Benthic community re-adjustment following dredging of a muddy-maerl matrix

Changes in the benthic infaunal community structure at a location in south-west Ireland subject to dredging impacts were studied. Dredging of a muddy-maerl matrix takes place with a seasonally varying frequency of 2–5 times per month. The benthic infauna at a currently dredged site was compared to a fallowed portion of the area, at which extraction ceased 6 months prior to the study. As virtually the entire licensed area is dredged in rotation, longer term recovery is not possible at the study site. In contrast to numerous other study, the benthic infauna at the dredged site was not depleted, but did exhibit higher levels of stress and a higher diversity than the fallowed site. A clear shift from the abundance of omniverous crustaceans in the dredged area to filter-feeding bivalves in the fallowing area was observed. These observations are thought to be linked to sediment mobility, the creation of spatial patchiness and the mobilisation of food resources.