The Macrobenthos of Moreton Bay

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Abstract
The macrobenthos of Moreton Bay is diverse, with 355 species collected from 400 dredged stations. Many of these species are distributed throughout the Indo—West—Pacific area, others have an Australian distribution (possibly some may also occur in the northern hemisphere), and others are known as yet only from Moreton Bay. The occurrence of the richest sites near the edges of the bay can be attributed to either favorable hydrographic—sedimentary conditions or to the location of these sites on the periphery of areas worked by prawn trawlers. Infrequently occurring species dominate the epifauna, and frequently occurring species dominate the infauna. Neither the infrequent species nor the four most frequent species show seasonal changes, but some seasonal change is evident in other species. Species occurring in more than eight sites usually showed a distribution pattern, but species patterns could not, by inspection, be classified into group patterns. By limiting consideration to the 32 commonest species six somewhat uncertain groups could be recognized related to substratum. Computer analyses were attempted involving successively: (1) reduction of data (species occurring infrequently were eliminated; correlation coefficients and non—metric coefficients between pairs of the remainder were computed, and species never appearing above an arbitrary limit were excluded); (2) clumping of sites (eight meaningful site patterns were derived by using clumps of contiguous sites, which is equivalent to increasing the "quadrat size" and thus increasing the frequency of coincidences); (3) defining species—groups (the above site pattern was used, and additional species were included); and (4) establishing site—group species—group coincidences (this involved a double standardization and choice of the level of classification of species—group (six) which appeared to give optimal clarity). Site—groups are not uniquely defined by the presence of a species—group which occurs nowhere else; instead, differences between site—groups are quantitative. The site—groups conform to a topographical pattern related to a complex including hydrographic and sedimentary factors and possible human activity. The species—groups are generally large and ill—defined. Results are compared with more classical studies of benthic communities, and a distinction is here made between constant and faithful species.

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