"Assessing Evidence of Phase Shifts from Coral to Macroalgal Dominance on Coral Reefs"
Ecological Society of America, June 2009
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"Our database included 3,581 quantitative surveys of 1,851 coral reefs (or sites) performed between 1996 and 2006. Our analysis was based on quantitative surveys that measured the percentage of the substratum covered by living coral and fleshy or calcareous macroalgae between 1 and 15 meters depth."
[A simplified version of Table 1]
Caribbean -- Corals: 20%, Algae: 23%
Florida Keys -- Corals: 8%, Algae: 15%
Indo-Pacific -- Corals: 33%, Algae: 12%
Great Barrier Reef -- Corals: 31%, Algae: 9% "
"Overall, our results indicate that there is no general recent trend (i.e., post-1995) toward macroalgal dominance."
"Macroalgal cover on these 'pristine' reefs is similar to the regional averages for three of our four study regions, suggesting that macroalgal cover may currently be close to the historical baseline across most the world."
"Macroalgal cover and coral cover are widely assumed to be causally linked and inversely related. Yet we found only weak negative relationships between coral and macroalgal cover. Surprisingly, macroalgal cover has not increased appreciably on most of the world’s reefs that have very low coral cover. For example, 379 of the 1,851 reefs had less than 10% coral cover, but macroalgal cover was also low (less than 20%) on nearly two thirds of these reefs. In fact, more than half the benthic cover on reefs in the Caribbean, Pacific and Indian Oceans consists of organisms other than hard corals and macroalgae, possibly because other taxa, such as sponges and gorgonians, have been the primary beneficiaries of coral loss."
