Florida’s coral reefs are facing what could be an unprecedented threat from a marine heat wave that is warming the Gulf of Mexico, pushing water temperatures into the 90s. The biggest concern for coral isn’t just the current sea surface temperatures in the Florida Keys, even though they are the hottest on record. The daily average surface temperature off the Keys on Monday was just over 90 degrees Fahrenheit (32.4 Celsius), according to the National Oceanic and Atmospheric Administration. The re