The gradual acidification of the oceans through increasing
absorption of atmospheric carbon dioxide is thought to be
potentially bad news for coral reefs. As seawater pH falls, the
saturation level of carbonate ions in the water also declines.
Since reefs are made up of calcium carbonate (from coral
skeletons and other sources) they should be slower to form and
faster to fall apart.  That is the thinking, anyway. But given
that ocean pH is changing very slowly, and reefs form over
millennia, it's difficult to see any effects in the real world.
There is an area of the eastern Pacific off Central America,
however, where the water is more acidic than elsewhere, thanks
to the upwelling of carbon-dioxide-rich waters. Coral reefs in
this region are poorly developed and tend to erode rapidly.
Derek P. Manzello of the University of Miami and colleagues have
analyzed the water chemistry and reef samples from the area.
They report in The Proceedings of the National Academy of
Sciences that the carbonate saturation le