HCNSO Student Theses and Dissertations

Defense Date

7-23-2019

Document Type

Thesis

Degree Name

M.S. Marine Biology

First Advisor

Joana Figueiredo Ph.D.

Second Advisor

Brian Walker Ph.D.

Third Advisor

Bernhard Riegl Ph.D.

Abstract

Coral reef decline worldwide has led to the need for coral reef restoration. The use of sexual reproduction in restoration efforts is required to increase genetic diversity; however, the procedures for rearing newly-settled coral recruits ex situ still need to be optimized. Recruits initially require low light irradiance, but it is unclear when higher irradiances are required to enhance growth and survival. Here we determined the optimal light regime for Orbicella faveolata and Acropora cervicornis recruits. Newly settled recruits were reared under treatments with varied rates of increasing irradiance (after reaching 5 weeks of age), and their survival, growth, and coloration was assessed weekly until they were 16 weeks old. Orbicella faveolata and Acropora cervicornis growth and survival were significantly affected by light irradiance regimes. Coloration also varied between treatments with a general trend of darkening pigmentation over the sixteen weeks. We found that low irradiances (< 40 mmol photons m-2s-1) were optimal for new recruits up to 8-10 weeks of age, which is possibly related to the full establishment of symbiosis and/or the ability to feed and digest food. Aposymbiotic recruits were able to survive for a longer period under low irradiances but experienced high mortality when exposed to higher irradiance, regardless of their age, possibly due to low levels or the lack of mycosporine like amino acids and other antioxidants produced by the Symbiodiniaceae that protect against high irradiances and reactive oxygen species. After Weeks 8-10, high irradiance levels similar to the ones that are optimal for adults (> 120 mmol photons m-2s-1) were required by zooxanthellate coral to survive and to boost their growth. This further suggests that the acquisition of symbionts from the family Symbiodiniaceae is at least one key component in the shift toward tolerating higher irradiances.

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