Solace seeking in the Southern Ocean

Australian researchers are on a 45-day mission to capture the most detailed picture yet of how marine life in the Southern Ocean stores carbon from the atmosphere. 

CSIRO’s RV Investigator left Hobart early this month on the Southern Ocean Large Areal Carbon Export (SOLACE) voyage. On board were Philip Boyd, his research team and a suite of technology needed to try to find answers in the showers of dead algae and carbon-rich organic particles known as marine snow. 

“The microscopic algae in the ocean are responsible for removing carbon dioxide from the atmosphere as much as the forests on land are,” says Boyd, from the University of Tasmania’s Institute for Marine and Antarctic Studies (IMAS). “When they die, these tiny carbon-rich particles fall slowly to the ocean floor like a scene from a snow globe.”

Boyd is travelling with colleagues from IMAS, CSIRO, the Australian Antarctic Program Partnership (AAPP), the Australian National University (ANU) and Curtin University.

During the voyage, automated ocean gliders and a fleet of deep-diving robots will photograph the density of the algae at different lengths then, once back at the surface, transmit data to the researchers via satellite. 

The fleet is made up of multiple floats from different nations. Each is 1.5 metres tall, with a buoyancy bladder that can be programmed to change buoyancy as it ascends or descends.

Such robots are used frequently, but Boyd and his team have covered theirs in biological sensors. The floats record vertical profiles of temperature and salinity.

“We are excited about how this combination of new imaging sensors will allow us to get a larger and much clearer picture of how ocean life helps to store carbon,” he says. “It’s a bit like an astronomer who has only been able to study one star at a time suddenly being able to observe the galaxy in three-dimensions.”

Two floats will be left in place for four years, including an underwater vision profiler that gives particle sizing of selling particles.

Boyd says that by looking at the density of algae at different depths, the voyage will shed new light on the biological carbon pump.

“We are just beginning to understand how the biological carbon pump works, but we know it helps in the removal of about a quarter of all the carbon dioxide that humans emit by burning fossil fuels.” 

Among those watching with professional interest back in Australia is Elise Tuuri from Flinders University, who explains that the biological carbon pump process starts with “overlooked” phytoplankton. 

“They’re a lot harder to see and be enthusiastic about compared to charismatic animals like dolphins, or exciting ones like sharks, but they play arguably the most important role in our oceans,” she says.

“Phytoplankton’s simplified role in the carbon pump is pulling CO₂ out of the atmosphere, converting this to oxygen. Then when they die, they form marine snow and transport this CO₂ to the sediment. So, they facilitate CO₂ transport from the atmosphere to the ocean and into the sediment.”

Boyd says previous research hasn’t been able to put a firm baseline number on the amount of carbon that is being pumped down into the deep ocean by these organisms during the carbon pump process.

“We know the pump plays a significant role in storing carbon in the ocean, but we don’t know how much as we can’t use satellites to do an inventory of the stocks like we can do on land for carbon storage,” he says. 

“We need to be able to get a baseline for carbon export by marine life as the magnitude of export will change in the coming years due to climate change. If we don’t have a baseline, then we can’t assess how much this pump has been altered.”

If all goes according to plan, the SOLACE voyage will return to dock in Hobart on 16 January, with results to be published three months later.