L5^.66Z-. OJe ^Iz, NOAA Special Report .^<°>^. ^'-^rts O* »■* G ^ The IXTOC I Oil Spill: The Federal Scientific Respons December 1981 U. S. DEPARTMENT OF COMMERCE National Oceanic And Atmospheric Administration Office of Marine Pollution Assessment .^qMMOS^,. I a The IXTOC I Oil Spill: The Federal Scientific Response December 1981 Edited by Craig H. Hooper NOAA Hazardous Materials Response Project Boulder, Colorado UNITED STATES NATIONAL OCEANIC AND Office of Marine DEPARTMENT OF COMMERCE ATMOSPHERIC ADMINISTRATION Pollution Assessment Malcolm Baldrige, John V. Byrne, R.L. Swanson, Secretary Administrator Director COVER PHOTO IXTOC I well on fire, taken September 1979 from the R/V G.W. PIERCE. Copyright© 1979 by Jack E. Barbash. n Contents Page Acknowledgments v Executive Summary 1 Chapter 1 Introduction (Craig Hooper) 9 Transport, Distribution and Physical Characteristics of the Oil Part 1: Offshore Movement and Distribution 13 (J. A. Gait) Part 2: Nearshore Movement and Distribution 41 (Erich R. Gundlach and Kenneth J. Finkelstein Chemical Characterization and Fate of the Oil 75 (Edward Overton) Resources at Risk (Robert Hannah and Charles D. 85 Getter) Research Protection Measures (Robert Hannah) 105 Biological Studies (Charles D. Getter, Geoffrey 119 I. Scott, and Larry C. Thebau) APPENDICES A Beach Profile Stations to Measure Oil Distri- 177 bution and Biological Impact (Erich R. Gundlach, Kenneth J. Finkelstein, Daniel D. Domeracki , and Geoffrey I. Scott) B Marine Cruises (Edward Overton) 183 C Common and Taxonomic Names of Coastal Biota 195 111 NOTICE Mention of a commercial company or product does not constitute an endorsement by NOAA Environmental Research Laboratories. Use for publicity or adver- tising purposes of information from this publication concerning proprietary products or the tests of such products is not authorized. Research reported in this document was funded by and conducted in cooperation with NOAA's Hazardous Materials Response Project, Marine Ecoystems Analysis Program, Long-Range Effects Research Program and P.L. 95-273 Section 6 Financial Support Program. IV Acknowledgments I would like to acknowledge the assistance of the over 200 scientists who performed the work described in this report. The major organizations these people represented are listed in Chapter I. I would also like to acknowledge the efforts of the authors of each of the chapters as they essentially wrote most of the report. There are four people who I am especially appreciative for their efforts in publishing this report: Dr. Robert Hannah of NCAA's Office of Marine Pollution Assessment in Bay St. Louis, Miss., who offered extremely useful ideas on the general organization of the report; Joan Myers, who spent countless hours doing the detailed editing; Rosalie Redmond, who typed, retyped and typed again the entire report as it went through many revisions. Digitized by the Internet Archive in 2012 with funding from LYRASIS IVIembers and Sloan Foundation http://archive.org/details/ixtocioilspillfeOOhoop EXECUTIVE SUnnARY On 3 June 1979, a Petroleos Mexicanos (PEMEX) exploratory well, IXTOC I, blew out in the Bay of Campeche, about 80 km northwest of Ciudad del Carmen, Mexico. The spill, not brought under control until 27 March 1980, became the largest oil spill in history. During the IXTOC I spill more than 200 scientists from a number of Federal and State agencies, academic institutions, and private companies were marshalled to forecast the trajectory of the spilled oil and to give advice on beach processes, danger to living resources, and changing composi- tion and toxic qualities of the petroleum over the several months that much of the oil remained at sea. The following summary describes the numerous operational support activities and scientific studies performed under the purview of the Federal Scientific Support Coordinator. The primary purpose of the physical, chemical, and biological activities described herein was to provide the Federal On-Scene Coordinator (OSC) with timely information concerning the location, toxicity, and potential ecological impact of the oil on the Texas coastline so that mitigation measures could be initiated. These studies did not constitute a comprehensive damage assessment program. Offshore Oil Trajectory Modeling Studies Computer modeling studies in support of the response to the IXTOC I blowout began early in the spill and continued throughout the summer and fall of 1979. Three distinct types of trajectory models were applied. The first concentrated on the regional problem along the Texas coast, providing daily forecasts of the expected movement and spreading of the oil. This information was presented in a format that was available on an immediate basis to on-scene personnel. A second effort was used to describe the long-term prospects for IXTOC I oil movement and define the strategic threat under which the response should be planned. These models provided information useful in scheduling the buildup and shutdown of the larger scale components of the response, those associated with cleanup activities and scheduling of scientific and aircraft personnel. The third type of modeling was a receptor-oriented study that identified threat areas asso- ciated with particular high-value regions. This information was available for the planning of observational programs and the delineation of minimum search areas to be covered. Using these three techniques, the scientific team was able to forecast accurately the pathways the oil would follow from the wellhead through impact on the Texas coast. Nearshore Movement and Distribution As the oil began to reach the Texas shoreline on 6 August 1979 contin- uous beach surveys were undertaken to map its movement and distribution. Throughout the late summer and early fall of 1979, the barrier islands along the south Texas coastline were periodically impacted by oil. Between these periods of impact, storms would often rework the oil and redistribute it along the shore, depositing clean sand over the beached oil or eroding the preshore causing the oil to move into the surf zone. The oil tended to persist longer on shell beaches than fine-sand beaches. There was initially considerable speculation concerning the fate of oil within the nearshore environment. Large mats of sunken oil were often conjectured; however, several diving surveys extending up to 300 m offshore turned up no substan- tial evidence of large quantities of sunken oil in the nearshore zone. The strategy for oil spill defense along the south Texas shoreline was to rely on the barrier islands to absorb most of the oil impact, concentrat- ing containment resources on the protection of biologically productive Laguna Madre. The breaks in this line of defense are inlets and overwashes. The four major inlets (Brazos-Santiago, Mansfield Channel, Fish Pass, and Aransas Pass) were protected by booms and skimmers deployed under direction of the U.S. Coast Guard. Cedar Bayou, a shallow pass between San Jose and Matagroda Islands to the north, was first boomed and then dammed with sand across the inlet. Booms were also placed in Pass Cavallo, still farther to the north, in preparation for the advancing oil. Although the containment operations were not totally effective, espe- cially during periods of adverse weather and at night, there is no evidence of great quantities of oil penetrating the defensive structure. Chemical Characterization and Fate of the Oil The IXTOC I oil spill was unique not only because of its magnitude, but also because of the long interval between the release of oil and its impact on coastal habitats. During this time, many physical and chemical processes acted on the spilled oil. These processes, cumulatively referred to as "weathering," included evaporation, dissolution, emul si fi cation, adsorption onto suspended sediments and detritus, photochemical oxidation, and microbial degradation. These processes altered the original physical and chemical properties of the oil, transforming it into several distinctly different types of petroleum residues. Physical changes included increased viscosity and density (and therefore lessened buoyancy) and the formation of various emulsions and oil residues. Chemical changes included oxidation and degradation caused by photochemical and microbial action. The original oil slick was transformed into oil-and-water emulsions of various composi- tions: sheens, flakes of emulsions, tar balls, pancakes of various sizes, tar mats, and possibly other physical forms as it weathered during its transport in the open gulf. One important aspect of the scientific support effort for the IXTOC I spill included collecting oil samples that could be quickly analyzed to determine both the density and toxicity of the oil for making operational decisions. In addition, a project to take advantage of the research opportuni ties afforded by the IXTOC I spill was undertaken, culminating in a cruise by the NOAA ship RESEARCHER and a contract vessel, the PIERCE, to the well site and then following oil plumes during their northward transect. During the Federal response to IXTOC I, over 1400 samples were collected in the northwestern Gulf of Mexico. Over 1000 additional samples were collected near the well head during the RESEARCHER and PIERCE cruises. Sample collections started in mid-July 1979, before the oil impacted Texas beaches and continued on a limited scale to the summer of 1980. Nine major cruises by research ships or cutters were undertaken for this purpose, together with extensive beach sampling and collection of commercial fishery products. Analysis of the RESEARCHER samples indicated weathering had already changed the composition of the IXTOC I oil by the time it reached the surface. Other physical weathering processes caused the oil to form a "water in oil" emulsion (chocolate mousse) in various forms. Visual obser- vations suggested photochemical weathering of the oil. These transforma- tions were reflected by color changes in the emulsions and by a tendency for a crust to form on the floating mousse. Physical agitation caused larger emulsion pancakes to break into smaller particles known as tarf lakes. These flakes, which ranged in size from several millimeters to several centimeters, frequently contained a heavily weathered outer crust and a less weathered inner material. The chemical characteristics of the inner material often resembled those of fresh oil samples that were collected near the wel 1 head. Resources at Risk A wide variety of environmental resources were at risk in the south Texas area during the IXTOC I incident. Padre Island and the Laguna Madre are known to be one of the most important staging and wintering areas for waterfowl, shorebirds, and colonial waterbirds in the United States. The endangered brown pelican, whooping crane, and peregrine falcon all inhabit this area. Sensitive marsh areas are also found in association with the extensive lagoonal system that provides an important nursery for commercial fish species upon which the Texas fisheries industry depends. Eighteen species of marine mammals and five species of marine turtles are reported to be residents of the offshore area of south Texas; all except one are classified as protected, threatened, or endangered. Resource Protection Measures The blowout of the IXTOC I well in the Bay of Campeche was unique from the standpoint of resource protection, since the time between the initial blowout and the subsequent impact of U.S. waters was approximately two months. This allowed a protracted period that is not usually available in spill situations to plan and prepare the response. Measures taken to mitigate environmental damage by the scientific team included the following general activities: • Identification and prioritization of sensitive areas using ground surveys and remote sensing. Tidal, wind, and bathymetric studies in support of boom placement efforts. Fishery resources protection through a voluntary shrimp inspec- tion program to ensure consumer confidence as well as slick location broadcasts to minimize lost fishing time and losses of catch and gear. A monitoring program to detect the presence of hydrocarbons in key shell fishing areas. Establishment of bird, mammal, and turtle cleanup stations along the Texas coast. Testing of dispersants and biological agents to determine the feasibility of their use to break up and degrade the oil as it reached U.S. waters. Studies to determine the most environmentally sound cleanup and disposal techniques. Biological Studies Numerous biological studies were conducted during the IXTOC I spill to monitor changes in dominant, important, or indicative species. These studies were undertaken to indicate the onset of measurable biological changes, so that to the extent practicable, mitigation measures could be initiated. A secondary objective was to provide some baseline information for any subsequent damage assessment studies. The results of these studies show, however, that in general the oil had only a minimal impact on local biota. This is no doubt influenced by the presence of the coastal barrier islands which largely prevented the oil from entering the more biologically sensitive lagoonal system. The biological program consisted largely of two general types of studies: field studies and laboratory analyses. The results of all over- flight population census, remote sensing flights, beach surveys, site intensive impact studies, as well as offshore cruises, made up a field study data base. A battery of toxicological tests comprised the laboratory data base. The results of these studies are outlined by habitat type. Inlets and Lagoons IXTOC I oil failed to impact large areas of marshlands. Small amounts of oil that entered inlets appeared to have little or no measurable effects on the productivity of marshes and inlets. This was observed both through direct observations as well as through physiological bioassays on representa- tive phytoplankton and seagrasses. • Sand Beaches During the period of heaviest oiling of beaches, population densities of wading and shorebirds remained low. Substantial increases in bird populations occurred after the natural removal of oil from beaches by tropical storms and correlated with the influx of newly arriving migratory bird species. Birds avoided oiled portions of beaches and moved to other habitats during periods of heaviest oiling. No more than 10 percent of the bird population using beaches was oiled at any time and few carcasses were found. Physiological bioassays using weathered IXTOC I oil on surrogate species related to the peregrine falcon and the whooping crane concluded that neither species would be affected by the consumption of oil -contaminated prey. Monitoring of infaunal populations at oiled beaches indicated measurable reductions in the population size. Total population densities were signifi- cantly reduced in the lower intertidal zone and in the second bar and trough of subtidal habitats. Numbers of crustaceans (mole crabs and amphi- pods) were significantly lowered in both zones following the spill. It was difficult to distinguish the effects of the oil spill from natural factors, especially storms and natural population variations. Results of acute (96 hour) toxicity tests, exposing IXTOC I oil to dominant infaunal organisms, indicated no significant mortality. These results support the findings of field studies, thus suggesting that IXTOC I oil was not acutely toxic to beach fauna, although sublethal effects (significantly decreased respiration rates and avoidance behavior) were observed in oil-exposed mole crabs. Results of acute toxicity tests, conducted on subtidal amphipods and zooplankton, suggested that IXTOC I oil was not toxic to these species. Offshore and Nearshore Environments Bioassay and toxicity tests of dominant and commercial species were conducted in addition to observations made during cruises. Toxicity tests conducted on adult redfish, seatrout, and brown shrimp indicated that IXTOC I oil was not acutely toxic to these commercially important fisheries species. However, high mortalities were observed in larval and juvenile fish species tested. Toxicity was greatest in larval redfish and many deformities in eggs and larvae were observed. Toxicity tests on redfish larvae indicated that the oil -accommodated seawater (water soluble fraction plus small oil microdoplets of mousse) fraction was more toxic than the water soluble fraction of the IXTOC I oil. Additional redfish larval tests indicated that the mousse fraction was nearly 100 percent toxic. The results of the studies may suggest that toxicity to redfish larval may be due to smothering rather than chemical toxicity per se, since the mousse and oil -accommodated seawater fractions were more toxic than the water soluble fraction. High mortalities were also observed in juvenile seatrout. In open water situations, adult organisms may have been able to avoid contaminated areas; however, impacts to eggs, larvae, and juveniles would likely have occurred in heavily oiled areas. All toxicity tests were conducted using the mousse collected by the U.S. Coast Guard vessel POINT BAKER, near Brownsville, Texas. These samples did not contain high concentrations of many aromatic oil fractions such as napthalene, methyl napthalene, dimethyl napthalene, and trimethyl napthalene. These compounds have been shown to be acutely toxic to many adult marine organisms; reduced toxicity observed in tests with adults may have resulted from the very small concentrations of these compounds in the samples collected by the POINT BAKER. The effects of IXTOC I oil on marine mammals are preliminary at this time. General indications are that no observable effects to marine mammals were found during the different research cruises conducted at various times during the spill. Initial findings indicated that sea turtle mortalities observed were possibly oil-related. However, preliminary findings suggest that incidences of mortality were rare and isolated. Conclusions In summary, field studies suggest that IXTOC I oil may have caused: (1) significant population shifts and avoidance by major wading and shore- bird species at heavily oiled beaches; (2) subtle reductions of infaunal population densities throughout the intertidal beach habitat, with signifi- cant declines occurring only in the lower intertidal zone and the second bar and trough of subtidal habitats; major population declines in two species of crustaceans (mole crabs and amphipods); (3) minor impacts to marsh vegetation; and (4) minor impacts to marine turtles and mammals. However, it was difficult to distinguish the effects of spilled oil from effects from natural factors such as tropical storms, seasonality, and normal population variation. 6 Laboratory studies further indicated that: (1) acute exposures of dominant beach infauna such as mole crabs, surf clams, and polychaete worms to the oil -accommodated seawater fraction were not acutely toxic, although significant sublethal physiological effects and avoidance behavior were observed in mole crabs; (2) acute exposures of subtidal amphipods and zoo- plankton to the oil -accommodated seawater fraction were not toxic; (3) acute exposures of redfish larvae to the oil -accommodated seawater, water soluble fractions, and mousse fractions were toxic, with highest toxicity being observed in the mousse and oil -accommodated seawater frac- tions (rather than the water soluble fraction); (4) acute exposures of seatrout to the oil -accommodated seawater fraction resulted in significant toxicity in juvenile fish, but no toxicity in adult fish; and (5) acute exposures of brown shrimp to the oil -accommodated seawater fraction were not toxic. Laboratory studies indicated that IXTOC-I oil was not acutely toxic to the adult marine organisms tested. These laboratory findings tend to support results from field studies, which indicated that IXTOC I oil caused only limited impacts to beach infauna and other marine organisms. Results of subtidal amphipod and zooplankton toxicity tests were inconclusive, in that both species were resistant to low concentrations of oil tested. However, effects of higher concentrations than those tested are unknown. 1 INTRODUCTION Craig Hooper Hazardous Materials Response Program, NOAA, Boulder, Colo, Early in the morning of 3 June 1979, a Petroleos Mexicanos (PEMEX) exploratory well, IXTOC-I, blew out in the Bay of Campeche. The well was located about 80 km northwest of Ciudad del Carmen, Mexico. The IXTOC-I spill soon surpassed the 7.6 million gallons lost by the ARGO MERCHANT in December 1976, and within a few months became the largest oil spill in history, eclipsing the 68 million gallons of oil spilled by the AMOCO CADIZ near the coast of Brittany, France, 15 months earlier.* The blowout contin- ued for over 10% months until the well was finally brought under control on 27 March 1980. This report is limited to the operations and scientific studies per- formed under the purview of the Federal Scientific Support Coordinator (SSC) and the NOAA Hazardous Materials Response Project. The SSC is charged with gathering and coordinating scientific information and advice for the ♦Estimates vary widely on the total amount of oil spilled. PEMEX estimates vary from 30,000 barrels a day at the height of the spill to about 4,000 barrels per day in November after the injection of steel balls reportedly reduced the flow rate. Jerome Milgram of MIT visited the well in October, and he estimated that as much as 50,000 barrels a day could be flowing from the well. Federal On-Scene Coordinator (OSC) who has charge of the overall response effort. This report is limited to the federally funded studies conducted on the impact of the IXTOC I oil on the Texas coastline; it does not deal with the ecological impact of the spill in Mexican waters. Neither does it discuss the results of the NOAA/BLM damage assessment program initiated after the blowout was controlled, nor does it cover the specifics of the U.S. Coast Guard cleanup effort. Those readers desiring additional informa- tion in the area are referred to the Oil Spill Intelligence Special Report on IXTOC I 4 January 1980 and the U.S. Coast Guard report describing the overall Federal response effort. Background on NOAA's Hazardous Materials Response Team At the time of the ARGO MERCHANT oil spill near Nantucket Island in December 1976, a research team of scientists from the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Coast Guard (USCG) undertook a limited research project designed to describe the movement and fate of the oil released by this tanker. This was a first-step in assessing the ecological effects of the spill. Many other Federal agencies, state organi- zations, and academic groups were drawn into the work. During this effort, it became apparent that forecasts of the oil's movement and scientific chemical and biological studies could be of considerable assistance to the OSC, who has the responsibility for preventing and combatting such incidents. Therefore, after the ARGO MERCHANT, NOAA established the Hazardous Materials Response Project to provide operational scientific advice to the Federal OSC during oil and toxic chemical spills in the marine environment. Head- quartered in Boulder, Colorado, this group has the capability of bringing together the talents of a wide range of experts from Federal, state, and local agences, as well as universities and the private sector. These experts have been called upon during numerous spills around the coast of the United States, and have also been requested to lend their assistance at foreign spills, most notably during the AMOCO CADIZ disaster in 1978. The scientific response teams are made up of members from several Federal and state agencies, and from universities and private companies as well as from the various components of NOAA. During the IXTOC-I spill more than 200 scientists from a number of agencies and academic institutions were marshalled to forecast the trajectory of the spilled oil, and to give advice on beach processes, danger to living resources and changing composi- tion and toxic qualities of the petroleum over the period of several months that much of the oil remained at sea. The following is a list of the major organizations that participated in the scientific response to the IXTOC-I spill: 10 » Federal agencies: -United States Coast Guard -Environmental Protection Agency -U.S. Department of Interior, Bureau of Land Management, Fish and Wildlife Service -U.S. Geological Survey -National Park Service -Food and Drug Administration -National Oceanic and Atmospheric Administration -United States Navy State of Texas Agencies -Department of Health -Parks and Wildlife Department -Department of Roads -Department of Transportation Universities -Corpus Christi State University -University of New Orleans -Texas A&M -University of Texas, Institute of Marine Sciences -Woods Hole Oceanographic Institute Private Contractors -Coastal Ecosystems Company -Computer Sciences Corporation -Ecology and Environment, Inc. -Energy Resources Company -Research Planning Institute -Science Applications, Inc. -SRI International -USR Company The following report summarizes the numerous operational support activities and scientific studies performed by the above organizations under the purview of the Federal Scientific Support Coordinator. It should be emphasized that the primary purpose of the physical, chemical and bio- logical activities discussed herein was to provide the Federal OSC with timely information concerning the location, toxicity and potential ecological impact of the oil on the Texas coastline so that mitigation measures could be initiated. 11 TRANSPORT. DISTRIBUTION. AND PHYSICAL CHARACTERISTICS OF THE OIL Part I: Offshore Movement and Distribution J. A. Gait Physical Processes Support Group, NOAA, Seattle, Wash. The following sections will describe the approach that the Physical Processes Team, a component of the NOAA/Hazardous Materials Response Team, undertook to monitor, map, and simulate the movement of the IXTOC I oil; the problems encountered; and the results obtained. A wide variety of physical processes each took its turn working on the spilled oil. The scale on which oceanographic processes affected the spilled oil was truly oceanic, and the sequence of meteorological patterns, including tropical storms, created considerable challenge. Although the physical processes studies used standard techniques of computer modeling, mathematical analysis, and geophysical observations, the actual size of the IXTOC I effort had the catalytic effect of forging these together in a number of new and useful ways. The result was a more continuous and compre- hensive trajectory study than has been available for any major spill. 13 INITIAL TRAJECTORY RESPONSE ACTIVITIES In any spill trajectory study it is necessary to have estimates of the transport processes affecting the pollutant. The IXTOC I case required, among other things, current and wind patterns for the Bay of Campeche. Upon the initial request for trajectory information on June 12, a search for relevant oceanographic data began. Within a few hours, a research paper (Nowlin, 1972) was located describing circulation in the southwest Gulf of Mexico. A call to the National Weather Service offices in Suitland, Maryland, produced estimated winds for Campeche Bay for 3 June through 13 June. Concurrently, National Ocean Survey chart No. 411 was digitized for use in OSSM (On-Scene-Spill-Model) (Torgrimson and Gait, 1979). With this much preliminary information, it was possible to begin looking at trajectory scenarios. Within 10 hours of the original phone request, two trajectory experi- ments had been run with these data. The results suggested that the spilled oil would initially drift west to west~northwest under the combined influence of the currents and winds. Once it reached the vicinity of the Mexican coast between Cabo Rojo and Tampico, it would be transported north with the coastal currents playing a dominant role. There was also an indication that some fraction of the oil could split off from the main body and move south along the Mexican coast in a circulation feature identified as the "Campeche gyre" (Figure 2.1). Using cl imatological wind data (U.S. Navy Marine Climatic Atlas of the World, Volume 1, North Atlantic Ocean) to extend the model runs, we found that these trajectory experiments suggested that oil might initially appear in U.S. waters offshore in early July and make its first U.S. landfall near Matagorda Bay in the third week of July (Figure 2.2). These results, along with a list of caveats, were forwarded to the Regional Response Team. These initial trajectory results did identify a threat to U.S. waters, but also a number of weak links in the data. These results also pointed out several critical circulation and wind features that appeared to have fundamental roles to play in the movement of the IXTOC I oil. EARLY DATA GAPS: DEVELOPING A DATA BASE The circulation feature identified as the Campeche gyre can be clearly seen in the data presented by Nowlin (Figure 2.1). It is an elongated (east-west), closed circulation pattern that is generally situated over the southwestern section of the Campeche Bank. The center of its circulation is on the Bank approximately at the location of the IXTOC I well. With this much information, it became obvious that the details of this flow may well be significant for the trajectory problem. For example, if the center of the gyre were to shift slightly to the west, the effluent from the well would initially follow a northward-flowing current, while a shift of gyre to the east would result in an initial transport to the south. 14 Figure 2.1 Dynamic topography of surface relative to 1000 - dB Surface: Alaska Cruise 1-lA, 2-lB, and 3-lC, 11 April - 21 August 1951. (After Austin, 1955; and Nowlin and McLellan, 1972). 15 WEST SIDE OF THE GULF OF MEXICO 15/ 7/79 0: 0 CST LATITUDE 29 54.0 LONGITUDE 98 30.0 91 171.3 KM LATITUDE LONGITUDE 18 .0 85 32.0 Figure 2.2 Initial trajectory estimate produced 10 hours after major notification. 16 Another important detail associated with the Campeche gyre is the extent and shape of its western edge. The position of this southerly flowing segment of the gyre would control onshore transport toward the Mexican coast, thus determining where the IXTOC oil might first be expected to impact the coastline. In addition, the extent and strength of the western edge of the gyre might control the amount of oil recirculated south along or toward the Mexican coast versus the fraction of the oil that would be transported to the west, reaching the Mexican Coastal Current thus moving north with a potential threat to the U.S. (Figure 2.3). A second data area that appeared to be significant to the trajectory studies related to the details of the northward-flowing Mexican Coastal Current itself (Figure 2.3). This current clearly would play a major role in the transport of oil toward the U.S. It was also obvious that our initial understanding and descriptions of the currents in this area were inadequate. The speed and width of the current, as well as its persistence and possible branches, would all be relevant factors in trajectory studies. As these data gaps were identified, we increased our data search to try and find further background information. One major source of regional information turned out to be material resulting from Bureau of Land Manage- ment (BLM) studies of the offshore Texas region. These studies were initially conducted to develop background information for environmental impact studies associated with Outer Continental Shelf (OCS) gas and oil development. Included in these data sets were the results of a number of current studies that used drift cards and current meters as well as hydro- graphic data. As useful as this information turned out to be, it covered only the lexas coastal region and did not extend down along the Mexican coast, so a broader coverage of data was essential. A second source of data came from the current study work and numerical modeling done by the NOAA/Atl antic Oceanographic and Meteorological Labora- tory (AOML). These studies used the basic Geophysical Fluid Dynamics Laboratory's (GFDL) general circulation model (Bryan 1967) to look at the currents within the Gulf of Mexico. This detailed study included seasonal variations in the wind and represented a full annual three-dimensional circulation pattern for the entire Gulf of Mexico. This study gave valu- able information for the deep waters of the gulf, although its scope was not such that it provided sufficient resolution over the Continental Shelf. A third very useful data set was located in a Texas A & M University Master's thesis by Alberto Mariano Vazquez de la Cerda (1975). This re- searcher had access to data obtained during a number of hydrographic cruises along the Mexican coast which specifically covered the Mexican Coastal Current. As such, it greatly extended the earlier work done by Nowlin (1972) and explained a number of significant features. In particular, these data and de la Cerda' s analysis made it clear that the Campeche gyre was limited in its western and northwestern extent by the topographic features associated with the Campeche Bank. This meant that oil moving from the well would have a tendency to move to the southwest along the edge of the Campeche Bank and was not likely to move directly west into the deeper waters of the Gulf of Mexico. 17 Figure 2.3 Representation of flow patterns significant to the movement of oil into U.S. waters. 