Defense Date

8-4-2025

Document Type

Thesis

Degree Type

Master of Science

Degree Name

Marine Science

First Advisor

Dr. Brian K. Walker

Second Advisor

Dr. David Gilliam

Third Advisor

Dr. Diego Lirman

Keywords

coral reef restoration, adaptable restoration protocols, Orbicella faveolata, predation exclusion device, polyhydroxyalkanoate

Abstract

Boulder-coral populations, particularly Orbicella spp., have declined recently in the Caribbean and Florida due mainly to stony coral tissue loss disease, leading to their classification as threatened in the US Endangered Species Act (ESA). Over 300 corals>2 m in diameter were previously surveyed and mapped in southeast Florida; the majority being Orbicella faveolata up to 320 years old. Many have died or suffered extensive tissue loss, leading to low densities. Restoring healthy tissue to their structures is vital for reinstating ecological function and staving off bioerosion. Therefore, O. faveolata fragments of healthy-looking disease-resistant donor colonies were propagated through microfragmentation. Various outplanting strategies across outplant locations, fragment genotypes, time of year, fragment size, and predation protection were tested. Predation, survival, and growth on outplanted fragments were assessed in three phases (February 2023, December 2023, and May 2024). Phase 1, embedding fragments of two different sizes into the coral skeleton, showed high predation on the smallest fragments. To address the Phase 1 challenges that were encountered, Phases 2 and 3 embedded larger fragments into cement domes and biodegradable PHA tubes were used to protect fragments from fish. Biodegradable PHA tubes effectively mitigated early fish predation. Predation by fish was most intense within the initial months, impacting fragment survivorship. Variation in predation and fragment growth was also observed across fragment genotypes and outplant locations, highlighting the importance of strategic site selection and prioritizing genotypes with optimal growth. Based on these findings, it is recommended that practitioners use fragments greater than 2 cm² and incorporate biodegradable PHA tubes to protect outplants during predation-intensive initial months. Additionally, outplanting success depends on timing and should ideally coincide with periods of low environmental stress. These propagated fragments are an important genetic stock of disease-resistant donors, and the outcomes of this project provide recommendations for optimizing the use of corals of opportunity, which may ultimately enable the recovery of major reef-building corals in Florida.

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