STINER, J. S.*; WALTERS, L. J.; University of Central Florida: Intertidal oyster reefs impacted by recreational boating: effects on reef structure and biodiversity

Widely regarded as a keystone species and ecosystem engineer, the eastern oyster Crassostrea virginica plays a vital role in estuarine environments. Complex three-dimensional oyster reefs act as havens for biodiversity. Recently, concern for this resource has arisen in Mosquito Lagoon, Florida, the southernmost limit along the Atlantic coast for undisturbed, intertidal reefs of C. virginica. Since the 1990s, intense recreational boating activity has caused atypical dead margins (mounds of disarticulated shells) to emerge on the seaward edges of oyster reefs located along major boating channels. Once dead margins are formed, little is known about their influence on biotic composition and interactions on oyster reefs. This study focused on the impact of dead margins on: (1) oyster reef structure, (2) species diversity, and (3) predation on oyster spat. Structural differences (e.g. reef slope, shell orientation, percent live oysters) were compared between oyster reefs in pristine condition and those with dead margins. To determine if dead margins influence the diversity of mobile species inhabiting oyster reefs, lift nets were deployed on pristine and impacted reefs. These nets were checked weekly and species diversity, abundance, and biomass were recorded. Lastly, field experiments were conducted to determine the impact of dead margins on the vulnerability of oyster spat to predation. Structural variables (e.g. shell orientation, single versus clumped shells, reef slope) were manipulated and effects on oyster mortality were observed. Together, this data helps document ecological implications of dead margins on C. virginica reefs and reinforces the urgent need for enhanced regulations and restoration.