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MEPS prepress abstract   -  DOI:

Green turtle herbivory and its effects on the warm, temperate seagrass meadows of St. Joseph Bay, Florida (USA)

Alexandra R. Rodriguez*, Kenneth L. Heck Jr

*Corresponding author:

ABSTRACT: The green turtle Chelonia mydas occurs sporadically in tropical and subtropical latitudes but effective conservation efforts are leading to increasing abundances at higher latitudes. One consequence of increased green turtle abundance in some locations has been the overgrazing of seagrasses, its preferred food item. Recent, large increases in juvenile green turtle abundance in the warm temperate northern Gulf of Mexico, especially in the clear waters of St Joseph Bay, FL, make this a prime location to study effects of their feeding activities on the extensive turtlegrass (Thalassia testudinum)-dominated meadows. Using caging and simulated grazing to quantify green turtle effects, we found that excluding green turtles led to increased Thalassia shoot density, and that simulating turtle grazing resulted in narrowed leaves and decreased turtlegrass productivity. Naturally grazed areas protected from further turtle grazing did not recover after 14 weeks of protection. Two years following relaxation of simulated grazing, turtlegrass continued to show residual stress symptoms, with narrower and fewer leaves per shoot than control areas. The future success of sea turtle conservation efforts is critically linked, and dependent on, the protection and sustainability of their globally decreasing feeding grounds. Thus, continued study of how increasing green turtle populations affect warm temperate turtlegrass meadows will provide important information on how best to manage both turtle and seagrass resources.