Physico-chemical characteristics of Port Curtis and their influence on the community composition of bottom dwelling fauna

Spatial patterns in benthic infaunal community structure of Port Curtis estuary (north-eastern Australia) were determined from quantitative grab samples and examined in relation to environmental variables. A total of 149 riverine, estuarine and open coastal stations were sampled during the survey, and 5744 individuals and 466 species identified. Filter-feeding organisms (primarily polychaetes, molluscs and crustaceans) dominated the bedforms, and accounted for 50% of the total species abundance and 30% of the total species richness. Most taxa were uncommon, and 98% of species individually represented less than 2% of the total abundance. Distributional patterns in total species richness and abundance were highly correlated, and both parameters varied significantly with sediment structure. Numbers of species and individuals were typically highest in coarse-sand and gravel sediments, and lowest in fine, well-sorted, sands. Cluster analysis of species abundance data revealed nine community groupings characterised by small species subsets with restricted distributions. These groupings were found to be primarily related to measures of depth, salinity, dissolved oxygen and sediment structure. Not all variation in community structure was explained by these environmental variables, and it is likely that other unmeasured factors play an important role in determining benthic faunal composition in the estuary.