December 5, 2010

Acidification Threatens Already Over-stressed Oceans

The world's oceans are facing far-reaching implications for its marine biodiversity and food security, due to changes in their chemistries not seen in more than sixty million years, according to a new study released by the United Nations on Thursday.

"Environmental Consequences of Ocean Acidification," published by the UN Environmental Program (UNEP), warns that some sea organisms including coral and shellfish will have an increasingly difficult time surviving, as acidification shrinks the minerals needed to form their skeletons.

"We are seeing an overall negative impact from ocean acidification directly on organisms and on some key ecosystems that help provide food for billions. We need to start thinking about the risk to food security," Carol Turley, from the UK's Plymouth Marine Laboratory, and lead author of the report, said in a statement.

Coral reefs provide shelter and food for nearly a quarter of all known marine fish species, according to the report, while more than one billion people rely on many of those same fish species as a key source of protein.

The increasing acidification is likely to affect the growth and structural integrity of tropical coral reef, and, coupled with ocean warming, could limit the habitats of crabs, mussels, and other shellfish with a rippling effect up and down the food chain.

The report, unveiled during the UN climate talks in Cancun, Mexico, states that about 25 percent of the world's CO2 emissions are currently being absorbed by the oceans, where they are turned into carbonic acid.

PH levels in oceans around the world have fallen by an average of 30 percent since the Industrial Revolution -- beginning in the 18th century. The report predicts that by the year 2100 ocean acidity will increase 150 percent, if the emissions continue to rise at the current rate.

Scientists say, however, that not all marine species will be affected negatively with the growing acidification in the oceans.

Adult lobsters may increase their shell-building as pH levels decline, as might brittle stars -- a close relative of starfish -- but at the cost of muscle formation.

"The ability, or inability, to build calcium-based skeletons may not be the only impact of acidification on the health and viability of an organism: brittle stars perhaps being a case in point," Turley said in a statement to CNN

"It is clearly not enough to look at a species. Scientists will need to study all parts of the life-cycle to see whether certain forms are more or less vulnerable," he added.

Scientists are more certain about the fate of photosynthetic organisms such as seagrasses, saying they are likely to benefit from rising acidification and that some creatures will simply adapt to the changing chemistry of the oceans.

The authors of the report said policy makers need to consider certain measures in fighting the loss of pH levels in the world's oceans, including rapid cuts to CO2 emissions and assessing the vulnerability of communities that rely on marine resources.

"Ocean acidification is yet another red flag being raised, carrying planetary health warnings about the uncontrolled growth in greenhouse gas emissions. It is a new and emerging piece in the scientific jigsaw puzzle, but one that is triggering rising concern," Achim Steiner, UNEP executive director, said in a statement.


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