Acidification from fossil fuels is killing our oceans

In a Hobart laboratory a few weeks ago, a young marine biologist placed the shell of a tiny sea snail on a weighing scale and held her breath. Donna Roberts's critical experiment rested on getting the exact weight of this fragile specimen; any movement in the room could instantly throw off the delicate scale, so sensitive it is called a microbalance.

Roberts had been weighing 100 of these shells, stripped from snails that had been collected from the depths of the great Southern Ocean half way between Tasmania and Antarctica.

The snails, known to biologists as pteropods, swim through the sea like butterflies. They are as abundant as krill and help feed the ocean's huge schools of fish.

The shell specimens dated back to 1996 and the earlier ones had weighed in at 20 micrograms. But Roberts observed that as the specimens became more recent, the weight of the shells had fallen. When her last specimen, from 2005, weighed in at just 10 micrograms, Roberts barely dared to breathe.

"Wow, what is going on?" she asked herself. A halving of shell weight in just one decade was a real worry.

Roberts's still unpublished research is just one reason why her collaborator, Dr Will Howard, from the Antarctic Climate and Ecosystems Cooperative Research Centre, this week convened an extraordinary meeting of Australia's leading marine scientists in Hobart.

For three days, the 50 scientists, along with colleagues from America and New Zealand, focused their collective minds on a threat that has emerged, it seems, from out of the blue: the growing acidification of our oceans.

These scientists now know that burning fossil fuels and massive land clearing are not just warming the planet and raising sea temperatures, they are also changing the chemical make up of the oceans. A vast amount of the carbon dioxide humans have pumped into the atmosphere since the industrial revolution has been absorbed by oceans.

A new report by the Antarctic research centre, released at the Hobart meeting, says that about half the fossil fuel carbon dioxide released into the atmosphere by humans has now dissolved into the oceans. If we keep pumping carbon dioxide into the atmosphere at the current projections, by 2100 the ocean acidification will be three times that experienced at the end of the glacial period, 15,000 years ago.

The chemistry is basic. The ocean is a weakly alkaline solution. When carbon dioxide sucked in from the atmosphere dissolves in sea water, it forms a weak acid, making the ocean more acidic. For sea life with fragile shells, corals and countless other sea creatures, a more acidic ocean could be disastrous and have unknown impacts right up the marine food chain.
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Our oceans have absorbed so much CO2 they will one day no longer be able to sustain life if we continue on the path we are on. What we do to other species we do to ourselves.