 4:59-64. Pettit, N.M., A.R. Smith, R.J. Friedman, and R.G. Burns. 1976. Soil urease: activity, stability and kinetic properties. Soil Biol. Biochem. 8:479-484. Ponnamperuma, F.N. 1972. The chemistry of submerged soils. Adv. Agron. 24:29-96. Rankov, V. 1967. Effect of gypsum and fertilizer on microflora of saline soils. Pushkarov. 8:203- 212. Sahrawat, K.L. 1980. Urease activity in tropical rice soils and floodwater. Soil Biol. Biochem. 12:195-1%. % Sankhanyan, S.D., and U.C. Shukla. 1976. Rates of urea hydrolysis in five soils of India. Geoderma 16:171178. Savant, N.K., AF. James, and G.H. McClellan. 1985. Effect of soil submergence on urea hydrolysis. Soil Sci. 140:81-90. Smart, R.M., and J.N. Barko. 1980. Nitrogen nutrition and salinity tolerance of D. spicata and S. altemiflora. Ecology 61(13):630-638. Stojanovic, B.J. 1959. Hydrolysis of urea in soil as affected by season and by added urease. Soil Sci. 88:251-255. Tabatabai, M.A 1982. Soil enzymes. Pages 903-947 in A.L. Page, ed. Methods of soil analyses. Part 2. Agronomy 9. 2nd ed. Am. Soc. of Agron., Madison, Wise. Tanji, K.K. 1969. Solubility of gypsum in aqueous electrolytes as affected by ion association and ionic strengths up to 0.15 M at 25 °C. Environ. Sci. Technol. 3:656-661. Vlek, P.L., and M.F. Carter. 1983. The effect of soil environment and fertilizer modification on the rate of urea hydrolysis. Soil Sci. 136:56-63. Zantua, M.I., and J.M. Bremner. 1975. Preservation of soil samples for assay of urease activity. Soil Biol. Biochem. 7:291-295. Zantua, M.I., and J.M. Bremner. 1976. Production and persistence of urease activity in soils. Soil Biol. Biochem. 8:369-374. Zantua, M.I., and J.M. Bremner. 1977. Stability of urease in soils. Soil Biol. Biochem. 9:135-140. Zantua, M.I., L.C. Dumenil, and J.M. Bremner. 1977. Relationships between soil urease activity and other soil properties. Soil Sci. Soc. Am. J. 41:350-352. 97 RESEARCH AND POLICY ISSUES REGARDING COASTAL WETLAND IMPOUNDMENTS: LESSONS LEARNED IN SOUTH CAROLINA M. Richard DeVoe and Douglas S. Baughman South Carolina Sea Grant Consortium 287 Meeting Street Charleston, SC 29401 ABSTRACT More than 140,000 acres along South Carolina's coastal rivers and tidal creeks were impounded for rice production during the early 1800's; 70,000 of the State's 504,000 acres of contiguous wetlands remain impounded today. Because of heightened awareness of the inherent productivity of these systems for waterfowl habitat and aquaculture, a number of property owners have sub- mitted permit applications to State and Federal regulatory agencies to re-impound formerly impounded areas. (The impoundment of undisturbed wetlands is not allowed in South Carolina.) These applications have generated a number of questions, some of which are still being debated, regarding the ecology, management, and public policy of coastal impoundments, and wetlands in general. A lack of information needed to address these issues has exacerbated the controversy and prolonged debate. As a result, opinions concerning the effects impoundments have on wetland processes have differed between wildlife and marine biologists. This dichotomy is especially evident within several of the 13 agencies which play a role in the decision-making process. Additionally, inconsistent decision-making has contributed to the dilemma. Whereas several public entities have been granted permission recently to reconstruct impoundments on public lands, no private land- holder has yet to receive similar consideration. Recent Supreme Court decisions on the rights of private property owners may affect this situation. Of course, politics and economics play an extremely important role in the process. These and other issues have underscored the need for credible and focused research data and information on one hand and a fair, consistent, and un- biased regulatory framework on the other. These issues are not unique to South Carolina; indeed, similar situations exist in Maryland, North Carolina, Georgia, Florida, Louisiana, and California. INTRODUCTION The State of South Carolina is blessed with over 504,000 acres of coastal, contiguous wetlands. This represents more than 20% of the total coastal marsh acreage on the East Coast and 11% of the remaining acreage in the United States (Tiner 1977; Office of Technology Assessment 1984). A significant portion of these wetland areas are or at one time were impounded for a variety of uses. Today, approximately 70,400 acres, or 14%, of the State's half-million acres are currently impounded (Tiner 1977). Additionally, another 74,000 acres of coastal marsh are estimated to have once been impounded (South Carolina Coastal Council 1984). The existence of impounded wetland sites in South Carolina can be traced back to the days of rice culture, an industry that flourished from the mid-1700's to the late 1800's. Rice was first grown on upland sites, but planters soon realized that irrigated lands could contribute to healthier and more productive crops. Through experience and experimentation, the natural flooding and draining cycle of the tides was recognized by growers as a means to enhance rice field irrigation. The onset of tidal culture led to a doubling of worker productivity and, by the beginning of the 19th century, 98 tidal rice field systems dominated the rice culture industry (Heyward 1937). Creating rice fields was not easy; clearing bottomland hardwood forests, constructing dikes, installing water control devices, and leveling the beds required a great amount of labor and time. Slaves did much of the work. The plantations of South Carolina led the Nation in the production of rice by the mid-1800's (Rogers 1970). As the value of rice increased, so did the value of the lands. The Lord Proprietors (the Crown) granted tidelands to many individuals, often on request, for rice culture. These land transfers are referred to today as "King's Grants." However, because of disagreements over payments and changes in policies, many conflicts erupted. Changes in the land policies of the Royal Government in the early 1700's led to "a rush to grab potential rice lands at the periphery of settlement" (Weir 1983). This expansion occurred so quickly that "those who wanted additional rice land in South Carolina by the mid-eighteenth century almost had to buy, inherit, or marry it" (Weir 1983). By the mid-1800's, most rice lands were in private hands. The rice culture industry remained strong up until the 1850's; the Civil War did much to bring about its demise. The loss of cheap slave labor, several crop failures, and a series of catastrophic natural events contributed to its decline, and by 1920 the industry was essentially dead. However, the impoundments themselves were not ignored. Increasing interest in impoundments for their wildlife and waterfowl values came primarily from rich "Yankees" who acquired these plantation lands and converted them for their "gentlemanly sports," primarily duck hunting. By 1931, very few plantations were still in the hands of native South Carolinians (Rogers 1970). South Carolina impoundments are valued today for hunting, public management (for both conservation and game management), and to a lesser extent aquaculture. Corporate owners of impoundments are primarily involved in two activities-timber production (in old impoundment fields) and aesthetically pleasing development (Tompkins 1986). Of the 70,400 acres of existing impoundments, approximately 31% are publicly owned and managed-25% by the State of South Carolina and 6% by the U.S. Government. The remaining 69% are in the hands of private landowners, where it is estimated that 75% of this acreage is managed to attract waterfowl (T. Strange, S.C. Wildlife and Marine Resources Department; pers. comm.). THE IMPOUNDMENT ISSUES Interest in impoundment systems has increased over the last 20 years in South Carolina, primarily for waterfowl hunting and conservation. Additionally, a number of impoundment owners have become interested in including aquaculture as a management goal. This surge in interest resulted in some 20 permit applications for the re-impoundment for waterfowl of over 3,000 acres of formerly impounded areas between 1967 and 1981. In each of these cases, the application was either denied or withdrawn. Even so, more than one dozen applications for reimpoundment and/or repair activities have been submitted to the State for consideration since 1981. These recent applications created a serious controversy in South Carolina, focusing on the relative benefits and detriments of impounded wetlands versus open tidal wetlands. The debate generated a number of arguments for and against re-impoundment and repair activities. OPPOSITION TO IMPOUNDMENT ACTIVITIES Many points have been raised against these proposals by natural resource agencies, public interest groups, and the informed public. We identified the following issues by reviewing the 99 many records and documents generated during a series of public hearings, administrative appeals, and court proceedings resulting from several major cases over the last 5 years. Effects on Wetland Functions Concerns were expressed about the effects of impoundment activities on basic wetland functions. Specifically, opponents suggested that impoundments would reduce tidal exchange; the exchange of tidal waters would be greatly reduced and would occur only when the impoundments were drained and flooded (usually in the spring in South Carolina brackish water waterfowl impoundments). This would greatly diminish the natural import and export of nutrients and biomass. Also, arguments were raised that access to nursery habitats by aquatic organisms would be limited (the value of fishery habitat being great in open wetlands). Impoundments would restrict or prohibit use by estuarine-dependent fish and crustaceans of the wetland habitat contained within the dikes. And finally, critics suggested that marsh productivity would be diminished and that tidal wetlands are significantly more productive than impounded wetlands (using Spartina productivity as a measure). Impoundments would prevent the export of Spartina detritus produced within their dikes. Effects on Water Quality Questions were also raised by opponents regarding water quality. One concern expressed by several groups was the potential for the formation and possible export of acidic waters due to "cat clays" (oxidized soils) during periods when impoundment beds are dewatered. In South Carolina, impoundment waters are usually drained in the spring and, depending on the management strategy employed, the beds may be exposed to the atmosphere for 3 to 4 months. Oxygen from the air may react with the highly sulfuric composition of the soils, producing acidic conditions. Also, impoundments concentrate waterfowl (and other avifauna), which are known to release large amounts of nutrient-laden feces. High nutrient levels could result, some suggested, in algal blooms and the subsequent depletion of oxygen in impoundment waters. Complicating this problem would be the high levels of fecal coliform bacteria that would result. Others pointed to the probable reduction of the filtering capacity of open wetlands. Navigation Other issues raised by re-impoundment opponents included the impact of impoundments on navigable waterways, which are subject to the navigational servitude of the United States and the State of South Carolina. Several agencies contended that tidal creeks cut off by impoundments violate this servitude. In fact, in a recent decision by the South Carolina Supreme Court (Opinion No. 22602, filed July 28, 1986), the Court ruled that the "South Carolina Coastal Council does not have the authority to authorize the complete blockage of navigable streams and waterways" in this case, for the purpose of constructing impoundment dikes. Public Access Impoundments would limit public access to a "public resource" according to public interest groups. The public would be cut off from all wetlands targeted for re-impoundment. The "Precedent" A major argument of involved regulatory agencies was that "if we allow one, we'll have to allow them all." This might indeed have been the case because there were no established criteria available for use in evaluating applications for re-impoundment or repair activities. 100 Tidelands Ownership Finally, the question of ownership of the resource was an issue: who owns the land below the mean high water mark? In South Carolina, the State owns all tidelands below the mean high water mark in trust for its citizens. However, as mentioned, thousands of acres of these lands were granted or sold to private interests by the Crown and the State. Ownership of a sizeable number of these properties is in question today. The standard used to determine ownership has been the "unbroken chain of title" rule; that is, if landowners demonstrated to the South Carolina Attorney General's Office that they have in possession a deed or title to the tidelands traceable back to the original grant of land, including a clearly marked plat or map, then the tidelands in question would belong to the landowners. (The State Supreme Court recently determined that the "unbroken chain" rule was too restrictive, and that private ownership can be proved without necessarily demonstrating an unbroken chain of title.) In addition, ownership per se was not considered by some opponents as germane to the real issues of impounding wetlands. SUPPORT OF IMPOUNDMENT ACnVITIES On the other hand, proponents of impoundments have pointed to arguments in support of re- impoundment activities on formerly impounded wetlands. Private Property Rights Impoundment owners (and managers) continue to argue that if they can prove ownership to impounded and formerly impounded lands on their property, any reasonable use of the lands should not require government approval, at any level. In their opinion, deprivation of these rights would constitute a "taking," and require compensation. Federal Intervention In each of three recent major re-impoundment cases, the State and the U.S. Army Corps of Engineers decided to issue their respective permits after lengthy debate; these permits usually contained a significant number of conditions. In each case, the U.S. Environmental Protection Agency (USEPA) has intervened, under Section 404 of the Federal Water Pollution Control Act, as amended, to seek revocation of the Federal permits (with some success). Several of the property owners involved in these cases remain furious: in one case, an applicant has described these actions as "socialistic" and "communistic." Wildlife Benefits Of course, proponents argued that many wildlife benefits result from impoundments. Impoundments provide ideal habitat for a wide range of waterbirds, they suggested, and also serve as important habitat for eagles, ospreys, alligators, and other threatened and endangered species. Inconsistent State and Federal Policies Impoundment owners pointed to the many inconsistencies in State and Federal government policies regarding impoundments (described in more detail below). THE NEED FOR INFORMATION These arguments surfaced as strong issues in the early 1980's even though little technical information was available to either substantiate or disprove them. The need for an improved 101 understanding of impoundment systems in South Carolina emerged in three basic areas: (1) impoundment ecology; (2) State and Federal impoundment policies and regulations; and (3) impoundment management as practiced throughout the State. The South Carolina Sea Grant Consortium, with funding provided by the National Sea Grant College Program, NOAA (U.S. Department of Commerce), initiated a multi-disciplinary study in September 1982 to examine these issues and gather baseline data on impoundment systems. A major goal of the Coastal Wetland Impoundment Project (CWIP) was to provide information useful to decision-makers, impoundment managers, and the informed public in resolving the impoundment debate in South Carolina. The results of the CWIP have been published in a three- volume document (DeVoe and Baughman 1986a; 1986b; 1986c). PERSPECTIVES ON THE IMPOUNDMENT ISSUE IN SOUTH CAROLINA Instead of reviewing the details of the CWIP, let us instead offer several perspectives on how the impoundment issue has manifested itself in South Carolina. These thoughts may not be new to you, but they do reflect the controversial nature of the impoundment issue in South Carolina. We would first like to quote a phrase from the Findings-of-Fact of the Administrative Hearing Officer in his 1982 summary of the issues presented before the South Carolina Coastal Council in an appeal of a State permit for the impoundment of 660 acres of salt marsh: "Opinions concerning the impacts of the impoundment on the Santee Delta varied from expert to expert and in some respects depended upon whether or not the opinion came from a waterfowl biologist or from a marine biologist" (Ellison Smith, pers. comm.). There are several points we want to make here. It is this division of opinion among scientists and the lack of a clearcut technical answer that impoundments are "good, bad or indifferent" ecologically that has, in the eyes of policymakers, affected the credibility of the scientific community and the potential contribution that scientists can make to resolving the issues. Further, policy- and decision-makers live with and accept a degree of uncertainty in their actions; however, they demand a level of assurance from scientists that science cannot always deliver. This exacerbates the credibility issue. And finally, in the case of the CWIP, project results support scientists and others on both sides of the issue in South Carolina. Yes, managed wetlands are great for waterfowl, other waterbirds, and several endangered species, but at the same time can be detrimental to many marine and aquatic species. Thus, the CWIP has scientifically documented many of the points made for and against impoundments. The issue boils down to a resource management question: what does the State of South Carolina want to do with its impoundment resources, both functional and remnant? Secondly, interest by landowners to seek permits for impoundment construction activities has created pressures on State and Federal natural resource and regulatory agencies. Up to 13 local, State, and Federal agencies can be involved with some aspect of the impoundment issue in South Carolina. Each agency has its own mandate, set of responsibilities, and philosophy. We have found, not suprisingly, that impoundment policies vary significantly from one agency to the next, and in some cases even within individual agencies. An example is the South Carolina Wildlife and Marine Resources Department (SCWMRD). Its Division of Marine Resources is concerned with fisheries and marine habitat and has generally opposed applications for re-impoundment activities, while its Division of Wildlife and Freshwater Fisheries has been quite supportive, due to their value as wildlife habitat. The bottom line is that their respective goals and objectives, and thus their information needs, are different. 102 Third, inconsistent decision-making has contributed to the dilemma. There have been instances where public agencies have been granted permission to reconstruct impoundments on public lands; however, no private property owner has yet to receive similar consideration. One example is the U.S. Fish and Wildlife Service (USFWS) of the U.S. Department of the Interior. The Ecological Services Branch of USFWS in Charleston, SC, has consistently opposed impoundment construction or repair activities in wetlands, while its sister branch at the Cedar Island Wildlife Refuge in North Carolina has proposed to construct impoundments in tidal wetlands for waterfowl management purposes. The message to impoundment owners and managers has been confusing indeed. Fourth, factors other than scientific "fact" must be considered in the decision-making process. These include an assessment of the benefits and costs of the proposed activity (economics), a consideration of what is in the public interest, and, of course, the political process itself, which involves a number of interest groups. And fifth, applicants seeking permits for impoundment activities in South Carolina must work their way through a very complex permitting process that is illustrated in Figure 1. A CASE STUDY FROM SOUTH CAROLINA Several of the points we have made can be illustrated by examining a case study. It involves an application first submitted to the State of South Carolina in 1971 to impound 1,000 acres of salt marsh, most of it formerly impounded, for the attraction of waterfowl and the initiation of an aquacultural operation. In 1981, the application was revised and resubmitted; the wetland area involved was reduced to 660 acres. At the State level, the application was submitted to the South Carolina Coastal Council (SCCC) and sent out for public comment. It was quickly opposed by the State Attorney General's Office on grounds of ownership, by the SCWMRD on the basis of wetland and fisheries impacts, and by a number of concerned citizens' groups for various reasons. Nevertheless, the SCCC approved the application with conditions. This permit action was immediately appealed by the Attorney General's Office, the Sierra Club, the League of Women Voters, and others. After a long hearing and appeals process, the SCCC decided to uphold its initial decision and issue the permit. This was immediately appealed to the State circuit court by the appellants (and ultimately to the State Supreme Court). At the same time, the Charleston District office of the U.S. Army Corps of Engineers (US ACE) handled the application on the Federal level. Recommendations for denial were offered to the USACE by the USFWS, the National Marine Fisheries Service (NOAA), and the USEPA However, the USACE decided to concur with the State decision and issued its "intent to issue" a Federal permit. The USEPA immediately made a request that the decision be elevated to the USACE's Washington office, which was rejected by the Charleston District. The USEPA then invoked Section 404(c) of the Federal Water Pollution Control Act, as amended, which provides the USEPA Administrator with the authority to prohibit dredge and fill activities if "the discharge of such materials into such area will have an unacceptable adverse effect on municipal water supplies, shellfish beds and fishery areas (including spawning and breeding areas), wildlife, or recreational areas." However, before the USEPA Administrator could finalize his decision, the South Carolina Supreme Court ruled on the appeal of the State permit. In essence, the court ruled that the 103 Site of Proposed Impoundment Activities EXISTING IMPOUNDMENT | FORMERLY IMPOUNDED AREAS | NATURAL WETLANDS X J OwnorLeaseArea YES NO Own Formerly Impounded Area YES NO Obtain Owners Consent Not Permitted Verification by State (8) S.C Attorney General's Office I No Construction Activities Allowed Areaof Impoundment Reconstruction IN CRITICAL AREA I OUTSIDE CRITICAL AREA Critical Area Permit <2a> SC Coastal Council Construction Permit for Navigable Waters @A) S.C. State Budget & Control Board Crossdiking Involved YES T J Section 10 & Section 404 Permit U.S. Army Corps of Engineers c Section 404 Permit U.S. Army Corps of Engineers I Letter of Approval2 S.C. Coastal Council I Construction Permit (6A) S C. Dept Health & Environmental Control NPDES Permit <6B) S.C. Dept. Health & Environmental Control r Type of Stock I GAMEFISH NON-GAMEFISH Gamefish Breeders License (5B) S.C. Div Wildlife & Freshwater Fisheries J L T If applicable — prohibited species can only be imported for research purposes •Although no additional permit is required for this activity because of the issuance of a General Permit, written permission must be obtained from the S C. Coastal Council before crossdiking activities begin Importation of Exotic/Prohibited Species Permit (4F,sa ) S.C Div. Marine Resources and Div. Wildlife & Freshwater Fisheries PRODUCTION Figure 1. Permit structure: impoundments. 104 SCCC does not have the authority to issue permits that completely block navigation in tidal creeks and canals, whether or not the waterways were artificial. Additionally, the court ruled that the activities proposed by the applicant were not in the public interest. Of course, the permit was overturned and the application withdrawn. Several points to note: This process took 14 years to resolve. The applicant spent almost $250,000 of his own money in fees, legal expenses, and other costs during this time. Interestingly, the estimated costs of the proposed activity were only $240,000, somewhat less than the costs actually incurred in attempting to obtain permits. This case represents an unusual situation, but other cases in South Carolina have taken many years and significant sums of money to resolve. One last point: the State Supreme Court decision in this case has essentially diffused the re- impoundment issue in South Carolina. However, we have many impoundments that are in need of repair, which is a different situation, and for which no consistent policies exist. SUMMARY We have presented a brief and somewhat simplified overview of the recent history of the impoundment controversy in South Carolina. The debate was intense and complex; the issues were many and diverse. And the topic warrants more in-depth analysis than that presented in this paper. Nevertheless, we can say in summary that impoundments will continue to be the focus of controversy in South Carolina and in other States (e.g., Maryland, Georgia, Florida, Louisiana) as well. What are needed to resolve extant cases and avoid long, drawn-out and expensive regulatory battles in South Carolina and elsewhere are: (1) Clear, concise, and integrated policies on impoundment construction and repair activities by State and Federal agencies (on a regional basis, at least); (2) A commitment to decision-making consistent with established policies; (3) Adequate awareness of the policies by affected or potentially affected parties; (4) A commitment to the acquisition of credible, unbiased, and focused research data and information to build the information base; and most importantly, (5) OPEN COMMUNICATION among all parties involved. ACKNOWLEDGMENTS We authors would like to thank Dr. J. M. Dean and Dr. M. E. Tompkins (University of South Carolina) and Dr. P.A Sandifer and Dr. R. Van Dolah (S.C Wildlife and Marine Resources Department) for their continuous help, input, and suggestions as the Coastal Wetland Impoundment Project progressed and the results were synthesized. Of course, we must thank all the scientists, graduate students, and technicians who gave their all to make the project a success. Finally, to all the players in the impoundment controversy, we extend our appreciation for sharing with us your insights and thoughts. We thank Monica Mulvey for typing the drafts of this paper. Support for the Coastal Wetland Impoundment Project was provided by the National Sea Grant College Program Office, NOAA U.S. Department of Commerce, under Grant Nos. NA8LAA-D- 00093, NA83AA-D-00057, NA84AA-D-00058, and NA85AA-D-SG121, the South Carolina Sea Grant Consortium, and the State of South Carolina. 105 LITERATURE CITED DeVoe, M.R., and D.S. Baughman, eds. 1986a. South Carolina coastal wetland impoundments: ecological characterization, management, status, and use. Vol. I: Executive summary. Publication No. SC-SG-TR-86-1. South Carolina Sea Grant Consortium, Charleston, SC. 42 pp. DeVoe, M.R., and D.S. Baughman, eds. 1986b. South Carolina coastal wetland impoundments: ecological characterization, management, status, and use. Vol. II: Technical synthesis. Publ. No. SC-SG-TR-86-2. South Carolina Sea Grant Consortium, Charleston. 611 pp. DeVoe, M.R., and D.S. Baughman, eds. 1986c. South Carolina coastal wetland impoundments: ecological characterization, management, status, and use. Vol. Ill: Technical appendix. Publ. No. SC-SG-TR-86-3. South Carolina Sea Grant Consortium, Charleston. 123 pp. DeVoe, M.R., and J.M. Whetstone. 1984 (rev. 1987). An interim guide to aquaculture permitting in South Carolina. Publ. No. SC-SG-TR-84-2. South Carolina Sea Grant Consortium, Charleston. 27 pp. Heyward, D.C. 1937. Seed from Madagascar. University of North Carolina Press, Chapel Hill. Office of Technology Assessment (O.T.A.). 1984. Wetlands: their use and regulation. Publ. No. OTA-0-026. O.T.A., Washington, DC. Rogers, G.C., Jr. 1970. The history of Georgetown County, South Carolina. University of South Carolina Press, Columbia. South Carolina Coastal Council. [1984.] A survey of formally impounded wetlands of South Carolina. Unpubl. MS. Tiner, R.W., Jr. 1977. An inventory of South Carolina's coastal marshes. S.C. Mar. Resour. Center Tech. Rep. No. 23. Tompkins, M.E. 1986. Historical review of South Carolina's impoundments. In M.R. DeVoe and D.S. Baughman, eds. South Carolina coastal wetland impoundments: ecological character- ization, management, status and use. Vol. II: Technical synthesis. Publ. No. SC-SG-TR-86- 2. South Carolina Sea Grant Consortium, Charleston. U.S. Congress. 1977. The Clean Water Act, as amended. U.S. Government Printing Office, Washington, DC. Weir, R.M. 1983. Colonial South Carolina, a history. KTO Press, Columbia, SC. 106 REGULATORY PROCEDURES IMPACT LANDOWNERS' MANAGEMENT PROGRAMS Allan B. Ensminger Wetlands and Wildlife Management Company P.O. Box 158 Belle Chasse, LA 70037 ABSTRACT The passage of various Federal and State environmental protection laws requiring prior permit approval for activities has imposed management burdens upon many wetland owners and managers. Less than 10% of the Louisiana coastal wetlands are included in approved Marsh Management Plans or in plans that have been applied for. The small percentage of wetlands involved in approved plans is not an accurate tabulation of the amount of acreage that is being managed in the coastal marshes. Many programs of open marsh water level management are not listed because the programs were in place before passage of regulatory requirements for intensive marsh management. Because of regulatory requirements, some landowners are reluctant to apply for or accept Marsh Management Plans. Landowners object to the requirement of ingress and egress for marine organisms because this requirement does not lend itself to water level management needed for other natural resource habitat production. Increased monitoring requirements imposed in permits cause landowners to be faced with employment of consultants or full time personnel to monitor permit compliance. Some aspects of this monitoring may be more academic in scope than necessary for successful management benefits. On-site structural mitigation is being denied landowners who do not have approved Marsh Management Plans. This decision is based upon the assumption that landowners and their managers can not be trusted to properly manage their ownership or is based upon the desire to impose the goals of the regulatory agencies upon private landowners. INTRODUCTION The history of coastal wetland management of Louisiana dates back to the first colonial settlements along the numerous bayous and waterways of the State. Early settlers used these waterways as avenues of access into the interior of the State. Extensive use was also made of the natural levee systems along almost every bayou and stream. Early use of the wetlands was in the form of subsistence hunting and fishing. Farming on the elevated terraces and ridges was a mainstay of the early settlers. Cattle grazing was also allowed on the back side of the natural levee systems. Access into the interior of the wetlands was limited to natural streams, and a few handmade ditches accommodated small water craft such as pirogues and canoes. As use of the coastal zone intensified, extensive navigational canals were constructed to transport products such 107 as sugar, cotton, and timber to major water ports along the gulf coast. Sections of the Gulf Intracoastal Waterway developed from these early transportation arteries as they expanded and were used in more recent eras. Natural production of fish and wildlife resources has been a major attraction for generations of humans along the coast. Numerous midden sites attest to this attraction for early Indian inhabitants of the coast. Fish scales, clam shells, and animal bones and teeth indicate a high degree of use of the ecosystem's natural resources. Extensive private land purchases of the Louisiana coastal wetlands were made during the first quarter of this century. Some of these purchases were for developing farming ventures, but many of the acquisitions were to harvest the abundant supply of wild furbearing animals. Commercial harvest of migratory waterfowl may have been one of the first applied influences of wetland management. A dependable supply of ducks was required to make this type of employment worthwhile. Water level management and access ditches were the mainstay of the early management projects. Impoundments to attract large concentrations of ducks were the outgrowth of rice culture activities in southwest Louisiana. Water deficiencies throughout much of the central portion of the continent during the early 1930's played an important role in the concept of constructing large reservoirs to provide habitat for waterfowl. Most early fur management programs were little more than the annual harvest of as many animals as possible during seasons established by the Louisiana Department of Conservation, the forerunner of the present day Louisiana Department of Wildlife and Fisheries. As cycles of muskrat became more common, many trappers and land managers introduced the practice of draining their "eatouts" by cutting ditches into a nearby bayou or waterway. Little information with regard to the danger of saltwater intrusion and impounding was available or understood. DISCUSSION Few, if any, of the early marsh management practices carried out on private and public properties required specific permits, unless their features would have an impact upon navigation in a public waterway. The following excerpt from the U.S. Army Corps of Engineers pamphlet EP 1145-2-1, May 1985, (Wall 1985) may be of assistance in understanding the authority for the regulatory program. The U.S. Army Corps of Engineers has been regulating activities in the nation's waters since 1890. Until the 1960's the primary purpose of the regulatory program was to protect navigation. Since then, as a result of laws and court decisions, the program has been broadened so that it now considers the full public interest for both the protection and utilization of water resources. The regulatory authorities and responsibilities of the Corps of Engineers are based on the following laws: Section 10 of the Rivers and Harbors Act of 1899 (33 U.S.C. 403) prohibits the obstruction or alteration of navigable waters of the United States without a permit from the Corps of Engineers. 108 Section 404 of the Clean Water Act (33 U.S.C. 1344). This Act prohibits the discharge of dredged or fill material into waters of the United States without a permit from the Corps of Engineers. Section 103 of the Marine Protection, Research and Sanctuaries Act of 1972, as amended (33 U.S.C, 1413), authorizes the Corps of Engineers to issue permits for the transportation of dredged material for the purpose of dumping into the ocean waters. Other laws may also affect the processing of applications for Corps of Engineers permits. Among these are the National Environmental Policy Act, the Coastal Zone Management Act, the Fish and Wildlife Coordination Act, the Endangered Species Act, the National Historic Preservation Act, the Deepwater Port Act, the Federal Power Act, the Marine Mammal Protection Act, the Wild and Scenic Rivers Act, and the National Fishing Enhancement Act of 1984. In addition to the authority of the Corps of Engineers to regulate activities in the wetlands, the Louisiana State and Local Coastal Resources Management Act of 1978 initiated a major effort to develop a coastal management program under Section 305 of the Coastal Zone Management Act. It is doubtful that any marsh landowner has ever read all of the Federal and State statutory acts with regard to regulation of wetlands. It is also doubtful that the landowner understands the provisions, conditions, and implications of the acts or the rules and regulations developed to administer them. The complex nature of application and receipt of a Coastal Use Permit and a Section 404 Permit has led to a situation of extreme frustration on the part of landowners, both large and small. Current publicity presents land loss as a condition that has just been discovered within the past decade, but for an extensive period of time landowners recognized land loss in coastal Louisiana. Coastal land loss has been referred to by a large number of wildlife researchers and land managers. Comparison of early marsh investigations by O'Neil (1949) and investigations carried out by researchers of the Louisiana Department of Wildlife and Fisheries (Chabreck et al. 1968) graphically record the loss. The comparison led to the publication of a vegetative type map of the coast that was updated in 1978. Field data collected in 1987 are in the final stages of interpretation and will soon be published. Before passage of the various regulatory acts, most landowners addressed marsh management problems on a basis of need and the availability of funds to carry out structural projects. Even after passage of the acts, some landowners continued for a time to implement projects without permits because of poor communication between regulatory agencies and the real world, the user. This situation has improved and only on rare occasions are large projects discovered that are not covered by proper permits. Mineral activity in the Louisiana coastal wetlands is an industry of long standing. This industry is accustomed to applying for exploration and production permits of oil and gas deposits. In most cases there is a large staff to attend to this administrative chore, and obtaining coastal use permits is just another layer of bureaucratic paper work. Private or public land mineral leases are held by companies that do not own the surface of the property. Requirements injected into and made a part of permits issued for access to remote exploration sites are of little consequence to the mineral operator as long as these requirements are economically within reason. Most mineral leases are of long primary terms and landowners have not understood the need to incorporate extensive environmental provisions into the terms and conditions of the original leases. 109 This combination of conditions has led to trial and error regulatory demands becoming part of oil and gas operation permits on private as well as public lands. A noted demand was the requirement for gaps in the spoil banks along canals excavated for access to drilling sites in order to provide ingress and egress of marine organisms. This disastrous requirement led to accelerated saltwater intrusion into many marsh areas and also destroyed some established marsh management projects for waterfowl and fur-bearing-animal food production. This practice shocked landowners and managers into reality. For many, it was the first time they recognized their rights as landowners had been impacted by State and Federal regulations. The practice of gaps in spoil banks has been addressed and is now a requirement only on rare occasions, except for back of a plug at the mouth of a canal. Other undesirable requirements are being recommended as conditions for permits to be issued. Some of these requirements include spraying spoil dredged from access canals into the marsh, and trying to backfill unused canals with the spoil excavated during original construction. In recent Marsh Management Plan permits, requirements for extensive monitoring have been included. Environmental conditions for the proper management of an area are being expanded to include many information-gathering projects that are of little or no value to the landowner in his effort to restore the marsh or reduce land loss. Fisheries production is one of the many functions of a wetlands area. This production has been relegated to a position of little value to landowners because of their limited authority to harvest the resource produced upon their lands. In some cases, the high yields of fisheries on public properties has swayed the management programs to provide recreational opportunity at the expense of target species of the management program. In the case of private landowners, this has led to vandalism of structures and levees in order to obtain these resources in the most expedient manner. One of the high priority projects of the newly formed North American Waterfowl Management Plan is to restore wintering waterfowl habitat of the Mississippi Delta and Gulf Coast Marshes. This plan is an attempt to return the continental population of waterfowl to a level that will support a fall flight in excess of the 100 million birds experienced during the 1970's. Habitat restoration and management will be a cornerstone of this program and will require coordination of activity on the wintering grounds along the gulf coast. In some prime waterfowl marshes, in my opinion, fisheries resources may have to be relegated to a position of less importance than waterfowl. Another area of great concern to managers and landowners is the extensive time lag between application for a marsh management permit and permit issuance. In almost no case is the final permit issued in less than 1 year and then only after substantial changes in the content and goals of the original plan. Plans being prepared for landowners by the Soil Conservation Service are being subjected to extensive revision in order to reflect goals beyond the needs of the landowner to manage his wetlands. In some cases, these provisions result in landowners' reluctance to accept Coastal Use Permits, and the ecosystem continues to suffer adverse impacts that could be corrected by structural measures. Most small landowners can be encouraged to do some management work on their properties. However, if permission to do the work is delayed for an extensive time period, they lose interest in the project, or funds to carry out the work are no longer available. A policy position developed among regulatory and commenting environmental agencies will not recommend manipulable structures as mitigation on wetlands without an approved marsh management plan. Additional wetlands will be lost without a change in this position or an improvement in the program to make it reasonable to obtain a permit for marsh management. 110 CONCLUSION Regulatory processes need to be adjusted to reflect a position of encouragement for private landowners to manage and protect their wetlands. Environmental management and regulatory agencies need to adopt clear policies for marsh management programs in various types of marsh ecosystems and provide assistance to landowners to accomplish these goals. The long delay between application and issuance of a permit must be addressed in order to maintain landowner support and interest in wetland management and protection. LITERATURE CITED Chabreck, R.H., T.J. Joanen, and A.W. Palmisano. 1968. Vegetative type map of the Louisiana coastal marshes. Louisiana Wildlife and Fisheries Commission, New Orleans, LA O'Neil, T. 1949. The muskrat in the Louisiana coastal marshes. Louisiana Wildlife and Fisheries Commission, New Orleans, LA. 159 pp. Wall, J.E.. 1985. Regulatory program, applicant information. U.S. Army Corps of Engineers, Pamphlet EP 1145-2-1, May 1985. Ill MARSH IMPOUNDMENTS FOR THE MANAGEMENT OF WILDLIFE AND PLANTS IN LOUISIANA Robert H. Chabreck and George M. Junkin School of Forestry, Wildlife and Fisheries Louisiana State University Agricultural Center Baton Rouge, LA 70803 ABSTRACT Marsh impoundments are widely used in coastal regions for improving wildlife habitat, aquaculture, water storage for agricultural irrigation and industrial uses, the flooding of marshes for mosquito control, and the maintenance of favorable water depths for navigation. Impoundments used to improve wildlife habitat can be categorized into four types by water depth and salinity regimes: permanently flooded with freshwater, manipulated freshwater, permanently flooded with brackish water, and manipulated brackish water. Their effects on wildlife and plants vary with the species involved and the type of impoundment. Impoundments have been widely used in Louisiana for waterfowl management. This type of management has been particularly effective in improving marshes for ducks, but habitat for other forms of wildlife is also improved. Marsh impoundments have certain limitations, which at times make it necessary for landowners to use other types of management. First, impoundments are costly to construct and maintain. Also, without facilities for pumping water, years that are unusually wet or dry generally result in poor food production. Impoundments can be built only in areas that will support a continuous levee. In certain areas, such as southeastern Louisiana, impoundment use is limited because of the fluid nature of the subsoil. INTRODUCTION Marshes along the Louisiana coast occupy approximately 985,000 ha and constitute over 40% of the total marsh area of the gulf and Atlantic coasts (Alexander et al. 1986). One-fourth of the waterfowl in North American use the Louisiana coastal region as winter or transient habitat (Hansen and Hudgin 1966). Because of the widespread deterioration of coastal marshes, the rapid inland advancement of saltwater, and the reduction in quality wildlife habitat, marsh management is becoming increasingly important. Impoundments and water management are critical aspects of marsh management and may be necessary to maintain the existing condition of a marsh or to improve the marsh's value as wildlife habitat. The term "impoundment" shall be defined as any area of wetland enclosed by an earthen dike in which various types of water-control structures may be installed for draining or flooding the area (Williams 1987). Marsh impoundments are hydrologically isolated and are widely used in coastal regions for improving wildlife habitat, aquaculture, water storage for agricultural irrigation and industrial uses, flooding marshes for mosquito control, and maintaining favorable water depths for navigation. In this paper, we will deal primarily with impoundments for improving wildlife habitat. 112 Impoundments used to improve wildlife habitat in Louisiana are mainly managed to produce duck foods, provide water depths that make food readily available, and provide appropriate cover that will attract ducks to the impoundment (Chabreck 1960; Yancey 1964; Joanen and Glasgow 1965; Baldwin 1968; Wicker et al. 1983). Such management is less expensive and more effective where water can be exchanged as needed by using free energy such as the tides. Improvement of duck habitats by using impoundments may mitigate the effects of duck habitat loss elsewhere in the region. Types of Impoundments Impoundments used to improve wildlife habitat can be categorized by water depth and salinity regimes into four types: permanently flooded with freshwater, manipulated freshwater, permanently flooded brackish water, and manipulated brackish water (Chabreck 1960). In permanently flooded freshwater impoundments, fluctuation of water depth results from natural causes. Water depth is usually greatest during winter and lowest during the summer because transpiration and evaporation are greatest in the summer (Chabreck 1960). Lacassine Pool, on Lacassine National Wildlife Refuge in southwestern Louisiana, is a premiere example of a permanently flooded freshwater impoundment (Fruge 1974). A manipulated freshwater impoundment has the potential for water level control and for the drainage of the area. A partial drawdown stimulates growth of perennial plants, and a complete drawdown promotes seed germination of annual plants. Manipulated freshwater impoundments in Louisiana usually require pumping to alter the water level; in years with excessive rainfall or drought, even pumping may not be efficient (Chabreck 1960). The potential to drain an area allows for additional management practices such as burning, mowing, disking, or herbicide application. The water depths in permanently flooded brackish impoundments vary considerably and are at their highest level and lowest salinity during the late winter and early spring. As a result of evaporation and transpiration, water depths are lowest in late summer and early fall. Water depths are usually inversely proportional to salinity (Chabreck 1960). Although this impoundment type is described as permanently flooded, drainage at 2- to 3-year intervals is necessary for the best widgeongrass (Ruppia maritima) growth (Chabreck 1960; Morgan et al. 1975). Rainwater, tides, and pumps can be used to change the water level in manipulated brackish impoundments. Salinity increases can be accomplished by increasing the flow of saltwater into the impoundment during high tides. Salinity is decreased in Louisiana usually by dilution with rainwater. Active water management, which involves pumping, is used as a last resort if passive management, tides, and rainfall are ineffective. Permanently Flooded Freshwater Impoundments Plants. Freshwater impoundments promote the growth of desirable submerged and floating- leaved aquatics (Baldwin 1968). Duckweed (Lemna minor) was the dominant species in permanently flooded freshwater impoundments at Rockefeller Refuge in southwest Louisiana. In Lacassine Pool, the most abundant floating-leaved species were watershield (Brasenia schreberi), big floatingheart (Nymphoides aquatica), and white waterlily (Nymphoides odorata), while the most abundant submergents were nitella {Nitella gracilis) and bladderworts (Utricularia sp.) (Table 1). The establishment of watershield in flooded freshwater impoundments improves their value to certain species of ducks (Chabreck 1960). The permanently flooded freshwater impoundments on 113 Table 1. Percentage of occurrence of floating-leaved species in Lacassine Pool, 1974 (data from Fruge 1974). Species Percentage of occurrence Watershield 78.57 American lotus 2.38 White waterlily 45.24 Big floatingheart 76.19 Rockefeller Refuge were dependable duck food producers, although the food produced (other than duckweed) was of low quality (Chabreck 1960). Wildlife. Permanently flooded freshwater impoundments receive high use by waterfowl. Gadwall (Anas strepera) and American wigeon (Anas americana) feed heavily on the leafy plant materials. Diving ducks such as ring necked ducks (Aythya collaris) prefer this habitat type and concentrate there in large numbers. Water depths are often too deep for bottom feeding dabblers. Permanently flooded impoundments are particularly valuable to ducks during prolonged droughts, when most marshes are dry. Rails and gallinules use this impoundment type year round, and wading birds often use this impoundment type if shallow water is available. Nutria (Myocaster coypus) do very well in this habitat type; however, muskrats (Ondatra zibethicus) are limited by the absence of preferred food plants. Excellent feeding conditions and abundant prey species for the alligator occur in habitat provided by permanently flooded impoundments (Chabreck 1960). In Lacassine Pool, 94.6% of the alligator nests were located in the impoundment, as compared to 5.4% on an area of equal size outside the impoundment (Carbonneau 1987). Manipulated Freshwater Impoundments Plants. The most common method of manipulating freshwater marshes includes partial or complete drawdown during the growing season to promote the growth of moist soil annuals (Baldwin 1956; Conrad 1966; Morgan et al. 1975). Wild millet (Echinochloa walteri) is an important food of ducks in Louisiana (Chamberlain 1959; Kimble and Ensminger 1959) and was the dominant species in manipulated freshwater impoundments at Rockefeller Refuge (Table 2). Important duck-food plants constitute 87.5% of the impoundment vegetation and 50.7% of the plants in the control area. In a floating freshwater marsh impoundment in southcentral Louisiana, the major species were pennywort (Hydrocotyla sp.), spikerush (Eleocharis sp.), and paspalum (Paspalum sp.), while water hyacinth (Eichhomia crassipes) and spikerush were the major species within the control area (Carney and Chabreck 1977). The impounded area contained 24.4% more duck-food plants than the control area. Water hyacinth was drastically curtailed within the impoundment and constituted only 0.5% of the vegetation in the impoundment but made up 18.8% within the control area. The reduction of water hyacinth was probably related to the drier conditions within the impoundment during drawdown (Carney and Chabreck 1977). The manipulated freshwater impoundments on Rockefeller produced an abundance of high quality food, but without absolute water level control, lean years were inevitable (Chabreck 1960). 114 Impoundment Control 23.3 94.5 41.5 0.0 11.8 0.0 8.8 0.0 4.2 0.0 3.4 0.0 7.0 5.5 Table 2. Percentage of vegetative composition in manipulated freshwater impoundments and adjacent freshwater marsh on Rockefeller Refuge in 1959 (data from Chabreck 1960). % Cover Species Marshhay cordgrass Wild millet Sprangletop Widgeongrass Waterhyssop Nutgrass Other Wildlife Manipulated freshwater impoundments are usually managed for dabbling ducks. A study by Chabreck et al. (1974) found that year-round dabbling duck use of an impoundment was over 4 times that of an adjacent non-impounded marsh. Waterfowl use of impoundments was greatest during the winter and the least during the summer, and was over 6 times greater in the impounded area than in the control area during the winter. Duck use of an impounded area in southcentral Louisiana during the winter was 9 times greater than usage in a control area (Carney and Chabreck 1977). In addition to waterfowl, other wildlife benefit from this type of management. Coots and rails use this habitat quite heavily as long as water depths are favorable. Wading birds are attracted to the impoundment by shallow water conditions. This impoundment type is highly preferred by most fur animals, particularly species such as mink (Mustela vison), raccoon (Procyon lotor), and river otter (Lutra canadensis) that feed on crawfish (Procambarus clarkii). Nutria also find this habitat favorable. Alligators are attracted by the abundance of prey (Chabreck 1960), but early drying may reduce nesting (Joanen and McNease 1978). Permanently Flooded Brackish Impoundments Plants. On Rockefeller Refuge, impoundments permanently flooded with brackish water consis- tently produced an abundance of high quality duck foods, dominated by widgeongrass (Table 3). A survey of marsh impoundments in South Carolina disclosed that the permanently flooded brackish impoundments were the habitat most often used by ducks in that State (Morgan et al. 1975). Wildlife. The permanently flooded brackish impoundments are heavily used by gadwalls, American widgeons, and lesser scaup {Aythya affinis), which are attracted to dense stands of widgeongrass. These impoundments receive high use by coots, but wading birds and fur animals avoid them because of water depth and lack of cover. Brackish marsh is not preferred alligator habitat if water salinity becomes excessive (Chabreck 1960). Manipulated Brackish Impoundments Plants. In manipulated brackish impoundments, the most successful technique in South Carolina involves a spring drawndown for 2 to 8 weeks, during which time the marsh is maintained in a 115 Table 3. Percentage of vegetative composition in permanently flooded brackish impoundments and adjacent brackish marsh on Rockefeller Refuge in 1959 (data from Chabreck 1960). % Cover Species Impoundment Control Marshhay cordgrass Widgeongrass Other 40.5 55.5 4.0 96.9 0.0 3.1 saturated but dewatered condition. In late spring or early summer, the marsh is completely drawn down for 1 to 2 weeks, then reflooded to a depth of 15 to 20 cm. Throughout the remainder of the growing season, water levels are gradually raised to depths of 46 to 76 cm, and water circulation is maintained (Prevost 1987). This management regime provides optimum conditions for production of important brackish water duck-food plants. A spring drawdown with moist soil conditions allows saltmarsh bulrush (Scirpus maritima) to sprout on areas of higher elevations. Moist soil minimizes acid conditions associated with prolonged drainage of brackish marshes (Edelman and Van Staveren 1958; Neely 1958). Complete drawdown prior to reflooding in early summer stabilizes soils and minimizes turbidity, thereby enhancing widgeongrass germination and growth and helping prevent wave action from uprooting widgeongrass seedlings (Joanen and Glasgow 1965). Late summer die-offs of widgeongrass (Percival et al. 1970) and destruction of widgeongrass stands by filamentous algae {Cladophora sp.) (Prevost et al. 1978) generally can be avoided by early summer flooding followed by vigorous water circulation and gradual elevation of water levels. Wildlife. Manipulated brackish impoundments provide excellent dabbling duck habitat and are also used by diving ducks, snow geese {Chen caerulescens), and coots. The cycle of flooding and draining attracts wading birds. This habitat type is ideal for fur animals. Abundant cover, food, and feeding conditions are available for both herbivores and carnivores (Chabreck 1960). Advantages and Disadvantages of Impoundments Impoundments enhance waterfowl wintering habitat. At Rockefeller Refuge, the impoundments produced an abundance of food as well as provided an ideal resting area for ducks. Of the total number of ducks on the refuge, about 80% used the impoundments. Aerial inventories by the Louisiana Wildlife and Fisheries Commission revealed that Rockefeller Refuge wintered fewer than 75,000 ducks in 1951 and 1952 prior to the construction of the impoundments. In 1958-59, the inventory indicated that 443,000 ducks wintered on Rockefeller Refuge (Chabreck 1960). Improvement of duck habitat by impoundments may mitigate the effects of duck habitat loss elsewhere in the region. Impoundments may simply redistribute ducks, causing crowding and promoting disease transmission (Whitman 1976), but this has not been identified as a problem in Louisiana. More nongame species than game species use impoundments (Epstein and Joyner 1986). Strange (1987) stated that it is impossible to manage an impoundment for a certain species without benefiting many other species. 116 On Rockefeller Refuge and Lacassine National Wildlife Refuge, the permanently flooded freshwater impoundments were favorable to alligators (Chabreck 1960; Carbonneau 1987). In certain coastal areas, deer (Odocoileus virginianus) populations have benefited from impoundments. In addition to having permanent freshwater and an increased food supply, the levees provide travel lanes, escape cover, and protection during floods (Chabreck 1960; Joanen et al. 1985). In South Carolina, brackish impoundments managed for waterfowl provide greater and more diversified wildlife use than unmanaged sites. Predatory birds and alligator numbers were greater in managed than in unmanaged marshes, presumably because of the high prey availability (Epstein and Joyner 1986). In the impoundments during drawdown, shorebirds and wading birds were more abundant than were waterfowl (Strange 1987). Annual drying of freshwater impoundments is essential for growth of annual plants, and periodic drying of brackish impoundments is necessary to maximize production of aquatic plants. However, certain groups such as alligators, mottled ducks, and aquatic organisms may be temporarily affected by these programs (Davidson and Chabreck 1983). Water salinities in impounded marshes more often reflect the historical trends of salinity in an area than do non-impounded areas (Chabreck 1960). Water hyacinth, a pest plant in Louisiana fresh marshes, is curtailed in manipulated freshwater impoundments which are drained (Carney and Chabreck 1977). Tidal marshes and associated water bodies are important nursery areas for marine fish and crustaceans, and impoundment levees block the ingress and egress of these organisms. Operation of water control structures to allow organisms to enter and exit impoundments has been successfully practiced on Rockefeller Refuge (Davidson and Chabreck 1983). Marsh impoundments have certain limitations, which at times makes it necessary for landowners to use other types of management. First, impoundments are costly to construct and maintain. Also, without facilities for pumping water, years that are unusually wet or dry generally result in poor food production. Impoundments can only be built in areas that will support a continuous levee. In certain areas, such as southeastern Louisiana, the use of impoundments is limited because of the fluid nature of the subsoil. We are currently studying the effects of water manipulation on plants and wildlife in a floating freshwater marsh impoundment in southeastern Louisiana. The study will determine the feasibility of water manipulation as a wildlife management tool in southeastern Louisiana, where the soil is highly organic. LITERATURE CITED Alexander, C.E., M.A Boutman, and D.W. Field. 1986. An inventory of coastal wetlands of the USA U.S. Department of Commerce. Washington, DC. 25 pp. Baldwin, W.P. 1968. Impoundments for waterfowl on South Atlantic and gulf coastal marshes. Pages 127-133 in J.D. Newsom, ed. Proceedings of the marsh and estuary management symposium. Louisiana State University, Baton Rouge. Carbonneau, D.A. 1987. Nesting ecology of an American alligator population in a freshwater coastal marsh. M.S. Thesis. Louisiana State University, Baton Rouge. 53 pp. 117 Carney, D.F., and R.H. Chabreck. 1977. An evaluation of spring drawdown as a waterfowl management practice in floating fresh marsh. Proc. Annu. Conf. Southeast. Assoc. Fish Wildl. Agencies 31:266-271. Chabreck, R.H. 1960. Coastal marsh impoundments for ducks in Louisiana. Proc. Annu. Conf. Southeast. Assoc. Fish Game Comm. 14:24-29. Chabreck, R.H., and R.G. Linscombe. 1982. Changes in vegetative types in the Louisiana coastal marshes over a 10-year period. La. Acad. Sci. 45:98-102. Chabreck, R.H., R.K. Yancey, and L. McNease. 1974. Duck usage of management units in the Louisiana coastal marshes Proc. Annu. Conf. Southeast. Assoc. Game Fish Comm. 28:507-517. Chamberlain, J.L. 1959. Gulf coast marsh vegetation as food of wintering waterfowl. J. Wildl. Manage. 23(1):97-102. Davidson, R.B., and R.H. Chabreck. 1983. Fish, wildlife and recreational values of brackish marsh impoundments. Pages 89-114 in R.J. Varnell, ed. Proceedings of the water quality and wetlands management conference, New Orleans. Edelman, C.H., and J.M. Van Staveren. 1958. Marsh soils in the United States and in the Netherlands. Soil Water Conserv. 13(1):5-17. Epstein, M.B., and R.L. Joyner. 1986. Use of managed and unmanaged marshes by waterbirds and alligators. In M.R. DeVoe and D.S. Baugham, eds. Coastal wetland impoundments: ecological characterization, management, status, and use. Vol 2. Synthesis. S.C. Sea Grant Consortium, Charleston. Fruge, D.W. 1974. The vegetation of Lacassine Pool, Lacassine National Wildlife Refuge, Louisiana. U.S. Fish and Wildlife Service Refuge Division, Washington, DC. 51 pp. Hansen, H.A, and M.R. Hudgin. 1966. Waterfowl status report 1966. U.S. Fish Wildl. Serv. Spec. Sci. Rep. Wildl. 99. 95 pp. Joanen, T., and L.L. Glasgow. 1965. Factors influencing the establishment of widgeongrass stands in Louisiana. Proc. Annu. Conf. Southeast Assoc. Game Fish Comm. 19:78-92. Joanen, T., and L. McNease. 1978. Time of egg deposition for the American alligator. Proc. Annu. Conf. Southeast. Assoc. Fish Wildl. Agencies 33:15-19. Joanen, T, L. McNease, and D. Richard. 1985. The effects of winter flooding on white-tailed deer in southwestern Louisiana. Proc. La. Acad. Sci. 48:109-115. Kimble, R.B., and A Ensminger. 1959. Duck food habits in southwestern Louisiana marshes following a hurricane. J. Wildl. Manage. 23(4):78-92. Morgan, P.H., AS. Johnson, W.P. Baldwin, and J.L. Landers. 1975. Characteristics and management of tidal impoundments for wildlife in a South Carolina estuary. Proc. Annu. Conf. Southeast Assoc. Game Fish Comm. 29:526-539. Neely, W.W. 1958. Irreversible drainage - a new factor in waterfowl management. Trans. No. Am. Wildl. Conf. 14:30-34. Percival, H.F., L.G. Webb, and N.R. Page. 1970. Some ecological conditions under which selected waterfowl food plants grow in South Carolina. Proc. Annu. Conf. Southeast. Assoc. Game Fish Comm. 24:121-126. Prevost, M.B. 1987. Management of plant communities for waterfowl in coastal South Carolina. Pages 168-183 in W.R. Whitman and W.H. Meredith, eds. Waterfowl and wetlands symposium: proceedings of a symposium on waterfowl and wetlands management in the Coastal Zone of the Atlantic Flyway. Delaware coastal management program, Delaware Department of Natural Resources and Environmental Coastal, Dover. 118 Prevost, M.B., AS. Johnson, and J.L. Landers. 1978. Production and utilization of waterfowl foods in brackish impoundments in South Carolina. Proc. Annu. Conf. Southeast. Assoc. Fish Wildl. Agencies 32:60-70. Strange, T. 1987. Goals and objectives of water level manipulations in impounded wetlands in South Carolina. In W.R. Whitman and W.H. Meredith, eds. Waterfowl and wetland symposium: proceedings of a symposium on waterfowl and wetlands management in the coastal zone of the Atlantic flyway. Delaware Coastal Management Program, Delaware Department of Natural Resources and Environmental Control, Dover. Wicker, K.M., D. Davis, and D. Roberts. 1983. Rockefeller State Wildlife Refuge and Game Preserve: evaluation of wetland management techniques. La. Dep. Nat. Resour., Coastal Manage. Section. 56 pp. Williams, R.K. 1987. Construction, maintenance, and water control structures of tidal impoundments in South Carolina. In W.R. Whitman and W.H. Meredith, eds. Waterfowl and wetland symposium: proceedings of a symposium on waterfowl and wetlands management in the coastal zone of the Atlantic flyway. Delaware Coastal Management Program, Delaware Department of Natural Resources and Environmental Control, Dover. Whitman, W.R. 1976. Impoundments for waterfowl. Canadian Wildl. Serv. Occas. Pap. No. 22. 22 pp. Yancey, R.K. 1964. Matches and marshes. Pages 619-626 in J.P. Linduska, ed. Waterfowl tomorrow. U.S. Department of the Interior, Washington, DC. 770 pp. 119 VEGETATION AND SALINITY CHANGES FOLLOWING THE INSTALLATION OF A FIXED CREST WEIR AT AVERY ISLAND, LOUISIANA (1982-86) Billy R. Craft and Dolan Kleinpeter Soil Conservation Service Alexandria, LA 71302 ABSTRACT Fixed crest weirs have been extensively used in Louisiana's coastal area. This study was initiated primarily to document the impacts of a fixed crest weir on vegetative communities and water salinities. The duration of this study extended from June 1982 through June 1986. The study area is an ecotone of fresh marsh-shrub swamp comprising about 202 ha and is subject to daily tidal influence. The fixed crest weir was installed in September 1981. It was constructed of creosote sheet piling and tongue and groove timbers. Length of the weir crest was 6.1 m. A modified line transect-circular plot sample technique was used annually to sample vegetation. Foliar cover was of primary interest. The transect line was orientated in a north-south direction to transverse the area influenced by the weir. Along the transect line, 0.08-ha sample plots were established at 60.96-m intervals. Salinity of the water was checked monthly. Samples were taken 91.4 m above and 91.4 m below the weir site. Salinity in parts per thousand was determined by using a Yellow Springs Instrument Model 33-S-C-T salinity meter. Noticeable changes occurred in the plant community. In 1982, there were 29 species of plants recorded; in 1986, 35 species. Over the study period, woody plant cover decreased and herbaceous plant cover increased. Generally, plants beneficial to wildlife increased in abundance. The coverage of Baccharis halimifolia changed more than any other plant. There was a reduction of eastern baccharis at seven of the sample stations. This allowed herbaceous plants such as Bacopa caroliniana, Eleocharis sp., and Scirpus robustus to increase, possibly because of more sunlight, less competition, and more stable water levels. Salinity differences were evident in a comparison of upstream and downstream results. Monthly salinity was determined for 56 months. For 41 months (73%), salinity was less upstream of the weir; for 12 months, salinity was the same upstream and downstream of the weir, and for 3 months, salinity was greater upstream of the weir. Based on the objective of the landowner, which was to improve habitat for waterfowl and furbearers, the fixed crest weir is serving to accomplish its purpose and function. INTRODUCTION Fixed crest weirs have been extensively used in Louisiana's coastal brackish and intermediate marshes (Chabreck and Hoffpauir 1962; Chabreck 1967; Larrick and Chabreck 1976). However, 120 very limited use of fixed crest weirs has occurred in fresh marshes. For fresh marshes, where marsh management is an objective of the landowner and a structure is needed, the Soil Conservation Service would normally recommend a variable crest structure for better water management capability. In this study, the landowner specifically requested a fixed crest weir. Since research data were lacking on the impacts of fixed crest weirs in fresh marshes, this study was undertaken to gather some baseline data on vegetation and water salinity. The primary objective of the landowner was to improve the area for waterfowl and furbearers. MATERIALS AND METHODS The study area was a 202-ha tract in at an ecotone of fresh marsh-shrub swamp. The area is east of Avery Island in Iberia Parish, 8 km north of Vermilion Bay. The fixed crest weir was installed in September 1981 on what is locally called the "logging canal." The logging canal outlets into Bayou Petite Anse, the major outlet for marsh areas east and north of Avery Island. Creosote sheet pilings and tongue and groove timbers were used for construction of the weir. From September 1981 to July 1983, the weir crest was set at 0.46 m above mean sea level (MSL). From July 1983 to June 1986, the weir crest was set at 0.55 m mean above sea level. Normal marsh elevation averaged 0.61 m above MSL. A modified line transect-circular plot sample technique was used to sample vegetation. Foliar cover was of primary interest. The transect line was oriented north to south to traverse the area influenced by the weir. Along the transect line, 0.08-ha sample plots were established at 60.96-m intervals; 12 permanent plots were established. Salinity of the water was checked monthly. Samples were taken 91.4 m above and 91.4 m below the weir site. Salinity in parts per thousand (ppt) was determined by using a Yellow Springs Instrument Model 33-S-C-T salinity meter. Sampling was conducted from June 1982 through June 1986. Vegetation was sampled once each year and salinity once each month. RESULTS AND DISCUSSION Vegetation In 1982, the vegetative community contained a mix of species representing woody and herbaceous plants. A total of 29 species were recorded in 1982 (Table 1). Dominant plants included Baccharis halimifolia, Sagittaria lancifolia, Sabal minor, and Cladium jamaicense. Over time, woody plant cover decreased and herbaceous plant cover increased (Tables 1-5). The coverage of Baccharis halimifolia changed more than any other plant in the 5-year sampling period. Reductions occurred at seven of the sample stations. Another woody species, Myrica cerifera, showed signs of stress as evidenced by branches defoliating and discoloration of remaining leaves. With the reduction in woody plant coverage, there was a corresponding increase in herbaceous plants including Bacopa caroliniana, Scirpus robustus, Eleocharis sp., and Sagittaria lancifolia. Some possible reasons for this were more stable water levels, more sunlight reaching the marsh floor, and less competition. 121 oo o\ U a a o o a. o on 3 e "S 03 t/1 .2 y o> a ifl a eg I o o o M O o M rH iH rH H r4 « m Eh o rJ C H >H k4 u o CT> CM H r^ Eh H f^ Eh rH o O U IH >H U CO C *H en Eh Eh Eh Eh 0 CQ ■r4 0. a, a. 