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Tuesday, June 5, 2007
535
Evaluation of a Novel Nutrient-Diffusing Substrata Design Used to Estimate the Effects of Nutrient Enrichment on Alkaline Phosphatase Activity and Nitrogen Fixation
David A. Lang, J. Thad Scott, and Ryan S. King. Department of Biology, Center for Reservoir and Aquatic Systems Research, Baylor University, Waco, TX 76798
Novel nutrient-diffusing substrata (NDS) were evaluated to estimate the effect of nutrient treatments (control, nitrogen = N, phosphorus = P) on alkaline phosphatase activity (APA) and N2 fixation in a stream-like outflow of a constructed freshwater marsh. Periphyton biomass accrual, APA, and N2 fixation were estimated 6, 18, and 29 days after deployment. Nutrient diffusion rates were estimated from the NDS media in order to evaluate nutrient depletion during the study period. Moreover, we evaluated whether APA can be accurately estimated on same-sample NDS following estimation of N2 fixation by acetylene reduction. APA rates of controls and N treatments were significantly higher than the P treatment on each day following deployment. N2 fixation rates of both controls and P treatments were significantly greater than the N treatment only on day 18, though the controls remained significantly higher on day 29. APA results were different when periphyton were analyzed following the acetylene reduction assay, thus only those results of APA measured alone were utilized for comparison of periphyton APA. These data demonstrate that APA and N2 fixation are strongly influenced by nutrient availability and may be useful in assessing the effects of nutrient pollution on key ecosystem processes.
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