Defense Date

4-18-2023

Document Type

Thesis

Degree Type

Master of Science

Degree Name

Marine Science

First Advisor

Joana Figueiredo

Second Advisor

Craig Dahlgren

Third Advisor

David Gilliam

Keywords

corallivory, Bahamas, fish surveys, coral survey, predation, lobster

Abstract

Corallivores are understood to be ecologically important. However, their effects on reef ecosystems are difficult to distinguish from the multiple anthropogenic stressors currently affecting reefs. The corallivorous muricid snail, Coralliophila galea, has been documented to have a strong negative impact on Caribbean coral reefs, including curtailing reef recovery following other stressors. Although the basic biology of C. galea is relatively well understood, the limited information on its predators prevents a complete understanding of predator-snail-coral relationships, which limits proper protection and conservation of coral reef ecosystems. To determine the impact predators of C. galea have on coral reef ecosystems, I assessed the relationships between the snails, their potential predators, and coral cover. Specifically, I determined if and to what extent spiny lobsters, Panulirus argus, naturally prey on C. galea and evaluated how concentrations of potential predators relate to snail densities, and how predators of C. galea indirectly affect coral cover via their impacts on snail densities. To do so, Atlantic and Gulf Rapid Reef Assessments (AGRRA) were conducted on a series of twenty Bahamian reefs to assess coral and other benthic cover, C. galea numbers, and numbers of potential predators of this corallivorous snail. Reef coral cover was inversely related to depth and directly related to C. galea site densities. Densities of C. galea was positively associated to the density of Orbicella annularis and O. faveolata and negatively associated to the density of Porites astreoides. Porites astreoides and Diploria labyrinthiformis coral cover also showed significance when analyzed individually to C. galea populations despite these two corals not being a common food source. Numbers of P. argus were too low to test its effect on snail densities. Their foraging behavior and level of interest of feeding on C. galea was examined in a controlled aquarium setting and revealed that while they will consume C. galea without size preference, it is still unclear to what extent in a wild setting this occurs. Fish densities did not reveal any additional significant associations except when analyzing Pomacentridae (damselfish). There was a positive relationship observed between damselfish and C. galea densities possibly indicating that either their predators are absent and/or that higher damselfish damage from “farming” on coral reefs attracts snails. Ultimately this study aided in understanding coral reef ecosystem dynamics and introduced new possible associations. Specifically, regarding important coral to snail relationships that may be aiding in settlement cues for C. galea, providing new data to potential C. galea predator options, and new fish populations that may provide clues to hidden coral reef dynamics.

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