Science: Slow Growth Rates in the Great Barrier Reef

The skeletons of Porites and other corals provide structure and habitat for the many tens of thousands of species associated with coral reefs.

[Image courtesy of Jurgen Freund of Freund Factory]

Since 1990, the growth of coral in the Great Barrier Reef of Australia has slowed to the most sluggish rate in the past 400 years, researchers say. This finding, reported in the latest issue of Science, could mean trouble for the numerous marine ecosystems associated with the Reef, as well as for other calcifying organisms all over the world.

Glenn De'ath and colleagues investigated 328 colonies of massive Porites corals from 69 different reefs in order to reach these conclusions, and their research suggests that a combination of global warming, declining pH, and decreasing carbonate content in seawater is to blame.

With a growth rate of only about 1.5 cm per year, large massive Porites corals are several hundred years old. Just like tree rings, the annual bands laid down in their skeletons record the environmental histories throughout the corals' live time.

[Image courtesy of Jurgen Freund of Freund Factory]

The researchers say that skeletal records of the coral indicate that calcification, or the deposit of calcium carbonate, by these creatures has declined by 13.3% throughout the Reef since 1990, and that such a decline is unprecedented in at least the past 400 years.

Since these coral reefs are central to the formation and function of ecosystems and food webs for tens of thousands of other marine organisms, the researchers warn that changes in biodiversity and productivity of the world's oceans seem imminent.

Brandon Bryn

2 January 2009