December 2, 2018

Cath Samson on deck
Cath Samson enjoys good weather in the Huon Marine Park  off southern Tasmania. Image: Bethany Green/CSIRO

Day 10: Cath Samson, Senior Marine Parks Officer Science, Parks Australia

We're at Sisters Seamount in the Huon Marine Park. We're 70 kilometres from South-East Cape on the South Coast of Tasmania so walkers climbing Precipitous Bluff on a clear day may be able to see Investigator on the horizon. It's a lovely calm, sunny day which everyone aboard is enjoying after the rough seas and grey skies at the start of the voyage.

In the 1980s and 1990s, fishermen braved these often hostile waters in search of orange roughy, a deep-water species found in spawning and feeding aggregations on and around seamounts in southern Australian waters. This was once one of Australia's largest and most valuable fisheries. Unfortunately, the use of bottom-trawl gear by the fishery damaged some areas of the fragile deep-sea coral communities.

Orange roughy on a seamount
Orange roughy and oreos swim above the deep seafloor. Image: CSIRO

In recognition of the environmental importance of these seamounts the fishing industry introduced a 370-square-kilometre no-trawl zone in 1995. Following the first scientific survey of the area in 1997, which demonstrated the uniqueness of these seamount communities and the impacts of trawling on them, the no-trawl zone was formally declared the Tasmanian Seamounts Marine Reserve in 1999. This reserve was later incorporated into the much larger Huon Marine Park when the South-East Marine Parks Network was declared in 2007.

In 2007, a second scientific survey in 2007 showed no clear signal of recovery in the deep-sea coral communities on seamounts where trawling had ceased five years earlier. Life grows very slowly in the deep sea: there's no light, little nutrients and it's very cold.

Eleven years on, scientists are back again. This time the marine park managers are also on the voyage. Will we see signs of recovery in these spectacular, slow growing and globally significant deep-sea coral communities?

Solenosmilia corals and urchins os seafloor
Extensive thickets of the hard coral Solenosmilia and sea urchins on the 'Hill U' seamount . Image: CSIRO
Two technicians operating the deep-tow camera system
CSIRO's Mark Lewis and Aaron Tyndall (in the pilot's seat) concentrate on flying the deep-tow camera system over coral thickets. Image: Parks Australia/CSIRO

To answer this question we will do a total of 40 deep towed-camera transects on: (1) seamounts that were once trawled but are now closed to trawling, (2) seamounts that are still trawled, and (3) seamounts that have never been trawled.

Much interest surrounds each 'flight' of the deep-tow camera system. A large crowd gathers around the screens displaying the underwater video and we wait in suspense while the camera descends through the inky depths wondering what we will see. Suddenly the top of the seamount looms out of the darkness. "We're on the bottom and starting the transect," the camera operator tells the ship's captain over the radio.

The ship's captain and camera operator work in tandem to guide the camera along pre-determined transects two to three metres off the seafloor, taking photographs and footage of the unique and diverse marine life on the seamounts. It is not an easy task to keep the camera in the correct position with wind and waves buffeting the ship, surface and deep currents often pulling the ship and camera in different directions, and the conditions changing as the camera descends from the top of the seamount at depths of about 7001200 metres to the base of the seamounts at about 16002000 m.

The one noticeable thing about the video transects so far is that the each is quite different, and there is also variation with depth. We have seen extensive Solenosmilia hard coral thickets, spectacular soft coral gardens, big black corals and large schools of orange roughy, oreos and basketwork eels and relatively barren areas of sand and rock.

Seafloor habitat with a quadrat marked
Seafloor imagery is marked into quadrats for analysis. It will take months for scientists to build a picture of how life on the seafloor has changed. Image: CSIRO
Cath Samson image-processing
Hands on management: Cath Samson gets acquainted with life on seamounts in the Huon Marine Park. Image: Bethany Green/CSIRO

Collecting the images is just the first part of the job though. Having obtained many hours of video and several thousand photographs, they need to be analysed. On previous voyages image analysis has been undertaken back in the lab but on this voyage we are undertaking the first stage of image analysis on the ship. This is my role on the voyage. Like a lot of science its a repetitive task but a very important one to enable the exciting part of science to occur and be told. It will be several months before scientists complete the data analysis and can tell us what changes have occurred in the past decade.

As a park manager, I am really excited to get the opportunity to see the video footage as its collected: to see and understand first hand what's in the marine parks. I have learnt so much about the unique and diverse marine life on the seamounts from chatting with scientists over lunch and dinner. On my shift, breakfast is at 2 am so there's less conversation then!

Monitoring programs such as the Seamount Corals Survey, that take repeat measurements at regular time intervals, are critical to understand environmental change and supporting the management of Australian Marine Parks. This voyage will help us better understand the deep-sea coral communities, in particular their recovery.

The data coming out of this voyage will be of global importance. This voyage marks more than 20 years since the seamounts were first systematically surveyed, providing an important long-term dataset about our ocean depths. Repeat surveys in the deep-sea are very rare because deep-sea research is difficult and expensive to conduct.

Diverse seafloor life at little sisters seamount
HIgh diversity at Little Sisters seamount. Image: CSIRO

Notes on today's activities from Marine Biodiversity Hub Director, Nic Bax . . .

With a low pressure system careering our way and promising seas of six metres or more, there has been a concerted effort over the last 24 hours to finish our towed video transects on the seamounts in this area. While we can operate the beam trawl and Sherman dredge in higher seas (up until the time when it is no longer safe on deck for the crew to deploy and retrieve gear), towed camera quality is more sensitive to the heave of the ship and, as we have found out, the high technology camera equipment does not take kindly to swinging against the stern as it is brought aboard.

By 1400, we had completed six more tows leaving us tantalisingly close to finishing the eight transects per seamount (fished, protected and never fished) in this area. Just one transect remains, but with the seas coming from the side, the ship would not have been able to hold position at the slow towing speed we need for the camera. We now have more than 20,000 paired stereo images from the towed video, so we will have a lot of data to process once we return to land. Fortunately we will not be identifying, counting and measuring the coverage of the marine animals in all pictures – we subsample the images so that each image can be assessed as independent from the one that preceeded it.

We turned our attention to redeploying the two Baited Remote Underwater Videos Systems (BRUVs) on Sisters seamount at about 900 m depth. Then off to Mongrel, the small parasitic cone off Pedra Seamount, for a benthic tow to provide more specimens for the biologists. But the weather beat us to it, so now we are steaming westwards at 6 knots towards Maatsuyker (ETA 02:00), when I expect that we will turn around and come back again – using the multibeam mapper all the way to fill in this area that is missing from our high resolution topographic maps. This will almost undoubtedly highlight some new seamounts (in the biological sense of the term, i.e. not necessarily >1000m high), knolls and ridges which are likely areas for more deep sea coral.

Meanwhile our species specialists on board have been working hard with the tally for marine bird species increasing to 37, while the last beam trawl produced over 150 species of small molluscs, most undescribed, and potentially including one new family.

Christmas decorations went up in the mess yesterday. A pod of 60–80 long-finned pilot whales swam by the ship today providing excellent photo opportunities.


Voyage date: 
Sunday, December 2, 2018