The influence of Corophium volutator abundance on resuspension

Two experiments were performed to test the hypothesis that Corophium voluta tor affects the turbidity of water in estuaries through active resuspension of sediment. One experiment was done in a flume system under different flo w velocities, and one in aquaria. A diatom film developed at the sediment s urface in both experiments before Corophium was added. This diatom film was supposed to have a stabilising effect on the sediment. In both experiments , the concentration of suspended solids in the water column increased with the density of Corophium individuals. No effect of flow velocity on suspend ed solids concentration was found. This indicates that, in our flume experi ment, active resuspension by Corophium was more important than physical res uspension, at least at low flow velocity (<20 cm s(-1)) and in the presence of a diatom him. The critical erosion threshold decreased with increasing Corophium density in the aquarium experiment, indicating that indirect effe cts of Corophium grazing may become more important at high levels of bottom shear stress. The implications of our findings for suspended solids concen tration in estuarine systems are discussed.