Soft-bottom benthic communities in Otago Harbour and Blueskin Bay, New Zealand
- Author
- Rainer, S.F.
- Year
- 1981
- Journal / Source
- New Zealand Oceanographic Institute Memoir
- Number
- 80
- Pages
- 38
- Summary
- Quantitative sampling of the macrofauna of deposit substrata in Otago Harbour and Blueskin Bay was carried out between May 1965 and January 1967, using diver-operated sampling gear to collect all organisms retained by a 1 mm mesh. Eighty samples, mostly of 0.2 m2 area, were collected in a large scale survey, with 34 stations arranged in four transects. The samples were ordered into five communities, using environmentally-based criteria (sediment grade and stability, quantity of organic detritus, macroscopic algae and shell). Subdivisions were recognised within each community according to local variations in these characteristics. The presence of whole or broken mollusc shell usually exerted considerable influence on the species composition of a community, particularly in shallow areas, by providing a substrate for the growth of macroscopic algae. A total of 397 species was collected. Few of these were widely distributed, many species appearing to be restricted to a relatively limited range of environmental conditions. Species diversity (nUI!lber of species per sample) varied with grade, stability and degree of sorting of a sediment, and with the presence or absence of macroscopic algae. Lowest species diversity was found in samples from unstable fine sand and unconsolidated silt sediments, highest species diversity in samples from stable fine sand sediments with an admixture of shell. Samples from poorly-sorted sediments had a higher species diversity than samples from well-sorted sediments, while the presence of shell or macroscopic algae was usually associated with an elevated species diversity. Dominance diversity, d,, was highly sensitive to changes in species composition that did not appear to have general significance. Many of the species found occur in other sheltered or enclosed shallow-water areas in New Zealand. However, the communities recognised do not accord well with those listed by other authors for the New Zealand area, although a ¥acoma isocommunity may be present