Montana Slate Library 3 0864 1003 0526 0 BIOLOGICAL INTEGRITY OF STREAMS IN McCONE COUNTY, MONTANA BASED ON THE STRUCTURE AND COMPOSITION OF THE BENTHIC ALGAE COMMUNITY Prepared for: McCone County Conservation District and State of Montana Department of Environmental Quality P.O. Box 200901 Helena, Montana 59620-0901 Project Officer: Rebecca Ridenour DEQ Contract No. 200012-10 Prepared by: Loren L. Bahls, Ph.D. Hannaea 1032 Twelfth Avenue Helena, Montana 59601 July 21, 2004 STATE DOCUMENTS COLLECTIC: AUG 2 3 2004 MONTANA STATE KBRAP" ,,^.1515 E. 6th AVE. HELENA. MONTANA 5962C Primed on paper made from 100% recycled post-consumer fiber Summary In the summer of 2003, periphyton samples were collected from 1 1 sites on 5 streams in McCone County, Montana for the purpose of assessing whether these streams are water-quality limited and in need of TMDLs. The samples were collected following MDEQ standard operating procedures, processed and analyzed using standard methods for periphyton, and evaluated following modified USEPA rapid bioassessment protocols for wadeable streams. Diatom metrics indicate severe impairment from organic loading at the middle site on Horse Creek, Nelson Creek, the upper (Fairgrounds) site on the Redwater River, and the upper site on Sand Creek. Moderate stress from organic loading was indicated at the upper and lower sites on Horse Creek and the Cemetery Road site on the Redwater River. All other sites showed minor impairment from organic loading. Some of this organic loading may be internal and natural in origin. 'D' Severe impairment from sedimentation was noted at the lowest (Highway 13) site on the Redwater River. Moderate sedimentation was indicated at the lower site on Horse Creek and the fairgrounds and airport sites on the Redwater River. All other sites showed minor impairment from sedimentation except the upper site on Horse Creek, where the sedimentation index was normal for a prairie stream. Diatoms that indicate elevated concentrations of dissolved solids were common at all sites. Salinity, along with elevated organic loading, was the most probable cause of depressed diatom species richness and diversity. Diatom species indicate brackish waters at most sites, but somewhat lower levels of salinity were indicated in Horse Creek near mouth, Redwater River at the airport, and both sites on Sand Creek. Large percentages of nitrogen-fixing diatoms were recorded in the samples from Nelson Creek and the upper site on Horse Creek. Nitrogen is most likely the limiting nutrient at these sites. Cyanobacteria, many species of which can fix atmospheric nitrogen, were also common in Nelson Creek and the upper reaches of Horse Creek, as well as in Sand Creek and the Redwater River. Cyanobacteria were absent from Prairie Elk Creek and lower Sand Creek. Algae in the division Euglenophyta {Euglena and Phacus) are known to be especially tolerant of organic pollution. These algae were found only in samples collected from the Redwater River below the airport and at Highway 13. Conversely, Prairie Elk Creek was the only site where a pollution sensitive species {Achnanthidium minutissimum) accounted for more than 10 percent of the diatom cells. Two abnormal diatom cells were counted at the Fairgrounds site on the Redwater River. This is within the normal range for an unimpaired prairie stream. No abnormal cells were observed at the other 10 sites that were sampled for this project. Introduction This report evaluates the biological integrity', support of aquatic life uses, and probable causes of stress or impairment to aquatic communities in Horse Creek, Nelson Creek, Sand Creek, Prairie Elk Creek, and the Redwater River in McCone County, northeastern Montana. The purpose of this report is to provide information that will help the State of Montana determine whether these streams are water-quality limited and in need of TMDLs. The federal Clean Water Act directs states to develop water pollution control plans (Total Maximum Daily Loads or TMDLs) that set limits on pollution loading to water-quality limited waters. Water-quality limited waters are lakes and stream segments that do not meet water- quality standards, that is, that do not fully support their beneficial uses. The Clean Water Act and USEPA regulations require each state to (1) identify waters that are water-quality limited, (2) prioritize and target waters for TMDLs, and (3) develop TMDL plans to attain and maintain water-quality standards for all water-quality limited waters. Evaluation of aquatic Hfe use support in this report is based on the species composition and structure of periphyton (benthic algae, phytobenthos) communities at eleven sites that were sampled in the summer of 2003. Periphyton is a diverse