Florida manatees depend on warm water refuges in winter — natural springs and power plant discharge sites — and the loss of power plant warmth sources creates welfare risks for thermally vulnerable animals.
Manatees caught in rapidly cooling water experience cold stress syndrome — a physiological emergency causing immune dysfunction, susceptibility to infection, and progressive organ failure. Animals unable to reach warm water refuges in time die from cold exposure. The thermal vulnerability of manatees is extreme — they are warm-water specialists unable to tolerate the temperature ranges that characterize their geographic range for most of the year. As power plants close, human-maintained warm water refuges become increasingly important for individual manatee welfare.