Patterns of infaunal macromollusc assemblages in a subtropical marine park: implications for management

Characterisation of habitats and communities is necessary to allow managers knowledge of the ecological resources they are charged with conserving. However, the high cost of gathering such data often precludes their incorporation into conservation planning, and habitat surrogates are often relied upon to represent underlying biotic patterns. In New South Wales (NSW), Australia, extensive surveys informed the development of a state-wide habitat classification scheme (HCS) for biodiversity management based on the distribution of habitat types by water depth. To test the suitability of the current HCS for soft sediments, we compared infaunal mollusc assemblages at two different depths, and at scales of kilometres to tens of kilometres, within five coastal regions of the Cape Byron Marine Park (CBMP). Mollusc assemblages differed significantly between depths and among the range of spatial scales examined, and patterns were significantly correlated with mean grain size and sorting. Species richness also differed between depths and among sampling locations, whereas abundance differed between depths and among sites nested within locations. Although the present study provides preliminary support for the relevance of the NSW HCS depth categories in the CBMP, it also suggests that future refinement should consider the inclusion of categories based on sediment characteristics.