assortment of simple photosynthetic organisms called algae that live attached to or in close proximity of the stream bottom. Some algae form long filaments or large colonies that are conspicuous to the unaided eye. But most algae, including the ubiquitous diatoms, can be seen and identified only with the aid of a microscope. The periphyton community is a basic biological component of all aquatic ecosystems. Periphyton accounts for much of the primary production and biological diversity in Montana streams (Bahls et al. 1992). Plafkin et al. (1989) and Barbour et al. (1999) hst several advantages of using periphyton in biological assessments. Biological integrity is defined as "the ability of an aquatic ecosystem to support and maintain a balanced, integrated, adaptive community of organisms having a species composition, diversity, and functional organization comparable to that of natural habitats within a region" (Karr and Dudley 1981). Project Area and Sampling Sites The project area is located in McCone County in northeastern Montana. Horse Creek, is a tributary of the Redwater River near Circle (HUC 10060002). Like the Redwater River, Sand Creek and Prairie Elk Creek are south side tributaries of the Missouri River (HUC 10060001). Prairie Elk Creek heads northwest of Circle in central McCone County and flows north to meet the Missouri River just south of Wolf Point. Sand Creek, the next drainage to the east of Prairie Elk Creek, heads north of Circle and enters the Missouri River a few miles downstream. Nelson Creek is a tnbutary of the Big Dry .\nn of Fort Peck Reservoir (HUC 10040104). The streams are located in the Northwestern Great Plains and Northwestern Glaciated Plains Ecoregions (Woods et al. 1999). The surface geology of the area consists of coal-bearing sedimentary rocks of the Fort Union Formation and sandstones and shales of the Montana Group (Renfro and Feray 1972). The climate is semiarid and continental, with cold winters and hot, dry summers. Upland vegetation is predominantly mixed grassland steppe (USDA 1976). The main land uses are livestock grazing and dry land farming. Periphyton samples were collected at 4 sites on the Redwater River, 3 sites on Horse Creek, 2 sites on Sand Creek, and 1 site each on Nelson Creek and Prairie Elk Creek (Table 1). Elevations at the sampling sites range from about 2,500 feet to 2,000 feet. The streams are classified C-3 in the Montana Surface Water Quality Standards. Methods Periphyton samples were collected following standard operating procedures of the MDEQ Plarming, Prevention, and Assistance Division. Using appropriate tools, microalgae were scraped, brushed, or sucked from natural substrates in proportion to the importance of those substrates at each study site. Macroalgae were picked by hand in proportion to their abundance at the site. All collections of microalgae and macroalgae were pooled into a common container and preserved with Lugol's (IKI) solution. The samples were examined to estimate the relative abundance and rank by biovolume of diatoms and genera of soft (non-diatom) algae according to the method described in Bahls (1993). Soft algae were identified using Smith (1950), Prescott (1962, 1978), John et al. (2002), and Wehr and Sheath (2003). These books also served as references on the ecology of the soft algae, along with Palmer (1969, 1977). After the identification of soft algae, the raw periphyton samples were cleaned of organic matter using sulfuric acid, potassium dichromate, and 3% hydrogen peroxide. Then, permanent diatom slides were prepared using Naphrax''"'^, a high refractive index mounting medium, following Standard Methods for the Examination of Water and Wastewater (APHA 1 998). At least 400 diatom cells (800 valves) were counted at random and identified to species. The following were the main taxonomic references for the diatoms: Krammer and Lange-Bertalot 1986, 1988, 1991a, 1991b; Lange-Bertalot 2001; Krammer 2002. Diatom naming conventions followed the Integrated Taxonomic Information System (http://ww\v. itis.usda.gov). For taxa not yet included in ITIS, naming conventions followed those adopted by the Academy of Natural Sciences for USGS NAWQA samples (Morales and Potapova 2000). Van Dam et al. (1994) was the main ecological reference for the diatoms. The diatom proportional counts were used to generate an array of diatom association metrics (Table 6). A metric is a characteristic of the biota that changes in some predictable way with increased human influence (Barbour et al. 1999). Diatoms are particularly useful in generating metrics because there is a wealth of information available in the literature regarding the pollution tolerances and water quality preferences of common diatom species (e.g., Lowe 1974, Beaver 1981, Lange-Bertalot 1979, 1996, Van Dam et al. 1994). Values for selected diatom metrics were compared to biocriteria (numeric thresholds) developed for streams in the Great Plains ecoregions of Montana (Table 2). These criteria are based on the distribution of metric values measured in least-impaired reference streams (Bahls et al. 1992) and metric values measured in streams that are known to be impaired by various sources and causes of pollution (Bahls 1993). The biocriteria in Table 2 are valid only for samples collected during the summer field season (June 2 1 -September 21). The criteria in Table 2 distinguish among four levels of stress or impairment and three levels of aquatic life use support: (1) no impairment or only minor impairment (full support); (2) moderate impairment (partial support); and (3) severe impairment (nonsupport). These impairment levels correspond to excellent, good, fair, and poor biological integrity, respectively. Quality Assurance Several steps were taken to assure that the study results are accurate and reproducible. Upon receipt of the samples, station and sample attribute data were recorded in the Montana Diatom Database and the samples were assigned a unique number, e.g., 2008-02. The first part of this number (2008) designates the sampling site (Redwater River at Fairgrounds) and the second part (02) designates the number of periphyton samples that that have been collected at this site for which data have been entered into the Montana Diatom Database. Sample observations and analyses of soft (non-diatom) algae were recorded in a lab notebook along with information on the sample label. A portion of the raw sample was used to make duplicate diatom slides. The slide used for the diatom proportional count will be deposited in the Montana Diatom Collection at the University of Montana Herbarium (MONTU) in Missoula. The duplicate slide will be retained in Helena at the offices of Hannaea. Diatom proportional counts have been entered into the Montana Diatom Database. Results and Discussion Results are presented in Tables 3, 4, and 5, which are located near the end of this report following the references section. Appendix A consists of a series of diatom reports, one for each sample. Each diatom report contains an alphabetical list of diatom species and their percent abundances, and values for 65 different diatom metrics and ecological attributes (Table 6). Sample Notes All of the samples in this sample set, except the one collected from Nelson Creek, were septic, black in color, and smelled of rotten eggs (H2S). Decomposition of soft algae was not complete, however, allowing for identification of most specimens. Diatoms and blue-green algae (cyanobacteria) were more resistant to decay than green algae, which were the most problematic to identify. Most of the samples were silty to extremely silty, except for upper Horse Creek, Nelson Creek, and Redwater River at the Fairgrounds. Fine particulate organic matter (FPOM) was abundant in samples collected from the lower 3 Redwater River sites and from upper Sand Creek. The samples from upper Horse Creek, Nelson Creek, and Redwater River at Fairgrounds contained moss and/or macrophytes. Non-Diatom Algae (Table 3) McCone County streams supported 18 genera of non-diatom algae in 4 algal divisions (Table 3). Green algae and cyanobacteria were the most diverse and most abundant groups of non-diatom algae. Each site supported from 2 to 9 genera of non-diatom algae. Diatoms accounted for most of the biovolume in these samples except for the 3 Horse Creek sites and the lower site on Redwater River (Table 3). Filamentous cyanobacteria {Lyngbya and Oscillatoria) dominated at the upper 2 Horse Creek sites and the filamentous green alga Rhizodonium was the most abundant alga in samples from lower Horse Creek and the lower site on Redwater River. Rhizodonium has been reported to cause problems in standing and slowly flowing waters across the western United States (Wehr and Sheath 2003). Algae interfere with water uses — e.g., fishing, swimming, boating, and irrigation — only when standing crops are excessive. Mat-forming filamentous algae are normal components of many aquatic ecosystems, including prairie streams, and there is no evidence from this study that standing crops of Rhizodonium are excessive in these streams. Also, criteria have not been established for determining when algal growth in prairie streams is excessive. Cyanobacteria, many species of which can fix atmospheric nitrogen, were most common in Nelson Creek and the upper reaches of Horse Creek, Sand Creek, and the Redwater River. Nitrogen is most hkely the limiting nutrient at these sites. Cyanobacteria were absent from Prairie Elk