Marine ecosystems threatened by acidic oceans

Sea level rise and coral bleaching are known impacts of climate change on the oceans, but scientists worldwide are increasingly concerned about acidification of seawater, a subtler effect, but one that is much more damaging to the marine ecosystem and the human food chain.

“The current level of carbon dioxide [CO2] equivalent accumulation in the atmosphere is 430 parts per million [ppm]. If we allow business as usual at the current rate of CO2 emission over the next eight to ten years, we will exceed 500 ppm of CO2 by 2050 and coral reef ecosystems will be extensively and irreversibly damaged, while carbonate reefs will largely disappear,” World Bank marine biologist Marea Hatziolos said. In an attempt to understand ocean acidification and its impact on the marine ecology in Thailand, a team of scientists from Phuket is set to study the problem in preparation to address its effects on the ocean ecology and the human food chain.
“We have observed the death of hard corals for some time and suspect this might be the result of the increase in ocean acidification, which causes the calcium-component coral reefs to disintegrate,” Somkiat Khorwongkiat, of Phuket’s Coastal and Marine Resources Research and Development Institute, said.

“Our research, funded by the European Union, will be the first of its kind to study the direct impact of climate change on the coral reefs in Thailand,” he said.

As the ocean absorbs much of the global CO2, the increase of the gas in the atmosphere from human economic activities means more of it is dissolved in the ocean. As a result, the pH balance of the seawater is disturbed.

“Studies found that the pH in the sea has decreased from 8.1 to 7.8 to 7.9,” Thailand’s renowned marine biologist Thon Thamrongnawasawat said.

“If the trend continues, the pH is likely to reach 7.6 in the next five decades. This means the sea is increasingly acidic.”

Thon said ocean acidification is a subtle and silent danger that may disrupt 400 million years of evolution of marine life.

Coral reefs and many other marine species, which slowly evolved to adapt to gradual changes in the environment, may not be able to cope with the sudden alteration of their surroundings by climate change, he said.

He said studies elsewhere discovered that in acidic areas, even species without a calcium component, such as sea worms, are found to have weaker sperm, causing a decline in their population.

Somkiat said the institute has earlier studied the impact of ocean temperature changes on soft coral.

The study found that the differences between the temperature at the ocean surface and that at deeper levels have caused a phenomenon called “internal waves”, which have lead to the death of colourful soft corals.

But he could not conclude that it was the result of climate change because ocean temperatures variations are caused by many factors, including El Nino and La Nina, or the dry and wet cycles.

“Ocean acidification is an obvious impact of climate change,” he said. “I hope our studies will help Thailand formulate the right policy to address the problem.”

Pennapa Hongthong, The Nation, 13 May 2008. Article.

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