Red tied may have contributed to the deaths of 70 pelicans in St. Petersburg early this year, the Tampa Bay Times reports.
An FWC investigation says a toxin from red tide was found in some of the dead birds, according to the Times.
Nutrients found in fertilizers and human and animal waste are believed to feed the algae blooms that cause red tide outbreaks.
Major storms forced St. Petersburg to release more than 150 million gallons of partially treated sewage into Tampa Bay last year.
But Mayor Rick Kriseman says a company hired by the city to test the dead pelicans found they likely died from botulism poisoning after eating dead fish in a pond -- not red tide.
"We hired a consultant,” Kriseman said. “We wanted to make sure it was an independent company and it wasn't us that was doing the testing and they came back and their findings didn't indicate a connection (to the sewage releases).”
FWC's report also noted the presence of botulism. The agency's investigation is not complete.