Creek and lower Sand Creek. Algae in the division Euglenophyta {Euglena and Phacus) are known to be especially tolerant of organic pollution (Palmer 1969). These algae were found only in samples collected from the Redwater River below the airport and at Highway 13. The filamentous chrysophyte Tribonema is known to favor cool water temperatures. Tribonema was common in samples collected fi-om upper Horse Creek, Prairie Elk Creek, and lower Sand Creek. Diatoms (Table 4) Of the 12 major diatom species in McCone County streams, ovAy Achnanthidium mimitissimum is sensitive to organic pollution (class 3). A minutissimum was most abundant in Prairie Elk Creek and lower Sand Creek (Table 4). Eight of the major species are most tolerant of organic pollution (class 1). These species were abundant at all sites except the lower 2 sites on the Redwater River. The remaining 3 major species are somewhat tolerant of organic pollution and these (class 2) species were most abundant in lower Horse Creek and lower Redwater River (Table 4). Horse Creek. Diatom metrics indicate moderate organic loading at the upper and lower sites and severe organic loading at the middle site. Minor to moderate sedimentation was evident at the lower two sites (Table 4). Some sedimentation and internal organic loading may be natural in prairie streams. Diatom species richness, diversity, and equitability values were moderately low to extremely low at the two downstream sites. The cause of this low diversity is likely a combination of organic loading and excessive salinity. Some of the most common diatom species in Horse Creek tolerate elevated concentrations of dissolved solids. Nitrogen- fixing diatoms were abundant at the upper site on Horse Creek, indicating that nitrogen is likely the limiting nutrient here. The three Horse Creek stations had little in common floristically, indicating that major changes in environmental conditions occurred between the sites. Nelson Creek. Nelson Creek was dominated by 4 species of diatoms that are very tolerant of elevated organic loading and/or salinity. The pollution index indicates severe impairment from organic loading, which resulted in depressed diatom species richness and diversity. Sedimentation was only a minor problem in Nelson Creek. Nelson Creek supported a large percentage of nitrogen-fixing diatoms (Rhopalodiales), which indicates probable nitrogen limiting conditions. Prairie Elk Creek. Prairie Elk Creek (and the lower site on Sand Creek) had the best overall biological integrity of all the sites in this sample set. Diatom metrics indicate only minor impairment from organic loading and sedimentation. Diatom species richness and diversity values were somewhat depressed, but still within the range of minor impairment. This was the only site where the pollution sensitive diatom Achnanthidium minutissimum was a major species. Redwater River. Diatom metrics indicate severe organic loading and moderate sedimentation at the upper (Fairgrounds) site on the Redwater River (Table 4). This site was dominated by Navicula durrenbergiana, a motile diatom that tolerates elevated concentrations of organic nutrients and dissolved solids. Although diatom species richness and non-diatom genus richness were normal for a prairie stream, diatom diversity and equitability were low and indicate a moderate amount of stress. Two abnormal diatom cells were counted at this site. This is within the normal range for an unimpaired prairie stream. No abnormal cells were obser\'ed at the other 10 sites that were sampled for this project. The Cemetery Road and airport sites showed moderate stress from organic loading and sedimentation, respectively. The salinity tolerant species Navicula salinarum dominated the diatom assemblage at Cemetery Road, indicating that elevated dissolved solids were also a stressor here. This site shared about a third of its diatom assemblage with the upstream site, indicating that a moderate amount of environmental change occurred between the two sites. Nitzschia frustulum was the dominant diatom species at the airport site. This species is highly motile and tolerates elevated concentrations of both orsanic and inorganic nutrients. This site shared about a third of its diatom assemblage with the Cemetery Road site. Both the Cemetery Road and airport sites had normal diatom species richness and diversity for a prairie stream. At Highway 13, diatom metrics indicate severe impairment from sedimentation but only minor impairment from organic loading. Diatom species richness, diversity, and equitability were very low as a result of dominance by Nitzschia reversa. This is a facultative planktonic species and its abundance here indicates probable ponding and very low current velocities. The