Ecoregion-specific Comparison of Stream Community Responses to Nutrient Gradients Using Both Survey and Experimental ApproachesEPA Grant Number: R824783
Title: Ecoregion-specific Comparison of Stream Community Responses to Nutrient Gradients Using Both Survey and Experimental Approaches
Investigators: Stevenson, R. Jan , Holomuzki, Joe , Wiley, Michael J.
Institution: University of Michigan , Transylvania University , University of Louisville
EPA Project Officer: Hiscock, Michael
Project Period: October 1, 1995 through September 1, 1998
Project Amount: $390,000
RFA: Water and Watersheds (1995) Recipients Lists
Research Category: Water and Watersheds , Water
Description:Nutrient loading commonly causes an increase in primary productivity and a replacement of oligotrophic algal-invertebrate communities with a new suite of organisms that result in very different stream structure and function, Quantitatively assessing the relationships between nutrient concentrations and algal-invertebrate communities in streams has been challenging because stream ecosystems are so physically variable and biologically dynamic. The proposed research is designed to develop a better predictive understanding of nutrient effects on stream communities in ecoregions with different hydrological stability.
Stream surveys with large within-ecoregion sample sizes, experiments, and analyses of large databases have been started with the objectives: (1) to access, quantitatively, variation in algal and invertebrate communities to different nutrient concentrations by sampling 140 streams in two hydrologically different ecoregions, one in Kentucky and one in Michigan; (2) to assess, experimentally, the cause-effect relationships between changes in stream communities and nutrient concentrations; (3) to develop algal and invertebrate indicators that infer specific nutrient conditions and that infer susceptibility of communities to change (i.e., arsinihative capacity); and 4) to test and revise the KY and MI ecoregion-specific indicators of nutrient conditions and effects with databases developed by the EMAP-SW Streams Program and by other stream surveys. Initial results of surveying 29 streams in Kentucky and 40 streams in Michigan indicate that chances for high accrual of algae with increasing nutrients is greater in the hydrologically variable streams of Kentucky than in the stable streams of Michigan. The surveys also show that low invertebrate abundances in Kentucky do not respond to nutrients, but that the high invertebrate abundances in Michigan do show a positive response to nutrients. Experiments show that invertebrate fitness positively responds to the range of nutrient conditions observed in the surveyed streams. Analysis of algal data from the EMAP-SW Stream Program shows that algal species composition responds to changes in nutrients, so that development of reliable biological indicators of the highly variable nutrient concentrations in streams is possible.