Article

Estuaries and Coasts

, Volume 34, Issue 1, pp 106-119

Open Access This content is freely available online to anyone, anywhere at any time.

Temperature Inverted Haloclines Provide Winter Warm-Water Refugia for Manatees in Southwest Florida

  • Bradley M. StithAffiliated withJacobs Technology, contracted to U.S. Geological Survey, Southeast Ecological Science Center Email author 
  • , James P. ReidAffiliated withU.S. Geological Survey, Southeast Ecological Science Center
  • , Catherine A. LangtimmAffiliated withU.S. Geological Survey, Southeast Ecological Science Center
  • , Eric D. SwainAffiliated withU.S. Geological Survey, Florida Water Science Center
  • , Terry J. DoyleAffiliated withU.S. Fish and Wildlife Service
  • , Daniel H. SloneAffiliated withU.S. Geological Survey, Southeast Ecological Science Center
  • , Jeremy D. DeckerAffiliated withU.S. Geological Survey, Florida Water Science Center
  • , Lars E. SoderqvistAffiliated withU.S. Geological Survey, Florida Water Science Center - Ft. Myers

Abstract

Florida manatees (Trichechus manatus latirostris) overwintering in the Ten Thousand Islands and western Everglades have no access to power plants or major artesian springs that provide warm-water refugia in other parts of Florida. Instead, hundreds of manatees aggregate at artificial canals, basins, and natural deep water sites that act as passive thermal refugia (PTR). Monitoring at two canal sites revealed temperature inverted haloclines, which provided warm salty bottom layers that generally remained above temperatures considered adverse for manatees. At the largest PTR, the warmer bottom layer disappeared unless significant salt stratification was maintained by upstream freshwater inflow over a persistent tidal wedge. A detailed three-dimensional hydrology model showed that salinity stratification inhibited vertical convection induced by atmospheric cooling. Management or creation of temperature inverted haloclines may be a feasible and desirable option for resource managers to provide passive thermal refugia for manatees and other temperature sensitive aquatic species.

Keywords

Thermal inversion Halocline Stratification Passive thermal refugia Picayune Strand restoration Everglades restoration Aerial survey Satellite telemetry Climate change Aquatic species