sedimentation inde.x is very high here because Nitzschia reversa belongs to the highly motile genus Nitzschia. This site shared only about one-fifth of its diatom assemblage with the next upstream site, indicating that a major environmental change occurred between the two sites. Sand Creek. Diatom metrics indicate severe impairment from organic loading at the upper site on Sand Creek. Several pollution tolerant species dominated the diatom assemblage at this site. Not all of these species are motile, however, and the sedimentation index indicates only minor impairment, both here and at the downstream site near the mouth. Although depressed, diatom species richness and diversity were within the normal range for a prairie stream. Along with Prairie Elk Creek, the lower site on Sand Creek had the best biological integrity of all sites in the sample set. Only minor impairment from sedimentation and organic loading was evident. This site supported the second largest percentage of the pollution sensitive species Achnanthidium minutissimum. Diatom species richness, diversity, and equitability were excellent and within the normal range for a prairie stream. This site shared less than one-third of its diatom assemblage with the upper site on Sand Creek, which indicates that a moderate amount of environmental change occurred between them. Modal Categories (Table 5) Several ecological attributes were selected from the diatom reports in the appendix and modal categories of these attributes were extracted to characterize water quality tendencies in streams of McCone County (Table 5). 10 Most diatoms at most of the sites were highly motile nitrogen autotrophs that tolerate moderate levels of organics and prefer brackish, eutrophic, and alkaline waters. The modal category for some of the attributes and sites was "not classified", which means that the ecological preferences of the diatoms that comprise the largest group have yet to be determined. Modal categories at some sites represent a significant improvement in water quality compared to other sites. For example, most diatoms in upper Horse Creek, upper Redwater River, and Sand Creek were ''moderately motile". At other sites, the modal category was "highly motile". At most sites, the modal category for salinity was "brackish", but it was "brackish- fresh" at the lowest site on Horse Creek, the next to last site on Redwater River (airport), and both sites on Sand Creek. Modal categories suggest possible inferior water quality conditions at the lower site on Horse Creek and the airport site on the Redwater River. Both sites supported a predominance of obligate nitrogen heterotrophs, as opposed to autotrophs at other sites. The modal category for oxygen demand was "moderate" at these sites, whereas the modal category was "fairly high" at other sites (Table 5). References APHA. 1998. Standard Methods for the Exanunation of Water and Wastewater. 20* Edition. American Pubhc Health Association, Washington, D.C. Bahls, L.L. 1979. Benthic diatom diversity as a measure of water quality. Proceedings of the Montana Academy of Sciences 38:1-6. Bahls, L.L. 1993. Penphyton Bioassessment Methods for Montana Streams (revised). Montana Department of Health and Environmental Sciences, Helena. Bahls, L.L. , Bob Bukantis, and Steve Tralles. 1992. Benchmark Biology of Montana Reference Streams. Montana Department of Health and Environmental Sciences, Helena. Barbour, M.T., J. Gerritsen, B.D. Snyder, and J.B. Stnbling. 1999. Rapid Bioassessment Protocols for Use In Streams and Wadeable Rivers: Penphyton, Benthic Macroinvertebrates and Fish. Second Edition. EPA/84 l-B-99-002. U.S. Environmental Protection Agency, Office of Water, Washington, D.C. Beaver, Janet. 1981. Apparent Ecological Characteristics of Some Common Freshwater Diatoms. Ontario Ministry of The Environment, Technical Support Section, Don Mills, Ontario. 11 Johansen, J.R. 1999. Diatoms of Aerial Habitats. Chapter 12 (>j Stoermer, E.F., and J.P. Smol (eds.). The Diatoms: Applications For the Environmental and Earth Sciences, Cambridge University Press, New York. John, D.M., B.A. Whitton, and A.J. Brook (eds.). 2002. The Freshwater Algal Flora of the British Isles: An Identification Guide to Freshwater and Terrestrial Algae. Cambridge University Karr, J.R., and D.R. Dudley 198 1 . Ecological perspectives on water quality goals. Environmental Management 5:55-69. Krammer, Kurt. 2002. Cymbellci. Volume 3 in Diatoms of Europe, Horst Lange-Bertalot, ed. A.R.G. Gantner Verlag K.G., Germany. Krammer, K., and H. Lange-Bertalot. 1986. BaciUariophyceae, Part 2, Volume 1: Naviculaceae. In Ettl, H., J Gerloff, H. Heynig, and D. Mollenhauer (eds.). Freshwater Flora of Middle Europe. Gustav Fischer Publisher, New York. Krammer, K., and H. Lange-Bertalot. 