Abiotic drivers of coastal fish community change during four decades in the Baltic Sea

Evidence for long-term change of marine ecosystems is increasing worldwide. Coastal areas harbour the socio-economically and eco-logically most vital aquatic ecosystems, but are under increasing anthropogenic pressure. Little is known, however, about how envir-onmental perturbations affect the development of coastal systems. In this paper, datasets of coastal fish communities covering almost four decades (early/mid 1970s to 2008) in three different basins of the Baltic Sea were analysed. There were clear changes in species composition over time in all but one dataset and coherence among basins in the timing of change. Changes were mainly associated with variables related to climate (water temperature, salinity, and North Atlantic Oscillation index), but less so with those reflecting nutrient status (nutrient concentrations and loading). Despite the importance of local water temperature, regional climatic variables were more important for the temporal development of communities. The results indicate that Baltic coastal fish communities have undergone large structural changes governed by processes acting on both local and regional scales. The findings suggest that ecological targets should be set accounting for long-term changes in community structure and that a common management of coastal and offshore ecosystems would be beneficial