CADDIS Volume 3: Examples & Applications
Case Studies
These reports provide examples of how some assessors have developed and interpreted evidence to determine causes of biological impairments, and in some cases improved the quality of an ecosystem. They provide different examples of how to organize an assessment report, analyze data, and present results. Most of the cases assess rivers and streams, but a few assess terrestrial ecosystems.
The process for identifying causes of biological impairments continues to improve. As a result you will note differences among the case studies. In some examples, comments have been inserted by the U.S. EPA editor or the authors. These comments are not meant to indicate that these causal analyses are in error, but to assist other SI users by suggesting alternative approaches that may be applied to their cases.
Click on a location to view details about its case study.
Arkansas River, CO
This brief synopsis illustrates the use of several lines of evidence to support the hypothesis that heavy metal exposure impairs benthic macroinvertebrate communities.
Effect: Altered benthic invertebrate assemblage
Sources: Mining wastes
Probable causes: Mixed metals
Report: Arkansas River Case Study: Using Strength of Evidence Analysis. p. 4-11 in U.S. EPA (2000) Stressor Identification Guidance Document. U.S. Environmental Protection Agency, Washington DC. EPA/822/B-00/025.
Guidance, presentations, other: Clements WH (1994) Benthic invertebrate community responses to heavy metals in the Upper Arkansas River Basin, Colorado. Journal of the North American Benthological Society 13:30-44.
Clements WH, Kiffney PM (1994) Integrated laboratory and field approach for assessing impacts of heavy metals at the Arkansas River, Colorado. Environmental Toxicology and Chemistry 13:397-404.
Clements WH, Carlisle DM, Lazorchak JM, Johnson PC (2000) Heavy metals structure benthic communities in Colorado mountain streams. Ecological Applications 10:626-638.
Kiffney PM, Clements WH (1994) Structural responses of benthic macroinvertebrate communities from different stream orders to zinc. Environmental Toxicology and Chemistry 13:389-395.
Kiffney PM, Clements WH (1994) Effects of heavy metals on a macroinvertebrate assemblage from a Rocky Mountain stream in experimental microcosms. Journal of the North American Benthological Society 13:511-523.
Nelson SM, Roline RA (1996) Recovery of a stream macroinvertebrate community from mine drainage disturbance. Hydrobiologia 339:73-84.
Willimantic River, CT
A screening assessment from a one-day workshop led to additional sampling in which an illicit toxic source was found. Remediation led to improved aquatic life. The experience led the State to develop a causal assessment program, which in turn, led the State to address the effects of impervious surfaces on stream condition.
Effect: Altered benthic invertebrate assemblage
Sources: Impervious surfaces, upstream impoundments, concrete channels, waste water treatment facility, industrial outfalls
Probable causes: Primarily a toxic effluent; secondarily sediment, altered food resource, increased temperature
Report: Bellucci C, Hoffman G, Cormier S (2009) An Iterative Approach for Identifying the Causes of Reduced Benthic Macroinvertebrate Diversity in the Willimantic River, Connecticut. U.S. Environmental Protection Agency, Cincinnati, OH. EPA/600/R-08/144.
TMDL: CTDEP (2001) Total Maximum Daily Load Analysis for the Upper Willimantic River (PDF) (16 pp, 382K, About PDF). Connecticut Department of Environmental Protection, Stafford CT.
Little Floyd River, IA
This case study is a realistic example of the difficulties of assigning specific cause to biological impairment. It demonstrates several strategic techniques to use when data are collected in different years, when the discrimination between acceptable streams and impaired streams is small, and when multiple stressors affect a stream’s biological condition.
Effect: Altered fish and benthic Invertebrate assemblages and a fish kill
Sources: Row crop agriculture, hog production, wastewater treatment facility
Probable causes: Primarily substrate alteration; secondarily nutrient enrichment and episodic toxic ammonia concentrations
Manuscript: Haake DM, Wilton T, Krier K, Stewart AJ, Cormier SM (2010) Causal assessment of biological impairment in the Little Floyd River, Iowa, USA. Human and Ecological Risk Assessment 16(1):116-148.