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U CO CU ■H 01 U < H q> 4->,*JaE>-x:<--( UUQH^^tlH Qj £ XI V- 0 *■ 1 1 t o C -H J» O 3 o 4_j i-E'Hcri-acoo j^C4-t&tj>!t-iua a C T a o a o 1 J* i- T C t rH J C 4J H o CO H S H C f- i-Ul-i ■HC0U3OC0r-(K- ,H c ■- 1 o •H *. > 3 0 1 l) ttli- l- CO ct rH t M CO 1 co E « 3 C K M « U i/;3cacu:3SO a-rHcocop3c03 co c/50e_?c/)QQSCU cu CU Cl ! XL ^H U i co : t O -H CC l- < a r- cu : O to M Ph| a \ to U < >• v ) S ee 1/ c/tIb: >- c 32 W H 126 Weirs usually reduce water-level fluctuations, reduce the volume of water during tidal exchanges, and moderate salinity changes (Chabreck 1967; Hoar 1975; Morgan et al. 1975; United States Department of Agriculture 1976). The impacts on vegetation should be a high priority consideration when weirs are planned as components of marsh conservation plans. Plant community characteristics play a vital role in the productivity of coastal marshes (Craft and Smith 1986). In this study, plants beneficial to wildlife increased in abundance and in diversity. This change was consistent with the landowner's objectives. Salinity Salinity was less upstream of the weir for 41 of the 56 monthly samples (Table 6). For 12 of the 56 monthly samples, the salinity was the same upstream and downstream of the weir. The salinity was greater upstream of the weir for three monthly samples. Salinity levels were smaller upstream for all yearly averages (Figure 1). Use of Fixed Crest Weirs in Fresh Marshes Very limited use has been made of fixed crest weirs in fresh marshes. The results of installation of this weir were consistent with the landowner's objective. In the future, greater water management capability could be achieved with the use of variable crest water-control structures when there is a need identified for a structure. Table 6. Salinity readings, in parts per thousand. Upstream Downstream of weir of weir Date Site (91.4 m) (91.4 m) 10/1/81 Logging Canal 4.0 4.0 11/1/81 3.7 3.7 12/1/81 4.0 4.0 1/1/82 4.0 4.0 2/1/82 4.0 4.0 3/1/82 0.0 0.0 4/1/82 2.0 2.0 5/1/82 2.0 2.0 6/1/82 1.0 1.0 7/1/82 0.7 1.3 8/1/82 0.1 2.1 9/1/82 3.5 16.7 10/1/82 1.0 3.1 11/1/82 1.3 3.5 12/1/82 1.6 4.4 1/1/83 0.0 0.7 (Continued) 127 Table 6. Concluded. Upstream of weir Date Site (91.4 m) 2/1/83 Logging Canal 0.1 3/1/83 0.1 5/1/82 0.2 6/1/83 0.8 7/1/83 0.3 8/1/83 0.5 9/1/83 0.9 10/1/83 1.5 11/1/83 1.6 12/1/83 1.0 1/1/84 0.5 2/1/84 0.1 3/1/84 0.1 4/1/84 0.5 5/1/84 5.0 6/1/84 0.6 7/1/84 0.1 8/1/84 0.1 9/1/84 0.3 10/1/84 10.0 11/1/84 0.9 12/1/84 2.2 1/1/85 0.1 2/1/85 0.1 3/1/85 0.0 4/1/85 0.3 5/1/85 0.0 6/1/85 1.0 7/1/85 4.0 8/1/85 0.6 9/1/85 2.1 10/1/85 0.1 11/1/85 0.1 12/1/85 1.4 1/1/86 0.9 2/1/86 1.1 3/1/86 2.2 4/1/86 2.0 5/1/86 2.9 6/1/86 2.5 Downstream of weir (91.4 m) 1.1 1.5 0.4 2.0 0.6 2.2 2.7 1.6 3.7 1.6 2.0 1.8 0.8 2.4 5.1 0.8 0.4 0.5 1.3 5.5 2.0 1.5 0.7 1.0 0.2 0.9 0.2 1.9 3.0 1.0 3.1 1.9 1.2 1.5 0.9 1.1 2.2 2.4 3.0 2.6 128 e (- in c X o 6 m u t, W a 3 "i — m « « U) V n n e "T" (U (VI T" T CO U> T~1 — r~r CU "^ CO 10 ~r ~r (0 CO 01 in a en * — a a (A <— o ao ft en | (Q > 0> ►» > i- 1 09 & E en (U ao W W W CI CU CXI (\J CM «■« *"• (idd) Aiiuiies o o o o 129 ACKNOWLEDGMENTS Appreciation is extended to the personnel of the Mcllhenny Company at Avery Island who provided assistance with the field work. Thanks also are extended to other Soil Conservation Service personnel who assisted in this effort over the years. LITERATURE CITED Chabreck, R.H. 1967. Weirs, plugs, and artificial potholes for the management of wildlife in coastal marshes. Pages 178-192 in J.D. Newsom, ed. Proceedings of the Marsh and Estuary Management Symposium. Louisiana State University, Baton Rouge. Chabreck, R.H., and CM. Hoffpauir. 1962. The use of weirs in coastal management. Proc. 8th Conf. S.E. Assoc. Game Fish Comm. 8:03-2. Craft, B.R., and E.R. Smith. 1986. Changes in vegetation in the Cameron-Creole marshes of Louisiana over a thirty-two year period. Proc. 10th Nat. Con. Coastal Soc. 10:187-203. Hoar, R.J., Sr. 1975. The influence of weirs on soil and water characteristics in the coastal marshlands of southeastern Louisiana. M.S. Thesis. Louisiana State University, Baton Rouge. 94 pp. Larrick, W.J., Jr., and R.H. Chabreck. 1976. Effects of weirs on aquatic vegetation along the Louisiana coast. Proc. 30th Conf. S.E. Assoc. Game Fish Comm. 30:581-589. Morgan, P.H., A. S. Johnson, W.P. Baldwin, and J.L. Landers. 1975. Characteristics and management of tidal impoundments for wildlife in a South Carolina estuary. Proc. 29th Conf. S.E. Assoc. Game Fish Comm. 29:526-539. U. S. Department of Agriculture. 1976. Gulf coast wetlands handbook. 90 pp. 130 COMPARISONS OF SALINITY, HYDROLOGY, AND VEGETATION CHARACTERISTICS BETWEEN FREE-FLOWING AND SEMI-IMPOUNDED INTERMEDIATE-TO-BRACKISH TIDAL MARSH SYSTEMS John F. Meeder Ecosystem Research Unit National Audubon Society Route 6, Box 610 Abbeville, LA 70510 ABSTRACT The National Audubon Society began a long-term ecosystem research study of the Paul J. Rainey Wildlife Sanctuary's coastal marshes in November 1984. The purpose of the study is to identify and quantify marsh processes, to identify and quantify the effects of marsh management, and to create a data base for evaluation of ongoing processes and future changes within the system. Results for the first 2 years of data are presented for Toms Bayou, which is free-flowing, and Big Island Bayou, which has been semi-impounded since 1967 by a fixed-crest weir set 9 inches below marsh level. Data on climatic conditions, water levels, salinity, vegetation composition, and standing crop were collected at two stations in each system: one located in the marshes of the upstream (U) one-third, and one in the downstream (D) one-quarter. In addition, data were obtained from a tidal recorder in Fearman Bayou, which is tidally connected to both systems. Both downstream sites have higher plant diversities, higher maximum standing crops than their upstream counterparts and are dominated by Spartina patens (Ait.) Muhl. Upstream sites are characterized by greater relative abundance of Scirpus olneyi. Belowground biomass averaged 5,010 g/m2 at the four stations, with 50% of the biomass found in the upper 10 cm of soil. The 2-year hydroperiod in the upstream marshes is 401 days in Big Island Bayou compared to 132 days in Toms Bayou, and the number of inundations is greater (32 versus 20 flooding events). However, the reduced tidal height in the Big Island system prevents frequent flooding over the well-developed natural levee in downstream marshes, reducing the 2-year hydroperiod to 299 days in Toms and 85 days in Big Island. During droughts, marsh salinities became more elevated in the semi-impounded Big Island system because of inefficient tidal exchange, and concentrations of salts by evapotranspiration (up to 12 mm water/day). Salinities in the system were also elevated for a longer period after Hurricane Danny because of inefficient runoff. Year 1 downstream marsh salinities in Big Island averaged 2.4 ppt higher than at Toms for these reasons. Marsh salinities were everywhere higher than adjacent bayou salinities with the exception of measurements taken immediately after rainfall events. The data indicate that the vegetation parameters in the marsh semi-impounded by fixed-crest weirs were not statistically different from those measured in the free-flowing marshes. However, the semi-impounded marshes were more prone to salinity crises and the effects of extended hydroperiod and wetter soils. Big Island marshes also had lower maximum standing crops than Toms Bayou marshes. 131 INTRODUCTION Intermediate and brackish tidal marshes are some of the most productive and, unfortunately, some of the fastest disappearing coastal ecosystems in the Gulf Coastal Region (Craig et al. 1979). The major reason for large losses of intermediate and brackish marsh is saltwater intrusion. Several natural and human-induced factors influence the rate of saltwater intrusion and resultant marsh loss (Salinas et al. 1986). They are: 1) regional subsidence, 2) eustatic sea-level rise, 3) freshwater and sediment diversion away from coastal marshes, 4) deep-water channel and levee construction for navigation and hydrocarbon production, and 5) improper or insufficient marsh management. In general, the effects of these vary from locality to locality depending upon distance from the Gulf of Mexico or a tidal water source, amount of freshwater head in drainage basin, amount of available sediment, degree of minerals production, and presence of structures affecting natural hydrologic patterns. The National Audubon Society's long-term interest in marsh ecology and management is based on recognition of the national importance of the Nation's wetlands, recognition of the special importance of southwest Louisiana's marshes to numerous waterfowl and non-game wildlife species, both resident and migratory, and land stewardship. The Society's interest and research in coastal wetlands began with the work of Robert Allen and Alexander Sprunt in the 1930's and 1940's. The Audubon Society's research program was the first founded by any private conservation group and has expanded continuously since its origin. The National Audubon Society's Paul J. Rainey Wildlife Sanctuary was established in 1926 by bequest from the estate of Paul J. Rainey. The sanctuary consists of 26,000 acres of intermediate and brackish water marshes in Vermilion Parish. The Society is obliged by deed to provide habitat for wintering snow geese. Marsh management is, therefore, centered around the production of Scirpus olneyi, the snow goose's preferred forage. Management practices include prescribed burning, water management, and muskrat population control. With the recent quantification of marsh loss in Louisiana by numerous studies, identification of many processes causing marsh loss, and serious questions arising on the effects of marsh management practices, the Society's interest in quantifying its own management practices intensified. In 1984, a long-term study was begun which will span 6 years. The purpose of the study is to identify and quantify marsh processes, quantify marsh management practices, and provide a data base sufficient to evaluate ongoing processes and future changes in the system. This report compares the hydrology, salinity, and vegetation characteristics over a 2-year period (May 1985 to May 1987) between two adjacent marsh watersheds-the free-flowing Toms Bayou and the semi-impounded Big Island Bayou. METHODS Location and Site Description Both Toms and Big Island Bayous flow northward, each draining several thousand acres of marsh. A steel piling fixed -crest weir was placed near the mouth of Big Island (BI) Bayou in 1967. The Big Island watershed is further modified by the loss of portions of the westernmost watershed by the construction of the Mcllhenny Canal and adjacent levee in the early 1900's and the construction of ditch systems connected to the Mcllhenny Canal by way of additional small scale fixed-crest weirs. These later structures have been added in the past 25 years. 132 The Big Island weir was constructed on National Audubon Property in cooperation and accordance with State Wildlife Refuge practices at the time. The weir was constructed to prevent conditions of saltwater intrusion and marsh overdrainage by local and regional construction of deep water channels (most notably, channelization of Southwest Pass and of Freshwater Bayou, dredging of Four Mile Cut, and the earlier construction of the Mcllhenny and Brunner Canals on the sanctuary). Semi-impoundments were constructed also to enhance habitat for fish and animal life by encouraging aquatic vegetation growth (Larrick and Chabreck 1976). Fisheries work by Herke (1979) and Herke et al. (1987) have shown that semi-impoundment by fixed-crest weirs decreases fishery usage and yield. Toms Bayou (TB) remains a pristine marsh watershed. No major deepwater channels are near, the system is free-flowing, and only minor non-diversionary ditching has occurred in the upper portion of the watershed. Two sampling stations were installed in both TB and BI bayou watersheds (Meeder 1986). One station was placed in the downstream (D) and one in the upstream (U) portions of each watershed. Marsh differences between upstream and downstream sites were elevation (Table 1), plant species composition, and distance from bayou mouths. Instruments placed at each station included a Stevens F-Type water-level recorder, with QMT clocks set for 16 days, placed on a 4-inch-diameter perforated pipe hand-driven into the marsh; a Table 1. Summary of marsh site characteristics. Freeflowing sites8 Semi-im pounded sitesb Characteristics TBU TBD BIU BID Elevation (m) 1.37 1.436 1.78 1.116 Events (2-year period) 120 36 32 12 Days inundated 132 299 401 85 Salinity (ppt) 6.3 5.1 6.4 6.6 No. abundant species 3 5 3 5 Max. standing cropc 1,040 1,750 775 1,340 Avg. standing crop0 Scirpus olneyi 274 127 162 167 Spartina patens 213 1078 377 793 Ratio of S. olneyi to S. patens avg. st. crop 1.28 0.12 0.43 0.21 Avg. belowground biomass 5,812 5,121 4,813 4,220 aTBU = Toms Bayou upstream marshes TBD = Toms Bayou downstream marshes bBIU = Big Island upstream marshes BID = Big Island downstream marshes caboveground biomass (g dw/m2) 133 caged evaporation pan; four rain gauges, and a max-min recording thermometer. Vegetation plots (20 x 100 m) were established for burned, unburned, and grazed treatments, and for marsh soil and water sampling. The hydroperiod was calculated for the field station areas by establishing the elevation at 1-m intervals for a distance of 50 m in four directions from the well. Average elevation was used to determine the length of time (days) the marsh was inundated (Duever 1977). Salinity Salinity was measured by using Yellow Springs Instrument-SCT meter and an AO temperature- compensated refractometer. Paired data are defined as salinity data that were taken at all stations at nearly the same time or at least within the same marsh conditions (usually within a day). Surveying All stations were surveyed and referenced to U.S. Geological Survey marker AUD 2 with an assumed elevation of 1.524 m above MSL. The closest known elevation marker is on Chenier au Tigre and its stability is questioned. Surveying was done with a TOPCON self-leveling transect, a 100-m tape, and telescoping rod marked to the nearest 0.5 cm. Vegetation Vegetation characteristics were measured by clip-plotting five 0.1-m2 plots chosen randomly along the 100-m transect. Vegetation height was measured, plants clipped at soil surface, sorted to species, live and dead material sorted, stems counted, dried at 100 °C for 24 h, and weighed to the nearest 0.1 g by using an O'Haus triple beam scale. Sampling was conducted at 3-month intervals from April 1985 through July 1986 and in July 1987 at all stations. Four-inch-diameter soil cores were taken from the lower right hand corner of each clip plot on each sampling date. Cores were subdivided at depths of 0-10 cm and 10-30 cm, sorted for root material, dried, and weighed as belowground material. Sampling was done on all vegetation plots but only those data from plots burned in the late fall or early winter were used in this report. Tide and Climate Monitoring A water-level recorder was set up at Fearman Bayou to measure tidal water fluctuations, and salinity was measured at this station. Establishing water levels and salinity of incoming and returning tidal water is important in interpreting marsh water-level records. Other data necessary for understanding marsh hydrology are rainfall and potential evaporation, which were collected at the field stations as well as the main weather station (U.S. Weather Bureau 1970). RESULTS Elevation Marsh surveying recorded marsh elevations every 50 m across the open marsh and at intervals of 1 or 5 m along transects across field stations. The marsh surface had a slight downward slope towards the north and west. Toms Bayou marshes averaged approximately 20 cm higher than Big Island marshes to the west at similar latitudes (TBU= 1.371, BIU=1.178; TBD=1.436, BID = 1.116 m above MSL). Both downstream stations are located in marshes developed behind natural bayou levees with elevations above MSL of 1.600 m at TBD and 1.251 m at BID. Note that the top of the levees are at an elevation slightly higher than the upstream marsh surfaces (0.16 134 for TBD and 0.14 m for BID). Thus, in order for tidal waters to wet the downstream marshes, the tidal waters must be close to or already inundating the upstream marshes where no natural levees exist or are poorly developed. TBD marshes are flooded more frequently than BID marshes because the rate of tidal water rising is much greater in the TB system. The ingressing tide is delayed in the BI system by the weir. Tidal lag becomes more apparent the further upstream in the watershed where bayous become smaller, more sinuous, and more impeded by vegetation and slow tidal egress. This normal tidal lag explains the differences observed between (TBU) and (TBD). For example, difference in tidal peaks between Fearman Bayou tidal station and the Chenier au Tigre tidal station (located near the end of the Mcllhenny Canal) varies from 2 to 4 hours, depending upon tidal strength. On the other hand, differences in tidal lows vary from 6 to 12 hours depending upon how much marsh inundation occurred-the more inundation, the longer the difference. Plant composition and distribution The most abundant marsh type at the Rainey Sanctuary is the brackish marsh as defined by the most abundant plant species, Spartina patens and Scirpus olneyi (Chabreck 1972). During cycles of wet years, intermediate salinity marsh plants such as cattail (Typha sp.) and bull tongue {Sagittaria lancifolia) become much more abundant. Marsh vegetation exhibits both gradational and distinct lateral zonation depending upon elevation and site history. The most distinct zonation occurs across well-developed natural levees along both Toms and Big Island Bayous. Roseau cane (Phragmites phragmites) with mangrove (Iva frutescens) dominate the highest portions of the levee adjacent to the bayou. Hog cane {Spartina cynosuroides) mixes with and eventually replaces the Phragmites marshward as marsh elevation drops. Spartina patens mixes with and replaces the Spartina cynosuroides as elevation approaches average marsh interior elevation. Juncus roemerianus and Fimbristylis castanea are also locally abundant in this zone. These three vegetative zones are subject to great variability in widths, depending upon how well- developed the bayou levee is. In upstream areas without levees, very little zonation is apparent and Juncus is absent. In the marsh interior not influenced by natural levees, a mixed plant community of Spartina patens and Scirpus olneyi is found. Species dominance in any one spot is dependent on relative elevation and site history. Dominance of species other than Spartina patens and Scirpus olneyi is unusual and usually limited to local topographic highs (Meeder 1987). Elevation across the marsh is very uniform (difference usually less than 9 cm) but increases to 15 cm in areas of recent snow goose or muskrat eatouts. Scirpus olneyi was almost always most common along "ridges" (+5 cm above average), whereas Spartina patens was almost always most abundant in "swales" (-5 cm below average elevation), along lake and bayou margins of interior marshes, and in areas unburned for 2 or more years. In the lowest spots, marsh soil continuity is often lost and Spartina patens is the only plant found. The loss of the spreading root system of Scirpus olneyi, which binds soil, may be a major factor in marsh surface degradation. In these cases Spartina forms very elevated clumps (with roots exposed) which become progressively higher as organics are lost from between clumps. These observations are based on more than 12.6 km of marsh survey and numerous site visits in surrounding marshes. Relative elevation is believed to exert control over plant distribution because relative elevation determines the hydroperiod, which has a manyfold relationship with plant ecophysiology. In addition to elevation, Scirpus olneyi distribution was related to site history. Important aspects of site history that greatly affect plant species composition, percentage of cover, and structure are the frequency of burning, the type and intensity of grazing, and the grazing recovery state. For example, adjacent marsh plots will have very different species composition after only 1 year of burned and unburned treatments. Scirpus olneyi is favored under burned conditions (O'Neil 1949). 135 Both snow goose and muskrat graze preferentially on the fleshy rhizome of Scirpus olneyi. They often graze in one area until virtually all their available food source is gone, producing an eatout (Lynch et al. 1947; O'Neil 1949). Eatouts degrade the marsh surface, destroy soil continuity, produce excessive amounts of litter, and change species composition and the structure and percentage of cover. Very little Scirpus olneyi has been found during the first 2 years after eatouts in study areas at Rainey Sanctuary. Standing Crop Standing crop from four stations shows several patterns. First, both downstream stations have significantly higher (TBD= 1750, TBU= 1O40 gm/m2) maximum standing crops than do upstream stations (BID= 1340, BIU= 775 gm/m2) (Table 2). Second, Toms Bayou stations have slightly Table 2. Summary of standing crop data. Mean values (N-5) (g dry wt/0.1 m2)a Site and Month and year sampled speciesb 4/85 7/85 10/85 1/86 4/86 7/86 7/87 Avg. TBU Other 0.00 0.20 0.00 0.00 0.20 0.18 0.00 0.03 Spartina 8.30 46.88 67.34 0.14 0.78 2.28 23.04 20.06 Scirpus 25.30 57.00 1.80 0.42 3.92 61.14 41.68 27.32 Total 25.60 104.10 69.10 0.50 4.90 63.56 64.72 47.48 TBD Other 3.70 12.24 17.30 20.66 7.04 6.20 10.46 11.08 Spartina 20.18 58.90 155.06 132.34 133.02 140.18 115.52 107.89 Scirpus 22.14 29.76 2.74 1.30 9.02 11.98 12.16 12.73 Total 46.02 100.90 175.10 154.30 149.08 158.36 138.14 131.70 BIU Other NA 3.7 40.00 0.00 0.06 0.56 1.80 2.34 Spartina NA 42.68 73.10 0.30 9.48 42.52 58.20 37.71 Scirpus NA 31.06 3.90 0.42 21.54 22.62 17.50 16.17 Total NA 77.48 77.00 0.72 31.08 65.70 77.50 56.22 BID Other NA 30.44 12.82 23.72 23.20 10.06 7.84 18.01 Spartina NA 55.92 74.24 97.72 73.38 94.74 79.48 79.25 Scirpus NA 16.04 33.16 0.58 6.44 28.96 15.22 16.73 Total NA 102.4 120.72 122.02 103.02 133.76 102.80 114.04 aAverage multiplied by 10=g dry weigh t/m2. Abbreviations: See Table 1 for site abbreviations. Other = live plants which are not listed by name; Spartina = Spartina patens; Scirpus=Scirpus olneyi; Total =total biomass of living plants. 136 higher live standing crops than do respective Big Island Bayou stations. Finally, both upstream stations have proportionally higher standing crops of Scirpus olneyi than Spartina patens than do the downstream stations. In addition, downstream stations consistently have a third plant species component--v/««cuj roemerianus or Fimbristylis castanea. Although standing crop is herein defined as the live plant material, stem counts and average lengths were also measured. Stem counts prove to be less useful in estimating standing crop because plant width-to-length ratios vary with time of year and among sites during the same sampling period. Dry weight measurements per unit area are the only reliable quantifiable way to make comparisons in standing crop. No spatial patterns in belowground biomass could be detected. Average belowground biomass was found to be 5010 gm/m2. Fifty-one percent of the roots were found in the 0- to 10-cm soil interval. Salinity Marsh surface water salinity data are presented by season and by annual averages (Table 3). Seasons were: winter= January-March; spring= April-June; summer= July-September; and fall = October-December. This subdivision fits the seasonal temperature and plant growth cycles quite well (e.g., Scirpus olneyi usually has three crops; one maturing in April, one in July, and one in October) and allows comparison of the growth season salinity levels with crop biomass. Seasonally, salinity in the marsh is lowest during the winter and highest either in the spring or summer depending upon rainfall, Gulf of Mexico salinities, and winds. Little difference existed in mean salinity levels among years at each station except for BID. Salinities in 1985 in BID were elevated because Hurricane Danny's storm tide waters did not drain from the marsh before Table 3. Annual mean marsh salinity summary, May 1985 through May 1987. Sites8 Year BIU BID TBU TBD 1 Paired datab 6.4 +3.1 7.6 4.2 6.3 2.9 5.2 2.9 2 Paired data 6.4 +3.9 6.0 3.9 6.2 3.9 5.0 2.5 1&2 Paired data 6.4 +3.6 6.6 4.1 6.3 3.6 5.1 2.7 1&2 Complete datac 6.2 +3.2 6.7 3.9 6.4 3.2 5.4 2.8 Top number=annual mean salinity; bottom number=standard deviation; see Table 1 for site abbreviations. bPaired data=salinity measurements taken at all stations within one work day. cComplete data = all measurements of salinity taken at particular station. 137 Hurricane Juan arrived (Table 4). Differences identified in the salinity data were 1) TBD marsh had the lowest average salinity and the smallest standard deviation, 2) BID had the highest average salinity (1.5 ppt higher than TBD), and 3) TB marsh station salinities are generally lower than BI Bayou marsh salinities. This is the case even though salty tidal waters must move further into the marsh system to enter the BI system than they do to enter the TB system. Hydroperiod The number of inundated days, number of flooding events, and number of days per event are tabulated for each station (Table 5). Significant differences found are: 1) BIU has the longest hydroperiod and the longest average period of flooding (13 days), 2) TBD has the greatest number of flooding events and a hydroperiod approximately 75% as long as BIU, and 3) BID had the shortest hydroperiod and least number of flooding events. These data show the effects of the fixed-crest weir on marsh hydrology. Whereas the weir dampens the tidal peak in the marshes, which prohibits inundation of downstream marshes found behind natural levees, the weir also inhibits tidal egress, causing extended hydroperiod in the upstream marsh sites which are lower in elevation than the downstream levees. Hurricanes Danny and Juan provided two natural experiments which documented the effects of the weir on marsh hydrology. The period of inundation for both storms were extended from 21% to 56% in the BI system over the TB system (Table 4). Because hurricane storm waters often have elevated salinities (as in Hurricane Danny, which was a dry storm), the results of extending the hydroperiod can result in severe impacts to marsh vegetation. DISCUSSION The need for installing weirs must be questioned based upon this study. If the two major reasons for installing weirs are to stop overdrainage and prevent saltwater intrusion, weirs are not doing their jobs. Semi-impoundment to produce better Scirpus olneyi (Ross and Chabreck 1972; Table 4. Post-storm periods of marsh inundation. Hurricane Field Station8 Differences TBU BIU Danny Juan 56a 19 75b 44 28% longer in BI 56% longer in BI TBD BID Danny Juan 6 11 9 14 33% longer in BI 21% longer in BI aSee Table 1 for site abbreviations. bMaximum number, may be up to 7 days shorter. cMinimum number of days; never dry before Hurricane Juan. 138 Table 5. Hydroperiod summary, May 1985 through May 1987. Sites8 Year BIU BID TBU TBD 1 Days 170 52 66 118 Events 15 5 10 18 Days/Event 11 10 7 7 2 Days 231 33 66 181 Events 17 7 10 18 Days/Event 14 5 7 10 1&2 Days 401 85 132 299 Events 32 12 20 36 Days/Event 13 7 7 8 "See Table 1 for site abbreviations. Chabreck and Narcisse 1981) should also be questioned based upon the findings that Scirpus olneyi at TBU is consistently better than in the wetter BIU marsh. Herke (1979) and Herke et al. (1987) have documented decreased export and lower standing crops of important fisheries species in semi- impounded marshes. Ongoing studies of aquatic vegetation in both Toms and Big Island Bayou lake systems and in our new rock-weir study raise serious questions on the usefulness of semi- impoundment in the long term for creation of desirable aquatic vegetation such as Ruppia maritima. We have found that semi-impoundment reduces turbidity levels, allowing better aquatic vegetation growth and preventing lake desiccation (Larrick and Chabreck 1976), and that lakes in semi- impounded marshes have organic muck bottoms which Ruppia does not prefer. In addition, the best stands of Ruppia, Eleocharis parvula, and Echinochloa crusgalli are found in lakes with normal water-level cycles (low water in winter, dry in spring, wet in summer and fall). This data set is not complete or statistically analyzed as yet, but the field observations are very supportive. In addition, we are looking at the sedimentation rates in these marshes, and I predict that the sedimentation rates (both organic and mineral) will be less in the BI than in the TB system, which further encourages marsh loss. Upstream marshes exhibited lower total standing crops than downstream marshes in both watersheds. This may be due to lower nutrient and sediment inputs upstream. In watersheds such as these studied, the further upstream the marsh is, the more dependent upon rainfall it becomes. If this is indeed the case, then this may broaden the "streamside effect" concept of Mendelssohn et al. (1982). Mendlessohn et al. found that Spartina alterniflora was most productive and had higher maximum standing crops along the edges of bayous and became less so marshward. He concluded from his experimental work, including fertilizer studies, that the major reason was the 139 relative abundance of nutrients. He further attributed the difference in nutrient distribution to tidal flooding frequency; the more frequently flooded areas had more limiting nutrients as well as sediments transported to them. I propose that this same process is working on a much larger, tidally influenced, watershed scale. I further propose that this streamside effect on a watershed scale may be partially responsible for the marsh loss observed between watersheds, especially in the downstream areas between Toms and Big Island Bayous. Natural levees along tidally dominated watersheds become less pronounced upstream, reflecting the decreasing accumulation rate of sediments both away from the bayou and in the upstream direction. The accumulation rate is determined by suspended sediment loads and frequency of flooding. Support for this concept is twofold: 1) sediments forming natural levees in both systems are primarily mineral soils; these same minerals are much less abundant marshward and in the upstream direction. In the upstream marshes and in the marsh interior between Toms and Big Island Bayous very little mineral is found (less than 5% by dry weight); and 2) the tide nodal point in Toms Bayou is approximately at the point where natural levees disappear. The tide nodal point is the area along the tidal reach of a drainage system where the incoming tidal waters usually stop. Waters upstream of the nodal point, therefore, are not flushed as frequently as further downstream, but move back and forth with the tide. Flushing above the tide nodal point usually occurs during spring tides, rainfall events, and strong southeasterly fronts. CONCLUSIONS The conclusions of this study based upon data analysis and field observations are summarized: 1. Fixed-crest weirs are inadequate management tools because they: a. prevent storm-water runoff (21% to 56% increased hydroperiod), b. increase salinities in downstream sites, c. increase hydroperiods in upstream sites, and d. reduce maximum standing crops. 2. Downstream sites: a. Have higher plant diversities (Spartina patens dominates), and b. higher maximum standing crops, c. TBD flushed best with lowest salinity and highest standing crop. 3. In 1985 mean salinity at BID was high because of storm tides. 4. BIU had longest hydroperiod, lowest maximum standing crop. 5. TBU has higher standing crop and more Scirpus olneyi than does semi-impounded BIU. 6. Extended hydroperiod decreases maximum standing crop values in similar marsh types. 7. Increased salinities decrease both total and Scirpus olneyi standing crops in similar marsh types. ACKNOWLEDGMENT I would like to thank Ecosystem Research Unit Director Dr. Michael Duever and Paul J. Rainey Wildlife Sanctuary Manager Lonnie Lege for their valuable discussions on the marsh. 140 Elwood Perry is responsible for collecting most of the field data. Linda Meeder is the computer technician who did the statistical analyses and word processing. The Mellon Foundation provided the support for this study. LITERATURE CITED Chabreck, R.H. 1972. Vegetation, water, and soil characteristics of the Louisiana coastal region. La. State Univ. Agric. Exp. Stn. Bull. 664. 72 pp. Chabreck, R.H., and L.L. Narcisse. 1981. Effects of water depths on growth of three-cornered grass. Sea Grant Publ. LSU-T-81-002. 34 pp. Craig, N.J., R.E. Turner, and J.W. Day. 1979. Land loss in coastal Louisiana. Environ. Manage. 3(2):133-134. Duever, M.J. 1982. Hydrology-plant community relationships in the Okefenokee Swamp. Fla Sci. 45(3):171-176. Herke, W.H. 1979. Some effects of semi-impoundment on coastal Louisiana fish and crustacean nursery usage. Pages 325-346 in J.W. Day, Jr., D.D.Culley, Jr., R.E. Turner, and AJ. Mumphrey, Jr., eds. Proceedings: third coastal marsh and estuary management symposium. Baton Rouge, LA. Herke, W.H., E.E. Knudsen, P.A. Knudsen, and B.D. Rogers. 1987. Effects of semi-impoundment on fish and crustacean nursery use: evaluation of a solution. Pages 2562-2576 in Coastal Zone 87, WW Div, ASCE, Seattle, WA. Larrick, W.D., Jr., and R.H. Chabreck. 1976. Effects of weirs on aquatic vegetation along the Louisiana coast. Thirtieth Annu. Conf. Southeast Assoc. Game Fish Comm. Jackson, MS. 13 pp. Lynch, J.J., T. O'Neal, and D.W. Lay. 1947. Management significance of damage by geese and muskrats to gulf coast marshes. J. Wildl. Manage. ll(l):50-76. Meeder, J.F. 1986. Resource inventory and analysis of the Paul J. Rainey Wildlife Sanctuary and adjacent marshlands. First annual report: introduction and site descriptions. National Audubon Society, Abbeville, LA. 103 pp. Meeder, J.F. 1987. Variable effects of hurricanes on the coast and adjacent marshes: a problem for marsh managers. Pages 337-374 in Proceedings: fourth water quality and wetland management conference. New Orleans, LA. Mendelssohn, I. A., K.L. McKee, and M.T. Postek. 1982. Wetlands: ecology and management. Pages 223-243 in B. Gopel, R.E. Turner, R.G Wetzel, and D.F. Whagham, eds. First international wetlands conference. New Dehli, India, Sept. 1980. National Institute of Ecology, Jaipuri. O'Neil, T. 1949. The muskrat in the Louisiana coastal marshes. Louisiana Wildlife and Fisheries Commission, New Orleans. 159 pp. Ross, W.M., and R.H. Chabreck. 1972. Factors affecting the growth and survival of natural and planted stands of Scirpus olneyi. Twenty-sixth Annu. Conf. Southeast Assoc. Game Fish Comm., Knoxville, TN. 13 pp. Salinas, L.M., R.D. DeLaune, and W.H. Patrick, Jr. 1986. Changes occurring along a rapidly submerging coastal area: Louisiana, USA. J. Coastal Res. 2(3):269-284. Weather Bureau. 1970. Weather Bureau observing handbook No. 2. Substation observations. U.S. Government Printing Office:1970, 392-254/213. 77 pp. 141 THE EFFECTS OF WEIRS ON PLANTS AND WILDLIFE IN THE COASTAL MARSHES OF LOUISIANA1 Robert H. Chabreck and J. Andrew Nyman School of Forestry, Wildlife, and Fisheries Louisiana Agricultural Experiment Station Louisiana State University Agricultural Center Baton Rouge, LA 70803 ABSTRACT An important technique for management of tidal marsh, particularly in areas that will not support levees to form impoundments, is construction of weirs in drainage systems of the marsh. A weir resembles a low dam constructed of steel or wooden sheet pilings. The top or crest of the weir is normally placed 15 cm below the elevation of surrounding marsh, and water is allowed to flow back and forth across the structure. A weir reduces the rate of tidal flow and establishes a basin of water behind the structure that cannot recede below the crest; consequently, complete drainage of marshes and most ponds on low tide is prevented. With reduced tidal flow, streams carry less suspended materials, and water turbidity decreases. The basin of water held by the weir functions as a mixing bowl and stabilizes water salinity. Hundreds of weirs have been constructed along the Louisiana coast for marsh management. Studies comparing ponds and lakes behind weirs with those drained by free-flowing streams (control areas) disclosed that production of aquatic plants was 400% greater and more ducks were present in ponds behind weirs. Stabilized water levels improve access for trappers, hunters, and other visitors to a marsh. INTRODUCTION A weir is a sheet-piling bulkhead placed across a drainage outlet; it prevents complete drainage of the marsh during lowest tides but allows the marsh to be flooded normally at high tide. The crest of the weir is usually set 15 cm below the elevation of the marsh. The basin created by a weir is often referred to as a semi-impoundment or a partial impoundment (Herke 1971; Day et al. 1986). Weirs are used in coastal Louisiana for several reasons. Their primary purpose is to increase the amount of habitat available to wintering waterfowl. Extreme low tides are very common in the coastal marshes during winter months and may last 3 to 4 days. Free-flowing ponds are drained by north winds, but ponds upstream of weirs remain flooded and available to waterfowl (Chabreck 1968). Another major role of weirs is to maintain usable waterways through the marsh during the winter to provide trappers unrestricted access. Weirs increase production of aquatic plants, which are often high quality waterfowl foods. A fourth purpose of weirs is to favor the growth of muskrat (Ondatra zibethicus) and nutria (Myocastor coypus) foodplants. Diets of these economically important furbearers consist primarily of emergent vegetation of the genera Scirpus and Eleocharis. Weirs prevent excessive drainage and saltwater intrusion because of artificial channelization of the marsh. Saltwater intrusion often kills vegetation and causes marsh loss. Approved for publication by the Director of the Louisiana Agricultural Experiment Station as MS. 89-22-3116. 142 It is not clear exactly when weirs were first used in coastal Louisiana. Arthur (1928) made no mention of weirs in his book on Louisiana fur animals. However, O'Neil (1949) presented a irr.rsh management plan that called for low dams in access ditches to prevent drainage of the marsh but to allow high tide to flood it as usual. The purpose was to prevent vegetative changes in the marsh because of drainage by the ditches. Weir construction began in the 1940's or early 1950's, and we believe the period of most construction was 1955-65. During that time weirs were constructed throughout the coastal marshes, but many were concentrated in the brackish and intermediate marshes of the Deltaic Plain. The purpose of this paper is to review the effects of weirs on plants and wildlife in coastal Louisiana. We have limited our discussion to studies of fixed-crest weirs. Weirs used in conjunction with levees or with an adjustable height or a vertical slot are not included because comprehensive studies have not been conducted on the effects of these structures on plants and wildlife. We have also limited this review to studies in which a similar unmanaged marsh area (control) was compared to the marsh influenced by weirs. LITERATURE REVIEW Effects on Aquatic Vegetation Because abundant aquatic vegetation provides important food for ducks (Bellrose 1976), one of the purposes of weirs is to increase the amount of aquatic vegetation. Chabreck and Hoffpauir (1962) recorded the distribution of aquatic vegetation on Marsh Island in Iberia Parish and in Terrebonne and Lafourche Parishes. On Marsh Island, they found that the species composition of aquatic vegetation varied with water salinity. Drastic changes in salinity were associated with discharge from the Atchafalaya River. Managed ponds and control ponds were nearly identical in aquatic vegetation, salinity, and turbidity at the time of construction. On five of the subsequent nine sampling dates, salinities were relatively higher and widgeongrass (Ruppia maritima) was the dominant vegetation in managed ponds. On these sampling dates aquatic vegetation occurred at 11% of the stations in managed ponds and 6% of the stations in free-draining (control) ponds, and widgeongrass was the dominant species in the free -draining ponds on four of these occasions. On the other four sampling dates aquatic vegetation occurred at 3% of the stations in managed ponds and 4% of the stations in free-draining ponds. In managed ponds the dominant species was wild celery (Vallisneria spiralis) and in unmanaged ponds it was either wild celery, pondweed (Potamogeton foliosus), or dwarf spikerush {Eleocharis parvula). The study areas in Terrebonne and Lafourche Parishes were sampled only once and contained weirs of various ages. Widgeongrass occurred at 41% of stations in managed ponds and 11% of the stations in unmanaged ponds. There was no relationship between the age of the weirs and the occurrence of widgeongrass. In the Terrebonne-Lafourche area, turbidities in managed and unmanaged ponds were less than 25 ppm. On Marsh Island, considerable variations in turbidity were noted throughout the study, but generally turbidity was less in managed ponds than unmanaged ponds. Little difference in salinity was found between managed and unmanaged ponds in either area. At the Biloxi Marsh Tract in St. Bernard Parish, the Louisiana Wildlife and Fisheries Commission (1964-65) found 10.7 ml of aquatic vegetation per sample in managed ponds and 2.4 ml in unmanaged ponds in 1964; and 22.4 ml in managed ponds and 5.1 ml in unmanaged ponds in 1965. No difference was noted in turbidity, and the difference in water salinities (4.3 ppt in managed 143 ponds vs. 5.3 ppt in unmanaged ponds) was small enough to suggest that the increase in aquatic plants resulted from a reduction in tidal action on the floors of the managed ponds. Larrick and Chabreck (1978) investigated aquatic vegetation at three locations in coastal marshes that were intermediate to brackish on Marsh Island, saline at the Wisner Wildlife Management Area in Lafourche Parish, and brackish to saline in Jefferson and Plaquemines Parishes 40 km north of Grand Isle. The amount of aquatic vegetation was lowest in the saline marsh, where aquatic vegetation was found at 1.7% of the sample stations in the managed ponds and at none of the stations in the unmanaged ponds. In the brackish to saline marsh, much of which had been modified by dredging, aquatic vegetation occurred at 18% of the stations in managed ponds and only 0.5% of the stations in the unmanaged ponds. In the intermediate to brackish marsh, aquatic vegetation occurred at 74% of the stations in managed ponds and 43% of the stations in unmanaged ponds. Larrick (1975) recorded salinity and turbidity in the same ponds at the time vegetation samples were taken. Although salinities varied among areas, he reported similar salinities in managed and unmanaged ponds within areas. In the brackish to saline area turbidity was slightly higher in managed ponds (30.3 ppm vs. 21.6 ppm), but in the saline marsh area and the brackish to intermediate area the turbidities were slightly lower in the managed ponds (31.0 ppm vs. 36.5 ppm and 40.0 ppm vs. 51.2 ppm, respectively). Herke (1971) reported that weirs reduced the rate at which salinity changed, so that the extreme low and extreme high salinities were moderated. This resulted in higher salinities behind weirs when salinities were decreasing, and lower salinities behind weirs when salinities were increasing. When salinities were stable, there was usually no difference in salinity between managed and unmanaged ponds. Effects on Emergent Vegetation Chabreck and Hoffpauir (1962) recorded species composition for 5 years following construction of weirs on Marsh Island. Although drastic differences were noted among years, the marsh affected by weirs remained similar to unmanaged marsh throughout the study. Chabreck (1968) sampled these same eight transects 5 years later and found differences between the managed marsh and unmanaged marsh. In managed high marsh, initially characterized by marshhay cordgrass (Spartina patens) and black rush (Juncus roemerianus), dwarf spikerush replaced much of the black rush. Black rush is associated with higher, well-drained marshes and has little direct value to wildlife. Spikerush, associated with lower, moister areas, is a valuable food for waterfowl and nutria (Martin and Uhler 1939; Chabreck et al. 1981). Larrick (1975) examined marsh vegetation at the same three areas where Larrick and Chabreck (1978) later studied aquatic vegetation. The plant species composition differed greatly among marsh types because of differences in salinity. The plant communities in all three areas were very similar in managed and unmanaged marshes. The increase in spikerush and decline in black rush noted by Chabreck (1968) in managed brackish to intermediate marsh was not noted by Larrick (1975). In the saline and brackish to saline areas, unmanaged marsh had significantly more vegetative cover than managed marsh, 64.6% vs. 42.4% and 80.2% vs. 75.3%, respectively. In the brackish to intermediate marsh area, the managed marsh had significantly more vegetative cover than unmanaged marsh (89.7% vs 86.8%). In all three areas the free-soil-water salinities were lower in managed marsh than in unmanaged marsh. In the upper Barataria Basin, Hoar, (1975) studied the effects of weirs on several soil characteristics. Of particular interest were his data on soil redox potential, dissolved hydrogen 144 sulfide, and soil water salinity. The redox potential of a soil can be used as a measure of the stress imposed on plants by waterlogging. Reduction potentials in waterlogged soils range from +350 mV to -350 mV. Conditions that produce +350 mV to -125 mV make nitrogen and phosphorus more available to plants than in drained, oxidized soils (Mitsch and Gosselink 1986). However, if the redox potential of the soil becomes highly reducing, specialized anaerobic bacteria will convert sulfate to hydrogen sulfide, which can be toxic at high concentrations (Patrick and DeLaune 1977). Hoar (1975) showed that hydrogen sulfide production should occur at a shallower depth in managed marshes than in unmanaged marshes. But Hoar did not detect a difference between the concentration of dissolved hydrogen sulfide in the managed marsh and in the unmanaged marsh. He did not evaluate the effect on plant growth of the slight difference in redox potential in the upper layer of soil. Hoar (1975) noted that the free -soil-water salinities fluctuated with water salinities. During his study there was an unusually large amount of rainfall, and the water in the upper end of the Barataria Basin was fresher than during the previous year. The weirs buffered incoming fresher waters with the slightly saltier water present from the previous year. As a result, free -soil-water salinities in marsh affected by weirs averaged 6.0 ppt and in marsh unaffected by weirs averaged 5.6 ppt. Effects on Waterfowl Chabreck (1968) reported that migrant ducks concentrated in managed ponds on Marsh Island because they were attracted by the abundance of food and water. During January, February, and March, low tides ranged from 0.33 m to 0.43 m below sea level, and Chabreck and Hoffpauir (1962) computed that a -0.67 m tide would drain 2.4% of the managed ponds and 84.0% of the unmanaged ponds. Spiller and Chabreck (1975) made monthly aerial counts of waterfowl in nine managed marsh ponds and nine unmanaged ponds in upper Barataria Basin (Figure 1). Seventy-four percent of the birds counted were present during winter months, 75% of which were found in managed ponds. The greatest difference in duck use between areas was in December and February and was attributed to the lack of water in unmanaged ponds. Effects on Non-game Birds Spiller and Chabreck (1975) also compared use of managed ponds and unmanaged ponds by non-game birds (mostly wading birds, gulls, and terns; Figure 2). Most of these birds feed on small fish and crustaceans and are therefore dependent on water to provide suitable habitat. Most of the non-game birds counted throughout the year were counted in winter, during which time more were in the managed ponds than in the unmanaged ponds. This difference was attributed to the lack of water in the unmanaged marsh. The authors reported that during other winter months, the non-game birds stayed in the unmanaged ponds as they drained because the marine organisms on which the birds fed became concentrated in pools. As the north winds continued, water drained from these ponds and the birds moved to the managed ponds, which still contained food and water. When the north winds abated, water returned to the unmanaged areas and the birds dispersed. Because the cycles usually occur over a period of several days, no significant difference in use by non-game birds was detected between the managed and unmanaged areas during the other winter months, even though the birds may have used one type more than the other at different times. 145 t/> C9 3.5_ 3.0_ 2.5_ 2.0_ 1.5_ 1.0_ I 'I 'I I |l I I WEIRS CONTROLS J F M -i — ( — ^i — * A M J J MONTH Figure 1. Number of ducks and coots per acre for areas influenced by weirs and controls (Spiller and Chabreck 1975). 146 ,4 2.2_ - 2.0- - 1.8_ sa 16_ O u 2 1.4. O 1.2. Z it. o .•_ •4_ ,2« .WIIRS CONTROLS -i — i — i — i — r~~i — i — i — i — « — r—T JFMAMJJASOND MONTH Figure 2. Number of non-game birds per acre for areas influenced by weirs and controls (Spiller and Chabreck 1975), 147 Effects on Mammals Spiller and Chabreck (1975) compared abundance of selected wild mammals in upper Barataria Basin in nine areas influenced by weirs and in nine control areas. Indices were used to compare populations of nutria, muskrat, and swamp rabbit (Sylvilagus aquaticus). Two indices were used to compare muskrat populations. One indicated higher populations in managed marshes and the other indicated higher populations in unmanaged marshes, but neither was statistically different. Three indices were used to compare nutria abundance and the results indicated no difference between managed and unmanaged marshes. Only one index was used to compare swamp rabbit populations. The index indicated more rabbits in managed marsh on all sampling dates, but on only one date was it statistically different. Small mammal populations were compared by using removal trapping. The only small mammal collected was the rice rat (Oryzomys palustrus). Fifty-five percent of the rice rats caught were caught in managed marsh, but this was not statistically significant. CONCLUSIONS Previous research clearly indicates the positive effect of weirs on aquatic vegetation in most marshes. Two areas where weirs have not consistently produced abundant aquatic vegetation are saline marshes and on Marsh Island, where salinities fluctuated drastically in response to discharge from the Atchafalaya River. In all areas, mean salinities in managed ponds and unmanaged ponds were similar, but turbidities were only slightly lower in managed ponds. This indicates that weirs may increase the occurrence of aquatic vegetation by modification of other factors. The other possible factors related to weirs are reduced tidal scouring, reduced salinity fluctuations, and stabilized water levels. Because of a great difference in the amount of aquatic vegetation between managed and unmanaged ponds in an area drastically altered by artificial channelization, we believe that the reduction in tidal scouring may be the main mechanism by which weirs affect aquatic vegetation. We also believe that stabilization of salinity is important. Previous researchers have reported that weirs slowed the rate at which salinities changed, but unfortunately no data are available to compare the magnitude of salinity fluctuations in managed and unmanaged ponds. Weirs apparently do not have a large effect on the species composition of emergent plant communities. Only one publication reported a difference in the structure of plant communities associated with weirs and control areas, and this difference was not evident when the areas were sampled 7 years later. No direct data are available to assess the influence of weirs on plant productivity. Limited data indicate that hydrogen sulfide production should occur at a shallower depth in managed marsh, but dissolved hydrogen sulfide concentrations were the same in managed and unmanaged marshes. Therefore, some mechanism was removing hydrogen sulfide as it was produced in both areas, possibly through tidal flushing, or by precipitation with ferrous iron. From these data we conclude that plant productivity was similarly affected by hydrogen sulfide in marsh affected by weirs and marsh not affected by weirs. The direct effect of the slightly lower redox potential on plant productivity was not evaluated. In one study, vegetative cover was measured at three sites; at two sites more cover was found in control areas, and at the other site the marsh influenced by weirs had more cover. From these data we conclude that either weirs have no effect on the amount of vegetative cover, or that cover varies in relation to factors associated with the location. 148 A large portion of the North American continental waterfowl population winters in coastal Louisiana (Bellrose 1980). Because weirs influence the water levels in ponds during the winter and increase the amount of aquatic vegetation, they increase the amount and quality of habitat available to wintering waterfowl. Although long overlooked, the quality of the wintering habit it could be extremely important to waterfowl populations (Fredrickson and Drobney 1979). The quality of the wintering ground influences the health of the birds, winter survival rates, and subsequent reproductive success (Heitmeyer and Fredrickson 1981; Krapu 1981; Kaminski and Gluesing 1987). Non-game birds were more abundant in ponds influenced by weirs when free-draining ponds had no water. While unmanaged ponds were draining, birds preferred these areas because food was concentrated. When water conditions were similar in managed and unmanaged ponds, birds used each type equally. Because numbers of non-game birds are highest in the winter, when unmanaged ponds are drained much of the time, weirs improve habitat quality for many non-game birds. Weirs have little effect on the abundance of certain mammals. Muskrats, nutrias, and swamp rabbits appeared to be more abundant in areas influenced by weirs than in unweired areas, but the results were not conclusive. The biggest impact weirs have on mammal numbers may be in drought years when freshwater can be a limiting factor, but, because there are no data on mammal populations during unusually dry years, their value to wildlife at these times is unknown. LITERATURE CITED Arthur, S.C. 1928. The fur animals of Louisiana. La. Dep. Conserv. Bull. 18. 433 pp. Bellrose, F.C. 1980. Ducks, geese and swans of North America. Stackpole Books, Harrisburg, PA 504 pp. Chabreck, R.H. 1968. Weirs, plugs and artificial potholes for the management of wildlife in coastal marshes. Pages 178-192 in J.D. Newsom ed. Proceedings: first coastal marsh and estuary management symposium. Louisiana State University, Div. Continuing Education, Baton Rouge. Chabreck, R.H., and CM. Hoffpauir. 1962. The use of weirs in coastal marsh management in Louisiana. Proc. Annu. Conf. Southeast Game Fish Comm. 16:103-112. Chabreck, R.H., J.R. Love, and G. Linscombe. 1981. Foods and feeding habits of nutria in brackish marsh in Louisiana. Proc. Worldwide Furbearer Conf. l(l):531-543. Day, J.W., Jr., R. Costanza, K. Teague, N. Taylor, G.P. Kemp, R. Day, and R.E. Becker. 1986. Wetland impoundments: a global survey for comparison with the Louisiana coastal zone. La. Dep. Nat. Resour., La. Geol. Surv. Div., Baton Rouge. Fredrickson, L.H., and R.D. Drobney. 1979. Habitat utilization by postbreeding waterfowl. Pages 119-131 in T. Brookhout, ed. Waterfowl and wetlands - an integrated review. Proc. 1977 S)Tnp. Northcent. Sec, Wildl. Soc, Madison, WI. 152 pp. Heitmeyer, M.E., and L.H. Fredrickson. 1981. Do wetland conditions in the Mississippi Delta hardwoods influence mallard recruitment? Trans. N. Am. Wildl. Nat. Resour. Conf. 46:44-57. Herke, W.H. 1971. Use of natural, and semi-impounded, Louisiana tidal marshes as nurseries for fishes and crustaceans. Ph.D. Dissertation. Louisiana State University, Baton Rouge. 26-4 pp. 149 Fioar, R.J. 1975. The influence of weirs on soil and water characteristics in the coastal marshlands of southeastern Louisiana. M.S. Thesis. Louisiana State University, Baton Rouge. 94 pp. Kaminski, R.M., and E.A Gluesing. 1987. Density- and habitat-related recruitment in mallards. J. Wildl. Manage. 51(1):141-148. Klrapu, G.L. 1981. The role of nutrient reserves in mallard reproduction. Auk 98:29-38. L^rrick, W.D. 1975. The influence of weirs on the vegetation of coastal marshes of Louisiana. M.S. Thesis. Louisiana State University, Baton Rouge. 103 pp. Larrick, W.D., and R.H. Chabreck. 1978. Effects of weirs on aquatic vegetation along the Louisiana coast. Proc. Annu. Conf. Southeast Game Fish Comra. 13:100-115. Louisiana Wildlife and Fisheries Commission. 1964. Pages 74-83 in Annual progress report, W- 29-R-II. New Orleans. Louisiana Wildlife and Fisheries Commission. 1965. Pages 94-% in Annual progress report, W- 29-R-II. New Orleans. Martin, AC, and F.N. Uhler. 1939. Food of game ducks in the United States and Canada. U.S. Dep. Agric. Tech. Bull. 634. Mitsch, W.J., and J.G. Gosselink. 1986. Wetlands. Van Nostrand Co. Inc., New York. 539 pp. O'Neil, T. 1949. The muskrat in the Louisiana coastal marshes. Publ. Fed. Aid Sec., Louisiana Wildlife Fisheries Commission. 152 pp. Partrick, W.H., and R.D. DeLaune. 1977. Chemical and biological redox systems affecting nutrient availability in the coastal wetlands. Geosci. Man 18:131-137. Spiller, S.F., and R.H. Chabreck. 1975. Wildlife populations in coastal marshes influenced by weirs. Proc. Annu. Conf. Southeast Assoc. Game Fish Comm. 29:518-525. 150 WEIRS AND THEIR EFFECTS IN COASTAL LOUISIANA WETLANDS (EXCLUSIVE OF FISHERIES) R.E. Turner, J.W. Day, Jr., and J.G. Gosselink Coastal Ecology Institute Center for Wetland Resources Louisiana State University Baton Rouge, LA 70803 ABSTRACT Weirs have been used for water control in coastal wetlands since the mid-1950's. They were originally proposed for waterfowl management and are now used for salinity and erosion (wetland loss) control. But there are very few field studies of how well weirs work to retard conversion of wetland to open water, and no published studies (peer-reviewed articles in scientific journals) on their impacts except for how they influence waterfowl and fish and invertebrates. Here we summarize the unpublished data results from conferences, symposia, and eight unpublished student theses. Water salinity in weired and adjacent unweired marshes is, in general, the same with regards to monthly mean, maximum, or minimum salinities. Weirs cause higher mean water levels, leading to significant soil chemistry changes which may be detrimental to vascular plants and lead to higher rates of marsh breakup. Aquatic vegetation in ponds with weirs may be significantly greater than that found in ponds without weirs. Overwintering waterfowl are apparently attracted to this increased aquatic vegetation. However, from spring to fall, waterfowl and non-game bird densities are the same, or lower, behind weirs compared to control marshes, as are mammal density and hunter usage. INTRODUCTION Water level management is a common wetland management approach. Fixed crest weirs are one specific water level management tool introduced in the 1950's to benefit waterfowl (Ensminger 1963; Cowan et al. 1988). Today, weirs and other water level control devices are commonly built with the hope of reducing coastal wetland loss rates, increasing or changing plant density and composition, sustaining or building up animal populations, and maintaining marsh sed. nentation rates. Since most of the well-documented, high coastal wetland loss rates are related t< artificial hydrologic changes (e.g., Swenson and Turner 1987; Turner 1987; Turner and Cahoon 1987) it is not unexpected that suggestions for corrective measures focus on water level management. The rather severe complications of dramatic landscape changes (Turner 1988) and limited management tools for natural resource managers (at a Federal, State, and landowner level) often result in a resurrection of past practices to adapt to new purposes. At the same time we have very few documented studies of the long-term impacts of any water level management practice in a diversity of coastal environments. Fixed-crest weirs are an exception in that they have been studied in a credible manner, but the results of those studies are generally unpublished. Further, the studies, when cited in permit applications, are often used to support activities inconsistent with the obser- vations discussed in the original report. It is the purpose here to review the original reports on fixed crest weirs and to summarize their apparent impact on water quality, soils, plants, and animals. 151 METHODS We examined the results from eight graduate student master's theses prepared at Louisiana State University by Burleigh (1966), Weaver (1969), Wengert (1972), Spiller (1974), Hoar (1975), Larrick (1975), Carney (1977), and Olinde (1977) and combined them with the related field studies of Chabreck and Hoffpauir (1962), Herke (1971, 1977), and Chabreck et al. (1979). Fishery aspects were not examined because Herke (1971, 1977, 1979) and Herke et al. (1987; also see Herke et al. in this proceedings) have reviewed them extensively. We divided our analyses into the effect of weirs on water quality, soils, vegetation, and animals. The study sites are shown in Figure 1 and the basic study results are outlined in Table 1. Four study sites in coastal Louisiana were used by these investigators to study the effects of weirs. The most extensively studied site is at Marsh Island, near the terminus of the Atchafalaya River. Other sites are in Terrebonne, Barataria Bay, and at the Biloxi Marsh Public Shooting Grounds bordering Lake Borne. Some investigators studied marshes as clusters with or without weirs, averaged the data for each cluster, and then made comparisons of each cluster. Other studies measured parameters inside a weired marsh and just outside. Many additional data were collected besides those discussed here (Table 2). The only data on fish and invertebrates appear in the reviewed scientific literature, and the only data on aquatic vegetation and overwintering waterfowl appear in the unreviewed proceedings of conferences or symposiums. We found no contradictions between our observations and summaries and those in the student theses or with conclusions based on these theses appearing in symposia. The quotation of these theses in marsh management permit applications are, however, often different from our and the students' observations. The value of this review, therefore, is to illuminate and summarize the diverse and generally sparsely used data in these student theses. Salinity values of marshes with and without weirs were calculated as cluster averages. Individual marsh measurements are also reported if salinity was measured just inside and outside of the weir. A histogram count of frequency versus salinity differences was then computed to discern the range of differences resulting from weirs, and whether or not the differences were skewed toward higher or lower salinities in weired marshes. In addition to the above summaries, we examined the formation of new ponds in the Biloxi Marsh Public Shooting Grounds between 1955 and 1978. The geographical information system at the Louisiana Department of Natural Resources, Coastal Management Section was used to generate maps of various parameters, including, ponds 0-20 ha in size. The ponds appearing on 1955 and 1978 7V2-minute quadrangle maps were identified inside and outside the shooting grounds. The shooting grounds constitute about one-quarter of the marsh within the quadrangle maps. RESULTS Table 2 is a summary of the various results mentioned in the papers consulted. Here we discuss results in terms of water quality, soil conditions, vegetation, and animal usage. Water Quality Salinity comparisons were common. Salinities ranged from 0 to 23 ppt, and the salinity differences between marshes with and without weirs were inconsistent. Sometimes the salinity behind weirs was higher and sometimes lower than in nearby marshes or in water bodies in control areas. A comparison of salinities in marshes with and without weirs is shown in Figure 2. In 152 e 2 a "O ss "9 a u a >> 3 a o t s 'Z 153 Table 1. Source of data used in this analysis of marshes with weirs and nearby control marshes without weirs (Carney 1977 included for discussion purposes). Water salinity range (ppt) Sampling frequency Other data8 Land Source 6-17 Spring-fall Fish; Wat Public6 Burleigh 1966 0-6 Seasonal Veg; Bird LL&EC Carney 1977 (impounded marsh vs. marsh with weirs) 0-8 (Marsh I.) Seasonal Monthly Wat; Veg Publicd LL&EC Chabreck and Hoffpauir 1962; Chabreck et al. 1979 0-14 Weekly Lev; Fish Publicb-d Herke 1971, 1977 2-10 Monthly Soil; Wat LL&EC Hoar 1975 0-23 Seasonal Veg; Lev; Wat; Soil LL&EC Larrick 1975 0-6 Bi-monthly Lev LL&EC Olinde 1977 (Stn. 0,1) Similar to Hoar (1975) and Larrick's (1975) site 2 Monthly Bird; Hunt; Mam LL&EC Spiller 1975 1-9 Monthly Wat; Fish Publicd Weaver 1969 0-13 Weekly from spring-summer Fish Publicd Wengert 1972 (areas 1,2,3,4) aBird=seasonal survey of waterfowl/non-game birds Fish = fish and/or invertebrates Hunt = hunter's usage Lev = water level Mam = mammals (nutria, rats, muskrat, raccoon, deer and "small mammals") Soil = Eh, pH, and/or salinity Veg = vegetation Wat = water quality, including oxygen, turbidity, and pH bBiloxi Marshland Public Shooting Grounds. cLouisiana Land and Exploration Company, Inc. dMarsh Island Wildlife Refuge, Louisiana Wildlife and Fisheries Commission. 154 Table 2. Interaction matrix of effects of weirs on wetland ecosystem. Data from experiments with inadequate control sites are not included. Parameter Higher No change Lower Source Water salinity Water oxygen Turbidity Soils Eh pH salinity organic content Pond siltation rate Vegetation coverage in ponds in marsh X X Weaver 1969; Floar 1975; Herke 1977 (Biloxi Marsh) Chabreck and Hoffpauir 1962 (Marsh I.); Burleigh 1966; Larrick 1975 (sites 1,2,3); Olinde 1977 Wengert 1972 (areas 1,23,4 combined); Herke 1977 (Marsh I.) Burleigh 1966; Hoar 1975 Weaver 1969; Larrick 1975 (sites 2,3) Chabreck and Hoffpauir 1962 (Marsh I.); Larrick 1975 (site 1); Hoar 1975 - X Hoar 1975 - X Hoar 1975 X - Larrick 1975 (sites 1,2,3) - - Hoar 1975 X - Hoar 1975 X Chabreck et al. 1979 Larrick 1975 (sites 1,3); Chabreck and Hoffpauir 1962 Larrick 1975 (site 2) Larrick 1975 (site 3) Larrick 1975 (sites 1,2); see Table 5a (Continued) 155 Table 2. (Concluded). Parameter Higher No change Lower Source Waterfowl density summer X fall X winter X - spring X Annual average X Non-game birds density summer X fall X winter X - spring X Annual average X Mammal density muskrat X nutria X rabbits X small mammals X Hunter usage X Spiller 1975a Spiller 1975° Spiller 1975a Spiller 1975a Spiller 1975a Spiller 1975 Spiller 1975 Spiller 1975 Spiller 1975 Spiller 1975 Spiller 1975 Spiller 1975 Spiller 1975 Spiller 1975 Spiller 1975 aCarney (1977) reported similar results for an impounded marsh compared to a marsh with weirs; the vegetation was lower with more hydrologic restriction and the waterfowl density higher only during the winter. general there was little difference between weired and unweired marshes, although there was a slight skew in the frequency distribution toward higher (<2 ppt) values behind weirs. Such a small range of differences (Figure 2a) and the consistent 1:1 relationship of salinity in areas with and without weirs (Figure 2b) indicates that the weirs sampled have little impact on marsh salinity. One might also assume that weirs with less impact on water level (slotted weirs, for example) would have even less effect. Compared to control marshes, turbidity was slightly lower in weired marshes in three studies, but the same in three other studies. Water dissolved oxygen concentration was unchanged by weirs in two studies. Soils Weirs had an appreciable impact on soil pH and Eh in the only study that recorded these parameters (Hoar 1975). Soil Eh is an indicator of soil flooding, something which the weir and any flood control device should change. Higher soil flooding (i.e., longer duration or greater 156 R o O 45- 40- 35- 30- 25- 20- 15- 10- 5- 0- -3.5 -3 -2.5 -2 -1.5 -1 -.5 0 .5 1 1.5 Difference Control- Weired Marsh PPT 2.5 10 15 20 Control Marsh PPT Figure 2. Comparison of water salinity in control marshes and marshes with weirs for the study sites listed in Table 1. Data are averages for those studies with grouped control (natural marshes) and experimental (with weirs) marshes. Data are for individual sites if samples were taken just inside and outside of the weirs. frequency) leads to lower soil oxidation reduction potentials, which are measured by Eh. Although soil scientists might measure soil Eh differently, or treat the field data differently now (for example, normalize the data by adding +244 mV to the raw field readings that Hoar obtained), the relative differences among or between marshes with and without weirs are seasonal and significant. Summer values were lower than in any other season and values in marshes with weirs were much lower (up to 150 mV lower) than in marshes without weirs. Low Eh values, such as those 157 measured by Hoar in the marshes with weirs, are indicative of significant waterlogging, or stress, on the plants (Burdick and Mendelssohn 1987). In other wetland studies with increased and decreased waterlogging, the plants respond with less or more plant growth, respectively (see Table 3). The implication is that the increased flooding caused by a weir 6 inches below marsh level may be a significant physiological stress on the plants, perhaps enough of a stress to result in plant death. Soil salinity was slightly higher behind weirs in one study, but unchanged in another. The soil organic content of marshes with weirs was apparently unchanged by weirs. Chabreck et al. (1979) reported a significant decrease in sedimentation rate over several years for ponds in marshes with weirs, as compared to ponds without weirs. In fact, he noted that weirs may "have actually functioned to reduce the "rate" of sediment deposition. Lower net sedimentation rates in areas with weirs indicates fewer flooding events and lower transport of suspended sediments into marshes. They do not support the idea that tidal scouring is a significant contributor to marsh breakup. On the contrary, tides bring suspended sediments into a marsh, sustaining both a healthy soil Eh profile and positive accretion rate. Vegetation and Marsh Degradation Weirs result in more submerged aquatic vegetation in low salinity marshes. The same is not true for emergent vegetation, which was unchanged by weirs at Marsh Island, but was lower at three other sites (Table 2). At the Biloxi Marsh Public Shooting Ground, the rate of formation of new ponds from 1955 to 1978 was 3 times higher inside the marsh management area compared to the surrounding marsh (Table 4). High vegetation losses in marshes with weirs were also apparent in the low salinity marsh studied by Larrick (1975; 3-12 ppt; Table 5). These results are also consistent with the results of Chabreck and Hoffpauir (1962), who presented data indicating that emergent vegetation gives way to submergent vegetation when flooding increased (Table 2). Gosselink (1984) reported similar results for impounded marshes in the Chenier Plain data. The negative effect of weirs on emergent vegetation is consistent with results from experimental studies in other coastal marshes (Table 3) and soil Eh data (Figure 3) and the decrease in sedimentation rate behind weirs at Marsh Island (Chabreck and Hoffpauir 1962). Our interpretation is that the weirs result in increased flood duration, fewer flooding events, and subsequent detrimental stresses on emergent vegetation resulting from waterlogging and from a decreased ability of plants to adjust their vertical position in a sinking landscape (caused by subsidence and sea-level rise). Animals The only difference in the number of animals in marshes with and without weirs was the higher number of overwintering waterfowl in marshes with weirs. This is attributable to the increased amount of submerged vegetation and higher water levels in winter. Otherwise there were no statistically significant differences in resident species of mammals, non-game bird species, or waterfowl. Hunter usage in areas with and without weirs was the same, indicating that weirs did not encourage utilization of ponds by animals or hunters. Herke (1979) has summarized the various influences of weirs on coastal Louisiana fish and crustaceans. Weirs present a physical and ethological barrier to fish migration; adults may congregate near the weir. Subsequent research has substantiated his concerns that coastal migratory species and resident estuarine species are adversely affected. The effects of weirs on 158 Table 3. Examples of the responses of coastal wetland communities to altered hydrologic regimes. Experiment Purpose Result Source 1. Streamside plants moved to lower elevation in the marsh (in pots; LA) 2. Inland plants moved to higher elevation in the marsh (LA) 3. Drainage tiles added to inland marsh (GA) 4. Belowground water movement blocked (LA) 5. Aboveground water movement blocked (LA) 6. Above- and belowground water movement blocked (LA) 7. Above- and belowground water movement blocked (NC) 8. Impoundment levee broken (FLA) Increase flood height and duration Decrease flood height and duration Increase belowground water movement Reduce belowground horizontal flow, increase soil flooding Greatly reduce sheet flow and increased flooding Greatly reduce waterflow and increased belowground flooding Greatly reduce sheetflow and increase below- ground flooding Increase above and belowground waterflow Lower standing crop, plant height, and density Higher plant biomass, height, and density Higher plant biomass, lower sulfide, higher iron Reduced Eh and flower density Mendelssohn et al. 1982 Variable Eh change; negligible sedimentation Reduced Eh, sedimentation rate, and tasseling Reduced Eh, plant growth, and sedimentation rate Dying vegetation recovered Mendelssohn et al. 1982 King et al. 1982; Wiegert et al. 1983 Turner et al. 1985 Turner et al. 1985 Turner et al., 1985 Mendelssohn and Seneca 1980 Gilmore et al. 1981 9. Ditched marshes filled in (DEL) Re-establish original hydrology Vegetation recovered, soil subsidence reversed Stearns et al. 1940 159 Table 4. Number of ponds 0-20 ha in Biloxi Marsh in 1955 and 1978 and changes. Number % net new 1955-78 Condition Ponds in 1955 1955 ponds filled in by 1978 New ponds in 1955-78 Total ponds 1978 % filled in 1955-78 With weirs Control area 20 73 1 4 16 22 35 91 75.0 25.0 5.0 5.0 Table 5. Percentage of vegetation in three areas with control and weired marshes (adapted from Larrick 1975). Area studied Vegetation Jefferson/Plaquemines Parishes Lafourche (Wisner Wildlife Management Area) Marsh Island Wildlife Refuge Ponds with weirs control difference Marsh with weirs control difference 18.1 0.5 + 17.6 75.3 80.2 -4.9 1.7 0.0 + 1.7 42.4 64.7 -22.3 70.7 42.7 +28.0 89.7 86.8 +2.9 fish and crustaceans will not be duplicated here, since this is the subject of a related paper presented at this meeting (see Herke et al.). DISCUSSION The basic potential direct effect of weirs is to stabilize water levels. This stability leads to longer periods of marsh flooding. Water quality is sometimes different behind weirs, compared to water quality in unweired marshes. Submerged vegetation increases as a result of deeper flooding, and overwintering waterfowl are attracted to either the increased water levels or submerged vegeta- tion. Densities of resident animals are relatively unaffected by this type of water level management. However, the long-term health of the marsh which animals including overwintering waterfowl depend on may be seriously compromised if vegetation is as stressed as it appears to be. 160 n £ n CO * -200 A W 4> I? -400 • Average Eh Control Sites O Average Eh Weired Sites — i— 8 10 2 4 6 Month Figure 3. Seasonal soil Eh in marshes with and without weir data (from Hoar 1972). 