"Seawater — increasingly acidic due to global warming — is eating away the limestone framework for the coral reef of the upper Florida Keys, according to a new study. It's something that scientists had expected, but not so soon.

This is one of the first times scientists have documented long-term effects of ocean acidification on the foundation of the reefs, said study author Chris Langdon, a biological oceanographer at the University of Miami.

"This is what I would call a leading indicator; it's telling us about something happening early on before it's a crisis," Langdon said. "By the time you observe the corals actually crumbling, disappearing, things have pretty much gone to hell by that point."

The northern part of the Florida Keys reef has lost about 12 pounds per square yard (6.5 kilograms per square meter) of limestone over the past six years, according to the study published in the journal Global Biogeochemical Cycles. Over the length of the reef, that's more than 6 million tons. The water eats away at the nooks and crannies of the limestone foundation, making them more porous and weaker, Langdon said."

Seth Borenstein reports for the Associated Press May 3, 2016. [2]