Beneath the Coral Sea, a chain of extinct volcanoes rises more than 3,000 meters from the ocean floor — ancient, largely unmapped, and until recently, never formally studied in the modern era. These are the Tasmantid Seamounts, submerged peaks that have spent millions of years accumulating life in near-total obscurity.
In October 2025, a team of scientists aboard the CSIRO research vessel Investigator set out on a 35-day expedition into the southern and eastern Coral Sea Marine Park. What they found in those depths had never been catalogued before.
A voyage into the deep unknown
The Ocean Census partnered with CSIRO for a 35-day mission aboard the RV Investigator, running from October 10 to November 14, 2025. Their target: the southern and eastern Coral Sea Marine Park, at depths ranging from 200 to 3,600 meters.
Two ecological features anchored the survey — the reefs of the Marion Plateau and the Tasmantid Seamount Chain. The team also covered the offshore Kenn Plateau, giving the expedition an unusually broad geographic reach.
Most critically, this was the first modern deep-water investigation of the northern Tasmantid Seamount Chain — extinct volcanic peaks that had never been formally studied this way. That gap wasn’t merely inconvenient. It left a significant blank in Australia’s understanding of its own deep-sea biodiversity, one that had persisted for decades without anyone filling it.
Tools of discovery: how scientists surveyed the abyss
CSIRO didn’t rely on a single method. The team deployed towed cameras, eDNA samplers, CTDs (instruments that measure conductivity, temperature, and depth), trawls, and sleds — a toolkit designed to capture life across multiple scales and depths.
One of the expedition’s more methodologically significant goals was comparing extractive and non-extractive survey techniques side by side. Environmental DNA analysis detects species from genetic traces left in the water, and it ran in parallel with traditional sampling throughout the voyage. That comparison will help researchers determine which methods work best for specific questions in deep-sea environments — a question with real implications for how future surveys are designed.
New multibeam seabed mapping was also generated, particularly on the Marion Plateau, where existing data were sparse. Specimens collected during the voyage will support species identification and help build genetic reference libraries for Coral Sea marine invertebrates and fish — resources that extend well beyond this single trip.
What the seamounts may reveal about ocean biodiversity
One of the expedition’s central scientific questions is whether seamounts and atolls support higher levels of local endemicity than continental slopes and offshore plateaus. Put simply: do these isolated underwater peaks harbor species found nowhere else?
The answer matters more than it might seem. If seamounts concentrate unusually high numbers of endemic species, that reshapes how we think about deep-sea conservation priorities entirely.
Researchers are examining how biodiversity shifts across the park’s key ecological features and between its distinct bioregions. Population genomic methods are being used to assess connectivity along the seamount chain — identifying which populations are sources, which are sinks, and how isolated or linked they actually are. The expedition is also testing predictive models that connect physical ocean conditions to deep-water benthic biodiversity, which could become practical tools for surveying regions that are even harder to reach.
From data to policy: shaping the future of the Coral Sea Marine Park
This expedition isn’t purely academic. Its results will feed directly into Parks Australia’s Marine Science Program and, most significantly, into the 2028 Coral Sea Marine Park Management Plan — the document that will govern how one of Australia’s largest marine protected areas is managed for years to come.
Right now, managers lack detailed data on the benthic communities living in the park’s Special Purpose Zones. This expedition was structured to fill that gap with evidence rather than estimates, addressing biodiversity priorities that Parks Australia had already identified as critical.
Funding came from several directions: CSIRO’s Marine National Facility provided sea time, while Parks Australia, Bush Blitz, and The Nippon Foundation-Nekton Ocean Census contributed additional support. The breadth of that collaboration reflects how seriously both the scientific and conservation communities are treating this data gap.
What comes next will take time. Specimens need identification, genetic libraries need building, and models need testing against the new data. But the foundation has been laid. When Australia’s marine park managers sit down to draft the 2028 management plan, they’ll have something they didn’t have before: a real picture of what lives on those ancient volcanic peaks — and what’s worth protecting there.
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