GALVESTON, Texas — Experts blame lingering warm water temperatures in the Gulf of Mexico for significant bleaching of coral in a marine sanctuary 100 miles off the Texas coast.

Researchers this month determined that nearly half of the coral colonies in the East Flower Garden Bank were bleached or paling, according to the Galveston County Daily News ( ). This year’s bleaching problem is considered the worst in the marine sanctuary’s history, with the next highest from 2005, when about 45 percent of the corals paled during a similar incident.

Flower Garden Banks Superintendent G.P. Schmahl said the bleaching is caused by the coral’s expulsion of the algae that gives it pigmentation.

Experts from the National Oceanic and Atmospheric Administration, who attribute the bleaching to climate change, said sea surface temperatures were recorded at more than 86 degrees for 85 days over four months. The water temperatures should be between 68 and 84 degrees for coral to grow comfortably, according the Flower Garden Banks’ website.

Schmahl said the algae should return when water temperatures cool in the winter. Even with the optimism, Schmahl said, the long period of bleaching could result in corals to starve and die off.

“In recent decades there has been a documented general increase in seawater temperatures associated with climate change and it’s putting coral reefs throughout the world under stress,” Schmahl said.

In July, the Flower Garden Banks experienced a huge die-off. Researchers are still trying to figure out what may have killed many of the sanctuary’s coral and sea creatures, but Schmahl related the event to the fact that heavy rains earlier in the year caused more freshwater from rivers to flow into the Gulf.

The Flower Garden Banks were discovered by a group of fishermen in the late 1800s. They were officially designated as a sanctuary in 1992. The sanctuary, according to its website, is comprised of three banks — East Flower Garden Bank, West Flower Garden Bank and Stetson Bank — about 70 miles to 115 miles off the Texas-Louisiana coast.

Information from: The Galveston County Daily News,