Credit: Corbis
The next day, sitting in the ship's common room, Matear explains to me that similar work has already been completed in other parts of the world's open oceans. Research on the acidification of the vast Southern Ocean has produced some of the most alarming results so far.
In most of the world's tropical regions, experts are concerned that acidification will be an additional stress factor on corals already struggling with warming waters, he says, but "the next extreme is that water becomes so corrosive that calcium carbonate becomes unstable and dissolves".
The worrying thing is that Matear's calculations predict that large portions of the Southern Ocean will experience this state when CO2 in the atmosphere hits 600 ppm (parts per million). Prior to the Industrial Revolution 280 ppm had been the norm, today it's 380 ppm, and it is expected to quickly rise to 600 ppm. "That's not far off," says Matear, "we're talking 2050 or 2060 based on current emissions predictions."
"What then happens is, if you have an organism with an aragonite [a form of calcium carbonate] shell, and you put it in that water...it would lose its shell," he says. The pteropods that dissolved in Victoria Fabry's jars are just one such species, and they are one of the most plentiful plankton species in parts of the Southern Ocean, such as the Ross Sea.
Most of the research looking at the effect of acidification on plankton has so far been on pteropods and coccolithophores (a microscopic plant covered in calcium carbonate platelets), but a recent pilot study from the Australian Antarctic Division and the University of Tasmania is the first to show that acidification negatively impacts the development of Antarctic krill, too.
The study found physical abnormalities and decreased activity in the tiny crustaceans, when grown in tanks at the pH expected in the Southern Ocean by the end of this century. It's unlikely such krill would survive to adulthood, says Lilli Hale, an honours student involved in the research.
"Antarctic krill play a key role in the structure and function of the Southern Ocean ecosystem, serving as an important grazer and critical prey item for reproductive successes of whales, seals and seabirds," she adds. It's hard to imagine how species such as the blue whale will survive without the krill on which they rely.
"The potential impact on the dynamics of ecosystems will be very large," says Matear, also based in Hobart with the CSIRO. "But our understanding of these ecosystems at the moment is so poor that it's difficult to make a projection of the scale of the effects."
NCAR's Kleypas likens it to the unfolding global economic crisis: "When one bank fails, then it affects the ability of another financial institution to remain solvent. Because of the interconnected nature of marine ecosystems, a similar domino effect will occur."
The outlook for the Southern Ocean is grim. I begin to wonder what will become of the Great Barrier Reef itself – described by Tilbrook as "the largest living [calcium] carbonate platform on Earth".
Ken Anthony, a marine ecologist at the University of Queensland in Brisbane, says that most existing predictions of the effect of ocean acidification on coral reefs are limited by the fact that they are based on what we know about processes in the open ocean.
The work Tilbrook and Matear are doing will fill an important gap in the data. "This cruise is the first to provide us with a good background understanding of how the chemistry of ocean water changes when it interacts with the reef, and will help us better predict the threat to the Great Barrier Reef," he says.
To really appreciate what we're in danger of losing, I decide I'd better have a look for myself.
