June 2002
John Pennecamp Coral Reef State Park

Elkhorn Coral, Acropora palmata
Coral reefs require relatively calm, clear, and clean waters with stable temperatures (above 70F) and salinity.
Coral is a collection of small, individual coral animals called polyps. These polyps secrete a limestone shell around themselves and as they grow
they come into contact with many other such other polyps.  This conglomeration of polyp shells forms a living reef. When the polyps die new
polyps build their home on top of the limestone skeletons. This conglomeration of polyp shells, from dead and living polyps,  forms a coral reef.
Zooxanthellae are tiny algae that grow in the tissues of coral polyps. They depend on coral for food and protection and the coral depend on
zooxanthellae for oxygen and food.  This is why corals require clear water otherwise the zooxanthellae would not be able to carry out
photosynthesis in the tissues of the polyps.
Historic wet and dry seasons, which provided steady sheets of water, have been replaced with times of drought or powerful discharges. Waters
reaching the lower Everglades have passed through agricultural and urban areas and contain increased nutrients, such as nitrogen and
phosphorus, and pollutants.
Nitrogen and phorphorus are usually nutrients in limited supply in coral reef habitats.  When present in high enough concentrations algae multipy
and algal blooms cloud the water over the reef, preventing the zooxanthellae in the tissues of the coral polyps from absorbing enough sunlight for
photosynthesis.  The result is a net loss of living coral.
While sawgrass historically acted as a filter for the slow moving waters, it cannot filter the increased nutrient loads,
which now travel through the Everglades to Florida Bay and the coral reefs.  This and people touching and collecting coral has caused much
destruction of the reefs in south Florida.