71 Pelican Deaths, Possible Causes Found

ST. PETERSBURG, FL — As the City of St. Petersburg continues to investigate the deaths of 70 brown pelicans and one white one in January, officials say they may have uncovered several factors that resulted in the birds becoming fatally ill. It seems high levels of nitrogen were found in the Riviera Bay Lake retention pond. That issue may have combined with several other factors to create a domino effect of sorts that led to the birds’ deaths.

"There's a significant nutrient impact on this stormwater lake," said Interim Water Resources Director John Palenchar in a Monday, Feb. 6 statement, "A lot of nitrogen was seen in the analytical results that came back from this lake."

The city has been working with independent biologists from Arcadis, along with the Florida Fish and Wildlife Conservation Commission to track down the cause of deaths. Biologists from Arcadis now say the increased nitrogen may have come from fertilizer-containing runoff, as well as animal waste. They also point to the cold-weather that turned the Tampa Bay area frigid during the first week of January.

That cold weather, the city’s statement said, “produced an inversion event.” That means surface water temperatures dropped dramatically and brought oxygen levels in the water down, as well.

“That led to a substantial fish kill in the lake, primarily of tilapia,” the city’s statement said. “Tilapia are mainly freshwater fish, known for an inability to survive in cooler waters, and inhabit shallow streams, ponds, rivers and lakes and less commonly found living in brackish water.” Tilapia also happen to be a rather common food source for pelicans.

"It was very likely some sort of pathogen within the freshwater fish that may have caused this," Palenchar said.

While possible causes have been identified, the city is continuing to study the issue. It is also working to create a plan to remedy the water quality.

"Being able to put in a fountain or a pump could actually alleviate that," he said. "We are asking Arcadis to look at any best management practices or improvements that can be done to improve water quality."

The city is posting the latest findings in regard to the pelican deaths on its website.

Photo by Matthias Liffers via Flickr used under Creative Commons