18 The analysis by de la Cerda pointed out a number of features of the Mexican Coastal Current between Cabo Rojo and Tampico. At this point, there was considerable evidence that the current behaved in some ways analogous to a western boundary current such as is seen off the east coast of Africa. In addition, this study identified a small coastal recirculation feature, in the vicinity of Tampico, that formed a counterclockwise eddy inside the Mexican Coastal Current. This feature had the potential to move oil inshore and recirculate it back toward Cabo Rojo and thus decrease the threat to U.S. coastal waters. A fourth additional information set was uncovered in a paper by W. Sturges and J. P. Blaha (1976). They hypothesized that the controlling dynamics for the Mexican Coastal Current were, in fact, similar to those that controlled the Gulf Stream and the summertime development of the Somali Current. The strength of the current is related to the large-scale curl of the wind stress over the Gulf of Mexico. The seasonable variations of the curl of the wind stress for the Gulf of Mexico are known from a statistical point of view, being seen as a biannual pattern with maximas in the summer and winter and minimas in the fall and spring. Given the scale information from de la Cerda' s thesis and the temporal correlations with large-scale wind patterns provided by Sturges and Blaha (1976), we began to get a better understanding of the transport processes associated with the Mexican Coastal Current. As our study accumulated additional information about the IXTOC I transport processes, we also accumulated additional questions that needed to be answered. In particular, there was a significant concern that oil might be moving north or northeast across Campeche Bay to a region where it could become entrained in the Loop Current through Yucatan Strait and, in that way, be carried to the coast of Florida. This supposition needed to be checked and, therefore, the data sources that we had, particularly the time-dependent AOML general circulation models, were examined in considerable detail to study the possibility of oil moving to the northeast. EARLY OBSERVATIONS During the early part of the IXTOC I spill event, actual observations of the oil distribution and leak rate available to U.S. scientists were minimal. It was impossible to determine what fraction of the oil was actually evaporating or what fraction of the discharge was actually oil rather than gas. There was also considerable question concerning the quantity of hydrocarbon that was burning. Reports of cleanup and recovery activity were sketchy at best. For these reasons, initial modeling work hypothesized a continuous release rate of oil and no weathering or burning. The early observations that were available from the IXTOC I site (even though they were quite meager) played an important role in setting up our initial response to the spill event. In about the third week of June, a U.S. observation team went to Ciudad del Carmen and obtained a few first- hand descriptions of the well site and the form of the oil in the vicinity 19 of the blowout. These observations described the oil distribution in the immediate vicinity of the well, but added no information about the far field, i.e., distances beyond a few tens of kilometers. According to reports at that time, the actual distance that oil extended from the well was quite small. In addition to observations from the on-scene U.S. observers, the Mexican government was also carrying out overflights. The results of these overflights began to be relayed to the Physical Processes Team on 28 June. The distribution of the oil released from the blowout was also available from a number of satellite images available from GOES, TIROS, and ERTS. The GOES imagery, available on a regular basis, was particularly useful for determining the direction of the oil plume from the well site. The satellite information was relayed to the Physical Processes Team directly from the Miami Satellite Center. These data were then compared with the computer simulations. During the third week of the spill, it became obvious that the GOES imagery was unable to show the actual extent of the oil, because only the very thickest oil appeared on the imagery. At the same time, all of the computer simulations indicated that the oil should extend much farther (by a factor of five) than was shown by the GOES imagery. The computer scenarios were rerun using the most conservative estimates of winds and currents that were available; even accounting for phenomenally high evaporation rates, the oil should have gone farther than was being reported or observed by GOES. Results of the computer experiments suggested that, by three weeks, the oil should be extending to the coastal area in the vicinity of Veracruz (Figure 2.4). Additional studies of TIROS satel- lite images were particularly informative about this problem. At first, the TIROS satellites identified suspected oil distribution by means of a reduction of the glitter from the ocean in imagery taken at very high sun angles. The idea was that thick oil would suppress the wave action and thus reduce the glitter seen by the satellites. Under these conditions, the oil slick might appear as a dark patch in a brighter image of the ocean. During the last week of June, prompted by computer predictions that had the oil far in advance of the position shown by the high-sun-angle TIROS images, a more detailed look at low-sun-angle images was suggested. A representation of this is seen in Figure 2.5. In the original low-sun- angle image, the oil was surmised to appear as lighter spots in a darker ocean, caused by the increase in albido from the surface oil film. Thin oil on the ocean was anticipated to take on a grayish appearance that would stand out as lighter than the darker blue background water resulting from the increased reflectivity of the oil film. Contrasted to the high-sun-angle image, there would have to be sufficient oil to actually suppress small gravity waves, in the low-sun-angle images it would only be necessary to have sufficient oil concentrations to reflect more light than the ocean. Thus, the low-sun-angle images were expected to indicate much thinner oil concentrations than the higher sun-angle images. 20 HEST SIDE OF THE GULF OF MEXICO 1/ 7/79 0: 0 CST LATITUDE LONGITUOE P8 29 54.0 9 8 30.0 94 «c 0« 88 86 Mill Mill Mill M 1 M I 1 II 1 lllll[ II II 1 1 1 iir J HI Ml Ml |l II II II ^ [MM MUM M M 1 1 III 1 if 1!^ 1^ IJ 1 1 1 1 II 1 II M 1 M Mill 1 1 I 1 1 \r nr' LLI 111 IT I I If I I I 1 1 1 u 1 ip 1 iL 1 1 Brov 1 141 vnsville 1 1 1 ll 1 1 11] iriir I J. Lil i 1 1 -LLil ! . : i 1 j 1 1 1 ' i 1 ; 1 ; ■| i ^ ' 1 i i i 1^ 1 1 1 1 I'll I'll i ; [T M 1' M 1 II 1 1 1 i! 1 1 1 1 II 1 1 IMIM Ml m ^ 1 i 1 fi i 1 1 1 1 1 1 1 1 1 1 1 If 1 1 1 Mill II M III M 1 1 II 1 1 i II II l{ 1 II 1 1 1 1 1 1 iJ 1 t MM MIL Ml ••%i4!*^ * . fi 1 1 1 1 1 1 1 1 I 1 1 1' 1 1 1 illiiiiilliii!^ MINI MINI Mill 1 1 1 M l[ Mill Mill 1\ 5»» II 1 M M 1 M M 1 M kd 1 |l 1! I| [1 1 1 _|l 1 M II II ll'l 1 1 1 1 1 MM 1 M 1 111 n 1 1 II 1 1 II II 1 1 MM 1 1 1 1 1 1 1 III Ml 1 171 .3 KM LATITUDE LONGITUDE 18 .0 85 32.0 Figure 2 4 Computer-generated scenario for the first of July usina con- servative estimates for wind and current transport. ^ 21 WEST SIDE OF THE GULF OF MEXICO 18Z 17 JUNE 1979 MIAMI SESS LATITUDE LONGITUDE P8 29 54.0 98 30.0 9& M II III II 1 M[ Mill II 1 in jnim III H 1 M 1 1 1 ^LMll Mill 11^ 1^ U 1 1 1 1 Mill II 1 lip ;;;i;i^ \\r LU \f M 1 1 i 1 Brownsville m 2tf \\\ 1 l| ir 1 Mil 1 Mill 1 i 1 ■ t ' i : ! i _ iiliili Yl 1 1 i ' i ! ; [T 1 ii; 1 M 11 i, 1 Mi 11 1 11 II 1 1 iiiiiiiiiii \k ',] fi 1 1 M M i j II M Mi II i MMlllillMiM Ml 11 jiM II 11 II III 11 iiii Hill 1 III r i M 1 1 1 1 MMIlL Ml LIGHT 1 Ml ll 1 >|£AV ^ /• llllljllllllill Mill III MMIII Mill IIMIiilir Mill iiiiii;m ll ■ F 1 i 1 1 1 ' i i z» M M 1 1 1 II I i 1 M 1 1 1 1 II 1 M 1 II 1 1 1 1 [ll II 1 1 r\ M f 1 1 M 1 II 1 1 1 II 1 Mill III llliiil 1 1 11 1 II i[ Mill II 1 1 IJ Kill 1 Ml 1 i L |M M M M M 1 M 1 M MINI MM Ml 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I 1 1 II 1 1 1 I 111 r/i.j) KM LATITUDE LONGITUDE 18 .0 85 32.0 Figure 2.5 Representation of oil distribution on 17 June 1979 as seen from low angel TIROS image. 22 The 17 June image suggested that the oil extended west-northwest and then trended to the west-southwest approximately following the edge of the Campeche Bank. At that time, the oil appeared to extend as far west as longitude 95, which put it three-quarters of the way from the well site to Veracruz. The independent agreement of the initial computer experiments and this satellite image was very encouraging. In addition, this informa- tion tended to corroborate the findings suggested in de la Cerda's thesis, which suggested that the circulation along the edge of the Campeche gyre, and in particular the western edge of the Campeche Bank, was controlled by bathymetry, and that an excursion of oil directly west across the bank and then into deeper waters of the Gulf of Mexico was unlikely. Armed with the TIROS satellite imagery and the initial trajectory experiment results, we began the first extensive U.S. mapping effort. The plane (a NOAA P-3) was scheduled to spend 4 or 5 hours over the Bay of Campeche, covering the plume that was expected on the basis of this infor- mation. On 3 July, the NOAA P-3 first encountered oil just north and east of Veracruz and subsequently confirmed that the oil leaving the well site was moving parallel to the northeastern edge of the Campeche Bay, and its initial approach to the coastline would occur in the immediate vicinity of Veracruz. Figure 2.6 shows the full extent of the oil distribution dis- covered on 3 July. There were no indications that significant amounts of oil were moving north or northeast into the gulf from the well head. Corroboration of the observations on 3 July, strengthened the original assumption that the key to the transport of oil into U.S. waters rested with the dynamics and characteristics of the Mexican Coastal Current. Immediately after the first NOAA P-3 flight on 3 July, new requests were made for additional overflight coverage of the Mexican coastal region between Brownsville, Texas, and Veracruz. Such flights were quickly under- taken by the State of Texas Department of Transportation, the U.S. Coast Guard, and NASA. In addition, a research cruise was planned, using a Coast Guard cutter, with the objective of better defining the Mexican Coastal Current. With this updated data base, continuing numerical experiments suggested that oil would be transported north along the Mexican coast and would possibly impact the U.S. coastal region by late July or early August. A Federal response effort was consequently established with the Hazardous Materials Physical Processes Team joining the Scientific Support Coordi- nator's staff for direct on-scene support. The Physical Processes Team immediately began supplying the output from various computer scenarios for analysis and consideration by the Scientific Support Coordinator. The Coast Guard Cutter VALIANT departed Galveston on 16 July enroute to the region on the Mexican Coastal Current. Objectives for the cruise were to (1) find the heavy leading edge of the oil, (2) obtain oil samples, (3) map the large patches of oil that had been seen in previous Coast Guard overflights; (4) document the spatial scale of the Mexican Coastal Current using XBT's (expendable bathythermograph); (5) investigate the size and 23 \ \ V«rficri« Miami 1 1 1 1 0 1 1 Miles i 1 300 1 1 500 Coatzacoalcos Kilometers Figure 2.6 Gait/Kennedy overflight 3 July 1979 showing distribution of oil as seen from the NOAA P-3 aircraft. 24 extent of the hypothesized counterclockwise recirculation off Tampico (Figure 2.3); and (6) obtain some direct measurements of the speed of the Mexican Coastal Current. All six of these objectives were met. A very heavy concentration of oil was mapped and sampled offshore of Cabo Rojo. A number of cross-shelf XBT transects were carried out which delineated the axis of the Mexican Coastal Current. A counterclockwise circulation off Tampico was seen to extend some 25 km offshore, and direct measurement with Richardson dye probes indicated the strength of the circulation patterns. The maximum speed associated with the Mexican Coastal Current occurred some 50 km offshore and was about 1 knot. The counterclockwise circulation off Tampico was expected to recircu- late oil that was nearshore and thus move it in toward the Mexican coast rather than allow it to continue farther north. This, then, suggested that the maximum threat to U.S. waters would come from oil concentrations that were some 50 km offshore near either Tampico or Cabo Rojo. When the U.S. Coast Guard Cutter VALIANT returned, this information was incorporated into updates of the trajectory scenarios and revised the estimates for the arrival of IXTOC I oil in U.S. waters. These studies showed that oil could be expected in the Brownsville region in the first week of August. ROUTINE OPERATIONS As the IXTOC i oil approached the Texas coastal region, more detailed estimates of its movement and spreading assumed particular interest to the on-scene response personnel. To provide these personnel with a more direct flow of information from the modeling efforts, we adapted the on-scene spill model to a tactical mode. These studies focused particularly on the Texas coastal region between Brownsville and Matagorda Bay. Three funda- mental elements went into these numerical experiments, which were updated every few days. The first element was the initial or present positioning of the oil. Daily overflights by the U.S. Coast Guard and NOAA supplied this informa- tion, and maps were available a few hours after the return of the observers. Each evening, these maps were presented in the debriefing that took place for all response personnel. The second element involved in the trajectory study was the definition of the coastal currents for the Continental Shelf region along the Texas coast. The estimates of these currents came from a variety of methods that will be described in more detail below. The third element to go into the trajectory study was the forecast of local winds over 48-hour or 72-hour periods. These data were provided as part of a special analysis by the National Weather Service on-scene fore- caster. 25 Texas coastal surface currents played a significant role in the move- ment of oil. The predominant summer flow appeared to move northerly along the Texas coast, but this northern progression of the water did not occur as a regular steady stream. It was controlled by local meteorological events, and throughout the summer, many reversals and stagnations in the current occurred. During periods of strong northerly flow, currents on the order of 1 knot were seen over most of the shelf area. An atmospheric system moving through could stall or stagnate the currents so that northern progress all but stopped. As the season progressed, the intensity of these atmospheric events increased, and reversals in the flow took place. Typi- cally, during the summer, 5 days would show northerly flow and 2 days would show a stagnation. As the season progressed, the average duration of the northerly flow tended to decrease; the stagnations became more frequent and reversals dominated for a day or so. As the season continued, this tendency for increased southerly movement grew and eventually dominated, so that throughout the winter the flow along the Texas coastal region was essentially to the south with atmospheric events leading to stagnations and occasional reversals. The transition from currents that flow dominantly to the north along the Texas coast to those flowing dominantly south typically occurs in late September. The fundamental question for the oceanographers involved in the IXTOC I trajectory study was to define the details of these many current reversals throughout the summer and to attempt to document the transition from the summer regime to the winter regime. To define these local and smaller scale currents, several observa- tional stratagems were employed. The first was to set up a series of onshore-offshore transects using Richardson current probes deployed by helicopter, with which surface currents off Brownsville, Mansfield Cut, Corpus Christi, and Cedar Bayou could be monitored every few days. In- creased coverage was attempted during times of atmospheric disturbance that might retard or reverse the current flow. The second method of monitoring the currents was to place radio frequency drogues along the coast and monitor their positions from radio direction-tracking shore stations. These provided more continuous monitoring of the current, but with signifi- cantly less spatial resolution. The third source of regional current information came from satellite drogues. Deployed to study the large-scale circulation for the western gulf, they occasionally drifted through the nearshore region and thus became additional sources of current data. During the maximum extent of the oil penetration into U.S. waters, the Richardson current probe work and satellite-tracked drogues were deployed in a reconnaissance mode farther north along the Texas coast as far as the Louisiana border. Once the real-time measurements of currents along the Texas coast were available, it became necessary to analyze these data and produce a current field that was both representative of the regional flow and compatible with the requirements of the on-scene spill model. Two specialized routines were used to obtain this current field, which was necessary because the observational data did not give all the information needed, and because errors in the data could lead to vector fields that could not give realis- tic descriptions of transport processes. The first criterion to be met by the derived flow field was that it conserve water, which means the analysis 26 routine must take into account the regional bathymetry and configuration of the coastline. A second important feature that derived flow fields should have was related to the constraints imposed by the dominant regional dynamics. The first of the specialized analysis routines is called Diagnostic Analysis of Currents (DAC). This routine generates the shelf flow pattern (Figure 2.7) consistent with the regional geometry and the first-order geostrophic plus Ekman dynamics, assuming an alongshore wind stress. Furthermore, since shelf circulation can have components that are not in balance with this geostrophic plus Ekman forcing, a second analysis routine, Streamline Analysis of Currents (SAC), was used (Figures 2.8 and 2.9). The composite pattern from these programs (Figure 2.10) generated a mass, or water-conserving, flow field that represented a geostrophic flow with onshore/offshore currents across the outer shelf or through tidal passes. Independent combinations of the circulation patterns derived from DAC and SAC could be added together to produce a best fit to the observed data that were consistent with the local geometry and some of the major dynamics. These patterns could represent or simulate various combinations of alongshore currents, tidal flow, or large-scale shelf waves. The current fields used in OSSM were thus composites of the analytically derived current patterns, such that they best approximated the set of observed data points. These current patterns were updated as often as new observational data were available, and in this form they made up the second element used in the trajectory study. The tactical trajectory analyses along the Texas coast continued on a routine basis as long as significant quantities of oil were observed north of the Brownsville region. LONG-TERM TRAJECTORIES Throughout September, as the currents along the Texas coast became more southerly and the regional winds tended to shift to the northeast, the threat of coastal impact to the Texas area decreased. It became essential to develop a plan for phasing out coastal cleanup activities, and stand down the cleanup crews. The actual regional response to the spill had become a multi-thousand-dol lar-a-day activity. However, before it could be terminated, it was necessary to know if the reversals that were seen in the currents and the winds, and the subsequent lack of oil, were permanent features or just short-term events. To investigate these questions and to arrive at a longer term under- standing of the oil problem in Texas waters, the Physical Processes Team did a different series of model runs. These focused on the entire western Gulf of Mexico rather than just on the coastal area of Texas. To run these experiments, we took statistical wind data for each month from the U.S. Navy Marine Climatic Atlas of the World (1976), Volume 1, North Atlantic Ocean. These gave the basic probabilities for both speed and direction 27 BRFF3N BAY TO BROWNSVILLE DIRGNOSTIC CURRENT MODEL VECTORS LATITUDE 27 28.3 LONGITUDE 97 40.0 :V//t t yT ^ ^ ^ A //^^y'^. . 1 t f f r f f , , \/t,tr,tffJfy^^^ y^ / / /y / / ^ ^ ^ . /////// 7 ^ . . . / / / / 7 / . . . . \\\\ \4«^^:^^^WNvx t WW ^.^?>e-^^ t r t t _ \ t \\n \\ fit ^y'^I ? f. , t t 1 t 1 f 1 t f 1 t 1 11 /l r 1 , \\\\\\\\\\\\\\\\\ ^ . \ \ \ /////////AW M . . ///A ///////^/.\ t ^.. f\\\\\\\ ///////. \ \ \ \ ^ LATITUDE 25 45.0 LONGITUDE 95 45.5 GRID AREA SflCBl ON MAP BR0WN2 FILE DMCURB 1 FROM CHECKPOINT fl31PRED Figure 2.7 Diagnostic analysis of currents for one of four areas used to define Texas coastal currents. 28 BAFFIN BAY TO BROWNSVILLE STREAM FUNCTION CURRENT VECTORS LRTITUDE LONGITUDE 27 28.3 97 A0.0 www www www ww\^^ ^ ^ \ ^ ^ ^ ^ ^ "vX^XX ^^NX LATITUDE 25 45.0 LONGITUDE 95 45.5 Figure 2.8 Streamline analysis of currents for one of four areas used to define Texas coastal currents. 29 BAFFIN BHY TO BROWNSVILLE STREAM FUNCTION CURRENT VECTORS LATITUDE LONGITUDE 2 7 28.3 9 7 40.0 lul I I I I I I I I I II If] iiirJ TTTTTE I If F- I- ET •' .^ • ^ J ' ^ ^ ' .^ ^ ^ • ••>'• E. - I I \ \ u / / / / i / / / / I I i i W /////// /// R i M U I i 1 \ W M I ^ i i J i u 1 ^ ^M i I D I \\\i i \\U J U\ ij////// WWII \iunuuui// niu J J J u J////////// iU///Ui//ii//////// WWWMUiiil I////// uiwiiwmiim ■■ ■ Mill// lU/i LATITUDE 25 45.0 LONGITUDE 95 45.5 Figure 2.9 Streamline analysis of currents for one of four areas used to define Texas coastal currents. 30 BAFFIN BRY TO BROWNSVILLE 1/09/79 CDT LRTITUDE Z7 28.3 LONGITUDE 97 40^0, 7///V/////// / / ///////// / / / / / 1 M/S > IT tr 1 im/nn, 1 1 Brownsville U\\ J J ^^^^^ - /7 ///////////// / / / / ///// / / / 1 l^W \llll /tt, nfffff //n,l \ \ \fl///Z^\\\\ ///////// / / / ///XVvvv ///////////// / / / j\\t\V ////I ffWtnt,,,, l\\ '^'\1/J ffffff\\\\\^^^^^^ ffLfJJfftftff\\\\\\\\\> . \\\\\\ ////////\\\\\\ttl! LATITUDE LONGITUDE Z5 45.0 95 45.5 Figure 2.10 Composite representation of currents for one of four areas used to define Texas coastal currents. 31 classes of the regional winds over the western gulf. The current patterns used in the long-range projections were composites from three different sources. The deeper waters of the gulf were covered with the monthly patterns derived from the AOML general circulation model. These currents were updated each month and represented the long-term average annual re- sponse of the Gulf of Mexico to climatological winds. Over the shallower shelf regions in the western gulf, it became neces- sary to increase the resolution because the large-scale AOML model did not cover the coastal region in adequate detail, A simple current was assumed to run north along the Texas coast in the summertime and south along the coast in the wintertime. This current exhibited 6 months of northward flow, with a reversal in September and then 6 months of southward flow. Along the Mexican coastal region, a flow pattern similar to the one derived from the U.S. Coast Guard Cutter VALIANT data and the de la Cerda thesis was used and given a twice-annual variation consistent with the dynamics suggested by Sturges and Blaha (1976). The Mexican Coastal Current was entered with a trigonometric variation showing maxima in the summer and winter and minima in the spring and fall. Given these wind and current conditions, a continuous flow of oil released from the location of the IXTOC well was traced over the gulf using two scenarios. One scenario suggested a continuous leak from 3 June 1979, when the well blew out, to 15 October 1979. The second scenario specified a continuous leak through March 1980. Each of these experiments was run in a test mode that offered the most severe challenge to the model's capability, since all the oil released at the location of the well blowout was traced without any mid-course corrections or updates, so that advective and wind- driven processes within the model were the sole determiners of the distribu- tion of the oil. This provided a check on the model dynamics and patterns. For both of the experimental scenarios, monthly patterns could be checked against actual observations that were available for the first 4 months of the spill. The projected model distributions compared favorably with observations, which increased confidence in the usefulness and reliability of the experimental results from at least a quantitative point of view. The results of the long-term experiments indicated once again that the essential element in transporting oil to the Texas coastal region was the Mexican Coastal Current. U.S. waters were threatened when the Mexican Coastal Current was strong enough to move oil north along the Mexican coast before the winds could blow it onshore. Decreases of oil in the Texas coastal waters were related to decreases in the flow of the Mexican Coastal Current and not fundamentally tied to the reversal of the Texais Coastal Current. The model suggested that over the wintertime, from September until at least February, the IXTOC I oil would tend to move to the south- southwest along the edge of the Campeche Bank and approach the coast near Veracruz. From that point, the oil would tend to remain south of Cabo Rojo and Ciudad del Carmen with major concentrations around Veracruz (Figure 2.11), Under the conditions of the second scenario, when the oil continued to leak throughout the winter, it moved north once again as the Mexican Coastal Current increased in strength, which would occur throughout January and - 32 GULF OF MEXICO AND ADJACENT flREHS 1/10/79 0: 0 CDT LATITUDE LONGITUDE 3 3 38,0 98 .0 I 232.4 KM LATITUDE 17 48.0 LONGITUDE 80 26.0 Figure 2.11 Long-term trajectory experiment based on statistical data representatin oil distribution on 1 October 1979. 33 February, raising the potential of once again bringing oil north of Cabo Rojo, up past Tampico, and into U.S. waters. During the spring, however, it was hypothesized that the Texas Coastal Currents would remain flowing south. This suggested that the oil moving north in the Mexican Coastal Current would encounter southerly flowing water somewhere near the U.S.- Mexican border. The convergence in the current patterns would then tend to create an area of oil accumulation, which would put a northern limit on the quantities of oil that could move north of the Mexican Coastal Current. From a statistical point of view, most of the oil moving north in the Mexican Coastal Current would slow down and accumulate just south of the U.S. border, where it could present a threat if atmospheric events occurred that would tend to stop, stagnate, or reverse the southerly flowing currents along the Texas coast. Such conditions were likely to occur at some time in the spring, as the Texas Coastal Current reversed. This, then, suggested that a continuing leak from the IXTOC I well could pose a threat to U.S. waters in the spring, beginning in late February or March (Figure 2.12). The dynamics associated with that threat were related to the increase in strength of the Mexican Coastal Current and the breakdown and intermittent reversal of the southerly flowing currents along the Texas coast. Computer simulation experiments carried out in December, as well as observational data through mid-January, indicated a northerly movement of IXTOC I oil. This information supported the theory that increased speeds in the Mexican Coastal Current during the winter would carry some oil to a coastal convergence zone between 25° and 26° N latitude. From this position, the oil presented a threat to the United States if either (1) the Texas Coastal Current weakened and reversed its direction of flow in the Browns- ville area so that the position of the coastal convergence migrated north, or if (2) the offshore advection associated with the coastal convergence carried oil into a counterclockwise eddy along the edge of the Continental Shelf such that it moved north and then back onshore at some position along the Texas coast. During the week of 18 through 25 January 1980, a number of activities were undertaken to investigate these possibilities. These included (1) computer analysis of the flow patterns through the three southernmost passes along the Texas coast (Brazos Santiago, Mansfield Cut, and Port Aransas), (2) measurement of alongshore drift at a number of locations along Mustang and Padre Islands, (3) measurement of shelf currents along three transects out to 45 n mi (Corpus Christi, Mansfield Cut, and Browns- ville), and (4) analysis of shelf circulations to estimate regional current patterns and persistence of the Texas Coastal Current. Observations of coastal currents and computer analysis of the regional flow provided some insights into the question of whether oil accumulating south of the U.S. border represented an immediate threat to U.S. coastal waters. Flow patterns through the various south Texas passes indicated offshore threat areas of about a few kilometers. Receptor mode model studies examining the larger scale circulation indicated that, even under the worst possible conditions, oil was still a few weeks from Texas coastal impacts. 34 GULF OF MEXICO AND ADJACENT HREflS 1/ 3/80 0: 0 CDT LATITUDE LONGITUDE P6 3 3 38.0 98 .0 > 232.4 KM LATITUDE LONGITUDE 17 48.0 80 26.0 Figure 2.12 Long-term trajectory experiment based on statistical data representating oil distribution on 1 March 1979. 35 The Texas Coastal Current showed consistent southerly flow along its major axis (approximately 15 n mi offshore). Along the shelf break and in the Brownsville area, there was evidence of the convergence associated with the Mexican Coastal Current, and it appeared that this boundary was moving north. Along the outer edge of the Continental Shelf, an extension of the Mexican Coastal Current was flowing north. This offered the possibility that oil moving north of 26** N latitude would remain well offshore. The Texas Coastal Current was as expected; however, its weakening and transition from southerly to northerly would need to be monitored to ensure maximum warning on excursions of oil into U.S. waters. A follow-up study in February 1980 included additional current measure- ments and a series of computer simulations to investigate the possibility that the pollution threat to U.S. coastal areas would decrease if the IXTOC I well was controlled by mid-February, as was rumored from a number of sources. In these experiments, oil released from the IXTOC I well between December and mid-February was traced, assuming composite currents representing best estimates along with statistical representations of monthly winds. These indicated a small statistical possibility of isolated patches of oil reaching U.S. coastal waters throughout February and March 1980. Provided the blowout was controlled by mid-February, the major threat would be greatly diminished. Current measurements taken 6 through 8 February 1980 off Port Isabel indicated quite a variable flow, suggesting the presence of shelf waves. These waves could propagate south along the coast and could be expected to be significant during periods of rapid change in the dynamic forcing for the region. With regard to pollutant transport processes, the currents associated with shelf waves implied several things. First, a series of convergence and divergence zones propagate along the coast. The signifi- cance of these in accumulating oil was well known. Second, shelf wave dynamics led to significant cross-isobath currents and subsequently enhanced cross-shelf mixing. The exchange of outer and inner shelf waters could bring pollutants to threaten the coast from farther offshore. On 16 and 17 February, current measurements off Port Isabel coincided with strong winds out of the north ("northers"), in which offshore winds gusted to 40 knots. These conditions were optimum for setting up the winter aspect of the Texas Coastal Current, and the observations confirmed a very strong southerly flow over the entire shelf area. Currents of up to 2.75 knots were flowing south, directed along isobaths. This extremely strong flow would not lead to much cross-shelf mixing (contrasted to the shelf-wave case), and it was expected that the momentum of the current would carry it south along the Mexican coast. This should result in a southerly displacement of the convergence zone between the Mexican Coastal Current and Texas Coastal Current, and its displacement to the south clearly reduced the threat to U.S. coastal waters. A final series of current observations and model trajectory experi- ments were carried out the third week in March. The seasonal reversal of the Texas Coastal Current was observed in the fall as a series of stagna- tions, reversals, and oscillations that appeared to correlate with regional wind events associated with synoptic weather patterns. A pumping action of the synoptic weather patterns on the coastal currents was also observed 36 during the studies carried out in support of the BURMAH AGATE tanker spill off Galveston. The spring reversal of the Texas Coastal Current was expected to go through a similar evolution of oscillations and reversals dominated by regional weather, but which would trend increasingly toward reduced southerly flow and eventually to northerly flow and the establishment of summer flow patterns. This breakdown and reversal process was indeed underway by early spring. However, computer studies of the shutdown of IXTOC I suggested that the major reduction in the output from the well, limited the amount of oil that could move north through the Mexican Coastal Current system, and that this source should be minimal by mid-April. The result of the March studies indicated that just about the time the Texas Coastal Current reversed, the oil accumulating south of the U.S. border would be reduced, and thus the risk of large accumulations of heavy oil reaching Texas beaches seemed minimal. RECEPTOR MODEL CALCULATIONS Throughout the IXTOC I spill, a much larger effort went into defining the distribution of the oil on a regular basis. To support this effort, long-range aircraft overflights were made daily, largely using U.S. Coast Guard aircraft, with additional support from NOAA and the U.S. Navy. To map the oil, two basic approaches were used, each corresponding to a some- what different view of what information was required. Conceptually, the most straightforward strategem was to go out and map the oil that was anywhere in the western gulf. To do this, the aircraft flew a series of patterns that fit together in a mosaic over the entire region, and they could spot oil wherever it was. Presumably, the track spacing of the flights was such that no major oil concentrations could be missed. This had the obvious advantage that all the oil could be accounted for in a quantitative or mass balance sense, and that no regions were left uncovered. It had the disadvantage that it was extremely expensive and that it required a phenomenally large amount of aircraft support. An alternate procedure for mapping the oil could be formulated on the premise that all the oil was not of interest, and instead we would concen- trate only on the oil that could pose a threat to high-value regions. In this case, it would not be necessary to map the entire western Gulf of Mexico, but only those regions where oil could conceivably get from the observed point to the designated high-value target. To investigate this possibility and define the threat regions for various points along the Texas coast, a receptor mode model study was undertaken. A standard trajectory model formulation tries to answer the question of where oil will go given its present position and hypothesized winds and currents. A receptor mode model study poses a somewhat different question: Given the winds and currents for a region, where could oil start from to arrive at a particular point? The On-Scene Spill Model was able to address both these questions. Five high-value target areas were identifed along the Texas coast, specifically, the major passes through the barrier island system. These passes represented areas where oil could move into the inner 37 lagoons. The first set of these threatened areas was Brazos Santiago, Mansfield Cut, Port Aransas, Cedar Bayou, and, finally. Pass Cavallo. For each of these points, a 1-week threat area was investigated. Alternate scenarios covered all reasonable wind combinations expected throughout the fall and expected variations within the currents. A composite of the threatened areas from each of these scenarios then represented the cumula- tive threatened region associated with each of the critical passes. If all five composite threatened areas were added together, then a region of the western gulf could be identified as the total threatened area to the five high-value points along the Texas coast. With this in hand, a rational strategem could be developed for determining which sections of the gulf needed to be mapped on a weekly basis (Figure 2.13). This study indicated a greatly reduced area that would require coverage in aerial surveys and defined an appropriate time scale for repeat observations. Figure 2.13 Outer line represents area of monitoring needed on a once-a-week basis to ensure no shoreline impact near sensitive areas, assuming steady winds for 1 week. Inner line represents required survey area for < 3 days of steady winds. 