12 Fixed-crest weirs are relatively innocuous compared to more intensive structural approaches (see Cowan et al. 1988 for a discussion of the various types of structural approaches to water level management). If a little bit of extra flooding has this impact on vegetation, then additional serious flooding, especially during summer, may lead to even higher rates of wetland loss through either increased waterlogging or decreased sedimentation. A management adaptation might be to have the least restrictive hydrologic changes during summer when soil oxidation and reduction potentials are naturally the lowest. This particular management approach was implemented coast-wide before appropriate comparative studies were initiated to determine the long-term consequences. Fortunately, the student theses cited herein, although unreviewed in the scientific literature and perhaps largely ignored as a result, are a valuable resource of information on natural marshes and the impacts of water level management. ACKNOWLEDGMENT This effort was supported by the Louisiana Sea Grant Program and the Department of Marine Sciences, Louisiana State University. Ms. S. Kaswadji greatly helped to track down literature citations and prepare figures. LITERATURE CITED Burdick, D.M., and I.A Mendelssohn. 1987. Waterlogging responses in dune, swale and marsh populations of Spartina patens under field conditions. Oecologia (Berl.)74:321-329. Burleigh, J.G. 1966. The effects of Wakefield weirs on the distribution of fishes in a Louisiana saltwater marsh. M.S. Thesis. School of Forestry and Wildlife Management, Louisiana State University, Baton Rouge. 68 pp. 161 Carney, D.F. 1977. An evaluation of waterfowl habitat improvement practices in a southeastern Louisiana freshwater marsh. M.S. Thesis. School of Forestry and Wildlife Management, Louisiana State University, Baton Rouge. 78 pp. Chabreck, R.H. 1968. Weirs, plugs and artificial potholes for the management of wildlife in coastal marshes. Pages 178-192 in J.D. Newsom, ed., Marsh and estuary management symposium. Louisiana State University, Division of Continuing Education, Baton Rouge. Chabreck, R.H., and CM. Hoffpauir. 1962. The use of weirs in coastal marsh management in Louisiana. Proc. 16 Annu. Conf. Southeast. Game Fish Comm. 16:103-112. Chabreck, R.H., R.J. Hoar, and W.D. Larrick, Jr. 1979. Soil and water characteristics of coastal marshes influenced by weirs. Pages 129-146 in J.W. Day, Jr., D.D. Culley, Jr., R.E. Turner, and A.J. Mumphrey, Jr., eds. Third coastal marsh and estuary management symposium. Louisiana State University, Division of Continuing Education, Baton Rouge. Cowan, J.H., Jr., R.E. Turner, and D.R. Cahoon. 1988. Marsh management plans in practice: do they work in coastal Louisiana? Environ. Manage. 12:37-53. Ensminger, A.B. 1963. Construction of levees for impoundments in Louisiana marshes. 17th Annu. Conf. Southeast. Assoc. Game Fish Comm. 17:440-446. Gilmore, R.G., D.W. Cooke, and C.J. Conohoe. 1981. A comparison of the fish populations and habitat in open and closed salt marsh impoundments in east-central Florida. Northeast Gulf Sci. 5:25-37. Gosselink, J.G. 1984. The ecology of the deltaic marshes of the Louisiana coast: a community profile. U.S. Fish Wildl. Serv. FWS/OBS-84/09. 134 pp. Herke, W.H. 1971. Use of natural, and semi-impounded, Louisiana tidal marshes as nurseries for fishes and crustaceans. Ph.D. Dissertation. Louisiana State University, Baton Rouge. 264 pp. Herke, W.H. 1977. Life history concepts of motile estuarine-dependent species should be re- evaluated. W.H. Herke, 555 Staring Lane, Baton Rouge, LA 101 pp. Herke, W.H. 1979. Some effects of semi-impoundment on coastal Louisiana fish and crustacean nursery usage. Pages 325-345 in J.W. Day, Jr., D.D. Culley, Jr., R.E. Turner, and AJ. Mumphrey, Jr., eds. Third coastal marsh and estuary management symposium. Louisiana State University, Division of Continuing Education, Baton Rouge. Herke, W.H., E.E. Knudsen, P.A Knudsen, and B.D. Rogers. 1987. Effects of semi-impoundment on fish and crustacean nursery use: evaluation of a "solution." Pages 2562-2576 in Coastal Zone '87, WW Div./ASCE, Seattle, WA Hoar, R.J. 1975. The influence of weirs on soil and water characteristics in the coastal marshlands of southeastern Louisiana. M.S. Thesis. School of Forestry and Wildlife Management, Louisiana State University, Baton Rouge. 94 pp. King, G.M., M.J. Klug, R.G. Wiegert, and AG. Chalmers. 1982. Relation of soil water movement and sulfide concentration to Spartina altemiflora production in a Georgia salt marsh. Science 218:61-63. Larrick, W.J., Jr. 1975. The influence of weirs on vegetation of the coastal marshlands of Louisiana. M.S. Thesis. Louisiana State University, Baton Rouge. 104 pp. Mendelssohn, I.A, and E.D. Seneca. 1980. The influence of spoil drainage on the growth of salt marsh cordgrass Spartina altemiflora in North Carolina. Estuarine Coastal Mar. Sci. 11:27- 40. Mendelssohn, I.A, K.L. McKee, and M.T Postek. 1982. Sublethal stresses controlling Spartina altemiflora productivity. Pages 223-242 in B. Gopal, R.E. Turner, R.G. Wetzel, and D.F. 162 Whigham, eds. Wetlands ecology and management. International Scientific Publications, India. 514 pp. Olinde, M.W. 1977. Waterfowl habitat on a fresh marsh in Terrebonne Parish, Louisiana. M.S. Thesis. School of Forestry and Wildlife Management, Louisiana State University, Baton Rouge. 97 pp. Powers, K.D. 1976. The relationship of waterfowl to the distribution of weeds in rice fields of southwestern Louisiana. MS. Thesis. School of Forestry and Wildlife Management, Louisiana State University, Baton Rouge. 73 pp. Spiller, S.F. 1975. A comparison of wildlife abundance between areas influenced by weirs and control areas. M.S. Thesis. Louisiana State University, Baton Rouge. 94 pp. Stearns, L.A, D. MacCreary, and F.C. Daigh. 1940. Effect of ditching for mosquito control on the muskrat population in a Delaware tidewater marsh. Univ. Del. Agric. Exp. Stn. Bull. 225:1- 55. Swenson, E.M., and R.E. Turner. 1987. Spoil banks: effects on a coastal marsh water level regime. Estuarine Continent. Shelf Sci. 24:599-609. Turner, R.E. 1987. Relationships between canal and levee density and coastal land loss in Louisiana. U.S. Fish Wildl. Serv. Biol. Rep. 85(14). 58 pp. Turner, R.E., C. Neill, and R. Kreidler. 1985. Experimental manipulations of marsh hydrology and their significance to marsh management. Unpubl. MS. Turner, R.E. [1988.] Landscape development and coastal wetland losses in the northern Gulf of Mexico. Am. Zool. (In press.) Turner, R.E., and D.R. Cahoon, eds. 1987. Causes of wetland loss in the coastal central Gulf of Mexico. Minerals Management Service, New Orleans, LA OCS Study/MMS 87-0119. 3 vols. Weaver, J.E. 1969. Otter trawl and benthic studies in an estuary at Marsh Island, Louisiana. M.S. Thesis. Louisiana State University, Baton Rouge. 88 pp. Weigert, R.G., AG. Chalmers, and P.F. Randerson. 1983. Productivity gradients in salt marshes: the response of Spartina ahemiflora to experimentally manipulated soil water movement. Oikos 41:1-6. Wengert, M.W., Jr. 1972. Dynamics of the brown shrimp, Penaeus aztecus aztecus Ives 1891, in the estuarine area of Marsh Island, Louisiana, in 1971. M.S. Thesis. Louisiana State University, Baton Rouge. 94 pp. Zucca, C.P. 1982. The effects of road construction on a mangrove ecosystem. Trop. Ecol. 23:105-123. 163 EFFECTS OF DRAWDOWN AND WATER MANAGEMENT ON A SERIOUSLY ERODED MARSH Bruce Lehto District Conservationist Soil Conservation Service 1400 Highway 14 Lake Charles, LA 70601 and Jeff Murphy 1200 Paris Street Lake Charles, LA 70601 ABSTRACT The occurrence of submergent and emergent plant species was recorded during October 1986, October 1987, and May 1988 in a severely eroded 541-ha marsh located adjacent to Black Lake in Cameron Parish, LA. Measurements from 1940 aerial photographs show 99% emergent vegetation and 1% open water. Measurements from 1983 aerial photographs show 2% emergent vegetation and 98% open water. O'Neil (1949) classified the area as fresh and intermediate marsh. The dominant vegetation in the 1940's was Jamaica sawgrass (Cladium jamaicenese). A system of levees and two guillotine-type structures prevent water exchange with the surrounding marsh and Black Lake. Rainfall is the sole source of water. A pump was used to effect a drawdown in the summer of 1986. Prior to the drawdown, the emergent plant species recorded were marshhay cordgrass (Spartina patens), glasswort (Salicornia sp.), seashore paspalum (Paspalum vaginatum), smooth cordgrass (Spartina alterniflora) and black needlerush (Juncus roemeranus). No submergent species were recorded. A record of emergent species occurring in October 1986 was the same as prior to the drawdown. No submergent aquatics were recorded. A pump was also used to effect a drawdown again in the summer of 1987. A record of emergent species occurring in October 1987 included all species recorded in October 1986 plus coast bacopa (Bacopa caroliniana), dwarf spikesedge (Eleocharis parvula), sprangletop (Leptochloa fascicularis), and cattail (Typha sp.). Submergent species recorded was widgeongrass (Ruppia maritima). A pump was again used to effect a drawdown in the spring of 1988. A record of emergent species occurring in May 1988 included all species recorded in October 1987 plus saltmarsh bulrush (Scirpus robustus) and bulrush (Scirpus validus). Widgeongrass was the only submergent species recorded. INTRODUCTION Deterioration of the marshes in the Black Lake area of Cameron Parish has resulted in a dramatic loss of vegetated areas to open water. An 81% reduction of vegetated areas occurred 164 between 1952 and 1974 in the Black Lake marshes south of the Intracoastal Waterway, west of Alkali Ditch, and east of Cameron Farms (Adams et al. 1978). This area experienced one of the highest marsh loss rates of any comparable area in coastal Louisiana for this period. Although the exact cause of this marsh deterioration has not been documented, it is thought that several contributing factors are increased salinities (Adams et al. 1978), erosion of the soil surface, subsidence, and excessive water depths. In 1984, the landowner and lessee of an impounded 541-ha marsh bordering the northeast shore of Black Lake (Figure 1) developed a conservation plan for revegetating the eroded marsh areas. Vegetated and open water areas were measured from available aerial photographs, percentage of emergent vegetation and open water are presented in Table 1. The O'Neil (1949) classified this management unit as fresh and intermediate marsh. The dominate vegetation until approximately 1960 was Jamaica sawgrass (W.P. Hardeman, Amoco Prod. Co., Lake Charles, LA; pers. comm.). Chabreck (1978) classified the area as brackish marsh. Based on information from Turner (1987), it is thought that increased salinities in this manage- ment unit eliminated less salt-tolerant species and a simultaneous increase in water depth caused Intracoastal Waterway \\> i N IS 3 0) -G \ to CO c to I— o u V- '5 I c o Z 3 C > to ca C ea u o U 1 > s u TO 3 t M ^ P- TO -C -£"■> u 1 TO M TO n> TO c o ^-. ll 3 TO It 2-5 fc. r° TO S& TO nj TO c 3 J O 61) 2%g £ to Q> u ts to ^-v TO n> TO TO vo r~- vo >/S i-I to f- in m (N (N ■ *o o u U \-t a. u X — > E o c u Ja e>o TO TO t- -— » u TO > a -O 175 Table 4. White shrimp landings from inshore waters of Cameron Parish, Louisiana. Annual catch Effort Catch per effort Year (kg) (number trips) (kg/trip) 1983 354,152 9,127 39 1984 655,1% 9,756 67 1985 539,823 7,020 77 1986 481,687 8,279 58 However, Little Pecan Lake is located along the interface between fresh and intermediate marsh, whereas the Grand Bayou sites are located within brackish marsh (Chabreck and Linscombe 1978). Catches of white shrimp in a lake along the fresh-intermediate marsh interface of the Barataria Basin were found to be substantially less than catches in brackish and saline marshes (Smith 1979). It was assumed that similar abundance patterns occur throughout coastal Louisiana. Therefore, white shrimp recruitment and abundance at Little Pecan Lake should be naturally less than that at Grand Bayou. The exaggeration of white shrimp production at Little Pecan Lake, relative to that from the Grand Bayou sites, may well be counterbalanced by the above-mentioned location- related effect. If such is the case, we could then qualitatively compare the effect of water control structures on white shrimp production within these semi-impounded marshes. Three hypotheses have been proposed to explain how weirs and other water control structures reduce the recruitment of estuarine organisms (Rogers et al. 1987). The most commonly accepted hypothesis is that immigrating estuarine organisms move passively with tidal currents. Therefore, structures that reduce tidal exchange should also reduce recruitment. Implied in this explanation is that, because of their passive transport, any reduction of water exchange will cause a proportional reduction in recruitment of estuarine organisms. A second hypothesis proposes that behavioral characteristics of ingressing estuarine organisms may cause them to avoid passing through or over water control structures even though physically able. The third hypothesis proposes that ingress of estuarine organisms is impeded when water control structures block that portion of the water column that organisms prefer to use. Assuming that tidal amplitude is similar at each site, an index of turnover or water exchange for each site can be estimated as the ratio of the water control structure's cross-sectional area (below marsh level) at its greatest constriction versus the watershed of the semi-impounded area. Therefore, at the unmanaged Grand Bayou site, for each square meter of the chute's cross-sectional area at its greatest constriction, there are 9.5 ha of watershed. Similarly, for each square meter of cross-sectional area above the low-level fixed-crest weir, there are 52.6 ha of watershed. At Little Pecan Lake, there are 148.7 ha of watershed for each square meter of culvert cross-sectional area. These indices provide a relative measure of the degree to which water exchange is reduced among sites (Table 5). Water levels within a semi-impoundment regulated by a fixed-crest weir did not fall as low as levels within a semi-impoundment regulated by a slotted weir (Rogers et al. 1987) or a semi- impoundment not regulated by a water control structure (Herke et al. 1987b). The period of flooding tide (recruitment period) was therefore longer for these semi-impoundments compared 176 Table 5. Water exchange indices and average white shrimp production estimates for each study site. Site Cross-sectional area of water control structure Water at the most area constricted point8 (ha) (m2) Water exchange index^ (m2:ha) Average white shrimp production0 Elevation and description of water control structure Non-weired Grand Bayou 26.5 2.78 1:9.5 28.7 Base of structure 152 cm below marsh level. 12.2-m-long, 183-cm-wide wooden chute. Low-level weir Grand Bayou 26.5 0.5 1:53.0 8.1 Weir crest set 30 cm below marsh level, 165 cm long. Weir located in a wooden chute same as above. Little Pecan Lake 174 1.17 1:148.7 14.3 Base of structure 127 cm below marsh level 9.1 -cm-long, 122- cm-diameter corrugated aluminum culvert with flap-gate and stop-log bay (weir crest length 231 cm). 8Cross-sectional area below marsh level. bCalculated using data from the first two columns. cData taken from Table 3. to that for a fixed-crest weir semi-impoundment (Rogers et al. 1987). Water exchange at the fixed-crest weir site was affected differently compared to the other sites where exchange occurred through a 122- to 162-cm-deep water column. Therefore, water exchange at the fixed-crest weir site cannot be accurately compared with that from either of the other sites. The 162-cm-deep unobstructed wooden chute at Grand Bayou and the 122-cm-diameter culvert at Little Pecan Lake were relatively similar in regard to the mechanism by which they reduced water exchange. For these sites, exchange indices may be used to compare the extent to which water exchange was reduced. 177 According to the exchange indices, water exchange at Little Pecan Lake (without accounting for flow reductions through stop-log operation and flap-gate closures) was reduced much more (at least 15.8 times more) than at the unmanaged Grand Bayou site. If ingress were directly proportional to the volume of inflow, then the reduction in water exchange should cause a proportional reduction in white shrimp production. However, estimated white shrimp production from Little Pecan Lake is only half that measured at the unmanaged Grand Bayou site. It appears that relatively severe reductions can be affected in water exchange without a proportional reduction in white shrimp production. This hypothesis implies that recruitment of estuarine organisms is not a totally passive phenomenon. Field and laboratory research has shown that penaied shrimp are capable of detecting difference in salinity (Hughes 1969; Penn 1975) and using vertical migration (Hughes 1969; Staples 1980; Hartman et al. 1987) and lateral migration (Copeland and Truitt 1987; Hartman et al. 1987) to immigrate into nursery areas. Arnold and Cook (1980) called this behavior selective tidal stream transport. Similar phenomena have also been documented for numerous immature estuarine-dependent fishes (King 1971; Fore and Baxter 1972; Sabins and Truesdale 1974; Hartman et al. 1987). Having detected the plume of fresher water exiting Little Pecan Lake through the open water control structure, post-larval white shrimp may have been able to position themselves for recruitment on subsequent flood tides. This active means of recruitment may explain why recruitment and production of white shrimp is not directly proportional to water exchange. An operable water control structure, such as a flap-gated structure, will not provide any ingress opportunities unless it is opened during the recruitment "season." Because high densities of post- larval white shrimp sometimes occur sporadically (Smith 1979), the water control structure should be kept open for as long as possible during the recruitment season in order to maximize ingress. In studying the effect of a low-level fixed-crest weir Bradshaw (1985) and Herke et al. (1987b) concluded that the weir caused a substantial reduction in recruitment of white shrimp and other estuarine organisms. The comparison of white shrimp production within Little Pecan Lake versus that from the low-level fixed-crest weir site suggests that a properly operated variable-crest flap- gated culvert may allow greater recruitment of white shrimp than the low-level fixed-crest weir. If this is so, one would expect the flap-gated variable-crest culvert would provide even greater recruitment opportunities than a standard fixed-crest (crest elevation 15.28 cm below marsh level) weir. Furthermore, the weir crest length at the Grand Bayou site was much longer (over 500%) than that recommended by current Soil Conservation Service guidelines. The culvert capacity at Little Pecan Lake was 31% greater than that recommended by Soil Conservation Service guidelines. If water control structures were installed at both sites according to current Soil Conservation Service guidelines, white shrimp production from the Grand Bayou site would likely be even lower relative to that from Little Pecan Lake. If recruitment of white shrimp and other estuarine organisms occurs according to the hypothesis of selective tidal stream transport, one might expect that white shrimp production from the low- level fixed-crest weir site would be higher than it is. However, post-larval white shrimp may not have actively selected this site for recruitment if fresher water was not flowing out over the weir on falling tides. Data indicate that salinities within semi-impoundments regulated by the low-level fixed-crest weir and a standard fixed-crest weir (crest elevation 15.2 cm below marsh level) were higher than adjacent outside waters during the white shrimp recruitment season (Rogers et al. 1987; Herke et al. 1987b). 178 Without detailed hydrological data, it is impossible to determine the extent to which the low- level fixed-crest weir reduced the volume of inflow relative to the other sites. If inflow was reduced more than that at Little Pecan Lake, that might explain why production of white shrimp was lowest at the fixed-crest weir site. Independent of water exchange, fixed-crest weirs affect recruitment of estuarine organisms through blockage of the lower and middle portions of the water column. A 122 -cm-diameter variable-crest flap-gated culvert, when operated properly, would provide ingress opportunities throughout a larger portion of the water column than would a low-level fixed-crest weir. Therefore, if immigrating post-larval white shrimp (and other immigrating estuarine organisms) are sensitive to blockage of the water column, then a water control structure such as the one at Little Pecan Lake may offer greater recruitment opportunities than a fixed-crest or a slotted weir. Because of scant data and the assumptions that were made in this study, findings generated herein should not be construed as scientifically based conclusions. Instead, these findings should be viewed as hypotheses. It is hoped that through this study, researchers will see that additional practical fishery or hydrology research is needed before we fully know how, and to what extent, different kinds of water control structures affect recruitment and production of estuarine organisms. CONCLUSIONS Available data suggest that when properly operated, a large diameter variable-crest flap-gated culvert, installed according to current Soil Conservation Service guidelines, may provide greater recruitment opportunities for white shrimp than either a standard-level fixed-crest weir or a low- level weir, installed according to current Soil Conservation Service guidelines. In comparing the semi-impoundment not regulated by a water control structure versus the semi-impoundment regulated by a variable-crest flap-gated culvert, it appeared that water exchange was severely reduced by the flap-gated culvert. Our observations suggest however, that relatively severe reductions can be affected in the volume of water exchange without a proportional reduction in white shrimp production. Immigrating post-larval white shrimp and other estuarine dependent organisms may utilize a combination of active locomotion and passive transport to orient toward and immigrate into selected areas, despite unfavorable tidal/exchange conditions. To maximize recruitment and production of white shrimp within an actively managed semi-impoundment, the structure should be kept open throughout the recruitment season, if possible. LITERATURE CITED Arnold, G.P., and P.R. Cook. 1980. Fish migration by selective tidal stream transport: first results with a computer simulation model for the European continental shelf. In J.D. McCleave, G.P. Arnold, and W.R. Neill, eds. Mechanisms of migration in fishes. Plenum Press, New York. Bradshaw, W.H. 1985. Relative abundance of small brown shrimp as influenced by semi- impoundment. M.S. Thesis. Louisiana State University, Baton Rouge. 61 pp. Chabreck, R.R., and G. Linscombe. 1978. Vegetative type map of the Louisiana coastal marsh. Louisiana Department of Wildlife and Fisheries, New Orleans. Copeland, B.J., and M.V. Truitt. 1967. Fauna of the Aransas Pass inlet, Texas. Vol 2. Penaeid shrimp postlarvae. Tex. J. Sci. 18(l):66-74. 179 Davidson, R.B., and R.H. Chabreck. 1983. Fish, wildlife, and recreational values of brackish marsh impoundments. Water quality and wetland management conference. New Orleans, Louisiana. Fore, P.L., and K.N. Baxter. 1972. Study of migratory patterns of fish and shellfish through a natural pass. Texas Parks and Wildlife Department Technical Series No. 9, Austin. 54 pp. Gagliano, S.M., K.J. Meyer-Arendt, and K.M. Wicker. 1981. Land loss in the Mississippi River deltaic plain. Trans. Gulf Coast Assoc. Geol. Soc. 31:295-300. Hartman, R.D., C.F. Bryan, and J.W. Korth. 1987. Community structure and dynamics of fishes and crustaceans in a southeast Texas estuary. Louisiana State University Agricultural Center, Baton Rouge. 116 pp. Herke, W.R., E.E. Knudsen, Z.X. Chen, N.S. Greene, P. A Knudsen, and B.D. Rogers. 1987a. Final report for the Cameron-Creole watershed fisheries investigation. Louisiana State University Agricultural Center, Baton Rouge. Herke, W.R., E.E. Knudsen, and B.D. Rogers. 1987b. Effects of semi-impoundment on fish and crustacean nursery use: evaluation of a "solution." Coastal Zone 1987, WW Div/ASCE, Seattle, WA Hughes, D.A. 1969. Responses to salinity changes as a tidal transport mechanisms of pink shrimp, Penaeus duorarum. Bio. Bull 136:46-53. King, B.D., III. 1971. Study of migratory patterns of fish and shellfish through a natural pass. Texas Parks and Wildlife Department Technical Series No. 9. Austin. 54 pp. National Marine Fisheries Service. 1988. Data obtained upon request from Mr. Lee Usie, National Marine Fisheries Service. New Orleans, LA Penn, J.W. 1975. The influence of tidal cycles on the distribution pathway of Penaeus latisulcatus Kishinouye, in Shark Bay, Australia. Aust. J. Freshwater Res. 26:93-102. Rogers, B.D., W.H. Herke, and E.E. Knudsen. 1987. Investigation of a weir-design alternative for coastal fisheries benefits. Louisiana State University Agricultural Center, Baton Rouge. 98 pp. Sabins, D.S., and P.M. Truesdale. 1974. Diel and seasonal occurrence of immature fishes in a Louisiana tidal pass. Proc. 28 Ann. Conf. Southeast. Assoc. Game Fish Comm. 161-171. Smith, D.A 1979. Documentation of the use of a brackish water estuarine zone as a nursery ground by penaeid shrimp. M.S. Thesis. Louisiana State University, Baton Rouge. 98 pp. Staples, D.J. 1980. Ecology of juvenile banana prawns Penaeus merguiensis, in a mangrove estuary and adjacent off-shore area of the Gulf of Carpenteria. I. Immigration and settlement of post larvae. Aust. J. Freshwater Res. 31:6735-653. Whetstone, J.M. 1987. Combination management for aquaculture and waterfowl. In Workshop proceedings. South Carolina coastal wetand impoundments: management implications. Technical report SG-SG-TR-87-1. Wicker, M.K., D. Davis, and D. Roberts. 1983. Rockefeller State Wildlife Refuge and Game Preserve: evaluation of wetland management techniques. Louisiana Department of Natural Resources, Coastal Management Section, Baton Rouge. 180 MARSH MANAGEMENT AND FISHERIES ON THE STATE WILDLIFE REFUGE-OVERVIEW AND BEGINNING STUDY OF THE EFFECT OF WEIRS Mark Konikoff and H. Dickson Hoese Department of Biology University of Southwestern Louisiana Lafayette, LA 70504 ABSTRACT The State Wildlife Refuge is a brackish marsh, with oligohaline, tidal, and heterotrophic water, a mostly undisturbed system on the western shore of Vermilion Bay about 15 m by water from the Gulf of Mexico. The main management practices are burning most of the refuge each year and construction of low water weirs on most small water bodies off Fearman Lake and Bayou. These have been recently expanded and refurbished. Burning may limit the abundance of intertidal mollusks, such as Geukensia demissa, but the effects on fisheries are unknown. The overall effects of weirs on estuarine animals are not known, but there is evidence that they limit movement. They may also serve to create and maintain different aquatic habitats. Studies begun in September 1987 using gill nets, trawls, and a quantitative sampler in comparable weired and unweired ponds and a common area in Fearman Lake have discovered some differences, but it is too early to tell if these are due to weirs, locations, or other factors. The oligohaline fauna consists of the infaunal Rangia cuneata and Macoma mitchelli, demersal juveniles of Callinectes sapidus, Penaeus setiferus and estuarine fishes, and adults of some freshwater species such as Ictalurus furcatus, Lepisosteus spp. and Dorosoma cepedianum. While scattered studies and observations made since the late 1950's, mostly in adjacent Vermilion Bay, suggest the lowering of salinities, especially during the flood years of 1973-75, there is also some evidence of saltwater intrusion. The important commercial and sport fishery species produced on the refuge are Lepisosteus spatula, Brevoortia patronus, Ictalurus furcatus, Sciaenops ocellatus, Paralichthys lethostigma, Callinectes sapidus, and Penaeus setiferus. Perhaps long term study of such a low diversity habitat will make for better understanding of natural and artificial effects of water levels. INTRODUCTION The State Wildlife Refuge, comprising 27,000 acres, is located in a low-salinity (brackish) marsh on the western shore of Vermilion Bay (Figure 1). Although the refuge is one of the most natural and least modified marshes in Louisiana, nearly all water bodies have low water weirs used as a management practice to retain water in the marsh for navigation, vegetation, waterfowl, and to slow erosion on the Vermilion Bay shoreline. Toms Bayou and a small connecting pond system leading from the refuge to the Audubon Refuge to the west is the only major system not weired. Although weirs have been long used in Louisiana brackish waters (Chabreck and Hoffpauir 1962), a recent study suggests that there is a significant reduction in exported fisheries production compared to a similar unweired area, due either directly or indirectly to the weir (Herke et al. 1987). While we will not discuss these arguments here (see Chabreck and Hoffpauir 1962 for a 181 STATE WILDLIFE REFUGE Figure 1. Map of State Wildlife Refuge showing the sample sites. Arrows indicate T = Toms Lake (unweired); F = Fearman Lake; B = Bob's Lake (weired). 182 summary of apparent effects), the fact that weired systems can maintain large standing crops of estuarine fishes and crustaceans (Weaver and Holloway 1974; Perry 1981) suggests that more study is needed to better understand the trade-offs brought about by weir construction. The present study, funded by the Louisiana Wildlife and Fisheries Commission, is designed to develop an overview of the fishery organisms of the State Wildlife Refuge over a several-year period and to try to determine the weir-induced effects on these organisms. Historic Salinity Trends in the Study Area The refuge lies at the eastern extremity of the Chenier Plain region (Gosselink et al. 1979) and at the western extremity of the Atchafalaya Bay system, which has been capturing increasing flows of the Mississippi since about a century ago (Gunter 1952). The refuge marsh is brackish, with burning practiced over most areas every year. Consistent with this type of marsh is the large production of white shrimp, Penaeus setiferus (Hebert 1968). Although salinity data have not been measured continuously at the refuge, there are data from a number of years suggesting little change of salinity over the last four decades (Table 1). Salinities may have responded to periods of either drought or floods, such as the floods of the 1970's (Juneau 1975; Hoese 1976), but the area has remained stable despite these events. To the contrary, Gosselink et al. (1979) reported a decrease in salinity at the Vermilion Lock, but this may be an artifact of several years of high salinities from drought and Hurricane Audrey in the 1950's. In our separate incomplete analysis of the fishery organisms studied since the 1950's, there is also no evidence yet detected of large changes in the fauna, although there may be effects on certain species. The purpose of this study is to provide a long-term (several years) analysis of the populations of aquatic animals in the refuge, especially in relation to the effect of the weirs. Additionally, material previously gathered on aquatic animals on the refuge will be summarized. A species list with pertinent information and references is being produced, with a referenced overview of the system based on historical work. The present paper will largely introduce the study and the preliminary results. MATERIALS AND METHODS Starting with a trial sampling in September of 1987, monthly samples are to be taken and continued through the duration of the project. Because of weather and logistical problems, no sample was taken in March 1988. Samples are taken with gill nets, trawls, and a quantitative barrel sampler. Representative comparative samples are taken in Fearman Lake, and in one unweired pond (off Toms Bayou), and one pond (Bob's Lake) where access is restricted by a 13.4-m weir (Figure 1). The weir to the lake restricts a 15-m channel preventing water levels falling below about mean sea level. In contrast, the small pond off Toms Bayou will go dry during low tides. Both lakes are roughly circular with widths of about 330 ±50 m, but Bob's Lake has an estimated area of about 11 ha, compared to 6 ha for Toms. The concept of the study is to test for differences between unweired and weired systems which are as close to being equal as possible in distance from the bay, size, and other attributes and to a common area between (Fearman Lake). Site samples will determine what animals are available from the pool of spawners in the open bay and gulf systems. For example, if the weir has an effect it might show up in the appearance of a species later in the weired pond than either the common area or the open pond. 183 Table 1. Historic average salinities for the study area. Where study reports a larger area, data were used only for stations closest to State Wildlife Refuge (usually western shore of Vermilion Bay). Study Years Average salinity (PPt) O'Neil (1949) 1930-40 6.9 Gunter & Shell (1958) 1951-52 1.4 Norden (1966) 1960-63 5.9 Hebert (1968) 1965 3.5 Dugas (1970) 1968-69 3.8 Hoese (1973) 1970 3.7 Hoese (1976) 1974-75 3.4 Unpublished 1979-86 4.3 Present study 1987-88 5.1 Gill net samples use a 60-m net with four sections, 15 m each, with mesh sizes of 2.5, 5.0, 7.5, and 10.0 cm. These are fished simultaneously in the three locations for a 24-hr period. Three 5- min trawl samples in each water body are taken with a 3-m trynet with a 4.4-cm body and a 3.2- cm cod with 1.25-cm stretched nylon liner. A quantitative barrel sample was developed based on a smaller version of a drop sampler (Zimmerman et al. 1984) which will be used at the same locations as the gill net samples at the same intervals. The sampler is a plastic 208-L drum cut open at both ends, but, as of this writing, sample analysis is incomplete. Only gill net and trawl data will be presented here. Statistical tests were done using the non-parametric sign test and the Friedman two-way analysis of variance (Siegel 1956). Additional incidental collections have been made by using various types of collecting gear to assist in the analysis of data and to assure that a complete list of animals is developed. Also all literature relative to the fisheries of the refuge and the effects of weirs are being gathered and studied. RESULTS GUI Net Collections A total of 18 species were caught in gill net samples. The greatest number of species was 16 in Fearman Lake with Toms and Bob's Lakes each having 12 species (Table 2). These differences were not statistically significant (p> 0.11). There were nine species caught at all three sites. The number of species caught exclusively at each site were: Toms - one; Fearman - three; and Bob's - one. The number of species uniquely absent from each site were: Toms - two; Fearman - none; and Bob's - two. Species found in both small lakes were also found in Fearman Lake. The coefficient of similarity (Southwood 1978) 184 Table 2. Species and locations of catch in gill net and trawl samples. T = Toms Lake (unweired); F = Fearman Lake; B = Bob's Lake (weired). Species Gillnet Trawl Lepisosteus oculatus TF B Lepisosteus spatula TF B Myrophis punctatus T Alosa chrysochloris T FB Brevoortia patronus TFB TFB Dorosoma cepedianum T F Dorosoma petenense F Anchoa mitchilli TFB Ictalurus furcatus TFB Anus felis TF Lucania parva B Syngnathus scovelli B Morone mississippiensis F B Lagodon rhomboides TF Aplodinoius grunniens T Bairdiella chrysoura F Cynoscion arenarius F Cynoscion nebulosus T Leiostomus xanthurus F TFB Micropogonias undulatus F TFB Pogonias cromis FB Sciaenops ocellatus TFB Mugil cephalus TFB TF Gobionellus boleosoma TFB Gobiosoma bosci FB Peprilus burn' F Prionotus tribulus TFB Citharichthys spilopterus B Paralichthys lethostigma TFB TFB Achirus lineatus F B Symphurus plagiusa TFB Anilocra acuta F Gammarid sp B Rhithopanopeus harrisi B Callinectes sapidus TFB TFB Penaeus setiferus B TFB Penaeus aztecus FB Palaemonetes sp TFB Rangia cuneata TFB Macoma mitchelli TFB 185 between Toms and Bob's was Cs = 0.75. This was not significantly different from the similarity between Fearman and Toms Lakes (Cs = 0.79) or Fearman and Bob's (Cs = 0.79). Gill net catch abundance was greater in Fearman Lake than in the two smaller lakes (Figure 2), but none of the differences were statistically significant (p > 0.22). A comparison of the catch rate of 12 species in the three areas is presented in Figure 3 for count and Figure 4 for weight. Fearman Lake had the greatest number of species that had the highest catch in an area when determined by count (nine species) or by weight (10 species) (Figure 5). Toms Lake had significantly fewer species with the best catch when determined by weight (three species) than Fearman Lake (10 species) (p = 0.025). There were no other statistically significant differences among areas as to the number of species with the highest catch (Figure 5). Observations on individual species with emphasis on season and area of gill net catch follow: Sciaenops ocellatus. Red drum was one of the most widespread species taken from October through January. No area dominated, although they disappeared from Bob's in January and a month later in the other lakes. Three reappeared in April. Paralichthys lethostigma. Flounder catch was scattered over most months except for November and February, but no pattern between the lakes was evident. Ictalurus furcatus. except December. Bob's. Blue catfish was the most common large fish, appearing in every month Blue catfish were most commonly caught in Fearman; only 10 were taken in UN-NBRED FEARMAN L. S WEIRED N U M B E R O R K I L O s 150.00 120.00 90.00. 60.00. 30.00 0.00 COUNT KILOS NUMBER OR WEIGHT OF TOTAL CATCH Figure 2. Gill net catch in three areas. 186 UN-NO RED □ FEARMAN L. S: WEIRED I N D I V I D U A L S K I L O G R A M S 100.00, 80.00 60.00. 40.00 20.00 felis cro«i ocell furca cepha letho spatu ocula patro ceped chrvs sapid SPECIES CAUGHT Figure 3. Number of individuals of 12 species caught in gill nets in three areas. Species names are abbreviated; see Table 2 for full names. r~l : UN-* BRED dj FEARKAN L £2 : WEIRED 120.00 96.00 72.00 43.00 24.00. 0.00 _^_ H. _IuduL. felis crosi ocell furca ceoha letr.o spatu ocula patro :epea chrys sapid SPECIES CAUGHT Figure 4. Weights of 12 species caught in gill nets in three areas. Species names are abbreviated; see Table 2 for full names. 187 : UN-NE1RED HI : FEARMAN L. Z3 ! WEIRED N U M B E R O F S P P 20.00 14.00 12.00 8.00. 4.00. 0.00 ALL HOST KILOS ALL AND MOST ABUNDANT SPECIES IN AN AREA Figure 5. Number of species caught in gill nets. ALL shows all species caught in three areas. MOST shows the number of species that had the greatest catch in each area when determined by count KILOS shows the number of species that had the greatest catch in each area when determined by weight Alius felis. Hardhead catfish were found in small numbers only in September and April. None was taken in Bob's. Lepisosteus spatula. Both spotted and alligator gars showed a similar pattern, discussed under the spotted gar. Only 11 alligator gar were taken. Lepisosteus oculatus. Forty-nine spotted gar were taken, almost in the exact same pattern as the alligators. They were absent from Fearman until February, but were caught in the other lakes in most months except January and February. Mugil cephalus. Mullet catch was scattered over all months except November; no pattern was evident. Pogonias cromis. Black drum were caught in small numbers, but none of the 15 taken came from Toms. Brevoortia patronus. Only a few juveniles were taken; very few were taken in Bob's. Callinectes sapidus. Blue crabs disappeared from catches from November through April, but there were scattered catches in all areas. Most of the crabs taken in September and October were copulating pairs. Miscellaneous species. Eight additional species were taken, representing fewer than 10 individuals: one was exclusive to each small lake, two exclusive to Fearman, one common between Fearman and each of the other two lakes, and two in all three lakes. 188 Trawl Collections Data are only available for September through April, an important period for the spawning of many species, but eliminating the equally important warmer summer months. A typical winter low of trawl-caught individuals was followed by large increases with warming temperatures. Twenty-nine species (not counting annelids or insects) were caught by trawling. The number of species in Fearman Lake was 22; Toms Lake, 18; and Bob's Lake, 21 (Table 2). The number of species caught in Toms was significantly less than in Fearman (p = 0.031), but other differences were not statistically significant (p > 0.19). Thirteen species were caught in all three sites (Table 2). The number of species caught exclusively in each site were Toms, two; Fearman, four; and Bob's, five. The number of species uniquely absent from each site were Toms, three; Fearman, none; and Bob's, two. As in the gill net samples, this means that species caught in both small lakes were also caught in Fearman Lake. The coefficient of similarity (Southwood 1978) between Toms and Bob's was C$ = 0.67. This was not significantly less (p > 0.19) than the similarity between Fearman and Toms (Cs =0.75) or Fearman and Bob's (Cg = 0.74). Trawl catch abundance was greater in the two smaller lakes than in Fearman Lake (Figure 6), but these differences were not statistically significant (p = 0.95). A comparison of catch rate of 19 species in the three areas is seen in Figures 7 and 8 (weight) and Figures 9 and 10 (count). Bob's Lake had the greatest number of species with the highest catch in an area when determined by number (13 species) or by weight (11 species) (Figure 11). There were no statistically significant differences among areas as to the number of species with the highest catch (p > 0.08). Observations on individual trawl-captured species (especially with respect to season and area) follow: Macoma mitchelli. These clams were only incidentally caught in the trawl, but they appeared nearly equally in all three areas. Juveniles (6-7 mm) appeared in both December through February. Rangia cuneata. No rangia were taken in Toms Lake, and only 3 of the 48 taken came from Bob's. Specimens as small as 2 mm were caught in Fearman in January, and by February ranged from 4-11 mm. Anchoa mitchilli. Bay anchovies appeared sporadically everywhere with no apparent pattern. Large catches were made in October in Fearman and Bob's, Toms in November, Fearman in February, and again Fearman and Bob's in April. Palaemonetes sp. Grass shrimp were clearly most common in Bob's, especially in April when over 2,000 were taken, including many that were ovigerous. They occurred sporadically elsewhere, except for moderate catches in February in Toms. Leiostomus xanthurus. Most spot came from Toms in February and April, and most were juveniles ranging from 20 to 40 mm. A few were caught at all three locations; a good catch of 53 was taken in one haul from Bob's in April. Penaeus setiferus. Although white shrimp are among the most common animals on the refuge (Hebert 1968), our samples were taken mostly when they were least common. Fair numbers 189 UN-Mil RED FEARHAN L. za. WEIRED 10000.00. N U M B E R O R G R A M S I N D I V I D U A L S 3000.00 6000.00. 4000.00 2000.00. 0.00 COUNT 6RANS NUMBER OR WEIGHT OF TOTAL CATCH Figure 6. Trawl catch in three areas. [.■■- J : UN-WHRED FEARHAN L. S: WEIRED 5000.00, 4000.00 3000.00. 2000.00. 1000.00 0.00 undul ntch patro xanth paleo SPECIES CAUGHT sapid setif Figure 7. Number of individuals of seven species caught in trawl samples in three areas. Species names are abbreviated; see Table 2 for full names. 190 f~] : UN-KHRED □ FEARflAN L. 22 : WEIRED 40.00. I N D I V I D U A L S 48.00. 36.00 24.00 12.00 0.00 1 *~£ L' '■" :i: ^L P^l ^ :.:» arena tntw boleo bosci rhoab cepna plaoi letho spilo ivrop aztec rangi SPECIES CAUGHT Figure 8. Number of individuals of 12 species caught in trawl samples in three areas. Species names are abbreviated; see Table 2 for full names. ED UN-KEI RED EZJ : FEARHAN I. E3 i WEIRED G R A M S 5000.00 4000.00. 3000.00 2000.00. 1000.00. O.OO unoul flitch patro xantfi paleo sapid SPECIES CAUGHT setif Figure 9. Weights of seven species caught in trawl samples in three areas. Species names are abbreviated; see Table 2 for full names. 191 UN-* I! RED L_J : FEARMAN L. ^ : WEIRED 25.00. 20.00. G R I 15.00. 10.00 5.00. 0.00 Ssss r. '•'■"•'.' 3 §§•$5; vSSs arena tnbu boleo bosci rhoab cepha plaqi letho spilo avrop a: tec SPECIES CAUGHT Figure 10. Weights of 11 species caught in trawl samples in three areas. Species names are abbreviated; see Table 2 for full names. ED: UN-WEIRED □ : FEARHAN L. E2 WEIRED 25.00 N U s E R O F S P P 20.00. 15.00. 10.00. 5.00 0.00 ALL HOST GRAMS ALL AND MOST ABUNDANT SPECIES IN AN AREA Figure 11. Number of species caught in trawl samples. ALL shows all species caught in three areas. MOST shows the number of species that had the greatest catch in each area when determined by count KILOS shows the number of species that had the greatest catch in each area when determined by weight 192 were taken everywhere in October, with a few reappearing in December. A few subadult (70- 88 mm) juveniles were taken only in Fearman in April. Penaeus aztecus. Brown shrimp are uncommon in the low salinities of the refuge (Hebert 1968), but a few (25) small juveniles (17-32 mm) were taken in Fearman and Bob's in April. Callinectes sapidus. Blue crabs appeared over most of the area; larger individuals predominated in September, October, and April and newly metamorphosed juveniles (7-30 mm) from November through February. Catches of juveniles were limited in Toms. Paralichthys lethostigma. Only one southern flounder was taken in Toms, but only 36 individuals were taken altogether. Newly transformed juveniles (12-37 mm) appeared from December through February. Micropogonias undulatus. Croaker were widespread with young-of-the-year (15-50 mm) appearing everywhere from December through April. Somewhat fewer were taken early in Bob's, but by April more were taken there than in the other two areas combined. Brevoortia patronus. Juvenile menhaden (22-41 mm) appeared first in numbers in Fearman in December, became common in Toms in January, but were delayed until February in Bob's. Miscellaneous species. A total of 18 other species were taken in very small numbers (Table 2). Of these, four were taken only in Fearman, five only in Bob's, and two only in Toms. Three were taken in all areas, and two were common to Fearman and each of the other two lakes. DISCUSSION The initial hypothesis that seemed most reasonable was that Fearman Lake would be the closest to the spawning grounds of most species and would receive the most juveniles the earliest. We specifically decided to trawl on the northern shore of Fearman Lake nearest to Bob's so that, if species were lacking, it would be because the weir served as an impediment, and not because the animals were not in the area. This hypothesis is suggested by studies on weired versus unweired areas by Herke and his students (Herke et al. 1987), who found evidence of delayed migration in weired areas. Several types of animals followed this pattern. Menhaden appeared in Fearman early, but reached Toms before Bob's, and by April seemed to diminish in Fearman. Spot fit this pattern, and never became very common in Bob's. Other species, however, did not follow the pattern. Croaker appeared first in Fearman, and then showed no clear-cut preference for any locale. Crabs seemed to invade Bob's earliest, and never became as common in Toms. Grass shrimp were only common in Bob's. The delaying effect of the weir may have been counter- balanced by the delay caused by the longer distance up Toms Bayou to Toms Lake, but our data do not show a consistent delaying effect of the weir. Other species may have been more affected by water depth than by delay in recruitment. Spot seem to prefer very shallow water when small, and do not normally overlap in depth distribution with croaker. This suggests that the distribution of spot in the lakes may be due to the lower average water levels in Toms. Nevertheless, Weaver and Holloway (1974) found more spot in a 193 weired than unweired area on nearby Marsh Island. Most of their other distributions seemed to agree with ours, especially for the menhaden, which were more common in unvegetated areas and more prevalent where weirs are absent. Of the incidental species, most appeared in Fearman, but Bob's contained more than Toms. This pattern may not be related to the weir or spatial arrangements, since two of the species, pipefish and rainwater killifish, prefer submerged vegetation present only in Bob's. Overall, in comparing the two small lakes, we found no statistically significant differences between catch rates or number of species, but we did find some individual species differences that cannot be tested with data from only 1 year. CONCLUSIONS While it is too early in the study to draw any conclusions, a number of facts suggest that fruitful, more substantiated conclusions will ultimately be available from such a study. Differences among the three lakes could be caused by several factors: (1) Fearman is closer to the supply of larvae for most species and should have a greater number of species than the other two sampling areas. (2) Bob's has a weir which keeps water levels more stable and never allows exposed bottom, resulting in larger amounts of detritus and development of submerged vegetation. The weir may restrict migrations. Toms goes dry many times during the year and must have a shallower average depth, which could be preferred by certain species like spot and red drum. (3) Toms is farthest from the source of larvae, is a smaller lake, and is reachable only through a long winding bayou. It is closest to the large freshwater source of the marsh to the west. (4) Due to fortuitous events, blocks of water with larvae of certain species may enter either Bob's or Toms. Bob's, located on the north side of Fearman, may be favored during southerly winds, while the reverse is true on the south shore, although northerly winds cause water levels to drop everywhere. Also, tidal currents, even when wind driven, seem to fill all areas. If these fortuitous events are the main cause of differences, then the observed differences will not be consistent from year to year. At this point there are no clear-cut statistically significant differences between the areas, and possible similarities outweigh the differences between the weired and unweired areas, as well as the common area of Fearman Lake. However, certain species may be somewhat selected more for one area or the other. At present the data suggest that if the weir is the cause of the observed distributions, weirs favor grass shrimp, juvenile crabs, and more minor species, but discriminate against menhaden, spot, and perhaps other species tied to very shallow water. At this point the data are not conclusive but are very intriguing. ACKNOWLEDGMENTS This study was funded by a contract with the Refuge Division of the Louisiana Department of Wildlife and Fisheries. Thanks to Johnny Tarver and Greg Linscombe for their support and 194 encouragement. Field laboratory facilities and boats were supplied by the Louisiana Universities Marine Consortium at generous rates. Mark LaSalle, U.S. Army Engineers Waterways Experiment Station, Vicksburg, MS, provided valuable suggestions on data analysis. University of Southwestern Louisiana students Rowdy Guidry, Robert Venable, and Dave Severson did much of the field collections under difficult conditions. LITERATURE CITED Chabreck, R.H., and CM. Hoffpauir. 1962. The use of weirs in coastal marsh management in Louisiana. Proc. Ann. Conf. Southeast. Assoc Game Fish Comm. 16:103-112. Dugas, R.J. 1970. An ecological survey of Vermilion Bay 1968-69. M.S. Thesis. University of Southwestern Louisiana, Lafayette. Gosselink, J.G., C.L. Cordes, and J.W. Parsons. 1979. An ecological characterization study of the Chenier Plain coastal ecosystem of Louisiana and Texas. U.S. Fish Wildl. Serv. FWS/OBS- 78/9 through 78/11:302 pp. Gunter, G. 1952. Historical changes in the Mississippi River and adjacent marine environment. Publ. Inst. Mar. Sci. Univ. Tex. 2(2):19-139. Gunter, G, and W.E. Shell, Jr. 1958. A study of an estuarine area with water-level control of the Louisiana marsh. Proc. La. Acad. Sci. 21:5-34. Hebert, H.F. 1968. Abundance and size distribution of white and brown shrimp in the North Lake area of Redfish Point, Vermilion Bay, Louisiana, 1965-67. M.S. Thesis. University of Southwestern Louisiana, Lafayette. Herke, W.H., E.E. Knudsen, P.A Knudsen, and B.D. Rogers. 1987. Effects of semi-impoundment on fish and crustacean nursery use: evaluation of a "solution." Coastal Zone '87, W/W Div./ASCE:2562-21576. Hoese, H.D. 1973. Abundance of the low salinity clam, Rangia cuneata, in southwestern Louisiana. Proc. Nat. Shellfish. Assoc. 63:99-106. Hoese, H.D. 1976. Final report study of sport and commercial fishes of the Atchafalaya Bay region. Conducted for the U.S. Fish and Wildlife Service by the Department of Biology, University of Southwestern Louisiana, Lafayette, LA 50 pp. Juneau, C.L., Jr. 1975. An inventory and study of the Vermilion Bay Atchafalaya Bay complex. La. Dep. Wildl. Fish. Tech. Bull. 13:1-153. Norden, C.R. 1966. The seasonal distribution of fishes in Vermilion Bay, Louisiana. Wis. Acad. Sci. Arts Letters 55:119-137. O'Neil, T. 1949. The muskrat in the Louisiana coastal marshes. Louisiana Department of Wildlife and Fisheries. 152 pp. Perry, W.G. 1981. Seasonal abundance and distribution of brown and white shrimp in a semi- impounded Louisiana coastal marsh. Proc. La. Acad. Sci. 44:102-111. Siegel, S. 1956. Non-parametric statistics for the behavioral sciences. McGraw-Hill. 312 pp. Southwood, T.R.E. 1978. Ecological methods with particular reference to the study of insect populations, 2nd ed. Chapman and Hall, London. 524 pp. Weaver, J.E., and L.F. Holloway. 1974. Community structure of fishes and macrocrustaceans in ponds of a Louisiana tidal marsh influenced by weirs. Contrib. Mar. Sci. 18:57-69. Zimmerman, RJ., T.J. Minello, and G. Zamora, Jr. 1984. Selection of vegetated habitat by brown shrimp, Penaeus aztecus, in a Galveston Bay salt marsh. Fish. Bull. 82:325-336. 195 THREATS TO COASTAL FISHERIES William H. Herke U.S. Fish and Wildlife Service and Barton D. Rogers School of Forestry, Wildlife, and Fisheries Louisiana Cooperative Fish and Wildlife Research Unit Louisiana State University Agricultural Center Baton Rouge, LA 70803 ABSTRACT Many saltwater fishes and crustaceans caught in Louisiana spawn in the Gulf of Mexico, but their young must migrate into the coastal marshes, which they use as a nursery. There they grow rapidly into juveniles or subadults and then migrate back to the gulf. Levees and water-control structures are being used in an attempt to slow the rapid erosion of the marsh. Our studies show that these structural measures interfere with the migratory movements of aquatic organisms and greatly reduce fisheries production in the areas semi-impounded by the structures. We know of no documented studies proving such structural measures actually reduce marsh erosion, and there is some evidence they may actually hasten marsh loss. Therefore, we believe marsh management permit applications should be placed on hold until the most important questions concerning semi-impoundment can be answered. In 1987, two Acts of the Louisiana Legislature authorized use of the marsh nursery for mariculture. In our opinion, these acts are not in the public interest and should be repealed. INTRODUCTION Many saltwater fishes and crustaceans caught in the Louisiana commercial and sport fisheries have a similar life cycle. Adults spawn in the Gulf of Mexico; eggs hatch in a short time; and larvae or tiny juveniles are carried by the current or swim toward the coast and usually proceed through the bays into the marsh where they grow rapidly. After a few weeks or months, the juveniles or subadults begin their migration back toward the gulf, where the survivors eventually spawn to complete the cycle (Figure 1). Examples of species that complete the cycle from gulf to marsh and back to gulf in 1 year are brown shrimp (Penaeus aztecus), white shrimp (Penaeus setiferus), gulf menhaden {Brevoortia patronus), and Atlantic croaker (Micropogonias undulatus). Other species such as redfish (red drum, Sciaenops ocellatus) and speckled trout (spotted seatrout, Cynoscion nebulosus) may take longer to complete the cycle but still make similar migratory movements. Weirs have long been used in Louisiana to regulate marsh water levels for purposes of increasing waterfowl food production, improving trapper access, and the like. Traditionally, these weirs have been solid dams placed across tidal channels. The crest of these weirs is usually about 15 cm below the average ground level of the surrounding marsh. Limited water flow can occur only when the water level exceeds the crest level; when water level is at or below crest level, the water behind the weir is impounded; thus the area controlled by the weir is said to be semi- impounded (Herke 1971). Although limited water exchange over the weir crest can occur, the weirs have the potential of reducing fishery production because they are in the migratory pathway; the larvae and tiny juveniles must pass over the weirs to reach the semi-impounded marsh nursery, and the surviving juveniles and subadults must again pass over them on their return to the gulf. FISHERIES STUDIES We began studying the effects of weirs on fisheries over 20 years ago, and we soon noted circumstantial indications that weirs reduced production of some fishery species. Herke (1968) took 1% •-? v^^^^t?- "%--"^\-^-y.v^ ^'^ijhA'J- ^-^v^-/^*"*"*-***^*-"^---"-*-"1"^-*^^' ILES PS^Sj "'_?■-"•. ^*, ?-■". *5 ADULTS °0 EGGS LARVAL STAGES Figure 1. Generalized life cycle of penaeid shrimp. Most estuarine-dependent fishes in the Gulf of Mexico make similar migratory movements, but undergo fewer morphological changes as they grow. 197 significantly greater numbers of brown shrimp below a weir than above it and concluded that the weir may have been an ethological barrier for some species even if it was not a total physical barrier. Recruitment of several aquatic species (Herke 1971) and brown shrimp (Wengert 1972) into semi-impounded areas was delayed, as was emigration from these areas. Moreover, Wengert's average catch of brown shrimp per trawl was consistently almost 4 times as great from the unimpounded areas. Weaver and Holloway (1974) found the standing stock of gulf menhaden, white shrimp, and Atlantic croaker to be much lower in semi-impounded areas than in adjacent unimpounded areas. In most cases "the detrimental effect [on estuarine-dependent fisheries] seems to be magnified if semi-impoundment results in increased growth of submerged aquatic vegetation- -and stimulation of such vegetative growth is a primary reason for creating semi-impoundments" (Herke 1979). In the late 1970's a decision was made to install large concrete weirs in the two canals connecting the marsh of Sabine National Wildlife Refuge to the western edge of Calcasieu Lake. The weir crests were to be set at the conventional height, but unlike traditional weirs, there was to be a radial arm gate in each. The gate, when lifted, was to provide a vertical opening about 10 ft wide from top to bottom of the channel. The U.S. Fish and Wildlife Service funded a study to develop baseline biological and physical information so that Refuge personnel could manage the gates for overall wildlife needs, yet reduce as much as possible the impact on estuarine-dependent fisheries organisms. Passive traps, pictured in Herke and Rogers (1984), were mounted in each canal as the principal sampling gear for our study. The traps fished the top, middle, and bottom of the water column and caught organisms moving both to and from the marsh nursery. Although the study was not designed to determine the effects of weirs on fishery use of the marsh, much pertinent information was obtained. The final report (Herke et al. 1984a) contained an abundance of information on such things as the seasonal presence, relative abundance, directional movements, and use of habitat types by numerous species. The canals were, used as the migratory pathway between the marsh nursery and the Gulf of Mexico by 117 fish and 12 crustacean species (Herke and Rogers 1984). There was no time during the year when closure of a water-control structure in one of these canals would not have interfered with the migratory movements of a number of species. Figure 2 illustrates this point by showing the periods during which only eight of the more important species were caught in the traps while moving either to or from the marsh nursery. In the canals, most species moved mainly at dusk and at night. Cold front passages and succeeding low water temperatures were followed by large emigrations 1 to 3 days later. (The absence of openings in a weir at such times could prevent such emigrations and cause fish kills due to cold. Such openings can also allow escape during low water periods in hot weather when low dissolved oxygen can cause fish kills; large scale emigration of brown shrimp took place through the weir gate slot at water levels far below the weir crest-Schultz 1985.) Most species moved primarily in the upper and middle levels of the water column, although some such as white trout (sand seatrout, Cynoscion arenarius), Atlantic croaker, redfish, and speckled trout moved mainly in the bottom half of the water column (Rogers and Herke 1985). This information, coupled with lower speckled trout catches in semi-impounded areas than in nearby natural areas in other studies, suggests that weirs inhibit immigration of speckled trout into semi-impounded areas (Herke et al. 1984b). Most of the preceding studies estimated standing crop, which is not the same as annual production, and thus gave only circumstantial evidence that semi-impoundment reduces fisheries production. Standing crop is the number of individuals and the biomass in a given area at a particular point in time. Rather than attempting to catch all the individuals to weigh and measure standing crop, biologists usually take samples and use the results as an index of the standing crop. Annual production is a function of the standing crop and how many times it "turns over" during the year. For example, a hectare of unimpounded marsh and a hectare of semi-impounded marsh may have the same standing crop of shrimp. Shrimp, however, need to cycle between the gulf and the marsh, and some young shrimp are normally moving into the marsh while older ones are moving toward the gulf. If a weir or other water-control structure inhibits these movements by 198 BROWN SHRIMP RED DRUM /'.WHITE ' 'SHRIMP DEC TIME OF YEAR Figure 2. Approximate period of movement (in and out combined) through the canals between the marsh and Calcasieu Lake, and eventually the Gulf of Mexico, by the young-of-the-year of eight important species. A value of 100 on the index equals the period of maximum movement for that species. During the entire Sabine Fisheries Study, members of 117 fish and 12 crustacean species were caught 50%, it will reduce turnover rate from the semi-impounded marsh by 50%. Thus, if a biologist took samples from both areas, the catch per unit of effort (the index of standing crop) should be about the same; productivity would appear to be about equal, whereas the unimpounded area would actually be twice as productive because shrimp using it were cycling in and out twice as fast. In the early 1980's we began a study, funded by the U.S. Soil Conservation Service, to determine quantitatively the effect of a fixed-crest weir on fishery annual production. A levee was constructed around 70 ha of natural marsh, and an interior levee divided this area into two areas of 35 ha each (Figure 3). Each area contained about 25% emergent marsh and 75% open water. The natural inlet from Grand Bayou was closed off and identical plywood-lined chutes, opening on a common vestibule from Grand Bayou, were constructed into each area (Figure 4). A solid weir with a fixed crest set 30 cm (instead of the usual 15) below average marsh ground level was installed in one chute; the other chute was left unweired. Identical trap systems were installed in each chute. Incoming larvae and juveniles could enter each area by passing through the 6-mm mesh openings in the traps, or through the 7.6-cm-wide vertical slit at the pondward end of the trap system. All outgoing organisms too large to pass through the 6-mm mesh were shunted into the traps. 199 200 Figure 3. Diagram of the paired ponds. The middle levee divided the total area into two areas of about 35 ha each. The traps fished continuously from 15 February 1983 through 13 February 1984 (Year 1), except for about 30 minutes each morning when they were raised for emptying (at which time a screen was inserted in place of the trap to prevent any outward movement of organisms). On 14 February 1984 the weir was switched to the other chute, and continuous trapping was resumed until 15 February 1985 (Year 2). The results of this quantitative study (Herke et al. 1987a, 1987b) confirmed what we had inferred from the previous circumstantial evidence: members of 107 species were taken during the 2 years from the unweired pond whereas members of only 83 species were taken from the weired pond, and the catch of most species was substantially lower from whichever pond contained the weir in its chute. The total catches of some of the economically important species are listed in Table 1 and shown graphically in Figure 5; the percentage of reduction in catch from the weired pond, compared to that from the unweired pond, is given in Table 2. 200 Figure 4. Detailed diagram of the trap system for the paired ponds shown in Figure 3. Several of our studies have indicated that the habitat in semi-impounded areas is suitable for a number of estuarine-dependent fisheries species, even though their production there may be considerably reduced. We believe the reduced production is primarily due to too few of the young being able to get into the semi-impounded area. Using our same paired pond study site just described, Bradshaw (1985) found such to be the case for brown shrimp. In another study at the same site, funded by the U.S. Army Corps of Engineers, the Louisiana Department of Natural Resources, and the Louisiana State University Coastal Fisheries Institute, we tested a modification of the standard fixed-crest weir that allowed increased access by immigrating brown shrimp to see if greater production would occur. A standard fixed-crest weir, with the crest then set 15 cm below average marsh ground level, was placed in the chute to one pond. The weir placed in the other chute was identical except for a 10-cm-wide slot from top to bottom. This was done in December 1985 prior to the onset of immigration of the 1986 crop of young brown shrimp. 201 Table 1. Total catches (by number and weight) of some of the economically important organisms leaving the two study ponds, February 1983 through February 1985. Number fin 1,000V) Weieht (kz) 1983-84 1984-85 1983-84 1984-85 Species No weir Weir No weir Weir No weir Weir No weir Weir Gulf menhaden 1,838 135 2,902 583 1,426 229 1,750 536 Atlantic croaker 556 65 842 752 1,185 316 1,070 1,388 Blue crab 447 295 267 105 3,358 1,510 2,322 2,065 Brown shrimp 316 101 286 57 840 420 858 393 White shrimp 256 30 320 48 723 150 793 279 Spot 31 14 77 33 185 155 268 153 Striped mullet 23 24 52 36 1,061 710 553 1,437 All other species 1,344 566 1,517 433 1,427 961 1,361 826 Total 4,811 1,230 6,263 2,047 10,205 4,451 8,975 7,077 2,8001 o 3001 o o >< 200 U 0Q 3 1001 SAND SEATR0UT BROWN SHRIMP YEAR 1 YEAR 2 on Ld m Z O o o Ixl m 2E z 150 100 SPOTTED SEATR0UT "1 350 280 210 140" 70- 0 WHITE SHRIMP YEAR 1 YEAR 2 NO WEIR DWEIR Figure 5. Total number of four important species caught each year from the ponds shown in Figure 3. 