Decadal changes in oyster reefs in the Big Bend of Florida's Gulf Coast

Abstract

Oyster reefs are among the world's most endangered marine habitats with an estimated 85% loss from historical levels worldwide. 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 disasters. Understanding the resilience of oyster reef communities to disturbance is key to developing effective conservation and restoration plans. 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. We assessed trends in oyster habitat along the Big Bend region between 1982 and 2011 by examining changes in areal extent and distance of oyster reefs from shore. During our study period, we found a 66% net loss of oyster reef area (124.05 ha) with losses concentrated on offshore (88%), followed by nearshore (61%), and inshore reefs (50%). We also found that the spatial distribution of oyster reefs was moving inland. This rapid loss is likely a departure from historic geological succession. Multiple lines of evidence suggest that the primary mechanism for these observed losses in oyster reefs is reduced survival and recruitment, likely a result of decreased freshwater inputs which increases existing reef vulnerability to wave action and sea level rise. Once oyster reef substrate becomes unconsolidated and the nucleation site is lost, the regeneration of the oyster reef may not be reversible through natural processes. To test these predictions, we recommend restoration-based experiments to elicit the mechanisms of decline in order to foster long-term sustainability of estuarine habitat critical to oysters.