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Seagrass Beds
 Seagrasses are flowering plants found in shallow coastal marine waters and are different than seaweed (algae). Algae obtains its nutrients directly from the water through diffusion, while seagrasses use their leaves and roots to obtain nutrients from sediment and water. There are seven species of seagrasses found off Florida's coast.
Florida has 1.5 million acres of seagrass beds. These beds are important feeding and breeding habitats for many marine species, including sea turtles. Unfortunately, seagrass beds have been on the decline since 1940 and more than one-third of the original seagrass around the state has been lost. Along Florida's Gulf Coast, seagrass beds have declined 8% since 1969. Seagrasses are both an indicator of environmental health and an important breeding ground for the lower tier of the marine food chain.
Seagrass beds are incredibly important habitat for juvenile and adult fish and crabs and shrimp. They also tend to be relatively sensitive indicators of water quality, and in places where humans are affecting water quality, researchers can look at trends over time in seagrass abundance as a way to indicate whether humans are having more or less of an impact on water quality. In addition to pollution, seagrass beds are declining due to being damaged by boat propellers and anchors.
Nearshore Hardbottom
Nearshore hardbottom habitat are the primary natural reef structures at depth of less than 15 feet and is primarily made up of tube-building polychaete worms or coquina shells. Hardbottom reefs are often centrally located between mid-shelf reefs and barrier island estuarine habitats. The reefs provides habitat to more than 530 marine organisms, including juvenile snappers, grunts, groupers, wrasses, and sea turtles. These reefs help stabilize nearby beaches. Nearshore reefs reduce wave and current energy and protect against coastal erosion.
Unfortunately, beach renourishment projects, which involve dredging sand from offshore and pumping it onto the beach, impact Florida's nearshore habitats, as well as the green turtles that find food and shelter there. In particular, the artificially wide, man-made beaches bury large sections of nearshore reef and hardbottom habitats used by sea turtles and many other forms of marine life. The projects can also increase turbidity in the water, which affects the reef algae – the primary food source for juvenile green turtles.
Coral Reefs
Numerous species of coral are found in Florida reefs. Each kind lives in a separate colony that is shaped differently from the others. The colonies take on the various hues of the algae that live within them—usually red, green, and brown.
Coral reefs are among the most biologically diverse ecosystems on earth. They are second only to tropical rain forests in the number of species they harbor and, indeed, are sometimes called “the rain forests of the sea.” Like their terrestrial
counterparts, coral communities may contain valuable materials and medicines that may one day be useful to people. In Florida, coral reefs are home to many of the state’s most important fisheries resources, including spiny lobsters and groupers. Reefs also
buffer coastal land from the damaging effects of storms and erosion and help to form the sandy beaches and quiet lagoons that are signatures of the state’s tourism industry.
Florida’s coral reefs today face an unintentional, but growing, threat from the very people who prize them most. Boaters frequently run aground or drop anchor on the coral heads, divers and snorkelers step on and bruise them, and pollution threatens to sully the clear waters that are vital to their survival.
Florida Keys National Marine Sanctuary
The Florida Keys National Marine Sanctuary protects an area of over 3600 square miles (2800 square nautical miles) of submerged lands and waters surrounding the Florida Keys. It includes parts of Florida Bay, the southwest continental shelf, the corals of the Florida Reef Tract that parallel the seaward edge of the Florida Keys, the Keys themselves, and the Straits of Florida. Sanctuary waters range from an average depth of four feet in Florida Bay to 2000 feet. Depth of the reef tract averages about 50 feet. The submerged lands of the sanctuary are part of a plateau of marine sediments that includes all of Florida and its adjacent continental shelves. The outer edge of the reef tract is subject to open tidal exchange of warm, clear waters of the Florida Straits that are low in nutrients and conducive to reef development.
The Keys are a partial barrier between the warm-temperate waters of the Gulf of Mexico and the tropical to subtropical waters of the Atlantic Ocean to their south. A corresponding distinction in marine flora and fauna between the two regimes is a result. The biota on the Atlantic side of the Florida Keys National Marine Sanctuary is predominantly Caribbean in character, while the marine biota on the northern side are characteristic of warm-temperate areas. However, water exchange between the two regions through channels between islands allows for a mixing of biota in nearshore areas.
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