202 Table 2. Percentage of change in catch when comparing catches from the weired pond to catches from the unweired pond. (The unweired pond catch was subtracted from the weired pond catch, the result was divided by the unweired pond catch, and that result was multiplied by 100. The species listed are the same as in Table 1.) Number Weight Species Year 1 Year 2 Year 1 Year 2 Gulf menhaden -93 -80 -84 -69 Atlantic croaker -88 -11 -73 30 Blue crab -34 -61 -55 -11 Brown shrimp -68 -80 -50 -54 White shrimp -88 -85 -79 -65 Spot -54 -56 -16 -43 Striped mullet 4 -32 -33 160 All other species -59 -43 -33 -39 All species -74 -67 -56 -21 The traps were operated continuously from 15 February to 30 July 1986. Catch of brown shrimp from the pond with the slotted weir was 2.4 times greater in number, and 84% greater in weight, than the catch from the pond with the standard fixed-crest weir. During this study, members of 57 species were taken in the trap on the slotted weir pond, whereas members of only 42 species were taken in the trap on the standard fixed-crest weir pond (Rogers et al. 1987). Moreover, the slotted weir appeared to control water levels adequately for other management purposes. Nursery usage, however, was still apparently lower in both the slotted weir and the standard fixed-crest weir ponds than in a nearby unimpounded pond. During the study, equal trawling efforts in each of the ponds collected members of 46 species in the unimpounded pond, 29 in the slotted weir pond, and 27 in the standard weir pond. We consider the slotted weir to be an improvement for fishery purposes, but realize that testing of other water-control designs should continue if the use of water-control devices in the marsh is also going to continue. In furtherance of this goal, and in cooperation with the National Audubon Society at their Paul J. Rainey Wildlife Sanctuary, we are currently studying the effects of a rock weir designed and installed by the sanctuary personnel. We believe the best design for passing young aquatic organisms into semi-impounded areas has yet to be determined, but with sufficient research, satisfactory solutions to the passage problem may be possible. Moreover, our past studies indicate the habitat in semi-impounded areas is generally suitable for those organisms that do gain access. As will be evident in the next section, however, in many circumstances we suspect semi- impoundment may be destructive to the habitat itself. MARSH MANAGEMENT Herke (1979) stated, "Before anyone makes substantial expenditures to (1) build more weirs of conventional design, or (2) design new weir types, or (3) tear out existing weirs, or (4) maintain existing weirs, I believe the true effects of semi-impoundment on nursery production (not standing crops) should be determined." We believe these effects have now been sufficiently determined to say that marsh management usually is detrimental to fisheries in the short run when it is done by means of levees and weirs or other water-control structures that interfere with the migratory cycles 203 of fisheries organisms. If, as some people claim, however, such structures slow the conversion of vegetated marsh to open water, then such structures may be beneficial to fisheries in the long run. But this is a big, and important, "if." Therefore, we believe the statement just quoted from Herke (1979) should now be rephrased by substituting "marsh loss" in place of "nursery production (not standing crops)." Although such structures may help to save the marsh under some circumstances, we know of no published scientific study showing that they do so over the long term. The basis for such claims seems to be personal observations unsupported by controlled experimentation or critical analysis. On the other hand, there are a number of published indications that water-level control in the marsh may actually hasten loss of vegetation. Concerning semi-impoundments controlled by fixed- crest weirs, dams, and earthen plugs, Cowan et al. (1988) stated, "In some cases, land loss rates within the impoundments may increase due to hydrologic isolation in an otherwise tidally influenced area. Marshes in these impoundments tend to break up and die back to form open water." Some possible reasons for this follow. There is general agreement that the primary reason coastal Louisiana is losing land is because sediment deposition is not keeping pace with land subsidence and the rise in relative sea level (e.g., DeLaune et al. 1983; Salinas et al. 1986; Coalition To Restore Coastal Louisiana 1987; Walker et al. 1987). Moreover, the rate of eustatic (true) sea level rise is predicted to increase substantially during the next century because of the "greenhouse effect" (Titus 1986). The only way to counter this rise in relative sea level is to increase the rate at which sediment from the Mississippi River is introduced into the marsh. Semi-impoundment will have no effect on eustatic sea level rise, but will likely increase the rate of relative sea level rise by restricting the inflow of sediment-bearing water. The distribution of marsh plants is largely governed by the depth and duration of inundation of their roots, and the tolerance of the plants to salinity. Chabreck et al. (1979) found that weirs increased both the average depth and the duration of inundation. Semi-impoundment levees also affect the marsh water-level regime since even canal spoil banks that result in unintentional partial impoundment do so. Swenson and Turner (1987) found that, on the average, an area affected by such a spoil bank (1) was flooded 141 h more per month than the adjacent control area; (2) had fewer but longer flooding events; (3) had fewer but longer drying events; and (4) had reduced water exchange, both above- and belowground. They stated that the ecological significance of the monthly hydrologic averages may be overshadowed by the few but relatively stressful long periods of inundation. They also stated that the soil chemistry changes one would expect under these longer periods of flooding would be ecologically significant, particularly if sulphates were reduced to toxic sulfides. Wiregrass {Spartina patens) is the predominant plant in Louisiana brackish marsh, and smooth cordgrass {Spartina alterniflora) predominates in the saline marsh. The effect of prolonged inundation on wiregrass has not been definitely determined. In field tests, however, as the degree of soil drainage increased, height of smooth cordgrass increased in a significant linear fashion (Mendelssohn and Seneca 1980); continuous flooding resulted in a decline in growth and ultimately in dieback (Mendelssohn et al. 1981). Wicker et al. (1983) evaluated wetland management techniques on the Rockefeller State Wildlife Refuge and Game Preserve. The Price Lake unit of the preserve contains about 3,000 ha of brackish to saline marsh and shallow, open-water bodies; it is surrounded by levees, and water level is controlled by two standard fixed-crest weirs. They found that open water bodies are increasing in this unit, and stated, The factors responsible for the increasing marsh breakup are difficult to delineate, but levee enclosure and weirs may possibly contribute to the problem by maintaining higher-than-normal water levels." The preceding paragraph gives support to this hypothesis. Permit applications for marsh management practices that will involve the use of levees and water-control structures frequently cite the need to prevent saltwater intrusion, which the applicants believe to be a major cause of Louisiana's coastal land loss. Although saltwater does kill plants 204 not tolerant to it, saltwater intrusion at present is probably not the major cause of land loss. Walker et al. (1987) give their tentative ranking of nine causes of this loss. In order of decreasing importance, the first four are (1) change in the depositional site and stage in the delta cycle; (2) compaction and localized differential subsidence; (3) sea-level change and long-term climatic change; and (4) human modification of the Mississippi River system. They do not list saltwater intrusion per se, but their text indicates it is a result of canal dredging (cause 5) and fluid extraction (cause 8). Some (for example, Turner 1987) would place canal dredging and its accompanying levee construction higher on the list. There are publications (and general agreement) showing that these result in direct and indirect destruction of marsh; any disagreement on this matter is about the degree of the latter. Thus, no matter what the net effect of semi-impoundment on marsh loss, it always results in some marsh destruction. Moreover, unless the water-control structures are maintained, they become non-functional and any possible benefits from them are lost. Even so, the direct and indirect marsh loss caused by the canals and levees remains indefinite. MARICULTURE Mariculture is the raising of marine organisms under captive or controlled conditions. The United States now imports more shrimp than is caught domestically, and much of this imported shrimp is from mariculture in tropical and subtropical areas, mostly in "Third World" countries. Fortunes have been made there where labor is cheap, growing seasons are long, and the need for foreign exchange seems more urgent than protection of the environment. But these profits have come at a high environmental cost. Most mariculture has occurred in coastal zones, resulting in large-scale destruction of the mangroves. Mangrove areas are generally regarded to be important nursery and feeding grounds for wild fishery species (see, for example, Cortiguerra 1979; Prince Jeyaseelan and Krishnamurthy 1980; Ong 1982; and Camilleri and Ribi 1986). As such, mangrove areas are an ecological counterpart to Louisiana's coastal marshes. Fortunately, there is growing concern around the globe over the loss of mangroves, and scientists and governments are calling for or requiring measures to protect the mangrove areas (see, for example, Cortiguerra 1979 (the Phillipines); Ong 1982 (Malaysia); Soegiarto 1984 (Indonesia); and Snedaker et al. 1986 (Ecuador)). A few years ago a new Cajun-style dish called "blackened redfish" was an immediate and phenomenal success. It soon appeared on restaurant menus across the United States. As a result, demand for redfish and the dockside price of the fish soared. The fishing pressure put on the wild stocks was sufficient to raise fears that the population would be overfished. Some saw mariculture of redfish as a means to reduce pressure on the wild stock; others saw it as a source of public benefits such as increased employment; and still others saw it as a means to make huge profits as has been done by some Third World mariculturists. In 1987 the Louisiana legislature passed two bills authorizing use of the coastal marsh for mariculture. They were subsequently signed by then Governor Edwin Edwards and became Acts 305 and 386. Both acts indicated that a reasonable number of fish were to be released to the wild; both required that the mariculture operations take place within an area having a marsh management plan; and both allowed the Department of Wildlife and Fisheries to exempt the mariculturist from any limitations on how the organisms could be harvested. Act 305 authorized the issuance of up to 10 permits, good for 5 years, and not to encompass over 3,238 ha each; required all fishery organisms used in a project to be purchased from a legal source; and contained a number of guidelines to be followed. Act 386 contained none of these restrictions. We discuss these acts further in the following paragraphs. The release of hatchery-reared fish into the wild poses a threat to the wild stocks. The hatchery fish have very little genetic variability. Introduction of the genes of hatchery-reared fish into the wild gene pool will eventually diminish the capacity of wild fish to survive adverse environmental 205 fluctuations. (For further discussion of this subject, see Genetics Committee 1975.) As worded, both Acts allow, and appear to intend, that the mariculture is to take place on an extensive basis (i.e., over thousands of hectares). Both require a marsh management plan, which at the time the Acts were written, normally meant use of levees, weirs, or other water-control structures. Our work shows that such systems greatly reduce the number and total weight of many economically important fishes and shrimps that return to the gulf, even when the area is not used for mariculture (for example, see Tables 1 and 2 and Figure 5). Therefore, the Acts require management practices that we have shown reduce natural fishery production and which may also tend to hasten marsh loss. Even if the Acts did not require it, the mariculturist will have to use some means of preventing the cultured organisms from escaping. Whether the means are levees or screens, and even if used for only a portion of each year, there will be no period during which they will not interfere with the movement into and out of the area by numerous species (see Figure 2). Stocking of the area by wild species will be even further reduced, because the systems we studied contained no such complete barriers to inward movement of small organisms. Because it is totally impractical to feed fish in an area of thousands of hectares, the mariculturist may pen the hatchery fish into a few acres and feed them until they are better able to forage for themselves. This in itself causes problems. Unless water is artificially pumped through the area, decomposition of the feed and fecal matter will probably use up the oxygen in the water and result in death of the organisms. But if water is pumped, the poor quality water will be moved into the surrounding area and adversely affect natural production there. Once the fish are released into the total mariculture area they will be feeding primarily, if not exclusively, on the organisms produced there naturally. Thus, the cultured fish will be competing with and preying on the wild- produced fish and shrimp that are able to get into the area. Both Acts contain the statement that "accurate records shall be maintained on the separation of wild fish from domestic stock." Because Act 305 requires all fish used in a project to be purchased from a legal stock, it prohibits the sale of wild fish by the mariculturist. However, Act 386 does not specifically require that fish used in a project be purchased from a legal source. Thus it appears that under Act 386 wild young could be used to stock the area and could be held in the area until captured by the mariculturist and sold (despite the "accurate records" statement in the Act). At this point, we know of only three ways to attempt to maintain accurate records on the separation of wild fish from domestic stock. One way is to seal off the entire area so that there is no interchange of water between the mariculture area and outside waters, and then attempt to kill out everything in the maricultural area. We know of no poison, however, that is this effective and not illegal to use, nor do we know if these Acts can make such mass destruction legal, even if there were an approved poison. Also, unless the area were again opened to water circulation, the water would soon become devoid of oxygen and all the organisms in the area would die. On the other hand, if water circulation is restored, then wild young will enter the area. The second way would be to seal off the area at a time when there would likely be very few of the species to be cultured in the area. (It is doubtful if there is ever a time when one could be sure there is none in the area.) The culture organisms could then be stocked in the sealed off area. But, again, water circulation would have to be restored and wild organisms would enter. The third way would be to rear the cultured young to a size that can receive a permanent mark before release into the area. Even if this is done, it leaves the problem of how to harvest the cultured animals without harming the wild ones. With something large, like redfish, it might be possible to capture them all and then release the unmarked ones without harming too many. But with smaller and more delicate animals, such as shrimp, most of the unmarked shrimp would be harmed or killed in the capture process. This is especially true since the Acts allow harvest by any 206 means, and the most efficient means of harvesting shrimp is with a trap on the areas' outlet (just as we have done in our studies). Moreover, we know from our own experience that the even more fragile organisms that will be attempting to leave at the same time, such as menhaden and anchovies, will nearly all die in the traps before they can be released. From the preceding paragraphs, it can be seen that wild species will be inhibited or prevented from entering any area of extensive mariculture; those that do get in will have to compete with, and will be preyed upon by, the cultured species; and most of the surviving wild individuals will probably be killed as they attempt to leave the area. For all practical purposes, any area used for mariculture will be lost to the natural fishery. Mariculture proponents may say this will not affect the catch of wild species, but this is incorrect at least for shrimp, Louisiana's monetarily most important fishery. Turner (1977) found a statistically significant positive correlation between commercial yields of penaeid shrimp and area of intertidal vegetation, both in Louisiana and in 27 locations throughout the world. Also, according to Turner and Boesch (1987), similar findings were reported by Jothy (1984) for Malaysia, by Pauly and Ingles (in press) for the Philippines, and by Staples et al. (1985) for Australia. Although not as well documented, there is good reason to believe the same correlation holds for many species of sport and commercial finfish. Table 3 (derived from our quantitative 2-year study funded by the U.S. Soil Conservation Service; see "Fisheries Studies" section) shows the average annual export of fisheries organisms per hectare from our unweired pond. From trawl samples taken concurrently in that pond and an adjacent totally natural pond, it appears that even the presence of our trap system reduced production in the unweired pond. Thus the values in the table are probably underestimates of natural productivity for this region of the marsh. Also, natural productivity and species composition vary somewhat from region to region. Nevertheless, the table does give an indication of the amount of loss to natural production that will occur for each hectare of marsh used for mariculture. We fee such losses to mariculture represent losses of a public resource for the purpose of private gain. Note that the "all other species" category in Table 3 represents over 90 additional species. Most of these have no present direct economic value, sport or commercial, but their loss will have considerable indirect economic effect because many are important in the food web of species of direct economic value. Moreover, loss of production in the marsh will adversely affect production even of many offshore species that never enter the marsh. There is much in the scientific Table 3. Average annual number and weight per hectare of some economically important organisms exported from the unweired pond, February 1983 through February 1985. Weight Species Number (kg) Gulf menhaden 67,714 45.4 Atlantic croaker 19,971 32.2 Blue crab 10,200 81.1 Brown shrimp 8,600 24.3 White shrimp 8,229 21.7 Spot 1,543 6.5 Striped mullet 1,071 23.1 All other species 40,871 39.7 Total 158,199 274.0 207 literature about the importance of marsh detritus that is exported offshore. The exports, however, highest in energy content and probably in overall value are the organisms that use the marsh as a nursery. They serve as forage for the offshore fishes, without which these offshore fishes would probably be much less abundant; the survivors grow to become catchable sport and commercial estuarine-dependent fishes, and parents of their next generation. It may be that most of the "all other species" have their greatest importance in an ecological role. For nearly all species, we know far too little to say where they fit in the overall "big picture." Some of the species currently considered unimportant may be essential pieces in the ecological puzzle. The sudden demand for redfish and the increase in its dockside price was probably the main impetus for passage of Acts 305 and 386; Act 305 specifically gives red drum (redfish) as an example of a species that may be cultured. If redfish were the only species that were allowed to be cultured, we would not be so concerned about the Acts. We expect the blackened redfish fad to run the course of all fads, and the price of redfish to once again fall to historic levels. If this happens, it would probably be unprofitable to culture them and mariculture operations in the marsh would disappear. But the Acts allow culture of "any fish" (Act 386) and "domesticated and other aquatic species" except any "harmful species of fishery" (Act 305). It is obvious that a mariculturist can make a profit from shrimp (Table 3) if given an exclusive monopoly on shrimp raised in a large area of marsh. Thus, we do not expect to see maricultural operations disappear from the marsh for purely economic reasons. Concern about overfishing the wild redfish population also led to the first ever restrictions in Louisiana on the annual poundage of redfish that could be landed commercially, and closing of the season for sport fishing. Restrictions on harvest are certainly prudent measures if there is danger of overfishing to the extent of reducing recruitment of young into the fishable population. But the young redfish must have a place to grow before they can recruit into the fishable population. It is counterproductive to remove large chunks of their nursery and rearing area for mariculture while trying to increase the numbers of those surviving to spawning age. The threats to the fishery resource, and possibly to the marsh itself, from mariculture are our greatest concerns, but we will mention a few others. Mariculture is also a threat to waterfowl interests. Semi-impoundment has been used for years as a tool for increasing waterfowl food production, thereby improving the hunter's chance of success. The average hunter may expect that the semi-impoundment required for mariculture will do the same thing, but this is doubtful. The water level fluctuation schedules required for waterfowl food production, and those required for successful mariculture, are not likely to be the same. Unlike the freshwater crayfish ("crawfish") aquaculturist, the mariculturist can not accept a drawdown that results in a dense stand of seed-bearing annuals. And if the mariculturist artificially feeds the cultured organisms, water levels will probably be held too high for successful growth of widgeongrass (Ruppia maritima), particularly since decomposition of food and feces, eutrophication of the water, and roiling by the concentration of organisms in the area will all increase water turbidity. The artificially high water levels may also waterlog the soil, thereby killing the emergent vegetation. We generally disagree with the "Recognizing" statements in Act 305; for example, "...and recognizing... that mariculture is compatible with the social and cultural heritage of the coastal area..." (How many Louisiana shrimpers want to exchange their independent life style for the "tied down to routines" life of a farmer?) We particularly doubt that mariculture will reduce unemployment. In 1987, Louisiana had over 26,000 licensed resident commercial fishing vessels. Marsh removed for mariculture will result in a reduction in natural fishery production. The reduction in natural fishery catch because of mariculture will probably result in more unemployment in the commercial fishery than it will in employment in mariculture. The 26,000 licensed vessels in 1987 is a considerable increase over 1986 (19,500 vessels). The increase probably resulted from (1) a change in the law making licensing requirements more enforceable, and (2) the depressed economy and layoffs in other occupations, which likely meant 208 a lower per capita income for the fishermen. Nevertheless, the commercial fishery was able to absorb the additional fishermen, thereby decreasing unemployment and the burden that unemployment places on the State. Maricultural operations cannot hire large numbers of suddenly unemployed people. Neither can the suddenly unemployed start mariculturafoperations themselves. Maricultural operations require control of land and water, and large amounts of capital. Extensive mariculture is the province of the large landowner, the wealthy individual, and the well-financed corporation. In addition to those licensed to fish commercially, about 200,000 men and women in Louisiana purchase a saltwater fishing license each year. Maricultural operations envisioned in the Acts will result in reduction in the abundance of the species sought by saltwater anglers; reduction in the quality of fishing; and could eventually result in the direct loss of access to a large percentage of the fishing waters to which the public has traditionally had access. This in turn will result in a loss of expenditures and employment in the service areas for sport fishing (e.g., boat and motor sales, transportation, lodging, tackle). Additional losses will occur in the tourist industry because our reknowned saltwater sport fishing is frequently one of the incentives for visiting Louisiana. For additional information on this subject, see Herke (1972, 1976, 1977, 1978). CONCLUSIONS 1. Most of Louisiana's important sport and commercial fisheries species must be able to migrate between the Gulf of Mexico and their coastal marsh nursery if they are to maintain fishable populations. 2. Semi-impoundment by such means as levees, weirs, or other water-control structures interferes with the migratory cycles, and seriously reduces the populations, of fishery species. 3. The loss of fishery production over the short term is acceptable only if semi-impoundment results in a sufficiently compensatory reduction of marsh nursery loss over the long term. 4. There is no adequately documented, scientific study in the published literature that shows semi-impoundment reduces marsh loss over the long term. 5. There are a number of studies in the published literature that indicate semi-impoundment may hasten marsh loss. There are also many other questions regarding semi-impoundment. Until these questions are answered, the attempted "cure" for marsh loss may in many cases may hurt more than it helps. We believe the most expeditious way to determine whether semi-impoundment hastens or retards marsh loss is through the critical examination of aerial imagery of areas that have long been affected by semi-impoundment, and similar areas not so affected. This examination would have to include areas outside the semi-impoundment for which the drainage is not affected by the levees or other structures of the semi- impoundment. (Areas immediately adjacent to the semi-impoundments may have suffered increased land loss caused by altered drainage because of construction of the semi- impoundment.) 6. Mariculture in the marsh will result in an overall loss of fishery production and possibly other damages such as increased unemployment; conversion of resources belonging to the general public to the profit of a relatively few individuals and corporations; and loss of public access to areas traditionally open to fishing. If mariculture is allowed in the marsh, we foresee the decimation of our natural fisheries, both sport and commercial. In our opinion, Acts 305 and 386 of the 1987 Louisiana Legislature are not in the public interest and should be repealed. 209 LITERATURE CITED Bradshaw, W.H. 1985. Relative abundance of small brown shrimp as influenced by semi- impoundment. M.S. Thesis. Louisiana State University, Baton Rouge. 61 pp. Camilleri, J.C., and G. Ribi. 1986. Leaching of dissolved organic carbon (DOC) from dead leaves, formation of flakes from DOC, and feeding on flakes by crustaceans in mangroves. Mar. Biol. 91:337-344. Chabreck, R.H., R.J. Hoar, and W.D. Larrick, Jr. 1979. Soil and water characteristics of coastal marshes influenced by weirs. Pages 129-146 in J.W. Day, Jr., D.D. Culley, Jr., R.E. Turner, and A.J. Mumphrey, Jr., eds. Proceedings of the third coastal marsh and estuary management symposium. Louisiana State University, Division of Continuing Education, Baton Rouge. Coalition To Restore Coastal Louisiana. 1987. Coastal Louisiana: here today and gone tomorrow? Coalition To Restore Coastal Louisiana, 3420 Prytania Street, New Orleans. 66 pp. [Draft for public review.] Cortiguerra, A.G. 1979. Mangrove and estuarine ecology in the Philippines. Canopy (October) 5(10):8-10,14. Cowan, J.H., Jr., R.E. Turner, and D.R. Cahoon. 1988. Marsh management plans in practice: do they work in coastal Louisiana, USA? Environ. Manage. 12(l):37-53. DeLaune, R.D., R.H. Baumann, and J.G. Gosselink. 1983. Relationships among vertical accretion, coastal submergence, and erosion in a Louisiana gulf coast marsh. J. Sediment. Petrol. 53(1):147- 157. Genetics Committee, Alaska District of the American Institute of Fishery Research Biologists. 1975. Salmon hatcheries-moving too fast? Alaska Seas Coasts 3(2):8-10. [Published by the University of Alaska Sea Grant Program.] Herke, W.H. 1968. Weirs, potholes and fishery management. Pages 193-211 in J.D. Newsom, ed. Proceedings of the marsh and estuary management symposium. Thomas J. Moran's Sons, Inc., Baton Rouge, LA. Herke, W.H. 1971. Use of natural, and semi-impounded, Louisiana tidal marshes as nurseries for fishes and crustaceans. Ph.D. Dissertation. Louisiana State University, Baton Rouge. 264 pp. University Microfilms, Ann Arbor, MI. (Dissert. Abstr. 32:2654-B.) Herke, W.H. 1972. Mariculture. Oceans 5(3):78. Herke, W.H. 1976. 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Sabine fisheries study: a study of the seasonal presence, relative abundance, movements, and use of habitat types by estuarine-dependent fishes and economically important decapod crustaceans on the Sabine National Wildlife Refuge. Louisiana State University Agricultural Center, Baton Rouge. 3 vol. Herke, W.H., B.D. Rogers, and E.E. Knudsen. 1984b. Habits and habitats of young spotted seatrout in Louisiana marshes. La. State Univ. Agric. Center Res. Rep. No. 3, Baton Rouge. 48 pp. 210 Herke, W.H., E.E. Knudsen, Z.X. Chen, N.S. Green, P.A Knudsen, and B.D. Rogers. 1987a. Final report for the Cameron-Creole watershed fisheries investigations. Louisiana State University Agricultural Center, Baton Rouge. 419 pp. Herke, W.H., E.E. Knudsen, P.A. Knudsen, and B.D. Rogers. 1987b. ^ Effects of semi- impoundment on fish and crustacean nursery use: evaluation of a "solution." Pages 2562-2576 in O. T. Magoon, H. Converse, D. Miner, L.T. Tobin, D. Clark, and G. Domurat, eds. Coastal Zone '87: proceedings of the fifth symposium on coastal and ocean management. American Society of Civil Engineers, New York. Jothy, AA 1984. Capture fisheries and the mangrove ecosystem. Pages 129-141 in J.E. Ong and W.K. Gong, ed. Productivity of the mangrove ecosystem: management implications. UNESCO/UNDP Regional Project; UNIT Pencetakan Tusat, University Sains Malaysia. Mendelssohn, I. A, and E.D. Seneca. 1980. The influence of soil drainage on the growth of salt marsh cordgrass Spartina alterniflora in North Carolina. Estuarine Coastal Mar. Sci. 2:27-40. Mendelssohn, LA, K.L. McKee, and W.H. Patrick, Jr. 1981. Oxygen deficiency in Spartina alterniflora roots: metabolic adaptation to anoxia. Science 214:439- 441. Ong, J.E. 1982. Mangroves and aquaculture. Ambio ll(5):252-257. Pauly, D., and J. Ingles. The relationships between shrimp yields and intertidal vegetation (mangroves) areas: a reassessment. Proceedings Recruitment Workshop, Ciudad de Carmon, Mexico, April 1986. In press. — Prince Jeyaseelan, M.J., and K Krishnamurthy. 1980. Role of mangrove forests of Pichavaram as fish nurseries. Proc. Indian Natl. Sci. Acad. B 46 No. 1:48-53. Rogers, B.D., and W.H. Herke. 1985. Estuarine-dependent fish and crustacean movements and weir management. Pages 201-219 in C.F. Bryan, P.J. Zwank, and R.H. Chabreck, eds. Proceedings of the fourth coastal marsh and estuary management symposium. Louisiana State University Agricultural Center, Baton Rouge. Rogers, B.D., W.H. Herke, and E.E. Knudsen. 1987. Investigation of a weir-design alternative for coastal fisheries benefits. Louisiana State University Agricultural Center, Baton Rouge. 98 pp. Salinas, L.M., R.D. DeLaune, and W.H. Patrick, Jr. 1986. Changes occurring along a rapidly submerging coastal area: Louisiana, USA J. Coastal Res. 2(3):269-284. Schultz. T.W. 1985. Diel movement of brown shrimp (Penaeus aztecus) at a southwest Louisiana estuarine lake-marsh interface. M.S. Thesis. Louisiana State University, Baton Rouge. 93 pp. Snedaker, S.C., J.C. Dickinson, III, M.S. Brown, and E.J. Lahmann. 1986. Shrimp pond siting and management alternatives in mangrove ecosystems in Ecuador. Rosenstiel School of Marine and Atmospheric Science, University of Miami, FL. 77 pp. Soegiarto, A 1984. The mangrove ecosystem in Indonesia, its problems and management. Pages 69-78 in H.J. Teas, ed. Physiology and management of mangroves. W. Junk TVS 9, The Hague. Staples, D.J., D.J. Vance, and D.S. Heales. 1985. Habitat requirements of juvenile penaeid prawns and their relationship to offshore fisheries. Pages 47-54 in P.C. Rothlisbergy, B.J. Hill, and D.J. Staples, eds. Second Australian National Prawn Seminar, NPS2, Cleveland, Australia. Swenson, E.M., and R.E. Turner. 1987. Spoil banks: effects on a coastal marsh water-level regime. Estuarine Coastal Shelf Sci. 24:599-609. Titus, J. G. 1986. Greenhouse effect, sea level rise, and coastal zone management. Coastal Zone Manage. J. 14(3):147-171. Turner, R.E. 1977. Intertidal vegetation and commercial yields of penaeid shrimp. Trans. Am. Fish. Soc. 106(5):41 1-416. Turner, R.E. 1987. Relationship between canal and levee density and coastal land loss in Louisiana. U.S. Fish Wildl. Serv. Biol. Rep. 85(14). 60 pp. Turner, R.E., and D.F. Boesch. 1987. Aquatic animal production and wetland relationships: insights gleaned following wetland loss or gain. Pages 25-39 in D. Hook, ed. The ecology and 211 management of wetlands. Vol. 1: Ecology of wetlands. Croom Helm, Limited, Beckenham, Kent, U.K. Walker, H.J., J.M. Coleman, H.H. Roberts, and R.S. Tye. 1987. Wetland loss in Louisiana. Geografiska Annaler 69 A (l):189-200. Weaver, J.E., and L.F. Holloway. 1974. Community structure of fishes and macrocrustaceans in ponds of a Louisiana tidal march [sic] influenced by weirs. Contrib. Mar. Sci. 18:57-69. Wengert, M.W., Jr. 1972. Dynamics of the brown shrimp, Penaeus aztecus aztecus Ives 1891, in the estuarine area of Marsh Island, Louisiana, in 1971. M.S. Thesis. Louisiana State University, Baton Rouge. 94 pp. Wicker, KM., D. Davis, and D. Roberts. 1983. Rockefeller State Wildlife Refuge and Game Preserve: evaluation of wetland management techniques. Louisiana Department of Natural Resources, Coastal Management Section, Baton Rouge. 212 RECREATIONAL USE OF MANAGEMENT UNITS IN BRACKISH MARSH Richard B. Davidson Louisiana Department of Wildlife and Fisheries P. 0. Box 585 Opelousas, LA 70358 Robert H. Chabreck School of Forestry, Wildlife and Fisheries Louisiana State University Agricultural Center Baton Rouge, LA 70803 ABSTRACT Recreational use was investigated in two impoundments and a semi-impounded (weir) area in brackish marsh. The study was conducted on Rockefeller Wildlife Refuge in southwestern Louisiana, and a visitor survey and creel census were conducted during 1981. The visitor survey disclosed that 165,162 user-hours were spent on the study area in 1981. Primary activities were fishing, crabbing, and castnetting for shrimp. Visitors harvested 77,819 kg of fish and shellfish. Brown and white shrimp made up 57.1% of the harvest. Shrimp were taken only with cast nets and 93.1% were taken from weirs and water control structures in impoundments. Fish taken in greatest abundance were alligator gars (7,247 kg) and redfish (7,569 kg). Of the alligator gars, 70.5% were taken from impoundments; 70.6% of the redfish were taken outside the impoundments. Competition for castnetting sites at water control structures often limited recreational opportunities for that activity. Because of the great interest in castnetting for shrimp and the lack of suitable castnetting sites during peak shrimp movement periods, future development should include water control structures and facilities to accommodate this activity. INTRODUCTION Brackish marsh impoundments are widely used in coastal areas as a mechanism for wildlife habitat improvement. Impoundments are constructed by completely enclosing a marsh area with a levee system. Impoundment construction began on Rockefeller Refuge in 1954, and water control structures were installed in levee systems to provide a means for regulating water depth and salinity (Chabreck 1960). Waterfowl use of brackish marsh impoundments has been the subject of several investigations (Chabreck 1960; Baldwin 1967; Chabreck et al. 1974; Morgan et al. 1975). Recreational use, however, has received little attention. As the need for multiple use of land and waters increases, additional information on all potential impoundment uses becomes increasingly important. Impoundment management for one species or group of species is often compatible with management of other species. Manipulation of water levels in freshwater marsh impoundments is beneficial to both ducks and crawfish {Procambarus clarkii) (Perry et al. 1970). Management of a brackish marsh impoundment for ducks involves permanently flooding the area to a depth of 0.2 to 0.4 m for 3 to 4 years. At the end of the period, the area is temporarily 213 dried during the summer and reflooded. The temporary drying causes pond bottoms to become firm, thus reducing water turbidity and enhancing the growth of aquatic plants when the area is reflooded (Chabreck 1960). This management procedure has been modified on Lake 4 on Rockefeller Refuge to include a fishery management program. Waterways outside the impoundment are periodically sampled for shrimp during the spring and summer. When post-larval shrimp are present in adequate numbers, water control structures are opened on high tides so postlarvae can enter the impoundment. Excellent stocking often results and growth rates are equal to those in natural waters. The impoundment is open to sport fishing and numerous fishermen visit the refuge to harvest shrimp and other fishery resources. The relationship of the duck management program to the fishery management program has not been evaluated. The objectives of this study were to investigate the recreational use of impounded and semi-impounded brackish marsh and to evaluate methods of enhancing recreational values. METHODS AND MATERIALS Study Area Rockefeller Wildlife Refuge, a State-owned area in Cameron and Vermilion Parishes in south- western Louisiana, occupies about 30,876 ha of coastal marshes between the Grand Chenier-Pecan Island beach ridge complex and the Gulf of Mexico. The refuge is operated by the Louisiana Department of Wildlife and Fisheries and has been intensively developed for wildlife. The study area includes two brackish marsh impoundments, Lakes 3 and 4, and the semi-impounded Miller Lake weir area, all within the western portion of the refuge. These impoundments all border the Humble Canal, a major outlet to the Gulf of Mexico. The visitor-use survey included all areas accessible via Humble Canal and adjoining canals. Lake 3 encompasses 1,740 ha. Water levels are controlled with a concrete, variable crested, reversible flap-gate control structure on the Headquarters Canal in the northeast corner of the unit and are manipulated by gravity drainage. The primary management objective is the propagation of important waterfowl food plants. Emergent, perennial vegetation grows on over 49.7% of the area; the remainder of the area is shallow ponds except for a canal 10 m wide along the east side. Lake 4 encompasses 2,270 ha, of which 53.4% contains emergent, perennial vegetation and the remainder is shallow water area. Canals border the west and south sides of the impoundment. Water levels are controlled with a concrete control structure containing seven variable crested, aluminum flap-gates located in the southwest corner of the unit. Wicker et al. (1983) provided a detailed description of this control structure. The primary management objectives are centered around the multiple-use of the unit by both estuarine fisheries species and waterfowl species. The water control structure is operated to allow postlarvae shrimp and fishes to enter the unit during times of peak abundance, yet water levels are maintained to produce conditions favorable to the growth of widgeongrass (Ruppia maritima) and other waterfowl-food plants in the ponds and to maintain water depths (0.4 m) necessary for dabbling ducks to feed. - The Miller Lake weir area encompasses 2,480 ha of brackish to saline marsh and shallow open water bodies and receives no special management. Two weirs are located in the east levee system and permit tide water from the Humble Canal to flow in and out. The weirs reduce tidal exchange 214 and water levels are stabilized behind the weirs to enhance waterfowl food plant growth (Chabreck and Hoffpauir 1962). The area behind the weirs is semi-impounded (Herke 1971). Marsh with emergent, perennial vegetation makes up 80.6% of the area with the remainder being shallow ponds. A small bayou leads from the weirs and meanders through the area. CREEL CENSUS Shrimping, crabbing, and fishing were the primary forms of recreation in the management units. Participants entered the area by boat and launched at the Humble Canal landing on Rockefeller Refuge at Grand Chenier. User activities and characteristics were determined by creel census as visitors departed from the refuge via the landing. The creel census was of the access point type as described by Hayne (1976). Information gathered from occupants in each boat included number in the party, distance traveled to the refuge, areas visited, time spent at each area, weight of each species taken, method of fishing, and time for each method. The creel census was conducted during visiting hours (sunrise to sunset) on randomly selected sampling dates throughout 1981. Sampling seasons were used in place of months; weekdays were assigned half the probability of being selected as were weekends and holidays. User days were divided into low-use (Monday through Friday) and high-use (weekends and holidays) for the purpose of sampling, and the number of creel censuses on high-use days was twice that of low-use days. The number of days of the creel census was based on a stratification that assumed much more use on weekends than weekdays. Each sampling day was divided into four equal periods, and two randomly determined periods were checked. Visitor use and harvest data were also collected based on periods of the year. Five periods were identified: period 1 (January, February, and December; refuge closed, except major canals); period 2 (1 March to 17 May; refuge open, shrimp limited to 4.5 kg/party); period 3 (18 May to 8 July; refuge open, shrimp limited to 45 kg/party); period 4 (9 July to 16 August; refuge open, shrimp limited to 4.5 kg/party); period 5 (17 August to 30 November; refuge open, shrimp limited to 45 kg/party). RESULTS AND DISCUSSION Visitor Characteristics We interviewed 805 parties that launched at the Humble Canal boat ramp on Rockefeller Refuge during 1981. They had traveled an average of 124.5 km (S.E. = 1.32) from their point of origin to the refuge (Table 1). The maximum distance traveled was 1,247 km. Statewide, 70% of saltwater anglers travel less than 80 km to fishing sites (Gosselink et al. 1979). Marine anglers nationally travel approximately 370 km from their homes to their fishing sites (National Marine Fisheries Service 1981). The difference is possibly because of the low human population density within 80 km of the Humble Canal boat launch and the location of two major metropolitan areas (Lafayette and Lake Charles, Louisiana) approximately 120 km away. Almost 70% of all anglers nationally live in metropolitan areas (U.S. Dept. of Interior 1977). The sampling period with the lowest mean distance traveled was period 1, when the refuge was almost entirely closed to recreation except for access to the gulf and for activities in the Humble and Headquarters Canals. The greatest mean distances were traveled during periods 3 and 5, when the shrimp possession limit was 45 kg/day (Table 1). Average party size (persons per boat) during 1981 was 3.14. Mean party size varied from 2.91 persons/party during period 1 to 3.38 persons/party during period 3. The second lowest mean party 215 Table 1. Mean user characteristics, Humble Canal area, Rockefeller Refuge, Cameron Parish, Louisiana, 1981. Characteristic Distance traveled Period8 Party size (km) User-hours/party 1 2.91 101.56 4.45 2 3.31 118.44 5.09 3 3.38 130.62 5.45 4 3.07 117.47 5.39 5 2.97 125.39 6.59 1-5 3.14 124.50 5.88 aSee "Creel Census" section for period descriptions. size was observed during period 5. The impounded Lakes 3 and 4 and the semi-impounded Miller Lake weir were restricted areas with no recreational activities permitted during period 1, thus limiting activities to rod and reel fishing, crabbing, and oystering on unrestricted refuge areas and to trawling and rod and reel fishing offshore. The large mean party size during period 3 was possibly a result of the shrimp possession limit of 45 kg per party. When castnetting for shrimp, parties included additional people to crab at the same site. The small mean party size during period 5, when the shrimp possession limit was also 45 kg/party, may have been a result of more people fishing for redfish and less shrimping. Each party spent an average of 5.88 h on the refuge with a low of 4.45 h during period 1 and a high of 6.59 h during period 5 (Table 1). Shrimp possession limit during period 5 was also set at 45 kg per party, but the smaller mean party size during period 5 required each party to remain on the refuge longer in an attempt to catch their limit of 45 kg. The difference in the time spent on the refuge by each party between period 3 and period 5, the periods when 45 kg of shrimp/party could be harvested, may also have resulted from possibly greater catch rates during period 3. VISITOR ACTIVITIES Approximately 30% of Louisiana residents fish in saltwater (Louisiana State Parks Recreational Commission 1974). The parishes (counties) nearest Rockefeller Refuge (Calcasieu, Cameron, and Vermilion) account for about 12.5% of resident fishing license sales in Louisiana (Gosselink et al. 1979) and only 5.35% of the State population (U.S. Dep. of Commerce 1982). The user survey conducted in 1981 indicated that visitors entering Rockefeller Refuge by way of the Humble Canal landing spent 135,221 user-hours on the study area (Table 2). Castnetting for shrimp and oystering were activities conducted entirely on the refuge. Rod and reel fishing and crabbing were centered mainly on the refuge but some fewer were conducted offshore in the Gulf of Mexico. Trawling, an activity not permitted on the refuge, was limited to offshore. Shrimpers visiting the refuge have a choice of castnetting on the refuge, primarily in Lakes 3 and 4 and at the Miller Lake weir, or trawling nearby in the gulf. The number, however, of user- hours spent castnetting was about 4 times greater than the number trawling. 216 Table 2. Total user-hours/day by period of the year for different types of activities by persons entering Rockefeller Refuge at the Humble Canal landing, 1981. Type Periods8 activity 1 2 3 4 5 Mean — User-hours/day- Rod/reel 78.27 558.78 541.88 289.02 638.06 421.20 Castnetting 0.00 6.52 536.89 15.61 583.31 228.47 Trawling 8.35 34.64 69.87 81.55 52.91 49.46 Crabbing 7.45 58.71 71.28 60.68 131.52 65.93 Oystering 22.53 6.69 0.00 0.00 23.86 10.62 Total 116.60 665.34 1,219.92 446.86 1,429.66 775.68 aSee "Creel Census" section for period descriptions. Greatest daily use by visitors in the Humble Canal area were during periods 3 and 5 (Table 2) and attributed to the fact that the shrimp take was set at 45 kg (100 lb)/party or boat. Castnetting during the year was limited mostly to these periods. Castnetters on Rockefeller spent 83,392 user- hours during 1981. No previous studies of recreational castnetting were found in the literature. The U.S. Army Corps of Engineers (unpubl., as cited in Gosselink et al. 1979) found that anglers in southwestern Louisiana (Vermilion Bay west to Sabine Pass) spent 479,000 user-days/year sport shrimping. Juneau and Pollard (1981) observed that recreational shrimpers in 24,700 ha of Vermilion Bay spent 22,064 boat-hours trawling/year. Party size was not considered in the latter study so user-hours/year was probably much greater than the stated value. The 18,052 user- hours/year spent by recreational trawlers launching from the Humble Canal boat ramp are considerably less than those reported by Juneau and Pollard (1981). The availability of other launch sites with access to waters open to trawling and near major population centers is a possible reason for the relatively small amount of recreational trawling by persons launching from the Humble Canal boat ramp. Also, sport shrimpers may have preferred to trawl in the protected waters of Vermilion Bay rather than the Gulf of Mexico offshore from Rockefeller Refuge. Rod and reel fishing was a popular activity most of the year but declined in period 4 when castnetting for shrimp was limited to 4.5 kg/party. Many visitors apparently engage in several activities while on the refuge and castnet for shrimp a portion of the time and fish or crab during the remainder. Visitors launching from the Humble Canal boat ramp spent 153,738 user-hours engaged in recreational rod and reel fishing mostly outside the study area. Sport anglers in southwestern Louisiana spend 479,000 user-days per year in recreational fishing (U.S. Army Corps of Engineers, unpubl., cited by Gosselink et al. 1979). Heffeman et al. (1977) in a study of the finfish harvest of Galveston Bay, TX, estimated that recreational rod and reel fishermen spent 909,000 user-days/year in that area. The tremendous differences in user-days/year are a result of the much larger area available in Galveston Bay than along the southwestern Louisiana coast and the much greater human population density in the immediate vicinity of Galveston Bay. Visitors to Rockefeller Refuge are limited by the number of fishing areas available unless they intend to go offshore. If offshore activity is their only objective, other boat launches closer to their point of origin are in most cases readily available. 217 Visitors engaged in crabbing spent the most time pursuing their activity during period 5 and the least amount during period 1 (Table 2). Sport crabbers on Rockefeller spent 24,064 user-hours during 1981 while those in southwestern Louisiana spend 378,000 user-days/year (U.S. Army Corps of Engineers, unpubl., cited by Gosselink et al. 1979). Persons engaged in recreational oyster tonging on the study area spent the most time tonging during periods 1 and 5 (Table 2). No parties interviewed were engaged in oyster tonging during periods 3 and 4, the time of year when oysters are thought to be "bad." It is traditional in Louisiana to harvest oysters only during the months with the letter "r" in their spelling (i.e., not during the warmer months of May-August). Oyster tongers were active 3,876 user-hours during 1981. Greatest visitor use of an area occurred at the Miller Lake weir in period 3 and at other areas outside the management units in period 5 (Table 3). Castnetters were attracted to the weir by the abundance of brown shrimp in period 3. Fishermen sought speckled trout and redfish outside the management units in period 5, when the shrimp take was limited to 45 kg/party. The number of user-hours/day was often limited to the drainage structure in Lake 4 and the weir by the number of castnetting sites available. Visitors often left the refuge without castnetting or participated in other activities, such as crabbing or fishing, when castnetting sites were not available at these structures. RECREATIONAL HARVEST Visitors entering Rockefeller Refuge at the Humble Canal landing in 1981 harvested 81,666 kg of fish and shellfish representing 15 species (Table 4). Shrimp made up 54.4% of the harvest (brown shrimp, 28.8%; white shrimp, 25.7%). The shrimp were taken by castnetting; 93.1% were taken at the Miller Lake weir and in Lake 4. The harvest of white shrimp was similar in both Table 3. Total user-hours/day by periods of the year for different areas visited by persons entering Rockefeller Refuge at the Humble Canal landing, 1981. Area Periods8 visited 1 2 3 4 5 Mean User Lake 3 0.00 94.99 28.76 28.62 28.90 36.25 Lake 4 0.00 125.73 202.88 29.19 327.47 137.06 Weir 4.22 54.67 557.46 17.28 352.19 197.16 Offshore6 25.84 108.72 174.63 219.77 171.68 140.13 Otherc 86.54 281.23 256.19 152.00 549.42 265.08 Total 116.60 665.34 1,219.92 446.86 1,429.66 775.68 aSee "Creel Census" section for period descriptions. bAll areas seaward of Joseph's Harbor. CA11 areas within the refuge boundaries other than Lake 3, Lake 4, and the Miller Lake weir area. 218 Table 4. Recreational harvest (kg) of fish and shellfish in impoundments, weir area, and other areas in Humble Canal system, Rockefeller Refuge, 1981. Lake Lake Miller Lake Other Species 3 4 weir areas8 Alligator gar 3,7% 850 463 2,138 (3,924)b (250) (24) (502) Longnose gar 0 0 19 0 Spotted gar 0 0 0 4 Sea catfish 118 14 0 250 Gafftopsail catfish 0 0 0 37 Black drum 68 211 639 2,945 (69) (33) (516) (1,709) Atlantic croaker 0 90 0 551 (235) Speckled trout 0 20 35 (30) 1,878 (1,041) Redfish 192 1,382 389 5,606 (148) (589) (589) (3,024) Sheepshead 0 18 19 52 Southern flounder 0 99 (36) 12 381 (157) Brown shrimp 34 2,420 21,013 22 (4) (1,000) (6,074) White shrimp 439 9,564 8,385 2,574 (363) (4,442) (3,816) (1,148) Blue crab 512 2,980 2,339 4,723 (103) (850) (369) (843) Oysterc 0 0 0 4,375 (519) includes areas on the refuge outside the management units. 'Value in parenthesis is standard deviation. cHarvest expressed in liters. areas but that of brown shrimp was over 8 times greater at the weir than in Lake 4. The harvest of both species was small in Lake 3. The drying of Lakes 3 and 4 during the spring and early summer probably reduced brown shrimp production. Water control structures on Lake 3 were inoperative by summer and apparently reduced access by white shrimp. Blue crabs were taken in abundance throughout the study area and the harvest totaled 10,554 kg, with 55.2% taken from the impoundments and weir area. Alligator gar (7,247 kg) and redfish (7,570 kg) were the finfish taken in greatest amounts on the study area. Of the alligator gars taken, 70.5% were taken from within the management units, and 74.1% of the redfish were taken outside the management units. 219 CONCLUSIONS The primary purpose of the impoundments and semi-impounded area is wildlife habitat improve- ment. Most management is designed to attract migratory ducks; however, Lake 4 is maintained as a multiple-use impoundment and water control structures are operated to permit ingress and egress of estuarine-dependent and recreationally valuable species such as brown shrimp and white shrimp. The Miller Lake weir area receives no special management attention but the two weirs stabilize water levels and salinities and provide a stable environment for shrimp production. Since the saltwater angler population is growing at a rate twice as great as the overall population, methods to satisfy this growing pressure on coastal sport Fisheries resources need to be investigated (Stroud 1978). As congestion increases, the value of the recreational experience decreases. Efforts must be made to provide additional access for fishing or shrimping. Any project, however, must fully consider the preservation of estuarine and shoreline habitats and must not conflict with the primary objectives of the management unit. As part of the waterfowl management program on the study area, Lakes 3 and 4 are drained every 3 to 4 years to maximize production of aquatic plants. A program designed to drain these impoundments on different years would provide greater recreational access because there would be no year when both Lake 3 and Lake 4 are dry. Also, recreational usage of Lake 3 could possibly be increased if its management was similar to the multiple-use management program implemented in Lake 4. The water control structures for the impoundments and the weir area should be modified to provide suitable castnetting sites. During peak shrimp movement periods, all available sites remain occupied, causing many people to change plans and participate in other activities or leave the refuge. Construction of shoreline walkways adjacent to the control structures could possibly provide these additional castnetting sites. LITERATURE CITED Baldwin, W.P. 1967. Impoundments for waterfowl on South Atlantic and gulf coastal marshes. Pages 127-133 in J.D. Newson, ed. Proceedings of the first coastal marsh and estuary management symposium. Louisiana State University, Baton Rouge. Chabreck, R.H. 1960. Coastal marsh impoundments for ducks in Louisiana. Proc. Annu. Conf. Southeast. Assoc. Game Fish Comm. 14:24-29. Chabreck, R.H., and CM. Hoffpauir. 1962. The use of weirs in coastal marsh management units in Louisiana. Proc. Annu. Conf. Southeast. Assoc. Game Fish Comm. 16:103-112. Chabreck, R.H., R.K. Yancey, and L. McNease. 1974. Duck usage of management units in the Louisiana coastal marshes. Proc. Annu. Conf. Southeast. Assoc. Game Fish Comm. 28:507- 516. Devel, D.G. 1973. 1970 salt-water angling survey. Curr. Fish. Stat. No. 6200. U.S. Dep. Comm. NOAA, NMFS. 54 pp. Funicelli, N.A., and H.M. Rogers. 1981. Reduced freshwater inflow impacts on estuaries. Pages 214-219 in R.C. Carey, P.S. Markovits, and J.B. Kirkwood, eds. Proceedings of a U.S. Fish and Wildlife Service workshop on coastal ecosystems of Southeast United States. U.S. Fish and Wildlife Service. 220 Gosselink, J.G., C.L. Cordes, and J.W. Parsons. 1979. An ecological characterization study of the Chenier Plain coastal ecosystem of Louisiana and Texas. 3 vols. U.S. Fish Wildl. Serv., Biol. Serv. Program FWS/OBS-78/08-78/11. Hayne, D.W. 1976. Field forms for fishing, hunting, and other recreational surveys. North Carolina State University, Inst, of Statistics. 18 pp. Heffeman, T.L., AW. Green, L.W. McEachron, M.G. Weixelman, P.W. Hammerschmidt, and R.A. Harrington. 1977. Survey of finfish harvest of selected Texas bays. Segment 1. Tex. Parks Wildl. Dep. Tech. Rep. Herke, W.H. 1971. Use of natural and semi-impounded Louisiana tidal marshes as nurseries for fishes and crustaceans. Ph.D. Dissertation. Louisiana State University, Baton Rouge. 264 pp. Juneau, C.L, Jr. and J.F. Pollard. 1981. A survey of the recreational shrimp and finfish harvests of the Vermilion Bay area and their impact on commercial fishery resources. Louisiana Department Wildlife and Fishery, New Orleans. 40 pp. Louisiana State Parks and Recreational Commission. 1974. Louisiana State comprehensive outdoor recreational plan. Baton Rouge. Malvestuto, S.P., W.D. Davies and W.L. Shelton. 1978. An evaluation of the roving creel survey with nonuniform probability sampling. Trans. Am. Fish. Soc. 107(2):255-262. Morgan, P.AS., Johnson, W.P. Baldwin, and J.L. Landers. 1975. Characteristics and management of tidal impoundments for wildlife in a South Carolina estuary. Proc. Annu. Conf. Southeast. Assoc. Game Fish Comm. 29:526-539. National Marine Fisheries Service. 1981. Socioeconomic survey, executive summary. Seattle, WA Perry, W.G., Jr., T. Joanen, and L. McNease. 1970. Crawfish-waterfowl, a multiple use concept for impounded marshes. Proc. Annu. Conf. Southeast. Assoc. Game and Fish Comm. 24:506- 513. Stroud, R.H. 1977. Changing challenges in recreational fisheries. Seminar lecture, Texas A & M Univ., College Station, TX. Stroud, R.H. 1978. Biting the saltwater angling bullet. Sport Fish. Inst. Bull. 299. U.S. Dept. of Commerce. 1982. 1980 census of population. Vol. 1: Characteristics of the population. Chapter A Number of inhabitants. Part 20: Louisiana. U.S. Department of the Interior. 1977. 1975 National survey of hunting, fishing and wildlife- associated recreation. U.S. Fish and Wildlife Service, Washington, DC. Walford, L. 1968. Values of the South Atlantic and gulf coast marshes and estuaries to sport fisheries resources. Pages 70-82 in J.D. Newsom, ed. Proceedings of the first marsh and estuary management symposium. Louisiana State University, Baton Rouge. Wicker, K.M., D. Davis, and D. Roberts. 1983. Rockefeller State Wildlife Refuge and Game Preserve: evaluation of wetland management techniques. Louisiana Department of Natural Resources Coastal Management Section, Baton Rouge. 94 pp. 221 VEGETATIVE MARSH MANAGEMENT IN LOUISIANA: LONG-RANGE RECOMMENDATIONS Bill Good Coastal Vegetation and Wetland Restoration Program Louisiana Geological Survey Louisiana State University Baton Rouge, LA 70803 ABSTRACT The major objectives of vegetative marsh management are to prevent the conversion of marsh to open water and to control the erosion at marsh-water interfaces. Two key strategies for combatting the erosion of marshland, soil stabilization, and succession acceleration can be used to accomplish this. In many cases soil stabilization can be accomplished more cost-effectively with vegetative marsh management than with other methods. Succession acceleration can reduce erosion if an environment changes faster than natural plant succession can recolonize the area. A proposed procedure for selecting an optimal project design incorporates site evaluation data, the likelihood of project success, potential benefits, and project costs. The techniques, materials, designs, and goals of vegetative restoration in Louisiana are discussed. Also, a state-wide prioritization scheme is suggested that would locate vegetation projects in those areas with the highest rates of wetland loss. INTRODUCTION Although it is not applicable in all marsh loss situations, vegetative marsh management has been demonstrated to be effective in combatting interface erosion and the loss of marsh lands that result from environmental changes such as rising salinity levels. Vegetative marsh management often can be used where other management techniques are not feasible. The initial investment and maintenance are usually much less costly. Vegetative techniques are not complicated, but designing effective projects and setting priorities for their implementation requires that site conditions be scientifically evaluated and that costs, risks, and benefits be carefully weighed. A critical step in the development of an effective vegetative marsh management program is to determine where such techniques are cost-effective. We must have guidelines by which appropriate vegetative techniques can be selected for a given situation. In addition, we must use a decision- making process that will maximize benefits. This report discusses two proposed strategies for off- setting marsh loss-soil stabilization and succession acceleration; it describes some techniques and materials available; and it proposes a method for project design and prioritization of vegetative marsh management in Louisiana. STRATEGIES Soil Stabilization Erosion is used here to mean the removal of marsh by the physical influence of water. This process is a significant contributor to marsh loss along canals and bayous (Turner et al. 1982), the shores of lakes and bays (Adams et al. 1978), and the Gulf of Mexico (van Beek and Meyer- Arendt 1982). Marsh vegetation helps reduce erosion by absorbing wave energy and by providing 222 a subsurface root structure that helps to hold the soil in place. Vegetative marsh conservation measures have been shown to reduce erosion more cost-effectively than alternative methods (Table 1). The moderate to high wave-energy environments common to erosion-prone situations often limit the number of planting techniques available. Seeds are not practical because they can be washed away. Thus, transplant materials are required. In some areas a temporary wave-dampening structure may be necessary (Figure 1) to protect a stand of vegetation until it is sufficiently robust. At a certain threshold of increasing wave energy, vegetation may not be practical at all and permanent physical barriers may be required to alleviate erosion. Research is needed to determine the wave energy likely to be generated on water bodies with different sizes, shapes, depths, shoreline configurations, and boat traffic; and the effect various wave-dampening structures and plant species have on the wave energy (see Knutson et al. 1982). Succession Acceleration If an environment changes faster than the natural plant succession can recolonize the area with species adapted to the new conditions, valuable marsh land will be converted to open water. Potential marsh loss may be prevented by accelerating succession with the introduction of the appropriate species. For example, when increasing amounts of marine water enter brackish and intermediate marshes, the existing vegetation dies, leaving mud flats (Sasser et al. 1986). Tidal action removes the sediment from these areas, and they can deepen rapidly until they are too deep to support vegetation. It is important to prevent the final phase of this process because it is usually irreversible. Smooth cordgrass (Spartina alterniflora) may well be the best plant to stabilize these areas. Work under way by the author suggests that cordgrass may successfully colonize an organic substrate in a denuded brackish marsh. Succession acceleration can also be used in freshwater areas where higher water levels resulting from subsidence, impoundment, or other causes result in conditions unfavorable to existing flora. Often these conditions are also unfavorable to seed germination. In these instances, transplants of a species tolerant of fairly deep water, such as cutgrass (Zizaniopsis miliaceae), may speed up recolonization sufficiently to stabilize the site. Table 1. Comparative costs per 0 3 m of erosion control methods. Plants only $3.70a Plants through fiber mat $38.40a Plants behind floating-tire breakwater $46.90* Rock revetment $200.00-390.00b Fiberglass bulkhead $101.13c Creosote lumber bulkhead $113.31c "Allen et al. (1986) assume 20-m centers and 0.5-m spacing "Gray and Leiser 1982 CR.A.W. Corp. 1987 223 WAVE - DAMPENING FENCE h f*££ ^ . / ■ • / - 1 sjk TREATED 4X4 N^g^jgg ^1 TREATED 1X4 TRONT AND REAR SIDES WW < -f'"f ' v.. ./!, X Figure 1. Wave-dampening fence. 224 TECHNIQUES AND MATERIALS Plant Species The major objectives of vegetative marsh management are to offset the conversion of marsh to open water and to control the erosion at marsh-water interfaces. These efforts are directed primarily at the intertidal or water-saturated zone. Therefore, those plant species that can thrive under these conditions are the major candidates for wetland restoration efforts in Louisiana. Cutgrass has excellent potential in areas with fairly fresh water, and smooth cordgrass can be used where conditions are too saline for cutgrass. These two species are exceptionally well adapted to waterlogged conditions, and together will cover nearly the entire spectrum of salinity regimes in Louisiana (Louisiana Marshlands Plant Materials Laboratory 1986). Other plants suited for marsh work include Avicennia germinans, Panicwn hemitomon, Phragmites australis, and Spartina patens (Mendelssohn and Hester 1985a; Louisiana Marshlands Plant Materials Laboratory 1986). The author is conducting field evaluations of Scirpus calif omicus, Typha latifolia, and Eichhomia crassipes in canal bank erosion control in an intermediate marsh. Some species that have been tested for dune conditions are Panicum amarum, Uniola paniculata, Spartina patens, Sporobolus virginicus (Mendelssohn and Hester 1985a), and Paspalum vaginatum (Mendelssohn and Hester 1985b). Seeding Seeding methods need to be refined to better exploit the cost-effectiveness of seeding as compared to transplanting. The labor costs for seeding are drastically less than those for trans- planting, and large areas can be seeded in the length of time required to transplant a relatively small area. A commercial source of Louisiana wetland plant seeds and better seed handling and distribution techniques are urgently needed. Hydroseeding could be used in succession acceleration when an increase in the influence of marine water warrants the introduction of S. altemiflora because it fulfills two important requirements of seeding this species: it keeps the seeds moist and it embeds the seeds in the substrate. In addition, mulches, fertilizers, growth stimulants, fungicides, sticking agents, seeds of other species, etc. can be added to the slurry and thus tailor the seeding to the site and manage- ment objectives. The author conducted a preliminary hydroseeding experiment with S. altemiflora on a mud flat in a brackish marsh near Mud Lake in Cameron Parish, LA. Louisiana Erosion Control, Inc., of Port Allen, LA, provided a 1,300-gallon commercial hydroseeder for this purpose. The experimental area exhibited a 15% survival rate after 5 weeks in spite of one of the worst droughts in a decade. Preliminary arrangements for the testing of a scaled-down version of a hydroseeder (more practical for use under marsh conditions) are underway. Wave-Dampening Fences The design of wave-dampening devices (see Figure 1) needs extensive investigation. The structural requirements of the fences will vary according to the wave energy regime, the porosity of the fence material, tidal amplitude, and the mechanical properties of the supporting sediment. In addition, the wave energy behind the fence must be determined to predict the survival of plantings so protected. 225 Wave-dampening structures will improve plant survival rates if they reduce wave energies sufficiently. An additional benefit of wave-dampening fences is that suspended solids settle out if the wave velocity is decreased enough, as has been illustrated by a project conducted by Mike Windham of the Louisiana Department of Wildlife and Fisheries. This concept is also being explored by John Day and Raoul Baumans (Louisiana State University Center for Wetland Resources) in a study of marsh accretion resulting from brush fences. Exclosures The severe herbivore pressure to which transplant material is subjected greatly affects survival. To date, nutria (Myocaster coypus) have been observed to decimate unprotected bitter panicum (Panicum amarum) (Mendelssohn and Hester 1985b), smooth cordgrass, cutgrass (unpublished data of the author), and baldcypress (Taxodium distichum) (Louisiana Sea Grant 1987) plantings. Nutria are not the only pests, but because of their numbers they may be the worst. Exclosures have been used successfully (Figure 2) but this increases the cost per planting unit enormously. In certain areas, herbivore exclosures can double as wave-dampening fences and water hyacinth barriers (Figure 3). However, this must be approached with caution because nutria have been known to gnaw through plastic in order to feed on transplants (Louisiana Sea Grant 1987). Chemical herbivore repellents are another alternative, but their effectiveness in protecting transplants from nutria has not been documented to date. The author has conducted a herbivore exclosure transplant experiment using S. altemiflora in a highly organic marsh southeast of Cut Off, LA All unprotected plants were removed within 3 weeks, presumably by nutria. After 12 weeks, 85% of the protected plants had survived. These had vigorous growth and basal sprouts (unpubl. data). Water hyacinth (Eichhomia crassipes) can be an especially insidious problem for vegetative restoration efforts in freshwater areas. Large rafts of this species can enter an area where it was previously absent and wreak havoc on transplants. Typically, an extreme change in water levels causes mass movement of this plant over considerable distances; the plants can then be blown against a bank by prevailing winds. This process can cause mechanical damage and the removal of transplanted material. This can be avoided by placing a physical barrier such as a wave- dampening fence or poultry wire fence around the plantings. If fences are oriented parallel to the bank, it is important to attach a perpendicular skirt that prevents waterborne material from getting behind the fence (Figure 1). Alternatively, water hyacinth may prove to be a valuable species for erosion control when used to fill the space within fences to reduce wave energy. Field trials of this concept are planned by the author. PROJECT DESIGN AND PRIORITIZATION Desigft To determine the best design for a proposed project, the following procedure is recommended. 1) Use a planting decision tree similar to that shown in Figure 4, but tailored to Louisiana conditions, to determine appropriate techniques. 2) For each alternative, consult a site evaluation . form similar to that shown in Figure 5. Each technique would be assigned a likelihood of success. 3) Estimate the cost of implementing each alternative at the site in question. 4) Evaluate the site's value as a sustainable resource base. 5) Employ Bayesian statistical methods to find the approach that would maximize overall expected benefits. 226 Twenty-gauge, one-Inch mesh, galvanized poultry wire, measuring 36" square Heavy-gauge, half-inch, galvanized staples, (our per stake minimum Electro-plated hog-tie clips, four minimum Wolmanlzed, 0.4-retentlon. number -2 grade 1 * 2 stakes I PLAN SECTION Figure 2. Nutria exclosure. 227 Figure 3. Combined wave-dampening fence and herbivore exclusion around an erosion-control planting. 228 ELEVATION (MLW lo MTL) BEGIN ELEVATION (MTL lo MMW) TIDAL RANGE O3 0II) * TIDAL RANGE (O.OIl) SALINITY (<40%. ) SALINITY (>40%.) * rznn FETCH ( >IOml) * FETCH (6 1 lo IO.nl) FETCH (1.1 lo 5. Oml) n FETCH (0.0 lo 10.nl) SALINITY 020%.) [SEEDLINGS SALINITY « 20%.) ELEVATION (MLW lo MTL) ELEVATION (MTL TO MMW) |SEEDLINGS| [SPRIQS**| SEEDLINGS] ELEVATION (MMW to EIIT) * DO NOT PLANT ** LEAST-COST PLANTING METHOD SPRIGS | | SEEDS »*| Figure 4. Planting decision tree for Spartina aliemiflora, Atlantic and gulf coasts (redrawn from Knutson 1977). 229 1 SHORE CHARACTERISTICS 2 DESCRIPTIVE CATEGORIES ISCORE WEIGHTED RY PERCENTAGE SUCCESSFUL! 3 WEIGHTED SCORE A. AVERAGE FETCH Ikml LESS THAN 1.0 1.1 TO 3.0 3.1 TO 9.0 GREATER THAN 9.0 (87) (66) (44) (37) B. LONGEST FETCH Ikml LESS THAN 2.0 2.1 TO 6.0 6.1 TO 18.0 GREATER THAN 18.0 (89) I 67) (41) (17) C. SHORELINE GEOMETRY COVE :;.iHQM;!rrt!£ MEANDER OR STRAIGHT HE/ iDLAND §H0R (85) (62) (50) D. SEOIMENT GRAIN SIZE Imnl 0.0-0.4 0.4-0.8 0.8- 0R GREATER (84) (41) (18) 4. CUMULATIVE SCORE 5. SCORE INTERPRETATION a. CUMULATIVE SCORE 0-200 201-300 300- 0R GREATER b. SUCCESS RATE 15% 50% 100% Figure 5. Vegetative stabilization site evaluation form (redrawn from Knutson et al. 1981). These evaluation procedures are in the early stages of development. Figure 6 is a rudimentary decision key developed specifically for Louisiana conditions. This is only a preliminary sketch of what is needed but it does hint at the potential applications of such a procedure. To develop these tools, data from present planting projects must be collected, analyzed, synthesized, and documented. The factors affecting the survival of plant materials used in vegetative projects are not yet adequately understood. Some of the important parameters are fetch, angle of exposure, slope 230 characteristics, tidal amplitude, substrate characteristics, seasonal and climatic conditions, herbivore pressure, transplant species, plant vigor, plant size, age of the plant at the time of transplanting, and the stratification and distribution of the seeds. Soil texture, oxidation-reduction potential, the amounts of organic matter, phyto-toxins, and relative abundance of plant nutrients are also important to the successful establishment of a given species. Prioritization Given the magnitude of the marsh loss problem in Louisiana and the limited resources available, a defensible method of setting project priorities must be developed. A cost/benefit approach, when correctly applied, will maximize effectiveness. At the state-wide level, certain generalizations must be made, and exceptions must be anticipated because of the different values of particular sites and their varying suitability for vegetative projects. In general, however, vegetation projects should be located in areas with high rates of wetland loss because successful projects in these areas will yield the most annual marsh acres per unit of effort. A large portion of the State's coastal zone falls within the severe and very severe land- loss categories (Figure 7). (This map was based on changes that occurred between 1956 and 1978 and it is likely that loss patterns have changed considerably since then. A more current map should be used as soon as one becomes available, and the following priorities re-evaluated accordingly.) We should focus first on areas in the very severe category. Thus, the rapidly eroding marshes at 1) Cameron Parish east and west of Lake Calcasieu, 2) Cameron and Vermilion parishes south of White Lake, 3) eastern Terrebonne and southwestern LaFourche parishes, and 4) southern Plaquemines Parish should be the highest priorities for vegetative marsh conservation measures. These areas should be investigated in detail and all potential vegetative project sites evaluated using the procedure outlined above. CONCLUSIONS The future of vegetative marsh management in Louisiana will depend on how well the above questions are answered, and how promptly this knowledge is applied. Actual project specifications should incorporate input from landowners and involved governmental agencies, but must ultimately be based on a sound scientific evaluation of site conditions, the likelihood of success, potential benefits, and project costs. A thorough analysis of existing projects is essential to develop a more systematic and objective approach to site evaluation and project design than is currently available. Vegetative plantings and all other available marsh management techniques must be put to their best use if we are to remain the beneficiary of the many sustainable resources our wetlands provide. ACKNOWLEDGMENTS The cartographic, editorial, and word processing sections of the Louisiana Geological Survey are gratefully acknowledged for their invaluable assistance in the preparation of this manuscript. 