Scientists have made history off the coast of Narooma, finding an extinct volcano with help from the research vessel Investigator.
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In the early hours of Saturday morning, the CSIRO research vessel was working hard to survey the sea floor south of Montague Island.
Associate Professor Martina Doblin, of the University of Technology, Sydney; Professor Iain Suthers, of the University of New South Wales; and Amy Nau, of the CSIRO Marine National Facility were aboard.
Ms Nau noticed something different.
“A rapid change in the profile of the sea floor captured by the multibeam sonar system showed that the ship had passed over a reef, popular with locals and known as Twelve-Mile Reef,” the trio of scientists said in a statement to the Narooma News.
“Even more distinctive was the output from the fisheries echo sounder.
“The bioacoustic signals of this sensitive equipment showed plankton and smaller fish in surface water, as well as schools of larger fish in bottom water, close to the reef.
“The reef, 4 km south of the listed position, was revealed in unprecedented detail by the ship’s state-of- the-art swath mapper.
“The reef appears to be the remnant of an old volcano, submerged more than 110 m below current sea level. At the top of the reef is a circular depression approximately 200 m across, only 15 m above the surrounding continental shelf.”
Prof Suthers is excited by its history.
“It’s entirely feasible that this ancient eroded feature hosted indigenous Australians over 10,000 years ago, when sea level was lower during the last ice age,” Professor Suthers said.
“It’s also remarkable that such a shallow rocky reef can influence the distribution of pelagic fish. Clearly the reef generates an ecosystem.”
It is that crater that is a bounty for larval fish, Prof Doblin said.
“It creates an upwards lift in the water and helps feed the reef with nutrients,” she said.
“It stimulates plankton and larval fish feed on the plankton.”
The bottom survey forms part of a wider study on linking the oceanography of the region with ecosystem functioning and the marine foodweb.
Scientists on board are researching the impact of the East Australian Current and its eddies on biological processes driven by microbes, plankton and larval fish.
Given the projected increase in the southward extent of the current, determining how the ecosystem is functioning now will help them understand how it will function into the future.
“Given that a change at the base of the foodweb will have a cascading impact on ocean productivity, our research has important implications,” Prof Doblin said.