Increasing Ocean Acidification Eroding Coral Reefs




Acid levels are increasing in the world's oceans due to higher levels of carbon dioxide in the atmosphere now dissolving into the waters, causing alarm in some scientists who say that it could be potentially disastrous for reef-building marine organisms and for their capacity to produce Earth's breathable oxygen as acidification affects their ability to form skeletons.

"Recent research into corals using boron isotopes indicates the ocean has become about one third of a pH unit more acid over the past fifty years. This is still early days for the research, and the trend is not uniform, but it certainly looks as if marine acidity is building up," says Professor Malcolm McCulloch of the ARC Centre of Excellence for Coral Reef Studies (CoECRS) and the Australian National University.

McCulloch continues: "It appears this acidification is now taking place over decades, rather than centuries as originally predicted. It is happening even faster in the cooler waters of the Southern Ocean than in the tropics. It is starting to look like a very serious issue."Marine animals with chalky skeletons would be at the highest risk as they rely on sea water saturated with calcium carbonate to form their skeletons. With increasing ocean acidification however, saturation levels of calcium carbonate have dropped off, inhibiting their ability to calcify and form skeletal structures.

Representing a third of all marine life, corals and plankton with chalky skeletons are at the foundation of the marine food web and their loss would mean widespread ecological impact. "Analysis of coral cores shows a steady drop in calcification over the last 20 years," according to Professor Ove Hoegh-Guldberg of CoECRS and the University of Queensland, Australia.

"When CO2 levels in the atmosphere reach about 500 parts per million, you put calcification out of business in the oceans," he adds. Currently, atmospheric CO2 levels are presently 385 ppm, rising from 305 in 1960.

"It isn't just the coral reefs which are affected — a large part of the plankton in the Southern Ocean, the coccolithophorids, are also affected. These drive ocean productivity and are the base of the food web which supports krill, whales, tuna and our fisheries. They also play a vital role in removing carbon dioxide from the atmosphere, which could break down."

Even more troubling is the fact that red calcareous algae, which holds the coral edges together in swift currents, are actually beginning to dissolve. "The risk is that this may begin to erode the Barrier of the Great Barrier Reef at a grand scale," Hoegh-Guldberg says.

"As an issue it's a bit of a sleeper. Global warming is incredibly serious, but ocean acidification could be even more so."
::Science Daily

See also ::Centre of Excellence for Coral Reef Studies, ::Hope that Corals Will Withstand Global Warming's Impact, ::Biorock: Stimulating Coral Growth With Electricity, ::Corals Engage in Fisticuffs with Global Warming, ::Coral Die-Offs Are Faster and More Widespread than Previously Thought

Image: ShiftingBaselines.org

Tags: Australia

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