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Incorporating Trophic Interactions into Biological Measures of Nutrient Enrichment in Support of Numerical Thresholds for Aquatic Life Use Attainment in Wadeable Streams

EPA Grant Number: FP916943
Title: Incorporating Trophic Interactions into Biological Measures of Nutrient Enrichment in Support of Numerical Thresholds for Aquatic Life Use Attainment in Wadeable Streams
Investigators: Taylor, Jason M.
Institution: Baylor University
EPA Project Officer: Just, Theodore J.
Project Period: September 1, 2008 through September 1, 2011
RFA: STAR Graduate Fellowships (2008)
Research Category: Academic Fellowships

Description:

Objective:

Analysis of trophic interactions in food webs provides a potential tool for identifying and quantifying cumulative direct and indirect effects of environmental stress, such as nutrient enrichment, on aquatic ecosystems. However, more empirical research that blends descriptive and experimental studies is needed for predicting the response of food web dynamics and ecosystem processes to changing abiotic and biotic factors. The objectives of this project are to: 1) estimate the effects of key benthic fish species in controlling periphyton response to nutrient enrichment and 2) evaluate the importance of trophic interactions among species as determinants of aquatic community structure in response to nutrient enrichment.

Approach:

This project will use a combination of field and mesocosm experiments coupled with observational studies to address objectives one and two. First, a series of field and stream mesocosm experiments where benthic fish densities (Etheostoma spectabile and Campostoma anomalum) and nutrient levels are manipulated will be employed to examine the effects of benthic fish on periphyton response to P enrichment. Several periphyton structural and functional attributes will be measured as response variables to fish and nutrient treatments. Second, riffle habitats from multiple streams spanning a steep phosphorus gradient will be sampled for fish and macroinvertebrates and six community-wide metrics based on δ13C-δ15N biplot space that measure aspects of trophic diversity and redundancy will be calculated for each stream. The potential of these metrics to serve as sensitive indicators of functional shifts along phosphorus enrichment gradients as well as provide important explanatory variables for describing the influence of biotic interactions in structuring communities will be evaluated.

Expected Results:

This research will contribute to understanding the effects of top down control and trophic cascades initiated by benthic fish on nutrients-periphyton relationships. Additionally, community-wide trophic metrics may provide a relationship that links ecosystem function to nutrient impairment in wadeable streams and provide insight into how stream communities respond to environmental stress through biotic interactions. These results will be incorporated into ecological thresholds for the development of defensible, numerical nutrient criteria for streams.

Supplemental Keywords:

trophic interactions, nutrient enrichment, nutrient criteria, indicators, top down control, trophic cascade, streams, fish, macroinvertebrates,

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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