Climate change is projected to affect aquatic ecosystems through changes in water temperature, hydrological cycles, and degree days. These effects will manifest themselves through changes in community composition, phenology, number of reproductive cycles, evolutionary adaptations, and genetic selection. These changes also serve as indicators of climate change effects on ecosystems and could be used to document ecosystem condition. State and tribal water quality agencies use biological indicators to assess ecosystem condition as required by the Clean Water Act. These assessments rely on comparisons of reference and non-reference sites. Climate change, however, will affect organisms at both types of sites, unlike traditional stressors. Therefore, understanding how biological indicators respond to the effects of climate change, what novel indicators may be available to detect effects, how well current sampling schemes may detect climate-driven changes, and how likely it is that current sampling schemes will continue to detect impairment, are important issues in need of discussion. This report is meant to initiate this discussion by providing information on the potential effects of climate change on biological indicators, outlining initial strategies to modify assessment activities to account for climate change effects, and highlighting possible next steps.

"EPA/600/R-07/085." "March 2008." Title from title screen (viewed Sept 17, 2008).

The Clean Water Act mandates that states assess the biological, chemical, and physical condition of their aquatic resources using biological indicators that compare reference and non-reference sites to measure condition. The Office of Water developed guidance documents for establishing biocriteria in rivers and streams, lakes, estuaries, and wetlands, and is developing biocriteria for coral reefs. Climate change is projected to affect aquatic ecosystems through changes in water temperature, hydrological cycles, and degree days. This report is a preliminary analysis of how biological indicators are likely to respond to climate change, how well current sampling schemes may detect climate-driven changes, and how likely it is that these sampling schemes will continue to detect impairment. The results and recommendations are an initial step towards helping biocriteria programs modify assessment activities to account for climate change effects and ensure that management goals continue to be met.