Stressed krill first sign of damage from ocean acidification – ‘We are entering an unknown territory of marine ecosystem change, and exposing organisms to intolerable evolutionary pressure’
By Andrew Darby
7 October 2013 (Sydney Morning Herald) – Turns out it’s the little things we need to worry about in climate change. When they’re in trouble, a great polar ecosystem may be, too. The oceans are now absorbing so much carbon dioxide they are acidifying at an unprecedented rate, according to the International Program on the State of the Ocean. Geological records show the current acidification is unparalleled in at least the past 300 million years, IPSO’s latest State of the Ocean report says. ”We are entering an unknown territory of marine ecosystem change, and exposing organisms to intolerable evolutionary pressure,” it says. The smallest of these creatures in the remote Antarctic marine ecosystem are said to be showing some of the earliest signs of acidification damage. And work by Australian scientists shows greater problems lie in store for the creatures at the centre of the Antarctic food web – krill. Environment Minister Greg Hunt pointed to warnings of increasing ocean acidification as the most important new advice from the Intergovernmental Panel on Climate Change’s latest report. ”In the debate around climate change, research on acidification of the oceans is a particular personal concern,” Mr Hunt said. ”This has been reinforced by the work of Australian scientists, particularly in the Antarctic. ”The Southern Ocean is specially vulnerable to increased acidity because of the cold water and the type of marine life. If there are changes in these environments, then there is a flow-on impact across the entire marine system.” The Oxford-based IPSO scientists reported widespread global effects, including the erosion of coral reefs, tipping past their building rates as soon as 2030 to 2050. But they say the rate of acidification is 50 per cent faster in the higher polar latitudes than in subtropical waters, because of the effects of temperature on ocean chemistry. ”Think of it like a cold beer at a barbecue,” said Donna Roberts, of the Antarctic Climate and Ecosystems Cooperative Research Centre at the University of Tasmania. ”It holds onto its carbon dioxide bubbles longer. Remember that 40 per cent of all the carbon dioxide going into the oceans goes into the Southern Ocean. It’s going to hit high, and hit hard.” Dr Roberts said work on tetrapod snails showed distinct acidification effects. ”We’re finding evidence that shell structure has been getting softer since 1997,” she said. Similar problems face foraminifera, countless micro-organisms that also rely on calcium carbonate for their structure. But it is the keystone Antarctic species, the shrimp-like krill, that is a focus of concern about future acidification. Biologist So Kawaguchi said krill were already experiencing changing climate stressors such as rising temperatures and changes in their planktonic food production. In an aquarium world with carbon dioxide elevated at predicted rates, krill eggs failed to develop properly, Dr Kawaguchi said. If emissions were to continue to rise, by 2300 krill would be unable to hatch in vast areas of the Southern Ocean. [more]
