There has been a lot of attention on how climate change is affecting Polar regions, however it appears that global climate change may have devastating effects on warm water animals as well. The endangered Florida manatee (Trichechus manatus latirostris) is one of the large marine mammals facing increased pressures. Changes in water temperature in winter and summer months as well as food and habitat loss are increasing the mortality of these warm-water inhabiting creatures.
As ocean temperatures rise in coastal Florida and salinity increases from less rainfall, algal blooms are becoming more frequent and intense. Algal blooms are a sudden increase in algae populations and can be toxic to aquatic life. A particular red tide caused over 270 manatee deaths in 2013 alone. Non-toxic algae can have devastating effects as well, blocking sunlight from reaching the sea beds where seagrass and its attached algae grow. Seagrass is the primary food source for manatees and a loss of more than fifty percent has been documented in some areas. Intense storms can also have a negative effect on seagrass abundance. Increasing storm frequency and intensity is predicted in the coming years and manatee mortality is expected to rise from the loss of these aquatic plants.
Since manatees have a very low metabolic rate, they also suffer from a condition called cold-stress when water temperatures fall to around 18º C (64.4 ºF). In winter months when water temperatures in Florida are lower, manatees take refuge by thermal outputs of power plants or in natural springs where water temperatures are higher. Some of these power plants will cease to have any thermal output in coming years and loss of rainfall by as much as 15% will decrease natural spring abundance. The warmer areas still available are expected to get overcrowded as the winter water temperatures in Florida continue to drop and soon will reach capacity.
Researchers will be observing manatee populations as global climate change takes more shape in the coming years. The increase in dangers to manatees are predicted using modeling programs but since it is not certain the course global climate change will take, there are currently not any measures being put into place to prevent manatee mortality from these causes, although perhaps it should be considered. If changes occur too rapidly for adult populations to adapt, the species may face a serious decline in numbers.
-by Danielle Critchfield
Edwards, Holly H. 2013. Potential Impacts of Climate Change on Warmwater Megafauna: The Florida Manatee Example (Trichechus Manatus Latirostris). Climatic Change 121(4): 727–738.