Report: Haake D, Wilton T, Krier K, Isenhart T, Paul J, Stewart A, Cormier S (2008) Stressor Identification in an Agricultural Watershed: Little Floyd River, Iowa. U.S. Environmental Protection Agency, Cincinnati, OH. EPA/600/R 08/131.
TMDL: IA DNR (2005) Total Maximum Daily Load For Sediment and Dissolved Oxygen, Little Floyd River, Sioux and O’Brien Counties, Iowa (PDF) (32 pp, 378K, About PDF)
Long Creek, ME
This very detailed assessment illustrates the complexity of urban systems that are affected by many causes.
Effect: Altered benthic invertebrate assemblage, extirpated brook trout fishery
Sources: Commercial and industrial area, airport, dairy
Probable causes: Decreased dissolved oxygen, altered flow regime, decreased large woody debris, increased temperature, and increased toxicity due to ionic strength
Report: U.S. EPA (2007) Causal Analysis of Biological Impairment in Long Creek, a Sandy-Bottomed Stream in Coastal Southern Maine (Final Report). U.S. Environmental Protection Agency, Washington DC. EPA/600/R-06/065F.
Presumpscot River, ME
This is one of first two Stressor Identification case studies. The study was performed by the State of Maine prior to the development of the SI Guidance, and it informed the development of the SI Guidance. The weight of evidence was heavily influenced by the lack of co-occurrence of the effect with other candidate causes and by manipulations at a pulp mill on the Androscoggin River, in which reductions in total suspended solids led to recovery.
Effect: Altered benthic invertebrate assemblage
Sources: Impoundment, paper and pulp mill
Probable cause: Total suspended solids with floc
Report: Presumpscot River, Maine. Ch. 6 in U.S. EPA (2000) Stressor Identification Guidance Document. U.S. Environmental Protection Agency, Washington DC. EPA/822/B-00/025.
TMDL: U.S. EPA (1998) New Englands’s Review of the Presumpscott River TMDL - Memo (PDF) (12 pp, 14.1MB, About PDF)
Guidance, presentations, other: Presumpscot River Plan Steering Committee (2002) Cumulative Impacts to Environmental Conditions on the Presumpscot River and its Shorelands (DRAFT – As distributed at the June 2002 Public Meetings) (PDF) (102 pp, 1.3MB, About PDF)
Groundhouse River, MN
This screening assessment was done during a two-and-a-half day workshop. Findings were used to mount a more extensive watershed-scale assessment with additional data collection. Results of the screening assessment were confirmed and additional causes were characterized. The State adopted the SI process and developed their own guidance and training materials.
Effect: Altered benthic invertebrate assemblage
Sources: Waste water treatment facility, agriculture
Probable causes: Sediment, nutrients
Report: Lane C, Cormier S (2004) Screening Level Causal Analysis and Assessment of an Impaired Reach of the Groundhouse River, Minnesota. U.S. Environmental Protection Agency, Cincinnati OH.
TMDL: Minnesota Pollution Control Agency (2009) Groundhouse River Total Maximum Daily Loads for Fecal Coliform and Biota (Sediment) Impairments (PDF) (377 pp, 9.3MB, About PDF)
Guidance, presentations, other: Jasperson J (2008) Biota TMDL Protocols and Submittal Requirements (PDF) (124 pp, 1.9MB, About PDF)
Minnesota Pollution Control Agency (2009) Setting the Course for Improved Water Quality – Tackling a Biological Impairment: The Groundhouse River TMDL Study Case Example (PDF) (47 pp, 987K, About PDF)
Bogue Homo, MS
This assessment was one of the first cases undertaken by the State that led to a streamlined process to perform more than 700 court-ordered causal assessments required for total maximum daily load (TMDL) development. A standard list of candidate causes and screening levels developed at the beginning of the program increased the speed of the assessments.
Effect: Altered benthic invertebrate assemblage
Sources: Forestry, agriculture, reservoir
Probable causes: Primarily dissolved oxygen (DO) and altered food resources
Report: Hicks M, Whittington K, Thomas J, Kurtz J, Stewart A, Suter GW II, Cormier S (2010) Causal Assessment of Biological Impairment in the Bogue Homo River, Mississippi Using the U.S. EPA's Stressor Identification Methodology. U.S. Environmental Protection Agency, Cincinnati OH. EPA/600/R-08/143.
