College of Arts and Sciences
Master of Science in Biology (MS)
NACO controlled Corporate Body
University of North Florida. Department of Biology
Dr. Eric Johnson
Dr. Matthew B. Ogburn
Dr. Adam Rosenblatt
In top-down regulation of ecological communities, predation of grazers is critical for maintaining the presence and growth of essential vegetation. The periwinkle snail (Littoraria irrorata) is a ubiquitous grazer in Atlantic salt marshes that can defoliate patches of Spartina alterniflora when populations are extremely dense. On the east coast of Florida, multiple predators could contribute to periwinkle population control maintaining this critical habitat. This study aimed to determine if the blue crab (Callinectes sapidus) is the primary predator of periwinkle snails in the salt marsh lower intertidal. Tethering was utilized to assess if periwinkle mortality is related to distance, predation strategy, and shell size. Groups of periwinkles (n = 5), were tethered in place at 0 m, 1 m, 3 m, and 5 m into the marsh for 24 hours. The presence or absence of each snail was recorded, and predated snails were classified by predation strategy (crushing, cutting, or extracting) using the characteristic patterns of snail remains. Key findings were: (1) Likelihood of predation for tethered snails declined exponentially as distance into the marsh increased, suggesting that the interior serves as a spatial refuge for periwinkles. However, predation was equally likely at 1 m, 3 m, and 5 m. The data also support that large crabs are limited to the marsh edge, while small crabs can forage within. (2) The crushing predation strategy was most prevalent across all distances, indicating that blue crabs are the dominant predator. (3) For all snails mortality was highest at the marsh edge, but across the interior larger snails generally had lower mortality than smaller snails. This size refuge favors larger snails and corresponds with blue crab size selectivity. Together, the observed trends in mortality, predation strategy, and size selectivity support the assertion that blue crabs are the dominant predator in the lower intertidal.
Small, Amanda Paige, "The Relative Contribution of the Blue Crab (Callinectes sapidus) to Periwinkle Snail (Littoraria irrorata) Predation Mortality in the Lower Salt Marsh Intertidal of Northeast Florida" (2021). UNF Graduate Theses and Dissertations. 1085.
Available for download on Friday, August 11, 2023