Published: Aug 30, 2010 4:18 PM EDT
Updated: Aug 30, 2010 1:18 PM EDT

WEST PALM BEACH, Fla. (AP) - A strange upwelling of cold water this summer has caused serious damage to some South Florida coral reefs.

It's not uncommon for cold weather to harm coral - along with pesticides, algae, acidity and other dangers.

But it usually happens in the winter. The bleaching of 70 percent of a large coral patch off Palm Beach County occurred in July, when sudden blasts of cold ocean water subjected the reefs to extreme highs and lows in one of Florida's hottest months.

The upwelling can be caused by winds, eddies and currents, but scientists say is virtually impossible to predict.

Coral reefs are an important part of the ecosystem, providing habitat for marine life and protecting the coast during tropical storms.