TMDL: MDEQ (2005) Phase 1: Total Maximum Daily Load Biological Impairment Due to Organic Enrichment/Low Dissolved Oxygen and Nutrients: The Bogue Homo River, Pascagoula Basin, Jones County, Mississippi (PDF) (44 pp, 681K, About PDF). Mississippi Department of Environmental Quality, Office of Pollution Control, Jackson MS.
Guidance, presentations, other: MDEQ (2004) Draft Stressor Identification for the Bogue Homo River, Forrest and Perry Counties, Mississippi. Mississippi Department of Environmental Quality, Office of Pollution Control, Jackson MS.
Little Scioto River, OH
This is one of the first two Stressor Identification case studies. In addition to the original case, alternate formats for organizing data are presented in CADDIS.
Effects: Altered fish and benthic invertebrate assemblages
Sources: Channelized stream, creosote plant and treatment facility, industrial waste site, waste water treatment facilities
Probable causes: Altered habitat, PAHs, metal and ammonia toxicity in different segments
Manuscripts: Norton SB, Cormier SM, Suter GW II, Subramanian B, Lin ELC, Altfater D, Counts B (2002) Determining probable causes of ecological impairment in the Little Scioto River, Ohio, USA. Part 1: Listing candidate causes and analyzing evidence. Environmental Toxicology and Chemistry 21(6):1112-1124.
Cormier SM, Norton SB, Suter GW II, Altfater D, Counts B (2002) Determining the causes of impairments in the Little Scioto River, Ohio. Part 2: Characterization of causes. Environmental Toxicology and Chemistry 21(6):1125-1137.
Report: Little Scioto River, Ohio. Ch. 7 in U.S. EPA (2000) Stressor Identification Guidance Document. U.S. Environmental Protection Agency, Washington DC. EPA/822/B-00/025.
Guidance, presentations, other: Ohio EPA (2008) Biological and Water Quality Study of the Little Scioto River. Ohio Environmental Protection Agency, Columbus OH. pp. 59. [accessed 02/02/10]
Touchet River, WA
This screening causal assessment is the first application of the Stressor Identification (SI) process to a long stretch of river, to the northwestern U.S., to an arid watershed, and to endangered salmonids. Specific alteration of the invertebrate assemblage aided analysis.
Effect: Altered benthic invertebrate assemblages and extirpation of salmonids
Sources: Wheat and irrigated agriculture, impoundments, logging, cattle raising
Probable causes: Primarily water temperature and sedimentation; secondarily toxics, low dissolved oxygen (DO), alkaline pH, reduced detritus, reduced flow, and reduced habitat complexity
Manuscript: Wiseman CD, LeMoine M, Cormier S (2010) Assessment of probable causes of reduced aquatic life in the Touchet River, Washington, USA. Human and Ecological Risk Assessment 16(1):87-115.
Report: Wiseman CD, LeMoine M, Plotnikoff R, Diamond J, Stewart A, Cormier S (2009) Identification of Most Probable Stressors to Aquatic Life in the Touchet River, Washington. U.S. Environmental Protection Agency, Cincinnati OH. EPA/600/R 08/145.
TMDL: Washington Department of Ecology. Walla Walla Watershed Water Quality Improvement Project
Guidance, presentations, other: Adams K (2010) Guidance for Stressor Identification of Biologically Impaired Aquatic Resources in Washington State
Lake Washington, WA
This is a brief synopsis of a historically important causal assessment of a eutrophic system. Evidence of world-wide consistency of association established general causality and modeling was important in the specific case.
Effect: Cyanobacteria blooms
Sources: Waste water inputs
Probable causes: Phosphorus
Report: Lake Washington Case Study. p. 4-13 in U.S. EPA (2000) Stressor Identification Guidance Document. U.S. Environmental Protection Agency, Washington DC. EPA/822/B-00/025.
