Pumping behaviour and filtration rate of the freshwater mussel Potomida littoralis as a tool for rapid detection of water contamination

Abstract

In order to evaluate the ability of the freshwater bivalve Potomida littoralis for use as a biodetector of aquatic pollution, the short-term effects of some pollutants (metals, antifouling product and effluents) on pumping activity of this mussel were studied qualitatively (pumping behaviour) and quantitatively (filtration rate). The method of the flow sensing at the exhalent siphon showed that the normal activity of P. littoralis was characterized by a continuous pattern of pumping with occasional and brief interruptions. When exposed to toxic stress, the exhalent flow immediately shifted to an intermittent pattern with periods of pumping alternating with periods of pause that could last several minutes. The threshold concentrations of heavy metals/antifouling agent inducing this type of activity within 2 h were: 25 µ gl −1 for copper, 90 µ gl −1 for cadmium, 5 µ gl −1 for mercury, 3000 µ gl −1 for zinc and 700 µ gl −1 for the antifouling agent Mexel. Both the effluent samples of the urban wastewater of Marrakech city tested were found to be toxic. The filtration rate of control animals ranged from 0.91 to 1.72 l h −1 g −1 animal, while after 3 h exposure to Cu, Cd , Hg and the effluent E1 and E2, filtration rates were decreased by concentrations above the threshold levels set as toxic for the pumping activity. The sensitivity of P. littoralis to pollution and its usefulness as biodetector for rapid toxicity screening is discussed and a procedure for the detection of pollution in Moroccan freshwater is proposed.