231 1. SALINITY a) 3%o Spartina alterniflora b) 3%o (max) Zlzaniopsis miliacea 2. WAVE ENERGY a) very low transplants or seeds b) low unprotected transplants c) moderate wave-dampening devices and transplants d) high vegetative measures not feasible 3. NUTRIA POPULATION a) low no protection needed b) moderate to high physical enclosures or repellents needed 4. WATER HYACINTH a) not present in connecting water bodies. no protection b) present in connecting water bodies protection needed Figure 6. Rudimentary decision-making key for Louisiana marsh restoration projects. 232 •c/ml»/yr COASTAL ENVIRONMENTS, INC. tf**° Figure 7. Louisiana coastal zone land change rates 1955-78 (reprinted from van Beek and Meyer- Arendt 1982). LITERATURE CITED Adams, R.D., P. Banas, R.H. Bauman, H.H. Blackmon, and W.G. Mclntire. 1978. Shoreline erosion in coastal Louisiana: inventory and assessment. Coastal Resources Program, Louisiana Department of Transportation and Development. Baton Rouge. 139 pp. Allen, H.H., S.O. Shirley, and J.W. Webb. 1986. Vegetative stabilization of dredged material in moderate to high wave-energy environments for created wetlands. Pages 19-35 in F.J. Webb, Jr., ed. Proceedings of the Thirteenth Annual Conference on Wetlands Restoration and Creation. Hillsborough Community College, Tampa, FL. Knutson, P.L. 1977. Designing for bank erosion control with vegetation. Pages 716-733 in Coastal Sediments 77, Proceedings of the American Society of Civil Engineers. American Society of Civil Engineers, New York. 233 Knutson, P.L., J.C. Ford, M.R. Inskeep, and J. Oyler. 1981. National survey of planted salt marshes (vegetative stabilization and wave stress). Wetlands 1:129-157. Knutson, P.L., R.A Brochu, W.N. Seeling, and M.R. Inskeep. 1982. Wave damping in Spartina alterniflora marshes. Wetlands 2:87-104. Louisiana Marshlands Plant Materials Laboratory. 1986. Technical Report. LaFourche- Terrebonne Soil and Water Conservation District and the USDA Soil Conservation Service. 28 pp. Louisiana Sea Grant. 1987. The imported plague. Pages 1-5 in E. Coleman, ed. Aquanotes 16(4). Louisiana State University, Baton Rouge. Mendelssohn, LA., and M.W. Hester. 1985a. Isles Dernieres and Cheniere Ronquille stabilization project: soil-plant survey and test plantings. Report prepared for the Coastal Protection Section, Louisiana Geological Survey. Louisiana Department of Natural Resources, Baton Rouge. 154 pp. Mendelssohn, LA, and M.W. Hester. 1985b. 1984 Annual Report: Texaco USA coastal vegetation project, Timbalier Island. Texaco USA New Orleans, LA 128 pp. R.AW. Corporation. 1987. Cost comparison. R.AW. Corp. Company Brochure, Lafayette, LA Sasser, C.E., M.D. Dozier, J.G. Gosselink, and J.M. Hill. 1986. Spatial and temporal changes in Louisiana's Barataria Basin marshes, 1945-80. Environ. Manage. 10:671-680. Turner, R.E., R. Costanza, and W. Scaife. 1982. Canals and wetland erosion rates in coastal Louisiana. Pages 73-84 in D. Boesch, ed. Proceedings of the Conference on Coastal Erosion and Wetland Modification in Louisiana: Causes, Consequences, and Options. U.S. Fish Wildl. Serv. FWS/OBS-82/59. Van Beek, J.L., and K.J. Meyer-Arendt. 1982. Louisiana's eroding coastline: Recommendations for protection. Report prepared for the Coastal Management Section, Louisiana Department of Natural Resources. Baton Rouge. 49 pp. 234 INTRODUCTION OF SMOOTH CORDGRASS ON A NEW SITE Faye A. Talbot USDA Soil Conservation Service 555 Goodhope Street Norco, LA 70079 Allan Ensminger Wetlands and Wildlife Management Company P.O. Box 158 Belle Chasse, LA 70037 ABSTRACT A revegetation project was located in the interior of a historically fresh marsh in southeastern Louisiana. The plant introduced to the area was smooth cordgrass (Spartina alterniflora), a typical saltwater marsh plant with no prior recorded occurrence in the area. Other salt tolerant species such as marshhay cordgrass (Spartina patens) had entered the area through natural plant succession, and since its introduction, smooth cordgrass is following this trend. Ample sites are available for smooth cordgrass to occupy. Nucleus stands of suitable vegetation to be used for planting are extremely important to the landowner to reduce the expense of obtaining and transporting plant material great distances. Natural expansion of a planted community is the goal of this revegetation program and demonstrates the success of the effort. INTRODUCTION This study of smooth cordgrass (Spartina alterniflora) was made in St. Charles Parish which lies in southeast Louisiana between Jefferson and St. John the Baptist Parishes, approximately 48 km up river from New Orleans. The area is typical of the Mississippi River Delta in that the land slopes away from the alluvial ridge of the river to adjacent back swamp and marsh areas. The study area is bounded on the north by Lake Pontchartrain, on the south by U.S. Highway 61, on the east by the Jefferson Parish line, and on the west by Bayou LaBranche. Minimum elevations at or slightly below mean sea level are found in the marsh areas adjacent to Lake Pontchartrain. Normal ground elevation in the marsh averages 0.15 m to 0.21 m above sea level (St. Charles Lakefront Levee 1969; Ensminger and Savant 1986). Borings near Lake Pontchartrain done by the U.S. Army Corps of Engineers in 1969 and the Department of Transportation and Development in 1986 show the subsurface soil in this area consists of Recent deposits varying in thickness from about 15.25 m to over 30.50 m underlain with sediments of Prairie formation age. Generally the Recent consists of a surface layer, 3.66 to 6.10 m thick, consisting of very soft marsh clays with peat and organic matter, and moisture content of about 360%. This soil is classified by the Soil Conservation Service as a Lafitte muck, a highly erosive, deep, organic soil. This area was chosen to introduce smooth cordgrass because of it deteriorates with increased salinity, water depth, and tidal fluctuation. Personal communication with local land users and 235 interpretation of old aerial photographs indicate that freshwater from Bayou LaBranche buffered brackish tidal surge in the northwestern edge of the study area; vegetation which is characteristic of fresh to intermediate marshes resulted. This would explain why this marsh was so vulnerable to saltwater intrusion after dredging of the Interstate Highway 10 canal in the mid-1960's. Conversely, marsh vegetation in areas further east was predominately brackish plants and much less damage resulted from the construction of Interstate Highway 10. Other natural and artificial events compounded the problems in these wetlands. The Mississippi River Gulf Outlet Project which was completed in 1963 increased salinity levels in Lake Pontchartrain threefold (Montz 1973). This project also increased daily tidal ranges, thereby accelerating erosion. Hurricanes Betsy (1965) and Camille (1969) flooded the marsh and swamp with 0.61 to 1.83 m of saline water. Oil and gas activities induced brackish water into the cypress swamps resulting in a reduction of stand density and quality of trees. Since 1953, 1,190 ha of the 1,868 ha fresh marsh have become open water. Shoreline erosion along Lake Pontchartrain is jeopardizing the brackish ponds and remaining marsh vegetation. A 914-m section of shoreline extending from the Pipeline Canal west ranges in width from 1.5 m to 30.5 m. Shoreline retreat in this area has been over 7.6 m per year since 1971. The shoreline protecting the area east of the pipeline has experienced slower erosion rates of 5.18 m per year because the abandoned U.S. Highway 51 buffered most of the wave energy for many years. However, most of the highway bed has now eroded away, and shoreline retreat will likely accelerate. In response to all of these problems, planting of smooth cordgrass was initiated. Smooth cordgrass is fairly fast growing, reproduces by seeds and tillers, has shown success in shoreline stabilization, is very salt tolerant, and responds well to tidal fluctuations. No evidence of smooth cordgrass was documented in the study area after initial evaluation of 43 sites. The nearest natural occurrence of this plant is approximately 45 km away in the extreme eastern portion of Orleans Parish and along the north shoreline of Lake Pontchartrain in St Tammany Parish. Structural methods have also been initiated in the area to aid in shoreline erosion control and water stabilization. METHODS Twelve plantings of smooth cordgrass were made on 2 May 1984, on Lake Pontchartrain in St Charles Parish (Table 1). Plant materials were vegetative sprouts grown in styroblock tubes at the Soil Conservation Service Coffeeville Plant Materials Center. The plants were from accession No. MS-5121. Each row had about 40 plants. Plants were about 25.40 cm tall and had a good root mat to the 10.16-cm depth of the tube. Planting sites 1 through 8 were along a cut in the lake bank and are protected from direct wave action. An old bulkhead is about 30.5 m out in the lake from this site. Soils at this site are organic overlaid with sand (in some cases up to 7.6 cm deep). Sites 9 through 1 1 were planted along the edge of a shallow, open water area. This area is away from the lake shoreline, and the soils are organic. Planting site 12 was made on the lake shore directly opposite sites 9 through 11. 236 Table 1. Description of plantings on Lake Ponchartrain, St Charles Parish. Planting site Number number of rows Design 1 3 0.61 m in the row and 0.61 m between rows 2 2 0.61 m in the row and 0.61 m between rows 3 2 0.91 m in the row and 0.61 m between rows 4 1 0.61 m in the row 5 2 0.61 m in the row and 0.91 m between rows 6 2 0.91 m in the row and 0.91 m between rows 7 2 1.22 m in the row and 0.91 m between rows 8 2 0.91 m in the row and 0.91 m between rows (staggered) 9 1 0.61 m in the row 10 1 0.91 m in the row 11 1 1.22 m in the row 12 1 0.61 m in the row RESULTS AND DISCUSSION The initial plantings were followed up by two detailed evaluations of plant growth during the first growing season including photographic documentation. Surviving plants were doing well on an evaluation trip on 25 June 1984. Immediately after planting, nutria damaged sites 5 through 11, reducing survival rates on sites 5 through 8 to 30% and sites 9 through 11 to 50%. Nutria feeding activity within stands of smooth cordgrass is common even though the plant is not a preferred food plant of the animal. This activity results in many vegetative test sections being excavated and available for water transport to other suitable growing sites by tidal action. For best results, it would be desirable to precede planting by a vigorous trapping program to reduce the nutria population. The best results~75% survival rate-were obtained on plantings of two to three rows with 0.61 m spacings (sites 1, 2, and 3). The rhizomes were closing in between plants, and tillers were evident growing from the rhizomes. There was no additional nutria damage to sites 1 through 8 after the initial damage. The plants along the inside of shoreline (sites 9-11) were doing well. Although it was evident that there was a good survival rate, all exterior shoreline plantings (site 12) had been washed out by waves. The second field review on 23 August 1984 proved even more promising (Table 2). The results were put into three groups: Group 1, inside shoreline (non-fertilized), sites 9, 10, and 11; Group 2, interior marsh sites (fertilized and non-fertilized), sites 1, 2, 3, and 4; and Group 3, sites 5, 6, 7, and 8. Photographic documentation after 24 August 1984 showed continued growth and development of the planting sites and gradual spread into adjacent areas. The value of the vegetation in trapping detritus was evident. In May 1985, approximately 15.24 to 20.32 cm of detrital material had been deposited between the planting line at sites 1, 2, and 3 and the natural shoreline. As 237 Table 2. Observation on planting sites, 24 August 1984. Group Results Approximately 0.91 m tall, 0.46 m tillering spread, 5 to 10 stems from single stem plantings, nutria activity (some plants eaten; some plants that had been eaten had resprouted). Site 3 row plantings were totally closed in and were tillering in each direction, Site 2 row plantings were mostly closed in and were also tillering in each direction, and, Site 1 row plantings had spread out 0.61 to 0.91 m and fertilized plants showed a little more spreading. Similar response to Group 2 where plants survived nutria activity. tillers spread toward the shoreline, the detrital material was bound by the developing root system of the plant. This same sequence of events was noted in continued spread and development into the adjacent areas following the major storm events. There were several major events attributing to the spread of the plant other than the plant's ability to spread. Three hurricanes-Danny in August 1985, Elena in September 1985, and Juan in October 1985-hastened the transport of seeds and vegetative material, followed by several hard freezes which increased the germination rate of the seeds. Extreme high and low tides, water circulation, normal winds, and breaches in the shoreline all helped to transport the plants to adjacent areas. CONCLUSION It is expected that smooth cordgrass will continue to grow and spread in this area with no additional planting; however, additional planting will hasten the spread of the plant. Success of the planting program has attracted the attention of researchers in the area, and extensive experimental planting and fencing has been undertaken. LITERATURE CITED Ensminger, A., and W. Savant. 1986. Marsh conservation plan developed for William Monteleon. Submitted to Louisiana Department of Natural Resources and U.S. Army Corps of Engineers. Montz, G.N. 1973. An ecological study of a baldcypress swamp in St. Charles Parish, Louisiana. Castanea 38:378-386. St. Charles Lakefront Levee. 1969. General design memorandum no. 2, supplement no. 6. U.S. Army Corps of Engineers, New Orleans, LA. 238 VEGETATIVE PROPAGATION OF GIANT CUTGRASS FOR FRESH MARSH EROSION CONTROL Jack R. Cutshall USDA Soil Conservation Service 3737 Government Street Alexandria, LA 71302 Robert Glennon USDA Soil Conservation Service Federal Square Station 228 Walnut Street, Room 820 Harrisburg, PA 17108-0985 Leo T. Biles USDA Soil Conservation Service P.O. Box 629 Thibodaux, LA 70301 ABSTRACT Giant cutgrass (Zkaniopsis miliacea) is being evaluated for revegetation potential in coastal fresh marshes. As seed matures on the giant cutgrass plant, the stolon (seed stalk) lodges and eventually lies down on the water. The nodes produce roots and leaves and the new plants anchor themselves in the soil. Fifty-one accessions were collected and established at the Louisiana Marshlands Plant Materials Laboratory at Golden Meadow, LA The nodes, rooted and unrooted, were cut and planted. Potentially 400 nodes per 3-m row on mineral soils and 200 nodes per 3-m row on organic soils can be produced. After 2 months, 80% of the rooted nodes survived and grew 0.6 m and 50% of the unrooted nodes survived and grew 0.3 m. INTRODUCTION Giant cutgrass (Zkaniopsis miliacea) (Michx.) Doell and Aschers is a warm season, upright perennial grass. It reproduces vegetatively by stout creeping rhizomes and sexually by seed. The seedhead is an open panicle. Spikelets are one-flowered unisexual with both staminate and pistillate flowers occurring on the same panicle branch. The leaf blades are long, flat, and smooth, but have a scabrous (sawlike) margin from which it gets its common name. Giant cutgrass is typically 1-3 m tall. The leaf blades are 1-2 cm wide. It grows in moist soils throughout the Southeastern United States (Hitchcock 1950). Ecologically, giant cutgrass is found in relatively small amounts (s 25% of total plants) in climax fresh marshes of Louisiana. It is usually a sub-dominant plant associated with maidencane (Panicum hemitomen) or paille fine, as it is known in Louisiana. As water depth increases on fresh marsh sites, giant cutgrass will replace paille fine as the dominant plant. Water level fluctuations from the soil surface to 0.3 m above the soil surface are optimum for giant cutgrass. It can tolerate deeper water for short periods of time or when root-linked to plants growing in shallower water. Constant water depths of 0.3 m or more are detrimental to giant cutgrass growth, and it is soon replaced by bull tongue (Sagittaria falcata) as the dominant plant. 239 Giant cutgrass initiates growth in the spring. Lush vegetative growth is evident in early March with seed stalk emergence beginning by mid-April. Seed heads continue to be produced through September. As seed stalks are formed, they will lodge and become decumbent stems provided there is adequate open space around the parent plant These decumbent stems will initiate new growth at the nodes. Vegetative growth initiating from the nodes takes on the characteristics of a new plant being developed. Often the root system on this new growth is floating in water. The new plant will anchor itself if water levels are low, or fluctuating at or near the soil surface. It will also produce a seedhead, whether the new plant is rooted to the soil or floating. METHODS AND MATERIALS Giant citgrass can be vegetatively propagated by dividing clumps of plants and transplanting them. It can also be propagated by cuttings. Cuttings can be made when the seed stalk becomes decumbent. There should be two nodes per cutting. These cuttings are then put in potting soil with one node below the surface of the potting medium and the other above the surface. The pot used to propagate cuttings should be at least 15.3 cm wide and 20.4 cm deep. This gives adequate room for root development. Potting medium is maintained in a moist condition. Bottom watering of the pot, saturated to a 5.1 cm height, provides constant moisture in the lower portion of the pot and allows the surface to have adequate air space for plant growth. Field trials to ascertain planting methodology for giant cutgrass have been conducted on several sites: a saturated Kenner muck soil, a Kenner muck soil with fluctuating water levels, and at the Louisiana Marshlands Plant Materials Laboratory at Golden Meadow, LA, both an organic (Allemands muck) soil and a mineral (Sharkey clay) soil. Plantings were made using pieces dug from mature stands of giant cutgrass and from potted cuttings. Pieces from existing stands were divided and one or two main stems were planted at or slightly lower than the elevation they had originally grown. Plantings using pieces from cuttings were also divided into one or two main stems. These plantings were planted at or slightly above the elevation at which they had originally grown. One trial involved making two floats, each consisting of 4-6 stems of common reed (Phragmites australis) banded together. The two floats were banded together and three small clumps of giant cutgrass, spaced about 0.3 m apart, were placed between them. Nylon pull-through fasteners were used as bands. RESULTS AND DISCUSSION Potential sites for vegetatively establishing giant cutgrass need to be selected carefully. While giant cutgrass can grow in soils that are at or near the saturation point, there is a high mortality for transplants. Transplants must have adequate air space in the upper reaches of the root zone in order to become established. Sites with native transplants on saturated soils had no survival. Native transplants on soils with fluctuating water levels had about 50% survival. Cuttings had about 50% survival. The poor survival on sites with water over the soil surface or those with constantly saturated soils is attributed to the inability of newly planted plants to conduct the carbon dioxide-oxygen gas exchange in the root zone. The amount of available oxygen in the root zone may indirectly reduce photosynthesis by reducing the movement of water and minerals into the roots and on the leaves (Ferry and Ward 1959). Some plants have the ability to conduct this exchange through the leaves 240 or other plant parts. Giant cutgrass appears to require fluctuating water or to be root-linked to plants that have fluctuating water which exposes the soil surface to air. Cuttings with rooted nodes potted at the Louisiana Marshlands Plant Materials Laboratory had 80% survival and grew 0.6 m in height after two months. Unrooted nodes had 50% survival and grew 0.3 m in height. Fifty-one collections of giant cutgrass were taken from Georgia, Texas, and Louisiana. These were established in ten-plant rod rows at the Louisiana Marshlands Plant Materials Laboratory. Observations conducted during the last two years (1986 and 1987) show that the mineral soils have a potential to produce up to 400 nodes per 3-m row and up to 200 nodes per 3-m row on organic soils. Thus, materials available for vegetative propagation can be readily grown in relatively small impoundments. CONCLUSIONS Vegetative propagation of giant cutgrass has a potential for combating coastal erosion on fresh marsh sites in Louisiana. Site selection for plantings is critical. Those sites with fluctuating water levels that leave the soil exposed to aeration have the best chance of stand establishment. Transplanting plants from rooted stolons is logistically better than transplanting clumps of plants. Stolons may be rooted in pots or nursery impoundments for future transplanting to selected sites. ACKNOWLEDGMENTS The authors wish to thank the Louisiana Land and Exploration Corporation, Continental Land and Fur Corporation, and Tenneco-LaTerre Corporation for their assistance in conducting plant material field trials. LITERATURE CITED Hitchcock, A.S. 1950. Manual of the grasses of the United States. USDA miscellaneous publication no. 200. U.S. Government Printing Office, Washington DC. 563 pp. Ferry, J.F., and H.S. Ward. 1959. Fundamentals of plant physiology. MacMillan Company, New York. 288 pp. 241 ONE COMPANY'S EXPERIENCES WITH WETLANDS CONSERVATION W. L. Berry, Director Environmental Affairs & Safety Gerald J. Voisin, Manager Houma District The Louisiana Land & Exploration Company P.O. Box 60350 New Orleans, LA 70160 ABSTRACT The Louisiana Land and Exploration Company's (LL&E) experiences with wetlands conservation are discussed in this paper. Wetlands conservation is used to describe these activities rather than the much maligned term "marsh management." Apparently, in the minds of many people marsh management has become synonymous with impoundment or doing some other perceived harm to the wetlands. LL&E recommends that the use of the term "marsh management" be dropped and replaced with "wetland conservation." The latter term is actually more descriptive of a landowner's goal in preserving his property. Since the 1920's LL&E has owned in fee simple some 600,000 acres of land in south Louisiana, mainly wetlands. Over 30 years ago, the company recognized the importance of the brackish and intermediate marshes. At that time it became apparent to LL&E that uncontrolled ebb and flow of tides through the many small streams, ditches, gullies, ponds, and lagoons within the marshes were causing increased erosion and saltwater intrusion and subsequent land loss. Studies were begun to determine how erosion could be retarded, if not stopped. The problem was discussed with many individuals familiar with the marshes and estuarine areas such as trappers and fishermen, and various conservation groups and government agencies. A program to preserve the wetlands evolved from these studies. In April 1954, LL&E constructed its first water control structure, weirs built across small streams and ditches. The primary purpose of weirs is to retard the quantity of waterflow (not the velocity) and to stabilize water levels in the marshes. The structures prevent total drainage of the marshes during excessively low tides, thereby effectively reducing erosion caused by fast runoff. Since the weirs are constructed below normal tide levels, the necessary flowing and mixing of saltwater and freshwater are retained and the estuarine nature of the area is preserved. In addition, water is maintained for water dependent species in the many shallow water ponds, lagoons, and potholes, even during extremely low tides. Areas protected by water control structures have become important nursery grounds for fish, shrimp, and other marine life, homes for many fur bearing and other animals, wintering areas for waterfowl, and sanctuaries for a great variety of other birds. Since 1954, the company has constructed over 400 water control structures on fee lands, totaling -almost five miles in length. All of the weirs installed by LL&E were designed and located in close coordination with the U.S. Department of Agriculture, Soil Conservation Service (SCS), and were based on recommendations made by SCS. The cost of the program, however, has been borne 242 entirely by LL&E. In addition to the millions of dollars in construction costs, over $1,000,000 is spent annually for maintenance of structures and related activities. The same or similar methods of wetland conservation used by LL&E have been adopted by the Louisiana Department of Wildlife and Fisheries and by several other large and small landowners. Also, LL&E has always been conscious of the need for users to take measures to preserve the State's wetlands. Accordingly, actions considered detrimental to the marshes are restricted in almost all contracts involving LL&E property. These include oil and gas leases, geophysical permits, canal and pipeline permits, and other activities. On LL&E lands, lessees have been required to construct hundreds of additional water control structures, dams, and bulkheads, and to take other actions to prevent undue erosion, drainage, flooding, or saltwater intrusion. Pipelines must be buried. Where they cross canals, ditches, and ponds, the burial depth is a minimum of 3 ft below the bottom of the waterways. Such restrictions predate current regulatory requirements by many years. The benefits of the LL&E program extend to fishermen, hunters, trappers, wildlife photographers, and others. Each year many thousands of recreational fishermen catch spotted weak fish, red drum, and other fin fish at or near the water control structures, and many more harvest shrimp with cast nets. Louisiana Land and Exploration has over 1,400 sites under lease for recreational hunting and fishing camps where families and their friends spend weekends, vacations, and other leisure time. Approximately 300 hunting leases (primarily waterfowl) provided hunting facilities for more than 6,500 hunters during the 1985-86 hunting season. Company employees regularly inspect the water control structures. Anglers and hunters frequently report damage to structures before the company's routine inspections reveal them. This is an indication that sportsmen recognize the value of the structures and are willing to cooperate in maintaining them. In recent years, LL&E's investigations have shown that the company's program has produced results beyond expectations. With improved conditions in the protected areas, they have become, in effect, nursery grounds for fish, shrimp, and other marine life and sanctuaries for waterfowl and fur bearing and other animals. Recognition of the value of this program was given by the Wildlife and Fisheries Commission of the State of Louisiana as early as October 1956, in its official publication, Louisiana Conservationist: "For instance, the Louisiana Land and Exploration Company, one of the largest marsh and land holders in the state, has recently set out upon an extensive marsh main- tenance program. The majority of this property lies within the marsh areas that are subject to rapid erosion, tide fluctuation and salt water intrusion. Actual land losses from erosion have been accurately measured and outlined on maps. Strategic points in tidal channels have been located for the placement of water control structures which are so designed as to stop erosion and adjust water levels and salinities in order to improve conditions for the three-cornered-grass growth. Suitable structures for both the prevention of erosion and proper control of tides have been experimented with and put into effect in a big way. Rules and regulations have been promulgated that are now made a part of the permits for any oil activity on the property. All canals and drilling sites must be incased within levees, if at all possible. Abandoned canals and dry-hole transportation canals must be dammed and maintained by their permittee. Areas that may be improved by canals and levees are studied and management devices made a part of the permit to be installed by the permittees." 243 Partial technical documentation of these results was given in the 1975 study conducted on company property, "Ecology and Management of Ducks in the Freshwater Marshes of Southeastern Louisiana" supervised by Dr. Robert H. Chabreck of the Louisiana State University School of Forestry and Wildlife Management. Three master of science theses (Hoar 1975; Carney 1977; Vaughn 1977) resulted from the study. Other studies have also supported the positive aspects of LL&E's wetland conservation projects (Chabreck and Hoffpauir 1962; Ensminger 1963; Chabreck 1967; Ensminger 1968; Spiller and Chabreck 1975; Larrick and Chabreck 1976; and Davidson and Chabreck 1983). The company is convinced that its efforts have contributed significantly to reducing wetland degradation. However, LL&E is constantly striving to improve the program to lessen losses or impacts, whether natural or artificial. With this in mind, LL&E consulted with and sought the assistance of the U.S. Soil Conservation Service (SCS). Louisiana Land and Exploration and SCS entered into an agreement whereby SCS would conduct studies of existing conditions and devise methods that would retard saltwater intrusion into the less saline areas, lessen erosion and land loss, and improve vegetation and habitat in general. Priorities are established to concentrate efforts where needs are greatest. For example, if SCS determines that erosion is the major problem, then erosion control receives top priority. With this approach, LL&E's current and future wetland conservation programs will be well planned and coordinated. As a result of this cooperative effort, three marsh management units containing approximately 20,000 acres have been permitted for intensive management programs. Another unit containing about 4,000 acres is in the permitting process. A number of additional marsh management plans have been completed and are ready to be permitted. In line with the above recommendation, these should now be called "wetland conservation plans." Also, the company believes wetland conservation to be much broader than what is normally thought of as marsh management. Louisiana Land and Exploration has, through the years, participated in numerous wetland conservation activities. Included is cooperation with various universities and government agencies and organizations in a broad spectrum of projects including financial support of research programs, and the donation of time, labor, equipment and the use of land on which to conduct studies and programs to survey wildlife. Sometimes the company has even helped move animals to areas with depleted stocks. Other recent examples of what LL&E has done follow. The company worked with the Louisiana Department of Wildlife and Fisheries to establish a brown pelican rookery on company property at Isles Derniere. The Louisiana State University Center for Wetland Resources has conducted and is continuing to conduct studies at sites on LL&E property. At the East Golden Meadow Management Area, land has been made available to the SCS on which to conduct plant experiments. In conjunction with the Louisiana Department of Natural Resources and other agencies, SCS is focusing on developing superior erosion control plants and cultural treatments and techniques for the conservation of Louisiana marshes. Once plants are developed in the lab, they will be field tested in actual marsh conditions, and existing unvegetated areas will be replanted. The test site will be expanded in the near future to include additional acreage. 244 In May of this year, again working with the SCS, over 700 black mangrove trees were planted on Timbalier Island to replace those killed in recent years by hard freezes and Hurricane Juan. The trees were cultivated at the East Meadow experiment station. As one final example, LL&E has recently joined with the Louisiana Litter Control and Regulatory Commission in the "Adopt-A-Beach" program. The company adopted the eastern portion of Timbalier Island. Initial cleanup was conducted on May 18. About 100 dump truck loads of large debris, mainly driftwood, and 170 garbage bags of smaller items were removed. Other companies, organizations, and individuals are encouraged to "Adopt-A-Beach"; it is an excellent program. Louisiana Land and Exploration has also conducted many in-house projects to better use the resources of the wetlands. One prime example is a model alligator farm near Galliano, LA. This project was established with the hope that it will assist in developing the State alligator industry. Further, it should form the nucleus for a new industry-use of nutria meat, currently a much wasted resource-as food for alligators. The small farm is also capable of producing alligators to restock areas of low population or areas devastated by natural disasters. The above synopsis of LL&E's wetland conservation accomplishments is given to make three points: first, to illustrate that the company does care about the wetlands and associated problems- -particularly land loss; second, for years LL&E has actively worked to solve these problems; and third, we believe our efforts have yielded positive results and this view is supported by scientific studies. However, the company is completely frustrated by the current regulatory scheme which seems to thwart rather than encourage wetland conservation. At the core of the problem is the complex dual permitting system for activities in the wetlands. Under the current dual State and Federal permitting systems for activities in the coastal zone, different commenting agencies, on both the State and Federal levels, provide input on all permit applications. In many instances, these views conflict because of the different interests of the different agencies. As a result, LL&E found it extremely time consuming, difficult and in some instance impossible to pursue wetland conservation projects under the dual permit scheme. In fact, the company has even rejected permits because the proposed terms are so different from those applied for that the intended goals could not be achieved. Who suffers the most? The wetlands. As most people are aware, Louisiana loses about 1 acre of wetlands every 15 minutes, the time it takes to read this paper. The situation is even more frustrating in attempting to permit marsh management plans. As mentioned earlier, the company has a number of these plans completed and ready to be permitted. However, permitting is not being actively pursued. Why? First, LL&E believes that under the existing political and regulatory climate, it would be virtually impossible to obtain permits. Therefore, why waste time, money, and energy? Second, the company is aware of the complex monitoring programs recently proposed as permit conditions for other companies' marsh management plans. Louisiana Land and Exploration simply cannot afford to conduct the costly sampling and analysis programs that will be standard requirements in the future. Again, who suffers the most? The wetlands. There are some measures, however, that LL&E believes could be taken to rectify these problems: 1. Eliminate dual State and Federal permits. 2. Streamline the permitting process. 245 3. Whichever level, State or Federal, ends up with the permitting functions, it should use one umbrella agency to administer a comprehensive wetlands program. It should be stressed that such an umbrella agency should not just be another competing group added to the system. 4. Other recommendations are: A) Marsh management or wetland conservation plan permits should be issued for a term of five years for new construction with an additional five years for maintenance. B) Monitoring requirements under a marsh management plan should be limited to annual field reviews conducted by the SCS of those areas where work authorized by a plan has actually been performed. Finally, it is suggested that tax incentives be given to landowners to encourage initiation of preventive maintenance programs and to maintain programs already in place. Related research projects should receive similar support. Louisiana Land and Exploration is confident that these recommendations will help all of us, collectively, to achieve the goal of preserving our remaining precious wetland heritage. LITERATURE CITED Carney, D.F. 1977. An evaluation of waterfowl habitat improvement practices in a southeastern Louisiana freshwater marsh. M.S. Thesis. Louisiana State University, Baton Rouge. Chabreck, R.H. 1967. Weirs, plugs, and artificial potholes for the management of wildlife in coastal marshes. Marsh Estuary Manage. Symp. 28 pp. Chabreck, R.H., and CM. Hoffpauir. 1962. The use of weirs in coastal marsh management in Louisiana. Proc. Annu. Conf. Southeast. Assoc. Game Fish Comm. 16:103-112. Davidson, R.B., and R.H. Chabreck. 1983. Fish, wildlife, and recreational values of brackish marsh impoundments. Pages 89-114 in R.J. Varnell, ed. Proceedings of the Water Quality and Wetlands Management Conference, New Orleans. Ensminger, AB. 1963. Construction of levees for impoundments in Louisiana marshes. Proc. Annu. Conf. Southeast. Assoc. Game Fish Comm. 17:440-446. Ensminger, AB. 1968. Innovations in tidal and marshland wildlife management La. Wildl. Manage. La. Wildl. Fish. Comm., New Orleans. 12 pp. Hoar, R.J. 1975. The influence of weirs on soil and water characteristics in the coastal marshlands of southeastern Louisiana. M.S. Thesis. Louisiana State University, Baton Rouge. Larrick, W.D., Jr., and R.H. Chabreck. 1976. Effects of weirs on aquatic vegetation along the Louisiana coast. Proc. Annu. Conf. Southeast. Assoc. Game Fish Comm. 30:581-589. Spiller, S.F., and R.H. Chabreck. 1975. Wildlife populations in coastal marshes influenced by weirs. Proc. Annu. Conf. Southeast. Assoc. Game Fish Comm. 29:518-525. Vaughn, J.A 1977. An examination of the contents of duck gizzards from Carrin Crow Bayou, Terrebonne Parish, Louisiana, during the 1975 and 1976 hunting seasons. M.S. Thesis. Louisiana State University, Baton Rouge. 246 ECOLOGICAL CHARACTERIZATION OF JEAN LAFITTE NATIONAL HISTORICAL PARK, LOUISIANA: BASIS FOR A MANAGEMENT PLAN Nancy C. Taylor and John W. Day, Jr. Coastal Ecology Institute Center for Wetland Resources Louisiana State University Baton Rouge, LA 70803 and George E. Neusaenger Jean Lafitte National Historical Park 423 Canal St. New Orleans, LA 70130 ABSTRACT A management plan for Jean Lafitte National Park based on surface hydrology, salinity regime, soil characteristics, and historical changes in vegetative community patterns is presented. Results indicate that portions of the interior part of the park and areas affected by spoil banks are converting to a floating ecosystem. The park has experienced both a sediment deficit and a slight salinity increase accompanied by encroachment of Spartina patens. Vegetative health and soil characteristics indicate that saltwater intrusion has not been a problem. Management strategies for the park include reestablishment of natural hydrology and enhancement of sediment input to the area. Suggested management actions for the park include a shoreline erosion control and revegetation experiment, breaching or elimination of spoil banks along some major waterways, introduction of resuspended lake sediments into floating marshes, rollover weirs, and freshwater and sediment diversions. Managed succession is proposed as a management tool for some coastal wetlands. The environmental data collected and synthesized from the study provide needed information for park management; however, management strategies should be carried out in phases so that monitoring and modification can be implemented if needed. INTRODUCTION This paper describes an active management plan for the Jean Lafitte National Park which was developed based on an ecological characterization. The area requires an active management approach because of the dynamic nature of the natural system and because it has been heavily influenced by human activity, especially the construction of canals for wetland reclamation for urban expansion, upland runoff of sewage effluent, and surface drainage. The plan was designed to achieve the National Park Service's goal to reestablish, insofar as possible, the natural environment as it existed before human interference. The objectives include preserving the original vegetation, productivity, and hydrology of the area and limiting the encroachment of nuisance or introduced species, such as Chinese tallow (Sapium sebiferum) and wax myrtle (Myrica cerifera). 247 To accomplish this, we developed an ecosystem-based management approach, founded on a sound data base and a conceptual framework which incorporated the principles of natural resource management. Despite the need for more pre-wetland management environmental data collection and analysis, Louisiana coastal management plans often lack a sufficient scientific baseline characterization of the area in question. Hence, information is needed to determine whether wetland management strategies actually achieve the goals for which they were designed. Much coastal wetland management in Louisiana has recently become synonymous with semi- impoundment (Templet and Meyer-Arendt 1988), and much of Louisiana's coastal wetlands are currently impounded or semi-impounded (Day et al. 1989) by water-control structures to slow land loss and increase productivity in managed areas. There is, however, a lack of evidence and much controversy about the effectiveness of such marsh management and there is evidence that impoundment of wetlands may in some cases be exacerbating the geologic problems currently associated with Louisiana's subsiding coastline (Day et al. 1989). Thus we attempted to develop an ecological characterization which would lead to an adequate data base for management as well as a monitoring plan to test management effectiveness. The specific objectives included (1) establishing wetland management units within the area based on local hydrology, natural biological and physical features, and previous studies, (2) conducting an intensive year-long environmental data collection program to characterize the surface hydrology, salinity patterns, sedimentation rates, soil characteristics, gross water movements, water budget, and emergent plant species distributions to determine if saltwater intrusion, sediment starvation, and altered hydrology are problems in the park, and (3) using the ecological characterization for the development of a management plan aimed at preventing continued wetland degradation. DESCRIPTION OF STUDY AREA The park is a 5,160 ha area located in the central Barataria Basin (Figure 1). Elevations in the park grade from greater than 1 m above sea level on a bottomland ridge to near sea level in fresh and intermediate marshes. The soils include highly organic Holocene soil series such as Allemand, Kenner, Lafitte, and Larose (Soil Conservation Service 1985). Vegetation includes various types of lowland deciduous hardwoods and cypress-tupelo communities (White et al. 1983). Young disturbed canal spoil banks support Salix nigra, Myrica cerifera, Iva frutescens, and Phragmites australis {communis), in addition to an introduced species, Sapium sebiferum. Older spoil banks (>50 years old) support species resembling those found on cheniers of coastal Louisiana (White et al. 1983). Common trees are Taxodium distichum, Celtis laevigata, Quercus virginiana, Liquidambar stryaciflua, Acer rubrum, Quercus nigra, and Salix nigra (White et al. 1983). The intermediate marsh is characterized by Spartina patens, Phragmites australis, and a mix of freshwater plants. The freshwater marsh is dominated by Sagittaria lancifolia, Panicum hemitonum, Polygonum punctatumn, and Altemanthera philoxeroides. Hydrology of the Area Rainfall, evapotranspiration, tides, and wind are the primary forcing functions responsible for the hydrologic patterns in central Barataria Basin freshwater swamps and marshes (Conner and Day 1987). The natural hydrology of the area included both overland flow from the natural levee through the forests and marshes into Lakes Salvadore and Cataouatche, and streamflow through Bayous des Families and Coquille. Prior to the completion of the artificial Mississippi River levee system, riverine sediments were deposited in the Barataria Basin by overbank flow and crevasse formation. At present, the major external sediment input to marsh and swamp areas is resuspended bay bottom sediments (Baumann et al. 1984). 248 Baratarla Basin | Highland lN>v^ Swamp fr$$$$g Fresh marsh |*.-H Intermediate marsh tMii.^ Salt marsh JaanLafltta National Park Figure 1. Location map of study site. 249 Waterflow through the park has been drastically transformed. A combination of agricultural, urban, industrial, and drainage activities have created an altered ecosystem dissected by modified bayous and dredged canals. Surplus water flows into channelized bayous or dredged canals and is diverted into open water. Canal systems short-circuit many of the natural water flows. Much runoff now bypasses wetlands within the park. When nutrient-laden waters enter water bodies directly, nutrient uptake and removal processes are insufficient to reduce nutrient loads, and eutrophication often results (Day et al. 1977, Craig and Day 1981). Spoilbanks retard water and material exchange and cause prolonged flooding and stagnation leading to decreased productivity and species changes (Conner and Day 1976; Hopkinson and Day 1980). Habitat Changes There were significant habitat changes in the park between 1956 and 1983 (Figures 2 and 3; Table 1; U.S. Fish and Wildlife Service 1983). In 1956, there were 2,385 ha of fresh marsh, 470 ha of bottomland hardwood forest, 614 ha of forested swamp, and 98 ha of forested and developed upland. The emergence of large stands of Myrica cerifera by 1983 indicates that park drainage patterns had been altered. A study by Michot (1984) showed that the scrub/shrub areas experienced the shallowest fall water levels (3.83 cm) reflecting either higher elevations or floating conditions. The conversion of 1,322 ha of fresh marsh to intermediate marsh and the emergence of a small number of inland open water areas probably resulted from subsidence and salinity increase. Floating Wetland Terminology Because much of the park is a floating wetland, it is important to define terminology referring to floating wetlands carefully. "Flotant" or "floating marsh" is a fresh marsh mat which oscillates freely with the water layer beneath it (O'Neil 1949). "Tremblant" is a floating brackish marsh (O'Neil 1949). "Quaking marsh" is a form of marsh intermediate between a stable marsh and floating marsh. A quaking marsh experiences some mat movement, yet because of vegetative connections with the substrate beneath it, does not oscillate freely with water levels. METHODS Establishment of Study Plots Sixteen study plots were established throughout the park in an effort to encompass the range of habitat conditions which exist (canal, firm marsh, floating marsh, swamp, and areas affected by spoil banks; site locations are in Figure 4). In establishing these plots, we used aerial imagery, Soil Conservation Service Conservation Treatment Units (CTU) (Figure 5), discussions with park representatives, and field observations. Sites 4, 5, 6, 10, and 15 were selected for studying the effect of the spoil banks on the inland marsh characteristics. Marsh and swamp hydrologic stations were placed 50 m inland to characterize typical habitat in the absence of spoil and habitat behind a continuation of spoil bank widths. All sites were monitored monthly for hydrology, salinity, and soil substrate characteristics. Sites 5, 6, 9, 12, 17, and 18 were also examined for sedimentation rates. Marsh Elevation and Marsh Water Depth Vertical movements of the marsh surface and water depth over the marsh were measured monthly. Between mid-May 1986 and early April 1987, wetland elevation and surface water depth 250 -5oiw*d Smmt m Bonomlaad Hudvocd - Spoil • Dcvttopcd Upland Figure 2. 1956 habitat map for Jean Lafitte National Park (from U.S. Fish and Wildlife Service map 1983). 251 Intermediate Man h Fresh Manh I SP°a Scrub/Shrub □ °PenWeier Forested Wellands H Urban Upland Bottom! an dHardvoods Figure 3. 1983 habitat map for Jean Lafltte National Park (from U.S. Fish and Wildlife Service map 19S3). 252 Table 1. Historical land use changes in Jean Lafitte National Park. Area Change Land Use 1956 ha 1983 ha Hectare Percent Change Fresh marsh 2,413 1,073 -1,340 -56% Intermediate marsh 0 1,109 + 1,109 + 100% Bottomland hardwood 476 441 -35 -7% Forested swamp 622 537 -85 -14% Scrub/shrub 0 120 + 120 + 100% Forested upland 11 94 +83 +750% Developed upland 88.6 54 -35 -40% Open water 94.7 280 + 185 + 195% were measured to the nearest centimeter on tide staffs secured in the clay layer beneath the marsh or swamp surface. If the marsh surface was dry, the water level was assumed to be at the marsh surface, and the marsh elevation was inferred by subtracting the water depth above the marsh from the reading on the tide staff. Since marsh elevations could not be leveled to a common datum, all marsh and water elevation changes are discussed in terms of yearly ranges about their relative means. Salinity Marsh and canal salinity readings were obtained monthly. Interstitial soil salinity was obtained at a depth of 15 cm below marsh surface, and when the marsh was flooded, surface water salinity was also measured. Monthly mean and maximum salinities in Bayou Barataria at Lafitte were obtained from U.S. Army Corps of Engineers data for 1956-80. Soil Characteristics Sedimentation was measured as accumulation over marker horizons established at 9 locations in 3 different environments: (1) streamside marsh or behind spoil banks, (2) inland marsh (both behind spoil banks and in areas without spoil about 50 m from the water edge), and (3) inland swamp. Marker horizons of feldspar chalk were established in June 1986 as described in Baumann (1980), Swenson (1982), and Baumann et al. (1984), and sediment accumulation was measured in August 1986. The marsh and swamp substrate was sampled for bulk density, percent organic matter, mineral content, and percent water. Details of procedures for all field methods and analytical and statistical analyses are described in Taylor (1988). RESULTS Soil Characteristics The soil results indicate that the sites near sources of mineral sediment generally experienced greater vertical accretion rates and had higher bulk densities, lower organic content, and lower water content than sites in the interior of the park or behind spoil banks. 253 Figure 4. Station locations in Jean Lafitte National Historical Park. 254 MILLAUDON CANAL Figure 5. Map of Jean Lafitte National Park showing proposed structure placement and Conservation Treatment Units (from SCS 1985). 255 Vertical Accretion Over Marker Horizons Vertical accretion results illustrated that (1) sediment accretion rates in the park were relatively low compared with apparent water level rise, (2) sites having free communication with natural waterways experienced significantly greater accumulation rates than sites behind spoil, and (3) streamside sites generally experienced greater sedimentation accumulation rates than inland sites (Table 2). Vertical accretion rates during the 9-month study ranged from 1.0 to 5.9 mm. The rates were extrapolated to 1.3 to 7.9 mm/yr. These accretion rates were lower than the average subsidence rates (1.0 cm) measured elsewhere in the Barataria Basin. Sites with open access to natural waterways (51, 9S, and 121) experienced significantly greater accretion rates than sites distant from a sediment source or behind spoil banks (5S, 6S, 61). Bulk Density, Organic Content, and Water Content Bulk density, water content, organic content, and mineral content are highly interrelated soil characteristics. Organic content (on a dry weight basis) determines the amount of water in a given volume of saturated soils (Rainey 1979) because highly organic materials are porous and hold large amounts of water when saturated (Boelter 1974). Analysis of the soil characteristics in Jean Lafitte National Park revealed the following conclusions: (1) bulk density values were generally low, ranging from 0.04 to 0.10 g/cm3 at 14 of the 17 sites, (2) soil water content throughout the park was high and fell in the range of 78%- 94% for all sites, and (3) organic content was high and ranged from 43.7%-87.1%. These low bulk densities, high water contents, and high organic content concentrations are consistent with values for fresh and intermediate marsh (Baumann 1980; Hatton et al. 1983; Swarzenski 1987). These soil characteristics are a result of peat soils composed almost entirely of living and dead plant material (Leet et al. 1982; Odum et al. 1984). Cluster analysis of the bulk density, organic content, and water content data revealed three distinct clusters: (1) a group with high bulk density, low organic content, and low percent water, characteristic of sites with open access to mineral sediments, (2) a group with low bulk density, high organic content, and high percent water, characteristic of floating marsh sites and inland sites affected by spoil, and (3) a group with intermediate bulk density, organic content, and percent water values, characteristic of interior, quaking marsh sites (Figure 6). There was 87% correlation between water content and bulk density. Table 2. Mean sediment accretion rates and significance for groups of stations with sediment sources (sites 51, 121, 9S), behind spoil (6S, 61, and 5S), or inland (sites 61 and 91). Note that groups are listed in order of decreasing accretion rates. Group Mean sediment accretion rate Significance8 Sediment source 5.42 mm/9 mo. A Inland 2.12 mm/9 mo. B Behind spoil 1.41 mm/9 mo. C aas determined by Tukey's Studentized Range with a =0.05; groups with different letters are significantly different. 256 100 -i 80 c a> c o o o c a at 60 - 40- Floating Interior Quaking Firm Non- Floating with Sediment Source 20 0.000 1 0.300 0.100 0.200 Bulk Density Figure 6. Cluster analysis of bulk density and percent organic for stations in Jean Lafitte National Park. V represents cluster means and ellipses represent two standard deviations around the means. Water and Marsh Level Changes Ranges of annual vertical water level changes revealed that (1) there were no significant differences in monthly water level ranges between canal sites and water over marsh sites, (2) canal sites had water level changes grouped at the upper end of the range of yearly water level changes, (3) marsh sites exhibited yearly water level changes with a range of 24-36 cm, (4) the lakeside station (site 5) and the impounded swamp (site 18) exhibited the lowest yearly water level ranges, 257 indicating hydrologic flow inhibition, and (5) sites along Pipeline canal (2, 13, 13C, 16) experienced water level changes in the upper ranges of water level changes. The range of water level fluctuation at marsh sites was 24 to 36 cm, while canal sites experienced water level changes of 45-67 cm. Since surface response to climatic and tidal factors was on the order of hours to days and we only measured water levels once a month, we could not detect any significant difference between canal and marsh surface water level changes. Swenson and Turner (1987) reported that partially impounded marsh sites in Louisiana were characterized by both longer flooding events and reduced water exchange both aboveground and belowground. Degree of Vertical Marsh Movement Vertical movement of the marsh revealed several interesting trends: (1) the lakeside station (site 5) experienced a range of vertical marsh movement (1.5 cm) that was an order of magnitude less than all other sites, (2) sites with open access to waterways (sites 2, 9, 12, 13, 7, and 1), regardless of exact location within the park, experienced vertical movement ranges clustered at the low end of the range, (3) most of the park experienced slight vertical movement through time (and could thus be called quaking marsh), (4) sites affected by spoil (sites 4, 5, and 10) and several swamp sites experienced the greatest ranges of vertical movement through time, (5) floating marsh (sites 10 and 15) and semi-impounded (site 17) and impounded swamps (site 18) were clustered at the high end of the vertical movement range, and (6) the "truest" floating marsh (site 10) experienced significantly more movement than all other sites (see Figure 7). These results suggest that ranges in vertical marsh and swamp movement through time may be a good indicator of vertical marsh stability or lack thereof. Salinity Seasonally adjusted monthly average salinity means in Bayou Barataria at Lafitte revealed an increase of 1.5 ppt for the record from 1956 to 1981 (Figure 8). Mean salinity increased from about 1.1 ppt to 2.6 ppt. The yearly increase, 0.06 ppt, was highly significant (p>F=0.0001). The model accounted for 13% of the total variation in data. Seasonally adjusted maximum salinity means in Bayou Barataria at Lafitte revealed an increase of 2.95 ppt/30 yr or 0.1 ppt/yr. There were no statistically significant differences between mean surface (1.7± 1.1 ppt) and subsurface park salinities (1.5 ±1.4 ppt). The data suggest that average salinities at Lafitte increased in the early 1960's, possibly because the Barataria waterway enlargement was completed during this period. Station Salinities Clustering of monthly station salinity results revealed three significant groups (p>F=0.0001): (1) a lakeside quaking marsh group (sites 1, 2, 4, 5, 7, 9, 13) with intermediate salinities which peaked during October or November, (2) floating marsh (sites 10 and 15) and swamp sites (12, 17, and 18) with fresh salinities during the year, and (3) canal sites (13C, 14, 16, 20) which experienced highly variable and erratic yearly salinity patterns (Figures 9 and 10). The extreme variability in salinity at the canal sites emphasized the fact that these areas show quick hydrologic responses to outside environmental factors such as tides and rains. Sites along Segnette Waterway (1,5,7,9, and 20) had mean salinities significantly greater than both the floating marsh (10 and 15) and swamp sites (12, 17, and 18). Water salinity at the swamp and floating marsh sites ranged between 0.3 and 2.2 ppt (mean = 1.11 ±0.54). These low station salinities appeared to be buffered from the salinity effects of outside environmental factors such as tides. In addition, the salinities of these sites were more heavily influenced by upland runoff than by tidal effects. 258 Water 240 230 220 210 200 { Oct 66 Dale Apr 86 Jul 86 a) Firm marsh (site 5) Feb 87 May 87 Apr 86 May 87 b) True Floating marsh (site 10) Water 80 70 60 50 40 30 20 K Apr 86 V/ r\ Jul 86 Oct 86 Dal* Feb 87 100 May 87 Apr 86 Jul 86 Feb 87 »*y 87 c) Impounded swamp (site 18) d) Quaking marsh (site 9) Figure 7. Monthly water and marsh level variation at selected stations in the park from April 1986 to May 1987 illustrating different degrees of floating. Water levels are denoted by a "*" and marsh levels are denoted by an V. Note that the two curves on the same plot are absolute to each other, and that the vertical scales between plots are different 259 M E A N S A L I N I T Y I N P P T 10i 8 0- Meansal = 1 .09 + 0.036 Xi - 0.79 sin X2 + 0.08 cos X2 X1 =12* (Year - 1 938) + Month X2 = (4* Arsin (1) 'Month)/ 12 if ' :!'.■;;> • ■ : !• I "4\ % i ?! '*! » ! : r'"f* ' *' "1 1 T'l-T TT TT T T T T T T T » ? 7 T I I1 I T 01JAN55 0UAN61 0 UAN67 T ■ T"T I "l""^ I I I I 01JAN73' ■ ■ ' i ' ■ ' ' 01JAN79 0 1 JAN85 DATE Figure 8. Long term monthly mean salinities at Bayou Barataria. 260 5 -i a. 03 en 3 - 0 I i ■ i ■ i ■ i ■ i ' I ' l ' I ' I ■ 1 ' 1 ' 1 .'■ MayJun Jul AugSep OctNovDecJan FebMarApr Intermediate Floating Canai Date Figure 9. Mean monthly salinities of freely floating marsh, intermediate marsh, and canal stations from April 1986 to May 1987, in Jean Lafitte National Park. 261 a) Mean salinity b) Minimum salinity c) Maximum salinity Figure 10. Isohaline maps of mean, minimum, and maximum salinities in Jean Lafitte National Park from May 1986 to April 1987. 262 DISCUSSION Environmental Conditions in the Park The results of the ecological study indicate the following trends: (1) there was a slight salinity increase over the past 30 years accompanied by an encroachment of more salt-tolerant plant species, (2) this encroachment of salt-tolerant species occurred without resulting in marsh breakup, (3) accretion rates were lower than regional subsidence, (4) sediment accretion rates were significantly lower in areas inland behind spoil compared with areas with access to direct sediment sources, (5) soil characteristics were the firmest and accretion rates were the highest along areas with access to mineral sediment sources compared to floating and inland locations, (6) the hydrology of the park has been drastically altered over time beginning in the 1700's, (7) some areas of the park were impounded and covered by approximately 0.6 m of water year-round, (8) most of the park is a quaking marsh, and (9) the park has been experiencing a sediment accretion deficit and is evolving into a floating marsh as a response to this deficit. Large areas of scrub-scrub have invaded the floating marsh. Each of these points will be addressed in the following sections. Effects of Saltwater Intrusion in Jean Lafitte National Park Over the past 30 years, mean salinity in Bayou Barataria at Lafitte increased by 1.2 ppt. This salinity increase is reflected in vegetation changes. The western (lakeside) portion of the park, which was characterized as fresh marsh in 1956 (U.S. Fish and Wildlife Service 1983), is now intermediate marsh, as indicated by soil salinity and vegetation dominated by Spartina patens. Saltwater intrusion does not seem to be a serious problem in the park for the following reasons: (1) significant wetland loss has not occurred, (2) vegetation composition is changing to reflect a successional adjustment to salinity changes in the area, (3) marsh soils with the highest bulk density, highest mineral content, and lowest water content occur in the areas where the increase in salinity has been highest, and (4) the healthiest and firmest marshes occur in the areas where salinity increase has been highest. Few open water areas have developed and the lakeside soil characteristics (where salinity is highest) have the highest bulk density, lowest organic content levels, highest mineral content levels, and highest accretion rates. In addition, the mean salinity tolerance ranges of the dominant vegetation (Myrica certifera, Sagittaria lancifolia, and Spartina patens) indicate that these species are occurring within tolerable salinity ranges, relative to the conditions that exist in the park. For example, while salinity levels in the western portion of the park usually fall below 3 ppt, laboratory studies show that Myrica certifera and Spartina patens do not experience stunted growth below 8 and 10 ppt, respectively (Odum et al. 1984; Williamson et al. 1984). Soil Characteristics Sediment input plays an essential role in maintaining both nutrient input and vertical accretion which allow wetlands in the Louisiana coastal zone to offset the current rate of apparent water level rise (AWLR). Results from this study indicate that vertical accretion in wetlands of the park are significantly less than the AWLR of 1.0 cm/yr. Vertical accretion rates and soil characteristics showed three important trends: (1) vertical accretion rates were highest near sediment sources (lakes and Millaudon Canal), (2) vertical accretion rates were significantly lower behind spoil banks, and (3) only sediment accretion sites near the lake had >60% mineral content. Thus, although vertical accretion rates in the park were low compared with the AWLR, the healthiest marshes with the highest accretion rates and best soil characteristics were close to new sediment sources. 263 Hydrology The hydrology of Jean Lafitte National Park has been drastically altered by the construction of canals through the wetlands during the past 280 years (Figure 11). Under natural conditions, water flowed across the wetlands, the rate depending on the freshwater runoff, tidal exchange, and winds. Currently, however, altered hydrology in the park includes (1) upland runoff which quickly flows into the canals and is shunted out of the park, (2) regional water level fluctuations, especially during frontal passages, which lead to both rapid water level changes and water flowing quickly into and out of the park, and (3) semi-impoundment of wetlands caused by spoil banks. Most upland runoff and tidal exchange are primarily shunted directly in canals, thereby influencing relatively small areas of wetlands in the park. For example, during flood tide, water collects at the intersection of Kenta and Pipeline Canals and quickly leaves the park during ebb tide. Semi- impoundment also causes relatively low net flows through the park. Overland sheet flow through the wetlands is minimal. In addition to the gross hydrologic flows which have been altered, spoil placement along the canals has impounded some areas of the park. The impounded cypress swamp, (site 18) was flooded by at least 0.6 m of water during the entire study because spoil placement altered the natural hydrologic gradient of flow from the swamp into the marshes. Impoundment of this swamp undoubtedly has led to altered nutrient export and lowered productivity and seeding regeneration (Conner et al. 1981). Brown and Lugo (1982) report that cypress tupelo communities show severely reduced growth and productivity if the mean depth of flooding exceeds 60 cm. The impounded site in the park is currently experiencing this critical water depth and thus may be experiencing stress. Altered hydrology such as channelization and impoundment can lead to both increased and decreased retention times of water in wetlands. The channels themselves may lead to more rapid drainage of some areas while spoil banks may retard drainage from other areas. For example, Swenson and Turner (1987) reported that partially impounded marsh sites in Louisiana were characterized by both longer flooding events and reduced water exchange both above and below ground. In addition, wetland ecosystems with altered hydrology, which include deeper water levels, longer retention times, and slow flushing rates, often have lower productivity and symptoms of stress. Conner et al. (1981) showed that a permanently flooded impounded swamp had fewer trees and those trees had lower basal areas, reduced recruitment, and lower productivity compared to a healthy control swamp. Prolonged periods of deep inundation often reduced vegetative productivity and regeneration. Floating marsh formation hypothesis Floating marshes are widespread in coastal Louisiana, yet the process of formation is uncertain. Two different theories have emerged: (1) Russell (1942) concluded that flotant resulted from the encroachment and expansion of emergent vascular aquatics into previously open water area, and (2) O'Neil (1949) proposed that floating marshes were formed by buoyant detachment of marsh from the subsiding soil substrate as a response to marsh flooding and an absence of mineral sediment. Swarzenski (1987) studied floating marshes in coastal Louisiana and determined that buoyant detachment was probably the most important mode of formation. Aerial imagery of the park indicates that 322 ha of wax myrtle stands emerged in the area during the past 30 years. Field observations, soil characteristics, and sediment accretion rates all suggest that this area has undergone an accelerated rate of flotant formation catalyzed by both a sediment 264 a) Historical flow pattern b) Current flow pattern Figure 11. Historical and present hydrologic flow patterns in Jean Lafitte National Park. The relative size of the arrows denotes the relative waterflow. 265 accretion deficit and spoil bank placement. Although no documentation exists for stable marsh in the park more than 30 years ago, Williamson et al. (1984) reported that fresh marsh north of Lake Salvador converted from stable marsh to flotant during the last three decades. The flotant formation characteristics in Jean Lafitte National Park are consistent with other observed flotant patterns: a sediment deficit, hydrologic alteration, prolonged flooding and mat detachment, and successional stages developing into shrub-scrub species. The following steps constitute our hypothesis for the development of floating marsh in Jean Lafitte National Park: (1) The park experiences a sediment accretion deficit and levees (spoil banks) inhibit sheet flow. Because local sedimentation is less than apparent water level rise, there is an increasing sediment accretion deficit, especially in the interior parts of the park distant from sediment sources. (2) Low bulk density substrate roots combined with anaerobic conditions and methane gas formation beneath cause the marsh mat to detach from the bottom and float (O'Neil 1949; Cypert 1972; Hogg and Wein 1988). (3) Sagittaria lancifolia succeeds to Panicum spp. which succeeds to Myrica cerifa in fresh areas. (4) Small salinity increases are accompanied by encroachment of Spartina patens. Jean Lafitte National Park is located in an interdistributary basin which, because of flood control levees, no longer receives direct sediments from the Mississippi River. Spoil banks and altered hydrology reduce input of resuspended sediments. The area is experiencing a sediment accretion deficit with respect to local apparent water level rise. Soil characteristics and field observations indicate that sites with little or no sediment input and hydrologic alterations have low bulk density, high organic content, and high water content, characteristics of floating marshes. Canal spoil banks in the park inhibit sheet flow and cause water to flood the marsh for longer periods of time. These conditions tend to accelerate the formation of a floating marsh. Prolonged flooding of fresh marsh results in anaerobic conditions which enhance methane gas formation beneath the vegetative mat. Upward gaseous pressure beneath the mat, in combination with the low bulk density of vegetation roots, causes the mat to detach from the bottom and float up like a cork (O'Neil 1949; Cypert 1972; Hogg and Wein 1988). After detachment from the solid substrate, the top of the vegetation mat floats a few centimeters above the water level and thus no longer floods. The floating mat oscillates freely up and down in phase with the water layer beneath it (Swarzenski 1987). Field observations of several wax myrtle stands in the central area of the park (stations 10 and 15) indicate that these sites are freely floating. The response of this system to the conditions discussed above has been to succeed to a floating wetland ecosystem. Hydrological alteration has led to the formation of floating marsh in several regions. In northern Wisconsin, floating bog formed behind a sand sill adjacent to the lake (R.P. Novitski, U.S. Geological Survey, Ithaca, NY 14850; pers. comm.). A Canadian floating Typha spp. marsh emerged in a diked freshwater impoundment (Hogg and Wein 1988). In Louisiana, Bahr et al. (1983) noted that 4,000 ha of scrub-shrub developed in the Barataria and Verret Basins since the 1950's as a result of human modifications to basin hydrology. Much of this newly emerged scrub- ,shrub in Louisiana is floating (R. Chabreck, School of Wildlife, Forestry, and Fisheries, Louisiana State University, Baton Rouge, LA 70803; pers. comm.). The emergence of the floating scrub- shrub in the park and areas of the Verret and Barataria Basins both occurred during the same time and under the same circumstances: post 1950's canal construction activities. 