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Indian River County Manatee Protection and Boating Safety Comprehensive Management Plan Water quality degradation caused by coastal construction, urbanization and boat traffic has an indirect effect on SAV by decreasing the amount of sunlight in the water column. A 1975 study found that "prop scars" in Florida result from boats that run in water less than one (1) meter deep at mean low water level (MLWL); many of these scars are recognizable for as long as five (5) years. Studies conducted in Tampa Bay by the Florida Marine Research Institute (FMRI) have shown that Thalussia beds will recover to natural short -shoot densities in approximately 3.6 to 6.4 years, since Thcalassia is a successional climax species. The colonizing seagrasses, Halodule and Syringodhon, may recover at a faster rate since they have rapidly -expanding root systems. Halodule may recover in 0.9 to 1.8 years in an interior bed, while scars in a less dense seagrass bed fringe may recover between 2.3 to 4.6 years. When open sediments are regularly disturbed, a scouring effect prevents recolonixation of even pioneer seagrass species. Spoil Islands In Indian River County, there are 55 spoil islands in the IRL. Most of these spoil islands are located west of the Intracoastal Waterway (TCW), and nearly half are located in the Malabar - Vero Beach Aquatic Preserve (Aquatic Preserve #7). A 1990 Florida Department of Natural Resources (FDNR, now FDEP) Spoil Island Management Plan classified 31 of the islands for conservation, with the remaining islands classified for various degrees of recreational and educational public access. Although large aggregations of manatees have not been documented around these spoil islands, aerial surveys demonstrate that manatees utilize the shallow seagrass beds located near these islands. These island seagrass fringes are most likely utilized for foraging and not as resting or shelter areas, thus preventing the documentation of large aggregations. Pelican Island National Wildlife Refuge The Pelican Island National Wildlife Refuge (PINWR) consists of approximately 5,000 acres of the IRI. and mangrove islands between C.R. 510 and the Sebastian Inlet and east of the ICW. The PINWR is managed by the USFWS for the purpose of protecting nesting colonies of brown pelicans and other wading birds. The island is off-limits to visitors, and boats are required to maintain a minimum distance of 150 feet from the island due to the extensive year- round use by wading birds and pelicans. Warm Water Refuge Areas When water temperatures drop below 68 degrees Fahrenheit, manatees become susceptible to cold -related disease and death, and will seek out warm water sources. Although the Vero Beach Municipal Power Plant near the 17th Street Causeway is considered a relatively minor warm water refuge area, it may be important for pre- and post -winter migrations. The Vero Beach Municipal Power Plant may be used as a stop -over point for manatees traveling south in early winter or north in early spring; however, this migration is not limited to early winter and spring time frames. Manatees are known to travel both north and south from the Vero Beach Plant throughout tite winter. Foraging resources and travel corridors, which are close to thermal refuges and used by manatees, are critical to a large percentage of the regional Community Development Department Page 11