In a snap, fish can suffocate

By STEPHANIE GARRY
Published July 4, 2007

A Great Blue Heron wades along the shore surrounded by dead fish that littered the shore and the surface of a lake by the landfill off 118th Ave. N. and 40th Street.
	[Times photo: Jim Damaske]

This time of year can be deadly for fish.

When the weather's hot and the rainy season is just starting, fish in small lakes and ponds die and float to the top.

The reason? A phenomenon called "flipping," says Kelli Hammer Levy, an environmental program coordinator for the Pinellas County Watershed Management. It happens like this:

Plants at the surface of a pond produce oxygen as a byproduct of photosynthesis. When the sun is out, they dump dissolved oxygen into the water and keep the fish breathing happily.

But at night, or when clouds obscure the sun like they did yesterday, oxygen is in short supply.

Then, to make matters worse, the lake "flips."

The cooler, denser water on the top of the lake drops to the bottom. Suddenly, all the oxygen is gone from the fish's habitat, and they suffocate. People often see them gulping for air at the surface.

"It happens like a snap of a finger," Levy said.

[Last modified July 3, 2007, 22:26:30]