Muddy lake, dead fish -- whodunit?

Pinellas Point denizens point a finger at construction and a drainage ditch, but city officials say the changes were perfectly natural.

By JON WILSON

© St. Petersburg Times, published February 27, 2000

ST. PETERSBURG -- Home to fish, water birds and otters, a small, tree-bordered lake in the Greater Pinellas Point neighborhood provides a backyard pocket of peace for the people who live on it.

They are protective of their haven.

So when Lake Coronado turned muddy and some dead fish floated up this month, residents began contacting officials to find out why.

One suspect: the baseball complex being built on Lakewood High School's southwest corner a few blocks away.

Resident Julia Daniels said she is concerned that dirt from the site washed down a nearby drainage ditch into the lake, muddied the water and caused the unusual fish kill. Neighbors and officials found about 20 tilapia, or Nile perch.

The ditch in question is between the construction site and Lake Vista Park.

City officials say the baseball site shouldn't be blamed. They say a "thermal inversion" -- a water temperature change that ends up stirring up the lake bottom -- caused the lake's problems.

Here's what occurred:

A strong rain pelted the neighborhood the night of Feb. 14, a Monday. Daniels said she thought she smelled dead fish on Feb. 15. On Feb. 16, she pulled about eight carcasses out of the lake.

The lake turned muddier after the storm, although Daniels said some of her neighbors on the lake had mentioned deteriorating water appearing a couple of weeks earlier.

Daniels said that by Feb. 19, she had inspected the construction site. She began to believe the Feb. 14 rain could have washed dirt down the ditch and into the lake.

"Our main concern is the wildlife," Daniels said. "It serves as a barometer for the condition of the lake."

City inspectors found nothing to suggest that runoff from the construction site entered Lake Coronado, said Mike Connors, the city's stormwater director.

Temperature inversions happen perhaps half a dozen times yearly in about 70 lakes the city maintains, Connors said.

A cold snap or rain can cause them, he said. When they happen, water at the top of a lake cools, becomes denser and sinks to the bottom. Water near the bottom rises to the surface, and the turbulence produces silt and other matter. The water coming up also has less oxygen, thus contributing to a fish kill.

Lake Vista, a small lake a few blocks away, also turned muddy and experienced a small fish kill, Connors said. A temperature inversion probably caused that, too, he said. The drainage ditch at issue does not connect to Lake Vista, Connors said.

Such "rollovers" in lakes also can be caused by wind, said Kevin Riskowitz, the city's water quality laboratory supervisor.

Riskowitz noted that the dead fish all appeared to be of one species. "If you have something very bad in the water, you are going to have all the species die," he said.

A state scientist said a rollover could be the culprit, but she said the phenomenon is more common in the autumn, when water is warmer than it is now.

"Cooler water has a whole lot less oxygen, so a when a cold front comes through, and it's really windy or rainy, that water mixes very quickly within several hours and oxygen levels drop rapidly," said Ann Forstchen, a fish health biologist for the Florida Marine Research Institute.

"But that's usually in the fall," she said. "I'm not saying it couldn't happen (now), but it's much less likely."

Residents are absorbing the theories but want to know more. They aren't convinced that the baseball site isn't at fault -- and they worry about the fields' future effects.

A petition circulating in the neighborhood asks officials to take action to prevent future problems, examine further drainage and erosion from the field, and repair any damage that already has occurred.

© St. Petersburg Times. All rights reserved.