38 SUMMARY OF COMPUTER MODELING STUDIES The computer modeling studies in support of the response to the IXTOC I blowout began early in the spill and continued throughout the summer and fall. These studies were coordinated with a number of observational pro- grams and other study areas, particularly those observational programs to define and map currents and delineate the distribution of the oil. Input from the National Weather Service was another continuous source of data for the modeling. Throughout the spill, combinations of direct observations, dynamic models, and statistical climatologies were used in various experi- ments. The On-Scene Spill Model was run in three distinct modes. The first mode concentrating on the regional problem along the Texas coast, detailed information that was used on a day-to-day basis to determine the expected movement and spreading of the oil for periods of several days. This infor- mation was presented in a format that was available on an immediate basis to the on-scene personnel. A second mode of operation for the trajectory models attempted to describe the long-term prospects for IXTOC I oil movement and define the strategic threat under which the response could be planned. This mode provided information for the buildup and shutdown of the larger scale components of the response, associated with cleanup activities and sched- uling of scientific and aircraft personnel. The third mode in which the trajectory models operated was a receptor mode study that identified threat areas associated with particular high- value regions. This information was available for the planning of observa- tional programs and the delineation of minimum search areas to be covered, as well as the repeat time intervals for the observational sampling. 39 TRANSPORT. DISTRIBUTION. AND PHYSICAL CHARACTERISTICS OF THE OIL Part II: Nearshore Movement and Distribution Erich R. Gundlach and Kenneth J. Finkel stein Research Planning Institute, Colunnbia, S.C The previous section described the program and methods used to predict the movement of the oil from the blowout site in the Bay of Campeche to the Texas coast. This section describes the transport and distribution of the oil as it impacted the south Texas coastal zone. HISTORICAL SEQUENCE There were three periods of major oil impacts occurring between early August and mid-September, until current patterns switched. During this time, oil impacs on the coast were categorized as light, moderate, and heavy (Figues 2.14 to 2.18) as determined by aerial and ground surveys. After each survey, a map of the coast was made delineating onshore and nearshore oil concentrations. The extent of oil coverage on each barrier island is illustrated in Figure 2.19 and summarized for the entire impacted shoreline (from the Rio Grande to Cedar Bayou) in Figure 2.20. The estimated total amount (in metric tons) of oil along the shoreline during the spill is presented in Figure 2.21. Appendix A describes in detail the methods used to survey the beaches, to calculate the amount of oil on them, and to observe the biological impacts. Figure A.l shows station locations. 41 17 AUG 1979 Corpus Christi 18 AUG 1979 > SHORELINE OIL OFFSHORE OIL VERY LIGHT MODERATE ■ SHEEN LIGHT ■ HEAVY m MOUSSE b-BOOM ( Z- CLEANUP OPERATIOr ^s Figure 2.14 Shoreline and offshore oil along the south Texas coast on 17, 18, and 20 August 1979. 42 21 AUG 1979 Corpus' Chr SHORELINE OIL IT VERY LIGHT LIGHT b-BOOM MODERATE HEAVY C- CLEANUP OPERATIONS OFFSHORE OIL SHEEN mm MOUSSE Figure 2.15 Shoreline and offshore oil along the south Texas coast on 21, 14, and 26 August 1979. 43 29 AUG 1979 Corpus Ch 31 AUG 1979 ^ . SHORELINE OIL VERY LIGHT B I MODERATE LIGHT b-BOOM ^H HEAVY C- CLEANUP OPERATIONS OFFSHORE OIL SHEEN Y///m MOUSSE Figure 2.16 Shoreline and offshore oil along the south Texas coast on 29 and 30 August and 1 September 1979. Oil coverage reached its maximum (3,900 metric tons) during this period (see Figure 2.21). 44 4 SEPT 1979 Christi • 6 SEPT 1979 I SHORELINE OIL VERY LIGHT B:;;;;;d MODERATE LIGHT ^H HEAVY b-BOOM C-CLEANUP OPERATIONS OFFSHORE OIL SHEEN 'f//^^y>^ MOUSSE Figure 2.17 Shoreline and offshore oil along the south Texas coast on 4, 6, and 12 September 1979. 45 14 SEPT 1979 \^ 23-27 SEPT 1979 Corpus Christi SHORELINE OIL VERY LIGHT MODERATE LIGHT ^mM HEAVY b-BOOM C-CLEANUP OPERATIONS OFFSHORE OIL SHEEN K^ MOUSSE U-MOUSSE PATCHES Figure 2.18 Shoreline and offshore oil along the south Texas coast on 14 and 23-27 September and 10-11 October 1979. The survey qf 10-11 October indicated areas where outcropping mousse and sediment v/ere observed. Outcrops ranged from 5 to 65 m long and 2 to 15 m wide. 46 I I I l20, AUGUST i25 , 1979 SEPTEMBER 30 , , , , , |5 I I I I |10 I , ^ ii#fffiM^ \ 19 10 *VnV|9»'W*VVVV*VVni*>PVV***VWVVVVVV**VVVVVVVVVfn*VVVf****VV**VVVVVVV4^^ I i i i I I I"f,""'l •• •]• SAN JOSE I. I I i I I I i i r SHORELINE COVERAGE BY OIL iHVERY LIGHT [|||MODERATE LIGHT ^ HEAVY NO OIL Figure 2.19 Extent of oil coverage along the individual islands of the south Texas shoreline. 47 LU UJ O I CO 250_ 200Z 150 ~ 100_ ^ 50Z AUG. 1979 SEPT. Figure 2.20 Summary of oil coverage along the south Texas shoreline. The extent of oil coverage reached a maximum during late August. Storm activity on 13 September caused a rapid decrease in oil coverage. The earliest observed impact of IXTOC I oil in south Texas occurred on 6 August, when a total of 16 to 18 miles (26 to 28 km) of shoreline was impacted with light to very light tar ball swashlines. There were no further impacts over the following week, and the beached tar balls desic- cated and weathered. Oil began washing up again on 13 August, this time in heavier concen- trations. By 15 August, coverage of North Padre Island was mostly light, with scattered patches of moderate coverage (refer to methods and Figures 2.22 through 2.25 for definitions of oil coverage). As indicated in Figure 2.21, the situation remained static through 17 August. The area just north of Mansfield Pass had been most heavily impacted, and by this time, two 48 o o ' o 3 - ^ . X ■ v> • z ■ o 2 - H ■ o • ^m . oc H UJ 1 ^— — — — — ^aS' S 1 ■ ■ ■ ■ .J-J. J-u- ■\ TROPICAL DEPRESSION \ ''■'''' 15 20 25 AUGUST 31 1979 10 SEPTEMBER Figure 2.21 Estimated metric tons of oil deposited onshore during the spill . booms were in position at Mansfield and Brazos-Santiago Passes, and cleanup began at the hotel portion of South Padre Island and on Mustang Island. Heavy mousse patches that were located offshore of Mansfield Pass on 17 August, came ashore and impacted the areas adjacent to the inlet on 18 August. From 17 August to 22 August, the situation was fairly stable, with much of the onshore oil being reworked and redistributed along the shore. Offshore sheens with scattered mousse were common. Approximately 1 ,000 metric tons had washed ashore during this period. The second phase of major oil impact occurred on 24 August, when several new slicks were sighted off Mansfield Pass and as far north as Aransas Pass (Figure 2.15). The same day, some very thick mousse washed ashore on Mustang Island just south of Aransas Pass (Figure 2.26). By 26 August, most of North Padre Island had moderate coverage and 30 to 49 LIGHT 0.3 thickness (cm) |:^'^•:■^;^:::::Ml , , 20 5 coverage (%) BURIED OIL^/V>>^ TOTAL OIL: //////// //>>^ ^ ^ 2.2 kg./m STXI-7B. 17 AUG 79 MODERATE 0.3 ■ 0-5 0.3 thickness (cm) 5 coverage \^) TOTALOIL: 12.0 kg./m STX-2, 17 AUG 79 HEAVY 1.0 0.4 thickness (cm) 10 15 coverage (%) TOTAL OIL: 20.2 kg./m STXI-9, 18 AUG 79 Figure 2.22 Topographic profiles (5:1 ration of elevation to distance) of stations having light (10 to 24 percent coverage of the inter- tidal zone), moderate (25 to 64 percent), and heavy (> 65 percent coverage) oil accumulation. 50 Figure 2.23 Station STXI-7B on South Padre Island on 17 August 1979, indicating light oil coverage. Figure 2.24 Station STX-2 on North Padre Island on 17 August 1979, indicating moderate oil coverage. 51 Figure 2.25 Station STXI-9 on South Padre Island on 18 August 1979, indicating heavy oil coverage. Figure 2.26 View of heavy oil coverage that washed ashore on Mustang Island just south of Aransas Pass on 24 August 1979. 52 40 percent of the offshore waters were covered by sheen (Figure 2.15). Additional slicks were observed north of Mansfield Pass. The Coast Guard continued to place new booms (primarily oi 1 -absorbent type), so that by 26 August, there were three booms across Cedar Bayou, five booms along Aransas Pass, six booms at Mansfield Pass, and eleven booms along Brazos- Santiago Pass. The heaviest period of oil impact occurred from 29 August through 1 September 1979 (Figure 2.16). Oil coverage was light to moderate along the entire south Texas area. In addition, 20 miles (32 km) of North Padre Island and 4 miles (6.4 km) of Brazos Island had a heavy oil coverage. During this period, oil along the shoreline reached its maximum of 3,900 metric tons (Figure 2.21). From 2 September until 13 September, only scattered sheen was observed offshore, and no new impacts occurred. The shoreline became noticeably cleaner, primarily due to deposition of clean sand over the surface oil and desiccation of the mousse to form tar at less than half its original volume. The calculation of oil content at 18 stations from 3 to 6 September revealed that approximately 31 percent of the beached oil was on the surface, 53 percent was buried, and 16 percent remained within the swash zone and first trough (Figure 2.27). So even though the beach surface appeared cleaner, the actual oil content ashore stayed approximately the same (Figure 2.21). 3-6 SEPT 1979 TOTAL OIL: 3700 M TONS 53% 31% WWWWWW WWWWWW WWWWWW wwww\w\ \wwwww\ 16% AWWWWW^ SURFACE BURIED NEARSHORE Figure 2.27 Relative proportions of surface, buried, and nearshore (swash zone and first trough) oil as observed at 16 stations from 3-6 September 1979. 53 On 13 September, a tropical depression hit the south Texas area; tides were raised over 2 ft (60 cm), and strong onshore winds produced 3- to 5-ft (1- to 1.5-m) waves (Figure 2.28). Within 2 days, over 90 percent of the oil on the shoreline was removed by wave action (Figure 2.21). Sheen was common on the surface of the swash zone as waves reworked the oil and sediment. The small amount of oil that still remained was found high up on the beach along the base of the foredune ridge. The survey of 14 September (Figures 2.18 and 2.21) illustrated the drastic reduction in onshore oil. The only area where oil remained was in the shell beaches. As determined during Environmental Sensitivity Index Mapping (ESI), oil was expected to persist longer within this area than in adjacent fine-sand beaches. The low content of shoreline oil persisted until mid-October. Desiccation and burial by wind-blown sand decreased the amount of surface oil. During the third week in September, approximately 1 week after the tropical depression passed through, erosion of the foreshore was evident. Several deposits of mousse mixed with sediment were discovered along the shoreline (Figure 2.18). The largest of these oil masses or tar mats was located at STX-3 on the southern tip of North Padre Island (Figure 2.29). In total, it measured 15 to 20 m wide, 65 m long, and 15 cm thick. A similar mass, also located at the toe of the beach, was observed after the URQUIOLA spill in Spain (Ruby, 1977). Figure 2.28 Aerial photograph of Corpus Christ State Park, showing extent of wave activity high along the shore during the tropical depression of 13 September 1979. 54 Figure 2.29 Overview (A) and close-up (B) of the tarmats located at the south end of North Padre Island (STX-3). As measured on 22 September, this oil mass was 15 to 20 m wide, 65 m long, and 15 cm thick. 55 OIL REACTION ON FINE-SAND AND COARSE-SAND/SHELL HASH BEACHES As indicated by the prespill ESI mapping, the grain size of exposed gulf beaches is either fine sand or a mixed coarse sand and shell hash. By far the majority of the shoreline is composed of fine sand, 150 miles (240 km) as compared with 12 miles (19 km) of coarse material. The coarse sand/shell-hash area, called Big Shell and Little Shell beaches, is geolog- ically unique for the Texas coast and has been the subject of several studies. As noted primarily during investigation of the URQUIOLA study (Gundlach et al., 1978), oncoming oil reacts quite differently on beaches of different grain size. Fine-sand beaches, very hard and compact because of good sorting and fine grain size, resist oil penetration into the sediment. In contrast, oil readily percolates into the loosely packed and poorly sorted sediments of the shell beaches. Photographs of typical oil penetration show the depth and extent of oil burial also increase as grain size increases, primarily because coarse-grained beaches respond more rapidly to a change in incoming wave conditions. The repetitive measurement of profiles across each beach type immediately illustrates this variance. Figure 2.30 presents a comparison of the two beach types. Along the much steeper and more variable shell beach, oil was buried 40 cm as opposed to only 7 cm on the fine-sand beach. COARSE-SAND /SHELL HASH BEACH z 0 o < > -2 0 ^ -3.0 13 SEP '79 20 30 40 50 DISTANCE (M) 60 70 FINE-SAND BEACH EROSION DEPOSITION -3.0 STXM-2 LHTS J6 SEP '79 ' — »— ■" ■*' PAVILLION 50 M Figure 2.34 Diagram of oil presence on the bottom within the near- shore zone at station STX-16 (2 miles south of the National Park Service on North Padre Island) on 3 September 1979. became very low, and they were very scattered. The continuous reworking of the armored tar balls by wave activity rapidly decreased the quantity of oil found within the nearshore zone. Figure 2.35 illustrates the condition of onshore and nearshore oil on 5 September. At this time, particulate to 5-cm size tar balls covered 25 percent of the surface area of the swash zone, and, as revealed during examination of box cores taken in the area, oil was also incorporated into the sediment. Within the first trough, surface tar balls were very sparse and few were found in the box cores. As at station STX-16 examined a few days before, the second greatest concentra- tion (now only 2 percent) occurred on the landward side of the first bar. Due to constant wave action, particle size and abundance had significantly decreased over the intervening 2 days. During the spill, there was much speculation concerning the fate of oil within the nearshore environment. Great mats of sunken oil often were conjectured. Based on these speculations, we carried out several diving surveys extending up to 300 m offshore; these showed no evidence of near- shore sunken oil. However, before the mid-September storm and at a few 60 STX-3N, 5 SEPT. 1979 THICKNESS (mm) 2 1 COVERAGE (%) 4 (mm) thlckne.t 25% coverage 35 40 45 50 55 DISTANCE (m) Figure 2.35 Topographic profile of nearshore and onshore oil on Mustang Island. Oil on the bottom, in the form of sediment- laden or "armored" tar balls, was most common in the shorebreak and swash zone (25 percent) coverage, 43 to 49 m distance). Very few tar balls were found farther offshore. Areas where box cores were taken and the approximate number of observed tar balls within each sample are also indicated. survey stations (e.g., STXI-4 on South Padre Island), sediment-laden mousse was found in very scattered patches (up to 3 x 4 m and 10 cm thick) on the bottom, of the first trough. Figure 2.36 shows most commonly observed sequence of oil reaction within the nearshore zone. Oncoming oil was primarily swept across the berm top during spring tides; however, a small percentage became sediment- laden and rolled around in the swash zone or became incorporated in the sediments at the toe of the beach. (Essentially, the oil behaved as a coarse-grained sediment.) Wave action rapidly broke the oil down into small particles and sheen, which was transported parallel to the shore by longshore currents until being carried offshore. TAR MAT SURVEY During October, a beach survey contracted by NOAA and performed by Coastal Ecosystem Company of Corpus Christi, Texas, located 36 tar mats (accumulations of sand, shell, and organic matter bound by oil). The study method consisted of inspections by digging from the upper beach to the outer bars at 2-mile (4 km) intervals from the Rio Grande River to Aransas Pass. Readily visible mats were also mapped according to odometer readings. 61 OILY SWASHES SOME BURIAL CLEAN BEACH FACE TARBALLS MIXED IN SED SHEEN W/ SMALL TARBALLS Figure 2,36 Reaction of IXTOC I oil on south Texas beaches. During spring tides, substantial quanti- ties of oil were forced over the berm to form oily swashes, some were buried by clean sand. and an aerial coverage estimate was made. The majority of oil the Texas coast appeared to be contained in the tar mat masses, found in the first trough at the base of the intertidal zone. remaining on typically Many of the tar mats were rapidly buried by sand, especially during the winter storm season. In March 1980, the U.S. Coast Guard requested a second tar mat study to determine the volume and the degree of burial of each mat and estimate the feasibility of a removing a mat. The study, con- ducted by Research Planning Institute, Inc. , measured and mapped 19 areas of visible tar mats in various stages of burial (Figure 2.37). Other digging in random locations revealed only traces of minute tar balls. Correlation of these 19 mats with the 36 mats found in December is incon- clusive because of odometer inaccuracies. An area north of Mansfield Ship Channel, however, is known to contain the majority of the total mat volume, which averages 7.7 percent oil. In several areas, what was first thought to be several mats actually proved to be one long discontinuous or par- tially buried mat. This may, in part, account for the discrepancy between the December and March studies. Breakdown of smaller mats or complete burial during the March survey may further explain the difference in the number of observed mats. In early 1980, the United States Geological Survey (USGS), the National Park Service (NPS), and the University of Texas Marine Sciences Institute (UTMSI) at Port Aransas initiated a joint study of the 19 Padre Island tar mats. The objective of these studies is to determine the fate and effect of three of the mats through several seasons. 62 s r i: s E-i E-- E- H vo r^ 00 c* o 00 u s- (0 ^^ in vo r- 03 s: £ s: s r 6- E- f- E- e- .-H (N ro -v m to c o •1— o +J (d o u ►J < o E s- (13 ^ w ^ rs) r-l z s X s: s: 1— E- t- E- E- E- r~^ ^ r- 00 CT» o n esj s. < m £ £ I o o -J H X i: X t. C- E- =- r- I rvl f*i TT c*i 63 The USGS and the NPS are studying the physical breakdown of the tar mats and the transport of the resulting particles. Specifically, the USGS at Corpus Christi, Texas, is studying the sediment dynamics, oil transport, and erosion rate of the mats. Sediments around the mats are being sampled to determine the extent of trace metal migration, if any, from the selected study mats. The NPS, also in Corpus Christi, is conducting a statistical grid study of tar balls associated with natural tar mat disintegration. Field work conducted monthly at 11 permanent transects will document the percent coverage of tar balls and the approximate volume of oil present on the National Park beaches. In a NOAA-funded study, the University of Texas is investigating biological effects in the intertidal and subtidal zones along transects trending perpendicular to the mats. Chemical analysis will (1) "finger- print" each mat to determine that IXTOC was its source, (2) study weathered material to detect changes in toxic properties through time, and (3) deter- mine the degree of hydrocarbon flux from the study mats into the water column. OIL INTERACTION WITH THE INLETS AND LAGOONS The strategy for oil spill defense along the south Texas shoreline relied heavily on the barrier islands to absorb the majority of the oil impact and protect the biologically productive Laguna Madre. The breaks in this natural line of defense occur at a number of inlets and overwashes. The four major inlets (Brazos-Santiago, Mansfield Channel, Fish Pass, and Aransas Pass) were boomed under direction of the U.S. Coast Guard. Cedar Bayou, a shallow pass between San Jose and Matagorda Islands to the north, was first boomed and then dammed with sand across the inlet (Figure 2.38). Booms were also placed in Pass Cavallo, still farther to the north, in preparation for the advancing oil. The placement of booms along the edge or across each inlet was not totally effective in preventing oil from entering adjacent channels or lagoonal areas. Divers from NOAA's National Marine Fisheries Service and RPI observed small concentrations of flattened tar balls (tar flakes) often passed under booms or through the channel opening. The three primary inlets to the impacted area were surveyed on 11 and 12 September, after the major oil impact and before most of the oil was removed during the tropical depression. Figures 2.39 through 2.41 indicate the distribution of oil within each pass. In Aransas Pass, the marsh/mangrove system on the western shoreline of Lydia Ann Channel showed the most conspicuous signs of oiling, although in all cases oil coverage was very light. Spartina marsh grass was oil-tinged (Figure 2.42), and several large globs of mousse were present. In all other areas, oil was present as lightly scattered tar balls. The high tides and increased wave activity during the tropical depression removed most of the oil beached within the inlet. 64 Figure 2.38 Aerial photograph (10 September 1979) of sand barrier formed across the inlet of Cedar Bayou to prevent oil from passing through the inlet. In Port Mansfield Channel, oil passed under the booms placed near the seaward end of the channel and impacted adjacent shorelines (primarily sand beaches (Figure 2.40). Oil content decreased heading west down the channel. Almost no oil was observed within Laguna Madre. Mansfield Channel had the most oil of all the passes, but still this was minor (1.3 metric tons). To the south, Brazos-Santiago Pass was of particular importance be- cause of a productive nursery area (South Bay) at the south end of Laguna Madre and the presence of mangroves directly west of the pass (Figure 2.41). Fortunately, oil impact within this area was the smallest (0.2 metric tons) of the three passes. Oil coverage along the shoreline rapdly decreased after passing the narrow constrictions of the channel. In all cases, the jetty structures at the entrance to each pass helped protect the inlets from the drifting oil. 65 OIL COVERAGE LLiiJ < 1% 5 - 10% 15 - 35% O STATIONS ^ BOOMS 1.0 Figure 2.39 Distribution of oil within the Aransas Pass area on 11 and 12 September 1979. Oil coverage is described as» surface area coverage within each linear meter of shoreline. 66 Figure 2.40 Distribution of oil within Port Mansfield Channel on 12 September 1979. Oil coverage is expressed as the amount of surface area covered by oil along each linear meter of shore- line. OIL DEPOSITION IN WASHOVERS During most of the spill, including the time of major impacts during mid- and late August, tide levels were low and there was no threat of oil passing over the barrier islands and into the Laguna Madre through washovers. However, the tropical depression of mid-September substantially raised the tide level and inundated several washovers. In all, there were four problem areas on Mustang and North Padre Islands (one of which was boomed), and two problem sites on Brazos Island. Only one washover (on Brazos Island) had a significant deposition of oil. Oil coverage was light to moderate (10 to 40 percent) on the south side of the washover (due to northerly winds) and extended up to 400 m back from the Gulf of Mexico shoreline. The largest patch of oil-affected area was 150 ft by 30 ft (50 m by 10 m) and 0.2 inch (5 mm) thick (Figure 2.43). The beach in front was entirely free of oil. Some oil was also observed in the water of the lagoon, but this, too, was isolated and occurred only on the southeastern edge. 67 O STATIONS Figure 2.41 Oil distribution within Brazos-Santiago Pass and waters on 12 September 1979. SAND/OIL REMOVAL AND ANALYSIS Commercial cleanup operations were organized and administered by the U.S. Coast Guard, beginning in mid-August and reaching their peak during the first few days of September. By mid-September, most of the beach and inlet cleanup had ceased, although booms remained in all of the active inlets. Beaches were cleaned by road graders and manual labor. Marcos and Lockheed skimmers were used in the inlets. 68 Figure 2.42 Oil-tinged Spartina marsh grass along the west shore of Lydia Ann Channel (station C-5 in Figure 2.39). Figure 2.43 View of the moderately impacted area along the side of the overwash in the center of Brazoslsland. Oil is visible at the base of the plants, many of which later died because of the oiling. 69 As of September 1979, when cleanup operations had appreciably declined, a total of 667 metric tons of sand and oil was removed from Mustang and South Padre Island beaches (Table 2.1). At South Padre Island, some 415.5 metric tons of spoil were removed from the beach, while 252 metric tons were removed from the Mustang Island beaches. Table 2.1 Total amount of oiled sand removed from South Padre Island and Mustang Island Beaches as of 7 September 1979. Removal of sediment declined considerably after this date. REMOVAL OF OILED SAND m^ yd^ m tons South Padre Island 4155 5431 415.5 Mustang Island 2520 3295 252.0 TOTAL 6675 8726 667.5 Three sand/oil spoil sites were sampled on 9 September 1979. The spoil sites included two large sediment piles (approximately 50 m by 10 m in area and 3 m high) fronting dunes on North Padre and Mustang Islands. The third major site was located near the main highway on Mustang Island. Some of the material in front of the dunes was reworked by waves during the passage of the tropical depression (Figure 2.44A). The spoil near the main road was later removed to a landfill site. Two replicate samples were taken at each spoil site to determine the efficiency of the cleanup operation. Table 2.2 indicates that a relatively small amount of oil (< 7 percent) was found in the beach spoil sites and only 9 percent oil was in the road spoil site. Figure 2.44B is a photograph of a typical oil concentration within the spoil pile. Oiled sand samples analyzed during the PECK SLIP and METULA oil spills (Robinson, in press; Blount, 1978) generally exhibited oil values of 10 percent. 70 .¥ 3r Figure 2.44 (A) Spoil site on Mustang Island being reworked by waves during the mid- September tropical depression; however, no additional oil was notice- ably present around the sites. (B) Closeup of the spoil site on the beach at Mustang Island. Oil concentrations at this site average only 2.5 percent. 71 Table 2.2 Analyses of oiled sediment dumpsites on Mustang (Road Dump 1 and 2 and Mustang 1 and 2) and North Padre Islands. A photograph of the Mustang site (1 and 2) is presented in Figure 2.44. Generally, oil content was very low. BEFORE AFTER OIL EXTRACTION OIL PERCENT SAMPLE SITE (grams) (grams) (grams) Road Dump 1 1 1 1 . 47 105.40 13.07 11.00 Road Dump 2 111.90 104.65 7.25 6.50 Mean 8.75 N. Padre 1 133.10 124.92 8.18 6.10 N. Padre 2 126.66 117.83 8.83 6.90 Mean 6.50 Mustang 1 125.73 122.24 3.49 2.80 Mustang 2 109.70 107.25 2.45 2.20 Mean 2.50 72 REFERENCES CITED Austin, G.B., Jr., 1955, Some recent oceanographic surveys of the Gulf of Mexico: Trans, of AGU. , Vol. 36(5), p. 885-892. Blount, A., 1978, Two years after the METULA oil spill. Strait of Magellan, Chile - oil interaction with coastal environments: Tech. Rept. No. 16-CRD, Coastal Research Division, Dept. of Geology, Univ. South Carolina, Columbia, 214 p. Bryan, Kirk and Michale D. Cox, 1976, A numerical investigation of oceanic general circulation: Tel lus. Vol. 19(1), p. 54-80. D'Ozouville, L. , M.O. Hayes, E.R. Gundlach, W.J. Sexton, and J. Michel, 1979, Occurrence of oil in offshore bottom sediments at the AMOCO CADIZ oil spill site: Proc. 1979 Oil Spill Conf . , Amer. Petrol. Inst., Washington, D.C., p. 187-192. Gundlach, E.R., C.H. Ruby, M.O. Hayes, and A.E. Blount, 1978, URQUIOLA oil spill. La Coruna, Spain: impact and reaction on beaches and rocky coasts: Environ. Geol . , Vol. 2(3), p. 131-143. Michel, J., M.O. Hayes, and P.J. Brown, 1978, Application of an oil spill vulnerability index to the shoreline of lower Cook Inlet, Alaska: Environ. Geol., Vol. 2(2), p. 107-117. Nowlin, W.B., Jr. and H.J. McLellan, 1972, A characterizaton of the Gulf of Mexico waters in winter: Jr. of Marine Research, Vol. 25(1), p. 29-58. Robinson, J.H. (ed.), in press, the PECK SLIP oil spill, a preliminary scientific report: NOAA Special Report, Office of Mar. Pollution Assessment, U.S. Dept. of Commerce, Boulder, Colorado, 190 p. Ruby, C.H., 1977, Coastal morphology, sedimentation and oil spill vulnerability: Northern Gulf of Alaska: Tech Rept. No. 15-CRD, Coastal Research Division, Dept. of Geology, Univ. South Carolina, Columbia, 223 p. Sturges, W. and J. P. Blake, 1976, A western boundary current in the Gulf of Mexico: Science, Vol. 192, p. 367-369. Torgrimson, G.M. and J. A. Gait, 1979, An on-scene spill model for pollutant trajectory simulations: Workshop on the Physical Behavior of Oil in the Marine Environment, Princeton, N.J., p 3.43-3.66. Vazques de la Cerda, A.M., 1975, Currents and waters of the southwestern Gulf of Mexico: M.A. Thesis, Texas A and M Univ., Austin, Texas 125 p. 73 3 CHEMICAL CHARACTERIZATION AND FATE OF THE OIL Edward Overton Institute of Bio-Organic Studies, University of New Orleans BACKGROUND The IXTOC I oil spill was unique not only for its magnitude, but also for the long interval between release of oil and its impact on coastal habitats. During this time, many physical and chemical processes acted on the spilled oil. These processes, cumulatively referred to as weathering, included evaporation, dissolution, emulsif ication, adsorption onto suspend- ed sediments and detritus, photochemical oxidation, and microbial degrada- tion. These weathering processes altered the original physical and chemical properties of the oil, transforming it into several distinctly different types of petroleum residues. Physical changes included viscosity and density (and therefore buoyancy) with the formation of various types and sizes of emulsions, and oil residues with several distinct textures. Chemical changes included oxidative degradation caused by photochemical and microbial actions and were characterized by color changes of the emulsified oil with actual loss of oxidized oil by-products by dissolution of these more polar compounds in the gulf waters. The original oil slick was trans- formed into oil-and-water emulsions of various compositions: sheens, flakes of emulsions, tar balls, pancakes of various sizes, tar mats, and possibly other physical forms as it underwent weathering during its trans- port in the open gulf. 75 One important aspect of the scientific support effort for the IXTOC I spill included collecting oil samples that could be quickly analyzed to determine both the density of the oil, and thus predict whether it would sink before reaching U.S. waters, and its toxicity, for operational decision making. In addition, a project to take advantage of the research opportuni- ties afforded by the IXTOC I spill was initiated. This effort culminated in a cruise to the well site and along the oil plumes during their northward transect, by the NOAA ship RESEARCHER and a contract vessel, the PIERCE. This chapter gives the rationale and an overview of the chemistry program associated with the IXTOC I oil spill, and describes and interprets the analytical studies performed through the summer of 1980. It does not include a complete synopsis of the chemical results obtained from analysis of the samples collected during the RESEARCHER/PIERCE cruises. A complete synthesis of these results will be reported elsewhere. OBJECTIVES OF THE ANALYSES Chemical analyses of samples from oil spills in general, and this spill in particular, can provide a great deal of important information about the spill. First, and probably most important, is information concerning the identification, properties, and source of the spilled substance. Sophisti- cated chemical analyses can generally identify individual compounds or classes of compounds associated with a spill. Data from these qualitative and quantitative analyses can be used by scientists to identify the spilled substance and to assess its toxic properties. Certain compounds and/or combinations of compounds can often serve as "passive tags" to link the spill to a specific source or discharge. This latter point is particularly important when the source of the spilled material is not definitely known. Second, the extent of geographical impact and the various types of habitats, communities, and organisms affected by the spill can be uniquely and clearly identified using chemical analytical techniques. In spills such as the IXTOC I blowout, contamination from the oil is not always visible or otherwise apparent to the senses. Chemical analysis can be used to detect elevated levels of petroleum-based hydrocarbons and differentiate those substances from normal background concentrations of hydrocarbons in the environment. This ability to differentiate impacted from nonimpacted samples, however, is generally contingent on the collection and analysis of suitable nonimpacted control samples. Also, certain samples may be impacted by the so called "invisible oil" (environmental degradation products of compounds found in the spilled oil). Such impact can only be detected by sophisticated chemical analyses. Third, the environment's degree of uptake of the spilled substance can be estimated from statistically significant numbers of quantitative chemical assays. Replicate analysis from a given site must be obtained before levels of environmental contamination can be ascertained. The number of replicate samples required will depend, to a large extent, on the variabil- ity in distribution of the spilled substance at a given sampling site. An 76 even distribution of the spilled oil means that analysis of as few as three replicates at a given site will allow a quantitative estimate of the extent of environmental contamination. An uneven distribution of the spilled oil, such as has occurred from the IXTOC I blowout, means that a much larger number of samples must be analyzed to achieve an accurate quantitative estimate of the impact. Alternatively, a less accurate estimate of the quantitative impact may be obtained by analyzing fewer sample replicates. In certain instances where the distribution of oil is very uneven, only its presence or absence in a given area can be determined. Fourth, chemical analysis can indicate both the duration of a spill and ultimate fates of petroleum hydrocarbons in the environment. This informa- tion is particularly important for damage assessment studies. In general, for spills in high-energy environments, the environment's adjustment to prespill condition can be measured in months. For low-energy environments or protected habitats, such as the Laguna Madre, the recovery period from massive oil spills may take years. Chemical analysis can be used to indi- cate when the environment returns to the prespill conditions. The Federal response to the IXTOC I oil spill collected over 1400 samples in and along the northwestern Gulf of Mexico. Over 1000 additional samples were collected near the well head by the NOAA ship RESEARCHER, and PIERCE cruises. Sample collections started in mid-July 1979, before the oil impacted Texas beaches and continued on a limited scale to the summer of 1980. Sample collection activities under Federal sponsorship from 16 July through 13 December 1979, included nine major cruises by research ships or cutters, extensive beach sampling, and collection of commercial fishery products. Table 3.1 lists the numerous sampling activities under- taken during the spill. Appendix B contains a description of each activity. A complete treatment of the sampling program, including numbers, types, and locations of all samples, collector storage methods, and present location of samples is contained in McCarthy et al. (1980). Additionally, a joint BLM/NOAA-sponsored research effort has been undertaken to ascertain the environmental damage from the IXTOC I oil spill in a limited area along the Texas coast. Results from this study will be reported when these studies are complete. RESULTS AND INTERPRETATION This section identifies the physical and chemical characteristics of the oil that impacted south Padre Island in the summer of 1979. Very little analytical work was done on samples collected during this impact; therefore, most of the chemical information was inferred from analyses of samples collected during the NOAA ship RESEARCHER cruise to the Bay of Campeche. For example, analysis of these samples indicated evaporative weathering had already changed the composition of the IXTOC I oil by the time it reached the surface. Other physical weathering processes caused the oil to form "water in oil" emulsions (chocolate mousse) of various sizes. Visual observations suggested photochemical weathering of the oil. These transformations were reflected by color changes in the emulsions and 77 Table 3.1. Sampling Activities MARINE CRUISES 1979 1. VALIANT 2. POINT BAKER 3. Cruise FSU-I 4. LONGHORN I 5. LONGHORN II 6. OSV ANTELOPE 7. NOAA Ship RESEARCHER/PIERCE 8. Cruise FSU-II 9. LONGHORN IV July 16-21 July 27-28 July 26-31 August 4-8 August 15-16 August 25 - September 8 September 11-27 October 31 - November 6 November 16 - December 13 BEACH SURVEYS 1. Initial Impact Samples - HAZMAT Team 2. RPI 3. URS FISHERIES WILDLIFE SURVEY STUDIES 1 . R/V WESTERN GULF 2. NMFS Monitoring, Fisheries Products 3. PDS Monitoring, Fisheries Products 4. Patuxent Toxicity Studies 5. UTMSI/PAML Mussel Watch Program DISJUNCT COLLECTIONS by a tendency for a crust to form on the floating mousse. Physical agita- tion in gulf waters caused larger emulsion pancakes to be broken into smaller particles known as tar balls or tarflakes. These tar balls, which ranged in size from several millimeters to several centimeters, frequently 78 contained a heavily weathered outer crust and a less weathered inner material The chemical characteristics of the inner material often resembled those of fresh oil samples that were collected near the well head. By the summer of 1980 the following major questions have been identi- fied and will be discussed in this chapter: 1. What were the characteristics of IXTOC I well head oil? 2. Were toxic compounds present in oil that reached the south Texas beaches? 