27 November 2014
The initial ship-based expedition to Camden Sound was conducted under the auspices of WAMSI’s Kimberley Benthic Biodiversity Project, which aims to provide a better knowledge base about what occurs where in the Kimberley’s diverse marine environments, especially in areas of management priority such as the state government’s proposed marine parks and reserves.
Cruise leader on board the RV Solander, Dr Andrew Heyward from AIMS in Perth, said that the vessel operated 24/7 during its 18-day itinerary. “Scientists and staff worked in shifts, doing towed video and sediment sampling during daylight, and multibeam sonar surveys during the night,” he said.
Although the weather was generally very good, extreme tides, strong currents, turbid waters and some uncharted areas provided plenty of challenges for researchers. They successfully completed more than 200 km of towed video and thousands of km of multibeam seafloor mapping, in the first of two expeditions to the Camden Sound area.
“We’ve seen large areas of dynamic sand across the open Sound, including some patches with underwater sand dunes,” commented Andrew, “but also rocky ground covered in a large variety of marine invertebrates, in particular sponges and soft corals.”
The turbid waters of Camden Sound prevent sunlight from penetrating more than ~10 m in depth, so organisms that need light - such as corals and seaweeds - appear to be restricted to the shallowest parts of rocky ground and the upper edges of fringing reefs around islands. As depth increases and light fades the filter feeding sponges, soft corals, ascidians and bryozoans become the dominant components of the seabed communities.
“Thanks to the combined efforts of the Solander and the Linnaeus this month,” said Andrew, “we’re beginning to understand a lot more about what the seafloor of the Lalang-garram-Camden Sound Marine Reserve looks like, and the benthic biodiversity that lives there.”
Dr Iain Parnum from Curtin University is busily compiling all the gathered multibeam sonar data now. "In terms of outputs, first of all, we'll deliver some much-needed improved bathymetry information for Camden Sound," he explained. "Secondly, sonar backscatter data - both from the seafloor and the water column - will give us good insights into the kinds of underwater terrain and ecosystems at each sampled location."
In addition, Dr John Keesing from CSIRO took advantage of the presence of the RV Solander in the Kimberley to advance another WAMSI project investigating historic changes in water quality. He collected sediment cores (each ~1.5 m long) at ~20 m depth from two locations in Roebuck Bay. “These cores will be used to reconstruct a time series of water quality in the Bay, which is expected to go back about 100 years,” he said.
As with all WAMSI projects, the data and outputs will be freely available to everyone with an interest in the marine environments of the Kimberley.
Map showing sites in Camden Sound where towed video surveys were conducted in November 2014
A still image from one of the towed video surveys showing mixed filter-feeding community (including bryozoans, sponges and soft corals) growing on a rock outcrop (Photo courtesy of AIMS)