The significance of streams as transporters of nutrients from terrestrial watersheds is growing as the increasing deposition of nutrients by humans often exceeds the capacity of many terrestrial ecosystems to absorb them. This study will evaluate the impact of nutrient pulsing in a low-nutrient (oligotrophic) forest stream in South Dakota. Rapid Creek is a spring fed creek characterized by very low nutrient concentrations. It has been experiencing a nuisance algal bloom. This phenomenon is unusual because typically algal blooms are directly related to anthropogenic nutrient loading, yet blooms of this diatom (Didymosphenia geminata) are often associated with nutrient-poor waters. Since this diatom can significantly impact stream ecosystem structure and function and impact fisheries, the South Dakota Game, Fish, and Parks Department is adding slow-release fertilizer to Rapid Creek in an attempt to prevent the bloom of D. geminata. To evaluate the impact of this nutrient loading on the biological and abiotic components of this stream, this study will examine nutrient dynamics upstream and downstream of the dosing site. Since the growth of diatoms is sensitive to the optimal ratio of important nutrient elements, this study will focus on nutrients such as carbon, nitrogen, phosphorus and silica; and on biological responses such as changes in enzyme activity, dissolved oxygen and chlorophyll production. These measures will provide insights into the health of the ecosystem. This project also enhances student research training and education while generating valuable data that will be broadly applicable to other ecosystems.
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Funding for this project was provided by a grant from the National Science
Foundation.