The deepwater megabenthic invertebrates on the western continental margin of Australia (100–1100 m depths): composition, distribution and novelty

WA Museum Records and Supplements | Updated 7 years ago

ABSTRACT – Taxonomic study of the first regional scale collection of deepwater invertebrate megabenthos from Australia’s western continental margin reveals a previously undiscovered high species richness and novelty. Benthic samples were taken systematically at 19 sites from Albany to Barrow Island (~35ºS to 21ºS) on the deep continental shelf (100 m depth) and upper continental slope (400 m). At some sites, additional samples were taken across-shelf at depths of 200 m, 700 m and 1000 m, with a couple as deep as 1200 m and 1500 m. Multibeam (swath) mapping of complex seabed topography enabled targeted collection of the epifauna on hard and soft substrates and targetting of features including submarine canyons.

A total of 2001 species including 396 (20%) confi rmed new species, 876 (44%) previously described species and 727 (36%) uncertain species were identifi ed within the taxa Porifera (Demospongiae), Cnidaria (Octocorallia, Antipatharia and Scleractinia), Mollusca, Echinodermata, Crustacea (Decapoda), Pycnogonida and Ascidiacea. The high proportion of new and uncertain species stemmed from poor knowledge of entire major groups (e.g. the Demospongiae), and from less well studied deep-sea taxa within otherwise well-known groups (e.g. the Bivalvia). Over half the species (1075) were collected only once. Distributional patterns of taxa show the western margin is an overlap zone of tropical and temperate fauna with a strong Indo-Pacific affinity (42% of described species) but an endemic fauna also exists (17% of described species).

This paper provides an annotated checklist of all these identifi ed species, along with live colour images of over half the species. All species can be cross-referenced to images and other collection information via a unique eight-digit computer code maintained in the Codes for Australasian Aquatic Biota database.

The research provides valuable information for consideration in the regional marine planning process and all biological specimens are lodged in Australian museums to enable ongoing examination of the diverse and largely undescribed fauna.