WA and Leeuwin Current

The first deployments undertaken as part of the establishment of the IMOS AUV facility benthic reference site program in WA were completed off the coast of Western Australia during April, 2010. These surveys targeted rocky reefs along the temperate West Australian coast.  Surveys were conducted off Rottnest Island, Jurien Bay, and the Abrolhos Islands. Six sites were surveyed at each location spanning three depths (15 m, 25 m, 40 m), both inside and outside MPAs, with three 25m x 25m full-coverage imaging surveys devoted to each site.  

Site locations targeted kelp beds and were provided by the science party as shape files overlaid on local bathymetric geotiffs. These areas varied in extent between 50m on a side at the smallest up to a few hundred meters on a side. The locations of individual 25m x 25m full coverage grids were designed in consultation with the science party to sample rugose areas within the survey boxes, with a spacing of up to 100 m between grids, or in the absence of detailed bathymetry (Abrolhos Coral Patches sites) to span depth gradients within the survey box.

The temperate Western Australian sites were revisited during April, 2011, 2012 and again in 2013.  In 2014 only sites at the Abrolhos Islands were surveyed owing to the availability of shiptime. Preliminary analysis of the data suggests that there were significant changes in some of the habitats, particularly those in the north of the survey region.  Observations of coral bleaching and distressed kelp correlate closely with a marked increase in water temperatures measured in these areas.  Our end users are now conducting an in-depth analysis to describe the changes in these habitats both at broad scales and at the level of individual coral colonies.