Between the river and deep blue Gulf: The past and future of oysters in Florida's Big Bend

Oyster reefs offer diverse ecological and social services for people and natural environments; unfortunately, reefs are also highly sensitive to impairment from natural and human-induced disturbances. Florida's Big Bend coastline (Gulf of Mexico coast from Crystal River to Apalachee Bay) supports large expanses of oyster reef habitat that have existed for thousands of years in a region that is one of the most pristine coastal zones in the continental US. Using historical and current aerial imagery between 1982 and 2011 postdoctoral associate Jennifer Seavey, along with WEC faculty Peter Frederick and Bill Pine found a 66% net loss of oyster reef area. Losses were concentrated on offshore (88%), followed by nearshore (61%), and inshore reefs (50%). This very rapid loss is not typical of the local geological geological succession pattern. Multiple lines of evidence suggests that the primary mechanism for reef loss is related to strongly decreased freshwater inputs, leading to high salinity. High salinity leads both to high predation rates and high incidence and severity of diseases, leaving reefs with mostly dead oysters. Without living oysters, the reef substrate becomes unconsolidated and the nucleation site is lost. Our field observations indicate that this collapse of reefs is irreversible, even when salinity conditions improve. The decreased freshwater inputs are a product of land use and freshwater policy in north-central Florida, leading to decreased discharge of the Suwannee River. Our next step is to attempt a series of restoration experiments that will better elucidate the process of reef collapse, and test the premise that permanent stable substrate will allow oysters to repeatedly recolonize reefs. This website gives more information about the project http://floridarivers.ifas.ufl.edu/oyster.htm.