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By Mike McRae 2 August 2017 4 min read

Bio-Argo float being deployed.

Thanks to an armada of intelligent machines sniffing out our Solar System, we know more about neighbouring planets and moons than ever. Yet in many ways, our oceans have remained as alien as the surface of Titan.

That includes the Indian Ocean. Bounded by Australia’s western coast to the east, southern Asia to the north, and Africa to the west, the Indian Ocean is roughly 70 million square kilometres and covers an area equivalent to about ten Australian continents. Add in an average depth of around 4 kilometres and it’s amazing we know much about this immense body of water at all.

It is home to almost half of the world’s fishers, providing 1/12 of the globe’s total fish production, where churning currents play an integral role in determining the climate of surrounding landmasses, which is home to 1 in 6 people in the world.

Fortunately a roaming flotilla of robots is now helping construct a detailed picture of our planet’s most remote marine environments, including new information from floats in the Indian Ocean.

Probing the Indian Ocean

Argo floats are the ocean’s answer to space probes. Named after the fabled Greek mariners, thousands of these free-drifting devices have been deployed since the turn of the millennium, mapping out the characteristics of the oceans and providing invaluable banks of information on Earth’s climate and global warming.

But they’re not the only robots drifting along on the ocean’s currents.

Scattered among the probes in the Indian Ocean is a separately funded network of floats called Bio Argos, tasked with gathering detailed information on the marine environment’s biological and chemical components.

Nick Hardman-Mountford is a biogeochemical oceanographer with CSIRO. He has been using Bio-Argo floats to gather information from some of the most remote ecosystems on the planet.

two people inspecting float
Dr Bozena Wojtasiewicz and Dr Nick Hardman-Mountford are working with researchers from around the world to develop a global network of 1000 Bio Argos.

“Our floats that have been operating over the past two years have shown us amazing insights into the mechanisms that support planktonic populations and food webs in eddies, the variation of algal growth rates with changes in light and the distribution of oxygen in the ocean,” says Hardman-Mountford.

Each two metre-long float has sensors that can record the water’s temperature and salinity, with many also capable of measuring levels of solar radiation, oxygen, nitrate, chlorophyll and dissolved organic matter. Set free on the ocean currents, the floats are far from passive observers.

“Bio-Argo floats work by diving to up to two kilometres deep and then making measurements as they profile back to the surface, where they send their data via satellites back to our desks. They repeat these cycles every few days and can do this hundreds of times during their lives,” says Hardman-Mountford.

“Between profiles, the Bio Argos park at depth and drift with the ocean currents, covering vast distances over their lives.”

Two floats managed to cover an incredible 70 degrees of longitude between them, drifting a combined distance of roughly 7,700 kilometres. One of them came within reach of Madagascar, the other ending up just north of the nearby island of Mauritius.

A global network

The vastness of the world’s waters once divided distant cultures from one another.

As a shared resource in food and raw materials, the oceans now bind us as a global community, demanding we work together in the name of conservation and to understand the role they play in a changing climate. When it comes to studying the ocean that stretches between them, India and Australia are firm allies.

“We have been working closely with researchers in India to deploy more than 60 Bio-Argo floats in the Indian Ocean,” says Hardman-Mountford.

“Work with our Indian colleagues in the Arabian Sea has mapped the distribution of bacterial populations in zero-oxygen waters, sometimes called dead zones.”

The bacteria are vital when it comes to regulating the ocean’s nitrates. Changes in the microscopic members of the food web could make or break the populations literally millions of people rely on for food and income.

Closer to home, a $62 million facility called the Indian Ocean Marine Research Centre (IOMRC) has been opened in Perth. The centre will bring together the talents and resources of the CSIRO, University of Western Australia, Australian Institute of Marine Science, and Western Australia Department of Fisheries to lead exploration of the Indian Ocean’s ecosystems.

“We are working with researchers from around the world to develop a global network of 1000 Bio Argos that would be able to track rates of oxygen loss and pH change in the ocean resulting from climate change and human CO₂ emissions,” says Hardman-Mountford.

Perhaps in time the swirling gyres of the Indian Ocean will be as familiar as the arid surface of Mars.

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