by Kimberly Coombs
In 1998, a mass coral bleaching event resulted from increased water temperatures due to climate change and impacted corals world wide. This event caused much of the coral cover to be greatly reduced as many corals have a narrow set of temperature ranges that they can survive, and most live near their upper thermal maximum; therefore, slight increases in temperatures can have negative affects on coral survivorship. Not much is known about the ability of corals to recover after coral bleaching events or the likelihood of the environment switching to an algae dominated environment.
Graham et al. (2015) conducted a study in order to identify reef recovery, the amount of coral cover being greater than macroalgal cover post-disturbance, or a regime shift, the amount of macroalgal cover being greater than coral cover post-disturbance, at the Seychelles reefs. This study observed 21 reef sites from 1994 to 2011 in which about 90% of the coral cover was lost in 1998. They found that 12 of the 21 reef sites were able to recover post-disturbance, yet it took about 10 years to see any major improvements in the amount of coral cover. On the other hand, the other 9 reef sites switched to a macroalgae dominated environment. Before the mass bleaching event, the macroalgae and coral cover percent were the same between the 12 reefs and 9 reefs, suggesting that the regime shift resulted from coral bleaching. Continue reading