Guidance, presentations, other: Summarized from Lehman JT (1986) Control of eutrophication in Lake Washington: case study. pp. 301-316 in Ecological Nnowledge and Environmental Problem-Solving: Concepts and Case Studies. National Academy Press, Washington DC.
Clear Fork Watershed, WV
This relatively data-rich case adresses a moderately sized drainage with several tributaries. Stressor-response relationships derived from field data prior to the assessment provided the primary evidence.
Effect: Altered benthic invertebrate assemblage
Sources: Mining, logging, agriculture, and residential development.
Probable causes: Sulfate/conductivity, organic and nutrient enrichment, acid mine drainage, residual metals (particularly aluminum) at moderately acidic pH, excess sediment, and multiple stressors
Report: Gerritsen J, Zheng L, Burton J, Boschen C, Wilkes S, Ludwig J, Cormier S (2010) Inferring Causes of Biological Impairment in the Clear Fork Watershed, West Virginia. U.S. Environmental Protection Agency, Office of Research and Development, National Center for Environmental Assessment, Cincinnati OH. EPA/600/R-08/146.
TMDL: WVDEP (2006) Appendix 1. Clear Fork in Total Maximum Daily Loads for Selected Streams in the Coal River Watershed, West Virginia (PDF) (14 pp, 327K, About PDF)
Guidance, presentations, other: WVDEP (1997) An Ecological Assessment of the Coal River Watershed. West Virginia Department of Environmental Protection, Division of Water Resources, Watershed Assessment Program. Report number - 5050009 – 1997. pp. 93.
Elk Hills, CA (terrestrial)
This relatively data-rich case study deals with a contaminated terrestrial site and an endangered wildlife population. It reverses the findings of a prior assessment by using mathematical modeling that links causes with population change and illustrates the importance of spatial and temporal scales of causes and effects.
Effect: Decline in abundance of the endangered San Joaquin Kit Fox
Sources: Petroleum drilling, wastes, vehicles, and drought
Probable causes: Predation and accidents
Report: U.S. EPA (2008) Analysis of the Causes of a Decline in the San Joaquin Kit Fox Population on the Elk Hills, Naval Petroleum Reserve #1, California. U.S. Environmental Protection Agency, Cincinnati OH. EPA/600/R-08/130.
Upper Arkansas River, CO (terrestrial)
This case study applied the Stressor Identification (SI) process at a terrestrial contaminated site, the highly mineralized area of the Colorado Rocky Mountains, to shed light on its utility in such an environment. Impairments evaluated were reduced vegetation (barren areas in the floodplain) and reduced plant growth and species richness in meadows irrigated with water from the Upper Arkansas River. Aspects of the assessment process that may differ between aquatic and terrestrial systems include the critical variables that are measured, degree of development of bioassessment criteria, spatial heterogeneity and linearity of physicochemical factors, and management practices.
Effect: Reduced plant growth and plant species richness
Sources: Mining, smelting, agriculture
Probable causes: Extrinsic metal with decreased pH (floodplain); extrinsic metal (irrigated meadows)
Report: Kravitz M (2011) Stressor Identification (SI) at Contaminated Sites: Upper Arkansas River, Colorado. U.S. Environmental Protection Agency, Cincinnati OH. EPA/600/R-08/029.
Birds of prey (terrestrial)
This brief synopsis of a historically important causal assessment explains that the link between DDT and peregrine falcon decline was not initially recognized. Ultimately, the connection was made by re-examining the description of the impairment and recognizing that the specific effect was reproductive failure due to eggshell thinning.
Effect: Decline of birds of prey
Probable causes: DDT/DDE
Report: Revisiting the Impairment in the Case of DDT. p. 5-2 in U.S. EPA (2000) Stressor Identification Guidance Document. U.S. Environmental Protection Agency, Washington DC. EPA/822/B-00/025.
Guidance, presentations, other: Blus LJ, Henny CF (1997) Field studies on pesticides and birds: unexpected and unique relations. Ecological Applications 7:1125-1132.
Grier JW (1982) Ban of DDT and subsequent recovery of reproduction in bald eagles. Science 218:1232-1234.