Manatees inhabit rivers, bays, canals, estuaries and coastal areas moving freely between fresh, saline and brackish waters. Florida estuaries and freshwater lakes, springs and rivers provide extensive beds of seagrass and abundant freshwater aquatic vegetation that provide the manatee’s primary food sources. Just as important is warm water habitat. Manatees cannot tolerate prolonged exposure to very cold water (below 68º F), and in the winter will migrate to areas of warm water for survival. To help sustain a healthy population of manatees in Florida, FWC, along with other partners and stakeholders, work together to manage the protection of Florida’s seagrass and warm water habitat resources.
Manatees are herbivores and feed on a variety of submerged, emergent and floating plants. These plants not only provide food to Florida’s manatees, but are also an important component of marine and freshwater ecosystems.
Freshwater Aquatic Vegetation
Hundreds of plant species inhabit Florida’s freshwater environments, providing an important food source for manatees. Some common freshwater plants manatees are known to eat include Eelgrass and Coontail along with exotic species like Water hyacinth and Hydrilla.
Seagrasses are underwater flowering plants that live in Florida’s protected bays, lagoons, and other shallow coastal waters. Because seagrass requires sunlight, most seagrass is found in clear shallow waters. These grass-like plants form small patchy beds that develop into large continuous beds known as seagrass meadows. Manatees are known to consume all species of seagrass found in Florida, including Manatee grass, Turtle grass, Shoal grass, and others.
Importance of Aquatic Vegetation
- Provide food and habitat for fish and wildlife
- Increase water clarity
- Stabilize sediments and shorelines
- Affect nutrient cycles
- Support local economies
Threats to Aquatic Vegetation
- Dredging of waterways
- Removal of shoreline vegetation and construction of seawalls
- Excessive nutrient run-off from land (leading cause of phytoplankton blooms)
- Shading from docks
- Increased sediments from shoreline and off-shore construction
- Propeller scars (“prop” scars)
| Aquatic Vegetation Protection Efforts
Seagrasses and freshwater aquatic vegetation grow throughout Florida’s waterbodies and are vital to the state’s economy due to the fishing and tourism industries that rely on the fish and wildlife that are dependent on this habitat for survival. Conservation and protection of aquatic vegetation involves many citizens, stakeholders and partners from government and industry. These conservation efforts include:
Manatee Habitat and Human-related Threats to Seagrass in Florida: A Review (165kb)
How you can help:
- Practice smart boating by avoiding navigation through shallow grass beds.
- Avoid contributing to the problem of changing water chemistry through run-off, be careful when applying fertilizers and pesticides. Rain can wash excess chemicals into rivers or other water bodies which drain into the sea.
- Use grating rather than planks when building or repairing a dock. Grating allows sunlight to penetrate to grasses living below docks.
Warm Water Refuges:
Manatees seek out warm water areas whenever the water temperature drops below about 68º F. Warm water refuges in Florida can come from natural sources, such as freshwater or Sulphur springs, or artificial warm water from power plant/energy center outfalls. The water temperature in these refuges must be consistent and reliable in order for manatees to seek out and reuse these sites on an annual basis.
Importance of Warm Water to Manatees
Manatees are regarded as tropical marine mammals, migrating to warmer waters during the colder months of the year. In the summer months, manatees are widely dispersed in Florida’s waterways and can even be found on rare occasions as far north as Massachusetts. When the water temperatures dip below about 68 o F (20 o C), however, manatees seek out Florida’s warm water areas. Prolonged exposure to lower water temperatures causes manatees to lose body heat and inadequately digest their food, which can lead to a condition classified as "cold stress" and eventually can be fatal.
Historically, manatees relied solely on warm water springs and other natural areas for refuge in winter. With the advent of power plants and other industrial sources of warm water effluent, many manatees began using these discharge basins as winter refuges. It is estimated that currently about 60% of the manatee population is dependent upon industrial sources of warm water with many hundreds being found together at some sites during the cold season. Loss of warm water habitat is a serious long-term threat to manatees.
Where are Florida's manatees
Threats to Warm Water Refuge Areas
- Reduction of natural spring flow due to groundwater withdrawals for human use
- Port Facilities and Inlets
- Power Plant Shut Down
Warm Water Protection and Restoration Efforts
- Establish minimum flows at Florida springs that protect the warm-water habitat
requirements of manatees.
- Develop and implement plans to prevent significant future manatee mortality caused by potential changes in power plant operation.
- Enhance protection and restoration of seagrasses and freshwater vegetation in proximity to warm water habitats.
- Improve manatee access to natural spring systems.
Summary of Artificial Warm Water Refugia Issues - This is a synopsis of the FWC's endeavors regarding the topic of artificial warm water refuges.
The Effects of Proposed Restoration of the Ocklawaha River in the Vicinity of the Rodman Basin on Manatees and Manatee Habitat (142Kb) - This report summarizes the history of Rodman Reservoir, historical manatee use, mortality and habitat information for this reservoir and the previously free-flowing Ocklawaha River, and predicted effects on manatee habitat quality and regional manatee populations using this system after planned restoration efforts are completed.
Manatee Sanctuaries and Quiet Resting Areas
DRAFT FWC Seagrass Survey Protocol Recommendations
Florida International University Seagrass Ecosystems Research Lab
University of Florida Center for Aquatic and Invasive Plant
Southeastern Estuarine Research Society