Between 1984 and 1997 seven ships over 200 feet in length grounded in the Florida Keys, destroying over 19 acres of coral reef. Following groundings, sediment is suspended for days, threatening the health of coral and other organisms that survived the initial insult. It prohibits tank vessels and vessels greater than 50 meters in length from operating in a designated area of coral reef habitat. Nutrient pollution and sediments from coastal development and farming can block sunlight, smother corals, and impede larval settlement. Algal blooms subsequently block sunlight, reducing coral growth.
Algal competitors interfere with coral reproduction by competing for substrate.
This pollution may also weaken corals and create an environment where coral disease pathogens thrive, ultimately increasing corals' susceptibility to disease. Recent reports suggest that the occurrence of coral disease has increased throughout the Florida Keys. Water diversion in South Florida is also a problem because of the linkage of Florida Bay to the sanctuary. Water diversion has lead to reduced freshwater flows in the Bay that in turn lead to in an increase in plankton blooms, sponge and seagrass die-offs, and fish kills. Overfishing, including harvest of lobster and conch, can cause shifts in fish size, abundance, and species composition within the reef community.