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A matrix of stony coral Solenosmilia variabilis
The deep-sea coral Solenosmilia variabilis attaches to the exposed rocky surfaces of seamounts. It reaches out out to filter-feed on tiny organisms delivered by passing currents and forms a dense matrix that creates habitat for an explosion of other animals. This voyage will develop methods to map these and other deep-sea corals, around Tasmania and the world, by matching their locations with characteristics of the seafloor. Image: CSIRO

Logo for Seamount Coral SurveyDay 1: Chief scientist and voyage leader, Alan Williams, CSIRO

After waving our good-byes at 08.00, we’re steaming south from Hobart on the Investigator at a rate of 11 knots in 30 knot winds through three-to-five-metre seas.

We’re a multi-skilled team of 40 scientists, technicians, marine park managers and communication specialists, supported by an experienced ship’s crew. While some of us are veteran voyagers – one of our number has notched up more than 90 research surveys – we also have first timers eager to learn the ropes. We’ve had our inductions and spent time this morning getting acquainted, setting up equipment and discussing the exciting science ahead, though an unfortunate few are tucked away in their cabins adjusting to life in motion.

Overall, there’s a salty air of excitement and expectation about the mission ahead. By the end of today we’ll be approaching the Huon Marine Park, 170 kilometres south of Hobart, one of 14 parks in Australia’s South-east Marine Parks Network. Tomorrow, the survey begins.

Voyage leader Alan Williams of CSIRO
Alan Williams with the deep-tow camera system on the wharf at CSIRO Hobart. Image: CSIRO

Tasmanian seamounts: a metropolis of marine life

We’re here because this is a distinctive place in Australia’s ocean environment, and a site of global research interest. Far below us lies a hidden realm of rugged hills and mountains, and a large cluster  of extinct volcanoes, more than 100 in total, recognisable by their conical shape. This area off southern Tasmania – roughly equal in size to King Island – contains the largest concentration of these seafloor features around Australia.

These volcanic seamounts rise 200–500 metres from the seafloor at depths of 1000 to more than 2000 m, and the largest we’ve measured has a base area of 25 square kilometres. They’re a metropolis for sedentary deep-sea animals such as corals and sponges, because they provide the two essentials: a hard surface to attach to, and a supply of tiny prey organisms home-delivered by passing currents. Such accommodation is rare in the deep ocean, much of which is an expanse of shifting sediments. Accordingly, the Tasmanian seamounts host Australia’s most extensive deep-sea coral habitats.

Global interest in deep-sea-coral research

The Tasmanian seamounts and their abundant marine life are globally significant. This, combined with their history of fishing and protection, make our seamount corals survey relevant not only to Australian marine parks, but to researchers and managers of deep-sea marine biodiversity worldwide.

Deep-sea coral communities are vulnerable to direct impacts from fishing, oil and gas development and mining, and also to climate change. We know these corals grow very slowly and that some can live for thousands of years, yet little is known about their capacity to recover from damage.

Tasmania’s seamounts came into focus in the 1980s, when Orange Roughy fisheries developed around New Zealand and Australia. The fishing industry explored the Tasmanian area and discovered many seamounts, but the bigger picture emerged in the 2006 when wide swaths of seafloor were mapped by scientists using multibeam sonar, revealing an extraordinary underwater scene of more than 100 seamounts. The fishing industry agreed to cease fishing an area the size of Bruny Island while CSIRO surveys mapped the area and evaluated the coral communities and the seamount biodiversity more generally. Subsequently, when the conservation importance of the seamount coral communities was fully recognised, the area became the world’s first deep-sea protected area, and is now part of Huon Marine Park.

Seafloor bathymetry map showing seamounts in Huon Marine Park
This bathymetry map showing part of Huon Marine Park shows the conical seamounts rising up from the seabed. More than 100 seamounts have been discovered in the area: the largest concentration found around Australia. Image: CSIRO

Comparing fished, previously fished and unfished seamounts

Some sections of individual, typically shallower, Tasmanian seamounts that held orange roughy were repeatedly fished, removing the coral communities under the fishing tracks. The fact that there are seamounts with contrasting fishing histories – still fished, previously fished and never fished – offers a unique opportunity to make comparisons, and we’ll be doing that on this voyage to better understand how these slow-growing communities recover. We first looked for signs of recovery 10 years ago, but found little new life in the areas where coral had been removed. We’ll also be looking on the many smaller seafloor features between the seamounts, to map the broader distribution of coral communities.

Guided by seafloor mapping from previous surveys, we’ll be flying a deep-tow camera system, specially designed by CSIRO engineers, in more than 100 locations over varying depths and features of this complex seafloor. To validate the biodiversity we see, we’ll also be putting down a small sled to collect specimens of seafloor animals such as brittle stars and crustaceans that wrap their arms and legs around the protective, habitat-forming corals. Many of the animals we find are likely to be species new to science.

From these sampling activities we will provide improved information on what limits suitable habitat for deep ocean corals, and contribute to more accurate predictions about where these communities are located worldwide. We will identify the deepest coral communities to estimate how they might be affected by the changing deep sea climate. We’ll also be searching for some granite pavers (or settlement plates) that we put on the seafloor 10 years ago, to improve our understanding of how rapidly deepwater communities colonise and grow.

Eels near the seafloor at Patience Seamount
Eels swim over deep-sea coral habitat at Patience Seamount in Huon Marine Park south of Tasmania. This is the only known spawning aggregation of deep-sea eels. A powered fishing rod and reel and baited remote underwater video will be used to sample and survey the eel populations during the voyage.  Image: CSIRO

Reely deep fishing on an orgy of eels at Patience Seamount

As well as surveying coral communities, we’re going to use a powered fishing rod and reel, and baited remote underwater video systems, to survey the world’s only known spawning aggregation of deep-sea eels – on the Patience Seamount. This will be an exciting moment for me because it is the first opportunity to learn more about  this ‘orgy of eels’ since first finding them 10 years ago. I’m keen to learn more about the size of the aggregation, their persistence on the seamount, and whether they are in spawning condition at this location year-round.

Marine parks managers getting a taste of life at sea

I’m pleased to welcome on this voyage a group of six people from Parks Australia responsible for managing the marine parks that we will be surveying. This is a great opportunity for these managers to build their understanding of some of the habitats and species protected within the South-east network of marine parks.

For most of them, this will be their first time out on these Commonwealth waters. We’ll be putting them to work on image analysis and biological processing. I know they’re very excited at the prospect. They’ll also be sharing their new knowledge with the public via the Parks Australia website and the recently launched Australian Marine Parks Science Atlas.

Join us live in the Huon Marine Park, 3–9 December

From 3–9 December, we’ll be livestreaming from the Investigator webcams, showing what life is like in an Australian Marine Park. The view from our deckcams will be mostly seabirds and water, but we’ll be switching to underwatercams during the sampling. You’ll be able to ride two metres above the seafloor with our cameras, and see the sights just as we do from the operations room onboard. This will be a truly rare opportunity, and we hope you’ll be able to join us. Keep your eye on this website for further details.

We’ll also be providing daily blogs and social media posts as the voyage progresses, and our onboard videography team will be working on videos to share on our return. We have many enthusiastic specialists onboard, and we’re expecting the unexpected.

Let the survey begin!

Further reading [external links]

Location: 
Voyage date: 
Friday, November 23, 2018
Day: 
1

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