Ocean Census specimen collection. Photo: Ocean Census / NIWA
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The Bounty Trough is one of the world’s least explored deep-ocean ecosystems.
Earlier this year, an expedition set off to explore this deep underwater rift valley off the Otago coast as part of the international Ocean Census project, under the umbrella of the United Nations Ocean Decade.
In partnership with Te Papa and NIWA, the voyage aimed to fill gaps in our knowledge of what lives in the deep.
Ocean Census scientists sift through a sample. Photo: NIWA / Ocean Census / Rebekah Parsons-King
Hundreds of new species discovered
Onboard the research vessel RV Tangaroa were different sets of traps and samplers as well as a deep-tow camera system to allow the scientists to watch what goes on at depths of up to 5,000 metres. The expeditioners returned with hours of video footage and 1,800 specimens. Hundreds of them are new to science – including a slender, slimy bottom-dwelling fish known as an eelpout.
Two eelpouts new to science were collected in a fish trap set at 2,700 m depth on the Ocean Census Expedition to the Bounty Trough. Photo: NIWA / Ocean Census / Rebekah Parsons-King
The number of new fish species may be countable on one hand, but Dr Rachael Peart expects to identify several new small crustaceans known as amphipods and isopods. They look a bit like tiny shrimp and dominate life in the deep ocean.
Te Papa mollusc curator Kerry Walton has already identified 78 new species of snails and mussels from the Bounty Trough, including a parasitic snail stuck to a gummy squirrel – a weird sea cucumber with a large sail-like extension.
Gummy squirrel with parasitic snail attached. Photo: Thom Linley
Te Papa fish curator Andrew Stewart says the museum’s collection is limited to shallower depths of about 1,200 metres and mostly commercial species. Being able to explore the Bounty Trough opened up a treasure trove of sightings and catches from the deep.
It also brought home the importance of ocean life.
“This is the world’s largest habitat, by a vast margin. It plays a massively important role,” he says. "We really need to know what’s down there because shifts down there are the canary in the coal mine. We lose those, we’re in trouble. Maybe not today, maybe not tomorrow, but we’re in trouble.”
Why explore the deep sea?
Professor Alex Rogers, the science director of the Ocean Census programme, says there are many reasons why we need to know what lives in the deep.
About half of the oxygen we breathe is produced by tiny plants that live in the ocean. They also kick off the marine food web – from microorganisms to fish – which ultimately feeds millions of people.
The view from the deep towed imaging system (DTIS) during a tow on the Ocean Census voyage to the Bounty Trough. Photo: NIWA / Ocean Census / Rebekah Parsons-King
As if that weren’t enough, the ocean also buffers us from the worst of climate change by taking up more than 90% of the excess heat we produce from burning fossil fuels and about a third of our emissions of carbon dioxide. It’s Earth’s largest carbon sink and life support.
And yet, we still don’t understand life in the ocean very well. Of an estimated two million marine species, we’ve so far identified only about a tenth.
“Many marine species are in decline,” he says. “We need to understand the distribution of life better in the ocean in order to halt that decline and to eventually turn it around to recovery.”
Learn more:
- For more ocean-themed stories, listen to Voice of Tangaroa.
- Claire Concannon meets some researchers exploring the deep sea in search of squid in The world through squid eyes.
- Alison Ballance learned all about deep-sea corals for this 2020 episode.
