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THE STRESSOR IDENTIFICATION GUIDANCE DOCUMENT
Citation:
CORMIER, S. M., S. B. NORTON, G. W. SUTER, AND W. SWIETLIK. THE STRESSOR IDENTIFICATION GUIDANCE DOCUMENT. Presented at EPA GOAL 2 BOSC Review, Cincinnati, OH, January 23 - 25, 2006.
Description:
THE STRESSOR IDENTIFICATION GUIDANCE DOCUMENT
Susan M. Cormier, ORD/NRMRL, Susan B. Norton, ORD/NCEA, Glenn W. Suter, II ORD/NCEA, William Swietlik, OW lOST
Science Question(s):
MYP Science Question: How can multiple and possibly related causes of biological impairment be inferred from indicator and other observations, and cause-effect modeling? For habitat alteration? For nutrients? For suspended and bedded sediments? For pathogens? For toxic chemicals?
Research Question: How can causes of biological impairments be identified, so that the right pollutant is reduced and ecosystems are remediated?
The Research: The EPA and others were reluctant to use biological surveys and biocriteria to drive permitting, remediation or restoration, because, unlike stressor specific criteria, the cause of the observed impairments were often unknown. This practical problem was solved by synthesizing approaches from different intellectual fields into a novel, defensible and useful methodology that identifies the probable cause or causes of undesirable biological conditions.
The Clean Water Act (CWA) requires that states, tribes, and territories adopt water quality standards that support designated uses including aquatic life use. These entities often measure a waterbody's ability to support aquatic life by sampling fish, invertebrates, and plants. If the measurements of biological assemblages deviate from expected norms, the waterbody may be listed as impaired. If a waterbody is listed as impaired, Section 303(d) of the CWA requires states and tribes to determine the cause of the biological impairment, to calculate a level of the causal pollutant that would allow the biological condition to return to acceptable levels, and to prepare an implementation plan to achieve these objectives. A defensible process for determining cause is especially needed by resource managers when the cause is not readily apparent, or when it is necessary to convince skeptical stakeholders.
To meet that need, ORD and OW staff collaborated to develop a logical, scientific process to evaluate available information for identifying the stressors that are most likely causing biological impairments. Rather than claiming to prove causation, we provided a clear and consistent method to identify and compare candidate causes and determine which is best supported by the evidence. The process uses a series ofthree methods. First, candidate causes that are not logically possible given the evidence are eliminated. Then, conventional medical/veterinary diagnostic approaches are used to identify any causal agents that have produced characteristic symptoms. For the remaining causes, a strength-of-evidence analysis is used to evaluate and score all available evidence for each candidate. The types of evidence are conceptually based on epidemiological criteria that have been customized for ecological investigations. To ensure transparency and defensibility, we encourage users to document all aspects ofthe analysis, types of evidence and inferences.
Impacts and Outcomes:
The Stressor Identification Guidance Document was published in 2000. Since then it has provided the basis for outreach to scientists in the regions, states and tribes. Training workshops have reached 47 states and 26 tribes. One example is the National Bioassessment and Biocriteria Workshop in Coeur D' Alene, Idaho. The 200 attendees participated in hands-on training, and state resource managers shared their own experiences during the sessions. The workshops also helped create networks of people who share similar challenges. Special sessions and courses have been offered at EPA Regional Biologists meetings in Regions 1,3,6 and 10, at the Society of Environmental and Toxicology and Chemistry meetings in November 2001,2004, and 2005, and the North American Benthological Society meeting in June 2004.
What is most noteworthy is that the method is being actively applied by several states, and has resulted in improved water quality. For example, the method was applied by the Connecticut Department of Environmental Protection on the Willimantic River, Connecticut. Working with the US EPA scientists, the cause of biological impairment was determined to be a effluent trom an illicit discharge, was corrected, and the biological diversity increased and now meets state biological criteria. The stream was removed from the 303d list. A workshop held in May 2005 brought together five additional case studies that have been completed or are well underway: the Touchet River, Washington; Bogue Homo Mississippi; the Floyd River, Iowa; the Coal River, West Virginia; and Long Creek, Maine. Additional workshops have been conducted for state scientists in New Jersey and Minnesota. New Mexico and other states have independently applied the approach. Other federal agencies have used or have proposed using the method.
The method has also provided a foundation for advancing the field of causal analysis. It is being adapted for application in estuaries and terrestrial systems, including studies outside the U.S. Examples, analytical tools, and a step-by-step guide to the method are being developed as part of the Causal Analysis/Diagnosis Decision Information System (CADDIS)-see accompanying poster.