Quelques donnees sur l'ecologie d'une zone marine littorale recevant les rejets d'une raffinerie de petrole

Abstract

The effects of a petroleum refinery effluent overflow in the sea on the physical and chemical characteristics, phytoplanktonic production and bacterial population have been studied. The high temperature of the water effluent involves thermic variations in the overflow area, occasionally producing an environment very poor in oxygen. Variable but sometimes very high PPO 4 concentrations induce serious disturbances in the NNO 3/PPO 4 ratio. An NNO 3 reduction, probably of bacterial origin, increases the lack of balance of this ratio. Chlorophyll a concentrations measured close to the effluent area are approximately equal to those of offshore waters but the NNO 3/PPO 4 ratio lead us to assume that phytoplanktonic species may be different. Bacteria utilising a gas-oil as the sole carbon source represent 10% of heterotrophic bacteria in the effluent area and 4% in an area not directly polluted by hydrocarbons. Physical and chemical conditions in the effluent area are not favourable to the phytoplanktonic population equilibrium, but seem to be so for a hydrocarbon degradation by bacteria.