Hi, I have been diving down here since the 60's and the water temps have remained steady thru the years. The one main thing that has changed is the amount of people and all the pollution they bring. Do you remember all the septic deep well injection systems they had in the Keys, and all the sewage that leaked into the Atlantic Ocean, this is not including all the Big Sugar, farm and cattle run off going into Florida Bay and then into the Atlantic Ocean thru all the cannels in the Keys and around Key West. Believe me, it's the man made pollutionI don’t doubt that pollution is a problem, probably the underlying reason for all the red algae problems; but the enemy of stag and elk horn corals has been high temperatures causing bleaching and white band disease problems.