Ref ID : 3122
Edna Graneli and Kristina Sundback; The response of Planktonic and Microbenthic algal Assemblages to nutrient enrichment in shallow coastal waters, southwest Sweden. J.exp.mar.Biol.Ecol. 85:253-268, 1985
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Field and laboratory nutrient (nitrogen and phosphorus) enrichment experiments were performed using natural phytoplankton and microphytobenthic assemblages from the brackish waster Oresund, S.W. Sweden. The response of algae from a low-nutrient area (Falsterbo Canal) was compared to that of algae from a polluted, nutrient-rich area (Lomma Bay). The biomass (measured as chlorophyll-a) of both phytoplankton and microphytobenthos from the Falsterbo Canal increased after the addition of nitrogen. Phytoplankton growth was stimulated by the addition of phosphorus to the nitrogen-rich water of the polluted Lomma Bay. Sediment chlorophyll a showed no significant increase after the addition of nutrients in the Lomma Bay. In containers without sediment, phytoplankton uptake was calculated to account for ~90% of the disappearance of inorganic fixed nitrogen from the water. In the sediment containers the microphytobenthos was estimated to account for ~20% of the nitrogen uptake. The rest was presumably lost mainly through denitrification. When containers with microphytobenthos from Lomma Bay were kept in the dark, phosphorus was released at a rate of up to ~180 µM/m-2/day-1. We suggest that by producing oxygen microbenthic algae keep the sediment surface oxygenated thereby decreasing phosphorus transport from the sediment to the overlaying water.