The Great Barrier Reef is declining
Seema Singh -
Friday, January 02, 2009 7:00 AM
In yet another blow from the warming climate, the world's largest coral reef system, the Great Barrier Reef of Australia, is on a decline.
One of the wonders of the natural world, which comprises more than 3000 reefs, has had the slowest rate of growth in the past 400 years, says a new study in today's issue of Science.
Researchers from the Australian Institute of Marine Science provide the first rigorous picture as well as empirical data on how increased carbon dioxide in the atmosphere is changing the way coral reefs absorb calcium from seawater to calcify (and harden) their skeletons.
This finding could mean trouble for the numerous marine ecosystems associated with the Reef, as well as for other calcifying organisms all over the world.
In their study, Glenn De'ath and colleagues investigated 328 colonies of massive Porites corals from 69 different reefs. Their work suggests that a "combination of global warming, declining pH, and decreasing carbonate content in seawater is to blame."
Massive Porites are distributed throughout the tropical and subtropical Indo-Pacific. The picture above is of a colony growing in shallow waters of the Great Barrier Reef. Image courtesy: Jurgen Freund of Freund Factory
Like trees, corals have annual growth bands that make it possible to go back calculated years in time and correlate with sea surface temperature and other environmental data during the same period. Calcification in these creatures has declined by 13.3 % in the last 20 years, which is unprecedented in four centuries.
In the early 1990s marine scientists had predicted that ocean acidification might one day threaten corals. But in July 2008 at an International Coral Reef Symposium they gave the people about 10 years to pull up their socks. But this finding suggests perhaps they were too generous: the threat engulfed the corals more than a decade ago!
Since coral reefs are part of the food chain for tens of thousands of other marine organisms and are central to the marine ecosystem, researchers warn that the productivity of the world's oceans would change.
See and read more about the Reef here: