Baffling black blob floating near Florida

Scientists: Strange 'black water' may be type of algae

A satellite image of the mysterious "black water" observed off the coast of Florida.

MIAMI, Florida (CNN) -- Researchers who have been studying a giant, mysterious area of "black water" in Florida Bay say it seems to be associated with a diatom, a type of algae.

The algae was found in the water, according to Scott Willis at the Florida Fish and Wildlife Conservation Commission, and the black water may be an algal bloom -- an explosion of microscopic marine life. Algal blooms are not rare in Florida waters, but blooms of this size are.

At its peak in February, the black water covered an estimated 700 square miles north of the Florida Keys and west of the tip of the mainland.

The algae does not seem to be killing fish, as some algal blooms -- like red tide -- are infamous for doing. But anglers say the fish they normally find in the area have disappeared. They've also reported the water as looking "snotty," "like sewage" and "nasty."

Florida officials refer to it as a "dark brown-black-green water mass."

Tuesday, Mote Marine Laboratory found there is oxygen in the water column -- it's not a "dead zone," as some had suspected.

A theory that it had something to do with an inrush of fresh water and runoff from a river near the Everglades was discounted by water testing. Another theory is that it might somehow be linked to a recent red tide event near Naples, just to the north.

The area of black water was first noted in satellite images in mid-December.