Developing Microbial Community Indicators of Nutrient Exposure using a Molecular Approach
Citation:
Hagy, J., K. Houghton, D. Beddick, J. James, S. Friedman, AND R. Devereux. Developing Microbial Community Indicators of Nutrient Exposure using a Molecular Approach. Society for Freshwater Science Annual Conference, Salt Lake City, UT, May 19 - 23, 2019.
Impact/Purpose:
The objectives of this study were to characterize periphyton community responses to water quality, and develop new sensitive and nutrient-specific periphyton indicators of water quality using a molecular approach based on analysis of DNA sequences. The most important and novel aspect of the research was use of DNA sequences to characterize microbial community composition of periphyton and develop indicators, providing an alternative to traditional approaches using microscopy. The presentation is based on a recently submitted manuscript and 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. The associated manuscript should be especially of interest to those working to advance application of molecular methods evaluating stream periphyton communities.
Description:
Biotic condition of streams with respect to nutrient pollution has been evaluated using biological indicators such as macroinvertebrate assemblages or periphyton communities, particularly diatoms. Molecular approaches have shown promise for this application, potentially because periphyton are incredibly diverse. To develop this further, we examined prokaryote and eukaryote community composition using 16S rRNA genes and 18S rRNA genes via experiments utilizing nutrient-diffusing substrata deployed in each of two streams in the southeastern United States. Experimental treatments included controls, +N, +P, and +N and P. Periphyton differed significantly by stream, date or season, and nutrient treatment, with more consistent community differences among prokaryotes compared to eukaryotes. Stronger nutrient effects were observed in the less nutrient-impacted stream. Combined +NP amendments decreased prokaryote species richness and diversity by 36%. Associations of taxonomic groups with nutrient treatments were evaluated using indicator species analysis and used to compute nutrient indicators. N vs. P effects were not well-resolved by broader community composition, but diatoms were more responsive to P than N. Results are encouraging in the context of existing studies, while also pointing toward further work needed to validate useful and practical molecular-based nutrient response indicators.