POLYCHAETE DISTRIBUTION AND DIVERSITY ON THE CHATHAM RISE, SOUTHWEST PACIFIC
Glasby, C. J.1; Read, G. B.1; Grove, S. L.2 & Probert, P. K.2
1National Institute for Water & Atmospheric Research, PO Box 14-901, Kilbirnie, Wellington, New Zealand
2Department of Marine Science, University of Otago, PO Box 56, Dunedin, New Zealand
The distribution of polychaete assemblages was investigated using clustering and ordination (multidimensional scaling) analyses. Samples were collected at 8 sites along a north-south transect across the Chatham Rise (depth range 350 m to 2300 m) in the vicinity of the Subtropical Convergence. At each site, 3 or 4 replicate samples were taken using a box corer and all polychaete taxa retained on a 420 mm screen identified to the lowest possible taxonomic level. Sediment grain size distribution was estimated from samples of the top 10 mm taken with a multicorer. Possible environmental factors (sediment, depth, carbon flux, latitude) influencing the distribution of assemblages was determined using the BIOENV method, part of the PRIMER software package (Plymouth Marine Laboratory). Over 1 700 individuals representing 174 species and 38 families were identified in 28 core samples. Eight families represented 64% of all individuals and 50% of all species and were, in order of abundance, Spionidae, Paraonidae, Cirratulidae, Syllidae, Ampharetidae, Orbiniidae, Maldanidae and Lumbrineridae. We quantify polychaete diversity on the Rise and compare our results with those of a previous study, which indicate that the southern slope supports higher polychaete densities than on the northern slope but that community composition is less diverse.