OceanX Completes 22-Day Roo Rise Expedition Uncovering Rare Deep-Sea Ecosystems

The research team employed high-resolution seafloor mapping, remotely operated vehicle (ROV) surveys, environmental DNA (eDNA) sampling, water-column profiling, plankton surveys, and targeted specimen collection to document the structure and biodiversity of the two underwater features. These complementary datasets covered the seafloor through the upper ocean, creating a comprehensive scientific record of the region.

During the expedition, scientists mapped 12,833 square kilometres of seabed, including 9,333 square kilometres in international waters. Approximately 8,232 square kilometres, representing 64 percent of the surveyed area, was newly mapped compared with existing global and Australian datasets. Researchers also completed eight ROV dives, one submersible dive, nine CTD casts, 15 bongo net deployments, and six XBT deployments, with the deepest CTD cast reaching 3,845 metres. A total of 2,365 samples were recorded, including 329 specimen lots and 528 eDNA samples collected across ROV transects and CTD stations. Tissue samples from 243 specimens representing nine phyla were collected for whole-genome sequencing and genomic reference development in collaboration with the OceanOmics Centre.

Preliminary observations documented extensive sponge gardens and coral communities across Roo Rise, including large habitat-forming species and taxa recognised as indicators of Vulnerable Marine Ecosystems (VMEs). Several surveyed areas supported dense coral and sponge assemblages with diverse associated communities of echinoderms, crustaceans, molluscs, annelids, and fishes. Scientists also identified four xenophyophore morphotypes that may represent previously undescribed species, pending further taxonomic and molecular review. An unusual seafloor habitat consisting of probable early diagenetic carbonate colonised by abundant agglutinated foraminifera was also documented during a Roo Rise dive.

"Roo Rise sits within a region that is globally important for ocean productivity and fisheries, yet its deep-sea habitats have remained largely under-characterized," said Dr. Alexis Weinnig, Science Program Manager and Expedition Coordinator at OceanX. "Over the past 22 days, our team mapped the structure of these seamounts and documented deep-water communities. We also collected samples from the seafloor through the water column. Bringing these datasets together will give scientists and decision-makers a stronger evidence base for understanding this part of the high seas."

The South of Java Island region is shaped by seasonal upwelling and complex oceanographic processes. It is also associated with the only known spawning area for endangered Southern Bluefin Tuna, although the expedition was conducted outside the species' peak spawning season. The collected data will enable scientists to examine interactions between seafloor structure, water-column conditions, and biological communities across the productive open-ocean ecosystem.

Minderoo Foundation and the Minderoo OceanOmics Centre at UWA led environmental DNA sampling and tissue collection to support genomic biodiversity research. The expedition generated 528 eDNA samples from ROV transects and CTD stations, while representative tissue samples from 243 specimens collected during ROV dives will support whole-genome sequencing and genomic reference resources. At Christmas Island, an adjacent Australian marine protected area, eDNA samples were collected from 90 sites, including 20 locations previously surveyed in 2023.

"This expedition lays the groundwork to support genomics-based biodiversity monitoring in one of the ocean's most under-studied and difficult-to-reach regions," said Dr Shannon Corrigan, Principal Research Fellow and OceanOmics Centre Lead at the Minderoo OceanOmics Centre at the University of Western Australia. She said combining Roo Rise datasets with Christmas Island research would help compare biodiversity across different protection levels and provide evidence critical for implementing the BBNJ Agreement while improving understanding of vulnerable deep-water habitats.

Scientists from the Western Australian Museum contributed taxonomic expertise, with voucher specimens to be curated in the museum's permanent collections for future biodiversity research. The expedition also engaged the public through live broadcasts from the R/V OceanXplorer. More than 100 people attended a live event at the Western Australian Museum Boola Bardip, while an earlier broadcast to Christmas Island attracted approximately 80 to 100 community members and Parks Australia staff. The recorded broadcast is now available through the museum's website and YouTube channel.

"The real legacy of expeditions like this lies in the specimens that come back to the Western Australian Museum collections," said Jennifer McIlwain, Director of Science at the Western Australian Museum. She said the collected specimens would provide permanent scientific records and noted the remarkable diversity of coral and sponge habitats across Roo Rise, with each seamount supporting distinct deep-sea communities despite appearing similar on maps.

Around Christmas Island, the onshore programme combined eDNA sampling with community engagement and local capacity building through 13 activities attended by approximately 345 participants. The expedition also gathered baseline plankton and microbial data for research into the Milky Seas phenomenon. Scientists successfully isolated bioluminescent bacteria from radiolarian and zooplankton material collected during bongo net surveys, with further population genomics and physiological analyses planned.

According to OceanX, the expedition's scientific datasets may contribute to future assessments of biodiversity, seamount ecosystems, and ecological connectivity in areas beyond national jurisdiction while informing future area-based management discussions under the Agreement on Biodiversity Beyond National Jurisdiction (BBNJ Agreement). The next phase of research will focus on taxonomic review, eDNA metabarcoding, whole-genome sequencing, and processing of seafloor mapping and oceanographic data. Observations involving potentially undescribed species will be announced following scientific validation and partner approval. Pending a data-sharing agreement, processed bathymetry is intended for submission to the National Oceanic and Atmospheric Administration's National Centers for Environmental Information and global mapping initiatives including GMRT, GEBCO, and Seabed 2030.