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Presented at the NABS Annual meeting, Athens, Georgia, 2003
in Changing Land Use Effects on Aquatic Food Webs
Watershed effects on water quality and primary producers in shallow ponds
J.N. Anderson1, G.W. Fairchild1, and D.J. Velinsky2. 1Department of Biology, West Chester University, West Chester, PA 19383, 2Patrick Center for Environmental Research, Academy of Natural Sciences of Philadelphia, Philadelphia, PA 19103
Unlike larger lake and stream systems, the response of shallow ponds to watershed influences remains largely unstudied. Inputs of nutrients and sediments to shallow ponds can potentially lead to shifts between macrophytes and phytoplankton, resulting in profound effects on pond trophic structure. This project examined 13 ponds with widely varying watershed characteristics and trophic state. Land use/land coverage within each watershed was classified using digital orthophotos; the watersheds of 7 ponds were primarily residential, while 6 were agricultural. Based on 3 sampling visits during the spring and summer of 2002, total P and total N varied among ponds from 16 to 350 ug P/L and 518 to 5700 ug N/L; N/P ratios varied widely but typically indicated probable P-limitation. Rapid light attenuation in most ponds (secchi depths ranged from 0.06 to 3.4 m) was caused by high densities of phytoplankton and suspended sediments. Either phytoplankton or metaphyton biomass dominated most ponds, and only a few ponds contained abundant macrophytes. Using both nutrient budget and statistical models, our study evaluates the strength of linkages between watershed land use/land coverage, water chemistry, and primary producer abundances in shallow pond systems.
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