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An exploratory analysis of Indiana and Illinois biotic assemblage data in support of state nutrient criteria development
Citation:
Angradi, T. An exploratory analysis of Indiana and Illinois biotic assemblage data in support of state nutrient criteria development. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R/13/009, 2013.
Impact/Purpose:
The purpose of this report was to conduct exploratory analyses of state datasets from Illinois and Indiana to determine threshold values for nutrients and chlorophyll a that could guide Indiana and Illinois criteria development.
Description:
EPA recognizes the importance of nutrient criteria in protecting designated uses from eutrophication effects associated with elevated phosphorus and nitrogen in streams and has worked with states over the past 12 years to assist them in developing nutrient criteria. Towards that end, EPA has provided states and tribes with technical guidance to assess nutrient impacts and to develop criteria. EPA published recommendations in 2000 on scientifically defensible empirical approaches for setting numeric criteria. EPA also published eco-regional criteria recommendations in 2000-2001 based on a frequency distribution approach meant to approximate reference condition concentrations. In 2010, EPA elaborated on one of these empirical approaches (i.e., stressor-response relationships) for developing nutrient criteria. The purpose of this report was to conduct exploratory analyses of state datasets from Illinois and Indiana to determine threshold values for nutrients and chlorophyll a that could guide Indiana and Illinois criteria development. Box and whisker plots were used to compare nutrient and chlorophyll a concentrations between Illinois and Indiana. Stressor response analyses, using piece-wise linear regression and change-point analysis (Illinois only) were conducted to determine thresholds of change in relationships between nutrients and biotic assemblages. Impact stmt: The purpose of this report was to conduct exploratory analyses of state datasets from Illinois and Indiana to determine threshold values for nutrients and chlorophyll a that could guide Indiana and Illinois criteria development.