Beware! Ocean acidification poses greater risk, finds study

Even as climate experts and policy-makers assemble for yet another round of climate talks in Bonn, Germany, next week, a battery of 250 scientists from 20 multi-disciplinary institutions in the host country may have some startling revelations to make.

Increasing human activity-induced carbon dioxide emission since the Industrial Revolution has turned oceans 30 per cent more acidic taking a heavy toll on marine organisms both small and big, the German scientists will inform the 23rd conference of Parties of the UN Framework Convention of Climate Change scheduled to begin in Bonn on November 6.

Gigantic carbon sinks, oceans take up about a third of rising carbon dioxide emissions. But when absorbed by sea water, the greenhouse gas triggers chemical reactions, causing the ocean to acidify. This acidification, along with global warming, will not only impair marine life, but also compromise important ecosystem services that oceans provide to humankind.

Though the scientific community has been aware of the negative impact of ocean acidification on marine organisms and ecosystems since the 2000s, the details have started emerging only recently.

“The knowledge gained have been massive in the last 10 years, and half of it came in the last 3-3.5 years,” said Ulf Riebesell, a marine biologist at GEOMAR Helmholtz Centre for Ocean Research at Kiel, who coordinated an eight-year-long research pursuit called Biological Impacts of Ocean Acidification (BIOACID), commenced in 2009.

Riebesell was addressing a team of visiting science journalists.

Experiments and model simulations carried out by the scientists as part of the study clearly indicated that corals, sea urchins, mussels and snails, as well as smaller marine organisms such as certain planktons that build their skeletons and shell from calcium carbonate, will not be able to develop as they did before.

Sea water in the polar regions is so acidic now that it has started corroding skeletons and shells of marine organisms living there. In the Antarctic Ocean, for instance, scientists have found that shells of plankton are 35 per cent lighter than comparable specimens recovered from sediment cores dating back to times prior to industrialisation, the scientists said.

The impact of ocean acidification on plankton, feared to be the first affected, may have serious implications, as these microscopic organisms sit at the base of the food chain and serve as food for fish and other larger marine animals. Even small changes at the base of the food web can have a knock-on effect on higher levels, said Riebesell.

While organisms with short generation times, such as micro-organisms, may be able to adapt to the rapid changes, others may not be.

Another combined effect of ocean acidification and warming will be on survival rates of early life stages of some fish species. This may reduce recruitment of fish stocks and thus affect fisheries yields in the near future.

“The current world climate report indicates clearly that net-zero emissions are a pre-condition for limiting global warming to well below 2 degrees Celsius. However, reducing carbon dioxide emissions alone may not be sufficient. Net removal of carbon dioxide from the atmosphere would have to contribute. This is already technically feasible, but the challenge is to develop and implement them at a larger scale,” said Hans-Otto Poertner, ecophysiologist at Alfred Wegener Institute at Bremerhaven, and BIOACID co-coordinator.

The writer was visiting research labs in Germany at the invitation of the German Academic Exchange Service, DAAD

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