Fish Kill Zone Widens; Algal Bloom Suspected

New fish kills were reported in Old Tampa Bay Thursday, widening the death zone miles beyond the original kill reported at Courtney Campbell Parkway over the weekend.

The latest fish kill was reported at the mouth of Allen's Creek in Largo, roughly two miles south of the causeway. Dead fish also were reported at Philippe Park in Safety Harbor, about three miles north of the causeway.

"The kill is continuing," said Theresa Cody, a research scientist with the state Fish and Wildlife Research Institute. "It tells me it's ongoing, but there is a lot of difference between Philippe Park and Allen's Creek, so I guess it's a pretty widespread problem."

Cody blamed low oxygen levels for the widespread kills. Water samples taken Wednesday and Thursday revealed dissolved oxygen levels well below the danger level of 5 milligrams per liter.

Bernie Banull of Safety Harbor took pictures of dozens of dead and dying stingrays at Philippe Park as well as other struggling fish. He said mullet were swimming on top of the water and appeared to be gasping for breath.

Fish and Wildlife researchers think an algal bloom is causing the low oxygen levels. Higher-than-normal amounts of algae called Rhizosolenia setigera and Pseudo-nitzschia are present in the bay. The algae produce oxygen when the sun is shining and use oxygen at night.

Nitrates and phosphorus, carried into the Bay by stormwater runoff, can fuel the algal blooms and overcast skies can limit the amount of oxygen the algae produces in the day.

Scientists say red tide, another algal bloom that kills fish and causes respiratory distress in human, is not responsible for the fish kills. Water sampling last week showed no red tide in the Bay.

Cody also said that high levels of bacteria, which caused authorities this week to close the swim area at Ben T. Davis Beach and shut down Courtney Campbell Parkway beach, are not responsible for the fish kills.

The first fish kill at the causeway was reported to Fish and Wildlife officials Sunday. By the time research teams investigated Monday, the fish had been dead too long to get fresh samples needed for necropsies.

Thursday, however, scientists were able to collect several stingrays, sea trout, drums and pinfish. Necropsies performed today could determine what caused the kills.

"They were definitely behaving abnormally," Cody said. "Based on the water quality, the low dissolved oxygen, I would definitely say they're having problems breathing."

Results from samples and necropsies could take up to two weeks.

Carli Segelson, an institute spokeswoman, said it is not unusual for stingrays to be affected by the algae.

"This is a multispecies fish kill, and these stingrays were in the area at the time," Segelson said. Pinfish, king fish, sea trout, and blue crabs also were reported dead at the two locations.