Science News

New Deep-Sea Discoveries in Marine Parks South of Tasmania

New areas of deep-sea coral reef and more than 100 unnamed species – including corals, lobsters and mollusks– have been discovered on undersea mountains in marine parks south of Tasmania.

Scientists and park managers returned to Hobart today after a four-week survey of the seamounts on CSIRO research vessel Investigator led by CSIRO.

The unusual cluster of more than 100 seamounts is world-renowned for its deep-sea corals and diverse marine life. Most of the seamounts are protected in Australia’s Tasman Fracture and Huon marine parks, which are managed by Parks Australia.

For the first time, new technologies enabled scientists to look at rocky habitats between the seamounts that support deep-sea corals, in particular the main reef-building stony coral, Solenosmilia variabilis.

“We surveyed 45 seamounts in total, and crisscrossed seven in detail completing a total of 147 transects covering 200 kilometers in length,” said voyage chief scientist Alan Williams of CSIRO.

“We ‘flew’ our high-tech camera system two meters above the seafloor in depths to 1900 meters, collecting 60,000 stereo images and some 300 hours of video for analysis.

“While it will take months to fully analyze the coral distributions, we have already seen healthy deep-sea coral communities on many smaller seafloor hills and raised ridges away from the seamounts, to depths of 1450 meters.

“This means that there is more of this important coral reef in the Huon and Tasman Fracture marine parks than we previously realized.”

Live imagery from the deep-tow camera systems revealed dense coral reefs, as well as hundreds of animals including feathery, solitary soft corals, tulip-shaped glass sponges and crinoids attached to the seafloor. Their colors ranged from delicate creams and pinks to striking purples, bright yellows and golds.

EM1 Ship track 15Dec heading north image NRUD CSIRO 729x453pixShip track 15 Dec 2018 heading north - image NRUD CSIRO

Bioluminescent squids, ghost sharks, deep-water sharks, rays, orange roughy, oreos and basketwork eels were also seen near the seafloor. And from above the water, an observation team collected data on more than 40 species of seabirds, and several whale and dolphin species.

A small net was used to collect biological samples for identification, and many new species were found, as is expected in such remote environments. A high proportion of the mollusk species collected were unknown.

There were many instances of mutually beneficial relationships among the samples, with brittlestars curled around corals, polychaete worms tunneling inside corals, and corals growing on the surface of shells.

“We now have a huge body of data on the animals that live on seamounts and how their communities change with depth, and have a much broader picture of what lives on habitats adjacent to the seamounts,” Dr Williams said.

“We have identified the precise depth range in which the diverse Solenosmilia community thrives. On the larger seamounts which peak in 1000–1250 m depth below the sea surface, corals dominate the top 100–200 meters.

“Our detailed sampling was on seamounts that were previously impacted by bottom fishing but have been protected since for more than 20 years.

“While we saw no evidence that the coral communities are recovering, there were signs that some individual species of corals, featherstars and urchins have re-established a foothold.”

Head of Parks Australia’s Marine Protected Areas Branch, Jason Mundy, was part of the Parks Australia team that joined the seamounts survey.

“Research voyages such as these are critically important to helping us understand, appreciate and protect Australian Marine Parks,” he said. “The images from this voyage remind us what extraordinary and diverse environments we are protecting in these special places.”

New information collected on the Investigator survey will give scientists a clear, quantitative picture of where and at what depth different species and communities live in these marine parks, and a foundation for predicting their likely occurrence both in Australia and around the world.

Story by Bryony Bennett, NESP Marine Biodiversity Hub

The seamount corals survey involved 10 organizations: CSIRO, the National Environmental Science Program Marine Biodiversity Hub, Australian Museum, Museums Victoria, Tasmanian Museum and Art Gallery, NIWA (NZ), three Australian universities and Parks Australia.

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