Effect of Sedimentation on Infaunal Invertebrate Populations of Cobequid Bay, Bay of Fundy

Construction of a tidal dam in the upper reaches of the Bay of Fundy is expected to result in deposition of sediment. We investigated the effect of sediment deposition on populations of three major benthic species of the upper reaches: Corophium volutator, Macoma balthica, and Mya arenaria. In fences and boxes that induced deposition on intertidal mudflats, accumulation of 1.0–3.5 cm of sediment at rates of 1.9–10.2 cm/mo caused Corophium density to decrease sharply, usually by an order of magnitude. Macoma density was generally unaffected. In fishing weirs, mud that accumulated at 1.5 cm/mo to a mean depth of 5.2 cm supported normal Corophium densities. The effect of sedimentation on Mya depends strongly on grain size: LD50 was 24 cm for coarse sand, 6 cm for fine sand, and 3 cm for mud. Mya is able to burrow upward in accumulating coarse sand. Even moderate rates and depths of sediment deposition, particularly of fine sediment, could have a major adverse effect on existing Corophium and Mya populations.Key words: Bay of Fundy, tidal power, sedimentation, grain size, water content, Corophium volutator, Macoma balthica, Mya arenaria