Investigator voyage to explore the iron-deficient Southern Ocean

When a human is iron-deficient, it is often time for a healthy dose of red meat, spinach or iron tablets.

But what about an ocean suffering the same condition?

Sub-Antarctic voyagers: from left, Richard Arculus, Andrew Bowie and Mike Coffin.

Approximately one-quarter of the world's oceans are iron-deficient and the Southern Ocean is one of the worst, described as "anaemic".

But about 40 scientists departing on a voyage from Fremantle to the sub-Antarctic Heard and McDonald islands on Friday think they may have found the ocean's iron-tablet equivalent: underwater volcanoes.

"We suspect that hydrothermally mobilised iron is critical to the growth of phytoplankton blooms, the foundation of life in the Southern Ocean ecosystem," said Professor Mike Coffin, from the Institute for Marine and Antarctic Studies, who is chief scientist of the voyage.

"Moreover, phytoplankton contribute at least half of the oxygen in Earth's atmosphere."


The CSIRO's Marine National Facility research vessel Investigator will travel to the remote islands that lie 4000 kilometres south-west of Perth and 2000 kilometres north of Australia's base at Davis Station in Antarctica.

The regions have been selected because unlike large parts of the Southern Ocean, they have an abundance of marine life, which the scientists believe may be linked to higher levels of iron.

"We've got a fairly strong hypothesis that the iron is supplied through these underwater volcanoes," said Associate Professor Andrew Bowie, from the Institute of Marine and Antarctic Studies and the University of Tasmania.

If the team's hypothesis is correct, Professor Bowie said, it will be the world's first proven link "between solid Earth processes associated with hotspot volcanism and biological processes in the ocean".

Professor Richard Arculus, from the Australian National University, said he was excited to be part of the team of multidisciplinary scientists from around the world, despite retiring from ANU just seven days ago.

"This is one of those things where you are part of a group, planning voyages years ahead. There was no chance, having just retired, that I was going to miss the trip."

As a volcanologist, Professor Arculus' time on the 58-day voyage will focus on determining the interaction between the interior of the earth and the life exploiting what has been put into the ocean from volcanic activity.

"We're hoping to find a number of underwater volcanoes and hot springs ... because [they] put iron-rich solutions into the oceans and the phytoplankton around the Southern Ocean absolutely depends on iron to allow their photosynthetic processes to work," he said.

Underwater or submarine volcanoes can lie anywhere from a few hundred metres to thousands of metres below the surface of the water.

The hottest-known plumes to erupt from submarine volcanoes reach temperatures of 400 degrees.

"Generally, it's very hard to find these hot springs. The way we find them is by the black plume of precipitating chemicals coming out of the mineralised chimneys, using optical sensors underwater," Professor Arculus said.

While the team shares confidence in its hypothesis, Professor Bowie said the expedition would not be easy, because iron levels in the ocean were hard to detect.

"It's essentially a pinhead in 100 Olympic-size swimming pools. If we're trying to detect that iron, we need very sophisticated equipment. We go to the bottom of the ocean, collect samples, bring them to the surface and within a few hours we can say how much iron is in there and we can trace it," he said.

"It's only technology in the last 10 years that has really allowed this."