1988. BaciUariophyceae, Part 2, Volume 2: Bacillariaceae, Epithemiaceae, Surirellaceae. In Ettl, H., J. Gerloff, H. Heynig, and D. Mollenhauer (eds.), Freshwater Flora of Middle Europe. Gustav Fischer Publisher, New York. Krammer, K., and H. Lange-Bertalot. 1991a. BaciUariophyceae, Part 2, Volume 3: Centrales, Fragilariaceae, Eunotiaceae. In Ettl, H., J. Gerloff, H. Heynig, and D. Mollenhauer (eds.). Freshwater Flora of Middle Europe. Gustav Fischer Publisher, Stuttgart. Krammer, K., and H. Lange-Bertalot. 1991b. BaciUariophyceae, Part 2, Volume 4: Achnanthaceae, Cntical Supplement to Navicula (Lineolatae) and Gomphonema, Complete List of Literature for Volumes 1-4. In Ettl, H., G. Gartner, J. Gerloff, H. Heynig, and D. Mollenhauer (eds.). Freshwater Flora of Middle Europe. Gustav Fischer Publisher, Stuttgart. Lange-Bertalot, Horst. 1979. Pollution tolerance of diatoms as a criterion for water quality estimation. Nova Hedwigia 64:285-304. Lange-Bertalot, Horst. 1996. Rote Liste der limnischen Kieselalgen (BaciUariophyceae) Deutschlands. Schr.-R. f. Vegetationskde., H. 28, pp. 633-677. BfN, Bonn-Bad Godesberg. Lange-Bertalot, Horst. 2001. Navicula sensu stricto: 10 Genera Separated from Navicula sensu lata: Frustulia. Volume 2 in Diatoms of Europe, Horst Lange-Bertalot, ed. A.R.G. Gantner Verlag K.G., Germany. Lowe, R.L. 1974. Environmental Requirements and Pollution Tolerance of Freshwater Diatoms. EPA-670/4-74-005. U.S. Environmental Protection Agency, National Environmental Research Center, Office of Research and Development, Cincinnati, Ohio. McFarland, B.H., B.H. Hill, and W.T. Willingham. 1997. Abnormal Fragilarm spp. (BaciUariophyceae) In streams impacted by mine drainage. Journal of Freshwater Ecology 12(1): 141 -149. Morales, E.A., and Marina Potapova. 2000. Third NAWQA Workshop on Harmonization of Algal Taxonomy, May 2000. Patnck Center for Environmental Research, The Academy of Natural Sciences, Philadelphia. Palmer, CM. 1969. A composite rating of algae tolerating organic pollution. Journal of Phycology 5:78-82. Palmer, CM. 1977. Algae and Water Pollution: An Illustrated Manual on the Identification, Significance, and Control of Algae in Water Supplies and in Polluted Water. EPA-600/9-77-036. Plafkin, J.L., M.T. Barbour, K.D. Porter, S.K. Gross, and R.M. Hughes. 1989. Rapid Bioassessment Protocols for Use in Rivers and Streams: Benthic Macroinvertebrates and Fish. EPA 440-4-89-001. 12 Prescott, G.W. 1962. Algae of the Western Great Lakes Area. Wm. C. Brown Company, Dubuque, Iowa. Prescott, G.W. 1978. How to Know the Freshwater Algae. Third Edition. Wm. C. Brown Company Publishers, Dubuque, Iowa. Renfro, H.B., and D.E. Feray. 1972. Geological Highway Map of the Northern Rocky Mountain Region. American Association of Petroleum Geologists, Tulsa, Oklahoma. Smith, G.M. 1950. The Fresh-Water Algae of The United States. McGraw-Hill Book Company, New York. Stevenson, R.J., and Y. Pan. 1999. Assessing Environmental Conditions in Rivers and Streams with Diatoms. Chapter 2 in Stoermer, E.F., and J. P. Smol (eds.), The Diatoms: .A.pplications For the Environmental and Earth Sciences, Cambridge University Press, New York. Stewart, W.D.P., P. Rowell, and A.N. Rai. 1980. Symbiotic Nitrogen-Fixing Cyanobacteria. Pp. 239-277 in Stewart, W.D.P., and J. Gallo (eds.). Nitrogen Fixation, Academic Press, New York. USDA. 1976. Climax Vegetation of Montana (map). U.S. Department of Agriculture, Soil Conservation Service, Cartographic Unit, Portland. USEPA. 2000. Level III Ecoregions of the Continental United States (map). U.S. Environmental Protection Agency, Corvallis, Oregon. Van Dam, Herman, Adrienne Mertens, and Jos Sinkeldam. 1994. A coded checklist and ecological Indicator values of freshwater diatoms from The Netherlands. Netherlands Journal of Aquatic Ecology 28(1):1 17-133. Weber, C.I. (ed.). 1973. Biological Field and Laboratory VIethods for Measuring the Quality' of Surface Waters and Effluents. EPA-670/4-73-001. U.S. Environmental Protection Agency, National Environmental Research Center, Office of Research and Development, Cincinnati, Ohio. Wehr, J. D., and R.G. Sheath. 2003. Freshwater Algae of North America: Ecology and Classification. Academic Press, New York. Whittaker, R.H. 1952. A study of summer foliage insect commimities in the Great Smoky Mountains. Ecological Monographs 22:1-44. Woods, A.J., Omemik, J.M., Nesser, J.A., Shelden, J., and S.H. Azevedo. 1999. Ecoregions of Montana (color poster with map), U.S. Geological Survey, Reston, Virginia. 13 m 1 0) Q. 4-* E m « Q O) (U ■D 3 _*^ O) c o _l d> t: 3 *^ *•* ra _i CO ro CO O O O O O O (N CM CM CO O O c n o O 0) c o o o c o u5 en c "5. 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