266 Management Implications of Saltwater Intrusion Saltwater intrusion has historically been identified as one of the principal causes of wetland loss, so controlling it--mostly with structures-has been one of the principal goals of wetland management in Louisiana. Yet considerable literature suggests that increased submergence and sediment deficits may be as important in causing vegetation diebacks in the coastal zone. Submergence results in poorer drainage and increased waterlogging of wetland soils (Day et al. 1987). The deleterious effects of waterlogging on plants has been amply reported in the literature. For example, responses of plant shoots to water logging may include reduced stem elongation, chlorosis, senescence, abscission of lower leaves, wilting, hypertrophy, epinasty, leaf curling, and a decline in relative growth rate (Drew 1983; Jackson and Drew 1984). Apparent water level rise leads to submergence and waterlogging stress. Williamson et al. (1984) determined that inundation, not salinity, was the principal cause of the decline of floating wax myrtle stands in the Lake Salvador management area. In addition, Mendelssohn and McKee (1988) reported that in a laboratory study, sudden submergence of 10 cm had a significant negative effect on the biomass productivity of salt, brackish, and fresh marsh species. Increased salinity had a negative effect on fresh and brackish marsh species, the extent of which was dependent on salinity level and duration and abruptness of the stress. Analysis of freshwater and brackish species tolerances to salinity and inundation reveals that many of these species have rather wide ranges of salinity tolerance and only limited inundation tolerances with respect to environmental conditions in the park. Future research is needed on the relative importance of submergence and salinity as the cause of vegetation die-offs in the coastal zone. Two alternate approaches could be used to deal with problems of salinity intrusion. The first approach is site specific where intrusion of saltwater to a specific area is limited by a combination of structural devices such as levees and weirs. There is evidence that this method has had limited success in the Louisiana coastal zone (Cowan et al. 1986). An alternate approach is basin wide management of freshwater resources and hydrology. The rate of saltwater input to the southern coastal region, via canals such as the Barataria Waterway, could be slowed by locks, gates, and canals closures. Long term effects of increased salinity (Figure 8) strongly suggest that the enlargement of the Barataria Bay waterway resulted in an abrupt increase in salinity in the mid- basin. In the upper basin, diversion of Mississippi River waters and management for retention of freshwater could be used to both increase sediment sources to wetland and buffer and dilute saltwater flow within the wetlands. Since most of the upper Barataria Basin is channelized, freshwater runoff through the coastal zone proceeds very quickly. Therefore the goals would be to slow both freshwater runoff and saltwater input to the wetlands. The rate of saltwater intrusion into a healthy fresh marsh is very important. If saltwater intrusion into a fresh area is rapid, sudden, and includes a significant salinity increase, then salinity can be a problem. But this is not the case in Jean Lafitte National Park; salinity increase has been slow enough that the plants and soils have been able to adapt to the changes. The Soil Conservation Service proposed a management plan for the park which advocated the use of plugs along all the oil slips intersecting the Segnette Waterway (Figure 3; SCS 1985). In light of the results of this study, which show small salinity increases and healthy robust vegetative communities where the salinity increase has occurred, it seems more important to practice management which enhances open access to the sediment sources derived from the lake and surrounding bayous and canals, than to deter waterflows with weirs and plugs at the current salinity levels. Plugs and weirs could lead to further waterlogging and more rapid flotant formation. It 267 is impossible to optimize both sediment input and salinity in the park. The implementation of the Davis Pond diversion and changes to restore natural hydrology will be very beneficial in dealing with any saltwater problems. Management Implications of Sediment Dynamics The importance of mineral sediment input for wetland health has been highlighted during the last two decades (DeLaune et al. 1978; Baumann 1980; Hatton et al. 1983; Baumann et al. 1984). Mineral sediment input increases wetland elevation, enhances primary productivity, and thus organic accretion in wetlands. Both of these accretionary processes are often necessary to offset inundation occurring in subsiding areas. Studies of sediment accretion in Barataria Basin wetlands show that this area is experiencing a sediment deficit (Baumann 1980; Hatton et al. 1983; Baumann et al. 1984). Jean Lafitte National Park is also experiencing a sediment deficit, especially in those inland ar^as and areas behind spoil banks. Thus, new sediment and mineral input must be enhanced in this area to encourage healthier vegetation and firmer substrate. Management of the park should include plans to enhance sediment input during frontal passages when southerly winds push water into the basin and water with high suspended sediments concentrations (often greater than 100 mg/L) floods marshes. These sediments settle and accrete in the marshes. Weirs in Pipeline and Tarpaper Canals would decrease the rapidity of the water exchanges and allow the sediments to settle within the canal and in the marshes. The proposed SCS management plan for the park included plug and weir placement along the Segnette Waterway, which would have resulted in semi-impoundment and sediment exclusion from the park. Based on results of this study, open access of park wetlands to both resuspended and diverted sediment sources is of high priority to the health and maintenance of the area. Management Implications of Altered Hydrology Disturbance of natural sheet flow through the wetlands and impoundment of cypress swamps are two of the major hydrologic alterations which have occurred in the park. Considerable research shows that impoundment as a management practice for cypress swamps results in lowered productivity and regeneration (Conner et al. 1981). The swamp in the park will disappear if management practices are not changed. Overland sheet flow from the bottomland hardwood forests to the cypress swamps and into fresh and intermediate marshes should be encouraged (Figure 11). Structures in pipelines and canals will moderate rapid water level fluctuations. Canal spoil banks that impound the cypress swamps and marshes should be breached and perhaps eliminated. Resilience and Management Implications of Floating Marshes There is relatively little information about floating marsh productivity and resilience in Louisiana. The productivity of floating Panicum marshes ranges from 1,700 g/m2/yr to 1,960 g/m2/yr (Sasser et al. 1981; Sasser and Gosselink 1984) as compared to 1,501-2,310 g/m2/yr for freshwater Saggitaria lancifolia marshes (Hopkinson et al. 1978). Secondary production of fish and other aquatic organisms is probably less in floating marshes than in stable marshes due to low 02, high CO-, and low pH below the mat (Howard-Williams and Gaudet 1985). Alligators, deer, and mammals do, however, use elevated floating marshes and wax myrtle stands as habitat. Determining whether floating marshes are ephemeral or resilient ecosystems within a management time frame is important for decisions concerning wetland management. In some cases, floating marshes have persisted for long periods. Sasser (Center for Wetland Resources, Louisiana 268 State University, Baton Rouge, LA 70803; pers. comm.) notes that floating marshes in Lake Boeuf have remained stable ecosystems for more than 46 years. Similarly, Hogg and Wein (1988) state that Canadian "floating Typha spp. mats develop to become very resilient systems and it appears doubtful that mat buoyancy and the current trend toward bog-like conditions will be disrupted, either by natural or anthropogenic perturbations at the mat surface." Conversely, several researchers reported that floating marshes may be ephemeral. Williamson et al. (1984) determined that as "floating wax myrtle stands increase in size, they develop tilt and add instability to an already tenuous system because the weight of the tree forces the surface roots under water causing the shrubs to slowly die." The question is, do these areas surrounding the dead Myrica cerifera stump convert to open water or fill in with herbaceous floating vegetation? Huffman and Leonard (unpubl.) reported that sinking floating mats are actually a successional phase to swamp forests with cypress. This is probably not the case in a subsiding environment such as coastal Louisiana. Management of these floating marshes, whether they are ephemeral or not, must take into account the long-term productivity and health of the environment. Within coastal wetlands, new mineral sediment and nutrient input lead to healthier vegetation and firmer substrate (Gosselink and Gosselink 1985; Kadlec 1987; Kadlec and Bevis 1987). Therefore, we suggest that resuspended and diverted sediment and nutrient sources be diverted into these floating areas to possibly convert them into stable marshes and to enhance their productivity. MANAGEMENT OF JEAN LAFITTE NATIONAL PARK In developing a management plan for the park, there should be three primary objectives: retardation of lakeside erosion, improved hydrology, and enhancement of sediment input to the area. If these three objectives are accomplished, there will be a number of beneficial effects, including enhanced vegetation health and productivity, more rapid soil formation, and stronger connections among different wetland habitats. Insofar as possible, improvement of hydrology of the area should reestablish overland flow which follows the east to west elevational gradient from the bottomland hardwoods to the cypress swamp, fresh marsh, intermediate marsh, and finally into the open water bodies. To facilitate overland flow through the park subbasins, canal spoil banks should be breached, lowered, or eliminated in some cases. The extreme fluctuation and dominance of the water flows into and out of Pipeline and Kenta canals should be moderated. The flow in natural channels (Bayous Boeuf, Des Families, and Coquille) should be encouraged where possible. The degree and speed of water level fluctuations within both the wetlands and the canals should be adjusted to what would occur naturally. Sediment input to the park should be increased by encouraging input and trapping of resuspended sediments from Lakes Salvador and Cataouatche and local canals (Millaudon and the Intercoastal Waterway). Resuspended sediments and nutrients from local canals and lakes would serve to partially offset the process of subsidence. But the only sediment diversion option which could truly overcome the subsidence problem occurring in the central Barataria Basin would be diversion of sediment-laden water from the Mississippi River. The implementation of the Davis Pond diversion will thus be beneficial to the park. Managed Succession The pattern of vegetation adjustment to gradually increasing salinity suggests that an important conceptual tool for the management of some Louisiana coastal wetlands may be the idea of managed succession. The objective of a number of management plans is to maintain fresh and intermediate marshes in areas which are converting to brackish marshes or open water. This is 269 done for preservation of a particular habitat type or for the preservation of any type of vegetated wetlands. Semi-impoundment may preserve a certain habitat type for a while, but as we discussed earlier, problems of waterlogging, sediment starvation, and poor drainage after tropical storms may make managed succession a viable alternative. By managed succession, we mean management actions employed to facilitate wetland succession which is already taking place while minimizing net wetland loss. In the park, for example, there has been a succession of fresh to intermediate and brackish marshes. Given the environmental setting of the park (gradual salinity increase and altered hydrology), we believe that actions can be taken to minimize wetland loss. These include a variety of actions (described above and in the next section) designed to improve hydrology and increase sediment input to the park. In general, we suggest that the ideas of managed succession be investigated more thoroughly to determine its utility in coastal Louisiana. Suggested Management Pilot Studies The results of this research and experiences in wetland management from other areas suggest that a coordinated management plan is necessary for the Jean Lafitte National Park. The plan includes a number of measures designed to reduce wetland erosion, restore a more natural hydrologic regime, increase sediment input to the park, and enhance productivity (Figure 12). The plan also identifies areas of further research necessary to address critical information needs. (1) Shoreline Protection Along Lake Salvador Lakeside erosion is one of the most critical problems facing the park. To arrest further erosion, some type of shore protection must be implemented. Shore protection as used by the Dutch in the Wadden Sea (Kams 1962; DeGlopper 1965; Boumans et al. 1987) could be coupled with wetland formation. (2) Small Scale Lakeside Flotant Conversion Experiment We suggest choosing a floating marsh site with potential access to lake suspended sediments (Figure 12). The objectives of this experiment are to determine the feasibility of increasing bulk density of soils of a floating marsh, increasing the overall health and productivity of the area, and, ultimately promoting the succession of floating marsh to stable marsh. The design of this pilot project is as follows. A break would be created in a spoil bank adjacent to an area of lakeside floating marsh to allow direct input of resuspended lake sediments to the marsh surface. A low level sill structure should be installed at the spoil break to ensure that the incoming lake water does not cut a crevasse and lead to erosion of the flotant. A wire mesh screen should be stretched across the break to insure that the mat does not float out of the area. Vegetation, soil characteristics, and accretion rates should be monitored every six months for several years to determine the success of the experiment and its practical application to other sites in the park. (3) Structural Suggestions Several structural measures are necessary to achieve the objectives of the management plan. These include breaching or eliminating some spoil banks along major waterways and installing some ' weirs. Rollover weirs would allow small boat access to the park while dampening water level fluctuations. A slotted weir could be used to allow the marshes and canals to draw down, but prevent rapid water level fluctuations. Slotted weirs would allow access to migratory marine organisms. Other possible weir types include rock weirs and flap-gated weirs. Rock weirs allow 270 Millauion C Management Suggestions H Suspended sediment experiment J Control effluent diversion [H] Diversion above mat surface I Diversion b el ov mat surface X Make breaks in levee spoil ^ Baffling vave barrier ^ Revegetation behind v»ve barrier Figure 12. Management suggestions for Jean Lafitte National Park. 271 water to flow around and through the rocks, but at a much slower rate. Flap gates allow more control of water movement. Structural alternatives should be carried out in phases so that monitoring and modification, if needed, can be implemented. We suggest that the spoil impounding the cypress swamp (site 18) be removed to promote flushing and draw downs by aiding regeneration and establishment of seedlings (Figure 12). Water levels and forest species composition and productivity should be monitored to determine the ecological consequences of this action. To both slow rapid water level fluctuations in the wetlands and encourage overbank flow, three water control structures should be installed: (1) in the Pipeline Canal, just north of its intersection with the Segnette Waterway; (2) just west of the intersection of Tarpaper and the perpendicular can^l flowing north of it; and (3) at the intersection of Kenta Canal and the Intercoastal Waterway. Placement of the structure in Pipeline Canal would slow the flow of water out of the park and enhance overland flow in both CTU 6 and 8, which currently show signs of hydrologic alteration. Overland flow through CTU 2, 4, and 6 would be encouraged by the structure placed in Tarpaper Canal. Removal of the spoil at the end of the northernmost oil cut on Segnette Waterway would enhance waterflow out into Segnette and into Lake Salvador. These alterations would encourage waterflow out of the park following both the natural wetland elevation gradient and the dampened canal courses. These structural changes would establish and promote four types of flow through the park (Figure 13): (1) upland runoff from the ridge into the park, (2) overland net flow through the interior CTU (3) enhanced exchange between the lake water and the wetlands, and (4) diminished water level fluctuations in the canals. (4) Freshwater and Sediment Diversions Freshwater and sediment diversions have been suggested as a means of nourishing wetlands (Gosselink and Gosselink 1985; Templet and Meyer-Arendt 1988; Conner and Day 1987). Wetlands act as buffers and filters for sediments and nutrients (Kennedy 1983; Howard- Williams 1985). Studies on effluent application to wetlands have shown that (1) long-term nutrient accumulation occurs in some cases (Dixon and Kadlec 1975; Gupta 1977), (2) increased organic matter and accumulation rates occur, and (3) that these nutrient and mineral sources are incorporated into long-lived plant and animal matter (Gaudet 1977; Dolan et al. 1981; Verhoeven et al. 1983; Howard-Williams 1985). Fresh marsh biomass increases significantly with nutrient input (Dolan et al. 1981; Verhoeven et al. 1983). There are three potential sources for freshwater and sediment diversion into the park: (1) resuspended sediments from Lake Salvador and local canals including the Intercoastal Waterway, (2) nutrient and sediment sources from Millaudon Canal, and (3) Mississippi River water. The first two sources would help offset the effects of subsidence and increase vegetation growth. Mineral sediment inputs increase wetland elevation, enhance primary productivity, and increase organic accretion in wetlands. Diversion into floating areas has never been attempted, and the consequences and methods are yet to be determined. For example, would sediment accretion and productivity changes be more substantial if sediment-laden waters were introduced above or below the floating mat? To answer this question, a three-part experiment is suggested. Water should be pumped or diverted into two separate regions~an area where water is introduced above the mat, and an area where the water is introduced below the mat. There should also be a control where no water is pumped at all. 272 Figure 13. Proposed water control structures and resulting generalized flow patterns. Note that relative size of arrows indicates relative discharge. 273 A diversion at Davis is scheduled to begin operation by 1992. This diversion is designed mainly for salinity management and will freshen the water in the park. It may also result in some sediment input to the park. The Algiers Lock can also be used to divert small amount of freshwater (on the order of 2,000 ft3/s) into the Barataria Basin during high flow. Since this diversion is via the Gulf Intracoastal Waterway some of the water and sediments could be used for the park. In the future, perhaps a small scale diversion could be implemented especially for the park area. ACKNOWLEDGMENTS We are indebted to Dr. James Gosselink and Dr. Flora Wang, Louisiana State University, David Mu!h and Kurt Schoenburger, National Park Service, and Tom Oswald, Center for Wetland Resources. This work was supported by the National Park Service, U.S. Department of the Interior, the Louisiana Sea Grant College Program, and the Department of Marine Sciences, Louisiana State University. LITERATURE CITED Bahr, L.M., Jr., R. Costanza, J.W. Day, S.E. Bayley, C. Neill, S.G. 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Uptake, accumulation, and loss of nutrients by papyrus in tropical swamps. Ecology 56:415-422. Gosselink, J.G, and L. Gosselink. 1985. The Mississippi River delta: a natural wastewater treatment system. Pages 327-337 in P.G. Godfrey, E.R. Keynor, S. Pelczarski, and J. Benforando, eds. Ecological considerations in wetlands treatment of municipal wastewaters. Van Nostrand Reinhold Company, New York. 473 pp. Gupta, P.K 1977. Simulation and maximization of wastewater inputs to a portion of the Porter Ranch Peatland. Pages 215-311 in R.H. Kadlec, D.L. Tilton, and J.A Kadlec, eds. Feasibility of utilization of wetland ecosystems for nutrient removal from secondary wastewater treatment plant effluent. University of Michigan, Ann Arbor. Hatton, R.S., R.D. DeLaune, and W.H. Patrick. 1983. Sedimentation, accretion, and subsidence in marshes of Barataria Basin, Louisiana. Limnol. Oceanogr. 28(3):494-502. Hogg, E.H., and R.W. Wein. 1988. 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Causes of wetland loss in the coastal central Gulf of Mexico. Vol. 2, Technical narrative. Minerals Management Service, New Orleans, LA Michot, T.C. 1984. A marsh vegetation study of Jean Lafitte National Historical Park. Division of Ecological Services, U.S. Fish and Wildlife Service, Lafayette, LA 25 pp. Odum, W.E., T.J. Smith III, J.K. Hoover, and C.C. Mclvor. 1984. The ecology of tidal freshwater marshes of the United States east coast: a community profile. U.S. Fish Wildl. Serv. FWS/OBS-83/17. 177 pp. O'Neil, T. 1949. The muskrat in the Louisiana coastal marshes. Louisiana Wildlife and Fisheries, New Orleans, LA Rainey, G.B. 1979. Factors affecting nutrient chemistry distribution in Louisiana coastal marshes. M.S. Thesis. Louisiana State University, Baton Rouge. 85 pp. Russell, R.J. 1942. Flotant. Geogr. Rev. 32:74-98. Sasser, C.E., G.W. Peterson, D.A Fuller, R.K. Abernathy, and J.G. Gosselink. 1981. Annual report for LOOP Inc. Louisiana State University, Baton Rouge. Sasser, C.E., and J.G. Gosselink. 1984. Vegetation and primary production in a floating freshwater marsh in Louisiana marsh in Louisiana. Aquat. Bot. 20:245-255. Soil Conservation Service, and Crescent Soil and Water Conservation District. 1985. District cooperative agreement with Jean Lafitte National Historical Park. Crescent Soil and Water Conservation District, Norco, LA 56 pp. Swarzenski, C. 1987. Floating marshes in Louisiana: substrate and hydrologic characterization. M.S. Thesis. Louisiana State University, Baton Rouge. 65 pp. Swenson, E.M. 1982. A report on the Catfish Lake, Louisiana, backfilling study. Coastal Ecology Institute, Center for Wetland Resources, Louisiana State University, Baton Rouge. 44 pp. Swenson, E.M., and R.E. Turner. 1987. Spoil banks: effects on a coastal marsh water level regime. Estuarine Coastal Shelf Sci. 24:599-609. Taylor, N.C. 1988. Ecological characterization of Jean Lafitte National Historical Park, Louisiana: basis for a management plan. M.S. Thesis. Louisiana State University, Baton Rouge. Templet, P.H., and KJ. Meyer-Arendt. 1988. Louisiana wetland loss: a regional water - management approach to the problem. Environ. Manage. 12(2):181-192. U.S. Fish and Wildlife Service. 1983. Wetland changes in Lafitte National Historical Park (1956- 83). U.S. Fish and Wildlife Service, Slidell, LA 1:24,000. 276 Verhoeven, J.T.A., S. van Beek, M. Dekker, and W. Storm. 1983. Nutrient dynamics in small mesotrophic fens surrounded by cultivated land. I. Productivity and nutrient uptake by the vegetation in relation to the flow of eutrophicated ground water. Oecologia 60:25-33. White, D.A-, S.P. Darwin, and L.B. Thein. 1983. Plants and plant communities of Jean Lafitte National Historical Park, Louisiana. Tulane Stud. Zool. Bot. 24:101-129. Williamson, G.B., N.G. Barker, and D.J. Longstreth. 1984. Death of wax myrtle along coastal Louisiana marshes. Board of Regents Research and Development Program, Louisiana State University, Baton Rouge. 85 pp. 277 RESULTS OF AN INTENSIVE MARSH MANAGEMENT PROGRAM AT LITTLE PECAN WILDLIFE MANAGEMENT AREA Thomas J. Hess, Jr. Louisiana Department of Wildlife and Fisheries Route 1, Box 19B Grand Chenier, LA 70643 Ronald F. Paille U.S. Fish and Wildlife Service P.O. Box 4305 Lafayette, LA 70502 Randal J. Moertle Golden Ranch Farm P.O. Box 18 Gheens, LA 70355 and Kenneth P. Guidry Route 6, Box 864 Natchitoches, LA 71457 ABSTRACT Little Pecan Wildlife Management Area, located in the lower Mermentau River Basin of Cameron Parish, LA, consists of 4,452 ha of privately owned property dominated by fresh, intermediate, and brackish marsh. Flap-gated, variable-crested water control structures were used to manage 10 semi-impoundments, 3 of which (1,539 ha) also had forced drainage capacity. Cross- sectional area of water control structures was 215% greater than that recommended by current U.S. Soil Conservation Service guidelines. Semi-impounded areas were managed (1975-87) using a multiple resource concept targeted at species of commercial and recreational importance including waterfowl, alligator, furbearers, freshwater finfish, and estuarine finfish and shellfish. Enhancement of wintering waterfowl habitat received top priority. Management techniques consisted primarily of late spring/early summer drawdowns, water level and salinity stabilization, introduction of brackish water, and maintenance of a deep tranasse system throughout each semi-impoundment. Drawdown management in semi-impoundments of fresh and intermediate marsh types encouraged the encroachment of jointgrass (Paspalum vaginatwn), giant cutgrass (Zizaniopsis miliaceae), and bullwhip (Scirpus califomicus) into shallow open water areas, resulting in a gain of vegetated emergent wetlands at the expense of shallow open water habitat. Data indicates that management practices increased furbearer harvest, increased waterfowl usage and harvest, and did not adversely affect alligator populations or harvest. Ingress and production of estuarine organisms were -permitted to the extent that increasing salinities did not adversely impact freshwater aquatic vegetation and freshwater finfish. Observations and intermittent sampling indicated that productivity of estuarine organisms within the semi-impounded marshes was relatively high. 278 INTRODUCTION Little Pecan Wildlife Management Area (LPWMA) is located in the lower Mermentau River basin of Cameron Parish, LA (see Figure 1). The area consists of 4,452 ha of chenier ridge, swamp, freshwater marsh, intermediate, and brackish marsh habitats. In 1975, this property was acquired by the late Mr. Herman Taylor, an avid waterfowl hunter. Taylor hired a staff of four biologists and began developing and implementing an intensive marsh management program (1975- 87). The marsh management plan at LPWMA was developed on the concept of multiple use of renewable natural resources. In order to finance the marsh management program, Taylor created an exclusive waterfowl hunting club, catering to and largely financed by large corporations. Goals and Objectives 1. Develop and maintain optimum wintering waterfowl habitat. 2. Increase wildlife and fisheries potential of the area. 3. Increase the surface value of the marsh through management and use of renewable natural resources, including waterfowl, alligators, furbearers, and estuarine organisms. 4. Reverse habitat deterioration by implementing established and experimental marsh management practices on the area. 5. Develop a mineral management program to minimize the environmental impact of mineral exploration, extraction, and transportation. Prior to implementation of marsh management measures, the fresher marshes north of Little Pecan Island were plagued with water hyacinths {Eichhornia crassipes) and lacked an abundance of waterfowl food plants. Tidally influenced marshes south of Little Pecan Island were not plagued with water hyacinths, but were adversely affected by excessive fluctuations in salinity and water levels brought about by the channelization of the lower Mermentau River. The impacts of these channelization/dredging projects were compounded by the operation of the Catfish Point Control Structure. This structure and the Schooner Bayou Control Structure were designed to convert Grand and White Lakes into a freshwater impoundment to supply irrigation water for rice farmers to the north. During periods of low river discharge, the water control structure at Catfish Point was closed to prevent saltwater intrusion into Grand and White Lakes. Downstream marshes were then deprived of riverine freshwater which buffered against marine influence. Tidal exchange, therefore, became more pronounced and brackish water moved further inland. Little Pecan Wildlife Management Area was protected to some extent from extreme fluctuations in water levels and salinities that occurred on the lower Mermentau River because of its location several miles up Little Pecan Bayou. Salinity readings recorded on a weekly basis indicated salinities were in the fresh to intermediate range throughout most of the year. Under periods of extended drought, however, salinities often peaked in the 15-20 ppt range (Figure 2). Water levels at LPWMA were capable of large tidal and seasonal fluxes. Tidal marshes along Little Pecan Bayou were occasionally dewatered during periods of strong north winds and low river discharge. Conversely, when heavy rains occurred throughout the Mermentau River watershed, water levels in Grand and White Lakes rose quickly. Excess water was discharged through the lower Mermentau River via the Catfish Point Control Structure. As a result, the coastal marshes experienced prolonged periods of backwater flooding. Two severe floods occurred from January 1984 to March 1988. 279 2, a e s 3 a s v. 93 s ■a i 3 a o e it a 3 2! 280 - en o ([8A»[ eas U98iu 'wo) 13A31 y31V« 281 J- CO < "8 9 a t 3 JSf cu un irj Hdd) A1INI1VS 282 CO en - ca - to s 1 o «* s a e U t s (taASi 93S UB3U1 cwo ) T3A31 N31VM 283 00 ai C\J i — CVJ "8 s % a d O g en CO to CO to co ir5 I fa U<*d) A1INI1VS 284 - c/j X I— ■z. o 1 a I - ~3 (18AS[ B9S U9SW « WO ) 13A31 y3iVW 285 CM IT) LO (}dd) A1INHVS 286 Under these adverse hydrologic conditions, plant diversity and wildlife and fishery habitat quality were reduced. To enhance the wildlife habitat of these marshes, Taylor and his staff constructed ni.ie marsh semi-impoundments. Each semi-impoundment was managed through the use of one or more flap-gated, variable-crested water control structures. Semi-impoundment 2, however, was managed through the use of a variable-crested weir until 1986, when a reversible flap gate was installed. Table 1 lists information concerning each semi-impoundment and its associated water control structures. Two large diesel-powered low-lift pumps provided forced drainage capability to the three large northern semi-impoundments (units 3, 4, and 9) via interconnecting tranasses. Variable-crested water control structures located on the interconnecting tranasses allowed these units to be managed independently or together. At LPWMA, the fresher marsh types were located in the northern and eastern areas (units 3, 4, and 9), whereas the more brackish marsh types were located in the southern and western areas (units 1, 2, 5, 6, 7, and 8). Despite being classified as fresh, intermediate, and brackish (Chabreck and Linscombe 1978), marshes throughout LPWMA were dominated by wiregrass (Spartina patens). METHODS Water Level Drawdowns The purpose of drawdowns at LPWMA was to enhance the production of high quality waterfowl food plants in order to attract ducks. These drawdowns simulated low water conditions that occurred more frequently prior to hydrologic modifications (canal construction) in the region. Gadwall (Anas strepera) was by far the most abundant and frequently harvested duck at LPWMA. Because the preferred foods of gadwall are aquatic plants such as sago pondweed (Potamogeton pectinatus), southern naiad (Najas guadalupensis) and widgeon grass (Ruppia maritima), drawdowns and marsh management practices were geared primarily toward the production and maintenance of these aquatic plants. A secondary objective of drawdowns at LPWMA was the germination and production of annual grasses whose seeds are preferred food of mallards (Anas platyrhynchos), teal (Anas spp.), and many other dabbling ducks. The ability of drawdowns to stimulate germination of annual grasses and submerged aquatic vegetation has been well documented (Lynch et al. 1947; Chabreck 1960; Kadlec 1962; Harris and Marshall 1963; Linde 1969; Fredrickson and Taylor 1982; Prevost 1987). The most commonly produced annuals included flatsedges (Cyperus sp.), Walter's millet (Echinochloa walteri), and bearded sprangletop (Leptochloa fascicularis). Drawdowns were normally attempted once every third to fourth year within any given semi-impoundment. Drawdowns were begun in March and terminated in June or July. Although three semi-impoundments had forced drainage capability, drawdowns in these areas were accomplished primarily through gravity drainage. Forced drainage was occasionally used to complete a drawdown when completion by gravity drainage was inadequate, or to remove accumulated rainfall when it threatened an otherwise successful drawdown. The occurrence of several wind-induced low tides associated with frontal passages in March and April greatly facilitated dewatering efforts. In order to maximize drainage during these exceptionally low tides, all stop-logs were removed. Rainfall during this period often prevented total dewatering. During June and July drawdowns became dependent on continued low precipitation and increasing rates of evapotransportation or forced drainage. Four factors were necessary to achieve a successful gravity drainage drawdown: 1) setting water control structures deep enough to allow drainage of ponds; 2) designing and installing water control 287 Table 1. Water control structure and semi-impoundment information for Little Pecan Wildlife Management Area, Cameron Parish, LA. Semi- impoundment Area number hectares Water control structure Invert elevation (marsh level8) Description6 164 -128 cm 1, 183 cm wide, flap-gated variable -crested, wooden box-chute 2 3 145 639 -61 cm -128 cm 1, 122 cm wide, variable-crested, aluminum weir 2, 183 cm wide, flap-gated, variable -crested, wooden box-chute 537 -128 cm 1, 183 cm wide, flap-gated, variable-crested, wooden box chute 262 ■128 cm -128 cm -52 cm 1, 122 cm diameter, flap-gated, variable-crested, corrugated aluminum culvert 1, 122 cm diameter, flap-gated, variable-crested, corrugated aluminum culvert. 2, 244 cm wide, flap-gated, variable-crested, aluminum weir 172 -128 cm -52 cm 1, 122 cm diameter, flap-gated, variable-crested (244 cm wide), corrugated aluminum culvert 1 , 244 cm wide, flap-gated, variable-crested, aluminum weir 8 Little Pecan Lake 86 19 428 174 -91 cm -76 cm •128 cm -128 cm 1, 91 cm diameter, flap-gated variable-crested (183 cm wide), corrugated aluminum culvert 1, 61 cm diamter, flap-gated, variable-crested (122 cm wide), corrugated aluminum culvert 2, 122 cm diameter, flap-gated, variable -crested, corrugated aluminum culvert 1, 122 cm diameter, flap-gated, variable-crested, corrugated aluminum culvert amarsh level = 1.4' mean sea level Kveir crest width not reduced to include the flanges associated with the stop-log channels 288 structures of adequate drainage capacity; 3) operation of water control structures to maximize gravity drainage discharge (e.g., removing all stop-logs); and 4) using periods of low precipitation and low tides to facilitate gravity drainage. Larger semi-impoundments were slower to dewater than smaller semi- impoundments. For example, semi-impoundment 8 (10 ha) could be completely dewatered in two days of exceptionally low tides. Under the same tidal conditions, however, only 5.1-10.2 cm of water could be drained off the larger semi-impoundments. These observations suggest that larger semi-impoundments may need proportionally more drainage capability than smaller semi-impoundments. For this reason, improvements at LPWMA often involved the installation of additional flap-gated, variable -crested culverts in the larger semi-impoundments in order to increase drainage capacity and drawdown success (See Table 1). Total drainage capability per marsh semi-impoundment at LPWMA averaged 215% greater than that recommended by current U.S. Soil Conservation Service guidelines (See Table 2); however, gravity drainage capacity on larger semi-impoundments was found to be only adequate. When drawdowns were attempted at LPWMA, the goal was to dry and crack the pond bottoms within that semi-impoundment. This was necessary to consolidate bottom sediments and promote the proliferation of submerged aquatic plants (Joanen and Glasgow 1965). Although pond bottoms had to be dewatered to stimulate the germination of annuals, extensive drying was not usually necessary or desirable. Miller and Arend (1960), Burgess (1969), and Prevost (1987) found that annuals germinated better on moist soil than dry soil. After initial drying and germination, annuals appeared to fare better when occasional showers or residual water kept the pond bottoms moist. Other researchers have found Table 2. Comparison of drainage/exchange capacity of semi-impoundments at Little Pecan Wildlife Management Area, Cameron Parish, LA., versus that recommended by current Soil Conservation Service guidelines. Semi- Drainage % drainage impoundment Existing recommended capacity exceeds SCS number drainage capacity by SCS Difference recommendations 1 23,411 cm2 4,552 cm2 18,859 cm2 414% 2 13,006 cm2 4,552 cm2 8,454 cm2 186% 3 46,822 cm2 13,192 cm2 33,630 cm2 255% 4 35,116 cm2 13,192 cm2 21,924 cm2 166% 5 32,143 cm2 6,596 cm2 25,548 cm2 387% 6 21,924 cm2 4,552 cm2 17,372 cm2 382% 7 6,596 cm2 2,880 cm2 3,716 cm2 167% 8 2,880 cm2 1,115 cm2 1,765 cm2 158% 9 23,411 cm2 9,104 cm2 14,307 cm2 157% Little Pecan Lake :a 11,705 cm2 8,918 cm2 2,787 cm2 31% Average difference15 215% aSemi-impounded lake Calculation excluded Little Pecan Lake and those semi-impoundments (units 5 and 6) where the installation of the desired type and size water control structure was not permitted by the regulatory agencies. 289 that growth and seed production of annuals were enhanced when soils were saturated or flooded to approximately one-third the height of the recently germinated annuals (Chabreck 1960; Kadlec and Wentz 1974; Fredrickson and Taylor 1982). With cooperative weather, many ponds were completely filled with dense growths of Walter's millet, bearded sprangletop, and flatsedges. Despite being short lived, annual vegetation was quite often so thick that it obscured the ponds and interfered with waterfowl use and hunting. Virtually all traces of annual vegetation were gone by the following year. In its place, desirable submerged aquatic plants such as sago pondweed, southern naiad, and widgeon grass often filled the water column throughout the pond. Over several years, the density of aquatic plants would gradually taper off, and through plant succession, undesirable aquatics such as coontail (Ceratophyllum demerswri) and Musk-grass (Chara spp.) would become dominant. At this point, a drawdown would be initiated to set back plant succession. Despite successful dewatering and drying, annual grasses did not always appear in the brackish semi-impoundments. In these areas, dwarf spikerush and some flatsedges were often the only desirable plants to germinate in response to a drawdown. According to Prevost (1987), soils in brackish marshes should be maintained in a saturated or moist condition to prevent the development of acid conditions which reduce germination of annuals and other desirable perennials. At conditions conducive to the LPWMA, however, extensive drying was necessary to consolidate bottom sediments and produce proliferation of aquatic vegetation (Joanen and Glasgow 1965). When reflooded with freshwater, ponds soon filled with desirable freshwater aquatic plants. If refilled with brackish water, widgeon grass and dwarf spikerush often filled ponds. During the dewatering process, deeper pond bottoms were temporarily dried, then refilled by occasional showers (Figure 3). Upon reflooding, aquatic plants often flourished in deeper pond areas while annuals flourished in shallower ponds, a situation most desirable for waterfowl use and hunting. In 6 out of 12 years, successful drawdowns were achieved at LPWMA through late spring and early summer droughts. The ability to achieve specific water level management goals was largely weather dependent. As a result, management plans were frequently modified during the course of any given year. Water Level and Salinity Stabilization The purpose of stabilization management was to maintain relatively constant conditions for the growth of submerged aquatic plants and the survival of freshwater finfishes and estuarine organisms. Stabilization management was usually conducted for at least two consecutive years after a drawdown. Under stable conditions, submerged aquatic plants grew best in fresher semi- impoundments the year following a drawdown. Similar observations were made by Harris and Marshall (1963) and Linde (1969). Submerged aquatic plants grew best in brackish semi- impoundments immediately following reflooding. Stabilization management was terminated when undesirable aquatic vegetation became dominant. Water exchange was allowed to the maximum extent possible, provided that management goals were not compromised. Water exchange, however, was often restricted to maintain stable aquatic conditions during adverse meteorologic and/or hydrologic conditions. Flap gates were closed during periods of drought and stop-logs were set to marsh level to protect against rising salinities and falling water levels. Flap gates were occasionally closed to prevent turbid outside waters from entering semi-impoundments and retarding growth of submerged aquatics. During periods of high rainfall, stop-logs were removed and flap gates were operated to keep water levels from standing over the marsh floor. With water standing on the marsh, decomposition of marsh vegetation created oxygen depletions, often resulting in fish kills. 290 CO en E 1/5 - CO * s 0) ni o 0) 0 t ( l3as[ eas ueaw «uio) 13A3"| dBlVM B go e 291 IS) ■p c 0) E E ID OO - en "8 a a rs (13A31 eas ueam «uio) -\31\31 y31VM 292 During March and April, water levels within semi-impoundments were reduced approximately 5.1- 10.2 cm below marsh level for three to four weeks. Light penetration to the bottom was increased, encouraging the growth of aquatic vegetation. Similar water level regimes were found to enhance production of widgeon grass (Joanen and Glasgow 1965). Water levels were maintained approximately at marsh level for the remainder of the growing season. During droughts, however, water levels within semi-impoundments occasionally fell to levels equal to those of a partial drawdown (Figure 4). Water Hyacinth Control Controlled introductions of brackish water were used to eradicate water hyacinths within infested semi-impoundments at LPWMA Prior to the introduction of brackish water, semi-impoundments were partially dewatered. This procedure reduced the dilution of brackish water within semi- impoundments and increased treatment effectiveness. When continually exposed to salinities of 4 ppt, water hyacinths died within 3 weeks. High salinity waters (8-16 ppt) were introduced to affect a quicker kill and to overcome any immediate or future salinity dilution (due to precipitation). During the summer of 1985, salinities of 10 ppt or higher were held for approximately 2 weeks throughout semi-impoundment 3 (Figure 5). This brackish water introduction was one of the most successful ever conducted at LPWMA Although water hyacinths were totally eradicated from several semi-impoundments, freshwater aquatic plants were also killed by this introduction of brackish water. Within a month, however, heavy rains associated with frequent summer thundershowers diluted salinities to less than 2 ppt. Desirable aquatic vegetation soon reappeared when the water freshened but were not as abundant as in normal years. Considering the effectiveness, the expense, and the personnel needed to control water hyacinths through the use of herbicides, controlled introduction of brackish water was a far superior method despite its temporary adverse effect on freshwater aquatic vegetation. Introduction of Estuarine Organisms Brackish water was frequently introduced into semi-impoundments at LPWMA to allow ingress of estuarine organisms, especially white shrimp (Penaeus setiferus), brown shrimp (Penaeus aztecus), and blue crab (Callinectes sapidus). Brackish water and juvenile estuarine organisms occurred at LPWMA primarily in association with late spring and early summer droughts. Recruitment of post- larval white shrimp into the estuary (during June and July) often coincided with the occurrence of brackish water at LPWMA Therefore, introduction of estuarine organisms at LPWMA focused on the available and marketable white shrimp. When juvenile shrimp were thought to be present or were collected in Little Pecan Bayou, water control structures were operated to allow ingress of estuarine organisms. In semi-impoundments where widgeon grass was the dominant aquatic plant, free water exchange was allowed if turbid waters or low tides did not threaten aquatic vegetation. In most semi-impoundments, freshwater aquatics were dominant. Water exchange in these units was allowed if salinities remained at or below 4-5 ppt. When salinities of outside waters were low, flap gates were raised and stop-logs removed to maximize water exchange. Tidal flushing also appeared to reduce the severity of filamentous algae blooms which often formed mats at the water's surface and smothered out desired aquatic vegetation. When the salinities of outside waters were high, water exchange was restricted by varying the weir crest elevations. Water Level Management During Waterfowl Season A month prior to waterfowl season, water control structures were set to draw water levels down to marsh level or slightly below. This procedure helped to make submerged aquatic plants more 293 CO a «s «-• a E ■o a 3 8. s CO en a* it) U & 3 - ~3 (V a CM ^ O a a (l3A8t ess ueauj «iuo) 13A31 cGiVM O n 294 - tn "8 s *■ s (13A8L BBS U99U1 ' UID ) 13A31 H31VM 295 CO o 2: M n *• * o ** -j 2 M 2 2 5 a « (19A31 eas ueauj «iuo) 13A31 d31VM Cm 4> 00 e V© 00 S3 S a 3 I *■* a a a 3 8. o E •£ 2% < 1 a t a Udd) A1INHVS 297 available to waterfowl. As waterfowl season progressed, water levels within semi-impoundments were reduced to the maximum extent possible without preventing hunter access. In addition to making aquatic vegetation more available, reduced water levels helped to maximize optimal dabbling duck feeding habitat (depths of 5.1-20.3 cm). Ditching In 1975, personnel at LPWMA began planning a tranasse network in each of its nine semi- impoundments. Existing tranasses and borrow pits were used when possible. The following goals were used to plan the construction of new tranasses: (1) to provide access for hunting, fishing, trapping, and monitoring even during low water periods; (2) to increase diversity for wildlife and fish populations; (3) to provide travel corridors for estuarine organisms in order to maximize use of semi- impoundments; (4) to provide fire breaks during controlled burns; and (5) to facilitate water exchange during drawdowns and flooding. Tranasses were dug 8 ft wide and 6 ft deep by a marsh machine (dragline mounted on pontoons). Tranasses provided sufficient depth to allow mudboat access during spring and summer drawdowns. Spoil deposits were staggered to maintain water flow patterns. Periodic maintenance of tranasses was done every 3-4 years to remove encroaching vegetation and silt deposits. Tranasse maintenance was accomplished by a marsh machine using a pipeline backfill blade. Use of the backfill blade was found to be more efficient than use of a dragline bucket. Controlled Burning A common management technique practiced at LPWMA was controlled burning. This was usually done in February or March following the fur trapping season. The primary purpose was to retard plant succession and stimulate growth of wildlife food plants. The decision to burn was made when climax species dominated large areas, when dead or dying vegetation was abundant, or when undesirable vegetation grew. Burning was conducted on a 3 or 4 year rotation depending on vegetative condition. Sections within each semi-impoundment were burned with water bodies and tranasses serving as natural fire -breaks. Several unburned areas were left in each semi- impoundment to provide food and cover for furbearers and other wildlife during the revegetation process. Fires were set by personnel using matches or a torch while traveling in a boat. Backfires were set around duck blinds, pumping stations, water control structures, and other fire sensitive areas. Extreme caution was taken to insure the safety of humans and property. Trespass Control of Property During the early years of LPWMA, it was imperative that trespass control of the area be established. Daily patrols were initiated to inform anglers and other individuals that LPWMA and its waterways were closed to the public. Public notice for closure of the property was included in 298 the Miami Corporation fishing permit. This was necessary to reduce poaching, vandalism, theft, and tampering with water control structures and to insure the success of the management program. Mineral Management Planning meetings, between LPWMA staff and oil company representatives, were held before any mineral activities were initiated. Exploration drilling and development programs were modified to be compatible with overall fish and wildlife management goals. From 1975 to 1987, nine well location canals were dredged on LPWMA. Continuous spoil deposition was used to maintain the integrity of the semi-impoundment system. Mitigation, regulated and provided by governmental agencies was used to counter detrimental environmental impacts. Levee construction, water control structure installation, and water control structure maintenance were mitigation projects implemented on the area. Communication between staff personnel, governmental agency personnel, and oil company representatives minimized adverse environmental impacts associated with mineral development activities. RESULTS AND DISCUSSION Waterfowl Habitat Enhancement Water level and salinity management of semi-impounded marshes was very successful in promoting the growth of high quality waterfowl food plants. Management success was due to 1) sufficient drainage capacity of water control structures; 2) operational flexibility of water control structures; 3) weekly monitoring of water level and salinities; 4) experienced staff personnel on call 24 hours/day, and; 5) a well planned tranasse system. An adverse effect of water level and salinity management practices at LPWMA was the encroachment of emergent perennial plants into shallow open waters of fresh and intermediate semi-impounded marshes. Similar effects have been observed in actively managed semi-impounded marshes at Rockefeller Refuge (Wicker et al. 1983). In seasonally flooded upland impoundments that were dewatered annually, dense growths of emergent perennials were found to invade open water areas unless plant succession was set back (Linde 1969; Fredrickson and Taylor 1982). At LPWMA drawdowns and partial drawdowns allowed giant cutgrass, bullwhip, and jointgrass to invade shallow pond bottoms. Encroachment by emergent perennials appeared to be facilitated by very gradual reductions in water levels when pond bottoms remained saturated or damp for long periods. Several consecutive years of partial drawdowns caused some ponds at LPWMA to fill with cutgrass, bullwhip, and jointgrass. To make room for plants having greater waterfowl and wildlife food value, attempts were made to eradicate these perennials. Introduction of brackish water used to control water hyacinths was generally ineffective in controlling perennial plant encroachment. When brackish waters (5-6 ppt) were held in Little Pecan Lake for 1-2 months, extensive stands of cutgrass along the lake edge (and especially those growing in deeper water) were virtually destroyed. Encroaching perennials were effectively controlled by treating with herbicides (2-4-D or Rodeo) sprayed via helicopter. Jointgrass was the most troublesome emergent perennial. During periods of low water levels, it would rapidly encroach upon shallow pond bottoms. Upon return to normal water levels, its ability to tolerate shallow flooding allowed jointgrass to survive. Its dense network of roots, foliage, 299 and interconnecting runners were then able to trap sediment and organic material, allowing it to convert shallow open water to emergent marsh. Jointgrass tolerated short term exposure (3 weeks) to salinities of 14 ppt. Several ponds were severely reduced in size by encroaching jointgrass. Burns conducted during periods of low water were not successful in reopening ponds choked by invading jointgrass. Where aquatic vegetation reached the water surface, filamentous algae often formed surface mats, smothering desirable aquatic plants. Prevost (1987) found that vigorous water circulation and gradually increasing water levels helped prevent this problem. The encroachment of emergent perennial plants into shallow open areas of fresh and intermediate marshes at LPWMA indicates that water level (drawdown) and salinity management may be capable of stimulating revegetation of emergent wetlands. In deteriorated intermediate and brackish marshes, the coverage of emergent perennials within four semi-impoundments at Rockefeller Refuge has steadily increased in response to 28 years (1958-86) of drawdown management. Furthermore, at Rockefeller Refuge, the most aggressive perennials are giant cutgrass and various species of the genera Paspalum (Ted Joanen, Rockefeller Wildlife Refuge; pers. comm.). Encroachment by giant cutgrass, bullwhip, and especially by jointgrass has also been observed in response to drought (and prolonged periods of low water levels) in other intermediate marshes of Cameron Parish, LA (Dr. Robert Chabreck, Louisiana State University; pers. comm.; Bruce Lehto, District Conservationist, Soil Conservation Service, Calcasieu and Cameron Parishes, LA; pers. comm.). Annuals and emergent perennials were found to close in and engulf ponds that were dewatered annually in a Wisconsin marsh; therefore, it was recommended that drawdowns be conducted only once every 3 to 4 years (Linde 1969). Germination of emergent perennial plants at Little Pecan Lake did not occur during extensive drawdowns when pond bottoms were severely dried. Germination occurred most often when pond bottoms were saturated or flooded to depths of only 2.5-5.1 cm. In moist-soil management areas, which are dewatered annually, Miller and Arend (1960), Kadlec and Wentz (1974), and Frederickson and Taylor (1982) found that germination of both annual and perennial plants was severely reduced once saturated soils dried for more than several days. Summarizing published literature, Kadlec and Wentz (1974) found that optimum conditions for the germination and establishment of many annual and perennial wetland plants occur on moist soils or in very shallow water. In greenhouse experiments, Weller (1975) found that when common cattail (Typha latifolia) seeds were exposed to various water depths ranging from 2.54 to 50.8 cm, germination occurred more readily at depths between 2.54 and 15.2 cm. In the field however, Beule (1979) observed that in the vast majority of cases, germination of common cattails occurred on exposed mud flats. Encroachment by emergent perennial plants at LPWMA occurred primarily through vegetative propagation during periods of low water when pond bottoms were either saturated or flooded to depths of only several inches. Similar effects have been observed by others (T. Joanen, pers. comm; R. Chabreck, pers. comm.). In greenhouse experiments, common cattails produced nearly twice as many rhizome shoots at water levels less than 15.2 cm versus water levels greater than 15.2 cm (Weller 1975). In coastal marshes of Louisiana, increased water levels have been found to reduce survival, growth, and productivity of wetland plants (Salinas et al. 1986). Without a period of low water, stands of emergent perennial vegetation in northern freshwater marshes have been observed to decline. When these areas were dewatered, however, a remarkable rejuvenation of perennial vegetation was observed (Kadlec 1962; Linde 1969; Kadlec and Wentz 1974). 300 In coastal Louisiana, the dredging of canals and associated spoil deposits have resulted in the unintentional impoundment of large wetland areas. These unintentional impoundments have been shown to exhibit high rates of wetland loss (Turner 1987). In many instances, however, the degradation and loss of wetlands in these existing unintentional impoundments could be reversed through the installation and operation of water control structures to provide water level md salinity control management as was conducted at Little Pecan. Waterfowl Harvest Detailed waterfowl harvest data were collected at LPWMA from 1975-87. No comparable harvest statistics from outside sources are available for analysis. Harvest data from LPWMA can be correlated with the U.S. Fish and Wildlife Service fall flight forecast (Table 3). LPWMA harvest data for 1975 through 1985 were used for discussion since hunting days and bag limits were constant. Years 1982-83 and 1984-85 were omitted from discussion because fall floods reduced hunter success and waterfowl utilization. Fall flight forecasts were relatively high during 1975 (96 million), but hunter harvest at LPWMA (4.2 birds/hunter/day) was rather low. Poor habitat conditions from 1975-76 to 1977-78 limited hunter success and waterfowl use. As the management program progressed, hunter success increased and peaked in 1980-81 (7.9 birds/hunter/day), despite a drop in the fall flight forecast from 95 million in 1979-80 to 80 million in 1980-81. After 1980-81, hunter success declined as a result of reduced continental waterfowl populations, semi-impoundment drawdowns prior to hunting season, and reduced season lengths and bag limits. Data from 8 of the 12 hunting seasons were used for statistical analysis, since season lengths, bag limits, and environmental conditions remained constant. Hunting seasons 1982-83 and 1984-85 were Table 3. The relationship between the average number of birds harvested/hunter/day at Little Pecan Wildlife Management Area, Cameron Parish, LA, and the U.S. Fish and Wildlife Service fall flight forecasts. Average no. birds Fall flight Year harvested/h unter/day forecasts (million) 1975-76 4.2 96 1976-77 3.9 88 1977-78 5.0 85 1978-79 7.0 90 1979-80 7.7 95 1980-81 7.9 80 1981-82 5.6 77 1982-83 4.0 76 1983-84 5.8 83 1984-85 4.6 80 301 omitted from statistical analysis because fall flooding biased the data. Hunting seasons 1985-86 and 1986-87 were also omitted from analysis, since season lengths and bag limits were reduced. During the first three waterfowl seasons, the habitat management program at LPWMA was in a developmental stage. Waterfowl harvests during this period were relatively low (Table 4). Hunting success increased during the fourth season (1978-79) and peaked during the sixth season (1980-81). A "T test" was used to compare waterfowl harvest results during the developmental period (1975-76, 1976-77, 1977-78) to the management period (1978-79, 1979-80, 1980-81, 1981- 82, 1983-84). A significant difference (P<.05) between the two groups was detected. These data indicate the intensive marsh management program, excluding the 3-year development period (1975-77) and the two fall flood years (1982 and 1984), provided optimum habitat for wintering waterfowl and satisfactory hunter success. Effects of Drawdowns on Waterfowl Harvest Spring drawdowns were conducted in at least one semi-impoundment during 6 out of the 12 years LPWMA was intensively managed (Table 5). Waterfowl harvest data from 1978-79 to 1981- 82 have been used to compare the effects of drawdown to non-drawdown management (Figure 6). The average number of birds harvested/hunter/day for each group was 7.0 and 5.6 during drawdown years and 7.7 and 7.9 during non-drawdown years (Table 5). Spring drawdowns prior to the fall waterfowl season generally reduced hunter success and waterfowl use. Ponds and open water areas were filled with dense stands of annual vegetation. The vegetation fell after several freezes in January, creating open areas which ducks used after ponds opened. Dense emergent vegetation produced during spring drawdowns made it necessary to mechanically open hunting ponds prior to waterfowl season. Table 4. Waterfowl hunting season results for Little Pecan Wildlife Management Area. Maximum allowable daily Average no. birds Total number Year Hunting days harvest/hunter harvested/hunter/day ducks harvested 1975-76 55 10 4.2 2,889 1976-77 55 10 3.9 2,617 1977-78 55 10 5.0 3,454 1978-79 55 10 7.0 5,676 1979-80 55 10 7.7 6,611 1980-81 55 10 7.9 6,740 1981-82 55 10 5.6 4,782 1982-83 55 10 4.0 5,298 1983-84 55 10 5.8 4,610 1984-85 55 10 4.6 3,875 1985-86 45 5 4.6 3,068 1986-87 45 5 5.2 3,334 302 Table 5. Marsh habitat conditions at Little Pecan Wildlife Management Area from 1975 to 1987. Year Spring Summer Fall Winter Waterfowl habitat 1975-76 Wet Wet 1976-77 Dry Dry 1977-78 Wet Wet 1978-79 Dry Wet 1979-80 Wet Wet 1980-81 Flood Flood 1981-82 Dry Wet 1982-83 Wet Wet 1983-84 Flood Wet 1984-85 Dry Wet 1985-86 Dry Dry 1986-87 Dry Wet Wet Wet Wet Wet Wet Wet Wet Wet Wet Semi-wet Semi-wet Wet Wet POOR-Marsh inundated with water hyacinths. IMPROVED- Water hyacinths controlled, abundant annual vegetation. GOOD-Residual annuals. Abundant aquatic vegetation. EXCELLENT-Reflooded by July 1. Abundant annuals and aquatics. EXCELLENT-Avg. water level +2.0 MSL. GOOD-Food, cover, and water for wintering waterfowl. FAIR-Used saltwater during summer to control water hyacinths. Wet Flood Flood FAIR-Late fall and winter flood impacted habitat. Wet Wet FAVORABLE-Abundance of aquatics. Flood Wet FAIR-Annuals and aquatics. Flood Wet FAIR-Annuals, marsh failed to produce late crop of aquatics. Wet Wet FAIR-Annuals and aquatics. Drawdowns improved long term habitat conditions and increased hunter success by replenishing the seed bank, setting back vegetative succession, and promoting the growth of high quality aquatic vegetation during subsequent non-drawdown years. Fur Harvest Fur trapping was conducted on LPWMA from the 1975-76 fur trapping season through the 1986- 87 season except during the 1982-83 season (Table 6). The decision not to trap that year was based on a poor fur price and low furbearer population estimates. It was hoped that the population would expand to a more harvestable level the following year. According to Chabreck and Linscombe (1978), semi-impoundments 1,2,7, and 8 were brackish; 5 and 6 were brackish-intermediate; 3 and 4 were intermediate-fresh, and 9 was fresh. Since 303 CM CO I CO 05 CD I CO O C I 00 i_ T3 I C o I it I 1 a a. V C J u I 00 CO CO CsJ AVQ/!d31NnH/a31S3AyVH IMOjyaiVM 'ON -0AV 304 Table 6. Nutria harvest data (1975-76 through 1986-S7) by semi-impoundment for Little Pecan Wildlife Management Area. Brackish Intermediate 3 4 Fresh 9 12 5 6 7 8 Year (164 (145 (262 (182 (81 (10 (639 (537 (428 TOTAL ha) ha) ha) ha) ha) ha) ha) ha) ha) 1975-76 Only trapped 1-4 (others under construction) 1,495 1976-77 Only trapped 1-6 (others under construction) 1,836 1977-78 78 141 571 378 192 1,360 1978-79 23 684 184 90 981 1979-80 98 115 260 33 23 15 943 389 124 2,000 1980-81 27 105 189 63 25 5 846 436 114 1,810 1981-82 21 47 123 46 17 386 121 8 769 1982-83 No trapping on Little Pecan Wildlife Management Area 1983-84 97 102 159 90 883 232 50 1,613 1984-85 281 93 687 232 157 1,450 1985-86 175 138 86 64 93 1 889 353 288 2,087 1986-87 230 149 195 75 20 744 163 171 1,747 several of the semi-impoundments were mixed marsh types, these semi-impoundments were categorized as follows: (1) Semi-impoundments 1,2,5,6,7, and 8 were considered to be brackish because of the dominance of wiregrass and the absence of bulltongue (Sagitarria sp.). (2) Semi-impoundments 3 and 4 were considered to be intermediate because of the dominance of wiregrass and bulltongue and the absence of maidencane {Panicwn hemitomon). (3) Semi-impoundment 9 was considered fresh despite the dominance of wiregrass and bulltongue. Fur management focused on nutria {Myocastor coypus) since it was the most abundant furbearer on LPWMA. Nutria harvest data from 1977-78 through 1985-86 averaged 1/2.1 ha in brackish semi-impoundments, 1/1.2 ha in the intermediate semi-impoundments, and 1/3.2 ha in fresh semi- impoundments. In the Chenier Plain of southwest Louisiana from 1970-71 to 1980-81, Linscombe and Kinler (1985) found that one nutria was harvested per 3.0 ha of brackish marsh, 2.3 ha of intermediate marsh, and 1.4 ha of fresh marsh. This suggests fur harvests from brackish and intermediate semi-impoundments on LPWMA were greater than the respective Chenier Plain average. In the fresh marsh, the average fur harvest was greater than in the fresh marsh semi- impoundment on LPWMA. Better harvests in the brackish and intermediate semi-impoundments may be attributed to the following factors: 305 (1) Stable water levels and a well developed network of tranasses allowed trapper access even during periods of extreme low water. (2) Water level and salinity management created a diversity of vegetation and habitat conditions conducive to furbearers. (3) Since large alligators are furbearer predators, areas having high populations of large alligators and low furbearer populations were targeted for the selective harvest of alligators. (4) Certain areas within each semi-impoundment were burned so that food and cover remained available during the revegetation process. The relatively low furbearer harvest in semi-impoundment 9 may be attributed to poor trapper access from extreme water hyacinth infestation. From the 1975-76 season through the 1984-85 season, approximately 50% or more of the area remained choked with water hyacinths despite herbicide treatments. In 1985, brackish water introduction into semi-impoundment 9 was successful in eradicating water hyacinths. Access was then opened to the entire area and the harvest increased to 1/1.9 ha during the last 2 years. Effects of Drawdowns on Fur Harvest Drawdowns did not appear to adversely affect nutria populations from the 1975-76 season through the 1985-86 season. In six instances the harvest of nutria improved after spring-summer drawdown. In seven instances, the nutria harvest decreased after a drawdown, and in six instances, there was no apparent difference. Since natural droughts and floods occur periodically, nutria and other furbearers have apparently adapted to a wide range of conditions. During a nutria tagging study in Louisiana, Kays (1956) concluded that nutrias usually remained in one general area throughout their lives. Adams (1956) stated that data from tagged nutrias strongly indicated that the daily cruising range seldom exceeded 0.18 km and under favorable conditions the range may be less. During an 11 month mark and recapture study, Robicheaux (1978) found that 80% of recaptured nutrias moved less than 0.4 km from the previous capture site. Even during drawdown, it appeared that nutrias did not emigrate from the LPWMA but remained within their home range. Alligator Harvest Alligator (Alligator mississippiensis) skin lengths over an 11 -year period averaged 203.2 cm at LPWMA and averaged 213.9 cm for the State of Louisiana (Tables 7a and 7b) (Joanen and McNease 1987; LA Dep. Wildl. Fish., unpubl. harvest records 1984-86). These data reflect a stable alligator population for both LPWMA and Louisiana. A progressive decrease in skin lengths over time would indicate a decline in the alligator population. Over an 11 -year period the average success rate was 99.3% for LPWMA and 94.4% for the State of Louisiana. The excellent hunter success rate at LPWMA was due to a high alligator population and hunter efficiency. Sixty-four alligators were harvested in 29 hunting days in 1975, and 61 were harvested in 2 days in 1985. 'Semi-impoundments were used by alligators when Little Pecan Bayou and adjacent oilfield canals became highly saline (Figure 2). Little Pecan Lake was managed as a permanent fresh to 306 Table 7a. Alligator harvest statistics for Little Pecan Wildlife Management Area, 1975-86. Tags No. Success Avg. skin Year issued taken (%) length (cm) 1975 68 64 94.1 215.9 1976" 62 61 98.4 180.3 1977 77 77 100.0 228.6 1979 99 99 100.0 203.2 1980 97 97 100.0 198.1 1981" 72 72 100.0 188.0 1982 73 73 100.0 195.6 1983 73 73 100.0 210.8 1984" 67 67 100.0 198.1 1985" 61 61 100.0 193.0 1986" 74 74 100.0 221.0 Average 99.3 203.0 (6'8") a Adapted from Joanen and McNease (1987) and unpublished Louisiana Department of Wildlife and Fisheries harvest records 1984-86. Table 7b. Alligator harvest statistics for the State of Louisiana 1975-86. Tags No. Success Avg. skin Year issued taken (%) length (cm) 1975 4,645 4,420 95.2 226.1 1976" 4,767 4,389 92.1 215.9 1977 5,760 5,474 94.0 223.5 1979 17,516 16,300 93.0 213.4 1980 19,134 17,692 92.5 203.2 1981" 15,534 14,870 95.7 210.8 1982 18,188 17,142 94.2 208.3 1983 17,130 16,154 94.3 210.8 1984" 18,386 17,389 94.6 213.4 1985" 17,466 16,691 95.6 215.9 1986" 23,267 22,429 96.0 212.1 AVERAGE 94.4 213.9 'Adapted from Joanen and McNease (1987) and unpublished Louisiana Department of Wildlife and Fisheries harvest records 1984-86. 307 intermediate water body, which also served as a refuge for alligators during periods of high salinities. Water level and salinity stabilization enhanced alligator habitat on LPWMA Effects of Drawdowns on Alligator Harvest Drawdowns did not appear to adversely affect success of alligator harvests at LPWMA. The average alligator hunter success rate was 99.7% during drawdown years and 99.0% during non- drawdown years. Drawdowns did not appear to adversely affect success of alligator harvests at LPWMA (Table 7). Deep tranasses and borrow pits helped maintain alligator habitat within semi- impoundments during drawdowns. Although some alligators may have temporarily left dewatered semi-impoundments, adjacent permanent water bodies such as Little Pecan Lake, Little Pecan Bayou, and oilfield canals provided ample habitat. Fisheries Harvest White shrimp catches in 1984 and 1986 were conservatively estimated to average approximately 746 kg/yr or 1.8 kg/ha/yr. In 1985, white shrimp recruitment and productivity within Little Pecan Lake was excellent, until the crash of a heavy algae bloom in late October. Oxygen depletion associated with this algae bloom killed a considerable number of fish and shrimp. Subsequently, white shrimp catch decreased (approximately 559.5 kg/yr). In addition to providing good catches of white shrimp and occasionally brown shrimp, blue crabs were also numerous within the lake. Hundreds of crabs were harvested annually for personal consumption. Blue catfish (Ictalurus furcatus) and channel catfish (Ictalurus punctatus) were abundant within Little Pecan Lake. It was estimated that several thousand kilograms of live catfish were removed annually from the lake. Channel catfish averaged 0.47-0.75 kg, whereas the blue catfish averaged 0.75-1.9 kg. Individual blue catfish weighing 3.7-7.5 kg were frequently caught and the largest blue catfish ever caught in Little Pecan Lake weighed 19.4 kg. Observation of catfish stomach contents indicated that catfish preyed heavily on white shrimp from October through December. Game fish populations within the lake were low. Despite attempts to renovate the entire fish population, catfish have always dominated the fishery. Harvest of Fishery Resources within Brackish Semi-impoundments When ample recruitment opportunities were provided, densities of white shrimp within semi- impounded marshes appeared in some cases to be equivalent to that of adjacent unmanaged marshes. Several factors may have contributed to high shrimp catches in semi-impoundments: 1) abundant aquatic vegetation within semi-impounded marshes provided more cover, edge, and greater quantities of epiphytic food organisms; 2) fewer shrimp predators were found within semi- impoundments; 3) predator foraging activities were restricted by dense growths of aquatic vegetation and shallow water levels; 4) the extensive tranasse system improved access to isolated ponds; and 5) dewatered semi-impoundments were occasionally reflooded with brackish water to maximize ingress. In some instances, recruitment opportunities into semi-impoundments were not made available to estuarine organisms. Low densities of shrimp and other estuarine organisms were nevertheless often found within those semi-impoundments because leaking water control structures unintentionally provided recruitment opportunities. 