One of the world’s great natural wonders may be destroyed by 2050, as coral growth rates in Australia’s Great Barrier Reef decline.  It was recently determined that coral growth rates in the Great Barrier Reef were the lowest in 400 years. Coral growth is measured by counting density rings, which is much like counting growth rings in a tree. If the slow growth rate continues, there will be nil coral growth by 2050.

The reason for the current stunted coral growth is thought to be from anthropogenic ocean acidification, which is the result of increased atmospheric carbon dioxide via the burning of fossil fuels. Ocean acidification results as the ocean, which is part of Earth’s natural carbon cycle, absorbs more carbon dioxide, thus increasing world ocean acidity by “reducing ocean pH and carbonate ion concentrations, and thus the level of calcium carbonate saturation.” This increase in acidity impacts oceanic calcifying organisms, such as corals, and “experimental evidence suggests that if these trends continue, key marine organisms—such as corals and some plankton—will have difficulty maintaining their external calcium carbonate skeletons.” From the The Christian Science Monitor:

In mid-December, The Monitor ran a story on research showing that some areas of the world’s oceans are acidifying faster than marine scientists had predicted even three years ago.  The culprit: the excess carbon dioxide that human industrial activity and deforestation are pumping into the atmosphere — and that the oceans are absorbing. (That article came on the heels of another, more-general Monitor article on the topic a month earlier.)

Now comes word that corals along Australia’s Great Barrier Reef have been growing at an increasingly slow pace since about 1990. The process coral colonies use to build their crusty superstructures is called calcification; it’s fallen off by some 14 percent since ‘90, according to a study published in the journal Science on Jan. 2. (You need a subscription to get the full research paper.)

The decline is severe, sudden, and “is unprecedented in at least 400 years,” according to Glenn De’ath, a scientist at the Australian Institute of Marine Science outside of Townsville, Australia, who led the research team.

Dr. De’ath’s team says more work is needed to pin down the relative contributions among several possible causes, including pollution, warming ocean temperatures, and ocean acidification.  But the group says it sees warming temperatures and ocean acidification as leading candidates.

The reason? Declines in coral far offshore were comparable to those near shore, where reefs would be more strongly affected by nutrient or soil run-off from land.

Researchers are concerned about the issue worldwide because it undermines the ability of shell-forming marine creatures — many of which are key links in the marine food chain — to build their homes. And reefs are nurseries and havens for a range of creatures.

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