MODERN BRYOZOAN ASSEMBLAGES AND DISTRIBUTION ON THE COOL-WATER LACEPEDE SHELF, SOUTHERN AUSTRALIAN MARGIN

Modern and relict sediments on the cool-water Lacepede Shelf are domin ated by fragments of bryozoans, molluscs and foraminifers. This study evaluates the distribution of modern bryozoan sediment on the Lacepede Shelf based on 88 species from 16 localities using cluster analysis a nd principal component analysis. Six bryozoan faunal assemblages, corr esponding roughly to physiographic position on the shelf, are recogniz ed objectively. Assemblages are robust and generally defined by the ch anging diversity and relative abundance of the bryozoan fauna across t he shelf. Slope assemblages can be differentiated from shelf assemblag es based on presence or absence of a few key species. Lateral variatio n along the three transects is associated with: (i) differences in she lf geometry (shelf width, depth of shelf edge and angle of the slope); (ii) previous influx of continental sediments; and possibly (iii) pre sence of upwelling and long-shelf currents. Data were also evaluated t o determine the level of detail required to provide the optimal inform ation, with the most efficiency, from diverse bryozoan faunas. Presenc e-absence data for species prove nearly as effective in determining br yozoan assemblage distributions as analyses that incorporate taphonomi c and abundance information. In addition, similar distribution pattern s were observed using as few as 12 key species. The distribution of br yozoan species provides additional insight into the composition of car bonate skeletal particles on the Lacepede Shelf and the ecology of the diverse bryozoan fauna. These data are contributing to our understand ing of the development of cool-water carbonates.