Off southern Tasmania, at depths between 700 and 1,500 metres, greater than 100 undersea mountains present rocky pedestals for deep-sea coral reefs.
In contrast to shallow tropical corals, deep-sea corals dwell in a chilly atmosphere with out daylight or symbiotic algae. They feed on tiny organisms filtered from passing currents, and shield an assortment of different animals of their intricate constructions.
Deep-sea corals are fragile and slow-growing, and weak to human actions resembling fishing, mining and climate-related adjustments in ocean temperatures and acidity.
This week we returned from a month-long analysis voyage on CSIRO vessel Investigator, a part of Australia’s Marine Nationwide Facility. We criss-crossed many seamounts in and close to the Huon and Tasman Fracture marine parks, that are dwelling to each pristine and beforehand fished coral reefs. These two parks are half of a bigger community of Australian Marine Parks that encompass Australia’s shoreline and shield our offshore marine atmosphere.
The info we collected will reply our two key analysis questions: what grows the place in these environments, and are corals regrowing after greater than 20 years of safety?
Explainer: the RV Investigator’s position in marine science
Our eyes on the seafloor
Conducting analysis in rugged, distant deep-sea environments is dear and technically difficult. It’s been a take a look at of persistence and ingenuity for the 40 ecologists, technicians and marine park managers on board, and the crew who present electronics, computing and mechanical help.
However now, after 4 weeks of working around-the-clock shifts, we’re again within the port of Hobart. We have now accomplished 147 transects protecting extra 200 kilometres in size and amassed greater than 60,000 stereo photos and a few 300 hours of video for evaluation.
A deep-tow digicam system designed and constructed by CSIRO was our eye on the seafloor. This 350 kilogram system has 4 cameras, 4 lights and a management unit encased in high-strength aluminium housings.
An operations planner plots “flight-paths” down the seamounts, including a one-kilometre run up for the vessel skipper to land the digicam on every peak. The skipper navigates swell, wind and present to make sure a gentle course for every one-hour transect.
An armoured fibre optic tow cable relays high-quality, real-time video again to the ship. This permits the digicam “pilot” within the operations room to manoeuvre the digicam system utilizing a small joystick, and preserve the view in focus, a mere two metres off the seafloor.
That is an typically difficult job, as obstacles like massive boulders or sheer rock partitions loom out of the darkness with little warning. The best fast ascent, a near-vertical cliff 45m in top, resulted in extremely elevated blood stress and one damaged digicam gentle!
Reaching into their world
Reside imagery from the digicam system was compelling. In addition to the primary reef-building stony coral Solenosmilia variabilis, we noticed tons of of different animals together with feathery solitary gentle corals, tulip-shaped glass sponges and crinoids. Their colors ranged from delicate lotions and pinks to hanging purples, vibrant yellows and golds.
To know the make-up of coral communities glimpsed by our cameras, we additionally used a small internet to pattern the seafloor animals for identification. For a number of of the museum taxonomists onboard, this was their first contact with coral and mollusc species that they had identified, and even named, solely from preserved specimens.
We discovered a raft of undescribed species, as anticipated in such distant environments. In lots of circumstances that is prone to be the one time these species are ever collected. We additionally discovered animals dwelling among the many corals, hinting at their advanced interdependencies. This included brittlestars curled round corals, polychaete worms tunnelling inside corals, and corals rising on shells.
We used an oceanographic profiler to pattern the chemical properties of the water to 2,000m. Though additional evaluation is required, our intention right here is to see whether or not long-term local weather change is impacting the dwelling circumstances at these depths.
A curious function of one of many southern seamounts is that it hosts the world’s solely identified aggregation of deep-water eels. We have now sampled these eels twice earlier than and have been eager to study extra about this uncommon phenomenon.
Utilizing an electrical big-game fishing rig we landed two egg-laden feminine eels from a depth of 1,100 metres: a attainable first for the file books.
In a side-project, a staff of observers recorded 42 seabird species and eight whale and dolphin species. They’ve another set of knowledge in the direction of finishing the primary circum-Australia survey of marine birds and mammals.
Extra coral pedestals than we realise
An essential discovering was that dwelling S. variabilis reefs prolonged between the seamounts on raised ridges all the way down to about 1,450m. This implies there’s extra of this essential coral matrix within the Huon and Tasman Fracture marine parks than we beforehand realised.
In areas that have been revisited to evaluate the regrowth of corals after twenty years of safety from fishing, we noticed no proof that the coral communities are recovering. However there have been indicators that some particular person species of corals, featherstars and urchins have re-established a foothold.
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In coming months we’ll work by means of a sub-sample of our deep-sea picture library to determine the quantity and sort of organisms in sure areas. It will give us a transparent, quantitative image of the place and at what depth completely different species and communities dwell in these marine parks, and a basis for predicting their possible prevalence each in Australia and all over the world.
The seamount corals survey concerned 10 organisations: CSIRO, the Nationwide Environmental Science Program Marine Biodiversity Hub, Australian Museum, Museums Victoria, Tasmanian Museum and Artwork Gallery, NIWA (NZ), three Australian universities and Parks Australia.
Nic Bax receives funding from CSIRO and the Australian Authorities Nationwide Environmental Science Program, Marine Biodiversity Hub
Alan Williams receives funding from CSIRO, NESP Biodiversity Hub, Parks Australia