posted on Jul, 2 2004 @ 08:10 PM
I thought it could be a change in temperature, but then I saw this...
"As of now, scientists do not know why the water appears black in satellite and aerial images or whether the water is harming the wildlife. They
speculate that it could be due to an exotic algae bloom, an underwater fountain pushing up sediments from the ocean floor, or possibly chemical and
sediment run-off from the nearby Shark River. Researchers at the Florida Marine Research Institute in St. Petersburg and the Mote Marine Research
Institute in Sarasota are running tests to determine the chemical make-up of the water."