Infaunal assemblages of the eastern Great Australian Bight: Effectiveness of a Benthic Protection Zone in representing regional biodiversity

This report describes the infaunal, macro-invertebrate assemblages of the continental shelf of the Great Australian Bight (GAB) in relation to environmental factors,
including water chemistry, hydrography and sediment type.
2. Patterns of species composition are examined to assess the effectiveness of the Benthic Protection Zone (BPZ) in representing the region’s benthic biodiversity.
3. A total of 240 species from 11 phyla were collected from 65 x 0.1 m2  Smith-McIntyre grabs.
4. Less than half of the taxa collected during this survey (99/240) could be confidently identified to the level of species, and it appears that a large proportion of the GAB
infauna is undescribed.
5. Motile, deposit-feeding organisms (primarily annelids and crustaceans) dominated samples, and comprised over 25% of the abundance and 35% of the species collected.
6. Most infaunal organisms collected were relatively uncommon, and 86% of species individually represented less than 2% of the total abundance.
7. Correlation analyses revealed a strong and significant positive relationship between species richness and abundance, and highlighted a general decline in both parameters with increasing latitude.
8. Numbers of species and total abundance were typically highest near the Head of the
Bight, where water temperatures are elevated, and in inner-shelf waters off the western Eyre Peninsula, which support high levels of plankton productivity.
9. The infaunal distribution pattern corresponds closely with spatial patterns in epibenthic standing-stock, and reinforces the notion that Head of the Bight and western Eyre Peninsula are ‘hotspots’ of benthic biodiversity.
10. Cluster analysis of species abundance data identified three community groupings, closely related to depth. As all three communities were represented within the BPZ,
it appears that this zone is well placed to represent and preserve the infaunal biodiversity of the eastern GAB.