By Ian Williams, NBC News correspondent
Will Howard used to think the biggest threat to the World's oceans came from the things you could see - like the detritus clogging so many our estuaries and coastal regions. Now he's found new evidence of how invisible changes in the chemistry of the water pose a disturbing new threat to life in the oceans.
"The impact has already begun. It's not a matter for laboratory experiments. It's happening now," he told me.
The world's oceans are becoming more acidic, as they absorb carbon dioxide from the atmosphere, and Howard has discovered the first direct field evidence of the impact on marine life - tell-tale changes in tiny sea snails the size of a grain of sand, which are struggling to make their shells.
"These organisms are the base of the marine food web, and what happens to them reverberates throughout the eco-system - right up to whales and penguins," says Howard, who's based at the Antarctic Climate & Ecosystems Cooperative Research Centre at the University of Tasmania.
It was the raw beauty of this remote corner of Australia that drew Howard here from his native New York fourteen years ago. He came on a short-term research project and never left.
I met him in his Hobart laboratory, where researchers weighed the shells of sea snails collected from deep beneath the southern ocean, which separates Australia from Antarctica. The weight had fallen by up to half in a decade.
"The fact that we are seeing it now, that it's already happening, came as a bit of a surprise to us," he says. "If these organisms are seeing the impact, the rest of the system can't be far behind."
The oceans naturally absorb carbon, and have been seen as a buffer against climate change. Around half the carbon dioxide pumped into the atmosphere is absorbed by the oceans, and scientists say acidity levels have risen thirty per cent in the last 100 years. The impact has been faster in the cold waters of the southern ocean, which is why it is such a good laboratory, and why Tasmania-based scientists have been at the forefront of this emerging research.
They believe the oceans' natural processes are now being overwhelmed.
"We're just pumping carbon into the ocean at too rapid a pace for the system to adjust itself and offset this problem," according to Bronte Tilbrook, who heads an acidification project a the Australian government's Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Hobart.
Shell-making is one the processes by which carbon is absorbed and then transferred to the depths of the ocean, and if this is inhibited, so ultimately might be the oceans ability to buffer against climate change.
"So if they're not making shells, it means the mechanism that transfers carbon from atmosphere to the ocean depths is also altered," according to Howard.
What's more difficult to predict is just how quickly the rest of the eco-system might be affected by the changes, though Ron Thresher, another New Yorker now based at the CSIRO in Hobart, thinks we will soon have a clearer picture thanks to ground-breaking research on recently discovered reefs near the Antarctic shelf.
In January, an unmanned submarine, the Jason, was able to collect the first coral samples from highly acidic water up to ten thousands of feet beneath the ocean.
"Look, you can see the effects of acidification," he said, handing me a small piece of coral, which started to disintegrate like a piece of chalk as I rubbed it. "See how fragile it is. It's flaking away."
The submarine collected live coral from a depth of around four thousand feet; below which the coral began to die off. Thresher calls this the "saturation point", the point at which the acidity is so high, the reef can no longer live, and the point is moving higher as more and more carbon goes into the ocean.
Coral reefs are vital marine habitats - nurseries for thousands of fish.
"As these things die off, all the associated things that live with them can't survive either," Thresher told me as we stood in front of a large cupboard stacked with coral.
It's early days, but he now believes his coral samples will yield more precise information than ever before about the pace and impact of acidification on marine eco-systems.
"It will enable us to predict the ultimate fate of these things," he says, and possibly draw up strategies for mitigating the effects.
Before we left Australia, we visited Sydney, where we wanted to catch up with a young PhD student at the University of Western Sydney. Laura Parker was suddenly thrust into the scientific limelight when she discovered abnormalities in the shells subjected to rising levels of acidity in the laboratory.
"It was a bit scary," she told me. "Because oysters are bioindicators, so anything that happens to tem might happen to other organisms in the environment."
Rock oysters are also big business in Australia - worth US$30m a year in New South Wales alone, and Parker's findings not only re-enforced the Hobart research, but is a reminder - a wake-up call to the more hard-headed - that there also the serious economic issues at stake.
The Hobart research has led to an extraordinary meeting of Australia's leading marine scientists - and a call for more and urgent global research.
When Howard isn't pouring over his microscope in his lab near Hobart's spectacular harbor, he often found sailing along the coast, where the abundance of life - from birds to penguins and dolphins, is a reminder to him of why he settled here, but also of just how much is at stake.
He and Thresher believe they've found the ocean equivalent of the "canary in the coal mine" - an early warning, of what is fast emerging as the biggest threat to our oceans.