Ice disturbance intensity structures benthic communities in nearshore Antarctic waters
Ice scouring is one of the 5 most significant natural forces acting on ecosystems, yet very few data exist linking the intensity of ice disturbance with parameters of benthic community structure. The benthos at 2 nearshore sites on Adelaide Island, Antarctica, was sampled at 3 resolutions to make novel links between biological data and empirical disturbance data from the literature. A total of 125 taxa and > 70 000 individuals were recorded. A total of 8 parameters of community structure were measured; all of them were negatively correlated to disturbance intensity at one site, whilst 6 significant relationships were found at the other site. At 2 of the 3 sampling resolutions, disturbance, rather than depth or the percentage cover of major substratum types, was the environmental variable most correlated with the patterns in community structure. Furthermore, biological samples were divided into 3 categories based on the disturbance data (low, moderate and high). Each group was statistically dissimilar and the relative abundance of sessile fauna decreased as disturbance intensity increased. The intensity of disturbance was broadly correlated with depth, but small-scale differences in topography and substratum type created small-scale refugia, which supported richer assemblages. Overall, both study sites were disturbed frequently and no evidence of a peak in richness at the moderately disturbed locations was recorded.