Degree

Doctor of Philosophy (PhD)

Department

Oceanography and Coastal Sciences

Document Type

Dissertation

Abstract

Today’s coral reefs are met with several environmental stressors and anthropogenic disturbances leading many to question whether they will persist beyond the 21st century. Persistence across a network of coral reefs requires a balance of recruitment from extraneous sources and the retention of locally produced larvae. While dispersal modeling and population genetics have provided critical insights on the potential pathways leading to long distance recruitment, larval retention remains significantly understudied. The main obstacles in gathering insight on larval retention are: 1) the paucity of information on coral life histories and behaviors, even among the most common species, and 2) the lack of high-resolution hydrodynamics which can elucidate fine-scale processes facilitating retention. This dissertation addresses both challenges, exploring biological and physical mechanisms supporting larval retention in coral larvae throughout the Tropical Western Atlantic.

First, it surveys the Gulf of Mexico and models how eddies could support retention over a series of isolated coral reefs. This model suggests that the Flower Garden Banks spawning season may naturally coincide with higher eddy activity in the surrounding area, supporting entrainment and recirculation of larval propagules over their natal habitats. Next, it investigates swimming behaviors in the larvae of six coral species. Through the development of novel experimental chambers, it examines how larvae change speeds as they age, from planulation or gamete release up to 16 days of dispersal. Results indicate that some broadcast spawned larvae may require settlement cues to swim downward, even when fully competent. This was in stark contrast to brooded larvae, which can settle in minutes following planulation, in the absence of chemical cues. Finally, using a high-resolution model to simulate reef-scale processes, the dissertation investigates the impact of swimming behaviors on larval retention. Since the water column is highly stratified, the ability of larvae to influence their depth likely has a great influence on dispersal potential. This model suggests that swimming behaviors increase larval retention relative to propagules that remain at the surface. Coral larvae must navigate the changing seascape and undergo successful recruitment to persist into the future.

Date

7-20-2023

Committee Chair

Holstein, Daniel M.

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Available for download on Wednesday, July 10, 2030

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