3. Can oil that impacted the south Texas beaches be unequivocally identified as oil that originated from the IXTOC I blowout? 4. Which components of the ecosystem were impacted by IXTOC I oil? 5. What were the ultimate fates of IXTOC I oil in the Gulf environment? Characteristics of Well -Head Oil Several floating oil samples, collected on the NOAA ship RESEARCHER cruise, came from the immediate vicinity of the IXTOC I well and were chemically characterized by high resolution gas chromatography-mass spec- trometry (GC-MS). The chemical composition of these samples has been reported in detail at the Key Biscayne Symposium on results from the cruises of the NOAA ship RESEARCHER and M/V PIERCE. A brief summary of the more ecologically significant families of hydrocarbons and nonhydrocarbons (NSO compounds) found in IXTOC I oil is presented herein. The sample contained normal hydrocarbons with as many as 35 carbon atoms in the hydrocarbon on compounds as well as numerous branched, cyclic, and isoprenoid hydrocarbons. The following families of aromatic hydrocarbons were also identified in relatively fresh IXTOC I oil. Alkyl benzenes (to at least C-.„ alkyl homologs) Naphthalenes (to C. alkyl homologs) Napthenoaromatics (to C- aklyl homologs) Biphenyls (to C- alkyl homologs) Fluorenes (to C„ alkyl homologs) Phenanthrenes (to C- alkyl homologs) The pyrene family (to C- alkyl homologs) The chrysene family (to C_ alkyl homologs) The benzopyrene family (to C- alkyl homologs) 79 The following sulfur containing nonhydrocarbon families were identi- fied by gas chromatography-mass spectrometry: Benzothiophenes (to at least the C-. alkyl homologs) Bibenzothiophenes (to the C„ alkyl homologs) Benzonaphthylthipohenes (to the C» alkyl homologs) Nitrogen containing nonhydracarbon families were also identified in IXTOC I oil: quinolines (C^ to Cj. alkyl homologs) phenanthridines (X„ to Cj- alkyl homologs) carbazoles (C„ to C^ alkyl homologs) Of course, crude oil is composed of many thousands of individual compounds, and therefore other hydrocarbons and nonhydrocarbons were present in IXTOC I oil but have not yet been identified. Toxic Compounds Present in Beached IXTOC I Oil Aromatic hydrocarbons and nonhydrocarbons are generally considered to be toxic to marine organisms. The prevalent conception is that the more volatile aromatic hydrocarbons, such as the benzenes and napthalenes, are responsible for the acute toxicity of petroleum. Toxicity resulting from chronic exposure to petroleum is associated with the presence of higher molecular weight aromatic hydrocarbons and nonhydrocarbons. In many cases, oxidation of these substances changes a relatively innocuous hydrocarbon or nonhydrocarbon into toxic or carcinogenic compounds. Additionally, poly- cyclic aromatic hydrocarbons present in petroleum are considered potential carcinogens, and, in fact, humans living close to petroleum industries suffer above average cancer mortalities. These facts lead to the definite conclusion that chronic exposure to petroleum aromatic hydrocarbons and nonhydrocarbons should be considered a health hazard to both marine organ- isms and humans. Very few samples of oil from the south Texas area have been analyzed,* and therefore the toxicity of beached oil can only be inferred from the analysis of samples collected during the NOAA ship RESEARCHER cruise. The U.S. Coast Guard Cutter POINT BAKER also collected samples of mousse in the gulf waters south of the U.S. -Mexican border, and these samples were specif- ically analyzed to determine the identity of toxic aromatic compounds. The *Many of the samples will be analyzed under the BLM/NOAA Damage Assessment Program now underway. 80 aromatic compounds found in the U.S. Coast Guard Cutter POINT BAKER samples are included in the list of aromatic hydrocarbons and nonhydrocarbons given previously. Limited analytical data indicate that tar balls and mousse samples, even those considered heavily weathered, retained quantities of both the acutely and chronically toxic aromatic hydrocarbons and nonhydrocarbons. These data suggest that most mousse and tar balls had a physical structure similar to that of a jelly bean. That is, these oil substances were com- posed of a heavily weathered outer crust that was depleted of aromatic hydrocarbons and nonhydrocarbons. The inner material, which was visually different from the crust, contained essentially all types of the aromatic hydrocarbons and nonhydrocarbons found in fresh well head oil. There was, as expected, tremendous diversity in the quantities of these aromatic substances in the weathered samples. Examination of data from the limited number of beached tar balls analyzed to date suggest there was significant quantities of aromatic compounds present in tar balls that washed ashore on south Padre Island. As of the summer of 1980, no samples of biota have been analyzed by standard GCMS techniques to determine the uptake of petroleum hydrocarbons and nonhydrocarbons. Samples of shrimp were organoleptical ly tested (tasted and smelled) and found to be free of petroleum residues using this relative- ly insensitive technique. Petroleum aromatic compounds can be oxidized by various natural (photo- oxidation), biological, and enzymatic processes. These water soluble oxidized compounds cannot be detected by visual inspection of the environ- ment and are therefore, frequently referred to as the "invisible oil." Oxidation generally increases the toxic and carcinogenic properties of aromatic compounds, and consequently this "invisible oil" may present a health hazard to marine organisms and man. No samples from the northern Gulf of Mexico have been analyzed for these oxidized aromatic hydrocarbons and nonhydrocarbons, and therefore nothing can be implied about their impact along the south Texas gulf coast. Identification of IXTOC I Oil in the South Texas Environment There is strong observational evidence to link tar balls that impacted the south Texas environment with the IXTOC I blowout. Unfortunately, other sources, both natural (seeps) and anthropogenic (tankers) could have caused a portion of the impact. There is, a need to chemically link the oil that impacted south Padre Island with the oil that resulted from the IXTOC I blowout. As of the summer of 1980, this link has not been unequivocally established with hard chemical evidence. The question must be proposed, "Do scientists have the analytical tools and established techniques necessary to identify IXTOC I oil if it impacted south Padre Island?" And further, if the answer to this question is yes, how can this identification be accomplished? 81 The answer to the first question is a qualified yes. The following paragraphs outline what information is needed to link IXTOC I oil with tar balls collected from south Padre Island. It also estimates the degree of accuracy in the identification. The chemical composition of various crude oils is qualitatively the same (most petroleums contain the same types of compounds). Quantitatively, there is great diversity in the amount of individual compounds in different crude oils. Furthermore, the quantitative distribution of compounds can be affected by the various weathering processes. Consequently, no single qualitative or quantitative parameter can be used as strong evidence to identify a given oil sample as having come from a specific source. A combination of chemical parameters must therefore be used to elucidate the source of petroleum in environmental samples. These identifications must be verified by analysis of a statistically significant number of field samples that were collected from areas known to be impacted by oil from a specific source (exposed sample). Control samples from a nonimpacted area must also be analyzed. It is also extremely useful for oil source identifi- cation if samples from the suspected source oil can be analyzed. The following are typical, but not inclusive, of the chemical parameters that are commonly used to link an environmentally weathered crude oil with its sources. The ratio of carbon 13 to carbon 12 and sulfur 34 to sulfur 32 are characteristic of the diaganetic history of a given crude oil's formation zone. These parameters are relatively insensitive to weathering, and can be used to indicate possible crude oil sources. They should not be used as unequivocal chemical evidence linking petroleum containing samples to specific sources but rather as eliminators of those samples that could not have originated from a given source. Generally, we do not consider physical data, such as viscosity, boil- ing points, ultra violet, infra-red, and UV-fluoresence spectra as applicable to the identification of petroleum sources in weathered crude oil samples. The quantitative distribution of certain hydrocarbons and nonhydrocar- bons within a crude oil is very characteristic of the source of that crude oil. Distributions of the following compounds or families of compounds are typically used to qualitatively identify the source of environmentally exposed crude oils: isoprenoid hydrocarbons cyclic and branched hydrocarbons hopanes and stearanes alkyl benzenes alkyl naphthalenes alkyl benzothiophenes alkyl biphenyls (or acenaphthalenes) alkyl fluorenes 82 alkyl phenanthrenes alkyl dibenzothiophenes alkyl quinolines alkyl carbazoles alkyl phenanthridines The quantitative comparison of these substances, both within a specific family of compounds and between families of compounds, can present strong evidence to link a given environmental crude oil sample with a specific source. These quantitative distributions are generally obtained from data produced by the analytical techniques of glass capillary gas chromatography and glass capillary gas chromatography-mass spectrometry. Certain samples, if heavily weathered, are beyond recognition as coming from a specific source. Also, the incorporation of crude oil at very low levels in certain types of samples, such as sediments or biota, substantially increases the difficulty at linking the petroleum to specific sources. Components of the South Texas Ecosystem Impacted by IXTOC I Evaporative weathering causes losses of the more volatile components of IXTOC I oil. However, oil that impacted Texas beaches still retained the smell of petroleum. Even though no scientific measurements were taken to evaluate atmospheric impact, it was apparent that atmospheric impact in the south Texas environment is minimal. Visual inspection of the beaches along South Padre Island indicated most oil that impacted the beaches was in the physical form known as tar balls. Several large tar mats were also observed in the trough line. Strong circumstantial evidence indicates the types of petroleum residue came from the IXTOC I blowout. Visual observatons before beach impact revealed large quantities of oil floating in the Gulf of Mexico. The quantities of oil that impacted South Padre Island were substantially less than those observed offshore. The discrepancy between visual observations of the amount of oil offshore and of that which reached the beaches led to the speculation that large quantities of oil lost its buoyancy and sunk before it impacted the Texas beaches. These speculations were never verified by chemical analysis. The extent of impact to other components of the ecosystems, such as the water column, bottom sediments, or various types of biota have not been determined as of the summer of 1980. The BLM/NOAA-sponsored damage assess- ment program is designed to answer some of these questions. 83 Ultimate Fates of IXTOC I Oil The ultimate fates of petroleum in the marine environment has been the subject of much work and speculation. One of the major goals of the NOAA ship RESEARCHER cruise and subsequent analytical efforts was to determine the effects of weathering on IXTOC I oil. Much information is being accumu- lated from this research venture. Unfortunately, very little information is available on the fates of the IXTOC I oil in the south Texas area, because essentially no chemical analyses have been performed from samples collected in this region. Synthesis of data from the NOAA ship RESEARCHER cruise is still in progress, but the following general observations can be made. 1. IXTOC I oil formed emulsions (chocolate mousse) within a few kilometers of the well head. 2. Emulsions were subjected to color changes and formed a crust after exposure to sunlight. 3. There is strong evidence to suggest that microbial degradation of the IXTOC I oil occurred at a relatively slow rate (microbes were nutrient starved). 4. Laboratory photolysis experiment using IXTOC I oil indicated that sunlight promoted the formation of numerous fatty acids and oxidized aromatic acids and alcohols. 5. Analysis of weathered emulsion samples did not reveal large quantities of polar oxidized hydrocarbons in the sample. This implies that as the aromatic hydrocarbons and non-hydrocarbons were environmentally degraded to more polar products, and that these products were leached into the water column and diluted in the Gulf of Mexico. 6. The important results will be included in a synthesis document currently being developed. Of the large quantities of oil that were introduced into the gulf environment by the IXTOC I blowout, very little was recovered by cleanup operations. The fates of the remaining IXTOC I oil, as of this writing, is subject to speculation. 84 4 RESOURCES AT RISK Robert Hannah Office of Marine Pollution Assessment, NOAA, Bay St. Louis, Miss Charles D. Getter Research Planning Institute, Columbus, S.C. Many resources were at risk in the south Texas area during and after the IXTOC I impact period. Padre Island and the Laguna Madre are known to be one of the most important staging and wintering areas for waterfowl, shorebirds, and colonial waterbirds in the United States. The endangered brown pelican, whooping crane, and peregrine falcon all use this area. Sensitive marsh areas are also found in association with the extensive lagoonal system there that provides an important nursery for commercial species upon which the Texas Gulf fisheries industry depends. The dockside value of shell and finfish landed at all Texas ports was $125.5 million in 1978. Eighteen species of marine mammals and five species of marine turtles are reported to be residents of the offshore area of south Texas with all except one classified as protected, threatened, or endangered. Because of their value, these resources and more will be viewed in this chapter from both a biological and socioeconomic standpoint. 85 BIOLOGICAL SETTING Lagoons Laguna Madre, Corpus Christi, Aransas, San Antonio, Matagorda, and Galveston Bays and their drainages make up the Texas lagoonal system. They are divided into the deeper basin and the shallower inshore region on the basis of depth (as by Hedgpeth, 1967). Lagoonal basins Most of the deeper portions of Texas lagoons and bays are occupied by an assemblage of crabs, shrimp, croakers, catfish, and other fishes of more or less seasonal occurrence (Hedgpeth, 1967). This assemblage is distinct from the shallow water lagoonal community, differing primarily by size (larger) and seasonality of the species involved. Since many of the orga- nisms are mobile and subtidal, they are able to escape the physical and chemical effects of oiling by actively avoiding oiled areas. The Laguna Madre supports a considerable commercial and recreational fishery for redfish, drum, and seatrout. Hedgpeth (1953) reported that over half of the total Texas fish landings of these three species came from the Laguna Madre. While commercial and recreational species have a large standing-stock biomass, the diversity of other biota is low (Breuer, 1962), consisting of only eleven resident invertebrates and ten resident fishes. A highly organic detrital substrate and a flourishing plankton population (i.e., copepods) (Breuer, 1962) fuels a productive detrital-plankton based ecosystem. Seagrass and algae beds Marine grasses and algae are largely subtidal. In extensive areas of the lower Laguna Madre, macroflora are absent and the dominant producers are blue-green algae. Environmental conditions prevent the successful invasion of shoal grass throughout large areas, although its spores are regularly dispersed throughout the system (Breuer, 1957). Elsewhere in the Texas lagoonal system, seagrasses contribute signifi- cantly to primary productivity (Wood et al . , 1967). The three most impor- tant seagrasses in Texas lagoons are shoal grass, widgeon grass, and turtle grass. These grasses help stabilize the mud flats and subtidal substrate, and provide critical habitat for numerous animals. Populations of these animals undergo rapid fluctuations because of the seasonal nature of sea- grass habitats (Conover, 1964). Animals in the lagoonal system include the following crustaceans: grass shrimp, caridean shrimps, arrow shrimp, snapping shrimp, and the commercially valuable pink shrimp. Crabs and bivalves characteristic 86 of Texas lagoonal seagrass beds include the mud crab, thick lucine, cross- barred venus, and bay scallop. The sea cucumber is also a commonly encoun- tered organism. Among the many gastropods using the seagrass habitat are the virgin nerite, two whelks (Busycon contrarium and B. spiratum) , Texas tusk shell, and bubble shell. Wintering waterfowl in the lower Laguna Madre (about one-half million birds) are reported to be attracted to exposed seagrass beds, especially shoal grass (McMahan, 1968). Oyster Reefs Oyster reefs, both living and dead, are a prominent feature of Texas lagoons. The American oyster is a sessile bivalve that attaches permanently to almost any firm substrate below mean low tide level. While the commercial value of oysters is in harvesting them for human consumption, oyster reefs are also an important ecological component. They form solid substrate areas that provide attachment sites for subsequent oyster recruitment, as well as for other attached organisms, marine algae, and myriads of small animals. Hedgpeth (1953) characterizes oyster reefs as the most important biotic aggregation in Texas lagoons and documents recent extensive die-off s of oysters due to man- induced changes, including dredging, filling, and manipulation of freshwater runoff characteristics. Large sections of oyster reef habitat are, therefore, no longer living, but consist of the shells of dead animals. Dead oyster reefs, in contracts to live reefs, are judged as relatively low in vulnerability to oiling due to the general absence of living oysters and the subtidal nature of the environment. Spoil Islands Dredging operations in the shallow lagoons of Texas have produced numerous islands or chains of islands that have become a substrate for the development of plant and animal communities, many of them are attractive to colonial seabirds and wading birds as nesting sites (Chaney et al . , 1978). Among the birds using these spoil islands are endangered and threat- ened species such as the brown pelican, black skimmer, and least tern. Almost all other birds nesting on spoil islands are protected or considered as having aesthetic value (e.g., great blue heron, little blue heron, roseate spoonbill, and white pelican). Chaney et al . (1978) lists a total of 47 species that nested on these spoil islands in 1977, of which over 30 species are colonial or wading birds. Lagoonal Beaches Lagoonal beaches having variable substrate composition, grain size, and organic content comprise a considerable portion of the south Texas coastline (27.3 percent). They are usually steeply sloping habitats, ranging from highly protected to moderately exposed to waves and currents, Three types of lagoonal beaches are addressed below. 87 Scarps in clay. This habitat is characterized by a very fine-grained, compact sediment, which is relatively stable due to its cohesive nature. The compacted nature of clay/sand sediments and the resulting impermeability and lack of interstitial space are the greatest limiting factors for communi- ties inhabiting clay scarps and beachfaces. In addition, clay affords a poor attachment surface and burrowing medium. Fiddler crabs and wrack- associated amphipods are present in small numbers in the supralittoral zone, a few nereid polychaetes are present in the inter- and subtidal portions of this habitat type. Sheltered sand beaches. The slope and composition of the beach face sediments are variable and dependent upon physical factors. Sandy substrates are relatively porous, allowing some limited burrowing activity. Intersti- tial spaces are used largely by bivalves and polychaete worms. Sand, like clay, affords a poor attachment substrate for plants and, therefore, has very low endemic primary productivity. Mixed sand and shell beaches. Sheltered sand and shell beaches usually have the steepest profiles of all Texas lagoonal beaches. The coarse substrate lacks the stability necessary to sustain a community with a large diversity or biomass, and interstitial pore size is too large for the capillary action necessary to keep beach sediments moist and prevent desic- cation of the infauna. Tidal flats Tidal flats occur throughout the south Texas lagoonal system and are 20.6 percent of the shoreline. Substrate composition, grain size, and organic content are all variable. Exposure to wave energy is very low to moderate. Parker (1959) characterizes three tidal flat environments, based on the invertebrates inhabiting them. Breuer (1957), among others, has affirmed the validity of the principles behind this classification in the Laguna Madre lagoonal complex, especially with reference to the fishes. These three tidal flat types are discussed below. Exposed tidal flats with low biogenic activity. Very few large orga- nisms are capable of adapting to the harsh environment of varying tidal exposure and salinity present in this habitat. Prime among these is the blue-green alga, which in some areas forms dense mats and often constitutes 80 percent of the living community (Sorenson and Conover, 1962). In addi- tion, unicellular green algae, flagellates, diatoms, and bacteria are found (Sorenson and Conover, 1962; Cuzon du Rest et al . , 1963). Animals present include ciliates, nematodes, crustaceans, corixid water bugs, and worms (Soil ins, 1969). The small clams Mulina lateralis and Anomalacardia cuniemeris are occasionally present beneath the mats (Dalrymple, 1965), and sheepshead minnow is often present above (Odum, 1967). Exposed tidal flats with moderate biogenic activity. This tidal flat environment is more stable in terms of physical and chemical factors, although physical stresses are still high. An increased standing stock 88 biomass is present within a low-diversity community. This habitat type is relatively rare (0.25 percent) among south Texas coastal environments, occurring mainly along the more sheltered, better flushed portions of the back shore of the barrier islands. Sheltered tidal flats with high biogenic activity. The third type of tidal flat habitat is more sheltered from wave activity and has a more stable salinity, encouraging relatively high species diversity and standing stock biomass. Seagrasses in the intertidal portion of this habitat add to the complexity of its trophic relationships. Primary among these seagrasses is shoal grass, although turtle grass is locally abundant. These seagrasses are highly seasonal and die down when temperatures are high in the summer (Hedgepeth, 1953). Like sand beaches, sheltered tidal flats are inhabited by either burrowing or very motile species. Molluscs, crustaceans, and polychaetes are the dominant burrowing macrofauna. Prime among these are two species of razor clams (Tagelus plebius and Ens is minor). Feeding upon these abundant bivalves are the oyster drill, blue crab, hermit crab, and various shorebirds (especially gulls and terns). The presence of other burrowing bivalves is dependent upon prevailing physical and chemical factors and the individual requirements of each species. Burrowing bivalves are commonly fed upon by large crabs such as the blue crab, the stone crab, and the whelk. Mud crabs inhabiting sheltered tidal flats include the common mud crab, flat mud crab, and the mud crabs Neopanope texana and Rithropanopeus harrisi Shrimps that burrow in mud include Ca1 1 ianassa jamai cense louisianensis. Gastropods present include the moon snail, common mud snail, and common Atlantic auger. Hermit crabs that occupy the empty shells of these and other tidal flat gastropods include (CI ibinarius vittatus , Pagurus longicarpus , and P. pol 1 icaris. Burrowing worms present include the parchment worm, lugworm, and other polychaetes, such as Eteone heteropoda and Laeoereis cul veri . The vulnerability to oiling of any of the three types of tidal flats relates to the mechanical and chemical effects on individuals as well as community diversity and biomass. Physical processes and sediment grain size control oil penetration and persistence. Community structure controls biological response. Organisms in a habitat under stress are already living at or near their physical limits. The effects of oil contamination may thus be devastating to such a community. In addition, low-diversity communities are less capable of withstanding any impact and slower to recover from pulsing, although where there is a large standing stock biomass, the quanti- tative destruction can be much greater. 89 Marshes Marshes occur on the lagoonal side of the sand beaches, the landward side of lagoons, along streams and rivers that drain into the lagoon, and on spoil islands and deltas (Phleger, 1965). Dominant features along the edges of the lagoons are inland or landlocked ponds, commonly ringed with cordgrass and high marsh vegetation. Physical conditions are extreme, with great variability in temperature and salinity. Benthic seagrasses and algae are sparse, but a large standing biomass in fishes and shrimp is characteristic (Gunter, 1950; Hedgpeth, 1950). Also abundant are burrowing polychaetes, hermit crabs, and gastropods. These areas provide rich feeding grounds for migratory waterfowl and shorebirds (Gunter, 1958). Landlocked ponds are considered vulnerable to oiling only when they have surface water connecting with open water. Figure 4.1 illustrates the species charac- teristic of Texas lagoonal marshes. This habitat closely resembles a marsh type termed "fringing," which dominates long stretches of back-barrier and mainland shorelines. Vegetation patterns are influenced by a complex of environmental factors and consist of two zonation patterns. The dominant producer, dominating the vegetated ti del and zone, is saltwater cordgrass. This shallow subtidal and intertidal vegetation damps impinging waves, tides, and currents, creating a sheltered-water microhabitat. Sediment accretion and stabilization and nutrient remineral ization are promoted, and the potential for spawning and nursery habitat is increased. A second zone characteristic marsh habitat is termed "high marsh." Vegetation is dominated by halophylic marsh plants such as sea ox-eye daisy, glasswort, and saltgrass. The black mangrove is scattered but locally abundant. Black mangroves are largely tropical/subtropical species whose range is limited by low temperatures, especially frosts. Most black mangroves in Texas are less than 1 m tall, and a significant number are dead due to recent frosts. The black mangroves in the study area appear to be at or near their minimum temperature limit. Animals inhabiting salt marshes are diverse and abundant and, like plants, exhibit physical responses and adaptations to numerous environmental factors that result in a distinct zonation in distribution. Grazing on plant and detrital material takes place in and on sediments and plant surfaces throughout all marsh zones. Intertidal grazers characteristically dominant in Texas lagoonal marshes include small shrimp (Paleomonedes, Tozumia, and Penaeus) , killifishes (Adinia, Cyprinodon, Poecil ia, Fundulus, and Lucania) , and crabs (Cal 1 inectes and CI ibinarius). The salt marsh periwinkle is an abundant grazer in the aerial parts of saltwater cordgrass. Juvenile and young adult mullet are seasonally abundant invaders of the vegetated intertidal salt marshes of Texas lagoons. 90 CD < I I CO cc < :7/l if'o / yT- ^va" /y /« (B 7/ / n Snail Periwink lam // < 0) s^w E V c z « o w offee Be alt Mars ackknife (B o o N n cr O 1) n > o UJ < orrychia jncus atis .5 c o o « Is > z 3 >. ■D 0) z < III o a ab rimp Crab •o o § < X o w ._ a, 3 o (A a (S e r "5 o < t- w ■D E (S M « lue Cr ud Sh ermit a a E « « (J cr cr O _i 2 w W 2 U. toai3 I < o 1 CD n A u T) u. (S a o c 03 o • 1— N J3 E S- 3 • ^ r^ q; O JT o -P #s ■o C c o fO to c >i-C •p o • r— o c 3 ) ro ^ ■o C35 c C (0 J- 3 3 O O) in 91 Not many infaunal organisms were observed in high marsh zones, nor were abundant infauna noted within intertidal vegetation. In contrast, shallow subtidal waters support a moderate to locally heavy infaunal popula- tion consisting of bivalves (Toredo and Ensis) , mud shrimp, and polychaete worms. High marsh consumers are dominated by fiddler crabs, which burrow extensively among high salt marsh plants. Amphibious and terrestrial insects, abundant throughout the high marsh and the intertidal zone at low tide, also use aerial portions of intertidal salt marsh vegetation. Mobile consumers, which may invade or inhabit salt marshes, consist of terrestrial mammals, euryhaline fishes, and migratory and shore waterfowl. Texas lagoonal marshes are highly vulnerable to oiling, due to the sheltered nature of the environment and the sensitivity of resident plants and animals. The impact to dominant components of the Texas marsh ecosystem includes oil -induced mortality of Spartina alterni flora (Baker, 1971), Sesuvium, Batis, Sal icornia, and Avicennia (Chan, 1977). Primarily, the impact to salt marshes is related to the toxicity of oil to individual species, the temporal pattern of oiling (chronic spillages), and seasonality. Inlets The biological role of Texas coastal inlets has received much study (Hedgpeth, 1953; Gunter, 1958; Copeland, 1965; Simmons and Hoese, 1959). The limited numer of inlets bisecting Texas barrier islands increases the relative value of each inlet and also its control of biological processes. Inlets constitute the vital link between the lagoons and the Gulf of Mexico and perform the following biological functions: 1. Influencing the salinity regimes within the lagoonal system and, therefore, the distribution and relative abundance of dominant organisms. 2. Acting as avenues of transport for migrating fishes, shrimp, and crabs that enter the lagoons to feed or spawn. 3. Exchanging nutrients, detrital material, and plankton. In total, more than 24 species of invertebrates and 55 species of fishes are known to move through Texas passes, including several commercial species (Copeland, 1965). Shrimp and crabs enter passes en route to lagoonal spawning grounds. This is followed by a peak passage out of lagoons by shrimp and crab larvae. Copeland (1965) indicates that there is a net migration into the Gulf of Mexico waters from the Texas lagoonal system, and that peaks in migration occur in May-June and October. Copeland (1965) estimates peak emigrations of up to 318,960 kg of biomass per day through Aransas Pass. 92 Beaches Exposed, fine sand beaches Exposed fine-sand beaches occur on the seaward side of the barrier islands and make up 22.8 percent of the south Texas coast. A considerable body of literature documents research on sand habitats (see Hedgpeth, 1953), including studies on plankton and productivity (McFarland, 1963a), dominant macroinvertebrates (Whitten et al . , 1950); Loesch, 1957; Hill and Hunter, 1973), infauna (Keith and Hulings, 1965), and fishes (Gunter, 1958; McFarland, 1963b). An illustration of this habitat and its characteristic species is presented in Figure 4.2. The lack of stable, solid surfaces and the abrasive action of moving particles does not allow an exposed sandy beach to support the abundant large algae found on rocky shores or the rooted vegetation found in muddy or sheltered, marsh areas. Endemic primary productivity is low and re- stricted in microorganisms (mainly diatoms) that generally live within the upper few millimeters of sand. The role of microorganisms on sandy beaches is relatively important because of the low standing stock biomass of sessile macroorganisms. Of the infaunal species (>0.5 mm), burrowing bivalves, polychaete worms, and^ crustaceans make up significant portions of the macrofaunal community on exposed Texas beaches. Characteristic dominant species of these groups include coquina clams, polycheate worms, mole crabs, and haustorid amphipods. Despite the relatively small number of species, the number of individuals may be tremendous. Loesch (1957) estimated over 10,000 coquina clams per square meter at one station on a Texas beach. Immediately below the intertidal zone to a depth of about 1 m, the number of species increases. Keith and Hulings (1965) report finding 35 species of macroinfauna, including 17 crustaceans, 12 polychaetes, and six molluscs at Texas beaches. The nearshore community of Texas sand beaches is probably the richest and most diverse of any part of the sand beach. The gentle, sloping sub- strate, less exposed to the effects of wave action, supports an assemblage of sessile, sedentary, and motile invertebrates and bottom feeding fishes (Hedgpeth, 1953). Conspicuous among these are commercial shrimp (Peneaus). Also occurring within the breaker zone is an assemblage of mud shrimp, portunid crabs (Arenaeus and Cal 1 inectes) , keyhole urchins, and sand stars. Over 40 species of fishes are reported from Texas beaches (Gunter, 1958), the most abundant being common pompano, sardines, mullet, and croaker. These are all valuable commercial or forage species. Recreational fishes of Texas sand beaches, reported by Springer and Pirson (1958), include redfish, mangrove snapper, drum, croaker, and sheepshead. The back-beach area of this habitat is dominated by the ghost crab, which feeds at the waterline, mainly at night principally upon the macroin- fauna Donax and Emerita (Wolcott, 1978). Its habitat extends from subtidal to landward on the beach foredunes. On Texas beaches, the greatest popula- tions of the ghost crab are found along the foredune ridge (Hill and Hunter, 1973). This portion of the beach is relatively stable and, due to its 93 < X o < UJ m < CO o lU CO o Q. X lU s^ <"i: ■^: i?