You are here:
Relationships Among Watershed Condition, Nutrients, and Algae in New England Streams Affected by Urbanization
Citation:
SMUCKER, N., N. E. DETENBECK, A. C. MORRISON, AND M. BECKER. Relationships Among Watershed Condition, Nutrients, and Algae in New England Streams Affected by Urbanization. Presented at Society for Freshwater Science Annual Meeting; Freshwater Stewardship: Challenges and Solutions, Louisville, KY, May 20 - 24, 2012.
Impact/Purpose:
Urbanization can negatively affect stream ecosystems by altering water chemistry, habitat, and nutrient, sediment, and hydrological regimes. As a part of research focused on quantifying and managing urban effects on stream ecosystems in New England, different methods for deriving nutrient criteria and the responses of algal biomass and diatom metrics to water chemistry and land cover in upstream watersheds were examined. Multiple regression models, in which impervious cover explained the most variation, indicated concentrations <0.202 mg/l nitrate and <0.015 mg/l total phosphorus as potential goals for protection. Streams with nutrient concentrations greater than these values had greater percent impervious cover and less forest in upstream watersheds, greater algal biomass and percentages of tolerant diatoms, and lower percentages of sensitive diatoms than did low nutrient streams. As the foundation of primary production, algal biomass and diatom community structure can be effective indicators of human impacts on stream ecosystems and potentially, indicators of changing trophic status of streams.
Description:
We examined algal metrics as indicators of altered watershed land cover and nutrients to inform their potential use in monitoring programs. Multiple regression models, in which impervious cover explained the most variation, indicated concentrations <0.202 mg/l NO3 and <0.015 mg/l TP as potential goals for protection. Streams with nutrient concentrations greater than these values had greater percent impervious cover and less forest in upstream watersheds, greater algal biomass and percentages of tolerant diatoms, and lower percentages of sensitive diatoms than did low nutrient streams (Wilcoxon t-tests, p < 0.01). Low nutrient taxa declined at values near these concentrations and in relation to impervious cover, but high nutrient taxa increased in a more linear fashion. Stepwise multiple regression models indicated that the interaction of chemistry and watershed land cover typically represented 65-79% of the total variation explained in diatom metrics. Ongoing examination of BMPs, sewerage practices, and discharge permits may further inform models, and management strategies, such as green infrastructure, and criteria development will be discussed.