Florida's Dolphins Are Dying - Why?
By Frontiers
April 19, 2025
5 Mins Read
A phytoplankton bloom harmed marine habitats, reduced the availability of nutritious prey for bottlenose dolphins, and caused a significant increase in strandings and deaths.
In 2013, 8 percent of the bottlenose dolphins living in Florida’s Indian River Lagoon died. Researchers have since found that the dolphins may have starved after a phytoplankton bloom destroyed vital habitats that supported their most nutritious prey. This bloom was fueled by a buildup of nutrient-rich runoff in the lagoon, including fertilizer, septic tank waste, and other human-related pollutants containing nitrogen and phosphorus.
“We linked mortality and malnutrition to a decreased intake of energy following a shift in dolphins’ diets,” said Dr. Charles Jacoby of the Florida Flood Hub for Applied Research and Innovation, corresponding author of the article in Frontiers in Marine Science. “We linked the dietary shifts to changes in prey availability, and we connected changes in prey to system-wide reductions in the abundance of seagrass and drifting macroalgae. These reductions were driven by shading from an intense, extensive, and long-lasting bloom of phytoplankton.”
Signs of trouble
In 2013, scientists monitoring the Indian River Lagoon observed that the dolphin population was in decline. Of the 337 dolphins studied, 64 percent were underweight, 5 percent were emaciated, and 77 died. This death toll was classified as an unusual mortality event.
“An unusual mortality event is a stranding event that is unexpected and involves a significant die-off of any marine mammal,” explained Megan Stolen of the Blue World Research Institute, first author of the article. “The 2013 event was characterized by a marked increase in mortality and widespread evidence of malnourishment.”
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