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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Periphyton
FACTORS AFFECTING PERIPHYTON OXYGEN DYNAMICS: METABOLISM CHAMBER EXPERIMENTS UNDER CONTROLLED CONDITIONS.
T.L. Bott1 and T.W. Gallagher2. 1Stroud Water Research Center, 970 Spencer Rd., Avondale, PA 19311, 2HydroQual, Inc., 1 Lethbridge Plaza, Mahwah, NJ 07430
The effects of temperature, light intensity and nutrient concentrations on oxygen dynamics of periphyton from the Jackson River, VA, were studied in metabolism chambers in the laboratory to permit independent manipulation of variables. Control of water velocity (usually 0.3-0.54 m/sec) was enhanced by fitting chambers with venturi inserts. Temperature was regulated by immersing chambers in water jackets; light intensity from coated halogen lamps was regulated using layers of shade cloth, and nutrient concentrations were altered by adding or withholding ammonia, nitrate, phosphate, bicarbonate and silicate. Oxygen dynamics were monitored continuously using DO probes. Experiments were performed with dense filamentous growths dominated by Melosira and Cladophora spp. (mean concentrations of 442 mg chlorophyll a/m2, 47 g organic matter/m2) and rocks lightly coated with diatoms and silt (94 mg chlorophyll a/m2, 23 g organic matter/m2). Community respiration increased ~10% per °C between 13 and 26 °C. Primary productivity saturated at light intensities usually between 500 and 1000 μmol quanta.m-2.sec-1 with direct relation to biomass density. Except for carbon, nutrient additions did not induce immediate responses in oxygen dynamics, presumably because of nutrient storage in biomass or scaling effects.
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