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Uses of Data
Biocriteria Links
Identify Stressors to a Waterbody
Biological assessment data help identify causes and sources of an impact to an aquatic community. With this knowledge, cost-effective priorities for restoration can be set that will focus on the most important causes of degradation. Biological assessments and criteria are useful in evaluating highly variable or diffuse sources of pollution such as storm water runoff. These types of non-point source pollution do not lend themselves well to traditional chemical water quality monitoring. A biological assessment of their cumulative impact will effectively evaluate these discharges and the success of the control actions.
For example, bioassessments have been successfully used in Florida to assess the cumulative impacts of multiple pollution sources within a watershed, in particular, storm water runoff and other non-point discharges. The Florida Stormwater/Non-Point Source Bioassessment Projects have found that bioassessments, over time, help reflect impacts from the fluctuating environmental conditions and highly variable pollutant inputs of wet weather discharges. Bioassessments were also identified by key storm water experts from across the nation as an important environmental indicator tool for assessing the impacts of storm water runoff and the effectiveness of storm water management strategies.
When attempting to identify the specific sources of use impairment (stressors), the role that biological assessments and biological criteria will play needs to be carefully defined. Stressor impact assessments based solely on biological information may be straightforward in certain waterbodies where a single source is the cause of impairment. In these cases, paired bioassessments, conducted above and below the discharge point, or in the vicinity of the source, may readily identify the degree of impairment and the efficacy of chosen control strategies. In small urban watersheds, dominated by storm water runoff, bioassessments and biocriteria may provide a direct means to measure and control the storm water impacts.
However, in complex waterbodies, where numerous sources contribute to the observed biological impairment, it may be difficult for bioassessments to distinguish the relative degrees of impairment from each contributing source.
Given these situations, EPA is developing a stressor identification process (SI) that utilizes all pertinent information (i.e., physical, chemical, and biological). This will provide watershed managers the scientific guidance for determining the causes of biological impairments to aquatic ecosystems and for presenting cogent scientific evidence for the causes.
Case Studies showing how bioassessment data has been used to identify causes and sources of impairment.
Stressor Identification Guidance leading water resource managers through a rigorous process to identify stressors that cause biological impairment in aquatic ecosystems and to assemble cogent scientific evidence that supports conclusions about potential causes. (December 2000) (EPA-822-B-00-025)