Change of topography and sediment characteristics on an intertidal mud-flat following mass-mortality of the amphipod Corophium volutator

A Corophium-bed characterized by a mosaic of emerged areas and tidal pools during low water was established on an intertidal flat in the southern part of the Danish Wadden Sea. In spring 1990, the plateaux harboured relativel y high densities of the amphipod Corophium volutator, whereas the amphipods were almost absent in the pools. Following a parasite-induced mass-mortali ty in the population of Corophium, summer 1990, the plateaux of the bed wer e subjected to sediment erosion, The heterogeneous plateau-pool structure d isappeared, accompanied by increased median particle diameter and decreased silt content in the former plateau sediment. These events were accompanied by increased chlorophyll-a concentrations in the sediment of both plateau and pool areas. The results suggest Corophium volutator to be the single most important org anism stabilizing the plateau sediment, and hence, the heterogeneous topogr aphic structure of the Corophium-bed. It is proposed that the stabilizing e ffect of Corophium burrows also in deeper sediment strata may outweigh the surface stabilizing influence of epipelic diatoms, as well as the negative effect of amphipods eating the diatoms, in non-cohesive coarser sediments.