Assessment of the eutrophication of Al Massira reservoir (Morocco) by means of a survey of the biogeochemical balance of phosphate |
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Authors: | Mohamed Alaoui-Mhamdi Lotfi Aleya |
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Affiliation: | (1) Department of Biology, University of Sidi Mohamed Ben Abdallah, B.P. 1796 Fès-Atlas, Morocco;(2) Laboratoire de Zoologie et Protistologie, URA CNRS 138 Aubière Cedex, France |
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Abstract: | The biogeochemical balance of phosphate was studied in Al Massira reservoir (Morocco) from February 1991 to end January 1992. The study concerned P-supplies and losses by the Oum errbia river, sedimentation rate and water-sediment exchange.Supply and loss of phosphate were calculated from samples collected every 48 hours. Phosphate sedimentation rate was measured with sediment traps. The assessment of phosphate release at the water-sediment interface during either low oxic or anoxic conditions was made in situ with a benthic chamber.The results showed that phosphate input was higher than phosphate output resulting in a progressive increase of the internal phosphorus stock. The sedimentation flux ranged between 9 and 19 mg m–2 d–1 of P. Release of phosphate depended on the oxygen concentrations in the water.We suggest that a drastic control of phosphate input into the water must be achieved through a programme of dephosphorylation of the tributaries to avoid accumulation of calcium-bound phosphate which may become a source of upward release of bioavailable phosphate.Further investigations of this flux should be carried out to check the quantitative influence on phytoplankton community dynamics. |
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Keywords: | Morocco reservoirs sedimentation phosphate flux phosphate release |
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