FL - Red tide sets manatee deaths along Florida's west coast apart, experts say
Water quality and seagrass health play a big role in marine mammals’ survival anywhere in the state.
Red tide in the water and in the air contribute to manatee deaths on Florida’s west coast, setting the region’s waterways apart from other troubled areas of manatee mortality in Florida, researchers say.
In the long run, the loss of seagrass connects both coasts’ investigations into the marine mammals’ well-being, but, according to Dr. Thomas K. Frazer, dean and professor in the University of South Florida College of Marine Sciences, the reasons behind the decline in water quality can often be linked to different factors.
“The last several years have been very difficult for manatees, for a variety of reasons. Particularly on the east coast, and similarly, maybe to a lesser degree, on the west coast,” he said.
“One of the reasons why we’ve lost so many manatees in the last two and a half years is from starvation. Not boat strikes, but starving to death, due to the lapse in water quality in (Sarasota Bay), which affects their food source."
Dr. Dave Tomasko, director of the Sarasota Bay Estuary Program
Seagrasses, which flourish in shallow water, are the bedrock of coastal marine life. They filter pollutants, act as a nursery to marine life and offer manatees and sea turtles their main food source.
Seagrasses also serve as a canary in the coal mine, their health and vitality an indicator of potential problems. Starting in 2016, seagrass numbers have generally declinedaround the state and specifically in Sarasota Bay; a warning of the decline of the delicate ecosystems along the Gulf of Mexico.
“One of the reasons why we’ve lost so many manatees in the last two and a half years is from starvation. Not boat strikes, but starving to death, due to the lapse in water quality in (Sarasota Bay), which affects their food source,” said Dr. Dave Tomasko, director of the Sarasota Bay Estuary Program, adding the Indian River Lagoon on Florida’s east coast is the epicenter for seagrass loss and manatee deaths.
“It might be as high as 30 to 50 percent of the east coast manatee population basically starved to death in the last two and a half years,” said Tomasko.
Red tide and seagrass loss
Closer to home, in 2018, a massive red tide bloom in the Gulf of Mexico affected marine ecosystems of surrounding communities, contributing to seagrass losses and the highest recorded manatee mortality rate in over a decade, with 824 deaths statewide. Over a third of the deaths were suspected or confirmed to be from red tide toxicity due to inhalation or ingestion of red tide, also known as brevetoxicosis.
That year, Sarasota and Manatee counties reported 82 manatee mortalities, the highest number recorded in a single year. In 2021, manatee mortalities across the state rose to 1,100, before declining to 800 in 2022, and declining again to 442, as of Sept. 1.