^-V ■- CV'A? X-'.' .is?;.- •}'■ ^■g "^q^i if: Jo to -a < a T»® ;JO S^ ^" O" rt«3 c • O E a » 2 — i • K a) = B) ^ o •- ^ 7 o 1 josoa m02«co =>o3z$iim +^ 13 O (/) (0 ■o c o 0) s- l/^ -C m 5 • r— J3 c E o D • ^ ^— -p O (T3 o c o > N c o S- U) •r— c > i^ ■P J- •r- IT3 C n 3 o E E >i O J3 u CD r— C (0 •r— E ? •r— (0 C S- (0 Q ^«^ T3 c 1/1 n3 4-> fO -P ■P c •»— (0 JH 1 — fO Q.^ U ^ •I— u +J fO in (U •1— ^ J- a» T3 -p c u 03 (TJ in S- (0 T3 x: 50 percent) oiling concentrated in beach wrack at the high-tide swashline. Stems and leaves of Spartina and Avicennia were oiled up to 40 cm above the base of the plant. Those areas that had light to moderate oiling were not severely damaged, while heavily oiled plants were dead or dying by the 11 September survey. Moderately oiled plants showed stress symptoms such as browning of stems, but plant growth was still evident. The higher- than-normal tides from Hurricane FREDERICK pushed oil farther back into the marsh, but at the same time dispersed much of it back into the water. Effects of the oil on animals appeared to be minimal. Li ttorina, a supral ittoral snail, was feeding normally above the oiled areas of the Spartina. Densities were about the same for pre- and post^oiling Li ttorina populations (averaging 9.6 per m pre-oiling and 7.1 per m post-oiling). Many tar balls on the shore were mixed with detritus. In this oiled detri- tus, large numbers of hermit crabs (CI ibanarius vittatus) were observed. Though oil was observed on the mouthparts and walking legs, crabs appeared to be active and showed no abnormal behavior when handled. Two weeks after impact, the short-term effects of the IXTOC I crude oil on the Lydia Anne Channel marsh appeared to be minimal . Some of the plants in heavily oiled areas were dead, but these were in small localized areas. A crude oil spill at Harbor Island on 3 October 1976 had similar results (Holt et al., 1978). Delaune et al. (1979) found that Spartina al ternif lora was capable of tolerating light oiling. Holt et al . (1978) also observed that mangroves were sensitive to heavy oiling, but were able to tolerate light oiling. 121 Toxicity and Analysis of Phytoplankton and Seagrasses This study assessed the acute toxicity of IXTOC I oil to mixed phyto- plankton populations and seagrasses by comparing photosynthetic rates in the presence and absence of a water-soluble fraction (WSF) or oil -accommodated seawater (OAS) preparation. This type of measurement is by nature an acute bioassay, which can only indicate whether the material being tested has an immediate effect on photosynthesis of the cells involved. Earlier studies have shown that seawater equilibrated with No. 2 fuel oil (Pulich et al., 1974; Gordon and Prouse, 1973) and some crude oils (Lacaze and Villodon de Naide, 1976) was inhibitory in varying degrees to photosynthesis of micro- algae (e.g., blue-greens, greens, and diatoms) and mixed phytoplankton samples, with the effect from No. 2 fuel oil being immediate, while the response to crude oil was more delayed or chronic. Seawater samples were collected at the south jetty in Port Aransas before spill impact. The natural phytoplankton population (consisting of diatoms, coccoid greens or blue greens, and green flagellates as determined by cursory microscopic examination) was concentrated within 2 hours after collection by centrifugation at low speed (1000 xg) for 20 minutes. The mixed phytoplankton were resuspended in 10 to 15 m£ filtered seawater for photosynthesis measurements. Photosynthesis and respiration were measured using a sensitive Clark-type oxygen microelectrode system as described by Pulich et al . (1974). All measurements were made at light saturation or higher. Water-soluble fractions (WSF) were prepared by mixing 150 g of crude oil with 1 £ of offshore seawater and shaking for 2 hours, followed by filtering through a 0.4 pm glass-fiber filter. Toxicity of the oil (100 percent WSF) to concentrated, mixed phytoplankton populations was determined by comparing the effect of different seawater-soluble oil extracts with unexposed controls. Two runs were made with mix phytoplankton samples to test the immediate effect of water-soluble fractions on photosynthetic activity. In this case, the concentrated phytoplankton were not exposed to the oil until oxygen measurements were started and then for only about 30 minutes total . Shoal grass (Halodule) and clover grass (Halophila) photosynthesis was measured by H^'^COa uptake as described by Pulich et al. (1976) with one modification - HCO3 was added at a saturating level (200 mg/£). Seagrasses were exposed to oil -accommodated seawater (i.e., the unfiltered seawater phase described above) in the following manner. Intact leaves of Halodule and Halophila were in direct contact with oil micro-droplets during the photosynthetic H^'^COg fixation, including 1 hour in the dark before incuba- tion in the light for 6 to 7 hours. The total quantity of oil present in the incubation bottle was 2.9 mg organic C per 68 mj^ seawater. The results, presented in Table 6.1, indicated no significant change in photosynthetic rate compared with controls for either set of samples. 122 TABLE 6.1 Effect of seawater-soluble fraction from IXTOC I oil on photo- synthesis and respiration by mixed phytoplankton samples. Values are averages of two to three measurements ± range, expressed in |j^ O2 PS'^ pg chlorophyll a per hour. EXPERIMENT I EXPERIMENT II Sample Photosynthesis Respiration Photosynthesis Respiration Control 5.16 ± 0.58 2.58 ± 0.30 2.70 ± 0.23 2.33 ± 0.22 Treated with 4.92 ± 0.40 7.50 ± 0.64 2.58 ± 0.30 2.25 ± 0.16 100% WSF The results obtained from the exposure of seagrasses, Halodule and Halophila, to the oil -accommodated fractions are listed in Tables 6.2 and 6.3. The data suggest strongly that the oil emulsion at this concentration has little or no immediate effect on the photosynthetic activities of both Halodule and Halophi la, as measured by carbon fixation. The lower rates measured in oil -exposed Halodule at low and medium light intensities may be attributed to shading of leaves by abundant oil droplets present in the incubation seawater. At the highest light intensity, oil -treated Halodule achieved the equivalent rate of photosynthesis as the control. For Halophila, there was no difference between the control and oil -exposed sample at medium light intensity. TABLE 6.2 Effect of oil -accommodated seawater on photosynthetic activity* of the seagrass, Halodule wrighti i , measured at 30°C and three light intensities. Rates determined by H^^COg uptake over 6 to 7 hours. Corrected for dark uptake. Photosynthesis Activity'*' Light Intensity Control Oil -Treated Low 9.6 ± 0. 1 7.9 ± 0.2 Medium 13.0±0.6 11.0±0.2 High 12.0 ± 1.0 13.0 ± 0.3 TT values in pg C/mg dry wt/hr; approximately 3.5 pg chlorophyll a per mg dry weight 123 TABLE 6.3 Effect of oi 1- accommodated seawater on photosynthetic rate of seagrass, Halophi 1a engelmannii , measured at 30°C and medium light inti ensity. Rates determined by Hi^COs uptake over 6 hours. Sample Photosynthetic Rate (|jg C/mg dry weight/hr) Control 18.0 ± 1.0 Oil-treated 19.0 ±2.0 Results from these physiological bioassays may be considered evidence that weathered IXTOC I oil (in the form of mousse) would not immediately inhibit photosynthesis or respiration rates of representative, nearshore phytoplankton samples and seagrasses. This information, however, should not be interpreted as evidence that this oil will have no effect (either inhibitory or enhanced) on growth and cell division of the plant species involved. Winters et al. (1977) have pointed out that seawater extracts of fuel oils are quite varied in their immediate effects on photosynthesis. For example, growth of blue-green algae and some green algae was inhibited in water-soluble fractions of New Jersey fuel oil, while only the green algae showed inhibition of photosynthesis. Additionally, pure compounds such as p-toluidine (selectively toxic to blue-greens) and phenalen-1-one (selectively toxic to green algae), which are lethal to the algae mentioned, had no immediate effect on oxygen evolution. Thus, it would not be safe to extrapolate these results to growth of entire Gulf of Mexico phytoplankton populations. At best, we can say IXTOC I oil does not appear to be as toxic as a No. 2 fuel oil. Additional experiments involving growth rate measurements should be carried out for both phytoplankton and seagrasses. Photosynthesis proceeded at approximately 5.16 p£ Og per pg chl. a per hour for Run I and approximately 2.70 p£ Og per pg chl. a per hour for Run II. Respiration after photosynthesis was variable, but did not appear decreased. Additional tests conducted by exposing mixed phytoplankton (mostly diatoms and green flagellates) to 100 percent WSF for up to 8 hours in dim light revealed no significant differences in the rates of phytosynthesis between controls and treated samples. However, there was a significant (p < 0.05) reduction (20 percent of respiration in the WSF-treated samples (4.8 in WSF sample compared with 6.0 pJi Og per pg chl. a per hour in con- trol). This was particularly noticeable for 2 to 3 minutes after photosyn- thesis, although later respiration measurements were also depressed. STUDIES OF SAND BEACHES Sand beaches occur on the seaward side of the barrier islands, compris- ing 22.8 percent of the south Texas coast. A considerable body of literature documents research on sand beach organisms (see Hedgpeth, 1953), including 124 studies on plankton and productivity (McFarland, 1963a), dominant macroin- vertebrates (Whitten et al., 1950; Loesch, 1957; Hill and Hunter, 1973), infauna (Keith and Hulings, 1965), and fishes (Gunter, 1958; McFarland, 1963b). Because the sand beaches were the heaviest oiled areas, much of the ecological monitoring effort was directed there. This included detailed monitoring of birds and infauna inhabiting oiled beaches. Wading and Shorebird Studies Major oil spills may have a devasting effect on marine bird popu- lations (Lincoln, 1936; Aldrich, 1938; Bourne, 1968; Smail et al., 1972; and others). Fouled plumage looses its waterproofing and insulative proper- ties rendering a bird susceptible to temperature extremes (Hartung, 1967). When ingested during preening or feeding activities, toxic fractions of oil may cause tissue damage and eventual death. Marine bird populations also may be indirectly affected by contamination of their food supply (Vermeer and Anweiler, 1975). Wading and shorebird studies were designed to assess the effects of the IXTOC I oil spill on the marine bird populations associated with the barrier islands and lagoons of the lower Texas coast. Assessment of eco- logical damage was based upon adequate pre-damage population data (Fidel 1 and Dubey, 1978). Although McCamant and Whistler (1974) and Blacklock (1977) have prepared checklists of Padre Island birds, no quantitative analysis of avian population cycles on the lower Texas coast has ever been conducted. Thus, in addition to assessing the effects of the IXTOC I oil spill on marine bird populations, this study may also provide baseline information for future activities. Aerial Counts Ten aerial bird consenses were conducted on Mustang, Padre, and Brazos Islands between 15 August 1979 and 5 October 1979. These surveys, done by helicopter, were conducted to provide up-to-date information to the NOAA-SSC on the use of the gulf beaches by coastal bird species. IXTOC I oil was present on the beaches when the surveys were started and no prespill data were available to make comparisons. Surveys on 15 August and 25 August indicated beaches were being used by resident species such as sanderlings (Cal idris alba) , willets (Catoptro- phorus semipalmatus) , ruddy turnstones (Arenaria interpres) , laughing gulls (Larus atrici 11a), Caspian terns (Sterna albifrons) , forster's terns (Sterna forsteri ) , sandwich terns (Sterna sandvicensi s) , and great blue herons (Ardea herodias). A tropical depression passed through on 31 August to 1 September. A 2 September survey showed an influx of migrant species, especially knots (Cal idris canutus). Following a mid-September tropical storm that resulted from hurricane FREDERICK, much of the oil was removed from the beaches and the number of birds using the beach areas increased dramatically (Figure 6.2). 125 Figure 6.2 Number of birds versus beach oiling expressed in thousands of tons from 15 August to 3 October 1979. Correlated with the tropical depression and subsequent removal of oil from the beachface, note a steady increase in the number of birds. m Q 5 10000 - m li. O cc LU m BIRD POPULATION VS. BEACH OILING OIL BIRDS TROPICAL DEPRESSION / —I 1 I I I 1 1 I I 1 I 15 20 25 31 5 10 15 20 25 30 5 AUG. SEPT. OCT. 1979 During heaviest oiling, total bird populations remained low (below 4,000 individuals), indicating probable avoidance of oiled beaches. Sub- stantial increases in bird populations (to about 13,000 individuals) occurred after the tropical depression removed oil from beaches and newly arriving, migratory species appeared. Beach Survey A total of 15 bird census trips were made on the beach in each of three study areas: (1) from Brazos Santiago Pass to Mansfield Pass (South Padre Island); (2) from Mansfield pass to the south end of Malaquite Beach (Padre Island National Seashore); and (3) from the north end of Malaquite Beach to Aransas Pass (Northern Padre Island and Mustang Island). The three beach censuses were conducted using a four-wheel-drive vehicle. During each beach census, all birds using the foreshore and nearshore waters were identified and recorded according to odometer mileage from a reference point. The position of each bird on the beach was registered with reference to distance from the surf zone. For example, a bird in the immediate vicinity of the swash zone or on damp sand up to the high tide line was noted as being in the "foreshore"; the area above the "foreshore" that received storm tides and other periodic inundations was designated the "berm"; and from the "berm" to the base of the foredune ridge, the dry sand area was called the "backshore." Whenever flocks of birds were encountered, the number of individuals of each species in the flock was noted, and position was recorded for the flock, not the individuals. 126 On each census trip, the location and extent of oi 1 -contaminated areas were recorded, including the type of contamination (i.e., oil sheen, tar balls, or mousse) and the distribution of the oil in each habitat. All birds were observed for evidences of oil on plumage, bill, and feet. Oiled birds were counted separately by species, and notes made on the extent and position of the oil on the body of each contaminated bird. Severely oiled birds and carcasses were collected and given to the U.S. Fish and Wildlife Service. The activity patterns of oiled and oil -free birds were compared. Initially, several species of birds were observed, but most data were obtained for sanderlings (Cal idris alba) and willets (Catoptrophorus semi- palmatus). Methods were similar to the time-budget studies of Dwyer (1965) and Afton (1979). Individuals were observed with binoculars (7x) and activites were tape recorded for 10 to 15 minute intervals. Activities were separated into six categories: (1) feeding, (2) resting (loafing and sleeping), (3) comfort movements, (4) locomotion (walking and flying), (5) alert, and (6) social interactions (threats, chasing and pursuit flights), Calculations of the percent of time spent in various activities were based on the amount of time individuals were actually observed. Observations ended when birds became visually obscured. Avian populations in beach habitats. Bird population densities re- sponded directly to oil concentrations on the beach. Unlike most other oil spills, the IXTOC I oil initially washed ashore in isolated patches. As these patches washed in, birds abandoned affected habitats and redistributed themselves in areas that remained relatively oil-free. By the end of August, however, most of the foreshore was coated by heavy concentrations of tar and oil. Avian populations on the beach de- clined from pre-impact densities (Figure 6.3). Since no oiled shorebirds were ever found dead, the decline in bird density in beach environments probably resulted from habitat shifts. Many birds may have abandoned the beach and sought food in secondary locations. Large numbers of sanderlings were observed feeding on the periphery of rain pools in the center of Padre Island and in similar habitats on the mainland. Since sanderlings and willets are distributed evenly along the fore- shore during the fall and winter (Myers et al . , 1979), their populations may serve as an indicator species for oil contamination. Populations of both species declined during the period of heavy oil concentration (Figure 5.4). After the beaches were cleaned, these species reinvaded the fore- shore. However, their population densities after impact were barely equal to (sanderlings) or just below (willets) densities before impact. Their population density should have increased as a result of migratory influx (Oberholser, 1974). Thus, the oil may have reduced the populations directly or may have eliminated or contaminated a portion of their food supply. After a succession of storm tides cleaned oiled beaches, bird popula- tions increased. Most population increases were due to an influx of migratory birds, particularly knots (Cal idris canutus) and several species of gulls and terns. Many species of migratory birds use the beach as a staging area for seasonal movements. Their numbers fluctuate as flocks 127 200- lU -J oc HI a. CO Q DC QQ 100- 14 17 .21 24 29 31 August 8 11 21 22 26 27 29 2 September October SURVEY DATES Figure 6.3 Average number of birds per mile on each of 15 surveys between 14 August and 2 October at oiled beaches in Padre Island National Seashore. Note the decrease in number of birds per mile during the period of heaviest oiling at the end of August and the beginning of September. move in, feed, rest, and then move on. Unfortunately, there is no baseline data for comparisons of densities along the Texas coast. Thus, it is difficult to assess population gains or losses. The oil on the beach did cause habitat shifts within the beach area. When oil concentrations increased on the beach, birds moved to the berm and backshore areas (Figure 6.5). Later, after oil concentrations decreased, birds returned to the foreshore. It is likely that during the period of oil impact, many birds were suffering food stress. Species that normally feed in the swash zone were forced into drier, less productive feeding habitats. Burnett and Snyder (1954) noted that eiders were forced to feed upon less favored prey as a result of an oil spill. Gene Blacklock (pers. comm. ) collected several sanderlings on northern Padre Island and found them to have low fat reserves and little food in their digestive systems. Oiled birds. The percentage of birds with oil on their plumage never exceeded 10 percent (Table 6.4). However, some species were more prone to oiling than others. During the initial stages of oil impact, royal terns 128 IIJ LU o QC CD 10- 30- 10- Willet Ir^rnn nnl Sanderling 1 6 9 16 16 21 22 22 25 28 29 29 4 6 6 September October SURVEY DATES Figure 6.4 Average number of birds, sanderl ings, and willets, per mile during each of 15 beach surveys through Padre Island National Sea- shore between 1 September - 6 October 1979. Note the decreas- ing and low numbers in mid- to late September during the heaviest oiling of beaches, and the resur- gence in numbers in late September and early October. were the most heavily oiled species of bird. While loafing, royal terns sat along the high-tide line where the greatest concentration of tar balls occurred. By the end of August, approximately 40 percent of the royal terns had oil on their breast feathers. However, by mid-September, royal terns avoided the high-tide line and congregated on the berm above tar concentrations. Most of the royal terns concentrated in relatively oil-free areas such as at the mouth of Mansfield Pass and in the vicinity of water- filled passes. The percentage of oiled birds increased during tions in late August. Most of the birds oiled duri sanderl ings, willets, snowy plovers (Charadrius ale plovers (Charadrius melodus) , and other shorebirds. birds was oiled in three ways: (1) by sitting in p transferring oil from contaminated plumage to other while preening, and (3) by walking through oil, the the ear region) with their foot. Some birds (25 wi 10 piping plovers, four black-bellied plovers, thre to 75 percent of their body covered by oil. Based the heavy oil accumula- ng this period were xandrinus) , piping The plumage of these atches of oil, (2) by areas (wings and rump) n scratching (usually llets, 40 sanderlings, e snowy plovers) had up on information from an 129 Figure 6.5 Percent of all birds in each portion of the beach (fore- shore, berm, and backshore) on each of four surveys between 9 September and 6 October 1979 at oiled beaches in Padre Island National Seashore. Note the heavy utilization of backshore areas (in black) during the heaviest oiling in mid- September and the subsequent utilization of foreshore areas following the tropical storm in late September and early October. Foreshore Berm Backshore lOOn CO Q m < I- o H I- Z HI o oc HI September October SURVEY DATES earlier study on the effects of oil accumulation on birds (Eastin and Hoffman, 1978), it is unlikely that the heavily oiled birds survived. Many wad oil on their up to 20 cm i flying and wa nycticorax) a of tar and oi its breast pi southward in lations. On globs on thei ing birds that frequented the feet. Two great blue herons n diameter on their feet and Iking. Many immature black-c nd several snowy egrets (Egre 1 on their feet; one snowy eg umage. Cattle egrets (Bubalc the fall, frequently rested i many occasions, flocks of up r feet. beach had large globs of tar and (Ardea herodias) had balls of tar exhibited some difficulty in rowned night herons (Nycticorax tta thula) also had large balls ret also had smudges of oil on us ibis), which migrate in flocks n beach areas of dense tar accumu- to 15 cattle egrets had heavy tar 130 TABLE 6.4 Percent of birds with obvious oil on feet and plumage on Padre Island National Seashore. J., . _ — _ — ___ . — _ . ■■ ■ - ■ ■• ' — — , - - ■ . ■ I- .^ Total Oiled Percent Date Birds Birds Oiled Aug. 14 4654 372 8.0 17 4349 139 3.2 21 5183 91 1.8 24 2617 187 7.1 29 2364 159 6.7 31 2081 171 8.2 4654 372 4349 139 5183 91 2617 187 2364 159 2081 171 2177 37 1516 20 2072 23 3287 40 2936 46 13,429 54 6973 43 4289 27 Sept. 4 2177 37 1.7 1.3 11 2072 23 1.1 21 3287 40 1.2 22 2936 46 1.6 25 13,429 54 0.4 27 6973 43 0.6 29 4289 27 0.6 Oct. 2 6397 12 0.2 It was impossible to speculate on oil-related avian mortality. Few carcasses or oil-immobilized birds were found. Carcasses that were found were mostly pelagic species. Shorebirds that succumbed to either direct or indirect effects of oil pollution were likely eaten by coyotes. Coyotes were often observed patrolling the beaches in the early morning and possibly preyed upon sick or dead birds. Time-budget studies. A total of 125 sanderlings and 58 willets were observed for a total of 634 and 328 minutes, respectively (Table 6.5). Whenever possible, observations on oiled birds were paired with TABLE 6.5 Total time of time-budget studies of sanderlings and willets, Minutes of Species Condition Observation Sanderling Oil-free 336 Oiled 298 Total 634 Willet Oil-free 170 Oiled 158 Total 328 131 observations of oil-free birds in the vicinity during the same time of day to eliminate variations in behavior due to differences in habitat quality, time of day, and tide cycles. Oiled sanderlings and willets spent less time feeding and more time resting and engaging in comfort movements than did oil -free birds (Figure 6.6). Hartung (1967, unpubl . manu. ) found similar reductions in feeding activity among oiled ducks. Presumably, reductions in feeding activity were related to oil-induced irritations of the digestive tract. Oiled ducks increased their use of body fats increasing the rate of starvation after oiling. Reduction in time spent feeding also translates into less energy metabolized; therefore, it was probable that oiled sanderlings and willets experienced similar stresses. Figure 6.6 Time budget comparisons of oiled and clean sanderlings and willets, during beach surveys on oiled beaches in Padre Island National Seashore. Among several trends note decreased feeding behavior and increased resting behavior in oiled birds. 10- 10 10 I- 10 z LU CL CO 10^ HI 30- UJ HI °- 70 SO- SO- 10. Social Interaction ' ■ Alert Threat Comfort Locomotion ' ' Resting A 1 Feeding Oiled Clean SANDERLING oiled Clean WILLET 132 Mortal ities Twenty-six oiled birds were recovered and turned over to U.S. Fish and Wildlife Service rehabilitation centers. Eight of these birds were blue- faced boobies (Sula dactyl ati a). These birds nest in the Yucatan and are entirely pelagic feeders (Palmer, 1962). Although no boobies were observed during the coastal pelagic census, undoubtedly many were affected by the oil spill. Since these birds rarely were seen in coastal waters (Palmer, 1962), it was probable that those individuals that washed ashore represented only a small fraction of the individuals that became oil-coated; most individuals were probably eaten by predators or sank after dying. The following is an account of the fate of oiled birds recovered during the bird-beach survey: 1. A heavily oiled pied-billed grebe was found floating to shore in the surf approximately 15 miles north of Mansfield Pass. The bird was alive, but so heavily covered with oil (thick mousse-like consistency) that it could not fly. The bird was given to U.S. Fish and Wildlife Service for rehabilitation, but it died during the cleaning operation. 2. A sanderling with a broken wing was collected in the foreshore approximately 25 miles north of Mansfield Pass. The bird was alive and its broken wing was covered with a thick accumulation of oil. The bird was turned over to U.S. Fish and Wildlife Service for rehabilitation, but it was subsequently destroyed. 3. A heavily oiled pied-billed grebe was found sitting in the fore- shore approximately 20 miles north of Mansfield Pass. The bird was alive when captured, but died within 30 minutes. The carcass was frozen and turned over to U.S. Fish and Wildlife Service for chemical analysis. 4. A black-necked stilt was captured on 11 September at a rain pool near the base of sand dunes, approximately a half mile south of the south boundary of Malaquite Beach. The bird had a 50-cm-diameter patch of oil on its breast feathers and oil on its bill and feet. It could not walk without falling to one side. The bird rehabilitation center was closed, so the bird was taken home, kept warm, fed water and shrimp slurry, and kept in a quiet dark place. The bird lived until 13 September. The carcass was turned over to U.S. Fish and Wildlife Service for chemical analysis. Toxicity Studies Immediate concern arose for two endangered species, the migratory peregrine falcons (Falco peregrinus) and the wintering whooping crane (Grus americana) , which were thought to be at risk. The hazards of feather oiling were well known, but the effects of consuming oil had not been tested with either birds of prey or cranes. Toxicity tests were conducted at Patuxent Research Center to examine this question. Tests were made with surrogate species: American kestrels (Falco sparverius) for peregrines and greater sandhill cranes (Grus canadensis) for whooping cranes. In the kestrel studies, birds were fed diets containing 3 percent IXTOC I oil or 3 percent Prudhoe Bay crude oil for 28 days; survivors were fed untreated 133 diets for 29 additional days. Birds did not avoid food into which oil was mixed. Kestrels fed diets containing 3 percent oil lost weight and some died (2 of 16 fed IXTOC I oil and 3 of 6 fed Prudhoe Bay oil). Survivors gained weight when untreated food was restored. In the sandhill crane studies, birds were administered (orally) a single daily dose of 2 to 10 m£ of Prudhoe Bay crude oil per kg of body weight for 4 to 24 days. Cranes were dosed in this way because they avoided feed into which oil was mixed. Two birds each received more than 1 £ of oil during the study. Prudhoe Bay crude oil was used because suffi- cient IXTOC I oil was not available. No birds lost weight, although oil- dosed birds became progressively more lethargic after 10 days of dosage, and relative liver weights were greater at necropsy. It was concluded that: (1) the toxicity of crude oil to these two species was not greatly different from toxicity to other species of water- fowl and (2) it was not likely that either peregrines or whooping cranes would be in hazard due to consumption of oil -contaminated prey. Beach Fauna Pre-spill, baseline sample collections of infauna focused on the supratidal, intertidal, and subtidal zones of barrier island beaches which had the highest probability of being oiled and for which little baseline information was available. Characteristic, dominant intertidal and benthic infauna of Texas beaches include coquina clams (Donax), polychaete worms, mole crabs (Emerita) , and haustoriid amphipods. This was characteristically a low diversity, high-density community. Despite the relatively low number of species, the number of individuals may be tremendous. Loesch (1957) estimated over 10,000 coquina clams per m^ at one station on a Texas beach. Infaunal Studies Infaunal samples were taken with can grabs (12-cm diameter; 0.12 m^ volume) at the upper (berm crest), mid (mid-beachface) , and low (top of the toe of the beachface) portion of the intertidal zone as well as subtidal ly in the troughs and crests of the innermost three bars. This was done at five transects (1, 2, 3, 4, and 5; Figure 6.7) before (23 July to 10 August 1979) and after (24 to 29 September 1979) impact of oil. Samples were placed in a solution of propylene phenoxitol for 20 minutes, then transferred into 10 percent formalin containing Rose Bengal. After two weeks, the samples were sieved to 0.5 mm and the remainder put in 45 percent isopropyl alcohol. Organisms were removed from the sediment using a dissecting scope. Taxonomic analysis was to the lowest possible level, usually to species. Mann-Whitney U-tests were used for significance testing to determine changes in species abundance, richness, and diversity of the dominant macro-infaunal groups: crustaceans, annelids, and molluscs. Significance was at the p < 0.05 level. 134 CORPUS C we)^^c° I N 0 30 0 KILOMETERS 30 MILES MEXICO Figure 6.7 Locality of biological monitoring stations throughout the oiled beaches in south Texas. 135 (0 < z u >- -I o a. D < UJ o < (0 « e a. I CO cc III m Z Z g < I- co s- o •I— > r- CO I fO E -a "- >, (/) O) 0) to S- I o a. O I/) C Ol (0 s- Q. — X (0 Ol o) -a ■p to -P •r- C I/) OJ C 4-> O I/) U -r- fO +-> s- i- (T3 +-> 10 C +J S- irt O 0) 4- Q£ to -P • C -P O U C to O Q. Q. E E -r- O U r— fO Q. c to 3 (0 S- <4_ CU C +J •r- 4- o nj J- U "O 03 C E n} I— Q) (0 5- 3 O T3 M- •r- CU > ^ "O W) c c •I- o H- -P O (tJ +-) to in 0) •I- cu ■P > •r— 'f— U) to c c O) CD ■a -p c c •■- O I ..- o ■p -p (0 -r- I— W) 3 Q. a. •!- (0 ■a 0) 5 o -c -a 10 0) to O c ^ (0 10 U i/) fO to r- 3 fO S- > C_J -t- I/) "O c •!- O -P D. S- (/) a; 0) -P s- c 0) ^ QJ I— ^ -P . C OJ •«- to 0) S- -D U C C to CSJ I/) cu to -p cu o fO 'r- -C 4-> U (0 >)-p I— to o Q-r— ■o c fO to c - o 0) -P > •!- r— -O fO c > o •I- u Si to •(- C Q. fO to cu I U -P ro if) I/) to (U (0 +J "O t/5 cu 5 -P O fO to to (U ^ •!- O +J jz tn 3t c (U ► -0 ro "O • 0) o to Z (0 cu cu s- ■P u •I- c -p t/) Q 3 s- -o >— 03 CO C ■O •!- •r- -a -P 3 S- r— 0) u -P c C -r- u |BPI)je)U| IBPUqns 00 -p . fO t£) to s- c 3 O CT N "4- 0) 5- tn Q. Q. 3 C o cu i- cu O) 5 +J u cu •r- ^ E to 0) S- u u to a. E ^ 0) cu I— ■p ^ s- CU (0 c o 3 J3 > T- Q. I/) .— cu f— +-> ro cu fO c ^ •I- U en c •r- o sivnaiAiQNi do daannN 136 Results showed a visible, though not significant, decrease in total faunal population densitites for the pooled intertidal zones (Figure 6.8). In separate comparisons of the upper, mid, and low intertidal zones, post- spill densities were only significantly (p < 0.05) decreased in the low intertidal zone (Table 6.6). Total post-spill densities at stations 1, 4, and 5 were decreased; but only at station 4 was the decrease significant (p < 0.05). Post spill total densities at stations 2 and 3 slightly increased (non-significant), perhaps due to the small total densities observed at these two stations. Additionally, post-spill sampling at stations 2 and 3 indicated a substantial (non-significant) increase in polychaete populations and a slight (non-significant) increase in mollusc populations (Figure 6.9). Post-spill crustacean population densities, consisting primarily of mole crabs and amphipods, were significantly (p < 0.05) decreased. Amphipods had the largest decrease in densities (in total numbers, per se) ; however, only mole crab densities were signifi- cantly (p < 0.05) decreased (Table 6.7). The subtidal zone had a significant (p < 0.05) decrease in total population densities (Table 6.8). Crustacean densities were significantly (p < 0.05) lower in post spill samples (Table 6.7). Haustorid amphipods, which were the dominant macro-infauna in the subtidal zone, also had signi- ficant (p < 0.05) decreases in population densities in post-spill samples. Figure 6.9 shows that, with the exception of polychaetes at station 3, there was a slight decline in all post-spill subtidal populations. Popula- tions in both the second trough and second sand bar had significantly declined from the pre-spill densities (Table 6.8). In general, population densities declined from pre-spill to post spill measurements. Crustacean populations in both intertidal and subtidal zones were significantly changed in comparisons of July, pre-spill sampling to the September, post-spill sampling. However, several combined factors may have caused these changes. First, the IXTOC I oil may have impacted the communities. Second, the occurrence of a tropical depression and storm during the first half of September cleaned off the beaches, but at the same time reshaped the beach profile. The berm crest was flattened, as well as the rest of the beach, back to the foredune ridge. The tremendous agitation of sediment during that period may have affected both intertidal and subtidal populations. Little information was available on the effects of storms on beach infauna. Third, seasonality may have played a role in population density. Loesch (1957) found a decline in the Donax population on Mustang Island, Texas, between August and October. Matta (1977), in a North Carolina barrier island beach infauna study, found seasonality affected all species with a decline occurring in the fall. Because the IXTOC I oil arrived at Texas in late summer and early fall, any one of these factors or any combin- ation of the three may have been responsible for observed population decl ines. 137 TABLE 6.6 Test for significance of impact on species abundance, richness, and diversity of macro- infaunal communities at south Texas beaches. H = high M = mid, L = low, and COM = combined zones of the intertidal zone. Pre-Sp ill Post Spi ill Station No. H M L COM H M L COM NUMBER OF INDIVIDUALS (N) 1 2 3 4 5 1 3 2 207 303 103.2 7 64 6 61 396 119.4 73 63 18 103 9 81 130 26 371 708 263.2 3 0 4 6 4 30 151 51 33 26 58.2 13 8 3 11 7 46 159 58 50 37 Mean (X) 53.2 3.40 8.40 70.00 Standard Deviation 127.6 136.7 35.1 251.7 1.96 47.0 3.44 45.01 II 1 (sig) U value ^ ^'' 13.5^^ 13^^ 23* 18^^ NUMBER OF SPECIES (S) 1 2 3 4 5 1 1 2 6 3 2 4 3 5 8 11 6 3 8 5 12 8 5 12 10 9.40 3 0 1 1 1 2 6 4 4 1 7 3 3 6 3 8 8 6 8 4 Mean (X) 2:60 4.40 6.60 1.20 3.60 4.40 6.80 Standard Deviation 1.85 2.06 2.73 2.65 0.98 1.50 1.74 1.60 U Value ^"^'9^ 18.5^^ 15^^ 18^^ 19.5^5 DIVERSITY OF INDEX (DS) 1 2 3 4 5 0.00 1.00 0.00 1.15 1.61 1.40 1.22 2.50 1.65 1.72 4.70 1.96 2.67 4.71 5.14 5.47 2.40 3.65 2.60 3.17 3.00 0.00 1.00 1.00 1.00 1.15 1.18 1.94 1.83 1.00 7.80 1.87 1.00 5.00 4.20 2.02 1.29 1.97 3.64 1.34 Mean (X) 0.75 1.70 3.84 3.46 1.20 1.42 3.97 2.05 Standard Deviation 0.65 0.44 1.27 1.09 0.98 0.39 2.41 0.85 U value ^'■'9^ p < 0.05) 11.5^^ 17^^ I4NS 22* *Significant ( 138 1000 - -I 800 < 9 I- 600 H cr LJJ I- 400 H 200 - 1000 - 800 - < G .