Corals feel the heat (and the weed)

Sea surface temperatures in the Red Sea are routinely very high, I believe, but there are corals there that cope nonetheless.  There’s a convincing sounding study in Science that indicates their tolerance is approaching its limits:

Sea surface temperature (SST) across much of the tropics has increased by 0.4° to 1°C since the mid-1970s. A parallel increase in the frequency and extent of coral bleaching and mortality has fueled concern that climate change poses a major threat to the survival of coral reef ecosystems worldwide. Here we show that steadily rising SSTs, not ocean acidification, are already driving dramatic changes in the growth of an important reef-building coral in the central Red Sea. Three-dimensional computed tomography analyses of the massive coral Diploastrea heliopora reveal that skeletal growth of apparently healthy colonies has declined by 30% since 1998. The same corals responded to a short-lived warm event in 1941/1942, but recovered within 3 years as the ocean cooled. Combining our data with climate model simulations by the Intergovernmental Panel on Climate Change, we predict that should the current warming trend continue, this coral could cease growing altogether by 2070.

In other coral news, it's reported today that seaweed is encroaching on a significant number of reefs in the Great Barrier Reef, but the reason is said to be poor water quality. However,  I think it’s also worth noting that ocean acidification would be likely to increase that problem.