Biological indicators of nutrient enrichment across Kentucky bioregions

L.A. Panayotoff, E.P. Akers, and J.F. Brumley.Kentucky Division of Water, Frankfort, Kentucky, USA 40601

Kentucky Division of Water (KDOW) is developing numeric nutrient criteria for wadeable streams using effects-based approaches. Diatom and macroinvertebrate data are being examined to assess the potential for assemblage attributes to identify levels of nutrients protective of aquatic life use. Existing data gathered from 1982-2005 were examined to identify possible criteria for TN, TP and Nitrate-Nitrite. Numerous diatom and macroinvertebrate metrics were screened for responses to nutrients, and relationships were examined for both linear and threshold responses. Bioregions differed substantially in the strength of biological responses to nutrients, making it evident that different approaches may be required for the 4 Kentucky bioregions. The Pennyroyal bioregion showed the clearest relationships between biological attributes and nutrients, with different approaches pointing to a similar range of nutrient levels above which undesirable effects are likely.