Living on the edge: the sponge fauna of Australia’s southwestern and northwestern deep continental margin

Abstract

This first assessment of sponges on Australia's deep western continental margin (100-1,100 m) found that highly species-rich sponge assemblages dominate the megabenthic invertebrate biomass in both southwestern (86%) and northwestern (35%) areas. The demosponge orders Poecilosclerida, Dictyoceratida, Haplosclerida, and Astrophorida are dominant, while the presence of the order Agelasida, lithistid sponges, and the Verongida are noteworthy in providing contrasts to other studies from the deep temperate Australian margin. Most sponge species appeared to be rare as two-thirds were present in only one or two samples-a finding consistent with studies of the shallow Australian sponge fauna. The Demospongiae and Calcarea had similar distribution and abundance patterns being found in the greatest numbers in the south on the outer shelf and shelf edge in hard substrates. In contrast, the Hexactinellida were more abundant at deeper depths and in soft substrates, and were more common in the north. Although the environmental factors that influence sponge distributions on the western margin cannot be completely understood from the physical covariates analyzed in this study, the data suggest depth-related factors, substrate type, and current regimes are the most influential. Incompletely documented historic demersal trawling may partly account for the lower sponge biomass found in the north. The potentially high importance of sponges to benthic ecosystems, as well as the potential for high impacts on sponges by bottom trawling, indicates that maintaining healthy sponge assemblages should be an important consideration for marine conservation planners. Successful management will need to be underpinned by additional research that better identifies the ecological roles of sponges, and their distributions over local and broad environmental scales.

Phylogeny Drives Large Scale Patterns in Australian Marine Bioactivity and Provides a New Chemical Ecology Rationale for Future Biodiscovery

“…Australia is fortunate to have both a highly diverse marine biota and a high diversity of habitat types. High taxonomic diversity is seen in the deuterstome phyla and their ancestors such as the Porifera [15], [16], [17], [19]. This diversity is overlaid with diverse and unique biophysical features through latitudes that span from the tropical Indo-West Pacific to the cool temperate Southern Ocean, including unique combinations of overlap and zones of transition with mixed fauna and high endemism [10].…”

“…While the full extent of Australian marine biodiversity remains relatively unexplored [9], several marine biodiversity hotspots including centres of endemicity have been recognised, especially in coral reefs [11], [12], the temperate coastline [13] and the Great Australian Bight off the coast of South Australia is now known to support one of the world’s most diverse soft sediment ecosystems [14]. There have been reports on the high species diversity of sponges in the north west [15], [16], [17], [18], and in the deep sea off the south west [19], [20], and the Great Barrier Reef [18].…”

Sponges as important sources of nitrate on an oligotrophic continental shelf

“…Despite these caveats, given the difficulties of attaining data on sponge biomass distribution to a high level of taxonomic discrimination in highly speciose ecosystems such as southwestern Australia (Fromont et al 2011) and the difficulty in obtaining seasonally representative nitrogen flux measurement coverage of such a taxonomically diverse group, we would argue that the extrapolations made in our study are a necessary and valid approach and that our results support the conclusion that sponges contribute significantly to benthic resupply of nitrogen at the scale of the continental shelf off southwestern Australia.…”

First record of the genus Vetulina Schmidt, 1879 (Porifera: Demospongiae: Sphaerocladina) from the Indian Ocean with the description of two new species: biogeographic and evolutionary significance

“…1; Fromont et al 2012). Equipment used were a Sherman sled and beam trawl that sampled hard substrates.…”