Nutrient limitation in two freshwater streams in the South Carolina Piedmont
Faculty Mentor
One WU mentor: Cynthia Tant, Ph.D.; tnatc@winthrop.edu
College
College of Arts and Sciences
Department
Biology
Faculty Mentor
Cynthia Tant, Ph.D.
Abstract
Understanding nutrient limitation is important for recognizing the requirements of the biofilm communities that form the base of stream food webs. Nutrient limitation experiments are also important in understanding eutrophication and changes in stream ecosystems. This project quantified nutrient limitation in two small, freshwater streams in the Catawba river basin within the Catawba Nation. I predicted that these two streams were colimited by both nitrogen (N) and phosphorus (P) due to the high demand of nutrients in the presence of low ambient nutrient concentrations. Nutrient limitation was assessed using nutrient diffusing substrates. Measurements included metabolism of both autotrophic and heterotrophic biofilm communities and ash-free dry mass (AFDM). Gross primary production (GPP) of autotrophic communities in one of the two streams was significantly higher in the control than either N or P additions. In the same stream, community respiration of heterotrophic communities was significantly higher in the N addition than the control, but not the other nutrient addition treatments. Heterotrophic AFDM for one stream showed a significant response to nutrient amendments; unexpectedly, the N addition had significantly lower AFDM than either controls or P addition. These results suggest that heterotrophs in one stream may be limited by nitrogen, which may be caused by increased light affecting the production and stability of bioavailable dissolved organic matter. In the other nearby stream, however, autotrophic and heterotrophic communities did not appear to be limited by either N or P. This study also found phosphorus inhibition, which may have been caused by too much phosphorus stimulation for these communities, leading to phosphorus toxicity.
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Honors Thesis Committee
Cynthia Tant, Ph.D.; Michael Lipscomb, Ph.D.; Jennifer Schafer, Ph.D.; Diana Boyer, Ph.D.
Honors Thesis Committee
Cynthia Tant, Ph.D.; Michael Lipscomb, Ph.D.; Jennifer Schafer, Ph.D.; Diana Boyer, Ph.D.
Course Assignment
HONR 450H - Tant & HONR 451H - Lipscomb
Nutrient limitation in two freshwater streams in the South Carolina Piedmont
Understanding nutrient limitation is important for recognizing the requirements of the biofilm communities that form the base of stream food webs. Nutrient limitation experiments are also important in understanding eutrophication and changes in stream ecosystems. This project quantified nutrient limitation in two small, freshwater streams in the Catawba river basin within the Catawba Nation. I predicted that these two streams were colimited by both nitrogen (N) and phosphorus (P) due to the high demand of nutrients in the presence of low ambient nutrient concentrations. Nutrient limitation was assessed using nutrient diffusing substrates. Measurements included metabolism of both autotrophic and heterotrophic biofilm communities and ash-free dry mass (AFDM). Gross primary production (GPP) of autotrophic communities in one of the two streams was significantly higher in the control than either N or P additions. In the same stream, community respiration of heterotrophic communities was significantly higher in the N addition than the control, but not the other nutrient addition treatments. Heterotrophic AFDM for one stream showed a significant response to nutrient amendments; unexpectedly, the N addition had significantly lower AFDM than either controls or P addition. These results suggest that heterotrophs in one stream may be limited by nitrogen, which may be caused by increased light affecting the production and stability of bioavailable dissolved organic matter. In the other nearby stream, however, autotrophic and heterotrophic communities did not appear to be limited by either N or P. This study also found phosphorus inhibition, which may have been caused by too much phosphorus stimulation for these communities, leading to phosphorus toxicity.
