Community level response to climate change: The long-term study of the fish and crustacean community of the Bristol Channel

Results from a 30-year study of fish and crustacean abundance at Hinkley Point, Somerset, England are reported. Standard community ecology metrics, including annual total species number recorded, alpha diversity and dominance indices, the rank-abundance curve and the assemblage of permanently present species, have all shown notable stability and no trend over the study period. In contrast, community structure has shown clear change which can be related to the fact that the abundances of many species have shown long-term trends. Of the 30 most abundant species, which together comprise more than 99% of the total species number and biomass collected, 17 have shown a long-term trend in log abundance indicative of exponential change. 9 species have shown approximately exponential increases, and 8 exponential decreases in abundance. This remarkable variation in individual species' abundance has been shown for some species to be related to changes in sea water temperature, the North Atlantic Oscillation Index, and salinity. While annual species richness has not increased, the number of species present each month has, on average, increased. This has been caused by changes in seasonal presence, with summer-autumn species extending their presence further into the winter. For fish, the dominant species show no trend, and it is argued they are likely to be under density-dependent control. It may be that while the most abundant species are constrained by resources, the majority of less abundant forms are dynamically unstable and more likely to be responsive to environmental change. (C) 2011 Elsevier B.V. All rights reserved.