Valve movement response of the mussel Mytilus galloprovincialis to metals (Cu, Hg, Cd and Zn) and phosphate industry effluents from Moroccan Atlantic coast

Valve activity was measured in the Mediterranean mussel Mytilus galloprovincialis in response to sublethal concentrations of four metals (Hg, Cu, Zn and Cd) and two phosphate industry effluents from the Atlantic coast of Morocco. Valve movements were monitored using a proximity inductive sensor which could display all activity figures from full closure to wide opening of the shell valves. In a 1 h exposure experiments, all metals induced a decrease in the time of normal opening and the appearance of sequences of stress behaviour, including enhanced valve adductions and complete closure at high concentrations. Mercury (tested from 5 to 75 μg Hg l) was the most toxic to the valve activity, with a threshold effective concentration at 10 μg Hg l and full valve closure occurring at 50 μg Hg l. Copper (15-150 μg Cu l) showed a toxic effect starting at threshold concentration of 20 μg Cu l and induced full valve closure at 150 μg Cu l. Zinc (100-500 μg Zn l) was effective in reducing the time of normal opening (threshold concentration at 100 μg Zn l) but no complete closure was recorded in any of the tested concentrations. For cadmium (1000-5000 μg Cd l), the valve activity was insensitive for exposures under 2000 μg Cd l. Results for the testing of several samplings of the phosphate industry effluents (Safi and Jorf Lasfar) showed that their toxicity varied over the time. The effluent of the Jorf Lasfar plant (2-9.4%) was, however, more toxic than that of Safi (1-25%). In the light of these results, the sensitivity of the valve activity of Mytilus galloprovincialis to pollutants and its usefulness for in situ monitoring of coastal pollution in Morocco are discussed. © Springer Science+Business Media, LLC 2006.