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Quantifying Periphyton Community Responses to Nutrients in a Southeast Coastal Plain Watershed using a Molecular Approach
Citation:
Hagy, Jim, R. Devereux, S. Friedman, D. Beddick, AND K. Houghton. Quantifying Periphyton Community Responses to Nutrients in a Southeast Coastal Plain Watershed using a Molecular Approach. Eastern Numeric Nutrient Criteria Workshop, Atlanta, Georgia, April 24 - 26, 2018.
Impact/Purpose:
This poster presents results obtained from a research project entitled “Water Quality and Aquatic Life Responses to Implementation of Best Management Practices in Gulf of Mexico Initiative Focus Watersheds.” The project was partially supported as a Regional Applied Research Effort (RARE) by US EPA Region 4 as well as the Safe and Sustainable Water Research Program, Project 4.02, Task A, “Improved Nutrient Indicator Development.” The objectives of this study were to develop new sensitive and nutrient-specific periphyton indicators of water quality using a molecular approach based on analysis of DNA sequences from stream periphyton. The research should be of interest to scientists and water quality managers interested in methods for evaluating biotic condition in streams, specifically in relation to nutrient pollution
Description:
Nutrient (nitrogen and phosphorus) pollution is a water quality issue in the US, including within the southeastern states that comprise US EPA Region 4. Biotic condition of southeastern streams with respect to nutrients has been evaluated using biological indicators based on macroinvertebrates or periphyton communities, particularly diatoms. The goals of this study were to expand and improve the nutrient specificity of periphyton indicators using a molecular approach based on analysis of 16S and 18S ribosomal RNA gene sequences. Although molecular methods can be used to identify thousands of taxa in stream periphyton communities, using this information to establish nutrient indicators is limited by a relative lack of information about nutrient responses for many taxa. We examined these responses by deploying nutrient-diffusing substrate experiments in two southeastern streams spanning a range of anthropogenic effects resulting from agricultural land-use in the catchment. Treatments included controls, +N amendments, +P amendments, and +N and P amendments. Periphyton communities that became established on the deployed substrates differed significantly by site, date or season, and nutrient treatment, with better-resolved community differences among prokaryotes compared to eukaryotes. Effects of nutrient amendments were more pronounced at the less nutrient impacted site compared to the agriculture-dominated site. Nutrient amendments decreased species richness and diversity to varying degrees at both sites. Analysis of taxa most contributing to community differences associated with nutrients identified a variety of groups that could be used in nutrient indicators. Ongoing quantitative analysis of the data is being pursued to develop a useful, generalized and transferable molecular-based nutrient indicator. The results may be of interest to environmental agencies and stakeholders responsible for stream water quality in the region.