Master of Science
Joana Figueiredo, PhD
Margaret Miller, PhD
D. Abigail Renegar, PhD
delayed settlement, latent effects, settlement cues, post-settlement
The recovery of coral populations depends largely on larval recruitment. Coral larvae settle in response to environmental cues that indicate habitat quality. Newly competent larvae typically avoid settling on substrates with high macroalgal cover and sedimentation, and thus might never recruit to degraded reefs, hindering their recovery. What is unknown is if settlement preferences change as larvae age. In the absence of suitable settlement cues, lecithotrophic larvae delay settlement and might do this until either dying (Death Before Dishonor Hypothesis) or becoming less discriminatory and settling regardless of their specific habitat requirements (Desperate Larva Hypothesis). To test these hypotheses in corals, changes in discrimination between settlement cues, such as crustose coralline algae (known settlement-inducing cue for corals) and Dictyota sp. (inhibitory cue), were assessed. Larvae from three reef-building and one weedy coral species were randomly drawn from a surviving pool and split into four age groups, and exposed to suitable and unsuitable settlement cues 0, 7, 14, or 21 days after becoming competent, respectively. Newly settled corals were then monitored for three months to assess any potential latent effects of delayed metamorphosis on post-settlement survival and growth. The results showed that as larvae got older, broadcast spawning species decreased selectivity (‘Desperate’), whereas brooding species’ larvae never did (‘Death Before Dishonor’). Moreover, the delayed settlement of the brooding coral A. agaricites showed latent effects on post-settlement survival and growth. The broadcast spawner Orbicella faveolata exhibited latent effects on post-settlement growth. This study demonstrates that delayed settlement (increasing larval age) affects post-settlement survival and growth differently between species. However, “old” coral larvae from broadcast spawners likely can disperse widely to replenish degraded reefs. