Florida Reef Tract
This system of coral reefs is 160 miles (260 km) long and curves to the east and south of the Florida Keys. Some geologists classify it as a barrier reef, others as a barrier-like collection of bank reefs. It is the largest area of coral reefs in the US and has a high biodiversity, being home to about 60 species of stony coral, 1,300 species of mollusk, and 500 species of fish. The reefs’ health has declined over the past 30 years, mainly due to human impact. Live coral cover has decreased, coral diseases have become extensive, inhabitants that were once common (such as the queen conch) have virtually disappeared, and the area of reef encroached on by mats of algae has expanded. Causes of this degradation include overfishing, fertilizer runoff from south Florida, sedimentation onto the reefs as a result of dredging, and sewage pollution from boats. Other contributing factors include hurricane damage, declines in algae-grazing sea urchins, and direct damage from dive-boat anchors and ship groundings. Steps are being taken to reverse the decline, with some signs of success.