Diatoms for Evaluating Excess Nutrient Conditions
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Indicators of biological condition based on primary producers have been developed and applied at local, regional, and national scales with relationships among these indicators, human disturbance, and water quality. Diatoms are an important primary producer in aquatic ecosystems and can be useful as biological indicators of changing nutrient concentrations, which are reflective of changes in nutrient loading. An advantage of diatoms is that they usually respond more rapidly to changes in water quality and can provide finer resolution (species-level) understanding of nutrient condition compared to other indicators, such as benthic chlorophyll a and macroinvertebrates. Several states in the US have used or are developing diatom-based tools to inform selection of numeric nutrient criteria and assessment thresholds. In this talk, we will discuss how diatoms can be used to understand water quality, provide an overview of the data Ohio EPA has been collecting over the last decade and how diatoms may be useful in cases with higher unexplained variation, and follow with results of a pilot study in Central Ohio where simultaneous measurement of diatoms and phosphorus was used to characterize nutrient condition status on Raccoon Creek along a stream reach with mixed point and non-point nutrient sources.