308 Effect of Drawdowns on Fishery Harvest Drawdowns appeared to adversely affect freshwater game fish populations such as bluegill (Lepomis macrochirus), black crappie (Pomoxis nigromaculatus), and largemouth bass (Micropterus salmoides). Although deep ditching afforded fish some refuge, fish kills associated with low dissolved oxygen were occasionally observed in the ditches. Game fish populations appeared to be most abundant 2-3 years following a complete drawdown and were capable of supporting moderate fishing pressure. It is not certain, however, whether the population rebound was from the reproduction of surviving fish or from reproduction of new recruits. Largemouth bass weighing 1.1- 1.5 kg were occasionally caught during the third year following a complete drawdown. Dewatered brackish and semi-impoundments were often reflooded with brackish waters to maximize ingress of estuarine organisms. CONCLUSIONS Water level and salinity management within semi-impoundments was successful in stimulating the growth of preferred waterfowl food plants and enhancing waterfowl habitat. Waterfowl harvest analysis indicated a significant difference (P<.05) between the development and management stages of the marsh management program. Fur harvests at LPWMA were equal to or greater than corresponding harvests from the intermediate and brackish marshes of the Louisiana Chenier Plain. The 11-year average alligator harvest success rate for LPWMA (99.3%) exceeded the corresponding average success rate for the State of Louisiana (94.4%). Management of fresh and intermediate semi-impoundments allowed simultaneous production of estuarine organisms and the maintenance of freshwater game fish populations. Brackish water impoundments were successfully managed to enhance wildlife habitat and estuarine organism productivity. Habitat deterioration was reversed by implementing established and experimental marsh management practices. Drawdowns, water level management, and water salinity management caused both emergent and submergent vegetation to flourish within semi-impoundments. Nine location canals were dredged on LPWMA from 1975 to 1987. Mineral activities were modified to minimize detrimental environmental impacts and remain compatible with marsh management goals. Results achieved during 12 years of intensive marsh management at LPWMA indicate that the program was a success. LITERATURE CITED Adams, W.H. 1956. Ecological studies of coastal marsh in the vicinity of Price Lake, Rockefeller Refuge, Cameron Parish, Louisiana. M.S. Thesis. Louisiana State University, Baton Rouge. 118 pp. Beule, J.D. 1979. Control and management of cattails in southeastern Wisconsin wetlands. Wisconsin Department of Natural Resources Technical Bulletin No. 112, Madison. 41 pp. Burgess, H.H. 1969. Habitat management on a mid-continent waterfowl refuge. J. Wildl. Man. 33(4): 843-847. Chabreck, R.H. 1960. Coastal marsh impoundments for ducks in Louisiana. Proc. Annu. Conf. Southeast. Assoc. Game Fish Comm. 14:24-29. 309 Chabreck, R.H., and G. Linscombe. 1978. Vegetative type map of the Louisiana coastal marshes. Louisiana Department of Wildlife and Fisheries, New Orleans. Frederickson, L.H., and T.S. Taylor. 1982. Management of seasonally flooded impoundments for wildlife. U.S. Fish and Wildlife Service Research Publication No. 148. 29 pp. Harris, S.W., and W.H. Marshall. 1963. Ecology of water-level manipulations of a northern marsh. Ecology 43(2):267-281. Joanen, J.T., and L.L. Glasgow. 1965. Factors influencing the establishment of widgeongrass stands in Louisiana. Proc. Annu. Conf. Southeast. Game Fish Comm. 19:78-92. Joanen, J.T., L.L. Glasgow, and L. McNease. 1987. The management of alligators in Louisiana, U.S.A Pages 33-42 in G.J.W. Webb, S.C. Manolis, and PJ. Whitehead, eds. Wildlife management crocodiles and alligators. Surrey Beatty and Sons Pty. Ltd., in association with the Conservation Commission of the Northern Territory. Kadlec, J.A 1962. Effects of a drawdown on a waterfowl impoundment. Ecology 43(2):267-281. Kadlec, J.A, and W.A Wentz. 1974. State-of-the-art survey and evaluation of marsh plant establishment techniques, induced and natural. National Technical Information Service, Springfield, VA 2 vols. Kays, C.E. 1956. An ecological study with emphasis on nutria (Myocastor coypus) in the vicinity of Price Lake, Rockefeller Refuge, Cameron Parish, Louisiana. M.S. Thesis, Louisiana State University, Baton Rouge. 145 pp. Linde, AF. 1969. Techniques for wetland management. Wisconsin Department of Natural Resources Research Publ. No. 45. 156 pp. Linscombe, G., and N. Kinler. 1985. Fur harvest distribution in coastal Louisiana. Coastal Marsh Estuary Manage. Symp. 4:187-199. Lynch, J.J., T O'Neil, and D.W. Lay. 1947. Management significance of damage by geese and muskrats to Gulf Coast Marshes. J. Wildl. Manage. ll(l):50-76. Miller, AW., and P.H. Arend. 1960. How to grow watergrass for ducks in California. Game Management Leaflet No. 1., California Department of Fish and Game. 16 pp. Prevost, M.B. 1987. Management of plant communities for waterfowl in coastal South Carolina. In W.R. Whitman and W.H. Meredity, eds. 1987. Proceedings of a symposium on waterfowl and wetlands management in the coastal zone of the Atlantic Flyway. Coastal Management Program, Delaware Department of Natural Resources and Environmental Control, Dover. 522 pp. Robicheaux, B.L. 1978. Ecological implications of variably spaced ditches on nutria in a brackish marsh, Rockefeller Refuge, Louisiana. M.S. Thesis. Louisiana State University, Baton Rouge. 50 pp. Salinas, L.M., R.D. DeLaune, and W.H. Patrick, Jr. 1986. Changes occurring along rapidly submerging coastal area, Louisiana, U.S.A J. Coastal Res. 2(3):269-284. Turner, R.E. 1987. Relationship between canal and levee density and coastal land loss in Louisiana. U.S. Fish Wildl. Serv. Biol. Rep. 85(14). 58 pp. Weller, M.W. 1975. Studies of cattail in relation to management for marsh wildlife. Iowa State J. Sci. 49:333-412. Wicker, M.K., D. Davis, and D. Roberts. 1983. Rockefeller State Wildlife Refuge and Game Preserve -evaluation of wetland management techniques. Louisiana Department of Natural Resources, Coastal Management Section, Baton Rouge. 51 pp. 310 CAMERON-CREOLE WATERSHED MANAGEMENT PRELIMINARY REPORT Billy DeLany Sabine National Wildlife Refuge MRH Box 107 Hackberry, LA 70645 ABSTRACT The Cameron-Creole Watershed, Cameron Parish, LA, includes 45,749 ha of salt to fresh marsh ecosystem and is a major component of the Calcasieu Lake Estuary. This preliminary report is concerned with the initial management of marshlands adjacent to the eastern shore of Calcasieu Lake. The most abundant plant species is wiregrass (Spartina patens). Wiregrass appears to be unadaptive to increasing water salinity, and wiregrass marshes have been deteriorating before salt tolerant oystergrass {Spartina alterniflora) has been able to establish. Wiregrass communities near the center of the Grand Bayou marsh are becoming open lakes. Historical fresh and intermediate marshes at the perimeter have become deteriorating brackish marsh systems and open lakes. Initial management will be concerned with water control, soil stabilization and plant community establishment. Plant habitat management is the cornerstone of current management practices. Management after the initial two years will be expanded to include organism diversity and productivity. INTRODUCTION The Cameron-Creole Watershed Management project began in 1961. Agencies now involved are Cameron Parish Gravity Drainage Districts 3 and 4, U. S. Army Corps of Engineers, Louisiana Department of Wildlife and Fisheries, Louisiana Department of Transportation and Development, Louisiana Department of Natural Resources, U.S. Soil Conservation Service, National Marine Fisheries, and U.S. Fish and Wildlife Service. The plan developed by these agencies includes a recently completed 30.6-km protection levee along the eastern shore of Calcasieu Lake and contruction of five weirs which began in March 1988. This management plan was initiated because of apparent land loss in the Cameron-Creole marsh system. Reasons for land loss are saltwater intrusion, subsidence, sea level rise, lack of sedimentation, plant community die-off, and physical water action on exposed soil banks. Artificial changes in topography such as the Intracoastal Waterway (1914), Louisiana Highway 27 (1919), Calcasieu Ship Channel (1941), trapper's ditches (late 1940's), and oil and gas activities (1940's) have hastened marsh deterioration. The most prevalent species inhabiting the East Cove marsh are wiregrass, saltgrass (Distichlis spicata), black needlerush (Juncus roemerianus), and oystergrass. Areas of higher elevation and areas influenced by salty waters are becoming saltgrass flats. Low elevation wiregrass marshes that are subject to varying degrees of water energy are being invaded by either black needlerush or oystergrass, or have become open water. Plant communities along natural levees and cheniers contain remnant stands of leafy threesquare (saltmarsh bulrush) (Scirpus robustus), Olney threesquare (Scirpus olneyi), and California bulrush (Scirpus califomicus). One fresh to 311 intermediate marsh system occurs near the Intracoastal Waterway. Apparently, the freshwater introduction system presently there is maintaining low level salinities. Plant species observed in the fresh to intermediate marsh in fall 1987 were black willow (Salix nigra), pondweed (Potomogeton sp.), bulltongue (Sagittaria lancifolia), alligatorweed (Altemanthera philoxeroides), Jamaica sawgrass {Cladium jamaicense), water primrose (Ludwigia repens), seashore paspalum (Paspalum vaginatum), and wiregrass. Watershed objectives are to provide storm flood control and to increase marsh productivity by managing saltwater flow into the system. Initial management plans include a 2-year program of drawdowns and semi-static water control. Management thereafter will be adjusted as needed to apply the concept of holistic management. Data that may be used to accomplish this goal are plant salinity tolerances (SCS 1977), marsh open water salinities (Sabine National Wildlife Refuge, unpubl. data 1988), digitized habitat imagery (Liebowitz and Hill 1988), streamside sedimentation rates (Cahoon et al. 1988), estuarine organism ingress and egress data (Herke et al. 1987), channel water levels, soil redox potential, and evapotranspiration losses. Although nature will maintain the controls, management flexibility is essential. Natural parameters influencing management decisions are sea level rise, nearness to saltwater sources, lack of freshwater sources, physical water action (lunar and wind tides, channel width and depth, and increasing fetch), tropical storms, drought, and plant adaptations to such an environment. WEIR MANAGEMENT Five weirs are presently under construction. Noname and Peconi Bayou weirs will have fixed- crest weirs with four openings 2.3 m wide and crests set 0.2 m below mean marsh level (MML). Mangrove and Lambert Bayou will have variable crest weirs with four openings 3.1 m wide and capable of a crest of 1.2 m below MML. The Grand Bayou variable crest weir will have five openings 3.1 m wide, and four openings having flapgates leading out and low level capabilities of 1.2 m below MML. Except for the Grand Bayou weir, all other weirs will be equipped with three 15-cm by 1.2-m vertical slots. The middle structure at Grand Bayou will be a boat bay for estuarine organism ingress and sport fishermen access. Channels leading to each weir will be riprapped at a 45° angle to assist estuarine organism ingress and egress. During the first years of water management (phase 1) there will be drawdown from 15 February to 15 July. The drawdown is designed to lower water levels to 15 cm below mean marsh elevation at the 5 ppt isohaline line. Flapgates at Grand Bayou will facilitate the drawdown, while impeding inward tidal flow. At least one vertical slot at each weir will remain open. During the drawdown period, Sabine National Wildlife Refuge (NWR) will manage the weirs to allow for seasonal estuarine organism ingress and egress, to negate salt burns caused by extended drought, and to release flood waters caused by tropical storms and unusually heavy precipitation. After the drawdown, variable crest weirs will be set at 21 cm below MML, and the boat bay will be opened. Miami Land Corporation will supply one person to assist with weir openings and closings. Third year (phase 2) water management will be considered semi-static, and emphasis placed on enhancing fish and wildlife diversity. All weir crests will be set at 21 cm below MML; all vertical sl6ts, the boat bay, and one gate at Grand Bayou will remain open. During peak post-larva ingress and juvenile organism egress (brown shrimp, Penaeus aztecus, and white shrimp, P. setiferus), one more gate will be opened at Grand Bayou. 312 Thereafter, weir management will be a combination of science, accepted methods, and trial and error. WATER LEVELS AND FLOW Water levels at the 5-ppt isohaline line are to be maintained at levels ranging from 15 cm below marsh elevation to 6 cm above marsh elevation. Water level and tide data have been collected in Grand Bayou for several years, and this data collection will continue in Grand Bayou and in marsh soils at the evapotranspiration data collection site. These data will supply water-level information before and after weir placement and provide information needed to manage water levels and flow. Temporary closures of the boat bay and other bays will be allowed if salinities exceed 5 ppt. The effects of weirs on flow direction and volume in this system are unknown at this time. Estimated decreases in vertical plane area at Grand Bayou and Lamberts Bayou will be 88.2% and 91.0%, respectively. After the first year, waterflow may be managed to facilitate a viable drawdown from the eastern reaches of the marsh and allow ingress from the west, because waters flowing into the system should be at lower volumes and channels leading to the east will start to fill with sediment. SALINITY Isohaline lines of 12 and 5 ppt were determined using Chabreck's (1972) vegetative survey. Salinity data has been collected since 1966 for six stations within the Grand Bayou waterway (ECl- EC6). In October 1987, four more stations were established in Grand Bayou to determine saltwater movement further east into the marsh (EC7-EC10). Eleven stations were established along Highway 27 (H27 1-278) to determine saltwater movement to the eastern fringe of the East Cove marsh. Salinity stations were also established at each weir site and 0.4-0.8 km inland from each site to determine directional saltwater flow into the system. Data is collected every 2 weeks with a Yellow-Springs Instrument Co. model 33 salinity meter. Long term salinity averages from EC1, EC6, and EC5 indicate a decrease in salinities from the mouth of Grand Bayou to the headwaters of East Prong (Table 1). However, there are 2 periods when salinities are higher at EC5 than EC6. These are April through May and September through November. It is assumed that the seasonal decrease in precipitation, increase in Calcasieu Lake salinities, and continuing evapotranspiration are causes of increased open water salinities further inland. Recent data from EC7, EC9, and H277 indicate this trend; yet, it is not known if this data is representative of the long term average (Table 2). Data from Station H277 indicate it is a brackish water system until February. Station H277 is the furthest point northeast into the watershed. Based on plant salinity tolerance data (SCS 1977), long term monthly salinity averages are at stress levels for many historic and presently surviving plants (Table 3). Many of the plants once common to this marsh have disappeared with increased levels of water salinities, according to Berton Daigle, a life-long native of this area (pers. comm.). Three factors to consider when comparing these data and observations are (1) salinity data are averages and not the maximum salinities which have occurred, (2) salinity data are open-water salinities, not marsh-soil salinities that may maintain a higher salt content, and (3) average plant salinity tolerance data used here have rather large standard deviations and may reflect the variable water regime at the time of sampling plant stress levels. 313 Table 1. Long term monthly salinity averages (± SE) for Stations EC1, EC6, and EC5, 1966 to March 1988, East Cove marsh unit, Sabine NWR, Cameron Parish, La. Stations Month n EC1 n EOS n EC5 January 18 8.8 ± 1.4 18 6.5 ± 1.1 13 4.7 ± 1.4 February 18 7.2 ± 0.9 18 6.5 ± 0.9 12 5.0 ± 1.0 March 22 7.4 ± 1.0 21 6.2 ± 0.9 12 3.5 ± 0.7 April 18 10.0 ± 1.4 18 8.5 ± 1.4 8 9.0 ± 1.2 May 20 10.5 ± 1.7 20 9.1 ± 1.7 8 9.9 ± 3.2 June 17 9.3 ± 1.0 17 7.2 ± 1.0 7 5.1 ± 1.7 July 20 11.4 ± 1.3 18 8.8 ± 1.3 7 6.2 ± 1.4 August 13 12.8 ± 1.5 13 11.4 ± 1.6 5 8.5 ± 1.4 September 18 14.0 ± 1.3 17 12.4 ± 1.2 6 16.9 ± 1.8 October 19 13.4 ± 1.2 16 10.7 ± 1.4 6 13.0 ± 2.7 November 18 11.7 ± 1.7 18 9.7 ± 1.4 10 10.0 ± 2.2 December 13 8.2 ± 1.2 12 7.8 ± 1.5 10 7.1 ± 1.6 Table 2. Recent monthly salinity averages (± SE) for selected locations within the East Cove marsh unit, October 1987 to April 1988, Sabine NWR, Cameron Parish, LA. Salinity stations n EC7 EC9 H277 October 1 21.2 17.5 6.8 ± 2.2a November 1 22.5 19.2 7.5 December 3 12.1 ± 2.5 5.5 ± 1.1 7.5 ± 0.3b January 2 7.2 ± 1.2 6.2 ± 0.2 5.8 ± 0.8 February 2 4.2 ± 1.1 2.9 ± 2.9 3.5 ± 1.4 March 2 1.8 ± 0.1 1.4 ± 0.9 1.9 ± 0.6 April 2 4.7 ± 3.2 1.5 ± 1.4 2.0 ± 0.0 an = 2 bn = 4 OYSTERGRASS PLANTING Under the present water regimes, wiregrass communities directly influenced by Calcasieu Lake are dying and eroding. Oystergrass is invading but at a slower rate than that which is needed to maintain the soil. To increase the rate of oystergrass establishment, oystergrass plantings were initiated in mid-winter 1988 on a Grand Bayou sandbar and on dead wiregrass root mats. In 314 Table 3. Target marsh plant species salinity tolerance levels, unpublished 1988 data.) (Soil Conservation Service, Common name Scientific name Plant salinity tolerance (± SD) Oystergrass Spartina alterniflora 19.5 ± 7.8 Saltgrass Distichlis spicata 13.3 ± 6.7 Saltmarsh bulrush Scirpus robustus 8.9 ± 5.3 Wigeongrass Ruppia maritima 8.9 ± 6.4 Wiregrass Spartina patens 8.5 ± 6.3 Olney threesquare Scirpus olneyi 7.2 ± 5.1 Cattail Typha sp. 3.9 ± 4.1 Coastal waterhyssop Bacopa monnieri 3.9 ± 2.3 Walter's millet Echinochloa waited 2.9 ± 2.4 Alligatorweed Alternanthera philoxeroides 2.7 ± 4.9 Bulltongue Sagittaria lancifolia 1.7 ± 1.6 California bulrush Scirpus californicus 1.6 ± 1.2 Giant cutgrass Zizaniopsis miliacea 1.4 ± 1.9 January, a pilot program of bunch planting oystergrass in single rows at 1.5-m intervals was initiated. May 1988 plant survival and tillering data indicate that survival on bayou sandbars was 100% and on dead root mats was 90.6% (Table 4). Plant tillering data indicated that bunch plantings on sandbars had a fourfold increase over plantings on root mat. In March 1988, a pilot single-sprout transplanting program was initiated on dead root mat. Planting was done in single rows at 0.6-m intervals, and 1,037 linear meters of root mat were planted. Data will be collected on transplant survival in October 1988 and April 1989. The apparent limiting factors of transplant survival to date have been nutria (Myocastor coypus) depredation and boat wave action. In June 1988, 9,058 m along the banks of the Grand Bayou Louisiana State University experimental pond levee and an adjacent marsh lake southeast of East Prong will be planted with oystergrass. A 580-m area along the north shore of the lake will be protected with a wave dampening fence to curtail shoreline erosion. Data will be collected to determine the effectiveness of the fencing. If this fencing does not succeed, it is assumed that East Prong and this lake will become one water body. This work will be funded by the Louisiana Geological Society. EAST COVE MANAGEMENT CALENDAR From 1 January to 15 February 1989, Sabine Refuge personnel will burn the entire Sabine NWR East Cove unit. To accomplish this, a helicopter will drop ping pong balls injected with potassium permanganate and ethylene glycol on all vegetative communities. Burning will be undertaken to encourage the growth of leafy and Olney threesquare grasses and to remove litter. 315 Table 4. Survival and tillering success of January bunch-planted oystergrass, East Cove marsh unit, Sabine NWR, May 1988. Distance planted Number Actual Percent Sprigs per Site (m) planted survival survival bunch (x) Sandbar 41.2 27 27 100.0 2.3 Wiregrass root mat 212.0 139 126 90.6 0.6 The establishment of the threesquare grasses will increase root species diversity and litter reduction may promote sheet flow and the removal of surface soil salts. Water salinities less than 8.0 ppt and 1.3 cm standing water are optimum for the burn. If standing water is not present, the burn will still occur unless there is a drought. The area will not be burned if water salinities are greater than or equal to 8.0 ppt. Weirs will be managed for draw-down, abnormal weather conditions, and organism ingress from 15 February to 15 July 1989. Abnormal weather conditions to be dealt with are drought and abnormally high precipitation rates. During periods of drought, waters will be allowed to flow into the system to prevent vegetative salt burns. In case of abnormal rainfall, weirs will be opened to release excess water. The boat bay will be opened for five days sometime in March or April to allow ingress of brown shrimp and for a second five days in June to allow ingress of white shrimp. Actual dates will be determined by using historical data on post-larva movement collected on Sabine Refuge (March-April: brown shrimp and June: white shrimp), lunar tide data (new and full moon tides), water temperatures (< 21 °C, no post-larva movement, 26 °C = optimum post- larva movement), salinity (8-16 ppt), and Louisiana Department Wildlife and Fisheries monitoring of post-larva shrimp ingress in Calcasieu Lake. From 16 July 1989 to January 1990, weir openings will be managed as previously stated in the weir management section. However, the boat bay will be closed to facilitate closed sportfishing season during open duck season and to retain fresh water from winter rains. Generally, the controlling factor on water flow will be determined by the 5-ppt isohaline line. Once salinites reach 5 ppt at the 5-ppt isohaline line, the variable crest structures will be closed one at a time then the boat bay will be closed last. Order of closure will be determined by water salinities flowing into each weir and the corresponding 5-ppt isohaline line in that respective area. From 10 January 1990 to 10 January 1991, weir structures will be managed as previously stated in the weir management section. Vegetation stands that were not burned the previous year will be burned. To facilitate estuarine organism ingress, one more flap gate at Grand Bayou will be raised during peak post-larva movement (whenever these periods occur for brown and white shrimp). Adaptations to natural parameters and needs pertaining to vegetation will be addressed in subsequent years. A yearly report will be compiled and presented to the Cameron/Creole Watershed advisory board, and the advisory board will make recommendations for future management. 316 CONCLUSION Salinities and physical action of water are critical factors for marsh plant survival and diversity. These factors influence soil stability which in turn may lead to an increase or decrease in marsh productivity (i.e., waterfowl, estuarine species, furbearers, alligators, and cattle). To encourage vegetation diversity and production, waterflow and exchange from Calcasieu Lake will be kept at a minimum for a maximum amount of time. To encourage estuarine organism diversity and production, this same waterflow will be maximized for a minimum, opportune time frame. This requires intensive weir management to optimize water flow capabilities. The most difficult and time consuming aspect of managing this area will be adjusting management schemes to fit the parameters of nature. Management of this area must have flexible long term goals with the idea of holistic management. One objective reached may mean the partial loss of another. Management at the present time is projected toward the next 20 years, but should probably be directed well into the 21st century. Management schemes must maintain the horizon in sight and yet not be myopic in thought. Management Implications 1. Lack of tidal flow may cause a decrease in productivity of migrating estuarine organisms, loss of sediment loads for plant nutrition and production, and salt burns on marsh vegetation. 2. Loss of vegetation will increase marsh soil erosion, and fetch will continue to abet marsh soil erosion. 3. Lack of freshwater introduction and coinciding evapotranspiration rates may allow soil salinities to remain at toxic levels. Future Research Evapotranspiration, salinity, tidal data, and marsh soil redox potentials will be collected and analyzed by Sabine NWR Wildlife personnel. Continuing research in streamside sedimentation rate will be continued by D.R. Cahoon, R.D. DeLaune, and R.M. Knaus. If funding permits, J.M. Hill and S.C. Leibowitz will continue to monitor land loss and gain trends. Vegetative censuses will be conducted by the Soil Conservation Service and Sabine NWR personnel. In order to manage the weirs for optimum waterflow capabilities, the hydrology of the East Cove marsh with respect to weir application needs to be determined. ACKNOWLEDGEMENTS This marsh system could continue to degrade if prevalent land loss processes are allowed to continue unchecked. Therefore, I appreciate and recognize those individuals and organizations whose efforts have prevailed since 1961 in the implementation of the Cameron/Creole Watershed Management Plan. I would also like to thank Rita Walther for her editing assistance, Sabine Refuge personnel for their aid and assistance, and the resource by which I gain my energy, the marsh. 317 LITERATURE CITED Cahoon D.R., R.D. DeLaune, and R.M. Knaus. 1988. Marsh accretion, mineral sediment deposition, and organic matter accumulation along man-made canals and waterways:introduction. Pages 233-243 in R.E. Turner and D.R. Cahoon, eds. Causes of wetland loss in the coastal central Gulf of Mexico. Vol. 2, Technical narrative. Minerals Management Service, New Orleans, LA. 400 pp. Chabreck, R.H. 1972. Vegetation, water, and soil characteristics of the Louisiana coastal region. Louisiana Agricultural Experiment Station Bulletin. 664 pp. Herke, W.H., B.D. Rogers, and E.E. Knudsen. 1987. Investigation of a weir-design alternative for coastal fisheries benefits. Louisiana Cooperative Fish and Wildlife Research Unit. 98 pp. Leibowitz, S.C., and J.M. Hill. 1988. Spatial analysis of Louisiana coastal land loss. Pages 331- 355 in R.E. Turner and D.R. Cahoon, eds. Causes of wetland loss in the coastal central Gulf of Mexico. Vol. 2. Technical narrative. Minerals Management Service, New Orleans, LA. 400 pp. Soil Conservation Service. 1977. Gulf Coast wetlands handbook. U.S. Department of Agriculture Technical Publication. 126 pp. 318 AN EVALUATION OF THE TENNECO LATERRE MITIGATION BANK MANAGEMENT PLAN Richard Simmering Billy Craft USDA Soil Conservation Service 3737 Government Street Alexandria, LA 71302 John Woodard Tenneco LaTerre P. O. Box 208 Houma, LA 70361 Darryl Clark Coastal Management Division Louisiana Department of Natural Resources P. O. Box 44887 Baton Rouge, LA 70804-9386 ABSTRACT The 2,828 ha Tenneco LaTerre mitigation bank plan consists of brackish, intermediate, and fresh marshes, bottomland hardwood forests, and wax myrtle scrub-shrub habitat. The plan was implemented in 1985 and has been monitored by an interagency team in addition to the U.S. Soil Conservation Service and Coastal Management Division of the Louisiana Department of Natural Resources. The planned structural components consist of three wooden fixed-crest weirs, one double variable-crested flap-gated weir, spoil bank maintenance, a low level levee, and gaps in existing pipeline canal spoil banks for freshwater introduction. The plan goal is marsh restoration through a reduction of abnormal tidal flows and water level drawdowns. The plan has been monitored by transect at 22 stations for percentage of vegetative cover. Tenneco LaTerre has recorded water levels at one station and salinity at 1 1 stations at a frequency of every 4-5 days since implementation. Marsh:water ratios, trapping and hunting data, and vegetative prevalence indexes were also recorded. The results of the 1986 monitoring indicated that the average salinities rose 0.6 ppt and water levels rose 0.06 cm inside the managed area compared to those values measured outside. Turbidity was reduced and submerged aquatic vegetation increased in abundance and diversity. The 1987 evaluation results also indicated that average water levels were slightly higher inside (mean=24.84 cm) than outside (mean=22.15 cm) the plan area. Stations outside the plan area showed greater water fluctuations (10.63 cm versus 4.83 cm). Salinities averaged 21% higher outside (1.22 ppt) compared to values recorded inside (1.01 ppt). Average salinities were 1.0 ppt in 1987 compared to 4.2 ppt in 1986 at the same station. 319 Revegetation of open water areas appears to be occurring in the southeast corner of the plan area. Turbidity has decreased and submerged aquatic vegetation has increased in the open water areas. More waterfowi (10%; 2,295 versus 2,562) and alligators (3.8%; 81 versus 78) were recorded in 1987 compared to 1986. In summary, the management area may have produced some positive results in the 2 years since implementation: (1) increased abundance and diversity of submerged aquatic vegetation, (2) revegetation of small areas surrounding islands in the southeast portion of the plan, (3) more stabilized water levels and turbidity inside the plan area than outside, and (4) a slight increase in waterfowl and alligator abundance. INTRODUCTION The area included in the Tenneco LaTerre (TLT) mitigation bank is about 2,828 ha. It is located in Terrebonne Parish, LA, and is within hydrologic unit 5. The entire area was a fresh marsh as shown in the 1963 Terrebonne Parish Soil Survey. In 1953, the marsh in this area was vegetated primarily by Paille fine (Panicum hemitomon). As of 1982, about 1,333 ha had been converted to intermediate/brackish marsh and large open water areas-unproductive from a wildlife standpoint (Figure 1). Significant deterioration in the area began around 1962 with the opening of the Houma Navigation Canal which provides a direct avenue of saltwater to the area via the Falgout Canal. In 1984, Hurricane Hilda hit the area, bringing in saltwater. The Pipeline Canal, with solid levees on both sides, was constructed east to west across the property, cutting off all freshwater recharge from the Marmande Canal. Other oil or gas exploration canals excavated into the area aggravated the situation by providing additional corridors for saltwater intrusion. All of these factors plus subsidence have had a detrimental effect on the area. An attempt is being made to stop and reverse the deterioration of this marsh. A marsh management plan was developed by TLT with the guidance and approval of the Soil Conservation Service (SCS), the U.S. Fish and Wildlife Service (USFWS), U.S. National Marine Fisheries Service (USNMF), and the Louisiana Department of Natural Resources (DNR). A Memorandum of Agreement (MOA) was implemented between TLT and the above agencies to establish a mitigation bank of fish and wildlife habitat units gained, resulting from habitat improvements in the management area. These habitat units could then be used to mitigate habitat units lost because of oil and/or gas exploration projects conducted by Tenneco and other companies. The MOA states that the area will be intensively managed for at least 25 years by installing, operating, and maintaining a series of water control structures and levees for the purpose of increasing freshwater and sediment inflow, improving water circulation, and reducing saltwater intrusion. More specifically, the objectives of the plan are to enhance the area for wildlife, waterfowl, and marine organisms and control erosion by doing the following: 1. Control saltwater intrusion into fresh and intermediate marshes. 2. Stabilize water levels within the management area. 320 ml - 'ml . i. i. .-.*!•! Figure 1. Status of the TLT mitigation bank area in 1982. 3. Increase herbaceous vegetation in and around open water. 4. Aid in ingress and egress of marine organisms. 5. Stop the conversion of vegetated marsh to open water. 6. Manage the vegetation for furbearing mammals, alligators, and waterfowl. Structural measures have been installed to reduce the salinity and stabilize the water levels within the bank area. Both the quantity and quality of the vegetation should improve as a result of better water management (Figure 2). Two Fixed-crest weirs have been installed along the Marmande Canal, and one weir was placed along the Minors Canal to allow additional freshwater to enter on the north end of the mitigation area. Breaks have been made in the spoil bank of the pipeline canal, which extends east-west across the mitigation area, to allow freshwater to flow into the intermediate and brackish marshes to the south. The Frxed-crest weir in Minors Canal along the western boundary of the area will permit additional freshwater to enter the segment of the mitigation area which is experiencing rapid marsh loss from saltwater intrusion. To further minimize saltwater intrusion, an existing weir was replaced in the southeastern corner of the mitigation area. This variable -crest weir allows drawdowns or ponding of freshwater, 321 *.••• P.C. Figure 2. Structural measures installed in the TLT mitigation bank area. depending on prevailing hydrological conditions and desired management results. A flap gate has also been installed on the weir, which can be closed to prevent highly saline water from entering the management area. This weir has been designed to insure the ingress and egress of marine organisms. During the intensive management period, TLT has agreed to construct the additional weir if a majority of the cooperating agencies determine the need for one along the southern end of the mitigation area. METHODS AND MATERIALS To evaluate the effectiveness of the management plan, a monitoring program is being conducted to gather and assimilate information inside and outside of the area concerning vegetative community changes, water salinity, tide fluctuations, change occurring to the land:water ratios, and trapping and hunting harvests. Historical Change Assessment A historical change assessment of the land:water ratio has been prepared to show the cumulative impacts over time of natural subsidence, erosion, compaction, and saltwater intrusion. Five sets of aerial photographs (1953, 1971, 1980, 1983, and 1985) were used for comparison. The area of land and water was determined by planimetry for each of the 5 years. 322 Tide Level Data Erratic water level fluctuations contribute to increased marsh erosion rates and reduce the ability of vegetation to become re-established in open water areas. Tide levels both inside and outside of the management area have been monitored by TLT at weir 1 to assess if tide fluctuations are being reduced inside of the management area. Elevations were frequently monitored (86 times from 25 March 1986 through 26 November 1988, and 82 times from 1 December 1986 through 28 November 1987). Salinity Levels Salinity readings have been collected by TLT on a periodic basis at 12 sites from 11 November 1985 through 28 November 1987. See Figures 3 and 4 for the location of the sites monitored in 1986 and 1987. Vegetative Changes In 1988, 22 60-m vegetative transects were established so that plant communities could be monitored yearly. These transects are located throughout the fresh, intermediate, and brackish marsh, and in open water (Figure 5). Each transect is divided into 10 5-m increments. All vegetative species are identified annually within a 1-m radius at each increment. A visual estimate of species composition is also made at each transect site location. The estimate gives a percentage of each species in relation to all other plant species in the community. It is important to know if the management plan is increasing or decreasing the abundance of plant species at each transect site, and if the plant communities are changing to species favoring a fresh, intermediate, brackish, or strong brackish marsh. An evaluation system has been developed to show Figure 3. Sites monitored for salinity in 1986. 323 S«IMty SU«« 1987 Figure 4. Sites monitored for salinity in 1987 Figure 5. Vegetative transect sites in the TLT mitigation bank area. 324 if this is occurring. Vegetative data obtained from the transects are used in this evaluation. A numerical prevalence index (P.I.) can be used to assess changes that occur to the vegetative community. To find the P.I., an indicator value is assigned to each plant species recorded for a particular site based on its tolerance to salinity (Table 1). For example, Distichlis spicata prefers an average salinity of 13.0 ppt for optimum growth; therefore, this species will be assigned an indicator value of 1. Table 1. Indicator values with their corresponding salinity and marsh types. Indicator value Average salinity (ppt) Marsh type 1 2 3 4 >8.1 Strong brackish 8.0 Brackish 3.3 Intermediate <3.2 Fresh Each plant species found on a transect is assigned an indicator value. The values of all plants recorded are added and then divided by the total amount of occurrence to find the average P.I. of a site. Hunting and Trapping The number of waterfowl, deer, furbearers, and alligators harvested from the management area are monitored by TLT. The area is leased to a limited number of individuals for hunting and trapping. Records are kept on the amount of wildlife removed from the management area. RESULTS Changes in the land:water ratio for these five years of data are displayed in Table 2. Table 2. Historical change in ratio of land to open water (in hectares) at Tenneco-LaTerre mitigation area, Terrebonne Parish, LA. Year Land Water 1953 2,833 6 1971 2,319 520 1980 1,966 874 1983 1,913 967 1985 1,728 1,111 1986a 1,728 1,111 a1986 photo showed no distinguishable difference from 1985. 325 Water level data for the time periods monitored are presented in Table 3. Table 3. Tide level elevations at weir 1 in centimeters. Average marsh elevation is 30.48 cm above MSL. Location and time 1986 1987 Average water elevation outside of area 26.88 22.15 Average water elevation inside of area 26.94 24.64 Average fluctuation of water level between monitoring dates outside of area 6.52 10.63 Average fluctuation of water level between monitoring dates inside of area 3.47 4.63 Salinity The averages and ranges of salinity readings are presented in Table 4. Table 4. Average salinity (ppt) and range (in parentheses) at Stations 1-12 during 1986 and 1987a. Weir 1986 1987 1 - Inside of area 4.2 (0-13) 1.0 (0-9) - Outside of area 3.6 (0-11) 1.2 (0-11) 2 - Inside of area 0.9 (0-4) 0 (0) - Outside of area 0.8 (0-3) 0 (0) 3 - Inside of area 1.2 (0-3) 0 (0) - Outside of area 1.1 (0-3) 0 (0) 4 5.2 (5-10) 0.1 (0-2) 5 5.0 (3-10) 0 (0-1) 6 4.3 (0.5-7) 0.1 (0-2) 7 0.6 (0-11) 0.8 (0-8) 8 4.3 (3-8) 0.3 (0-6) 9 3.8 (2-7) 0 (0-2) 10 - Inside of area 3.5 (1-7) 0 (0-2) - Outside of area 3.8 (1-8) (~)b 11 - (Lake DeCade) 4.4 (1.6-7) (-)c 12 - (Falgout Canal) 6.8 (3-14) (-)d a1986 data was collected from 11/11/85 - 11/28/86. 1987 date was collected from 12/1/88 - 11/28/87. bNo readings were taken in the canal at this site in 1987. cStation No. 11 in Lake DeCade was relocated to inside the management area in 1987. dNo readings were taken at Station No. 12 in 1987. 326 Vegetation The P.I.'s for all sites monitored in 1987 except open water are displayed in Table 5. The P.I. values indicate that the vegetative communities are brackish-intermediate to intermediate-fresh marsh. Table 5. Summary of prevalence index values for monitored sites in October, 1987. Transect (Site) Nos. Prevalence Index 1 2 3 4 13 14 15 16 17 18 19 20 21 22 23 29 2.89 2.92 2.47 2.60 3.40 3.48 3.29 3.58 3.34 3.47 3.65 3.49 3.73 3.59 3.65 3.53 Mean Prevalence Index Range in Prevalence Index 3.32 2.47-3.73 Hunting and Trapping Results of the 1985-86, 1986-87, and 1987-88 hunting and trapping seasons are presented in Table 6. DISCUSSION Tide Level Fluctuations Monitoring data indicate the structural measures have reduced water-level fluctuations by about 100% within the mitigation bank. This trend is expected to continue and should have a positive effect on the reintroduction of vegetation around the edges of existing marsh, on mud flats, and in open-water areas. 327 Table 6. Trapping and hunting report summary. Species 1985-86 1986-87 1987-888 Trapping Muskrat Mink Nutria Raccoon Otter Duck Whitetailed Deer Alligator 165 150 23 28 1,013 1,010 38 31 6 8 Hunting 2,295 2,562 13 6 61 78 BTrapping harvest data for the 1987-88 season not available. Salinity Salinity levels were variable in 1986 and 1987. In 1988, average salinities were higher at many of the sites inside the area compared to the salinity outside of weir 1 in 1988. In 1987, the average salinity was slightly higher outside weir 1 than all of the sites inside the area. The 1988 increase was caused by a lack of rainfall to provide freshwater, saltwater being pushed into the area by Hurricane Juan and remaining trapped there, or other factors. Based on limited data, it is too early to tell if the structural measures are having a positive effect on salinity levels, but salinities have decreased significantly from 1982 levels. Vegetation Impacts to the vegetative community resulting from the management plan are expected to occur slowly. The results obtained from the monitoring program are encouraging, but not enough information has been collected to definitely state that the plan has stopped the erosion process and is adding to or improving the quality of the existing marsh. However, some positive indications that the plan is working include the following: 1. Plants such as Bacopa and Eleocharis spp. are invading small open water areas. These plants will provide a substrate on which other, more dominant species can grow. 2. Most open water areas now support submerged vegetation such as Myriophyllum spp., Ceratophyllum, Najas spp., and Ruppia. 3. Species composition is becoming more diverse in some locations. Eleocharis cellulosa, Eleocharis flavescens and Bacopa are becoming much more predominant in the plant community. 328 Hunting and Trapping The main objectives of this management plan are to stop the expansion of open water areas, to improve the quality of vegetative communities within the remaining marsh, and to promote the growth of beneficial submergent vegetation in open water. This in turn should increase the wildlife and fisheries production. Harvest data should reflect these changes. No definite trends have been established which indicate that management is having a positive or negative effect on the amount of wildlife harvested. The data collected show that the total number of animals harvested by both trapping and hunting were about the same for the 2 years studied. More data need to be collected. Conclusion Impacts to the vegetative communities within the mitigation bank are expected to occur slowly. The results obtained from the monitoring program are encouraging but the limited amount of information collected so far is not enough to draw any definite conclusions. Further study of the area is needed. 329 GEOGRAPHIC INFORMATION SYSTEM APPLICATIONS FOR MARSH MANAGEMENT PLANS Pierre Bourgeois, John Barras, Bo Blackmon, Darryl Clark Louisiana Department of Natural Resources Coastal Management Division P.O. Box 44487 Baton Rouge, LA 70804 ABSTRACT A Geographic Information System's (GIS) main function is to efficiently update, retrieve, analyze, and output spatially referenced data in tabular or graphic form. The Coastal Management Division (CMD) manages an interactive software package, consisting of the Analytical Mapping System (AMS) Map Overlay Statistical System (MOSS), and Earth Resources Data Analysis System (ERDAS) on a Data General MV/10000 computer. Marsh management plans have been digitized into CMD's computer system through the AMS package. From the AMS system, the plans are exported to the MOSS system, which is primarily used for data manipulation and analysis. MOSS workups can be done on individual marsh management plans using the U.S. Fish and Wildlife Service habitat and acreage data from 1956 and 1978. In addition, the marsh management plans can be exported to ERDAS where the 1985 classified Landsat Thematic Mapper information can be extracted for individual marsh management plans. Our study concentrates on a marsh management plan in the eastern portion of Cameron Parish, LA INTRODUCTION The Coastal Management Division (CMD) of the Louisiana Department of Natural Resources (DNR) is one of several State and Federal agencies responsible for managing the State's coastal wetlands. CMD maintains an extensive collection of information sources consisting of maps, aerial photographs, satellite imagery, and permit records for the purpose of assessing the impact of proposed activities within Louisiana's coastal zone. CMD uses a geographic information system (GIS), Mapping Overlay Statistical System (MOSS), and image processing system (IPS), Earth Resources Data Analysis System (ERDAS), for project impact analysis within the coastal zone. MOSS is a public-domain, vector-based GIS software package developed by the USFWS for natural resource and land cover evaluation. ERDAS is a vendor-developed, cell-based image processing system which is primarily used by CMD for classification of Landsat Thematic Mapper (TM) imagery but can also perform GIS functions. MOSS and ERDAS together form CMD's interactive system and are operated on a Data General MV/1000 minicomputer. Most analyses in MOSS use the 1956 and 1978 digital ecological characterization (habitat) maps created for the U.S. Fish and Wildlife Service (USFWS) as overlays for 1:24,000 U.S. Geological Survey (USGS) quadrangle maps. These maps subdivide each quadrangle map into land cover and land use polygons ranging in size from an acre to several thousand acres. A wetland classification scheme (Cowardin et al. 1979) based on a hierarchal structure of 1) system and subsystem, 2) class and subclass, and 3) modifiers such as, water regime, water chemistry, and soil was used to identify approximately 130 habitat types (Wicker 1981). The habitat maps were derived from 1956 and 330 1978 aerial photographic coverage of Louisiana's coastal zone. Habitat coverage in 1983 is available for a few quadrangle maps in the deltaic plain. CMD uses 1984 and 1986 classified Landsat TM coverage of the coastal zone as another primary data base. The 1984 data set covers the entire coastal zone while the 1986 set provides partial coverage of the deltaic plain. The classification categories are based on land cover types and constitute a Level 1 land cover scheme (Braud and Streiffer 1987). CMD primarily uses the GIS to provide information to coastal resource analysts to aid in the review of proposed activities within Louisiana's coastal zone (Howey and Blackmon 1987). Coordinates for a proposed activity are entered into a program which performs an automated MOSS analysis for 1956 and 1978 habitat data on the site requiring a minimum of user interaction (Streiffer and Braud 1987). The program delivers a standard GIS analysis package which provides statistical and map output for the site. In addition to the automated permit analysis system, CMD's GIS is used for special projects requested by CMD personnel or by outside agencies. Currently, CMD is developing a wetland management plan data base. The primary objective is to produce land loss statistics and habitat change over time within the wetland management plan boundaries. METHODOLOGY The wetland management data base consists of 130 plans ranging in size from a few acres to several thousand acres. An attribute scheme was developed to encode point, line, and area data for each plan into the data base. Point data represents water control structures, line data represents various types of plan boundaries, and area data represents the acreage values of the plan. Once all the plans have been incorporated into the data base, individual habitat change analysis will be performed on each plan. The analysis will primarily involve comparing 1956, 1978, and 1983 (if available) habitat data as well as 1984 and 1986 (if available) classified Landsat TM imagery to statistically and spatially assess habitat change over time within each plan. This can provide a valuable tool to wetland managers. The Little Pecan Lake wetland management plan was chosen as an example to demonstrate some of the analysis techniques that can be applied to each wetland management plan. The methodology developed to analyze this plan can be applied to the other plans in the data base. The 2,793-ha study area is located in eastern Cameron Parish. The following section will outline the incorporation of the Little Pecan Lake management plan into CMD's data base and its subsequent analysis in MOSS and ERDAS. Incorporation of the Little Pecan Lake Plan into CMD's GIS The permit record for the Little Pecan Lake plan was obtained from CMD's permit files to determine the location, areal extent, and structural components of the plan. Plan boundaries and water control structures were then manually transcribed onto the Catfish Lake 7.5-minute USGS topographic map. The plan was then digitized from the map using the Analytical Mapping System (AMS), the data entry and encoding software package used by MOSS. After digitizing, the plan was verified in the AMS, using the VERIFICATION subroutine, and then stored in the AMS data base. The plan was prepared for transfer to MOSS using the EXPORT routine. EXPORT allows the user to select the map projection and ellipsoid parameters for the digitized map. The Little Pecan Lake plan was exported as a Universal Transverse Mercator (UTM) projection using the Clarke 1966 ellipsoid. The ADD routine in MOSS was used to transfer the plan from the AMS data base to a specified user directory in MOSS. 331 Analysis of the Little Pecan Lake Wetland Management Plan in MOSS MOSS was designed to allow users to enter, retrieve, analyze, and display maps and other spatial data stored in the system. MOSS uses two data formats: vector and cellular. CMD uses MOSS primarily for its vector capabilities; however, a subsystem, the Map Analysis Package (MAPS), can be used to manipulate cellular data. The following MOSS products were created for the example area: a. VICINITY MAP - A vicinity map was created to allow the reader to be familiar with the study area (Figure 1). b. STUDY AREA MAP - A study area map was created based on the marsh management plan boundaries (Figure 2). c. OVERLAYS - The management area polygon can be overlaid with the 1956 and 1978 habitat maps (Figures 3 and 4). The management area can be overlaid with the permit data (Figure 5). In addition, the management area can be overlaid with the Louisiana National Heritage Program (LNHP) data (Figure 6). d. SPECIFIC HABITAT INQUIRIES - Any habitat type can be singled out for analysis. In this instance we are interested in total water area for 1956 and 1978. Figures 7 and 8 represent the 1956 and 1978 water maps for the management area. Habitat review could be done for the canals present in 1956 and 1978 (Figures 9 and 10). Erdas Analysis of the Little Pecan Lake Wetland Management Plan CMD uses ERDAS to obtain habitat change statistics for individual wetland management plans within its coastal data base. MAPS (MOSS cellular format) can also be used to obtain habitat change data for plans but is not as efficient or as user friendly as ERDAS. In addition to providing change statistics, ERDAS is also used for specialized analysis procedures such as the compilation of land loss density maps, and land and water interface complexity maps. Analysis of the Little Pecan Lake wetland management plan in ERDAS first requires that the 1956 and 1978 habitat plan overlays be converted from a vector format to a cellular format. The cell size used was 10 m2. As stated previously, MOSS is a vector-based GIS. A vectory system identifies each polygon as a unique area. For example, individual marsh ponds on the digital habitat maps are represented as separate polygons in MOSS. The ponds may be of the same type but will have different areas. ERDAS, a cell-based system, will divide a map into a series of 10-m2 cells, each the same size as its neighbor. In this case, a specific value will be assigned to all cells in the map representing freshwater ponds. The advantage in using cell maps is that change statistics are much easier and faster to obtain. The main disadvantage is that maps produced using a cell format are not as appealing to the eye as those produced using a vector format. Area figures for the cell maps may differ from those produced by vector maps but the difference is negligible. After conversion to a cell format was completed, the plan habitat overlays were changed to an ERDAS-readable format for analysis. Development of the Habitat Change Maps. The first step in the land loss analysis of the management plan was to simplify the original wetland classifications to a land cover classification system consisting of 16 habitat categories using the RECODE program in ERDAS. The simplified 332 VICINITY MAP LITTLE PECAN LAKE MM PLAN Figure 1. Figure 2. 333 LITTLE PECAN LAKE MARSH MANAGEMENT PROJECT cc • PC a v»s o vc . FC ^5>N y * \ * / c> S \ ^v . \ / \ / J LN PR TR 1 ! Figure 3. LITTLE PECAN LAKE 1978 HABITAT DATA Figure 4. 334 LITTLE PECAN LAKE MARSH MANAGEMENT PROJECT PERMIT DATA OVERLAY \gwiii \ / -£r»"»» J3C""* 1 Figure 5. LITTLE PECAN LAKE MARSH MANAGEMENT PROJECT NATURE CONSERVANCY OVERLAY Figure 6. 335 LITTLE PECAN LAKE MARSH MANAGEMENT PROJECT 1956 WATER MAP Figure 7. LITTLE PECAN LAKE MARSH MANAGEMENT PROJECT 1978 WATER MAP Figure 8. 336 LITTLE PECAN LAKE MARSH MANAGEMENT PROJECT 1956 CANAL MAP Figure 9. LITTLE PECAN LAKE MARSH MANAGEMENT PROJECT 1978 CANAL MAP \ y Figure 10. 337 habitat codes include background, natural water, artificial water, fresh marsh, intermediate marsh, brackish marsh, saline marsh, forest, swamp, shrub/scrub, shrub/scrub (spoil), agriculture/pasture, developed, aquatic vegetation, inert, and beach. The land change statistics for the plan were obtained by using MATRIX to compare the 1956 and 1978 aggregated habitat maps. The habitat classes for 1956 and 1978 were reeoded to produce maps consisting of two subjects-land and water-for each year. It is important to note that CMD considers aquatic vegetation a water class when deriving land loss statistics. MATRIX compared the 1956 and 1978 land and water maps to produce a change map consisting of four classes: 1) water 1956 to water 1978, 2) land 1956 to water 1978, 3) water 1956 to land 1978, and 4) land 1956 to land 1978. MATRIX compared each cell in the 1956 map with its corresponding cell in the 1978 map and assigned one of the four change classes to that cell. The 1956/1978 land and water change map for the Little Pecan Plan (Figure 11) shows that the area had 9.07% land loss and 0.70% land gain. The MATRIX program not only calculates numerical change values but also produces a map showing where land loss has occurred. Plan managers can use a change map to identify problem areas with high land loss rates or to differentiate between various types of land loss occurring within a plan's boundaries. For example, the Little Pecan Plan change map shows shoreline erosion on Little Pecan Lake, areas of interior marsh deterioration in the southern portion of the plan, and the addition of oil field location canals in the eastern half of the plan. Other change combinations of 1956 and 1978 habitat classes can also be obtained using MATRIX. Vegetation change maps can be produced showing changes in marsh type, forest, or swamp over the 22-year period. Care should be used when interpreting change statistics as the habitat data reflects conditions existing when the aerial photograph was taken. Meteorological conditions or management practices could change water levels within a plan, causing a misunderstanding of land loss or gain data. Land Loss Density Maps. ERDAS can also be used to generate land loss density maps. A land loss density map is used to locate areas that have land loss in excess of a user-specified base value. The land loss density map for the Little Pecan Wetland Management Plan (Figure 12) shows all areas of land loss that are greater than 608 m2 acres. The land loss density map for the plan was created by scanning a land loss map of the plan with a roving window composed of 9 cells (30x30 m). The central cell of the window is sequentially centered on each cell of the land loss map. The cell is then assigned a value based on the number of land loss cells occurring within the window. For example, if 3 cells are counted within the window, the central pixel for the density map is assigned a land loss density value of 3 which equates to 300 m2. The land loss density for a full window equals 892 m2. By using filtering techniques to eliminate land loss values below a certain size, a map can be produced which identified problem areas on management plans. Land gain maps can also be created using the same method. Land and Water Interface Density Maps. A land and water interface density map is produced using techniques similar to those used for creating the land loss density map. A roving cell window is used to scan shorelines on the 1956 and 1978 plan maps. Shorelines which have the greatest complexity are assigned a higher density value than simple shorelines. An example of a complex shoreline would be the southwestern quadrant of the Little Pecan Wetland Management Plan. Many small ponds and natural channel meanders occur there, increasing the total shoreline area. ERDAS assigns a graduated color scale to these density values. The purpose for creating the 1956 and 1978 land and water interface density maps is to provide plan managers with a visual means of identifying areas of complex shorelines within plans. These sights may be desirable habitats for certain species. ERDAS can provide a visual representation of shoreline complexity within plans 338 LPLA5678LW.GIS SCALE 1 : 40000 / 1 The variable name is : 56/78 LAND / WATER CHANGE MAP FOR LITTLE UALUE CLASS NAME NO. OF POINTS % NO . OF ACRES WATER / WATER LAND / WATER WATER / LAND LAND / LAND 2262 1 . 8. 1 1 25315. 9.07 1961 . . 70 229076. 82. 1 1 558.977 625.547 48.457 5660.590 TOTALS: 278973. 6893.570 Points, totals and percentages based on NON-ZERO data values in the ENTIRE input image Figure 11. 339 SCALE = 1 : 40000 %-Wl t — w TWwBf ^iiMrawp 1 Jlii 2 The variable name is : 56/78 LAND LOSS DENSITY AND BOUND. MAP FOR UALUE CLASS NAME NO. OF POINTS X NO. OF ACRES 1 1978 LAND / UJATER BOUNDARY 2 1956/1978 LAND LOSS AREAS WITH 15813. 21398. 42. 50 57.50 390. 748 528. 756 TOTALS: 3721 1 919. 504 Points, totals and percentages based on NON-ZERO data values in the ENTIRE input image Figure 12. 340 but it cannot be used to calculate shoreline lengths, bodies for plans can be calculated using MOSS. The actual shoreline perimeters of water Habitat Diversity Maps. Habitat diversity maps for 1956 and 1978 are generated in ERDAS using the same techniques that produce the land/water interface density maps. The habitat diversity map is a visual representation of habitat complexity. A 15x15 cell (150x150 m) roving window is used to scan each cell within the plan. A value is assigned to the central cell based on the number of different types of habitat cells occurring within the window as it moves through the map. The greater the number of habitat types found within the window, the higher the habitat diversity for that location. ERDAS then creates a map showing areas of high and low habitat diversity for the plan. This type of map may be useful to plan managers for locating areas having the highest habitat complexity. Classified Landsat Thematic Coverage of the Little Pecan Plan Wetland Management Plan. As mentioned previously, CMD has complete 1984 and partial 1986 classified Landsat Thematic Mapper (TM) coverage of the coastal zone. This coverage was produced in-house by Decision Associates, Inc., and by CMD technical personnel using ERDAS. The classified satellite data is in cell form, has a resolution of 25 m, and consists of 14 classification categories. The 14 classification categories include out (background), water, broken marsh, marsh, forest, swamp, shrub/scrub, ag/pasture, developed, inert, beach, clouds, floating vegetation, mixed vegetation, and unclassified (unknown). Classified Landsat TM imagery for wetland management plans can easily be obtained from the 1984 or the 1986 (if available) coverage. Table 1 shows area statistics for 1984 classified Landsat Table 1. Habitat area statistics for the Little Pecan Lake Plan area. Totals and percentages are based on non-zero points. Value Points Acres % Description 0 4865 751.379 .00% Out 1 4955 765.279 11.00% Water 2 5016 774.701 11.13% Broken Marsh 3 33255 5136.098 73.81% Marsh 4 245 37.839 .54% Forest 5 308 47.569 .68% Swamp 6 747 115.371 1.66% Shrub/Scrub 7 527 81.393 1.17% Agriculture/Pasture 8 1 .154 .00% Developed 9 1 .154 .00% Inert 10 0 .000 .00% Beach 11 0 .000 .00% Clouds 12 0 .000 .00% Floating Vegetation 13 0 .000 .00% Unclassified 49920 7709.937 341 TM coverage of the Little Pecan Lake Plan. The satellite imagery for a plan can be analyzed with the same techniques used for analyzing the habitat data. The classified satellite coverage is not as detailed as the habitat maps but can provide recent land cover conditions and change statistics for plans. The habitat coverage can be compared to the classified TM coverage but problems exist in generating accurate comparisons. The main cause of error is the inability to compare the TM broken marsh class to the 1978 habitat data. Broken marsh is a category representing a distressed marsh characterized by numerous small islands of marsh interlaced with a network of small ponds and channels. Broken marsh is a useful class since it can be used to identify areas of marsh which are in the initial stages of deterioration. This is a mixed land and water class and constitutes a portion of the total land and water areas of a plan. The habitat data has no analog for broken marsh. Habitat data aggregated to land and water classes must be compared to land, water, and broken marsh categories in the classified TM data. CMD has not yet developed an accurate means of assigning the proper percentages of land and water areas within the broken marsh class to the total land and water area occurring at a specific location. This results in an inability to accurately compare the 1984 TM coverage to the 1978 habitat data. CONCLUSIONS The purpose for designing the wetland management data base is to provide a sound foundation for future management decisions concerning individual plans. CMD's GIS/IPS can provide the following information for each plan: 1956 and 1978 habitat data; 1983 habitat data (if available); 1984 Landsat TM data; and 1986 Landsat TM data (if available). In summary: 1) Information provided by CMD's GIS/IPS is only a tool, and results should be interpreted by professional wetland managers who are familiar with the history of each plan. 2) The data base can easily be updated to meet the user's needs. 3) The wetland management contract from Minerals Management Service, for which the Louisiana Geological Survey and DNR are providing data, is a 2-year project. Deliverables from the CMD GIS/IPS will include: A. Coastwide habitat maps B. Habitat change maps from 1956 to 1978 C. Habitat maps and habitat change maps for large hydrologic basins within the coastal zone D. Site analyses, similar to the Little Pecan Lake analysis, for 24 plans. LITERATURE CITED Braud, D.H., and H.R. Streiffer. 1987. Landsat Thematic Mapper data analysis for coastal Louisiana. Final Report. Louisiana Department of Natural Resources, Coastal Management Division, Baton Rouge, LA. Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deep-water habitats of the United States. U.S. Fish Wildl. Serv. Biol. Serv. Program FWS/OBS- 79/31. 131 pp. 342 Howey, T.W., and J.H. Blackmon. 1987. Use of a geographic information system as a tool foi making land use management decisions for coastal wetlands in a state regulatory program. Pages 399-418 in O.T. Magoon et al., eds. Coastal Zone '87. American Society of Civil Engineers, New York. Streiffer, H.R., and D.H. Braud. 1987. Automated permit analysis system. Presented at MOSS IV users workshop May 16, 1987. Decision Associates, Inc. Baton Rouge, LA Wicker, K.M. 1981. Chenier Plain region ecological characterization: a habitat mapping study. Louisiana Coastal Resources Program, Louisiana Department of Natural Resources, Baton Rouge, LA 343 EXPERIMENTAL MARSH MANAGEMENT IMPOUNDMENTS R.E. Turner, J.H. Cowan, Jr., LA Mendelssohn, G.W. Peterson, R.F. Shaw, C. Swarzenski, and E.M. Swenson Center for Wetland Resources Louisiana State University Baton Rouge, LA 70803 ABSTRACT Although most of the problems of wetland management are coupled to hydrologic changes and hydrologic manipulations are the main management tool, there are no long-term experimental studies of water regulation schemes for controlling landloss rates and managing fish, fowl, and fur. Some of these changes take years to develop and perhaps reflect long-term variations in water level and water quality. Experimental marshes have been constructed in various wetlands (salt- brackish and intermediate-fresh) and are being used to test the effects of water management on vegetation, soils and water chemistry. The objectives are to (1) establish and run long-term, experimental research areas to develop best marsh management practices (a large land-holding company will donate land, and funding is being sought for the dredging expenses of building the impoundments and for one piece of equipment); (2) encourage coordinated research, develop further funding, and regulate access and disturbance to the experimental study area; and, (3) work with coastal landowners to better manage these wetlands for the long-term. Our emphasis is on ecosystem studies involving Sea Grant funded studies of plant and soil properties, hydrology, and fish and wildlife use. INTRODUCTION It is our purpose here to describe a major research initiative at Louisiana State University on wetland hydrology and wetland management, the reasons for the project, what the project intends to accomplish, and the limitations. Hydrologic Change: Direct and Indirect Hydrologic manipulations are perhaps the only manageable causal agent of change leading to the high wetland loss and habitat changes observed in Louisiana. If there is a possibility for reversing habitat changes, including wetland to water conversions, then hydrologic alterations are likely to be involved. Existing active or direct management measures include annually or seasonally adjusting water levels using weirs, flap gates, earthen plug, and levees. Several extensive water level management schemes are employed on some refuges with mixed success, but are generally too expensive for use on the vast majority of non-refuge wetlands. There are, however, no experimental studies of how different management measures, proposed for different ends and affecting a common resource, affect the long-term stability of the marsh and animals using it. When management has been intentional, the faunal elements have been managed under a "fish, fowl, or fur" scheme with mixed success, if evaluated at all. This is not a criticism of the present management; it is an evaluation of what we do not know and need to know as the coastal landloss and management problems continue. 344 Hydrologic manipulations are particularly prominent as the unintentional consequence of building spoil banks during canal dredging. These spoil levees remain for several decades (Monte 1978). Approximately 8% of the land surface within the deltaic plain from the Mississippi Sound to the Atchafalaya River has been converted to canals and their associated spoil banks. This percentage is equal to the best estimate of the density of natural drainage features. Canals and their spoil banks and water management levees are therefore a major hydrologic factor influencing wetland growth, maintenance, and decay. These levees will continue to be a management issue for the lifetime of the levees. The direct environmental effect of canal construction-the conversion of marsh to open water and spoil-is relatively easy to document. The indirect impacts, however, have only recently been recognized and are, in general, poorly documented or understood (Allen and Hardy 1980). Such effects are often related to the hydrologic regime of the wetland (King et al. 1982; Gilmore et al. 1981; Mendelssohn et al. 1982; Zucca 1982). Changes in wetland water circulation patterns have been caused by long, straight, deep-dredged canals and by adjacent spoil banks which may block normal overland flow and result in saltwater intrusion, acceleration of freshwater runoff, altered sediment deposition patterns, and modification of nutrient supplies to adjacent wetlands. One major indirect effect is to partially or completely impound marshes thereby reducing drying cycles and increasing flooding times (Table 1). The consequences of increased flooding in salt and brackish marshes appear to be reduced marsh plant vigor, accelerated subsidence rates, marsh breakup and loss, and decreased water quality (Table 2) (Adkins and Bowman 1976; Craig et al. 1980; Turner 1987). The increase in canal density exhibited during this century has been accompanied by an acceleration in annual land loss rates and canal surface area (Scaife et al. 1983; Turner et al. 1983; Turner and Rao, in press). Table 1. Changes in hydrologic regime of a semi-impounded salt marsh (from Swenson and Turner 1987). Semi- Control impounded Flooding number of events 12.9 4.5 event length (hours) 29.7 149.9 Drying number of events 11.6 4.00 event length (hours) 31.2 53.9 Mean water level (cm) 1.71 3.99 Volume exchange (m3/m2 marsh aboveground belowground surface) 0.15 0.09 0.06 0.04 345 t/5 K a ? 01) o la ■a >> cs o a 3 a a o w TJ e * a (A 03 o a VI u JS V) W "S. a 93 X w JO a H 8 3 O C/3 8 ON 73 u c X! O s CO JS« s ta E u E 3 «_ CO 3 00 Q. 00 C 3 On —: *, ^H CO p^J CO • *-• 73 « « o ll c°a e 3 H a^ X) 3 a. c 3 u X) 3 a. e 3 u u u g e 3 3 H H 8 s T-H ON . »— 1 "3 ^ (0 -«-» u 4-» u u ii o 3 E CO m H 5 M .2 '3 ■*• i- if U TJ ■a 3 x; «5 o c xs ■« 3 '5b •n o X3 Its 'P "8 CO 8 < «*8 u t e>0 CO -o 3 C co J2 ■-1 r- T3 .3 T3 3 3 O u- ao ? u X) a "8 CO -^ 3 O Eb u > tN 2 o E ■o 3 co (l6^c/)rfg; i - - - * - increased salinity & decreased waterlogging tulates Simulates salt water intrusion only lafes salt Simula water intrusion and subsidence Simulates salt water Intrusion and decreased water level Figure 1. Experimental field design to investigate the effects of simulated saltwater intrusion and subsidence. 