Florida manatees (Trichechus manatus latirostris) seek out warmer waters during winter months when ambient water temperatures drop below 20 degrees Celsius. Over time, manatees have discovered artificial warm water sites from power plant discharges in addition to natural sites such as springs and passive thermal refugia (PTRs). The Florida Power and Light (FPL) Port Everglades power plant in Broward County is one such artificial warm water refuge used by manatees. This plant was shutdown on July 16, 2013, and is expected to remain off line for at least three years during demolition and construction of a new facility. The purpose of this study was to determine changes in habitat usage and other responses to the disruption of a warm water refugia (the closure of a power plant) on Florida manatees within the greater Port Everglades region. From November 15, 2013 to March 31, 2014, manatees were counted at the site via shore line and aerial surveys. Environmental data were collected to determine variables correlated to manatee presence and absense. Two manatees were radio-tagged using remote sensing devices in an effort to identify alternative warm water refugia and feeding areas. Data were collected from state and local organizations and photo-identified manatees were used to analyze for trends in cold stress syndrome (CSS) lesions and watercraft scarring. Results confirmed that manatee presence was positively correlated with heater outlet temperature. Differences did not exist between the results of survey methods between the FPL Port Everglades (PE) and Fort Lauderdale (FL) power plant sites, however, differrences in the aerial survey counts showed an increased presence at the FL site during the colder month of January 2014. Data from tagging identified one manatee that preferred the FL site while another preferred PE, presumably due to more convenient access to feeding grounds in Biscayne Bay. Data from mortality events indicated a low number of CSS and watercraft deaths in Broward County as compared to other parts of the state of Florida. Further monitoring of the study area for the remainder of the shutdown period is recommended, as are improvements in survey design, expansion to include additional environmental data from FL, continued mortality statistic analysis and locating possible PTRs.

The Florida manatee (Trichechus manatus latirostris), a subspecies of the West Indian manatee, is one of the most endangered marine mammals in United States waters. The Florida manatee is the only manatee that ranges into subtropical and temperate regions. During the winter months manatees adopt a “refuging strategy” where they aggregate at warm-water sources immediately following decreases in the ambient water temperature to below 20° C (68° F) in order to avoid cold stress syndrome (CSS). During the winter manatees aggregate in warm water refuges, including natural warm water springs and the effluent discharges of power plants. The purpose of this study was to determine the number of manatees that aggregate and utilize the waters of the Florida Power and Light (FPL) Plant in Port Everglades (PPE), Florida, its effluent canal, and the surrounding Intracoastal Waterway during the winter months. This study documents the importance of Port Everglades as a wintering refuge for the Florida manatee. This study analyzed the inverse relationship between the number of manatees present at a warm water effluent and water temperature. In this study data were collected over five manatee winter seasons (between 15 November and 31 March) from 1999-2004, from both boat-based and land-based surveys monitoring the presence of manatees in the effluent canal from the FPL electricity generating facility in Port Everglades, FL and the Intracoastal Waterway. Findings indicated that there was an inverse relationship between the number of manatees present and water temperature, where more manatees were present in cooler months, and fewer in warmer months. This study also analyzed the parameters of Catch per Unit Effort (CPUE) as well as heating degree-days and their effect on and relationship to the number of manatees present. The higher the heating degree-days number, the more severe, or cold, winter this indicates. The year with the highest heating degree-days, 24.98, was the 2002-2003 season, which was also the season with the highest number of manatees observed, 393, and the highest CPUE, 10.62 manatees/day.