A modest increase in atmospheric carbon dioxide means a big jump in acidity of the ocean.
And many creatures have calcium carbonate shells, which will dissolve in acidic water.
The impact will be drastic: snails, bivalves, squid, and sea urchins all depend on their shells. The sea urchin is “the cow of the ocean,” grazing and feeding others. Microscopic or almost microscopic floating organisms live in the tiny shells that eventually form our limestone landscapes and mountain ranges. Squid have an internal stiffening rod that enables them to use their muscles without collapsing — the “cuttlebone” that we give to caged birds.
Researchers in Australia have detected a 50% drop in the weight of sea-snail shells in the last ten years.
[June, 2008] 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.
“It’s going to affect every part of Australia’s marine environment, every bit of water that’s in contact with the atmosphere,” Howard told the Herald . “If I could sit Kevin Rudd down tomorrow, I would say: this is an inevitable and inexorable consequence of our putting carbon dioxide into the atmosphere. It’s not going to stop. What we need to do quickly is get some research together where you can anticipate the ecological impacts of this.”
… What the scientists are asking is this: how quickly will the oceans reach the point where some vital sea creatures will not survive? How many will be able to adapt to the new conditions? What happens to all this marine life when rising acid levels combine with the rising sea temperatures caused by global warming?
Right now, the best predictions are that within 50 to 60 years, a serious rise in ocean acidification is likely to leave some species struggling to survive, especially corals and creatures with fragile shells.
“There are distinct chemical thresholds and once they are crossed, these organisms’ shells would tend to dissolve,” Howard explains. “As the ocean approaches those thresholds, the organisms’ ability to make those shells are compromised. There is a zero sum game.”
… Even if carbon dioxide emissions are radically reduced now, Howard and Tilbrook explain, the oceans will take hundreds of years to recover. But right now, the biggest cause for concern, says Howard, is that it is starting to look like some of the changes are happening much faster than anyone anticipated.
I give it about ten years.