Assessing recovery in a stream ecosystem: Applying multiple chemical and biological endpoints

Recovery dynamics in a previously disturbed stream undergoing remediation was assessed by measuring several chemical and biological endpoints. Three major trophic levels (periphyton, benthic macroinvertebrates, and fish communities) were analyzed along with various biological indicators of fish health including sub-organismal (biochemical and physiological) and individual-level responses. Ambient toxicity testing, water quality measurements, and fish bioaccumulation studies were also conducted to provide additional indicators of stream recovery. Information on chemical loading, biological exposure (bioaccumulation), and bioassays help identify the underlying or mechanistic basis of recovery, while endpoints measured on instream biota, and particularly those at higher levels of biological organization, are key responses for understanding the dynamics and ecological significance of recovery. When assessing recovery in aquatic ecosystems, it is important to conduct long-term field studies incorporating a variety of response variables that represent a wide range of sensitivities and response time scales. The value of different endpoints for assessing recovery depends on the inherent characteristics that are related to response variability and sensitivity, specificity and causal relationships to stressors, and ecological relevance. Long-term data sets incorporating a variety and range of these endpoints are needed to improve our understanding of natural variability in streams and provide a baseline against which effects of disturbance and subsequent recovery processes can be evaluated. The complexity of aquatic systems and their variable recovery dynamics suggest that no single measure is adequate for assessing aquatic ecosystem recovery and that a suite of chemical and biological endpoints is required for a more complete understanding of ecosystem dynamics and status during both the recovery and the post-disturbance periods. Such information should be valuable to environmental managers and regulators in helping to make more informed decisions regarding effective management and mitigation practices in disturbed systems.