356 Vegetation surrounding the experimental plots in both donor and recipient marshes was removed by clipping to within 25 cm of the marsh surface to eliminate the influence of shading on the experimental plants. Vegetation within the treatment and control plots was trimmed to a height of 40 cm in order to eliminate dead material from the previous year. The experiment was replicated five times. The field plots were established during May 1986 and monitored over the succeeding months. The experiment was terminated in October 1986. Factors Preventing Plant Reestablishment in a Brackish Marsh Study Site. The study sites were located in a brackish marsh at Catfish Lake near Golden Meadow, LA. The dieback site was unvegetated and characterized by a soft substrate and standing water. Spartina patens and S. alterniflora were the dominant species in the surrounding vegetated area. Spoil levees originating from the dredging of an oil access canal and adjacent navigation channels circumscribed the dieback site. The control site was located along Bayou Faleau, a natural watercourse within 0.3 km of the dieback site. This area was characterized by unimpeded drainage and 100% vegetative cover composed predominately of S. alterniflora, S. patens, and Distichlis spicata. Salinity levels at control and dieback sites at Catfish Lake were similar and ranged from 11 to 16 ppt during the course of the study. Experimental Design Sods of healthy marsh (soil cores 0.10 m2 surface area and 30 cm deep with intact vegetation) containing either S. alterniflora or S. patens were exhumed from the control site and moved to the dieback site where they were inserted into the substrate at two elevations: equivalent to that of the dieback marsh surface and 10 cm above the marsh surface. Disturbed controls in the healthy marshes were removed in exactly the same manner as the transplanted sods but were replaced in their original locations and elevations. Sod disturbance, per se, had no significant effect on the accumulation of aboveground biomass of S. alterniflora (Mendelssohn and McKee 1987). The experiment, which was replicated five times, was initiated in April 1987 and terminated in October 1987. Plant and Soil Analyses All aboveground material in each experimental plot was clipped at the soil surface and placed into plastic bags. These samples were later analyzed for stem density and live and dead aboveground biomass (after drying at 65 °C). Brightened platinum electrodes were inserted into the soil of each sod at two depths (1 and 15 cm) and allowed to equilibrate for 1 hour prior to measurement of soil redox potential (Eh). Eh was calculated by adding the potential of a standard calomel reference electrode (244 mV) to the millivolt reading. Interstitial water was collected with an in situ water sampler as described in McKee et al. (1988). An aliquot of the water was immediately added to an antioxidant buffer and analyzed for sulfide concentration with a sulfide electrode (Lazar Model IS-146, Lazar Research Laboratories, Los Angeles, CA) (see McKee et al. 1988 for details). The remaining water was used for the measurement of salinity (Fisher conductivity meter), pH, and NH^ concentration (EPA Method 353.2, U.S. Environmental Protection Agency 1979). RESULTS Effect of Increased Salinity and Submergence on Plant Biomass in a Brackish Marsh An increase in salinity from approximately 15 ppt to 26 ppt caused a significant reduction in height, biomass, and density of 5. patens in the field (F = 56.38, 93.39, and 80.16, respectively; 357 p <0.01) (Figure 2). Although there may have been differences in nutrient concentrations between donor and recipient marsh soil, interstitial water concentrations indicated only minor differences in NH4 between the control sods and those transplanted to the recipient marsh (Table 1). Little, if any, difference was noted in pH and Eh. Therefore, the primary difference between the donor and recipient marsh plots was salinity and salinity-related parameters (saltwater intrusion would not only bring in higher salt concentrations, but also more sulfate which, when reduced, would result in higher sulfide levels in the soil). Increased water level significantly reduced the density and biomass (F=31.47 and 23.17, respectively, p < 0.01), but not height, of this species (Figure 2). Interstitial water sulfide concentrations were significantly higher in the lower elevation plots in both the donor and recipient marshes (F = 19.92, p <0.01) (Table 1). There was also a significant negative relationship between soil sulfide and biomass at the donor (r = -0.68) and recipient (r = -0.72) marshes. Soil NH4 concentrations were significantly higher in the more waterlogged plots (F = 73.91, p <0.01), particularly in the recipient marsh (Table 1). There were also significant relationships between soil NHA and sulfide (r = 0.87, donor; 0.79, recipient), soil NH4 and biomass (r = -0.69, donor; -0.79, recipient), and soil NH4 and density (r = -0.57, donor; -0.87, recipient). Live aboveground biomass was most reduced in the low elevation (-10 cm) treatment in the recipient marsh, indicating a greater negative effect of the combination of increased salinity and waterlogging on the growth of S. patens than either factor acting alone (Figure 2). However, the interaction between the two factors was not significant and their combined effect on biomass was additive. When the elevation of the transplanted plots was increased to 10 cm above the recipient marsh surface, height, biomass, and density were not significantly increased above that of plots placed equivalent to the ambient elevation (Figure 2). Factors Preventing Plant Reestablishment in a Brackish Marsh All of the sods that were transplanted to the dieback site at marsh elevation exhibited highly reducing conditions compared to the controls (Table 2). Redox potentials were significantly lower in the dieback sods placed at marsh elevation (Table 2). Sulfide concentrations in the dieback sods (marsh elevation) were 1.5 times higher than in the control sods (Table 2). Aboveground biomass and stem density of S. patens were significantly reduced in these plots compared to controls (Figure 3). However, the biomass produced in the S. alterniflora-dominaled sods transplanted into the same dieback site was double that of its controls; stem density was also significantly increased. The reducing conditions of the dieback site were somewhat ameliorated in the elevated sods (Table 2). Increasing the elevation of the S. patens sods in the dieback site resulted in greater biomass production, but no further increase occurred in the elevated S. altemiflora sods (Figure 3). NH4 concentrations in the interstitial water of the S. patens dieback plots were significantly higher and salinity significantly lower than that in the control plots (Table 2). However, the NH4 concentrations and salinity in the S. altemiflora soil did not differ significantly among sites. DISCUSSION Since the vertical accretion of marshes is dependent upon the accumulation of organic matter produced by marsh macrophytes, any reduction in primary productivity will slow the aggradation propess. A sudden change in the environment that leads to a rapid reduction in biomass or even complete elimination of the emergent vegetation in a marsh would reduce the potential for the marsh accretion rate to keep pace with subsidence and sea level rise. A reduction in belowground roots and rhizomes, which bind the sediment and provide stability, would accelerate subsidence and 358 DONOR RECIPIENT DONOR RECIPIENT LOCATION LOCATION Figure 2. Interstitial water salinity and height, stem density, and live aboveground biomass of Spartina patens sods after six months growth at different elevations within two marshes of differing salinity. DC = disturbed control; UC = undisturbed control (n = 5). See text for further details. 359 Table 1. Soil redox potentials (Eh) (mV) and interstitial water pH, sulfide (mM) and NH4 (ppm) concentrations measured in Spartina patens sods placed equal with (disturbed control (DC) and undisturbed control (UC)) or 10 cm below marsh surface in the donor marsh and at three elevations (equal to, 10 cm above, or 10 cm below surface) in the recipient marsh after one growing season (n = 5). Donor marsh -10 cm DC (=) UC(=) -10 cm Recipient marsh + 10 cm Eh (1 cm) -5 ±41 -58 ± 34 9 ± 46 -134 ± 21 Eh (10 cm) -92 ± 42 -33 ±38 -80 ± 29 -160 ± 7 pH 7.1 ± 0.1 7.1 ± 0.1 6.8 ± 0.0 7.1 ± 0.1 38 ±39 109 ± 34 -120 ± 16 -104 ± 34 6.9 ± 0.3 6.5 ± 0.3 Sulfide 0.34 ± 0.12 0.02 ± 0.01 0.01 ± 0.00 2.10 ± 0.61 0.01 ± 0.01 0.01 ± 0.01 NH4-N 1.6 ± 0.34 0.6 ± 0.1 0.8 ± 0.2 8.3 ± 1.3 0.4 ± 0.1 0.5 ± 0.2 Table 2. Soil redox potentials (Eh) (raV) and interstitial water salinity (ppt), pH, sulfide (mM), and NH4-N (ppm) concentrations measured in control (healthy marsh) and treatment (dieback marsh) sods placed at two elevations (equivalent with or 10 cm above the dieback marsh surface) at a brackish marsh site (n = 5). Sods contained either Spartina altemiflora or S. patens. Variable Control Dieback (=) Dieback ( + 10 cm) Spartina patens sods Eh (1 cm) Eh (15 cm) Sulfide Salinity pH NHA-N Spartina altemiflora sods Eh (1 cm) Eh (15 cm) Sulfide Salinity pH NH4-N +294 ± 45 -257 ± 23 + 186 ± 79 -35 ± 57 -291 ± 46 -264 ± 40 1.13 ± 0.44 2.44 ± 0.16 2.13 ± 0.22 [6.4 ± 0.4 11.2 ± 0.2 11.2 ± 0.4 6.9 ± 0.0 7.1 ± 0.0 7.1 ± 0.1 1.51 ± 0.34 8.10 ± 0.45 3.60 ± 0.63 +298 ± 46 -173 ± 59 + 19 ± 78 -102 ± 73 -260 ± 55 -289 ± 13 1.00 ± 0.44 2.50 ± 0.13 1.28 ± 0.31 14.4 ± 0.5 14.2 ± 0.9 13.6 ± 0.5 6.9 ± 0.0 7.1 ± 0.1 7.2 ± 0.2 0.67 ± 0.45 2.59 ± 1.10 1.75 ± 0.49 360 break-up of the substrate. The rapid rate of subsidence in Louisiana's coastal zone (Baumann et al. 1984), in combination with the predicted sea level rise of 50 to 200 cm during the next 100 years (Titus 1986), will lead to increased salinity and flooding stresses. A salinity range of 21-28 ppt produced a significant reduction (compared to controls at 11-15 ppt) in aboveground biomass of S. patens. Since S. patens possesses salt glands (Anderson 1974), this species has the capability of extruding excessive salt, thus aiding in control of internal electrolyte concentrations. Although toxic ion effects cannot be totally excluded, the significant reduction in aboveground biomass of S. patens in response to simulated saltwater intrusion was most likely caused by a water deficit, which resulted in substantial tissue death upon sudden exposure to more saline conditions. Two months after transplantation to the higher salinity marsh, approximately 50% of the original tissue was dead. However, new green shoots had also appeared in these plots. Although these results indicate that S. patens may recover to some extent from sudden influxes of saltwater that kill the original biomass, the potential for biomass production would be nevertheless significantly reduced. Flooding with saltwater may cause stresses in addition to those resulting from increased electrolyte concentrations or physiological drought. If the influx of saltwater is accompanied by an increase in depth or duration of flooding, then the plants may also experience root oxygen deficiencies, decreased nutrient uptake, and/or a buildup of toxic compounds such as hydrogen sulfide in the highly reducing soil environment (Hook 1984; Kozlowski 1984). Many inland brackish and salt marshes in Louisiana are characterized by low productivity, decreased elevations due to subsidence, increased waterlogging, and high soil sulfide concentrations. Factors associated with increased soil waterlogging have been implicated in decline in growth and dieback of S. alterniflora (Linthurst and Seneca 1980; Mendelssohn and Seneca 1980; Howes et al. 1981; Mendelssohn et al. 1981; King et al. 1982; DeLaune et al. 1983; Mendelssohn and McKee 1988). The results of this study demonstrate that dieback of S. /?a/ms-dominated brackish marshes may in some cases also be caused by similar mechanisms. The results showed that the aboveground growth of S. patens can be adversely affected when the soil becomes highly reduced and sulfide accumulates (2.5 mM). The strong negative effect of greater soil waterlogging on plant growth was evident in the saltwater intrusion-subsidence experiment (Figure 2), as well as the dieback site experiment (Figure 3). The significant reduction in aboveground biomass and stem density of S. patens caused by an in situ decrease in elevation alone further emphasizes the effect of elevation on plant growth (Figure 2). The inhibitory effects of waterlogging were ameliorated, however, when the elevation of the plots was increased 10 cm. This result was evident in both experiments. The positive effect of increased elevation suggests that restoration of such a dieback area with S. patens would require sediment additions to raise the elevation of the inland marsh. In contrast to S. patens, standing biomass of S. alterniflora in sods transplanted to the same dieback site was significantly higher that of the controls (Figure 3). These results indicate that S. alterniflora can tolerate sulfide levels of about 2.5 mM for a growing season and that transplantation of this species to a dieback brackish marsh would possibly succeed in restoring the area without the need for sediment additions. Although S. alterniflora was more tolerant of waterlogged brackish sites- than S. patens, S. alterniflora standing biomass can be significantly reduced in salt marsh dieback sites where sulfide concentrations increase to extremely high levels (4-5 mM) (McKee and Mendelssohn, unpubl. data). Also, there is evidence that belowground biomass of S. alterniflora is significantly reduced by moderate levels of sulfide (2.5 mM) (Koch and Mendelssohn, in press). Thus, depending on the site, restoration with S. alterniflora may require sediment additions to achieve a long-term recovery. 361 BRACKISH MARSH m S. altcmiflora 0 S. patens CONTROL, DEBACK - DIEBACK +10 cm Figure 3. Live aboveground biomass and stem density measured in sods after seven months growth at two elevations (equal to or 10 cm above surface) in a brackish marsh dieback site. Control sods were located in a nearby healthy marsh (n = 5). 362 Hydrological modifications that impair drainage of water from marshes may promote the accumulation of sulfide to potentially toxic levels. The amount of sulfide accumulation would depend on a number of factors including sulfate input, organic matter content of the soil, available Fe, and flushing rate of the soil substrate. The effect of saltwater intrusion on brackish marsh species such as S. patens may not only be due to osmotic effects of increased salinities, but also to sulfide toxicity. The input of sulfate with more saline water would contribute to the generation of sulfide, which may accumulate in areas where flushing and aeration of the soil is prevented (e.g., in inland subsided marshes or artificially impounded sites). For these reasons, marsh restoration plans that involve changes in drainage patterns, for example, should be carefully evaluated to ensure that conditions conducive to the accumulation of sulfide and other reduced toxic compounds are not created in the process. Even though increases in salinity and waterlogging may negatively affect brackish marsh species, this effect does not explain why degraded areas do not become revegetated with more salt- or flood-tolerant species. Recolonization of a deteriorated marsh would not only depend on a source of propagules (seeds or rhizomes), but on conditions suitable for plant survival and growth. Recolonization through seed would require a period in which the marsh surface is exposed or where light requirements for germination are met. In areas where the minimum water level is increased through subsidence or sea level rise to a point above the marsh surface, seed germination would be inhibited because of the continued presence of water over the marsh surface. Even if seed production, dispersal, and germination rates were high, the conditions in the degraded marsh may be too inhibitory for seedling survival. Furthermore, marsh grasses such as S. patens and S. alterniflora spread primarily through vegetative propagation. Thus, if emergent vegetation were suddenly eliminated from an area through a change in salinity regime or inundation levels, erosion and subsidence of the marsh surface may proceed to a point where seedling establishment cannot occur. Vegetative spread may occur too slowly to allow succession to a more flood- or salt-tolerant vegetation type. Furthermore, the presence of high levels of soil phytotoxins, which may accumulate in unvegetated areas, may inhibit vegetative invasion, as well as seedling establishment. CONCLUSIONS This study has demonstrated how basic research with standard bioassay techniques can be used to evaluate the relative impact of salinity and water level and to identify factors preventing the reestablishment of vegetation in a brackish marsh dieback site. This technique showed that brackish marshes can be negatively affected by both saltwater intrusion and subsidence. However, the ability to restore a deteriorated brackish marsh in Louisiana was not controlled by salinity levels, but rather by the degree of plant inundation and the accumulation of soil phototoxins because of altered hydrology and lowered marsh surface elevation. These data support the hypothesis that marsh restoration can be accomplished by revegetation, sediment addition, or a combination of the two. The data further showed that information about soil-plant interactions would be essential to the proper choice of restoration technique. REFERENCES Anderson, C.E. 1974. A review of structure in several North Carolina salt marsh plants. Pages 307-344 in R.J. Reimold and W.H. Queen, eds. Ecology of halophytes. Academic Press, New York. Baumann, R.H., J. W. Day, and C.A Miller. 1984. Mississippi deltaic wetland survival: sedimentation versus coastal submergence. Science 224:1093-1094. 363 Boesch, D.F. 1982. Modification in Louisiana, causes, consequences and options. Proceedings of a Conference on Coastal Erosion and Wetlands. U.S. Fish Wildl. Serv. Biol. Serv. Program FWS/OBS-83/59. 259 pp. DeLaune, R.D., C.J. Smith, and W.H. Patrick, Jr. 1983. Relationship of marsh elevation, redox potential, and sulfide to Spartina altemiflora productivity. Soil Sci. Soc. Am. J. 47:930-935. Gagliano, S.M. 1981. Special report on marsh deterioration and land loss in the deltaic plan of coastal Louisiana, presented to Louisiana Department of Natural Resources, Louisiana Department of Wildlife and Fisheries, Coastal Environments, Inc., Baton Rouge, LA. Hook, D.D. 1984. Adaptations to flooding with fresh water. Pages 265-294 in T.T. Kozlowski, ed. Flooding and plant growth. Academic Press, New York. Howes, B.L., R.W. Howarth, J.M. Teal, and I. Valiela. 1981. Oxidation-reduction potentials in a salt marsh: spatial patterns and interactions with primary production. Limnol. Oceanogr. 26:350-360. King, G.M., M.J. Klug, R.G. Wiegert, and AG. Chalmers. 1982. Relation of soil water movement and sulfide concentration to Spartina altemiflora production in a Georgia salt marsh. Science 218:61-63. Kozlowski, T.T. 1984. Plant responses to flooding of soil. Bioscience 34:162-167. Linthurst, R.A, and E.D. Seneca. 1980. The effects of standing water and drainage potential on the Spartina altemiflora -substrate complex in a North Carolina salt marsh. Estuarine Coastal Mar. Sci. 11:41-52. Mendelssohn, I.A, and K.L. McKee. 1987. Experimental field and greenhouse verification of the influence of saltwater intrusion and submergence on marsh deterioration: mechanisms of action. Pages 8/1-8/34 in R.E. Turner and D.R. Cahoon eds. Causes of wetland loss in the coastal central Gulf of Mexico. II: Technical narrative. Final report to the Minerals Management Service, New Orleans, LA 400 pp. Mendelssohn, I.A, and KL. McKee. 1988. Spartina altemiflora dieback in Louisiana: time-course investigation of soil waterlogging effects. J. Ecol. 76:509-521. Mendelssohn, I.A, and E.D. Seneca. 1980. The influence of soil drainage on the growth of salt marsh cordgrass Spartina altemiflora in North Carolina. Am. J. Bot. 58:48-55. Mendelssohn, I.A, K.L. McKee, and W.H. Patrick, Jr. 1981. Oxygen deficiency in Spartina altemiflora roots: metabolic adaptation to anoxia. Science 214:439-441. Mendelsohn, I.A, R.E. Turner, and K.L. McKee. 1983. Louisiana's eroding coastal zone: management alternatives. J. Limnol. Soc. South. Afr. 9:63-75. Titus, J.G. 1986. Greenhouse effect, sea level rise, and coastal zone management. Coastal Zone Manage. J. 14:147-171. Turner, R.E., and D.R. Cahoon. 1987. Causes of wetland loss in coastal central Gulf of Mexico. Vol. 2: Technical narrative. Minerals Management Service, New Orleans, LA 400 pp. Turner, R.E., R. Costanza, and W. Scaife. 1982. Canals and wetland erosion rates in coastal Louisiana. In D.F. Boesch, ed. Proceedings of the Conference on Coastal Erosion and Wetland Modifications in Louisiana: Causes, Consequences and Options. U.S. Fish Wildl. Serv. FWS/OBS-82/59. U.S. Environmental Protection Agency. 1979. Methods of chemical analysis of water and wastes. Environmental Monitoring and Support Laboratory, Cincinnati, OH, EPA-600/4-79-020. Wicker, KM. 1980. Mississippi deltaic plain region ecological characterization: a habitat mapping study. A user's guide to the habitat maps. U.S. Fish Wildl. Serv. Biol. Serv. Program, FWS/OBS-79/07. 364 A LEGAL REVIEW OF SOME LOUISIANA WETLAND MANAGEMENT ACTIVITIES James G. Wilkins and Michael Wascom LSU Sea Grant Legal Program 170 Paul Hebert Law Center Baton Rouge, LA 70803 ABSTRACT Land owners in Louisiana wishing to undertake marsh management must obtain a coastal use permit (CUP) from the Louisiana Department of Natural Resources' Coastal Management Division (CMD), which administers the Louisiana Coastal Resources Management Act (CRMA), and U.S. Army Corps of Engineers (Corps), §10 and/or §404 permit. In some parishes, local coastal management programs replace CMD for activities in the coastal zone defined as uses of local concern. In some situations a permit may be required from the Department of Natural Resources' Division of State Lands (DSL). At the State level, several agencies have commenting authority on CUP applications through memoranda of understanding (MOU) with CMD. Under the memoranda, CMD is required to condition its permits so that they comply with the regulatory requirements of five of the agencies which may have jurisdiction over the permitted activity. The MOU between CMD and the Department of Wildlife and Fisheries (DWF) requires that DWF comments be given full consideration and responded to in the actual permit document. The Federal permitting authority for marsh management activities is the Corps, with other Federal agencies having commenting authority. Memoranda of agreement with the Federal agencies give them the authority to request elevation to a higher level of review if their comments are not responded to satisfactorily, resulting in significant time delays in permit decisions. Under Federal consistency requirements, the Corps' permit decisions must be consistent with approved State management programs. The Corps operates under the Rivers and Harbors Act of 1899 and the Clean Water Act. These Federal statutes regulate structures blocking navigable waters and dredge and fill in wetlands respectively. The Endangered Species Act could prevent issuance of a Corps permit if the marsh management activities adversely affected a threatened or endangered species. State laws affecting marsh management are the CRMA and various State property laws. The CRMA administered by CMD, attempts to balance development with conservation in the coastal zone. The State property laws affecting marsh management are designed to delineate State/private property ownership rights and protect State property ownership. These laws limit certain marsh management activities. The regulatory process for obtaining a marsh management permit may be slow due to interagency checks and balances and widely varying policies and mandates. INTRODUCTION Within the last 15 years, much attention has been focused on Louisiana's coastal erosion problems. An outgrowth of the concern for Louisiana's coastal resources has been the emergence 365 of using marsh management practices and techniques to aid in controlling land loss and to prevent further depletion of fish and wildlife stocks. It is the purpose of this paper to examine how marsh management practices fit within Federal and Louisiana regulatory schemes, to identify problems and conflicts that may exist in the law, and to help guide prospective marsh managers through the regulatory maze. There are a myriad of activities carried out in the name of marsh management; consequently, the first step is to define the term "marsh management." The Technical Steering Committee for the Minerals Management Service study has developed the following tentative definition: " ... marsh management is defined as the use of structures to manipulate local hydrology for the purpose of reducing or reversing wetland loss and/or enhancing productivity of natural renewable resources." While this definition does not encompass all the activities that have traditionally been associated with marsh management, it seems to address most of the current policy considerations and goals. In all likelihood, this definition is now or will become the standard used by the various regulatory agencies in evaluating proposed marsh management plans; therefore, it will be the focus here although other practices will be examined in less detail. This discussion is also limited to marsh management plans that are to be carried out on privately owned land. Since there are differences in the laws that apply to Federal and State wildlife refuges, marsh management activities in these areas will not be discussed. PROCEDURES AND PERMITTING NETWORK Permit Requirements and Application Procedures Under the provisions of the Louisiana State and Local Coastal Resources Management Act of 1978 (CRMA), a landowner or manager wishing to implement a structural marsh management plan in the coastal zone (statutorily defined at La. R.S. 49:213.4) of Louisiana must obtain a coastal use permit (CUP) from the Coastal Management Division (CMD) of the Louisiana Department of Natural Resources or a permit from a local coastal management program (La. R.S. 49:213.11). In most situations, they must also obtain a permit from the U.S. Army Corps of Engineers (Corps) under §10 of the Rivers and Harbors Act of 1899 (33 U.S.C. §403) or under §404 of the Clean Water Act (33 U.S.C. §1344). In certain situations both Corps permits will be required. In some cases a permit or a right of way grant may also be required from the Division of State Lands (DSL) of the Department of Natural Resources (La. R.S. 41:1703). In accordance with a memorandum of understanding between CMD and the New Orleans District of the Corps establishing a "one window" permitting system, the CMD has been designated as the lead agency. This means that for regulating activities in the coastal zone which have a direct and significant impact on coastal waters and which are also subject to the §10 and §404 permitting jurisdiction of the Corps, CMD is responsible for receiving permit applications and issuing joint public notices. Therefore, an applicant for a marsh management plan within the coastal zone should apply to CMD for a CUP. CMD will then immediately notify the Corps and send them a copy of the permit application. The Corps then makes the determinations as to whether or not a §10 or §404 permit is required and if so begins processing the application as if the applicant had applied directly to them for those permits. A determination is also made by the two agencies as to whether or not a joint public notice will be used. Both agencies are required to provide a notice and comment period before they may issue their respective permits (La. R.S. 49:213.1 1(c)(2); 33 U.S.C. §1344(a)). Since this is only a joint public notice agreement and not a joint permitting system, if either agency 366 decides that the application is not complete for its purposes, it may decide to delay the public notice until more information is obtained from the applicant (R. Bosenburg, U.S. Army Corps, of Engineers, New Orleans, LA; pers. comm.). In that case the other agency may decide to go ahead with its processing of the permit application including an independent public notice. State Permitting Network The State permitting network for activities in the coastal zone including marsh management activities consists of the permitting agency, CMD or the local (parish) coastal management program, and the State commenting agencies. Under this system, decisions to issue a coastal use permit are based not only on the guidelines and regulatory policies of the lead agency but also on compliance with the regulatory requirements and policies of the commenting agencies. CMD has memoranda of understanding with seven other State agencies: the Office of Conservation and Division of State Lands of the Department of Natural Resources, the Department of Environmental Quality, the Department of Health and Hospitals, the Department of Culture Recreation and Tourism, the Department of Agriculture, and the Department of Wildlife and Fisheries (DWF). These memoranda of understanding provide for notification from CMD of activities which may fall under the jurisdiction of the various agencies and give the agencies authority to comment on the proposed activity. Additionally, the memoranda provide that for all the agencies listed above, with the exception of the Department of Agriculture and DWF, CMD will condition the approval of coastal use permits on compliance with the rules and regulations of these commenting agencies and upon the applicant obtaining any permits required by these agencies. Under this system, for example, if an archaeological or historical site or park would be impacted, the Department of Culture Recreation and Tourism is notified and may comment to CMD. The comments may establish conditions or object completely to the proposed activity. The Department of Agriculture may comment on or object to activities, including the use of pesticides, which impact agricultural resources, and CMD must respond to these comments to the maximum extent practicable in their permit decisions. The memorandum of understanding does not require that CMD condition CUP's to be consistent with the regulatory requirements of the Department of Agriculture. The DWF memorandum of understanding with CMD provides that DWF's comments on coastal use permit applications will be "given full consideration in the coastal use permit decision process and summarized and responded to in the actual permit document." Comments about policy concerns by the other agencies not involving violations of their regulatory authority are evaluated by CMD for consistency with the CRMA and may or may not be acted upon by CMD. Also, CMD reviews comments of other State and Federal agencies and incorporates those that don't conflict with the CRMA (J. Rives, CMD; pers. comm.). An in-lieu permitting system has been established by the CRMA and further developed in a memorandum of understanding between CMD and the Office of Conservation of the Department of Natural Resources. This system divides permitting authority for oil and gas related activities between the two agencies. For example, the siting and drilling of oil or gas wells require permits from the Office of Conservation instead of a CUP. However, if access to the drill site requires dredging a canal or building a board road in the coastal zone a CUP is required for that activity in addition to the Office of Conservation permit. The CRMA also establishes local coastal management programs under which the local program may assume the permitting authority for activities in the coastal zone defined by the CRMA as uses 367 of local concern (La. R.S. 213.9). In accordance with this system, approved local programs have been established in some parishes and have assumed permitting authority from CMD over certain coastal uses of local concern. Under the CRMA a marsh management plan which intersected only one body of water and which used a water control structure costing less than $15,000 would be of local concern and would require a parish permit rather than a CUP (La. R.S. 213.5A(l)(a),(2)(j). In addition the approved local programs are given the authority to comment on coastal use permit applications being reviewed by CMD. The Coastal Management Division tries to accommodate these comments if they concern something specifically addressed in the parish program or relate to something of local concern and are not contrary to State policy (Rives, pers. comm.). FEDERAL PERMITTING NETWORK At the Federal level, the Corps (33 U.S.C. §1342 and 1344; 33 U.S.C. §403) is the permitting agency regulating marsh management activities involving the discharge of dredged or fill material in wetlands or for structures blocking navigable waters. This jurisdiction is statewide and is not limited to the statutorily defined coastal zone as is the jurisdiction of CMD (33 U.S.C. §1362(12); 33 U.S.C. §403). Other Federal and State agencies are given commenting authority. This commenting authority is granted to the U.S. Fish and Wildlife Service (USFWS) and DWF by the Fish and Wildlife Coordination Act (16 U.S.C. 661-666c) and through a memorandum of agreement between the DWF and the Corps. The National Marine Fisheries Service (NMFS), though not specifically listed in the Fish and Wildlife Coordination Act, comments under authority of that act since it was formerly the Bureau of Commercial Fisheries within the USFWS (35 Fed. Reg. 18,455). That bureau was transferred along with its functions to the Department of Commerce in 1970 (35 Fed. Reg. 15,627). Thus, NMFS retained the commenting authority it had under the Fish and Wildlife Coordination Act as the Bureau of Commercial Fisheries in the USFWS. NMFS also comments under authority of a memorandum of agreement between itself and the Corps and various other Federal statutes that grant NMFS responsibility for the protection of the habitat of living marine resources. The Environmental Protection Agency (EPA) comments under the authority of the Clean Water Act and a memorandum of agreement with the Corps (33 U.S.C §1344(c)). The memoranda of agreement between the Corps and EPA NMFS, and USFWS also gives them the authority to request referral of a District Engineer's (DE) decision to issue a permit. This means that it will be reviewed at a higher level within the Corps. This process is called elevation and would occur when the DE notifies the agency of its intent to issue the permit without recommended conditions or over a recommendation of denial. In actuality the Corps and the commenting agencies attempt to resolve conflicts through standard procedures before the elevation state is reached (Bosenburg, pers. comm.). Some of these procedures are outlined in the memoranda of agreement while others are based on informal agreements between the agencies. One such procedure is the interagency meeting. Interagency meetings between the Corps, Federal, and State commenting agencies and the applicant are often held to discuss conflicts and possible solutions before a permit decision is made. Often a commenting agency's proposed conditions coupled with its notice of intent to request elevation serves as a catalyst for discussions between the applicant and the agency. Many conflicts are resolved at this point. When an impasse is reached in which the applicant refuses to modify 368 his proposed project or address the agency's concerns and the agency threatens elevation, the Corps must make the decision on the permit application. The Corps may impose conditions on the permit that will result in enough of a compromise that the commenting agency will withdraw its request for elevation but maintain its objections (Bosenburg, pers. comm.). Referral and elevation can result in significant time delays (120 days or more) in the processing of a permit. Because of the time and effort associated with the elevation process, the Corps attempts to avoid having its permit decisions elevated by delaying its permit decision in hopes of a compromise being reached between the applicant and the commenting agency (D. Clark, CMD; pers. comm.). In addition to its authority to request elevation under the memorandum of agreement, EPA is given the authority by the Clean Water Act to establish, after consultation with the Corps, substantive guidelines to be used by the Corps in evaluating §404 permit applications (33 U.S.C. §1344(b)). The Clean Water Act further provides that EPA may prohibit the specification of any defined area as a disposal site for dredge or fill material whether before or after a §404 permit has been issued if it determines that such disposal will have an adverse impact on municipal water supplies, shellfish beds, fishery areas including spawning and nursery areas, and wildlife or recreational areas (33 U.S.C. § 1344(c)). This gives EPA veto authority over Corps §404 permit decisions before or after permit issuance. The Corps §404 permit decisions are also affected by the comments and regulatory requirements of certain State agencies. Under the Federal consistency requirements of the Coastal Zone Management Act of 1972 (CZMA) Federal agencies including the Corps are required to "conduct or support activities which directly affect the coastal zone of a State in such a manner which is to the maximum extent practicable consistent with approved State management programs" (16 U.S.C. §1457). In accordance with this mandate, the Corps will not issue a §404 or §10 permit for a project over which CMD has jurisdiction unless CMD has either issued a CUP or a determination that the project is consistent with the Louisiana Coastal Resources Program (LCRP), whichever is appropriate. Nor may the Corps issue an §404 or §10 permit with conditions that are inconsistent with a preissued CUP (Clark, pers. comm.). Thus, to obtain a §404 permit, the applicant must satisfy the regulatory requirements of CMD. This could bring in the comments of the other State agencies with which CMD has memoranda of understanding as mentioned above. In the case of blockage or usurpation of State waterbottoms, the DSL may affect a §404 permit by raising an objection to a CUP permit application that CMD feels is sufficient to deny the permit. The denial of the CUP would in effect be a determination of inconsistency with the LCRP thereby prohibiting the Corps from issuing the §404 permit. The DSL may also object directly to the Corps concerning §404 or §10 permit applications. The Corps will not issue a permit over such objections (R. Gonzales, U.S. Army Corps of Engineers, New Orleans, LA; pers. comm.). Section 401 of the Clean Water Act requires an applicant for a Federal license or permit which results in any discharge into navigable waters to obtain a certification from the State that the discharge will comply with the applicable provisions of the Clean Water Act (33 U.S.C. §1341(a)(l)). Under this provision the Corps is prohibited from issuing a §404 permit in Louisiana if the applicant has not obtained a water quality certification from the Louisiana Department of Environmental Quality (DEQ) or such certification has been waived by DEQ. This requirement is not limited to the coastal zone but has statewide application. The certification period involves a public notice and comment period and DEQ usually attaches conditions to its certifications (L. Wiesepape, Department of Environmental Quality; pers. comm.). 369 The Clean Water Act and the CRMA provide for penalties for violations of their provisions (33 U.S.C. §1319; La R.S. 49:213.17). Both the Corps and CMD employ personnel to enforce those provisions. The Corps employs an after-the-fact permitting system in which those who perform activities without a §10 or §404 permit may obtain a permit after the work is completed if legal considerations allow (P. Serio, U.S. Army Corps of Engineers, New Orleans, LA; pers. comm.). CMD will issue after-the-fact permits only for activities performed in emergency situations (Clark, pers. comm.). With the permitting and regulatory framework discussed in the previous section in mind we will now examine in more detail some of the complex legal issues and statutory interpretation on which the system operates. Later we will discuss some of the major policy concerns that drive these decisions. LEGAL AND REGULATORY REVIEW Federal Regulation Two of the main Federal statutes are §10 of the Rivers and Harbors Act of 1899 and §404 of the Clean Water Act, both administered by the Corps. Section 10 of the Rivers and Harbors Act of 1899 prohibits the creation of any obstruction, excavation (dredging), or filling in a navigable water of the United States (33 U.S.C. §403). For §10 purposes, navigable waters are defined as "waters of the United States that are subject to the ebb and flow of the tide shoreward to the mean high water mark and/or are presently used, or have been used in the past, or may be susceptible to use to transport interstate or foreign commerce" (33 C.F.R. §§32 1.2(a), 322.2(a) and 329.4). The jurisdiction applies to artificial as well as natural water bodies throughout the State. A §10 permit would be required for any marsh management practices using a dam or weir or other structure or work in navigable waters. Such permits are susceptible to objection by the DSL based on the prohibition in the Louisiana Constitution against the alienation of State water bottoms. The Corps withdraws §10 permits on the basis of such objections (R. Ventola, U.S. Army Corps of Engineers, New Orleans, LA; pers. comm.). Section 301 of the Clean Water Act prohibits the discharge of any pollutant into waters of the U.S. except under permit issued by the EPA (33 U.S.C. §1311). However, in the case of the discharge of dredged or fill material into the waters of the United States, the Corps is the permitting agency in accordance with §404 of the Clean Water Act (33 U.S.C. §1344). The definition of waters of the United States for §404 purposes is broader than the §10 definition. It includes, in part, waters which are used or have been used or are susceptible to use in interstate or foreign commerce, waters (including wetlands) the degradation of which could affect interstate or foreign commerce, and wetlands that are adjacent to such waters. All waters which are subject to the ebb and flow of the tide are considered to meet the interstate or foreign commerce use test (33 C.F.R. §328.3). The definition of navigable waters under §404 is very broad and covers almost any body of water affecting interstate commerce, except certain isolated waters and including isolated wetlands. A considerable amount of litigation has occurred in the battle to delineate the scope of the definition of adjacent wetlands (See for example U.S. v. Riverside Bayview Homes Inc. 474 U.S. 121 (85)) and to determine the level of effect on interstate commerce required to include isolated wetlands in §404 jurisdiction. It is unlikely that any significant areas of wetlands in 370 Louisiana, especially in the coastal area, do not meet the §404 test for U.S. waters. Therefore, we will assume that most Louisiana coastal areas meet this test and forgo the very technical legal arguments surrounding the current controversy over §404 jurisdiction in "adjacent" and "isolated" wetlands. A marsh management plan which involves the discharge of dredged or fill material into U.S. waters, such as would be involved with earthen dams and levees, will require a §404 permit. This is in addition to a §10 permit if the structure is to be constructed in waters defined as navigable for §10 purposes. The EPA is given the power to "guide" the Corps in its permitting of disposal sites for dredged or fill material by §404(b) and has done so in the §404(b)(l) guidelines (40 C.F.R. §230.1 to §230.80). These guidelines provide substantive criteria for the Corps to use in evaluating proposed disposal sites, including certain mandated requirements. The EPA may veto the permitting of specified disposal sites if it finds that there would be "an unacceptable adverse effect on municipal water supplies, shellfish beds and fishery areas (including spawning and breeding areas), wildlife, or recreation areas" (33 U.S.C. §404(c)). The EPA has rarely used this veto authority but recent cases indicate that the EPA may take a more active role in this area in the future (Bersani v. Robichaud, 850 F. 2d 36 (2nd Cir. 1988). In cases where the discharge of material is not intended as fill but has the effect of changing the character of the disposal area to dry land or raising the level of a non-navigable water bottom, a permit would be required from EPA under §402 of the Clean Water Act rather than a §404 permit (33 C.F.R. §323.2(k), 49 C.F.R. §122.2). This is the result of different definitions of "fill" material used by the Corps and EPA in their respective regulations. EPA's definition is apparently used so they can regulate discharges that would not be regulated under the Corps' definition of fill. Section 402 of the Clean Water Act would also regulate discharges of any other pollutant. There are some exceptions for agricultural purposes such as agricultural return flows (33 U.S.C. §1342(1)(1)). Under the Fish and Wildlife Coordination Act (16 U.S.C. §662(a)) the USFWS, the NMFS, and DWF are given authority to comment and make recommendations on proposed alterations to any stream or other body of water by a Federal agency or under Federal permit or license. Such consultation is mandatory and while the commenting agencies do not have veto authority, their comments are required to be, and are, given consideration by the Corps. Furthermore, where feasible, their recommendations are required to be implemented as part of the project to maintain "maximum overall project benefits" and wildlife conservation and enhancement (16 U.S.C. §662(b)). This does not mean that the comments will necessarily be reflected in the permit conditions. In addition, under the memoranda of understanding discussed in the preceding section, the Federal agencies have the authority to request elevation if their comments and suggestions are not acted upon by the Corps. Thus a proposed marsh management project could be modified or possibly denied by the permitting agency (in this case the Corps) in response to the comments and recommendations of the various agencies. At the very least, considerable delays in the permitting process will likely occur as a result of adverse comments from the commenting agencies. This is because although the Corps has the authority to make the ultimate permitting decision and override the recommendations of the commenting agencies it may withhold its permit decision while attempting to bring about an agreement between the adverse parties. Another Federal statute that could affect marsh management activities is the Endangered Species Act (ESA) (16 U.S.C. §§1531-1543). This law protects species of animals and plants that have been listed as endangered or threatened. Federal agencies are required to carry out their activities, including licensing and permitting, in such a manner that gives very strong consideration to 371 protection of critical habitat of endangered or threatened species (16 U.S.C. §1536). Critical habitat is an area or areas either within or outside the geographic range of an endangered or threatened species that possesses the qualities essential for the conservation of the species (16 U.S.C. §1532(5)(A)). Through the consultation process mandated by the ESA (16 U.S.C. § 1536), a Federal agency can be prohibited from carrying out its project or licensing or permitting an activity if critical habitat would be destroyed or adversely affected. The USFWS and NMFS have been delegated the responsibility of enforcing the provisions of the ESA which provides another avenue of commenting authority to all Federal agencies. The ESA and the regulations promulgated pursuant to it also contain prohibitions against any one, including private citizens, harassing, harming, pursuing, hunting, shooting, wounding, killing, trapping, capturing, or collecting an endangered or threatened species (16 U.S.C. §1538). The presence of an endangered or threatened species or its critical habitat within or in close proximity to a proposed marsh management area could give rise to challenges to certain activities under the ESA by USFWS, NMFS, or other parties. There are several endangered or threatened species of animals and plants that inhabit Louisiana for at least part of the year. The recent controversy over turtle excluder devices underscores the power of this law (Wilkins 1987). State Laws Affecting Marsh Management The primary State laws that affect marsh management are the CRMA (La. R.S. 49:213.1-213.22) and various Louisiana Constitutional provisions and statutes that deal with the division between private and State ownership of land. Other State laws that could be implicated in marsh management activities are those that protect water quality, protect historic and archaeological sites, provide for maricultural activities, and deal with marsh burning. The Louisiana Coastal Resource Program established by the CRMA is administered by CMD. The declared public policy under which the CMD operates is "to protect, develop, and, where feasible, restore or enhance the resources of the State's coastal zone" (La. R.S. 49:213.2). The coastal zone is geographically delineated in the CRMA (La. R.S. 49:213.2, 213.4). Also provided for in the Act are some of the uses and activities in the coastal zone subject to the coastal use permitting requirements and the authority to develop guidelines to further delineate such uses (La. R.S. 49:213.5). Marsh management activities, as defined above, are some of the activities requiring a coastal use permit and guidelines have been developed for use in the initial permitting process as well as establishing conditions for the permit. Among other things these guidelines require that marsh management plans "result in an overall benefit to the productivity of the area," that water control structures result in minimum obstruction of the migration of aquatic organisms and permit tidal exchange in tidal areas, and that impoundments which do hinder normal tidal exchange and aquatic organism migration, to the maximum extent practicable shall not be constructed in brackish or saline areas (U.S. Department of Commerce et al. 1980). Under the guidelines marsh management plans are required to contain marsh management goals; area history; type of habitat; location, construction, and operation of water control structures; a monitoring plan; and non-marsh management activities to be carried on in the plan area. The monitoring plan requires data on water quality, vegetation, land and water ratio, and wildlife so that the effectiveness of the plan may be evaluated. A marsh management CUP is limited to a 5-year term and the monitoring data is used as a factor in deciding whether or not to renew the permit. At' present CMD is formulating a new set of guidelines to be used in marsh management permitting. These will become department-wide guidelines to be used by all agencies in the Department of Natural Resources (DNR). 372 The Louisiana Constitution, Civil Code Articles, and statutes that deal with State ownership of land have the potential for greatly affecting marsh management activities. These laws provide that the State of Louisiana owns as public holdings the running waters, the waters and bottoms of naturally navigable water bodies (rivers, streams, bayous, and lakes), the territorial sea, the seashore, (La. Civil Code Article 450) and the banks of navigable lakes (Miami Corporation v. State 186 La. 784, 173 So. 315, 325(1936)). State public holdings are analogous to those owned under the common law doctrine of public trust. The State owns public areas for the benefit of the people so that its "ownership" is more of the nature of guardianship and as such, they are inalienable, imprescriptible, and exempt from seizure (AN. Yiannopoulos, Louisiana Civil Law Treatise, Vol. 2 §34). Although it seems to have been widely ignored by the Courts, Louisiana law also provides that the State owns the waters and beds of all rivers, streams, lagoons, lakes, and bays whether or not navigable that were not under direct ownership as of 12 August 1910 (La. R.S. 9:1101). In addition, Louisiana claims ownership of the waters, beds, and shores of the Gulf of Mexico and "arms" of the Gulf and the lands covered by those waters at high tide within the State's boundaries (La. R.S. 49:3). An arm of the sea has been defined as "a body of water located in the immediate vicinity of the open gulf that is directly overflowed by the tides" (AN. Yiannopoulos, Louisiana Civil Law Treatise, Vol. 2 §45). The Louisiana Constitution prohibits the alienation of the beds of navigable water bodies except for reclamation of eroded land by the affected landowner (Article IX §3 of the Louisiana Constitution of 1974) which must be permitted by DSL (La. R.S. 41:1702). The banks of navigable rivers, streams, and lakes are defined as the area of land between ordinary low and high water marks (La. Civil Code Article 456). The seashore is the land between the low water mark and the mark of the highest winter tides (La. Civil Code Article 451). The banks of rivers and streams may be and usually are privately owned but in the case of navigable rivers and streams such ownership is subject to the right of public use (La. Civil Code Article 456). The beds of non-navigable rivers and streams belong to the riparian land owners (owners of the land adjoining the river or stream) (La. Civil Code Article 506) and the beds of non-navigable lakes are subject to private ownership. Again this may be limited to those beds privately owned before 12 August 1910. Louisiana law defines the buildup of sediments or accretion that is formed successively and imperceptibly on the bank of a river or stream as alluvion. The same law defines land exposed by water receding imperceptibly from a bank of a river or stream as dereliction. In either case the newly formed land belongs to the riparian landowner (La. Civil Code Article 499). This right of acquiring alluvion or dereliction does not exist on the seashore or the shores of lakes (La. Civil Code Article 500). Therefore, if alluvion or dereliction occurred on the seashore or the shore of a navigable lake, the newly formed land would belong to the State. Conversely when the shore of the sea or a navigable lake, river, or stream erodes, the newly formed water bottom becomes property of the State unless the owner of the eroded land takes the statutorily required steps to reclaim it (Miami Corporation v. State 186 La. 784, 173 So. 315, 325 (1936)). Such reclamation efforts can be very expensive and are not often done if the erosion is extensive. Artificial water courses (canals) are public water bodies subject to public use when constructed on State owned land (AN. Yiannopoulos, Louisiana Civil Law Treatise, Vol. 2 §47). When canals are constructed by public authorities on private land pursuant to a right of way servitude, they are private holdings subject to public use (Hunter Co. v. Ulrich 8 So. 2d 531 (1942)). Canals constructed on private land for private purposes have been held to be private with no right of public use (Vaughn v. Vermilion Corp. 444 U.S. 206). Therefore, if the owner of a private canal decided to exclude the public from using the canal he could erect barricades to keep out boat traffic. The same right would apply to a non-navigable, privately owned river or stream. 373 This right to exclude the public from privately owned rivers, streams, and canals has been challenged both in court and by legal writers. One theory is that since the State owns all the running waters in public trust, it is illegal for the owners of the bed and banks of these water bodies to deny public access to the water in them (Ketchum 1988). This is a questionable theory as the language relied on in the cited case is dictum (a statement made by the court not necessary for adjudication of the case) and not the holding of the case (Chaney v. State Mineral Board 444 So. 2d 105 (La. 1983)). The theory is also in contravention to other Louisiana cases and opinions by the Louisiana Attorney General's Office (Op. Attorney General 81-785 (1981); Op. Attorney General 81-873 (1981); Op. Attorney General 82-102 (1982)). An alternative theory supporting the right of public access to private canals has been presented in two important cases. In Vaughn v. Vermilion Corp., a Louisiana case, the U.S. Supreme Court held that, under Federal law, the owner of a private canal could deny public access even though the canal was navigable and joined with navigable waters of the United States (Vaughn v. Vermilion Corp. 444 U.S. 206). The court's holding, however, made an exception to this rule: when a private canal diverts or destroys a preexisting natural navigable waterway the canal may be subject to public right of use (Vaughn v. Vermilion Corp. 444 U.S. 209). The holding in Vaughn forms part of the basis for the State of Louisiana's current suit against the Lafourche Realty Company over the closure of the Tidewater Canal System (Summersgill Dardar, et al. v. Lafourche Realty Co., et al., No. 85-1015 (E.D. La. filed 6 August 1985)). The Lafourche Realty Co. (defendant) had obtained a CUP and a §404 permit to establish a marsh management plan by erecting water control structures in a privately owned wetland area undergoing serious degradation from saltwater intrusion. The defendant also obtained a §10 permit from the Corps to erect barricades to control boat traffic through the Tidewater Canal System. The defendant then erected barricades, posted armed guards at them and began selectively denying access to the canal. This canal system had been dug in the privately owned marsh and provided access to the marsh by connecting to natural navigable waterways. It also had been used by the public for many years as a short cut to prime fishing grounds. The blockage of the canal system was ostensibly to prevent vandalism to the water control structures so that the marsh management plan could operate properly (Summersgill Dardar, et al. v. Lafourche Realty Co., et al., No. 85-1015 (E.D. La. filed 6 August 1985)). The State is arguing as part of its case that the construction of the Tidewater Canal System, along with other human activities in the area, has diverted or destroyed the system of natural navigable waterways that had previously existed: the canal system has superceded the natural system. Thus, under Vaughn the public has a right of use which cannot be denied by the defendants (Summersgill Dardar, et al. v. Lafourche Realty Co. et al., No. 85-1015 (E.D. La. filed 6 August 1985)). The water control structures themselves are either on privately owned water bottoms or are constructed on State owned water bottoms in such a way that normal boat traffic can pass. The DSL, therefore, did not initially object to these structures or the barricades. Under the theory mentioned earlier that the State may prevent blockage of any running waters, the barricades and the water control structures would be illegal. The legal issues and technical aspects of State property ownership and public access rights are relevant to marsh management because certain practices associated with marsh management are considered by DSL to be an unconstitutional alienation (divesting or loss of ownership by sale, donation, or other transfer) of State property (K. Morgan, DSL; pers. comm.). Such activities 374 would include deposition of fill on State -owned water bottoms, thereby changing their character to dry land, or emplacement of boat barricades across State owned water bodies, preventing the public's right of access. The use of weirs may be permitted as long as the obstruction does not hinder boat traffic that could normally travel the water body (Morgan, pers. comm.). The owner or operator of the weir, however, is required by DSL to purchase a waterway right of way grant (easement) from the State for maintaining the structure on a State-owned water bottom (La. R.S. 41:1702). The DSL opposes levees and dams for impoundments and water control in State-owned water bottoms, even when associated with marsh management plans (Morgan, pers. comm.). Although DSL has no enforcement authority, it has the authority to comment to CMD, and CMD has denied applications for CUP's based on DSL objections (Clark, pers. comm.). In addition, DSL refers cases to the Louisiana Attorney General Office for enforcement of this prohibition (Morgan, pers. comm.). As mentioned above, Louisiana has always claimed ownership in public trust of the beds of navigable natural water bodies. The State defines "navigable natural water bodies" as a water body susceptible of use as a highway of commerce by customary modes of water transportation as of Louisiana's admission to statehood in 1812, regardless of whether or not it remains so today (Stage v. Aucoin, 206 La. 787, 855, 20 So. 2d 136, 158(1944)). A recent U.S. Supreme Court decision, however, indicated that under Federal law, Louisiana was granted more land in public trust at statehood than just the navigable natural water bottoms to which it claims ownership today. In the case of Phillips Petroleum Co. v. Mississippi, the U.S. Supreme Court decided an issue of State ownership of tidelands by giving a broad interpretation to the doctrine (Phillips Petroleum Co. v. Mississippi, 56 USLW 4143(1988)) that says that all States were admitted to statehood on an equal footing. The Court held that equal footing meant all lands subject to the influence of the tides, whether or not navigable, as well as all other natural water bodies that were navigable were transferred, at statehood, to each State in public trust in its capacity as a sovereign (Phillips Petroleum Co. v. Mississippi, 56 USLW 4143(1988)). As Mississippi had never alienated these non- navigable tidelands and had always claimed ownership to all land under tidally influenced water, the title of Phillips Petroleum, which could be traced back to pre-statehood Spanish land grants, was null and void. The effect of this decision on Louisiana property law has yet to be decided. Some legal scholars theorize that Phillips Petroleum could pave the way for Louisiana to reclaim ownership in public trust to privately owned lands under non-navigable natural water bodies which are tidally influenced (subject to the ebb and flow of the tide) (Yiannopoulos 1988). The reasoning of this theory is that the State of Louisiana, like Mississippi, has never affirmatively alienated the lands in question. This is due in part to confusing definitions under Louisiana law of swamplands subject to tidal overflow and water bottoms subject to tidal ebb and flow; the former of which could be alienated while the latter could not (Yiannopoulos 1988). It is also due to the fact that in the 1800's large tracts of unsurveyed land were sold by the State to private parties. These tracts often contained navigable water bodies and lands subject to tidal influence and the question arises as to whether or not the State intended to alienate them (Yiannopoulos 1988). Alternatively even if it had alienated them, to do so was against the public trust and public policy of the State and therefore such alienations are void (Yiannopoulos 1988). Currently under Louisiana Constitution Article IX §3 which prohibits the alienation of navigable water bodies and under the case of Gulf Oil Corporation v. State Mineral Board 317 So. 2d 576 (La. 75) the State may assert its ownership to navigable water bodies that it has alienated (Yiannopoulos 1988). This would appear to form a foundation for the State to assert its ownership of the non-navigable tidelands that it has alienated, because both navigable water bodies and non-navigable tidally influenced waters were part of the public trust lands given to the State under Federal law. Therefore, the same public policy should apply to 375 navigable water bodies and non-navigable tidally influenced waters were part of the public trust lands given to the State under Federal law. Therefore, the same public policy should apply to navigable water bodies and non-navigable tidelands (Yiannopoulos 1988). Other legal scholars maintain that the Phillips Petroleum decision will have little effect on titles to land in Louisiana because the State did make the conscious decision to alienate the non- navigable tidelands. In addition, legal arguments aside, many argue that when presented with unclear cases of State alienation of tidelands, Louisiana courts would be reluctant for political reasons to overturn long established ownership rights. This, however, should be within the purview of the legislature. The details of these legal theories are too involved for the scope of this discussion. However, the possibility of future far reaching ramifications in Louisiana from Phillips Petroleum should be kept in mind. Of paramount importance to land owners is of course the possibility of losing ownership of land. In addition, the Phillips decision could have an important impact on marsh management. If the State were to assert its ownership of tidelands in areas under marsh management plans it could impose restrictions such as those already mentioned against alienation of State lands. It could also discourage marsh land owners from undertaking marsh management plans if they thought their land actually belonged to the State. The State could ill afford to practice marsh management on all of the newly acquired land. With the possibility of such additional regulatory burdens and financial considerations, the issues presented here will bear close scrutiny in the future. A marsh management plan that includes reclamation of an area of land that had been lost through erosion of the shore or bank of a State-owned water bottom would fall under the statutes dealing with State water bottom management also administered by DSL. A permit for such reclamation is required and a prerequisite for obtaining such a permit is proof of ownership and boundaries of the eroded lands. Permits may also be required for other structural encroachments on State-owned water bottoms such as pilings, breakwaters, and piers (La. R.S. 41:1701-1714). Other Marsh Management Activities Other activities which do not fall within the above definition of marsh management but have been either traditionally associated with marsh management or in some way linked to it may also be regulated. Marsh burning, the use of pesticides, and hunting and trapping will be discussed very briefly while more emphasis will be placed on mariculture and on boat barricades. Marsh burning is often used to prevent plant succession and to promote new vegetation growth. It is supposedly regulated under La. R.S. 56:7, which prevents anyone from setting fires to marshland except the owner who is attempting to improve food conditions for wildlife. Such burning must be done under permit and supervision of the DWF (La. R.S. 56:107). This provision seems to be widely unenforced such that marsh burning is essentially unregulated (W. Vidrine, DWF; pers. comm.). The use of pesticides is regulated by the Department of Agriculture. Some landowners use herbicides to control what are considered "noxious weeds." Another practice, and one that is currently being promoted by the DWF in their Acres For Wildlife Program, is the use of herbicides to increase open water areas in marsh land to improve waterfowl habitat (Vice 1988). Hunting and trapping to harvest the natural resources of marshland and to control destructive animals such as muskrat is considered by many to be a sound marsh management practice. These activities are regulated under the appropriate Wildlife and Fisheries statutes (La. R.S. Title 56). 376 Some of the most controversial practices often associated with marsh management plans are maricultural operations. These operations received much attention after the 1987 session of the Louisiana Legislature when two conflicting bills providing for the establishment of maricultural operations were passed (La. R.S. 56:13,579). La. R.S. 56:579.1 allows DWF to issue a maximum of 10 mariculture permits (La. R.S. 56:579. IB). No permitted area can exceed 8,000 acres and each must be within marsh management areas operating under valid coastal use permits issued by the CMD. It also requires that the permits have a duration of no more than 5 years and that all fisheries used in the operation be "purchased from a legal source." This in effect requires the use of stocked rather than wild organisms. The other maricultural law, La. R.S. 56:13, provided for the DWF to issue "special fish and wildlife harvesting permits" to "owners and operators who filed a marsh management plan" (La. R.S. 56:13). It set no limit on the number of permits, the duration, or the acreage involved, and did not require the use of stocked fish. Both maricultural laws exempted marsh management operators from R.S. 56:329 which prohibits the obstruction of the free passage of fish in any body of water, excepting water control structures or dams for conservation purposes (La. R.S. 56:13, 579.1). Under R.S. 56:13, certain marsh management operators were allowed to place screens on the access routes of their impounded marsh areas in order to trap wild fish. The fish were then allowed to grow within the impounded area and then harvested when they reached a marketable size. This practice raised a storm of controversy when these operators "harvested" red drum which were then protected by closed commercial and recreational fisheries for that species. The DWF was later able to prevent such harvesting of red drum by interpreting R.S. 56:13 in such a way that it did not provide for exemption from rulings of the Wildlife and Fisheries Commission regarding limitations and closures of fisheries (B. Watson, DWF; pers. comm.). This action did not quell the controversy surrounding R.S. 56:13 and it was repealed in the 1988 regular session of the Louisiana Legislature. In the regulatory network there is a seeming conflict between the CMD's permitting of marsh management plans and DWF's permitting of maricultural operations within those areas covered by the plans. CMD does not consider maricultural operations to be a marsh management practice; indeed its policy as set forth in the Coastal Use Guidelines is that the restriction of ingress and egress of marine organisms is to be minimized in wetlands that are not completely impounded (U.S. Department of Commerce et al. 1980). The placing of screens or nets across access routes in wetlands is an activity requiring a coastal use permit from CMD as well as a maricultural permit from DWF. In addition, an owner or operator must obtain a coastal use permit for a marsh management plan as a pre-requisite under R.S 56:579.1 to obtain a maricultural permit. Most of the existing marsh management permits were issued before the passage of the maricultural law and with no consideration by CMD of possible future maricultural operations. If a marsh management plan does not include the use of screens or nets to restrict migration and the owner or operator later uses such devices under the maricultural permit, he would appear to be in violation of his coastal use permit for the marsh management operation. The question is whether the legislature intended to exempt maricultural practices which obstruct marine organism ingress and egress from coastal use permit requirements by the language in R.S. 56:579. IB that begins "notwithstanding any other provision of law to the contrary ..." or merely to exempt it from other wildlife and fisheries laws as the illustrative list would indicate. This is an issue that needs to be resolved because future conflicts between the permitting authority of CMD and DWF could occur, leaving marsh managers who also carry out maricultural operations confused about how to comply with regulatory requirements. 377 Another activity practiced by some owners and operators of wetland areas under the auspices of marsh management is the use of barricades across waterways to block boat traffic, ostensibly to reduce erosion from boat wakes and prevent vandalism to water control structures. This activity would require a §10 permit from the Corps, but if the barricades were placed across naturally navigable waterways, the State Lands Office of DNR would object to it as an unconstitutional alienation of State lands (Morgan, pers. comm.). Their objection would in all likelihood result in the Corps and CMD either denying or withdrawing the respective permits (Ventola, pers. comm.). The current controversy over the Tidewater Canal underscores the problems in this area of the law. CONCLUSION The regulatory and permitting network that affects structural marsh management in the coastal zone of Louisiana is a complex and often contradictory process. The intricacies between the permitting agencies (CMD, DSL, the Corps) and the commenting agencies are designed to safeguard various widely divergent public interest goals. This system can present a confusing front to prospective marsh managers who may feel that they are over regulated. The lengthly process involved in obtaining the required permits has left some applicants discouraged and frustrated with the system. The laws that determine the policies of the regulatory and commenting agencies are also complex and constantly evolving. This evolution is now being significantly influenced by growing awareness of the seriousness of the coastal land loss problem. LITERATURE CITED Ketchum, K. 1988. Waterways of the marsh: marsh management plans and public rights. Tulane Environ. Law J. 1:3-7. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Office of Coastal Zone Management, and Louisiana Department of Natural Resources Coastal Management Section. 1980. Coastal use guidelines 7.5, 7.7, and 7.8. Page 61 in Louisiana coastal resources program final environmental impact statement. Office of Coastal Zone Management, NOAA, and the Department of Commerce, Washington, DC. Vice, E. 1988. Managing your hunting land: expert advice available. La. Sportsman. 6(10):46. Wilkins, T. 1987. TEDs and the endangered species act of 1973. La. Coastal Law. 56:1-7. Yiannopoulos, A 1988. Five babes lost in the tide-a saga of land titles in two States: Phillips Petroleum Co. v. Mississippi. Tulan" Law Rev. 62:1357. 378 50272-101 REPORT DOCUMENTATION PAGE 1. REPORT NO. Biological Report 89(22) 1. Recipient's Accession No. 4. Title and Subtitle Marsh Management in Coastal Louisiana: Effects and Issues -- Proceedings of a Symposium 5. Report Date September 1989 7. Edilora Walter G. Duffy and Darryl Clark 8. Performing Organization Rept. No. 9. Performing Organization Name and Address 10. Project/Task/Work Unit No. 11. Contract(c) or Grsnt(G) No. (C) (G) 12. Sponsoring Organization Name and Address U.S. Department of the Interior Fish and Wildlife Service Research and Development Washington, DC 20240 13. Type ol Report & Period Covered Louisiana Department of Natural Resources Coastal Management Division Baton Rouge, LA 70804 15. Supplementary Notes 16. Abstract (Limit: 200 words) This proceedings is from a symposium "Marsh Management in Louisiana: Effects and Issues" held in Baton Rouge, LA, in June 1988. It provides an overview of issues and strategies surrounding the management of fresh, brackish, and salt marshes in coastal Louisiana to control wetland loss. A wide spectrum of views, opinions, ideas, and case studies are presented from a variety of sources: State and Federal agency personnel, public and private marsh managers, university scientists, consultants, and private citizens. Currently, management of coastal wetlands in Louisiana primarily involves control of water levels and salinities in marshes by weirs. Several case studies are presented to investigate the effects of these structures on marsh vegetation and coastal fisheries. Legal and regulatory issues affecting management efforts are also considered. 17. Document Analysis a. Descriptors b. Identifiers/Open-Ended Terms marsh management coastal Louisiana c. COSATI Field/Group fresh marsh brackish marsh salt marsh wetlands wetland loss fisheries 18. Availability Statement Unlimited distribution 19.Securrty Class (This Report) Unclassified 20. Security Class (This Page) Unclassified 21. No. of Pages vii + 378 22. Price SeeANSI-Z39.18) I. GOVERNMENT PRINTING OFFICE: 1989-663-542 OPTIONAL FORM 272 (4-77) (Formerly NTIS-35) Department of Commerce As the Nation's principal conservation agency, the Department of the Interior has responsibility for most of our nationally owned public lands and natural resources This includes fostering the wisest use of our land and water resources, protecting our fish and wildlife, preserving the environmental and cultural values of bur national parks and historical places, and providing for the enjoy- ment of life through outdoor recreation. The Department assesses our energy and mineral resources and works to assure that their development is in the best interests of all our people. Tne Depart- ment also has a major responsibility for American Indian reservation communities and for people who live in island territories under U.S. administration. U.S. DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE TAKE PRIDE in America UNITED STATES DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE National Wetlands Research Center NASA Slidell Computer Complex 1010 Gause Boulevard Slidell. LA 70458 OFFICIAL BUSINESS PENALTY FOR PRIVATE USE. $300