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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Periphyton
EPILITHIC PRIMARY PRODUCTION AND RESPIRATION IN IRISH LAKES OF DIFFERENT TROPHIC STATUS.
D.M. DeNicola1, K. Irvine2, and E. De Eyto2. 1Department of Biology, Slippery Rock University, Slippery Rock, PA 16057, 2Department of Zoology, Trinity College Dublin, Dublin 2, Ireland
Primary production of shallow epilithic algal communities for 21 lakes of different trophic status in the Irish Republic was measured by changes in dissolved oxygen in chambers. The relationship of benthic production parameters to physico-chemical variables (temperature, total N, total P, pH, alkalinity, conductivity, color, turbidity, and phytoplankton chlorophyl) were analyzed by stepwise multiple regression. Alkalinity and turbidity were significantly the best predictors of net primary production, while color and turbidity best predicted respiration rates. Of the other variables, only total N had at least moderate predictive capacity. Several lakes with very high nutrient concentrations had low epilithic production because of shading by phytoplankton and turbidity. The predictive capacity of alkalinity was likely related to land use, as lakes in limestone areas are more influenced by agricultural inputs. In addition, two marl lakes with low nutrient levels and clear water, had high benthic productivity. Overall, production of epilithon was not significantly related to a priori traditional trophic classification based on phytoplankton chlorophyl or total P. Benthic algal productivity can be an important source of organic matter in lakes. Using trophic status to predict its relative contribution to the food web, however, requires determination of nutrient thresholds for the above interactions.
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