Home sweet home: the creatures of ancient underwater volcanoes

PhD student, Beth Flaxman, who was recently onboard the CSIRO research vessel (RV) Investigator, sampled the mysterious creatures of the deep sea. Find out more about how scientists sampled these creatures that call ancient underwater volcanoes home.

On 30 September 2022, myself and 31 scientists and technical staff from the Australian Museum, Museums Victoria Research Institute, CSIRO and Western Australia Museum began our 36-day voyage onboard the CSIRO research vessel (RV) Investigator to the Indian Ocean Territories (IOT) (Christmas and Cocos Islands). This ‘laboratory-at-sea’ can be in operation for up to 60 days without returning to land to refuel, allowing extensive surveying of remote parts of the ocean.

We visited the IOT seamounts because they have not been explored or scientifically surveyed, and recently, the Christmas and Cocos (Keeling) Islands were both designated as Marine Parks. Marine Geophysicists from CSIRO onboard the RV Investigator used multibeam sonar to map the “landscape” of the seafloor, referred to as bathymetry. The high resolution data was used to produce detailed 3D images of the seamounts to enable visualisation of this expansive deep-sea environment. In the deepest parts of the ocean, the sonar can reach a width of 30 km across the seafloor!

A few of my favourite facts that I’ve learned about these seamounts are:

• The seamounts in the region are aged between 50-100 million years old
• They were formed by the spreading of tectonic plates as the Indian, Australian and Indonesian plates moved away from each other
• The Muirfield seamount rises from 4,500 metres to within 17 metres of the surface and was discovered when a cargo ship (MV Muirfield) crashed into it in 1973!
• The Cocos Islands sit atop a seamount that reaches the surface, from 4,900 metres below

Once we had vision of the seamount landscape, the science team chose a safe pathway to deploy a 4-metre beam trawl to collect a sample of fish and invertebrates from these isolated patches of seafloor. It can be very tricky to find a suitable patch to deploy the beam trawl in this environment, given the rocky and craggy texture of the seamounts. Once the trawl miraculously arrived back onboard, all hands were on deck to sort, label and preserve the catch for future research back at the museums.

It was a wonderful experience, particularly for a student, to be in the presence of biologists from a range of disciplines: we had experts in fishes, corals, brittle stars, worms, crustaceans and more! Each day was filled with new facts and enthusiastic discoveries. The unique excitement of deep-sea trawls in unsampled territory is that you truly never know what you are going to find. I can also say that I’ve honed my microscope skills by practising extracting worms from their tiny sediment tubes whilst they sway across the petri dish in rhythm with the waves.

In my master’s and PhD studies, I have made use of the invaluable collections at the Australian Museum, so it was fascinating to see exactly where these specimens come from and the intricate process of preserving and transporting them to the museum, where they will be used for research in the decades to come!

Beth Flaxman, PhD student, Marine Invertebrates, University of Sydney and the Australian Museum.