December 2, 2018
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.
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?
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 700–1200 metres to the base of the seamounts at about 1600–2000 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.
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.