Deep-Sea News

First Comprehensive Study of NW Australia’s Deep Corals Completed

Scientists circumnavigate and map the seafloor of the entire mesophotic (deep water) zone in Ashmore Reef Marine Park.

Scientists discovered a sea snake thought to be locally extinct and saw several species such as the great spotted cowrie (Perissersoa guttata) for the first time in the Ashmore Reef Marine Park, off Australia, during Schmidt Ocean Institute's 18-day expedition that concluded this week.

A nautilus swims past the ROV SuBastian on Dive 406 (April 12th 2021). The nautilus is the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species in two genera, the type of which is the genus Nautilus. Principal Investigator Dr Karen Miller from Australian Institute of Marine Science (AIMS) smiles while watching the science camera feed from the ROV SuBastian’s first dive. Dr Karen Miller is leading the expedition that is exploring mesophotic coral at Ashmore Reef. Ashmore Reef is one of Australia’s most important protected Marine Park Areas (MPA’s). It is hoped the discoveries and outcomes for the expedition will provide visibility and new insights into the diversity, ecology, and importance of mesophotic reefs to ecosystem integrity in Australia and around the world.A team of scientists, led by Dr. Karen Miller of the Australian Institute of Marine Science (AIMS), also documented for the first time in high-resolution great diversity in coral-dominated areas, calcareous algal beds, and sponge gardens, and collected samples that will provide understanding into the biology of deep-water corals.

At the end of Dive 406 (Monday April 12, 2021) a short-nosed sea snake or Sahul reef snake and second sea snake species for the day was spotted on Ashmore Reef at 67m. The Ashmore population of Aipysurus Apraefrontalis is functionally extinct in Ashmore's shallower waters, but the discovery of the critically endangered snake in the deeper reef potentially identifies a new breeding population.The science team gained new ecological insights of mesophotic species and communities in depths between 50-150 meters using the underwater robot, ROV SuBastian. “Our observations of the reefs showed the mesophotic zone at Ashmore to be diverse, vibrant, and healthy,” said Dr. Miller. “We found no evidence of coral damage, showing the marine park is helping to preserve this special ecosystem.”

At the end of Dive 406 (Monday April 12, 2021) a short-nosed sea snake or Sahul reef snake and second sea snake species for the day was spotted on Ashmore Reef at 67m. The Ashmore population of Aipysurus Apraefrontalis is functionally extinct in Ashmore's shallower waters, but the discovery of the critically endangered snake in the deeper reef potentially identifies a new breeding population.The robot offered the capacity to look at animals and these underwater areas in great detail, unlike previous deep-water survey methods completed in NW Australia. The dives were streamed live to the public, sharing 148 hours of never-before-seen footage of the Ashmore Reef seabed, and over 500 high-quality specimens were collected to share internationally for further research.

On Dive 409 (Thursday April 15 2021) ROV SuBastian documented a benthic ctenophore on Ashmore Reef.                                                                                                                              “Mesophotic ecosystems are hypothesized to have significant ecological importance, including the potential to reseed shallow water reefs under environmental stress, said Dr. Nerida Wilson, Western Australia Museum. “The ability of these environments to provide a refuge for coral reefs needs critical attention, as all reefs face a range of stressors including a changing climate. However, it may be that mesophotic environments are unique in their own right.”

FK210409 Dive409 20210415 HardCoral 0246Australian artist Ellie Hannon sailed with the scientists in the Artist-at-Sea berth, capturing the beauty of Ashmore Reef in her paintings created on-board. She was also able to paint a panel for the deep-diving robot, SuBastian.

A detail of a gorgonian fans documented by ROV SuBastian on Dive 410 (April 16 2021) on the sea floor of Ashmore Reef. Like other corals, gorgonians have polyps. The polyps have tentacles arranged as a pennate, which means they have one main tentacle with branches off of it, like a feather. They can withdraw into the leathery tissue of the coral.The expedition was led by Australian Institute of Marine Science, and included scientists from the University of Western Australia, Curtin University and Western Australia Museum with support from Parks Australia.

On dive 415 April 21st 2021, ROV SuBastian photographs a sea snake swimming along the sea floor of Ashmore Reef.  Sea snakes were once quite abundant at Ashmore Reef but  in recent decades they’ve largely disappeared. During the expedition a large number of sea snakes have been sited at depths between 50m-150m including a previously thought locally extinct short nosed sea snake.The Ashmore Reef study is the final Australia expedition for Schmidt Ocean Institute’s R/V Falkor after nine unique projects as part of a 16-month initiative. “This expedition was filled with a wealth of discoveries and a fitting final voyage to end our collaboration with the local and international scientific community, exploring the waters around Australia, a continent with rich biodiversity and iconic underwater features," said Dr. Jyotika Virmani, executive director of Schmidt Ocean Institute.

The footage and samples collected will have important implications for the sustainability and protection of these underwater ecosystems and similar habitats worldwide that are in peril because of rising ocean temperatures. You can learn more in their recently published impact report.

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