Bad news for reefs

Ocean acidification could lead to collapse of coral reefs: To better understand the effect of acidification on coral growth decline, Hebrew University scientists led by Prof. Jonathan Erez and Prof. Boaz Lazar at the Fredy and Nadine Herrmann Institute of Earth Sciences, together with Carnegie Institute colleagues Dr. J. Silverman and Dr. K. Caldeira, carried out a community metabolism study in Lizard Island at the Great Barrier Reef in Australia.

The researchers compared calcification rates documented in 2008 and 2009 to those measured using similar techniques in 1975-6. Despite the fact that the coral cover remained similar, the researchers found that the recent calcification rates had decreased by between 27% and 49%. These lower rates are consistent with predictions that took into account the increase in CO2 between the two periods, suggesting that ocean acidification is the main cause for the lower calcification rate at Lizard Island.

While previous studies on individual reef building corals have shown that they lower their calcification rates in response to ocean acidification, in the present study this was demonstrated for the whole community. These findings suggest that coral reefs are now making skeletons that are less dense and more fragile. While they still look the same, these coral reefs are less able to resist physical and biological erosion.

According to Erez and Silverman, "The results of this study show a dramatic decrease in the calcification of the reef, and that it was likely caused by ocean acidification. When the rate of calcification becomes lower than the rate of dissolution and erosion, the entire coral ecosystem could collapse and eventually be reduced to piles of rubble. The collapse of this habitat would ultimately lead to the loss of its magnificent and highly diverse flora and fauna."

This strikes me as a pretty significant study, as I would expect that Lizard Island is a bit less affected by river run off issues than reefs further south.