— 600 -I m D CO 400 - I 1 Prespill Postspill 1302 P ^-J 1829 200 - r~| ^ I JXjU Total STATIONS Figure 6.9 Total density of organisms at five site-intensive stations where intertidal and subtidal macroinfauna were monitored. Data are presented for pre-spill and post-spill periods. Intertidal stations show variable but usually decreasing numbers in post-spill samples while the subtidal zone consistently shows decreases in density of macroinfauna. 139 TABLE 6.7 Test for significance of impact on abundance of dominant inter- tidal macro-infaunal species at south Texas beaches. Stations 2 and 5 were not fully sampled because of inclement weather. ^ station No. Haus Pre tori us Post Donax sp. Scolopelis Pre Post Pre Post Emeri Pre ita sp. Post Lumb Pre rineris Post NUMBER OF SPECIES (N) Intertidal 1 2 0 67 5 3 29 2 4 9 32 3 51 140 8 2 0 1 0 5 1 6 3 000 11 5154 3 4 ■ 215 6 71 4 9 25 43 7 20 5 227 0 297 2 135 2 12 1 20 U value ^^^9) 17NS ^^NS ^^NS ^2* ^,NS NUMBER OF SPECIES Subtidal 1 42 0 28 8 3 6 2 7 2 6 2 71 20 15 6 10 1 2 4 3 19 3 23 5 108 35 1 3 9 3 117 33 4 321 0 124 98 3 8 4 12 48 25 5 29 g) 3 49 27 ^NS 8 8 7 2 9 10 U value ^^^ 9* ^NS 3NS ^NS b ^Significant (p < 0.05) Upper Beach Faunal The supratidal ghost crabs and the wrack-associated amphipods of the south Texas sand-beach habitats were examined for impacts resulting from IXTOC I oil. Impacts were observed incidental to studies of oil distri- bution and geomorphology. The ghost crab (Ocypode quadrata) is the dominant consumer of the supral ittoral portion of Texas exposed-sand beaches (Hill and Hunter, 1973). Vertical distributions and relative abundances were measured within randomly placed 1 m^ triplicate grids at intervals along three beach transects (beach stations 6, 7, and 8) before (25 July to August 1979) and during (2 September 1979) the impact of IXTOC I oil. During impact, oil coverage was moderate to heavy. 140 (0 c 3 ■o fO 0) >*- c c .i— I— X} o E s- O o u eo E II >♦- z: o o o U) in «s 0) S- c (T3 ^ ^ '<- II s- CQ T3 C #> (0 ♦- in • r— S- s_ c o fO CT <4- OJ c in 10 ■t-> ■p II t/) to (U « t— in (U X3 •r- c •P fO •r- C <~ 3 in 00 E a> . E c (D O o u N LU _J 00 CSJ 00 in r— ^ o CO c\j CSJ m CD o 00 r~* >— CSl I— CSJ CSJ I— ro «;t ID ID I— r— CO I— CSJ 00 CSJ ID o r^ .— UT) I— CSJ 00 CO .— ID t— t— CO r— «J- «:J- O tn ID ^ r— O ^ CSl CsJ r- <^ 00 CSJ C7) r*> r>. «;I- I CD -— en 00 I CO 1 .- 00 1 ^ r^ in ro 00 1 CSJ ID 1 — r— 1 1 — o CD ID CO l£) (T> en o in r— ID CO ^ CSJ CD ^ CO I — in (Ti in CSJ CO C7> CO o >— iT) r^ en «a- r— CO en CSJ 00 CSJ CO CSJ r^ r— CSJ CSJ CSJ CSJ O O in r— r- 1/5 C_) r»- en in 00 r^ CO en 00 r^ o ID ID in r^ CSJ ID in CO o ^ 171 • z P>. CSl ^ 00 z CSl 00 in r^ CSJ (Ti ID en 00 z ID CSl in oo z ^ r^ in 1X3 ,— CM 00 ID CO r^ CO 00 ID 00 CSJ 0) 3 Q I— (13 OO > 141 At heavily oiled station 6, a significant (p < 0.05) change (determined by the Mann-Whitney U-test) in vertical distributions of ghost crabs was observed. At moderately oiled station 8, a significant (p < 0.05) change was also observed, but at station 7 (also moderately oiled), no significant change in vertical distribution was noted. Therefore, it appears that ghost crabs are able to move higher up on the beaches following oiling, but the response varies between localities. The amphipods, Orchestia and Talorchestia, are most commonly associated with beach wrack (usually the alga (Sargassum) on Texas sand beaches (Hedg- peth, 1953). Wrack-associated amphipods were observed in light concentrations under beach wrack before oil impact (July and August 1979), but were absent following impact at five or six transects that were revisited on 2 and 6 September 1979. This same loss of wrack-associated amphipods was noted during the PECK SLIP spill study of December 1978 (Robinson, ed. , in press). Infauna Laboratory Toxicity Analysis In additior> to field studies laboratory studies were concentrated on organisms living in outer coastal barrier island beach habitats because of the high probability that animals in these areas would be oil-impacted. One of the immediate questions faced was the potential toxicity of IXTOC I oil to marine biota inhabiting these areas. The objective of these experiments was to quantitatively define the acute toxic effects of this oil on common invertebrates of the Texas coast, which were likely to be impacted in sandy beach environments. The acute toxic effects of IXTOC I oil on three species of invertebrates (a sandy beach bivalve, Donax variabilis; an intertidal, burrowing, detrital-feeding polychaete, Scolelepis texana; and a burrowing tidal crustacean, Emerita sp. ) commonly found in beach habitats were measured in laboratory toxicity tests. Additionally, sublethal effects induced by oil-exposure, including behavioral and physiological changes, were measured. These lethal and sublethal studies provided useful information in predicting potential impacts to sand beach fauna. Intertidal organisms and sediments used in this study were collected from the beaches of Mustang and St. Joseph Islands, using standard inverte- brate collection techniques. Collected sediments were sieved through a 500-p mesh sieve to remove macrofauna, and dried for 48 hours to kill any remaining fauna. Collected beach fauna were maintained in salinities of 34 0 ^ /oo and at a water temperature of 25°C. Sediment selectivity tests. The bottom sections of 0.24 £ (h pint) capacity milk cartons, cut 6 cm from the bottom, were filled with dried beach sediment that had been mixed with different concentrations of whole oil. The range of concentrations included controls (no oil in sediments), 0.1, 1.0, and 10.0 percent oil in sediment. The cartons containing control, 0.1, and 1.0 percent oiled sediment were placed randomly side by side in a 20-gallon aquarium. The 10 percent oiled sediments and unoiled sediments (controls) were placed in a separate, 10 gallon aquarium to prevent contam- ination of sediments at the lower oil-exposure concentrations (0.1 and 1.0 142 percent). The aquaria were slowly filled with beach water (34 /oo salinity) to a depth of 12 cm over the surface of the sediments. Mole crabs (Emerita sp.) were introduced randomly over the water surface. The water was aerated and maintained at 25°C. One experiment was run for 24 hours and a second was run for 72 hours. At the end of each test, water was slowly drained to below the surface of the sediment containers. The contents of each carton were sieved through a 500-p mesh sieve, and the living and dead mole crabs counted immediately. The results of the 24-hour, sediment-selectivity tests suggested that mole crabs had a definite preference for the less oiled sediment. There was a significant (p <0.05) difference between treatments as tested by one-way ANOVA for these 24-hour tests. Thirty-five percent of the crabs were observed in the control sediments, 28 percent in the 0.1 percent oiled sediments, 25 percent in the 1 percent oiled sediments, and 13 percent in the 10 percent oiled sediments. Less than 1 percent mortality was observed in all treatments over the duration of exposure, and no treatment showed significantly greater mortality than the controls. The 72-hour, sediment selectivity tests indicated there were no signi- ficant (p <0.05) differences in the selection of treated and control sediments by the mole crabs. No dead crabs were observed in the control sediment. Mortality was 1 percent in the 0.1 percent oiled sediments, and 2 percent in the 1.0 percent and the 10.0 percent oiled sediments. Toxicity tests. Oil accommodated seawater (OAS) was prepared by shaking a 1 percent mixture of IXTOC I mousse (collected by the U.S. Coast Guard Cutter POINT BAKER) in seawater for 1 hour in an Eberbach shaker. After allowing this mixture to settle for 1 hour, the aqueous phase contain- ing the 100 percent OAS fraction was siphoned off. This stock solution, which contained approximately 25 mg/£ total hydrocarbons, was used to prepare different exposure solutions for each of the toxicity tests. Calculated, treatment-exposure concentrations of OAS for each group of test animals were 0 (control), 5, 15, 30, and 60 percent. Water samples taken after 24 hours of exposure indicated a significant evaporation of hydrocar- bons. Therefore, each test container of mole crabs, surf clams, and poly- chaetes had 25 percent of the water removed and replaced with a fresh mixture of exposure solution, daily. Four groups (replicates) of mole crabs, surf clams, and polychaetes, consisting of 10 animals per group, were exposed to each treatment con- centration. Mole crabs and polychaetes were placed in 11.4 cm finger bowls containing approximately 1.5 cm of sediment and 200 mS. of 34 /oo, aerated seawater. Surf clams were placed in 11.4 cm finger bowls containing 3 cm of sediment and 200 m£ of 34 /oo, aerated seawater. All tests were con- ducted at 25°C. Test animals were fed rotifers (Brachionus pi icati lis) daily. Both survival and mortality were recorded daily for each finger bowl. Behavioral observations for mole crabs (burrowing versus nonburrowing before being presented a food source; feeding versus nonfeeding when pre- sented a food source, and burrowing versus nonburrowing after being presented a food source); surf clams (continuously pumping, intermi ttantly pumping, or non-pumping after being presented a food source); and polychaetes (per- centage of worms extended from burrow or on sediment surface; percentage of worms burrowing; and percentage of worms producing feces after being presented a food source) were recorded daily. 143 All experiments were conducted for 96 hours. Mole crab. Percent mortality, percent survival, and percent behavioral . activity (number of mole crabs exposed above the sediment following food stimulation) are recorded in Table 6.9. No mortalities of mole crabs were recorded for any of the OAS treatments. However, unretrieved animals a well as pieces of mole crabs and molts may represent mortalities that could not be verified without an in-hand dead specimen. No acute, sublethal behavioral effects, as determined by mole crab activity observations, were measured in different treatments. Behavioral activity in both control and oil-exposed mole crabs decreased throughout the 96-hour period. TABLE 6. 9 Results of mole crab toxi city tests and b ehaviora 1 stud ies. Treatmer It % Mortality %_ Survival 96-hr % Act after 24-hr ivity Food 48-hr # Vi Stimu 72-hr sible lation (%) 24-hr 48-hr 72-hr 96-hr 96-hr Control 5 OAS 15 OAS 30 OAS 60 OAS 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 95 98 98 75 100 35 60 68 63 78 63 80 70 58 70 40 50 50 60 53 18 33 33 25 38 Surf clam. Results of surf clam toxicity tests and behavioral studies (number of surf clams with siphons extended and working, following food stimulation) are recorded in Table 6.10. No mortalities were recorded for any of the surf clams in the OAS treatments, while there was 8 percent mortality measured in the controls. All test animals were retrieved from the experiments. There were no significant sublethal effects measured in comparisons of behavioral activity observations in control and oil-exposed surf clams. Behavioral activity decreased throughout the 96-hour period in both control and oil-exposed surf clams. There were no behavioral differences measured between different OAS concentrations. 144 TABLE 6.10 Results of surf clam toxicity tests and behavioral studies % Act- ■ V i ty # Visible Treatment % Mortality after 24-hr " Food 48-hr Stimu" 72-hr ation (%) 24-hr 48-hr 72-hr 96-hr 96-hr Control 0 0 0 8 40 33 30 5 5 OAS 0 0 0 0 53 38 28 25 15 OAS 0 0 0 0 68 48 40 28 30 OAS 0 0 0 0 58 23 40 20 60 OAS 0 0 0 0 38 28 35 18 Polychaete. Results of polychaete toxicity tests and behavioral stud- ies are listed in Table 6.11. Not all the test organisms were retrieved from the experiments. These unretrieved animals, as well as dead and decomposing body sections, may represent mortalities that could not be verified without an in-hand dead specimen. Survival in all OAS-exposure concentrations was not significantly different from control survival. The highest mortality (25 percent at 96 hours) was measured in the 15 percent OAS treatment. Sublethal effects as determined by polychaete burrowing activity could not be determined for any of the treatments. Burrow openings and fecal pellets around openings were recorded, but artifacts of the previous day's activity could not be distinguished from the current day's. In general, activity increased in all treatments after 48 hours, then decreased through 96 hours below the initial level. Inspection of polychaetes after retrieval from experiments and before and during respiration measurements showed the 60 percent OAS-exposed organisms to be in poor condition, alive but motionless upon stimulation, and covered with mucus and attached sand grains and debris. The poly- chaetes from the control dishes, however, were robust, active, in good condition, and free of mucus and debris. TABLE 6.11 Results of polychaete toxicity tests and behavioral studies, Treatment (%) % Mortality 24-hr 48-hr 72-hr 96-hr % Survival 96-hr Control 5 OAS 15 OAS 30 OAS 60 OAS 0 3 5 10 3 5 5 8 3 10 10 10 5 5 8 8 10 17 17 23 85 80 75 92 77 145 Oxygen consumption. Differences in the metabolic functions of control and OAS-exposed populations of test organisms were determined by oxygen consumption measurements to assess sublethal, physiological responses to oil exposure. The following tests listed in Table 6.12 were conducted. All organisms were acclimated to 25°C for 15 minutes. Respiration chambers were filled with supersaturated, filtered seawater and held to a constant temperature (25°C) in a circulating water bath. A Beckman model 0260 oxygen analyzer (Og/T") was used, and changes in oxygen (pj^ 0^) within the respiration chamber were recorded every 5 minutes for the duration of the measurements. Organisms were wet weighed to the nearest 0.001 g. Oxygen consumption was calculated for each replicate in p£ Og per g per hr. TABLE 6.12 Laboratory design of whole animal respiration tests. Organism No. of Repl icates No. of Organisms/ Replicates Duration of Measurement Treatments Tested Mole Crab Surf Clam 3 3 3 3 30 min. 30 min. Control , 60% OAS Control , 60% OAS 60% OAS Result of oxygen consumption (p£ O2 per g per hr. ) measurements for all organisms taken from each OAS concentration after 96 hours of exposure are recorded in Table 6.13. The only measureable differences that were shown to be signficiant (p < 0.05) between the control and any oiled treat- ment were for the mole crab. There appeared to be a slight increase in oxygen uptake in the oiled versus the control treatments for the surf clam, but these differences were not significant. Oxygen consumption was slightly (nonsignificant) lower for the polychaetes treated with 60 percent OAS than for controls, which may possibly be a reflection of the poor physical condition of these worms as noted in the toxicity results section. It was not possible to determine the acute toxicity of IXTOC I oil (as oil accommodated seawater) in the beach biota studied, at least at the concentrations tested. The fauna examined appeared to show few, if any, acute effects from oil exposure. This could be related to the physical nature of the oil tested. However, the concentrations tested (1.25 to 15 ppm) in the lab should not be considered the same as the actual concen- trations observed in the Gulf of Mexico and on Texas beaches. 146 TABLE 6.13 Oxygen consumption for experimental animals removed from control and 60 percent OAS treatments after 96 hours of exposure. Data are reported in p £ O2 per g per hour. Treatment Organism Control 60% OAS Mole Crab* 20.14 18.24 24.88 18.47 26.95 15.32 X 23.99 17.34* Surf Clam 6.44 9.80 10.12 13.36 11.39 15.18 X 9.32 12.78 Polychaete 90.00 85.37 142.86 90.90 X 116.43 88.14 'Significant difference from controls at p < 0.05. Mortality was higher in the polycheates than in any other fauna tested (although this was by no means significant). This may be related to poly- chaetes being the only one of the three beach fauna tested that was a surface-deposit feeder. The other two were both suspension feeders. Feeding from the sediment surface, the polychaete may have ingested the numerous micro-tar balls that were initially suspended in the OAS and later settled to the sediment surface. This may help to explain the poor health of the worms in higher treatment concentrations as noted in the results. These acute tests did not evaluate any of the potential, sublethal, biological effects of oil exposure on reproductive success, long-term health of the organisms, accumulation of toxic substances, growth and development, and histopathological conditions that may result from chronic exposure to IXTOC I oil. What can be concluded from these acute tests was that the fauna examined appeared to show very few acute effects from oil exposure. 147 Effects Other Than Spilled Oil As results of laboratory toxicity studies and field studies have shown, there was some evidence for oil related impacts to sandy beach habitats from the IXTOC I oil spill. In addition to oil-induced impacts, other factors such as tropical storms and seasonality should also be con- sidered to properly interpret these data. Tropical Storms South Texas was hit by a tropical depression 31 August to 1 September 1979. The tropical depression raised tide levels, removing beached oil and pushing some of it up to the foredune line. However, the majority of the oil was dispersed back into nearshore waters. The beachface was also altered as the high winds and waves flattened it. In mid-September, a tropical storm resulting from Hurricane Frederick hit the south Texas coast. The storm surge was 1.2 m (4 ft) and winds reached to 60+ knots. The beachface was completely flattened. This was most noticeable at Big Shell where a 1.0 to 1.5 m berm normally found was flattened. The oil on the fine-grain sand beaches was removed or pushed up to the foredune ridge. The oil in the coarser mixed, sand shell beach at Big Shell Beach was worked into the sediment, as well as removed. It was not possible to determine what effect these storms had on the benthic infauna of the intertidal and nearshore subtidal zones. Thus, it was impossible to differentiate between impacts attributable to these two storms from those resulting from the IXTOC I oil spill. Seasonal ity Little is known about the seasonality of the beach infauna on south Texas barrier island gulf beaches. Loesch (1957) documented a seasonal decrease in Mustang Island Donax populations from August (peak) to September. Thus, in addition to impacts resulting from IXTOC I oil and tropical storms, seasonal variability in population densities must also be considered. STUDIES OF OFFSHORE AND NEARSHORE ENVIRONMENTS AND ORGANISMS Bioassay and toxicity tests of dominant and commercial species, in addition to observations made during cruises, comprise the results of offshore and nearshore environments and organisms. 148 Fisheries Toxicity studies and bioassay of three commercial fish species were carried out to investigate potential acute toxicity of IXTOC I oil. Seatrout Study This study investigated toxicity levels and sublethal, respiratory metabolic effects of IXTOC I crude oil on the spotted seatrout (Cynoscion nebulosus) , a sensitive, euryplastic species living in nearshore and estu- arine environments, which is used commercially and recreational ly (Wohlschlag and Wakeman, 1978; Wohlschlag and Parker, unpubl. data). The specific aims of these studies were to use the spotted seatrout as a test organism for making preliminary determinations of: 1. Acutely toxic levels of IXTOC I oil on adult and fingerlings or underyearl ings, 2. Metabolic results at active and standard (or resting) levels for detection of physiological scope diminution even though the chemical composition of the spill material could be considered unknown, 3. What levels of the spill material produce observable metabolic depression, and 4. Information of basic energetics data on a species of general importance in fishery and ecological considerations. Spotted seatrout used throughout the study were captured near Port Aransas, Texas, by hook-and-1 ine or seine. Capture temperature (30°C) and salinity (32 /oo) were near test levels for respiration experiments, but toxicity test fish required additional acclimation to the lower (23°C) room temperature used. Fish were transported to the laboratory in insulated boxes and placed in indoor holding tanks for acclimation to the appropriate test condition. Fish that behaved abnormally or appeared unhealthy were discarded. Samples of wellhead IXTOC I mousse were collected by the U.S. Coast Guard Cutter POINT BAKER. The preparation of oil spill material to produce a stock, "100 percent solution" in toxicity tests were done as follows: "mousse" collected by the U.S. Coast Guard Cutter POINT BAKER was blended with seawater from laboratory settling tanks with a salinity of 35 /oo. No measured amounts of "mousse" were used; the procedure involved high-speed blending of the oil in water for 45 sec, after which the oil accommodated seawater (OAS) fraction was siphoned into a holding container. After enough of this solution was collected, it was diluted with two parts seawater to produce a 100 percent stock solution. Initially, the concentration of the stock was 27 mg/£ oil for the adult fish toxicity tests and 30.1 mg/£ for the fingerlings and underyearl ings. Before the start and end of each test, samples of each appropriate dilution were taken for later chemical analysis. 149 Preliminary toxicity tests on adult C. nebulosus were conducted in 20-gallon, glass aquaria equipped with aerators. Six OAS dilutions were used (100, 50, 12, 12.5, 5, and 1 percent); control fish were maintained in a larger holding tank. Observations were recorded for 96 hours on each of these six tanks, each containing two fish of 100 to 200 g weight. All tests were conducted at room temperature (23°C) and a salinity of 35 /oo. Fingerlings and underyearl ing fish tests were carried out in six 20-gallon aquaria at five dilutions (100, 50, 25, 12.5, and 5 percent) and one, oil-free control tank. Again, observations on behavior and toxicity were recorded for 96 hours. At the end of all experiments, fish were weighed and lengths measured. Specimens were then frozen for later inspec- tion. Respiration experiments were conducted at 28°C and 35 /oo. Fish were exposed to each OAS dilution in a temperature-controlled, circular tank for 48 hours before respiration measurements were made. Fish were starved during this period and a slow current was maintained within the circular tank to provide a stimulus for swimming so that active metabolism measure- ments could be made. The holding tank and respirometer tank were always well-aerated throughout experiments. Active and resting metabolism rates were made in a 207-Blazka chamber (Blazka et al., 1960; Fry, 1971) as used by Wohlschlag and Wakeman (1978). No filtration system was used for these tests. Fish were maintained for 2 days swimming at low velocities (about one length (L/sec) before active measurements began. After swimming in the chamber at an intermediate speed for enough time to calm the fish, the velocity was increased gradually until the fish "broke" pace. At this instant, the velocity was lowered (usually quite slightly) to the highest possible velocity at which normal swimming persisted without breaking. With this "training" regimen, the maximum-sustained velocity could be reproducible for each fish. The U (total lengths/sec) swimming velocity was determined, after which each fish was tested for at least 1 hour for a consistent U . Following the 1 hour or longer runs, the fish were left in the chamber at intermediate and/or zero velocities, and oxygen measurements were made to detect any respiratory irregularities that could have resulted had the U been associated with may undesirable anaerobic metabolism. Oxygen consumption rates were measured by withdrawal of small samples for use in a Radiometer (Model E-5046) with a PHM 71 electrode equipped with acid-base analyzer. Following completion of a set of experimental, oxygen consumption measurements, the fish were removed and lengths and weights recorded. Along with lengths, weights, oxygen consumption rates, and swimming velocities (total lengths/sec), salinities were recorded to 0.1 /oo and temperatures to 0.1°C. From this, a simple multiple regression was calculated at control and experimental conditions in the form ^ = a + bX +bX WW V V 150 where Y = expected Og consumption rate in log ^q mg02 1 hr a - constant X = log^o weight in grams W X = L/sec The various "b" values are the respective, partial regression coefficients. Similar procedures have been used by Wohlschlag and Juliano (1959), Wohlschlag and Cameron (1967), and others. Temperature and salinity values remained near 28°C and 35 /oo, respec- tively, and were not included in the regression calculations. Control data were acquired from a study on ocean-dumped, pharmaceutical wastes by Wohlschlag and Parker (in progress). Standard metabolic rates were deter- mined from the appropriate, active regression equation using the Brett (1964) technique. This involves a line parallel to the active regression line through the lowest U value and using the "Y" intercept value as a realistic estimate of the standard rate. The preliminary experiment to assess the toxicity of OAS to subadult fish in 20-gallon aquaria indicated that 100, 50, and 25 percent dilutions had a significant effect on behavior after 96 hours of exposure. At dilu- tions of 12.5, 5, and 1 percent, adverse effects usually appeared after 24 hours of oil exposure. The second, preliminary experiment to assess 96-hour toxicity to fingerlings had similar, but more lethal, results. From these preliminary data, a 96-hour TLM level would be a range from 5 to 25 percent dilution (1.3 to 7.5 mg/£). The smallest of the fish generally died first; this would indicate a critically susceptible size of smaller than about 10 g, although there may have been uncontrolled variables from one aquarium to the next. The first experimental Blazka respiratory measurement attempts failed during acclimation (habituation) to a 5 percent OAS level, when some deaths occurred. Accordingly, the remainder of the results deal with respiratory metabolism measured under control or 1 percent OAS conditions in the Blazka apparatus. The more definitive results from the Blazka chamber experiments yielded for control data: ^ = 0.06995 + 0.71242 X,, + 0.11192 X,, (Equation 1), where the average t was 1 14 g, and the < lengths/sec. Total N = 34, w V weight was 114 g, and the average of 14 determinations at U was 3.3 ^ ^ max 151 The data at 1 percent OAS were ^ = 0.87662 -H 0.36468 Xw "" ^'^^^^^ \ (Equation 2), where average it was 164 g, a sec. Total N = 27. weight was 164 g, and average of 10, U measurements was 2.8 lengths/ m3x The following schedule of statistics for these equations are also useful (Table 6.14). TABLE 6.14 Statistical parameters used in calculations of regressions. N = sample size; R = correlation coefficient Equation N R Sw s. P s. P No. w V 1 34 0.92 0.07901 0.12416 0.001 0.0092 <0.001 2 27 0.77 0.13624 0.02123 0.001 0.0190 <0.001 Figure 6.10 is the plot of oxygen consumption rate of all control fish (calculated from Equation 1 and adjusted to the average weight of 114 g) against observed swimming velocities. This equation is ^ = 1.52522 + 0.11192 X V The Brett (1964) extrapolated standard metabolism rate was 29.17 mg Og/hr or 256 mg 0„/kg/hr. Figure 6.11 is the plot of the oxygen consumption of the experimental fish (calculated from Equation 2 and adjusted to the average weight of 164 g) against observed swimming rates. This equation is ^ = 1.68433 +0.11381 X v Some pertinent notes on the condition of the fish in the Blazka chamber experiments are most revealing. Fish in the 1 percent solution showed no deterioration for the first 2 days of the acclimation and first 2 days of oil exposure. By the third day of oil exposure, fish in the Blazka chamber were more labored in their swimming motions and appeared to have equilibrium problems. Fish were definitely sluggish on the fourth day of oil exposure with an obvious prevalence of tail rot. Of the three fish remaining on day 152 ► l-^ O 6uj D0| CM o 00 (0 -* C\J c CVJ 1 1 o o - CVJ CO o o -P ^~v x: X CD IT5 • r— E 0) 3 ? V — ' OJ ■a en 0) fO c S- •r— a» fO > +-> ro to 3 Ol O) if) ■♦-> (0 '^f E 5- r^ 3 ■" E -D •r- S- -t-> X (0 to (0 -o E C -p (13 3 S- +J O O I/) ;- 4- +j ■o nj 0) (U 0) S- ^J I/) fTJ (TJ E ^— (/) -1- ^^ o -P -P S- C I/) ■t-) ..- Q) o c O 0 o Q. irt (0 u (X) ■o -P _| S- Q) (D o 1— U ^ 4- U -r- s- -o > l/> •I- c K 4-> U -1- c O LU to •r- o X _I c o . (0 I/) UJ - > -p ■p Q. (0 c E s- o 3 i/) CT ^~^ c c 4- o •r— Sw** u E E ? c •r- O (U 5 s- 05 (O s- >, < X ■a o 0) > . ■a U (/) (U 0) (U ■»-> irt u (0 ^ c (^ O (0 ZJ E u +J s- ^— 1/) o (TJ c >♦- C_) (TJ a* O to ■" a> ■o c U3 -P E l.- M O Blu -p (0 -p u fO s- -p X 3 (U E +J (0 (0 E -D S- S- (0 0 -o 14- C 01 +J r- S- to •I- ro O -D in Qi 0) -P +J T3 C (13 ■P T3 to — to U U OJ J- J- -p 0) -r- n3 D. U U C -r- t— uj -a c C 'r- •I — « -P (U •<- D .p X O fO (0 s- >- c c •I- O s- E O •!- 4- 3 I/) to Q> -a -P cu n3 > c to O JH •f- o -p a.-p E to 3 C s- < to CD u c n3 E (0 s_ C7) O U (0 M- S- c -a 0) Ol >,-P D5 X o c O .— -t- Q. E ■D E 0) +J .^ ^J ^ ? fO D5 to U 5 X >— /(O to Q) E O CT)^ (0 ^-' S- i-l 0) "O tH > Ol . fO c to •.- Dl (0 (U -P S- «:1- to 3 to 3 CTr— irt 154 five, one died; one failed to swim faster than 1.6 lengths/sec and was afflicted with tail rot, gill lesions, and coughing spasms; while the last fish swam weakly at only 1.5 lengths/sec. During the 7 days, there was no perceptible deterioration with U values showing no trend downward. ^ ^ max ^ The initial trials that indicated a 1 percent OAS concentration was significantly toxic were apparently misleading, inasmuch as cumulative effects did not become evident until after 4 days. Just what protocol should be used for evaluating delayed reactions to unknown toxins at un- known concentration is unclear because relative concentrations, exposure time, and effects in the open ocean are unknown. McKeown and March (1978) have observed severe damage to gills in rainbow trout (Salmo gairdneri ) exposed to Bunker C oil. Minchew and Yarbrough (1977) found fin erosion in Mugi 1 cephalus exposed to 4 to 5 mg/£ crude oil in estuarine pond ecosystems. Sinderman (1978) reviewed the recent literature on the generalized nature of fin rot occurrences in degraded estuarine and coastal systems. The coughing response has been shown to be directly related to concentrations of toxic substances (Barnett and Toews, 1978; Carlson and Drummond, 1978; and others). Any of these, or other similar deficiencies, would be expected to suppress metabolic scope. From the descriptions of the preliminary, toxicity tests and the Blazka chamber respiratory experiments, there was no obvious, biological clue about a sufficient concentration or a proper exposure interval. Whatever the identifications of toxic materials are, it was apparent that a 5 percent extract was acutely toxic within 2 days. In about 7 days, the 1 percent dilution may be considered acutely toxic. Whether the acute toxicity depends upon bioaccumulation past a threshold concentration, or upon the progressive breakdown of a biochemical system once a toxin, or combination of toxins, initiates a degradational process, should provide a focal point of interest in future experiments. Such experiments should provide contrasting acute and sublethal chronic toxicity levels wih the sublethal levels low enough to: (1) allow for flow-through experiments conducted at a continuously added, constant pollutant level, and (2) detect further degradation, if any, by a single initial addition of the pollutant. The experimental concentration of the pollutants in this study yielded what might be ordinarily expected of sublethal levels. The Blazka respir- ometer experiments, as summarized by Equations 1 and 2 and the plotted, processed data in Figures 6.10 and 6.11, show that the variability of the controls is considerably less with high "R" multiple correlation and low standard error of the regression, s . The greater variability of the plotted data for oil exposed fish in Figure 6.11 shows up at X =0 and at the maximum-sustained (encircled) values when compared with Figure 6.10 for 155 control data. The greater variability of standard error (s. ) for the b w of the control (0.12 compared with 0.02) was unclear, although similar ranges of standard errors are common and may be associated with the relatively smaller average size, X = 114 g, and the smaller range of weights for the control fish. Average weights of 114 g for controls in Equation 1 and 164 g for 1 percent IXTOC I samples in Equation 2 reveal somewhat emphatically the differences between control and experimental metabolic levels when the average maximum activity is decreased from 3.3 lengths/sec to 2.8 lengths /sec, or to 85 percent of the maximum-sustained value. At 114 g, Equation 1 yields 704 mg/0^ kg/h at maximum activity, Xv = 3.3 lengths/sec. From Figure 6.10, extrapolated from the minimum, active level of this zero (standard) level by the Brett (1964) method, the standard rate is 256 mg 0„/kg /h. The difference, or scope, was 448 mg O^/kg/h (704 to 256). At 164 g. Equation 2 (1 percent IXTOC I) yields at X =2.8 lengths/sec, 614 mg O^/kg/h, which was considerably depressed. A corresponding Brett type of extrapolation yielded a standard rate of 214 mg O^/kg/h, somewhat lower than the control as might be expected for continuously stressed fish. The difference from 614 to 214 of 400 m about 89 percent of the control values. The difference from 614 to 214 of 400 mg O^/kg/h was a scope which was The depression in the b coefficient in Equation 2 (0.36 compared with 0.71) in Equation 1 indicates that polluted waters adversely and selectively affects the larger fish. This has been repeatedly observed both in current studies by Wohlschlag and Cameron (1967), Kloth and Wohlschlag (1972), and others. For this study, an extrapolation from Equations 1 and 2 to a larger size, say 500 g, was instructive. For control fish, the scope is (460 to 167) = 293 mg 0 /kg/h with X^ = 500 g and X^ = 2.8 lengths/sec. Thus for a 500 g fish, the oil-exposed fish have a scope value that was about 67 percent of the control fish. Clearly, the implications are that even these low concentrations of chemical toxicants in the 1 percent solution of the mousse-water phase can have a severe effect on the overall metabolism of organisms. In fisheries, the disappearance of larger members with exploitive stresses is well known, but little work has been extended to show if natural or pollution stresses 156 at very low, sublethal levels can have the same utlimate effect (i.e., the older and larger members tend to disappear from a population structure while the younger and smaller members survive), providing some recruitment is maintained. Redfish Study The redfish (Sciaenops ocel lata) is one of the most important commer- cial and sport fishes in Texas waters. Redfish generally spawn around the mouths of tidal inlets on the Texas coast in the late summer and early fall. Oil from IXTOC I blowout was in Texas waters, not only while adult redfish were spawning, but also while the early larval stages were develop- ing. This study was to determine the effect of IXTOC I oil on redfish eggs and larvae, which are very sensitive and susceptible stages to deleterious perturbations in the life cycle. To determine the toxicity of IXTOC I crude oil on the eggs and newly hatched larvae of the redfish, three different tests were conducted using three forms of IXTOC I crude oil. In all cases, the eggs and larvae were obtained from captive redfish which were induced to spawn, using light and temperature manipulation to simulate natural conditions. All tests were performed in 32 /oo seawater, maintained at 26°C. In the first of these tests, a 1 percent concentration (25 to 30 ppm) of oil accommodated seawater (OAS) was used. This solution was prepared by agitating IXTOC I crude oil and filtered seawater for 2 hours and then allowing it to settle for 2 hours. The water, which was relatively free of large oil globules, at the bottom of the container was decanted off and used as OAS. Concentrations of 0 (control) to 100 percent seawater/OAS were prepared. Fifty, one-day-old redfish eggs were placed in each of the 11 different concentrations and allowed to stand without aeration. After 24 hours, the emerging larvae were counted. The second experiment was conducted in the same manner as the first with the following modifications. The OAS was filtered using a 0.45p Millipore filter, and the water-soluble fraction (WSF) was retained. Twenty-five, 1-day-old redfish eggs from a different spawn were used in Experiments 1 and 3. These were placed in mixtures of 0 (control) and 50 to 100 percent WSF and filtered seawater. The number of live and dead larvae and unhatched eggs were recorded. In the third experiment, 500, 16-hour-old redfish eggs were placed in 1 £ of unfiltered seawater to which 4 g of IXTOC I mousse had been added. The mixture was maintained with gentle aeration. Another mixture of 9 g of mousse to 1 £ of water was prepared, aerated vigorously, and maintained at room temperature. Five hundred, 1-hour-old redfish eggs were added, and the number of live larvae were counted after 24 hours. Live and dead larvae were counted in the 4 g/£ preparation, while only live larvae were counted in the 9 g/£ preparation. Experiments using mousse were repeated 1 week later, using eggs 14 hours old, but modified in that after 24 hours, 157 the total number of live larvae, live deformed larvae (body bent dorsal ly and/or a large unabsorbed yolk sac), dead larvae, and unhatched eggs were counted. Only live larvae were counted in Experiment 1 (Table 6.15). It was therefore impossible to ascertain the effect of the OAS on redfish eggs. Hatch percentage of nearly 100 percent was observed in other eggs from this same spawn. This, along with the short time (<1 hour) the eggs were sub- jected to the OAS before hatching, indicates that the 38 percent mortality in the control (0 percent) was an expression of normal mortality in 24-hour- old redfish held in this manner. Forty-eight to 52 percent mortality above control mortality was observed between 50 and 100 percent OAS/seawater mixture. Live and dead larvae were used in Experiment 2 (Table 6.16). No dead larvae were found in the control or 50 percent WSF; 64 to 94 percent mortality was experienced between 60 and 100 percent WSF. A large percentage (80 percent) of the 127 live larvae treated with 4 g of IXTOC I mousse in Experiment 3 were either deformed, unresponsive to tactile stimuli, or moved very slowly. There were a large number (250) of dead larvae that were highly deformed. Many of the larvae were brown and retained a large yolk sac, indicating that death occurred very shortly after hatching. After 24 hours, only five live larvae were found in the 9 g mousse/water mixture. Many of the unhatched eggs were observed floating in mousse that had accumulated at the water surface. TABLE 6.15 Survival of redfish larvae after 24 hours in OAS (oil accom- modated seawater). OAS Live Larvae (%) (No.) 0 (Contrc • 1) 31 10 26 20 17 30 13 40 13 50 7 60 9 70 8 80 7 90 5 100 5 Mortality 38 48 66 74 74 86 82 84 86 90 90 158 TABLE 6.16 Survival of redfish eggs and larvae after 24 hours in WSF (water-soluble fraction). WSF Live Larvae Dead Larvae Unhatched Mortality (%) (No.) (No.) Eggs (%) 0 (Control) 16 0 7 0 50 22 0 3 0 60 17 2 4 11 70 6 16 2 73 80 8 14 2 64 90 6 19 0 76 100 2 19 0 94 In the repeat of the mousse experiment using 14-hour-old eggs, the total number of eggs and larvae observed after 24 hours was lowest in the highest oil concentration (Table 6.17). This was probably due in part to the unhatched eggs being entrapped in the mousse and were thus not counted. Mortality was highest in the 9 g treatment where 96 percent of the larvae accounted for were dead or live deformed; 89 percent of the larvae accounted for in the 4 g treatment were dead or live deformed. After 48 hours, all larvae in the oiled beakers were dead, while living fish were still observed in controls. TABLE 6.17 Survival of redfish eggs and larvae after 24 hours in two IXTOC I crude oil mousse/seawater mixtures. Mousse/1 £ Live Unhatched seawater Live Deformed Dead Eggs (g) (No.) (%) (No.) (%) (No.) (%) (No.) (%) Total 0 (Control) 298 (67) 4 32 (7) 9 3 (1) 17 (4) 115 (26) 15 (3) 445 394 (85) 18 (4) 20 (4) 464 89 (28) 214 (68) 8 (3) 314 The water-soluble fraction (WSF) of IXTOC I crude oil was more acutely toxic than the oil accommodated seawater (OAS) fraction, since higher mortality was observed at a lower concentration in the WSF than in the OAS. The mousse mixture of 9 g/£ water was more toxic than a mousse mixture of 4 g/j^ water. The large number of deformed larvae in the lower concentra- tion of mousse indicated that possibly even this mixture would chronically cause 100 percent mortality after an extended period of exposure. 159 Brown Shrimp Study The brown shrimp (Penaeus aztecus) is a commercially important species, making up a large portion of the shrimp fisheries along the Texas coast. Adult shrimp migrate out of lagoons and estuaries into offshore coastal waters to spawn. Ocean currents brought IXTOC I oil into Texas coastal waters during this period of migration, and impact to the Texas shrimp fisheries was feared. The purpose of this study was to investigate the effects of IXTOC I oil on adult brown shrimp in laboratory bioassays in an attempt to predict potential impacts to the brown shrimp fisheries. Toxicity tests and burrowing behavior. Four groups (replicates) of shrimp, consisting of eight animals per group, were exposed to four different treatment concentrations consisting of 5, 15, 30, and 60 percent oil-accom- modated seawater (OAS) fractions of IXTOC I oil. An additional group was maintained in oil -free seawater as a control. These animals were placed in aquaria containing approximately 4 cm of sediment in 14.5 S, of 27 /oo aerated seawater. Animals were not fed. the tanks were sealed with black, polyurethane plastic to simulate darkness. Each tank was censused at the end of each 24 hours, for a 96-hour period. Dead shrimp were recorded and removed from the tanks. Shrimp behavioral activity was monitored daily by subjecting each tank to sunlight for 30 minutes to stimulate burrowing activity and recording the number of burrows. Initial observations indicated best results were obtained by limiting exposure to sunlight to 5 minutes, due to problems of reburrowing during the 30-minute period. Thus, the period of sunlight exposure was reduced to 5 minutes. After 96 hours of oil exposure, tests were ended. Percent mortality for the shrimp at the various treatment levels are listed in Table 6.18. All test animals were retrieved from the experiments. There was no significant difference in mortality observed between controls and oil-exposed shrimps. The highest mortalities (9 percent at 24 to 96 hours) occurred in the highest exposure concentration (60 percent OAS). TABLE 6.18 Mortality observed in adult shrimp exposed to four different OAS* concentrations for 96 hours. Treatment % Mortal ity ^_ (% OAS) 24-hr 48-hr 72-hr 96-hr Control 3 6 6 6 5 3 3 3 3 15 0 0 0 0 30 3 3 3 3 60 9 9 9 9 *oi 1 -accommodated seawater 160 After 96 hours of oil exposure, shrimp were exposed to light for 5 minutes and percent burrowing was recorded as listed in Table 6.19. There was no significant difference in burrowing behavior observed between controls and experimental shrimp, after 96 hours of oil exposure. In oil-exposed shrimp, approximately 50 percent of those above the sediment would burrow within the 5 minute exposure to light. Then the number of burrowed shrimp was highest in the 30 to 60 percent GAS treatments, both before (71 percent) and after (93 percent) exposure to light (5 minutes). Oxygen consumption. Differences in metabolic function of control and oil -exposed populations of adult brown shrimp were determined by measuring whole animal oxygen consumption. The following tests were run as indicated in Table 6.20. All organisms were acclimated to 25°C for 15 minutes. Respiration chambers were filled with supersaturated. TABLE 6.19 Burrowing activity observed in control and 96-hour oil-exposed shrimp before, during, and at the end of 5 minutes of exposure to sun- light. Treatment % Burrowed % Burrowing % B( jrrowing at (% OAS) Ir litially w/ in 5 min. end of 5 min. Control 41 42 75 5 31 59 59 15 47 59 69 30 77 43 90 60 71 50 93 TABLE 6.20 Laboratory design of brown shrimp respiration experiments. No. of Shrimp No. of Organisms/ Repl icate Duration of Measurement Treatment Tested 1 20 min. Control , 15 & 60% OAS filtered seawater and held to a constant temperature (25°C) in a circulating water bath. A Beckman model 0260 oxygen analyzer (02/T°) was used, and changes in oxygen (pjH O/g/g/hr) within the respiration chamber were recorded 161 every 5 minutes for the duration of measurements. Organisms were weighed wet to the nearest 0.001 g. Oxygen consumption was calculated for each replicate in p£ Og/g/hr, and are recorded in Table 6.21. There were no significant (p < 0.05) differences measured between controls and any oil- exposed shrimp. There appeared to be a slight increase in oxygen uptake in the oiled compared with control shrimp, but these differences were not significant. TABLE 6.21 Whole animal respiration rates ([j£ 02/g/hr) in adult Brown Shrimp acutely exposed to IXTOC I oil for 96 hours. Oil Exposure Concentration Whole Anima 1 Re: SP" i rati on (p£ O9 /g/hr) Mean S/N N Statistical Significance* P value* Control 15% OAS 60% OAS Mann- 1.34 0.16 1.61 0.15 1.45 0.12 -Whitney U-test 3 3 3 NS NS 0.40 0.70 ^determined by Marine Mammals Little information is available concerning the distribution and natural history of marine mammals in the Gulf of Mexico. Davis (1974) describes 18 species of marine mammals that have been sighted in the Texas coastal waters. The only common nearshore resident is the bottled-nosed dolphin (Tursiops truncatus) which inhabits the inlets and the gulf near the inlets. The spotted dolphin (Stenella altenuata) is a pelagic species found farther offshore. Porpoises were observed swimming in oil during two of the cruises. On Cruise FSU-l (Florida State University) in July 1979, porpoises were seen riding the ship's wake as it went through tar ball fields and windrows. During the R/V WESTERN GULF cruise (22-23 August 1979), porpoises were observed surfacing in oil sheen and, in one case, in mousse-coverd water. No marine mammal mortalities were observed during the spill. 162 Marine Turtles Five species of marine turtles have been reported along the Texas coast. The most commonly observed marine turtle is the Atlantic loggerhead (Caretta caretta). The other common species observed along the south Texas coast is the Kemp's ridley (Lepidochelys kempi ). This endangered species, at one time, used Padre Island sand beaches as egg-laying areas. In a joint effort with Mexico, the NMFS and National Park Service are trying to reestablish Padre Island as a nesting area for the Kemp's ridley. Two Atlantic green turtle (Chelonia my das) carcasses were recovered from the foreshore, approximately 32 to 33 miles (51 to 53 km) south of Malaquite Beach. The partially decomposed carcasses were covered with oil. They were frozen and delivered to the U.S. Fish and Wildlife Service. A dead Kemp's ridley turtle was also turned in to the U.S. Fish and Wildlife Service. The carcasses were sent to the Patuxent Research Center for autopsy. Preliminary autopsies indicated there was no apparent cause of death other than oil contamination. There was little evidence of oil ingestion. The results of tissue analyses will better define these findings, Zooplankton and Benthic Amphipods During the impact of the Texas coast by IXTOC I oil, much concern was focused on potential effects of pelagic zooplankton and benthic infaunal invertebrates. Impacts to zooplankton were expected from floating oil slicks and sheens, while impacts to benthic invertebrates were expected from sinking oil and tar balls. Two series of experiments were carried out on the acute toxicity of oil accommodated in seawater (OAS) made from the spilled IXTOC I oil. In one experiment, mixed natural zooplankton were exposed to OAS for 96 hours. A vital staining method was employed to distinguish dead from living indi- viduals. In another experiment, a benthic amphipod, Parhyale hawaiensis (Dana), was acutely exposed to OAS. Results from these tests were used to predict potential impacts to zooplankton and benthic infauna. Juvenile amphipods (one month old) used in the toxicity tests were obtained from stock cultures maintained at the Port Aransas Marine Labora- tory of the University of Texas since 1976. They were kept in seawater (30 percent) filtered by glass fiber fish flake. Following the acclimation period, juvenile amphipods were exposed to the following OAS dilutions of 50, 40, 30, 20, 10, and 1 percent. Forty individuals were divided into two equal replicate groups and placed in 200 ml of each OAS dilution. An additional group of juvenile amphipods were similarly divided and maintained in oil-free seawater as a control. Mortality was observed for 7 days. Test medium was gently bubbled with air and not renewed during the experi- mental period. 163 Zooplankton were collected at the Port Aransas Marine Laboratory pier and acclimated in seawater of 30 /oo, at a room temperature of 24°C for 2 days, before the experiments began. Zooplankton were fed with a mixture of algae comprised of Dunal iel la tertiolecta and Isochrysis galbana during both acclimation and exposure periods. Following acclimation, replicate samples of zooplankton were exposed to five OAS concentrations of 40, 30, 20, 10, and 1 percent. An additional group of zooplankton were maintained in oil-free seawater as a control. At the end of 96 hours of exposure, 10 m£ of neutral red were added to each jar which contained 1 £ of test medium, and the zooplankton were then prepared following the procedures suggested by Crippen and Perrier (1974). To obtain percentage of survival for each sample, subsamples of at least 300 individuals were counted, identified, and determined for their status of living and dead animals. OAS stock solutions used in all toxicity tests were prepared in the following manner. Oil was layered on the top of filtered seawater in a 4 £ aspirator bottle with a tube outlet near the bottom and shaken on an Eberback Shaker at low speed (260 excursions/min) for 2 hours. The lower portion OAS was drained after a 2 hour settling period and used as a stock OAS. The chemical composition and the total amount of oil suspended and dis- solved in seawater were analyzed at the time the experiment began. The prepared OAS stock contained 27 mg/S, of oil. Therefore, a 50 percent dilution would contain approximately 14 mg/£ of oil. All experiments were maintained under the conditions of room tempera- ture of 24°C (±2°C), and at salinity of 30 °/oo. Animals were also fed daily during all experiments. At all test concentrations, ranging from 1 to 50 percent OAS, all individuals survived 7 days of exposure, except that two amphipods died at day seven in 40 percent OAS (Table 6.22). Additionally, there was no mortality observed in controls. Amphipods were actively moving and had no signs of abnormal behavior when compared with controls. TABLE 6.22 Average percent survival of Parhyale hawaiensis in oil accommodated seawater (OAS). -9^ Exposure Time 0 Control OIL CONCENTRATION OF OAS (hours 1% 10% 20% 30% 40% 50% 24 100 100 100 100 100 100 100 48 100 100 100 100 100 100 100 72 100 100 100 100 TOO 100 100 96 100 100 100 100 100 100 100 120 100 100 100 100 100 100 100 144 100 100 100 100 100 100 100 168 100 100 100 100 100 95 100 164 Zooplankton used in the toxicity study were typically a natural endemic to Texas coastal waters during the summer. The calanoid copepod, Acartia tonsa, comprised 65 percent of the test population. Other copepods that made up the remaining four most abundant species were Paracalanus crassi rostris (26.3 percent), Oithona colcarva (6.6 percent), Corycaeus amazonicus (0.6 per- cent), and Eucalanus monachus (0.5 percent). These four species together with A. tonsa comprised more than 99 percent of test zooplankton populations. Survival of copepods at all test concentrations were high, being >75 percent (Table 6.23). No significant trend in mortality was correlated to the concentration of OAS tested. Highest mortalities of copepods were recorded in sample 1 of both controls and 1 percent OAS. The reasons for this were not apparent, but judging from the mortality at the higher concen- trations of OAS, it may be related to some effect caused by some unknown artificial factors rather than the toxicity of oil. TABLE 6.23 Average percent survival of coastal zooplankton in oil accommodated seawater. Control OIL CONCENTRATION 1% 10% 20% 30% 40% 65 82 91 96 80 88 83 81 76 83 76.5 82.5 86 86 81.5 76.5 82.5 86 86 81.5 6.6 0.3 2.9 5.8 0.9 3 3 3 3 3 Sample 1 Sample 2 Sample 3 47 87 67 Mean 67 s/t^ 11.6 N 3 These two studies indicated that the OAS of the spilled IXTOC I oil was not acutely toxic to the two kinds of crustaceans tested, possibly because this oil has been weathered for a long time. Thus, the most toxic components such as benzenes and napthalenes may have already evaporated to the extent that the residual components were no longer acutely toxic to these two marine invertebrates (amphipods and copepods). Previous studies (Lee et al., 1978) have indicated that weathered oil was much less toxic than fresh oi 1 . Chemical analysis of the test oil also showed that only a small amount of oil was dissolved into seawater and this total water soluble fraction was less than 3 mg/£ (K. Winters, pers. comm.). The water soluble fractions of a few oils have been characterized. Anderson et al . (1974) reported 23.75 ppm for south Louisiana crude oil, 21.65 ppm for Kuwait crude oil, and 5.28 ppm for a No. 2 fuel oil. Winters et al. (1976) have quantified 165 another four EXXON fuel oils, including 16 ppm for Montana, 19 ppm for Baytown, 14 ppm for New Jersey, and 9 ppm for Baton Rouge. In general, the toxicity of either oil in seawater or water soluble fractions was positively related to the concentrations of aromatics such as benzenes and naphtalenes, generally found in the water soluble fractions (Anderson et al . , 1974; Byrne and Calder, 1977) and the total amount of organics present in seawater (Lee, unpubl. data). Thus, the toxicity varies from one oil to another depending upon concentrations and toxic properties of the aromatic fractions of the particular oil. Toxicity also varied among animals. For example, the 96-hr-LC5o of a No. 2 fuel oil was about 3.0 ppm (OAS) and 3.5 ppm (WSF) for the grass shrimp, Palaemonetes pugio. Under the same test conditions, the 96-hr-LC5o for the post larvae of the brown shrimp, Penaeus aztecus, was 9.4 ppm (OAS) and 4.9 ppm (WSF), respectively (Anderson et al . , 1974). For the two taxa (copepods and amphipods) tested in this present study, estimated values of 96-hr-LC5o were above the concentrations tested (13.5 mg/£). Obviously this weathered IXTOC I oil was far less toxic'than either south Louisiana crude or certain No. 2 fuel oils. SUMMARY OF BIOLOGICAL STUDIES Inlets and Lagoons The only significant oil impact observed to inlets or lagoons was on 28-29 August 1979, when approximately 12 metric tons (86 barrels) of IXTOC I mousse impacted approximately 900 m of fringing marsh that bordered Lydia Anne Channel inside the Aransas Pass. Measurable effects upon animals were minimal as were effects to lightly oiled marsh grasses. Moderately oiled marsh grasses exhibited stress symptoms, but plant growth continued. Small, scattered areas of heavy oiling resulted in dead or dying marsh vegetation. Tides and wave action had dispersed much of the oil from these areas by 11 September 1979. Physiological bioassays with IXTOC I oil (in the form of mousse) did not immediately inhibit photosynthesis or respiration of representative nearshore plankton samples and seagrasses. Sand Beaches Aerial counts of wading and shorebirds indicated fewer birds were present during the period of heaviest oiling. Following heavy seas due to a tropical depression (31 August to 1 September 1979), an influx of birds occurred. A mid-September tropical storm that resulted from Hurricane Frederic removed much of the oil from the beaches, and the number of birds using the beach areas increased dramatically. 166 Ground surveys of oiled beaches revealed the following. Wading and shorebirds responded directly to oil concentrations on the beach in four ways: (1) birds avoided heavily oiled beaches; (2) birds avoided more heavily oiled parts of the beach, being more common on the back beach rather than the foreshore during periods of heaviest oil; (3) oiled birds spent less time feeding and more time resting; and (4) the entire bird population showed a decrease in size. This was interpreted as abandonment of sand beaches, because following the storm's removal of oil from beaches, bird populations returned to former numbers and reinvaded previously oiled foreshores. Ground observations of wading and shorebirds indicated that the oiled birds never exceeded 10 percent, peaking during periods of heaviest beach oiling. Eighty- two (82) birds were more than 75 percent oiled; these were judged as unlikely to survive. Few dead birds were found; however, removal by predators may have accounted for this. Physiological bioassays of birds related to the endangered peregrine falcon and whooping crane showed reduced fitness (lethargy, weight loss, and increased mortality), although the toxicity of IXTOC I oil to these species was judged low when compared with other crude oils. Site-specific studies of the infaunal communities at sand beaches before and after oiling indicated that the subtidal zone experienced a significant change in population size following oiling. Densities of subtidal crustaceans (mostly mole crabs and amphipods) were greatly reduced. Changes in other subtidal infauna were more variable, although the trend was toward reduced numbers, especially at the second trough and bar. The intertidal infauna did not show an overall population decrease, however. Intertidal crustaceans populations were significantly reduced as was infaunal community diversity. Ghost crabs avoided oil on the lower beach by migrating farther up the beach in some cases; however, at one moderately oiled transect, no significant change in distribution was measured. The response of wrack-associated amphipods was also variable, although they disappeared at five of six transects following oiling. Laboratory bioassays with IXTOC I oil (in the form of mousse) had minimal effects on mole crabs, surf clams, or polychaetes in acute exposures. This may support results of field studies that indicate a limited impact to infauna. Effects Other Than Oil Population decreases may have been affected by a tropical storm that hit the Texas coast in September 1979. The beach was reworked back to the foredune ridge. The berm crest was flattened. Seasonality may have also had an effect on the decrease in population. Peak summer populations would be decreasing during September. This was documented for Donax sp. (Loesch, 1957) and may also hold true for other beach fauna. 167 Offshore and Nearshore Environments Toxicity studies and bioassays were conducted on three commercially important species. The spotted seatrout was sensitive even to low levels of oil contamination. Symptoms, such as equilibrium problems, sluggishness, tail rot, and coughing spasms, were observed in tests using 1 percent OAS. Redfish eggs and larvae were tested in OAS, WSF, and two different mousse/seawater fractions. WSF was more acutely toxic than the OAS or mousse/seawater fractions. Of concentratons >50 percent WSF, mortality of larvae increased rapidly from 11 percent dead (60 percent WSF) to 94 percent dead (100 percent WSF). OAS, WSF, and mousse/seawater fractions were deleterious to redfish larvae and eggs. Brown shrimp were more resi stent to the oil than were the fish. The highest mortality was 9 percent at the 60 percent OAS concentration. There was no significant difference in survival between the control and oil -exposed shrimp. Though porpoises swam in oil sheen and on an occasion in mousse, no mortalities or abnormal behavior was observed on any research cruise. Three oiled turtles which were found dead were turned over to the U.S. Fish and Wildlife Service. Autopsies at the Patuxent, Maryland, laboratory could find no causes other than oil for the deaths. Tissue analysis will further define this. Toxicity tests were conducted on zooplankton and benthic amphipods. The OAS, even at 50 percent concentration had little effect on the short- term survival of the amphipods. There was 100 percent survival at all test levels except the 40 percent concentration, which had a 95 percent survival rate. In tests conducted in concentrations from 1 to 40 percent OAS, zooplankton had a 75 percent or greater survival rate. Control survival was 67 percent and was not significantly different from test animals. Tests on both the zooplankton and amphipods indicated that the IXTOC I oil was not acutely toxic to either one. CONCLUSIONS IXTOC I oil failed to impact large areas of marshlands. Small amounts of oil that entered inlets appeared to have little or no measureable effects on the productivity of marshes and inlets. This was observed following the impact of IXTOC I oil to a salt marsh, and also through physiological bioassays on representative phytoplankton and seagrasses. During the period of heaviest oiling of beaches, population densities of wading and shorebirds remained low. Substantial increases in bird populations occurred after the natural removal of oil from beaches by tropical storms and with an influx of newly arriving migratory bird species. 168 Birds were observed to avoid oiled portions of beaches and to move to other habitats during periods of heaviest oiling. No more than ten (10) percent of the bird population utilizing beaches was oiled at any time and few carcasses were found. Physiological bioassays were run using weathered IXTOC I oil on birds related to the peregrine falcon and the whooping crane. It was concluded that neither peregrines nor whooping cranes would be affected by the consumption of oil-contaminated prey. Monitoring of infaunal populations at oiled beaches indicated measur- able changes in the population size. Total population densities were significantly reduced in the lower intertidal zone and in the second bar and trough of subtidal habitats. Numbers of crustaceans (mole crabs and amphipods) were significantly lowered in both zones following the oil spill. It was difficult to distinguish the effects of the oil spill from natural factors, especially storms and natural population variations. Results of acute (96 hour) toxicity tests, exposing IXTOC I oil to dominant infaunal organisms, indicated no significant mortality. These results support the findings of field studies, thus suggesting that IXTOC I oil was not acutely toxic to beach fauna, although sublethal effects (significantly decreased respiration rates and avoidance behavior) were observed in oil- exposed mole crabs. Results of acute toxicity tests, conducted on subtidal amphipods and zooplankton, suggested that IXTOC I oil was not toxic to these species. Additional toxicity tests conducted on adult redfish, seatrout, and brown shrimp, indicated that IXTOC I oil was not acutely toxic to these commercially important fisheries species. However, high mortalities were observed in larval and juvenile fish species tested. Toxicity was greatest in larval redfish as many deformities in eggs and larvae were observed. Comparisons of redfish larval, toxicity, indicated that the oil accommodated seawater (water soluble fraction plus small oil microdoplets of mousse) fraction was more toxic than the water soluble fraction of the IXTOC I oil. Additional redfish larval tests indicated that the mousse fraction was nearly 100 percent toxic. The results of the studies may suggest that toxicity to redfish larval may be due to smothering rather than chemical toxicity per se, since the mousse and oil-accommodated seawater fractions were more toxic than the water soluble fraction. High mortalities were also observed in juvenile seatrout. In open water situations such as the Gulf of Mexico, adult organisms may be able to avoid contaminated areas; however, impacts to eggs, larvae, and juveniles would occur in heavily oiled areas. All toxicity tests were conducted using the POINT BAKER mousse sample of the IXTOC I oil, which did not contain high concentrations of many aromatic oil fractions such as napthalene, methyl napthalene, dimethyl napthalene, and trimethyl napthalene (Ed Overton, Univ. of New Orleans, New Orleans, Louisiana; personal communication). These compounds are acutely very toxic to many adult marine organisms. The small amount of toxicity observed in tests with adults may have resulted from the very small concen- trations of these toxic aromatic compounds in the POINT BAKER mousse. 169 The effect of IXTOC I oil on marine mamrR'als are preliminary at this time. General indications are that there were no observable effects to marine mammals found during the different research cruises conducted at various times during the spill. Initial findings indicated that sea turtle mortalities were possibly oil-related. However, preliminary findings suggest that incidences of mortality were rare and isolated cases. These supportive ecological studies have indicated that IXTOC I oil did visibly impact considerable shoreline areas in South Texas. Field studies conducted at marshes and beaches suggest that IXTOC I oil may have caused: (1) significant population shifts and avoidance by major wading and shorebird species at heavily oiled beaches; (2) subtle reductions of infaunal population densities throughout the intertidal beach habitat, with significant declines occurring only in the lower intertidal zone and the second bar and trough of subtidal habitats; major population declines were only observed in two species of crustaceans [mole crabs (intertidal) and amphipods (subtidal)]; (3) minor impacts to marsh vegetation were observed; and (4) minor impacts to marine turtles and mammals were observed. However, it was difficult to distinguish the effects of spilled oil from effects from natural factors such as tropical storms, seasonality, and normal population variation. Laboratory studies conducted using POINT BAKER mousse samples of the IXTOC I oil indicated that: (1) acute exposures of the oil -accommodated seawater fraction were not acutely toxic to dominant beach infauna such as mole crabs, surf clams, and polychaete worms, although significant sublethal physiological effects and avoidance behavior were observed in mole crabs; (2) acute exposures of the oil -accommodated seawater fraction to subtidal amphipods and zooplankton were not toxic; (3) acute exposures of the oil- accommodated seawater, water soluble, and mousse fractions to redfish larvae, were toxic, with highest toxicity being observed in the mousse and oil -accommodated seawater fractions (rather than the water soluble fraction); (4) acute exposures of the oil -accommodated seawater fraction to seatrout indicated significant toxicity in juvenile fish, but no toxicity in adult- sized fish; and (5) acute exposures of the oil -accommodated seawater fraction to brown shrimp were not toxic. Laboratory studies indicated that IXTOC I oil was not acutely toxic to the adult, marine organisms tested. These laboratory findings tend to support results from field studies which indi- cated that IXTOC I oil caused only limited impacts to beach infauna and other marine organisms. Results of subtidal amphipod and zooplankton toxicity tests were inconclusive in that both species were resistant to low concentrations of oil tested. However, effects of higher concentrations than those tested are unknown. 170 Chapter 6: References Afton, A.D. 1979. Time budget of breeding northern shovelers. Wilson Bull. , Vol. 91, p. 42-49. Aldrich, E.G., 1938, A recent oil pollution and its effects on the water birds of San Francisco Bay area: Bird Lore, Vol. 40, p. 110-114. Anderson, J.W. , J.M. Neff, B.A. Cox, H.E. Tatem, and G.M. Hightower, 1974, Characteristics of dispersions and water-soluble extracts of crude and refined oils and their toxicity to estuarine crusta- ceans and fish: Mar. 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Sci., Vol. 21, p. 171-185. 174 APPENDICES Beach Profile Stations to Measure Oil Distribution and Biological Impact Marine Cruises Common and Taxonomic Names of Coastal Biota 175 BEACH PROFILE STATIONS TO MEASURE OIL DISTIRBUTION AND BIOLOGICAL IMPACT Erich R. Gundlach, Kenneth J. Finkelstein, Daniel D. Domeracki , and Geoffrey I. Scott During the time IXTOC I oil was impacting the Texas beaches, extensive aerial photographs and taped observations were made during almost daily helicopter overflights. These records determined oil distribution along the shoreline and recorded oil transport and dispersal processes. The preparation of an oil-concentration map for the entire impacted coastline was a major objective of each flight. In addition, 103 field stations were established and visited between 17 July and 10 October, 1979. The are shown in Figure A.l. Many of these stations, particularly those in the oil-impacted areas, were revisited several times. Two types of stations were established: Profile stations: 65 total, set up along exposed and lagoonal beaches to permit geomorphic and biological characterization of all habitat types. Photo stations: 38 total, especially along each of the three major inlets, set up for rapid determination of oil concentra- tions, obvious biological impact, and habitat type. At each of the profile stations, the following work was completed: 1. The topographic profile of the beach was measured; concurrently, notations were made of all relevant changes to the beach, includ- ing the nature and occurrence of the oil and biological impact. Permanent stakes were set to mark the location of the profile. 2. Sediment size was estimated along the profiles. 3. Trenches were dug to determine the distribution of buried oil. Each trench was sketched and photographed in detail. 4. A sketch was drawn to show general coastline geomorphology , resi- dent biota, and surficial oil distribution. Several examples are given in the discussion of oil impact (see Chapter 2, Part II). 5. The beach was photographed in detail. 177 CORPUS CHRISTIE • M'3 CTX 6< / CC-4» ^^^'•CTX^SIFl CC-2IFI#^ ^X^M-IIFI M'2 PROFILE LOCATIONS ^— * MEXICO .ov^ o^ hN^^ ico 30 KILOMETERS MILES 30 Figure A. 1 Location of profile stations along the south Texas coast. Sites surveyed before oil impact provided baseline data to monitor ecological and physical changes. 178 6. Biological observations were made as follows: a. Macroflora and macroepi fauna were censused by projecting a 20-grid square over a randomly selected 1 m^ area in each interval. These censuses were taken at random within the interval and recorded in grid per taxon units. Macroflora counts were later converted into percent coverage while macroepi fauna were recorded as number of individuals of each taxon per 0. 25 m^ b. Macroinfauna were censused with triplicate can cores driven straight into the substrate along the upper, middle, and lower beachface. Infaunal samples were field-sieved with 1-mm mesh, or bagged for lab sorting. Samples for lab analysis were fist narcotized with propylene phenoxethol , stained with rose bengal, preserved in 10 percent formalin, and then bagged and labeled. 