AIMS 2013 Biodiversity Survey of Glomar Shoal and Rankin Bank

Rankin Bank and Glomar Shoal shoals are situated 147 km North West and 93km North, respectively, of the Dampier Archipelago in North Western Australia. They are the only large, complex bathymetrical features on the outer western shelf of the West Pilbara. Rankin Bank rises steeply from 120m depth along its north eastern margin and in all other quadrants it rises above the surrounding continental shelf from approximately 80m depth. The main body of the shoal takes the form of several highly complex and rugose peaks and plateaus, reaching 20-40m below the sea surface. In comparison, the much larger Glomar Shoal rises on all sides from 80m depth and, as a whole, shallows more gradually to include a plateau region lying within 40m of the surface. At the 60m depth contour Glomar Shoal covers an area of 14699.6 hectares, which is approximately 8.5 times larger than Rankin Bank which covers an area of 1721.5 hectares. The shoals were surveyed from the Australian Institute of Marine Science (AIMS) Research Vessel, RV Solander, using multibeam equipment and technicians provided by Fugro Survey Pty Ltd, during August - September 2013. For both shoals, continuous coverage bathymetry, rugosity digital elevation and terrain models were produced. These data were then used to ensure key areas of depth, aspect and slope were sampled during the subsequent biodiversity sampling cruise in September 2013. Data on biota was collected using underwater towed cameras for benthic habitat assessment and stereo baited remote underwater video stations (SBRUVS) to sample fish. In addition, seabed surface sediments were collected around each shoal, using a grab sampler, and analysed for grain size and chemical composition.