More than 430 manatees have perished in 2021. Why are they dying? Scientists are searching for answers as to why more Florida manatees have died in the first two months of 2021 than in most of 2020. Native grasses which once lined the bottoms of Florida’s springs—such as Fanning Springs, pictured here—are being choked out by algae fed by fertilizer and nutrient runoff. This lack of vegetation is causing many manatees to starve to death in the winter. ByRebecca Renner Email Early this past winter, Martine de Wit noticed a spike in the number of manatees that were dying. At first, the veterinarian with the Florida Fish and Wildlife Conservation Commission attributed the surge to cold stress. De Wit was used to seeing some manatees sickened by the strain put on their sensitive bodies when water temperatures dip below 68 degrees Fahrenheit, as they did several times in December and January.