7. Various samples of sediment biota were collected for possible chemical analysis as described in a later section. At photo stations, the site was visually inspected, photographed, trenched, and sketched. Observations were recorded in a field notebook and on recording tape. Chemical, biological, and sedimentary samples were taken when deemed necessary. CALCULATION OF OIL QUANTITY ALONG THE SHORELINE At each profile station, a topographic profile was measured, during which the surface oil concentration (in percent) was estimated for each sample interval by the three members of the field team. The thickness of oil in each interval was measured. Based on surface concentrations, the amount of oil coverage was determined to be very light, light, moderate, or heavy as designated in Table A. 1 . Table A. 1 Oil coverage of an 8- to lO-m Intertidal Zone Very light 10 percent Light 10 to 24 percent Moderate 25 to 64 percent Heavy 65 percent 179 Examples of light, moderate, and heavy concentrations are shown in Figures 2.14 to 2.18. In addition to surface oil coverage, subsurface oil was examined and measured (thickness and extent) by trenching. The total oil along the shoreline was then calculated as follows: Surface oil was calcuated by the following formula: LWD X %C X SG X %0 yields grams (per meter length of oiled beach) where (for each interval along the beach profile): L = length of beach oiled in cm - calculations are made for 100-cm (1 m) interval, and then multiplied by the entire stretch of beach characterized as light, moderate, or heavy. W = width of oiled zone in cm. D = thickness of oil in cm (0.3 to 0.4 cm was common). %C = percent of surface area covered by oil (in decimal units). 3 SG = specific gravity of the oil in g/cm (assumed to equal 1.0). %0 = percent oil in mousse in decimal units (assumed to be 0.4; 40 percent oil, 60 percent water). Example: Station STX-4C, Mustang Island, 20 August 1979. 100 X 140 X 0.4 X 0.05 x 1.0 x 0.4 = 112 g 100 X 130 X 0.4 X 0.05 x 1.0 x 0.4 = 104 g 100 X 400 X 4.0 X 1.00 x 1.0 x 0.4 = 64,000 g 100 X 600 X 4.0 X 0.95 x 1.0 x 0.4 = 91,200 g 155.4 kg Total length of heavily oiled zone = 500 m x 155.4 kg = 77.7 metric tons (1000 kg = 1 metric ton = 1 long ton = 2200 lbs) Buried oil was calculated by the following formula: LL T. x %0 X SG b b 180 where: L = length (cm) of oiled beach at each sample interval. L. = length (cm) of buried oil-sediment layer measured perpendicular to shore. T. = thickness (cm) of the buried layer. %0 = percent oil within the layer (assumed to be 10 percent), 3 SG = specific gravity (g/cm ) of the oil. As noted previously, units are in centimeters and grams. OIL/SEDIMENT SEPARATION CALCULATIONS A chemical separation of oil from sediment was done in selected samples from temporary cleanup piles on Mustang and North Padre Islands to arrive at an estimate of the quantity of oil removed during cleanup. The calcula- tion involved the following steps. 1. Oil was removed from each weighed 150-gram sample by a 36-hour Soxhlet extraction, using 50-50 methanol-benzene solvent. 2. Solvent was removed with a rotary evaporator for 15 hours. 3. The remaining oil was weighed. 4. A 20-m£ sample of clean sediment was weighed to determine bulk density (includes pore space) of the sand. 5. Percentage oil by weight was converted to percentage oil by volume by the formula: oil weight: (specific gravity, 0.94 g/cm^) weight clean sand: (bulk density, 1.41 to 1.54 g/cm^) 6. Percentage oil by volume was multiplied by the measured volume of oil-sediment layer at each cleanup storage site to determine total vol ume oi 1 . 7. Total volume of oil was multiplied by the oil specific gravity to obtain the total weight of oil at each sample site. 181 CHEMICAL AND SAMPLING AND CHAIN OF CUSTODY Chemical and biological samples collected for chemical analysis between 17 July and 10 October 1979 were taped shut with signatures attached across seals to maintain chain-of-custody. The samples were frozen at -17°C and turned over to a NOAA representative responsible for all accumulated chemical and biological samples. Chemical sampling from 26 September to 3 October was conducted using hexane-washed glassware. Glassware was washed with soap and tap water, rinsed three times in tap water, washed with reagent-grade hexane, and then a final time with nano-grade hexane. Caps were placed over aluminum foil previously baked at 260°C for 2 hours. 182 B MARINE CRUISES Edward Overton VALIENT Cruise (USCG) 16-21 July 1979 The cutter VALIENT cruise was undertaken to determine surface circulation on the Continental Shelf of the western Gulf of Mexico, and to establish the regime of water currents for increasing the accuracy of forecasting oil movements. During the 6-day cruise, the participants also collected samples along the leading edge of the slick before it entered U.S. territorial waters for analyses of the physical properties and chemical characteristics of the oil. They also observed and logged the occurrence of oil in the gulf water. POINT BAKER Cruise (USCG) 27-28 July 1979 The POINT BAKER cruise sampled the leading edge of IXTOC I oil before oil patches entered U.S. territorial waters early in August 1979. The sample collected was for studies of short-term (acute) lethal and sublethal effects on local Gulf of Mexico biota, to be performed at Univer- sity of Texas Marine Science Institute/Port Aransas Marine Laboratory (UTMSI/PAML). Also, a preliminary chemical characterization of the POINT Baker sample was completed and compared with analyses of other available samples of IXTOC I mousse or oil suspected to be of IXTOC I origin. FSU-I, LONGHORN Cruise 26-31 July 1979 Cruise FSU-I, made aboard the LONGHORN (UTMSI/PAML) and sponsored by the NSF, was undertaken to install six deep-ocean current water arrays as part of the Florida State University project (under the direction of Wilton Sturges) to study the Western Boundary Current in the Gulf of Mexico (Amos, 1980). The cruise also served as a shake-down exercise in deployment and operation of a shipboard computer system coordinating STD casts, XBT profiles, and continuous sea-surface temperature sensors. 183 The LONGHORN departed Port Aransas, Texas, and proceeded to below the 24th parallel, off the Mexican coast, before turning north to return to Port Aransas. During the cruise, considerable amounts of oil were encoun- tered and a log was maintained of these sightings. As the primary objectives of the survey did not include sampling spilled oil, only a few samples of opportunity was taken. The most common form of oil encountered was tar balls ranging from pea-sized and smaller to about 20 mm in diameter. The tar balls were frequently aligned and concentrated in windrows. Some tar balls were observed sinking or suspended several centimeters below the surface, especially in windrows. Breakdown of the tar balls could be observed as a "wake" of sheen, often present behind the oil particles. LONGHORN I (Mousse I) 4-8 August 1979 The LONGHORN I cruise was the initial search for the presence of IXTOC I oil in the water column off the southern Texas coastline, encompass- ing the region from Port Aransas south to the Mexican border (Amos, 1980). The cruise was initiated at a time when no IXTOC I oil had been sighted in U.S. waters, but was approaching rapidly from the south. An estimate of the amount of submerged oil was urgently needed by the spill response strike teams on the mainland so they could assess the potential effective- ness of booms being placed across various barrier island passes to protect the sensitive estuarine areas. Divers made visual observations and collected samples. Concurrent with the more immediate objective, a variety of samples were taken to begin investigation of the oil spill phenomena. Although the LONGHORN I was a relatively short and hurried cruise, several classes of samples were collected, including oblique plankton tows, whole water samples, filtered particulates, surface and submerged hydrocarbons (sheen, mousse, tar), and sediments. Physical oceanographic measurements included STD casts, XBT's, rosette samples, and current drifters. LONGHORN II Cruise (Mousse II) 15-22 August 1979 The LONGHORN II cruise surveyed hydrocarbon concentration gradients along the Texas-Mexican coastline at the peak of IXTOC I impact in U.S. waters (Amos, 1980). The ship traversed the region from Port Aransas to approximately 150 miles south of the Mexican border. Continuous sea-surface observations were maintained and logged hourly. Divers were deployed frequently for subsurface observations. In mid-to-late August, oil was encountered throughout the entire cruise track and was rarely out of sight. Tar balls (1 to 3 cm in diameter) and, to a lesser degree, slightly larger conglomerants (up to 20 cm in diameter) were the common forms. Tar balls were found with or without associated sheen, depending on sea conditions, and were more often in windrows when a breeze was blowing (as was usual). A single large patch of heavy mousse was encountered and sampled at Station V-GA. While the LONGHORN occupied this station, an unidentified aircraft appeared and applied dispersant to the mousse patch. 184 Sampling stations were located along four transects (II-7 stations, IV-7 stations, V-8 stations, VI-3 stations) with the line of stations run- ning roughly west to east from the inner Continental Shelf to the shelf/slope dropoff. Physical oceanographic measurements included STD casts, rosette samples, XBT's, and surface current metering. Sampling included hydrocarbons (sheen, mousse, tar balls), whole and filtered water, pumped articulate filtrates, oblique plankton tows, and sediments. A few samples of biota were also retrieved. Observations on the physical states of oil encountered were logged. Tar balls, more descriptively called tar flakes, were by far the most common form of oil sheen. Their median diameter was probably less than 3 cm and only rarely were they up to 20 cm wide; frequently, they were less than 1 cm in diameter. The tar balls occurred in patches, streaks and, most often, in windrows. When the wind was calm or light the tar balls spread out over the surface and invariably a sheen patch formed. Tar balls could be seen "bleeding" irridescent wakes into the sheen, particularly in sunlight. Oil-produced sheen was never encountered without tar balls. Conversely, however, tar balls were often found without a surrounding sheen. As the wind increased, the patches of sheen broke up into smaller patches, then into wide streaks and finally into windrows. The stronger the wind, the less shiny was the surface of the slick and in winds of >20 knots, it was hard to tell whether or not a sheen was present. When the tar balls were concentrated in windrows they could often be seen sinking, sometimes out of sight and at other times returning to the surface. When the winds were calm and the tar balls were in patches of sheen, they were never observed to sink. Tar balls were seen beneath the surface by divers whenever there was oil on the surface. They were found mainly in the upper 10 feet, but were observed as deep as 65 feet. The concentration of oil below the surface was much lower than that on the surface. Particles were usually only a few millimeters in diameter and were almost always described as thin and flaky. No obvious change in particle density coincident with the thermocline was reported, but a general thinning out of particles with depth occurred. Particles were found down to the nepheloid layer (turbid water zone found adjacent to the bottom), but not within the nepheloid layer, nor were they seen on the bottom by the divers at any station or found in any of the sediment samples. Tar balls are tarlike pieces of oil, ranging from light-brown to black. After collection, they easily fused together, were sticky to the touch, and readily liquified in sunlight to a dark, viscous liquid. Mousse is a semi liquid emulsion of (IXTOC) oil and sea water, pre- sumably named for its color (milk-chocolate) rather than its texture. In the nomenclature adopted for the LONGHORN cruises "mousse" refers only to 185 the large patches of thick oil, still somewhat liquid, before it broke up into tar balls. Other scientists have referred to tar balls as mousse (indeed, tar balls may coalesce and in sunlight become mousse again). The "Big Mousse Patch" At 1110 CDT, 18 August 1979, en route to station V-6, the LONGHORN encountered a large area of heavy oil completely covering the sea surface. It Was reddish to chocolate-brown in color, highly viscid in texture, and contained much debris. It was presumed that this was a classic example of "mousse" and station V-6A was initiated. This was th only genuine mousse encountered on the LONGHORN II cruise. A strong odor, described as like an "old gas station," permeated the area. The mousse made a memorable sound as it "slurped" against the side of the ship. When the surface of the oil parted, several schools of small silvery fish and some sharks could be seen swimming below perhaps due to the shade provided by the oil cover. Shortly after the mousse was found, a DC-6 aircraft appeared and sprayed the patch, presumably with a dispersant; after the spraying had ceased, the LONGHORN steamed back into the mousse and found the area of the patch appeared smaller, as if the oil had been "herded" by the chemical. Its texture was now more liquid but the layer was thicker, although it was difficult to judge exactly what the immediate effects of the spraying had been. Another surface sample was taken, but due to the extremely noxious smell surrounding the patch, making some of the crew feel ill, the LONGHORN retreated from the mousse. The purpose for the EPA-sponsored OSV ANTELOPE cruise was to obtain 'ground truth' to accompany aerial observations of sheen and mousse in the northwestern gulf, as well as to survey the water column and bottom for accumulations of IXTOC I oil. Objectives as outlined in the cruise plan were to: 1. Perform sea-level observations of surface oil, mousse, and sheen concentrations in conjunction with aerial overflights. 2. Evaluate the physical chemical phases that the oil has taken. 3. Examine subsurface distributions of oil. 4. Evaluate the concentrations and composition of the oil sheens, mousse, and tar on a real-time basis using spectrof luorometry. 5. Relate oil concentration observations to physical phenomena (water column structure, etc.). 6. Update the offshore distribution of oil to enable possible time of impacts on Texas and/or Louisiana to be estmated. 7. Examine the potential presence of toxic components in waters adjacent to and beneath mousse patches using in situ bioassays. 186 8. Investigate sediment and benthic samples, specifically in near- shore mixing areas and in the nepheloid zone, for petroleum hydrocarbons. 9. Examine selected species of fishes and invertebrates to determine potential body burden or food web uptake of petroleum hydrocarbons. 10. Obtain fresh-as-possible samples of water-borne mousse for examina- tion for microbial degrading organisms and to add to better understanding of photo degradation steps. The cruise comprised three legs with the ANTELOPE putting into port for several days between segments. Leg I, 25 August to 11 August. The general cruise track was from Pensacola down to 28°00'N latitude to the Flower Garden reef and then up to Galveston, Texas. Samples of water, tar balls, oil slicks, oiled sargassum weed, and the water under tar ball and sargassum slicks were obtained. No large slicks were observed during this leg of the cruise. Some hydrocarbons detected by on-board fluorimetry were attributed to either shipboard contamination or background from the multitude of offshore oil drilling platforms in the region. Leg II, 29 August to 31 August. The cruise track of this leg started at Galveston, ran to the Flower Garden reefs, back near shore between Galveston and Corpus Christi, Texas, then south in response to a request from a Coast Guard overflight before coming into port in Corpus Christi. Sediment samples were obtained, neuston tows were made, and a vertical upward tow was made using the bongo nets. Not all samples obtained on this leg were analyzed (due to personnel limitations), but no oil appeared in the analyses that were conducted. Neither was any oil observed on the sea surface that was thought to be of Mexican origin. Leg III, 3 September to 8 September. Leg III of the cruise was scheduled to sample along three lower BLM transects that had been occupied by the LONGHORN two weeks earlier. Benthic and pelagic biological ocean monitors were obtained. The cruise covered the 3rd (second from most southern) BLM transect, and sampled at the most landward station of the 4th (most southern) BLM transect before being terminated early due to engine problems. At 26°G8.6'N latitude and 97°06'W longitude, samples of water, mousse, degraded oil, water-borne tars and tar balls, and mousse, tars and tarred sediments from the beach were obtained for bacterial and chemical analyses. 187 R/V RESEARCHER/PIERCE Cruise, 11-27 September 1979 The NOAA ship RESEARCHER and a companion vessel, the G.W. PIERCE (Tracor Marine, under contract to NOAA) departed Miami, Florida, on 11 Septem- ber to survey and sample in the region of the IXTOC I wellhead, Bay of Campeche, and to track the oil northwa^'d into U.S. territorial waters. Objectives of the cruise were to: 1. Determine the effects of physical, chemical, and microbial weather- ing of spilled oil in the marine environment on its chemical and physical properties. 2. Determine the fate of spilled oil in the marine environment. 3. Estimate the microbial degradative input to weathering of spilled oil. 4. Study the effect of spilled oil on bacterial and planktonic communities. The vessels conducted coordinated operations in the vicinity of the well head, with the RESEARCHER sampling just outside the main plume of spilled oil and the surrounding vicinity, while the PIERCE occupied stations within the plume and in other areas with heavy concentrations of mousse. A helicopter carried by the RESEARCHER was used for reconnaissance flights to plan and coordinate sampling strategies and to observe the physical formation and mutation of the oil plume as it moved away from the IXTOC I well head. Small launches were deployed by the RESEARCHER for sea-level sampling of mousse, sheen, and air over slicks. Microbiological investigations and sampling formed a significant part of the research efforts conducted during the joint cruise. Long-term incubation experiments were performed on-board the PIERCE to estimate potential bacterial degradative effects on the weather of mousse. Microcosm experiments conducted aboard the RESEARCHER served to measure assimilation of 14p- labeled amino acids, hexadecane, and naphthalene, to estimate bacterial metabolic rates and uptake. Selective changes in species makeup of microcosm bacterial communities were also monitored and compared with the 'real-world' samples. At a total of 46 stations occupied by the two vessels, extensive collections of many classes of samples were taken, including physical oceanographic measurements, microbiological samplings, and samples destined for detailed chemical analyses. The combined effort generated over 1,500 samples of all classes, with roughtly 800 of these for chemical assay. The PIERCE occupied 17 stations, most of which were in the immediate vicinity of the well head. The RESEARCHER occupied 29 stations (excluding samples of opportunity), which fall into two groups: 1. Stations in the vicinity of the well head and below the 23rd parallel off the Mexican coastline. 188 2. Stations comprising two sediment sampling transects made off the southern Texas coastline, one of which corresponds to the previous BLM-STOCS transect IV, for which there is prespill baseline data. Two additional stations, where more complete chemical sampling was peformed, were occupied offshore of Brownsville and Corpus Christi. Several samples of opportunity were taken from the beaches on either side of the U.S. -Mexican border. The second group of RESEARCHER samples represents samples that could be applicable to a damage assessment program for the south Texas environments. Analysis of samples collected in the vicinity of the well head will provide much insight into weathering processes, and hopefully, provide an unequivocal characterization of IXTOX I oil. Their usefulness to damage assessment beyond this information is limited. RESEARCHER Operations Physical oceanographic measurements taken throughout the cruise con- sisted of STD profiles of all stations and XBT sections fired every 15 n mi when steaming in water depths exceeding 100 m. Sampling of the water column was coordinated with salinity and/or thermal profiles. Samples included whole and filtered water sediments, sediments, flotsam, and water and beached hydrocarbons. Oil Dispersal Observations During the time the vessels were near the IXTOC I well head (15-21 Sep- tember), the well was on fire and putting out large volumes of crude oil on the sea surface. Flames from the well covered approximately 1 acre. Two relief well platforms, the AZTECA and INTEROCEAN II (of Houston), were near the well site, the AZTECA being located about 1/4 mile to the north and INTEROCEAN II about 1/4 mile east of the burning well head. Upon our arrival on 15 September, the well output was to the northeast at about 055° true. Previous reports, through around 10 September, indicated that earlier output of the well had been to the west and northwest. The visible plume from the output extended northeast for at least 35 n mi . Output continued in this 055° direction until 20 September, when it started to swing to a more southerly heading. Upon our departure on 21 September, the output was roughly toward 145° true. Crude oil could be observed to be boiling up at the surface near the well head and fire. It remained sharply delineated from the surrounding sea and there was little observable sheen around the edges. The plume of oil funneled out and widened. A short distance from the well head, signifi- cant amounts of sheen began to bleed off the edges of the still- solid plume of emulsified oil. Perhaps 10 miles (16 km) down plume, heavy patches of sheen appeared within the oil -mousse. Still farther down plume, the mousse became more patchy and streaked, with much sheen interspersed, and 189 when farther out, sheen began to predominate, with the mousse, now more solid in appearance, forming raft- like patches that tended to entrap and incorporate floatsam (weeds, bottles, etc.)- The entire surrounding sea appeared milky. But in areas where sheen predominated, there was an obvious, pronounced milky edge along the sheen patches (suspended sediments?, dispersants? , water soluble fraction?). Pronounced color changes were observed to occur both diurnal ly and with increasing distance from the well head and for some distance down plume, the oil appeared chocolate brown. With increasing distance and/or sunlight the oil-mousse took on a brighter, richer, reddish-brown tone (which may have been attributable simply to better lighting). The color was not homogenous, but rather, a swirled appearance was evident. In some places, swirls of very bright orange oil were interspersed. FSU-II Cruise (NSF), 13 October - 6 November Cruise FSU-II, made aboard the LONGHORN (UTMSI/PAML) and sponsored by NSF, was undertaken to recover current meter arrays deployed during FSU-I the previous July. Several of these were refurbished and redeployed, while others were left on location. As described previously, the cruise track extended belo the 24th parallel into Mexican waters. A related objective was to measure the thermohaline structure of the water column via STD casts and XBT selections. As on three previous LONGHORN cruises, surface observations were made for the presence of IXTOC oil and a few samples were retrieved for chemical assay. At the time of this cruise, the currents were no longer bringing oil ashore onto Texas beaches. Tar balls were the major form of oil encountered during the FSU-II cruise. Sheen was observed only once. Tar balls were generally small, perhaps smaller than observed on the three previous LONGHORN cruises. They frequently occurred in windrows and together with Sargassum. At several locations, tar balls of considerably darker coloration were mixed with the more traditional mousse-colored balls. Occasionally these darker pieces had attached goose barnacles. When sampled, the darker "tar balls" were found to be small pieces of driftwood with goose barnacles growing on them. In contrast to the previous cruises, there were extensive areas where no oil was sighted. 190 LONGHORN IV Cruise (USCG) 16 November - 13 December With the objective of surveying postimpact accumulations of IXTOC I petroleum residues in Texas waters, UTMSI/PAML was contracted by NOAA in November 1979 to conduct extensive samplings of offshore, nearshore, and estuarine passes (Griffin, 1980). This study area was bordered on the north by Pass Cavallo and continued southward to Port Isabel. This effort culminated in a series of four cruises aboard the R/V LONGHORN, which examined the various environmental zones by the following time-table: Southern stations-Port Mansfield, Port Isabel... 16 to 20 November Middle Stations 30 November to 3 December Northern Stations and Pass Cavallo 7 to 10 December Port Aransas 13 December A total of 131 nearshore/offshore and 12 channel stations were occupied, with the study area divided into north, middle, and south sections (lettered N, M, and S followed by sequential sample numbers). Seaward stations were located along the 15-, 30-, 60-, 120- , and 180-ft isobaths with approximately 5 miles between the 15-, 30-, and 60-ft stations and approximately 10 miles between the 120- and the 180-ft stations. By design, stations for the offshore survey included several of the previous Bureal of Land Management- South Texas Outer Continental Study (BLM-STOCS) program stations, as the BLM-STOCS program constitutes a body of prespill baseline data for comparison. The BLM-STOCS program sampled 25 stations among four transects with the inner three stations of each transect reoccupied in this survey. Samples collected included hydrocarbons and macrobenthic organisms; sediments for hydrocarbon and trace metal analysis; sediments sieved for infauna with a subsample retained intact for particle size analysis; sediments for micro- biology; and physical oceanographic measurements of bottom currents, surface salinity and temperature, and bottom salinity and temperature. BEACH SAMPLING ACTIVITIES FOR OIL HAZMAT Team Initial Sampling Effort In mid-August, at thetime of initial impact along the southern Texas coastline, NOAA/HAZMAT personnel collected beached hydrocarbons. These samples represented the first collected along Padre Island beaches that were suspected of coming from the IXTOC I blowout. One of these samples (tar balls) was analyzed at UTMSI/PAML and reported by Parker (1979). 191 Research Planning Institute Research Planning Institute (RPI) of Columbia, South Carolina, was contracted by NOAA to conduct biological and geological sensitivity analyses of the south Texas coastlne from Port Isabel to the Sabine River, including the Laguna Madre. Concurrent with these efforts and following the sensitivity analyses, samples of beach sediments, infauna, and beached tars were collected at over 100 stations along the barrier islands and in adjacent coastal lagoons, bays, and marshes. URS - Post- Impact Samples of Beach Tars In the latter part of November and early December 1979, Peter Sturtevant (URS) collected various beached hydrocarbons along the Texas barrier islands that had been impacted by IXTOC I oils not removed by clean-up operations. The rationale was to verify the identity of the hydrocarbons while also attempting to sample various types of states of beached oils. FISHERIES AND WILDLIFE SURVEY STUDIES A cooperative program was formulated between Texas Parks and Wildlife Department (TPWD), National Marine Fisheries Services (NMFS), and Texas A&M University to conduct a joint research cruise to determine whether shrimp and/or finfish caught near oil on the sea surface had been contaminated or were otherwise unmarketable. Organoleptic tests (visual and oilfactory) were performed by Food and Drug Administration (FDA) personnel upon catch species, with only faint petroleum odors not sufficient to warrant production rejection detected. Additionally, catch aliquots were sent to the FDA Dallas laboratory for analyses of petroleum hydrocarbons, including polynu- clear aromatics (PNA's). Other aliquots were sent to the NMFS Charleston laboratory for further organoloeptic (taste) testing. Samples were scheduled to be analyzed for oil contamination of gut contents by the NMFS Beaufort Laboratory. Fifty-five samples were collected at six stations. Standard 40-ft shrimp trawls were used to collect all speciments. A used net was fished in sheen-covered waters (stations 1 through 4) and a new net was fished in waters having no apparent sheen (stations 5 and 6). A single mousse sample was taken for reference. 192 Fisheries Products Monitoring - NMFS The National Marine Fisheries Service (NMFS) undertook to monitor dockside catches of fisheries products for possible petroleum contamination along selected Gulf of Mexico ports. Shrimp were obtained from commercial boats beginning 1 August 1979 and weekly at five ports in Texas - Brownsville, Port Aransas, Freeport, Galveston, and Port Arthur - until the end of November. After that monthly samples were taken (except in the Galveston and Port Arthur areas, which remained on a weekly basis through 31 January 1980 in response to the BURMAH AGATE* spill). In late October, shrimp sampling began at several Louisiana ports: Cameron, Delcambre, Leeville, Houma, and Venice. Also, in late December a weekly finfish collection was initiated at selected ports, dependent upon species availability. For Texas, this includes red snapper at Brownsville and flounder at Port Aransas. In Louisiana, spotted sea trout and red drum are taken at Leeville and Houma. All samples will be analyzed for traces of hydrocarbons in tissues. Fisheries Products Monitoring - FDA In August 1979, Food and Drug Administration (FDA) agents began monitor- ing fisheries products along selected Gulf of Mexico ports for possible petroleum contamination of commercial species. This project stemmed from legal mandates making FDA responsible for protecting consumers from contami- nated and/or otherwise unmarketable fisheries products. Aliquots of commer- cial shrimp, shellfish, crab, and finfish species were obtained from domestic seafood processors and are awaiting analysis for polynuclear aromatic (PNA) contaminants. No analyses have been completed to date, as FDA- approved methodology is under development. Further sample collection has been postponed until analyses begin, and at that time, collections will be resumed. Patuxent Toxicity Studies Several samples of oil were sent to the Patuxent National Wildlife Refuge for use in petroleum toxicity bioassays. A samples of oil taken near the wellhead by Oil Mop, Inc., was used in ingestion studies of the Americal kestrel to simulate exposure of perigrine falcons, an endangered species that winters in Texas. Also, samples of mousse and tar received *M/T BURMAH AGATE is a tanker which burned after a collision 11.3 km offshore of Galveston on 1 November 1979, spilling a major portion of the 290,000 barrel cargo. 193 from Padre Island beaches were slated for use in related studies. Results of these studies are forthcoming. In addition to oil samples, Patuxent received approximately nineteen birds and six sea turtles from spill-related mortality along the Texas coastline. These were autopsied and stored in freezers for possible future chemical analyses of tissues. UTMSI/PAML Mussel Watch Program In conjunction with the ongoing National Mussel Watch Program, a limited number of oyster samples were obtained at various inshore localities along the Texas coastline to detect a chronic increase, if any, in hydrocarbon content of local populations due to the influx of IXTOC I oil. Samples were collected by UTMSI/PAML after the IXTOC I impact in late September and early October at Port Isabel, East Matagorda Bay, Port Mansfield, and Port Aransas. 194 c COmON AND TAXONOniC NAMES OF COASTAL BIOTA PLANTS COMMON NAME SPECIES Alga bl ue- green Lyngbia confervoides other Sargassum Grasses saltgrass Distichi is saltwater cordgrass Spartina a1 ternif 1ora sea ox-eye daisy Borrichia shoal grass Halodule wrighti i turtle grass Thai assia testudimum widgeon grass Ruppia maritima othei Cassia fascrulata Panicuia ararum, Sal icornia Mangrove, black Avicennia 195 BIRDS Cormorant, olivaceous Phalacrocorax o1 ivaceus Crane, whooping Grus americana Duck, black-bellied whistling Dendrocyqna autumnal is Duck, fulvous whistling Dendrocygna bicolor Duck, mottled Anas fulvigula Duck, redhead Aythya americana Egret, reddish Dichromanassa rufescens Falcon, peregrine Falco peregrinus Goose, Canada Branta canadensis Goose, lesser snow (not found with lesser prefix) Goose, white-fronted Anser albifrons Gull, laughing Larus atricil la Heron, little blue Florida caerulea Oystercatcher, American Haematopus pal liatus Pelican, brown Pelecanus occidental is Pelican, white ---Pelecanus erythrohynchos 196 Birds (cont'd) Plover, snowy- ■Charadrius alexandrinus Plover, Wilson's- ■Charadrius wilsonia Skimmer, black- Rhynchops nigra Spoonbi 1 1 , roseate- •Ajaia ajaia LAND MAMMALS Bat- (not specific) Coyote- Canis latrans Fox, grey- Urocyon cinereoargeneus Ground squirrel (not specific) Jackrabbit- (not specific) Kangaroo rat- (not specific) Skunk- ■Memphitis mephitis Dolphins MARINE MAMMALS AND TURTLES bottle-nosed- Tursiops truncatus bridled- Stennella frontalis 197 Marine mammals and turtles (cont'd) rough- toothed Steno bredanensis spotted Stennel la plagiodon Manatee, West Indian Trichechus manatus Seal , West Indian — Monachus tropical is Turtle, green sea Chelonia mydas mydas Turtle, hawksbill Eretmochelys imbricata imbricata Turtle, leatherback Dermochelys coriacea coriacea Turtle, loggerhead Caretta caretta caretta Turtle, Kemp's ridley sea Lepidochelys kempi Whales, baleen black right Baleana glacialis blue Balaenoptera musculus common finback Balaenoptera physalus Whales, toothed goose-beaked Ziphius cavirostris gulf stream beaked 198 Marine mammals and turles (cont'd) killer, common- ■Orcinus orca killer, false- Pseudorca crassidens killer, pygmy- Feresa attenuata pilot- -Globicephala macrorhyncha sperm- Physteter catodon sperm, dwarf- Kogia simus sperm, pygmy Kogia breviceps FISHES Croaker, Atlantic •Micropogonias undulatus Drum, black- •Pogonias cromis Drum, red- Sciaenops ocel lata Flounder, southern- Paral ichthys lethostigma Kil lif ishes- Adinia, Cypriniodon, Poeul ia Mackerel , king- Scomberomorus cavalla Minnow, sheepshead- Cypri nodon variegatus Mullet- •Mugi 1 Pompano- Trachinnotus carolinius 199 Fishes (cont'd) Redfish Scianops ocel lata Sardine Harengula pensacolae Seatrout Cynoscion nebulosis Snapper, red Lutjanus campechanus SHELLFISH Auger, Atlantic Tereba dislocata Bubble shell Bulla striata Clams coquina Donas variabis razoi Tagebus plebius, Enis minor othei Mul ina lateral is, Anomalacardia cumiemeris Crabs blue Callinectes sapidus fiddler Uca ghost Ocypodus quadrata 200 Shellfish (cont'd) hermit C1 ibinarius vi ttatus mud Ri thropanopeus harri si , Neopanope texana texana, Panopeius herbsti i mud (flat) Eurypanopeus depressus stone Menippi mercenaria Lucine, thick Phacoides pectinatus Nerite, virgin Neritina virginea Shrimp arrow Tozeuma carol inensis brown car i dean Hippdyte pleuracantha, H. zostericola grass Paleomonedes sp. pink Penaeus duorarum snapping Alpheus heterochael is white other Cal lianassa jamai cense louisianensi s 201 Shellfish (cont'd) Snails mud Pol inicis dupl icatus, Nariarius vibex oyster drill Thais hematostoma MISCELLANEOUS INVERTEBRATES Beach hoppers • Orchestia, Talorchestia Keyhole urchin Mellita Gastropods Pagrus longicarpus, P. pollicaris Sand stai Astropecten Sea cucumbei Thyrone mexicana Worms lug Arenicola cristata parchment Chaetopterus variopedatus polychaete Eteone heteropoda, Laeoeris culveri , Scolopis squamata 202 us. GOVERNMENT PRINTING OFFICE: 577-846 — 1982 PENN STATE UNIVERSITY LIBRARIES ADDDD7D' MS3^3