Tasmania – Rocky Reef Habitats

The temperate rocky reef habitat of SE Tasmania consists of diverse algal, sponge and invertebrate assemblages that provide structure for mobile fauna such as fishes, lobsters and urchins. Below the algal rich zones is a rich, poorly documented sessile invertebrate fauna.

Several reference sites have been surveyed in Tasmania to determine rate of change of benthic habitats near the Tasman Peninsula, Freycinet Peninsula Marine Protected Area (MPA) and Governors Island. The objectives of these surveys is to document biological assemblages associated with rocky reef systems in deep shelf waters beyond normal diving (>25m) depths. At each location, multiple reefs were surveyed at a range of depths from approximately 50 m to 100 m depth. Where distinct ectones (e.g. reef to sand) are present, transects were designed to cross transition zones and help determine the uniqueness of ectonal assemblages. Replication depended upon site logistics, however, dive profiles were designed to provide sufficient replication to quantitatively determine abundances of key species/features within depth strata, within reefs, between reefs (km to 100 km scale), and between differing levels of reef complexity.

The AUV sites in eastern Tasmania are part of a multi-disciplinary experiment, where the analysis of covariance is being undertaken on co-located fine-resolution seabed habitat data, provided by the detailed multibeam sonar bathymetry data collected by Geoscience Australia (EM3002 multibeam sonar) coverages, and biological datasets collected at similar spatial scales by Remotely Operated Vehicles (ROVs), Baited Underwater Video systems (BRUVs), towed video and the AUV. This research is being undertaken by the University of Tasmania and Geoscience Australia as part of the National Environmental Science Programme (NESP) Marine Biodiversity Research Hub, which is a collaborative program funded under the Commonwealth Government's National Environmental Science Program [NESP - link]. Within this Hub, several interrelated projects are designed to develop and test appropriate surrogates for biodiversity and incorporate these into an advanced predictive framework that covers a range of spatial scales.

The AUV data enables a finer scale coupling of biological datasets with multibeam bathymetry than data collected through the use of ROVs, BRUVs and towed video alone, because of geo-referencing errors associated with Ultra Short Baseline Acoustic Positioning System (USBL) tracking systems. This additional data allows scale matching errors to be examined in more detail and allow surrogacy to be examined at the finest possible scale. Ultimately, researchers are able to compare the relative efficiency of using AUV, ROV and towed video systems for shelf habitat biological surveys. In addition, the high resolution images produced by the AUV significantly enhance the ability to identify taxa, adding finer taxonomic resolution, and hence value, to the data collection. 

Surveys in Tasmania began in 2008 and have continued on an annual basis.  We have a set of sites along the southern and eastern coast of Tasmania that are revisited on a bi-annual basis, spanning near-shore reef systems affected by the long-spined urchin Centrostephanus rodgersii, to deepwater sponge habitats in the Flinders Island Commonwealth Marine Reserve.  Much of this work has been coordinated through the NESP biodiversity hub and aims to document and model benthic habitats around Tasmania.  In early 2015 we were able to visit sites on the SW corner of Tasmania that form part of the Commonwealth Marine Reserve offshore of Maatsuyker Island.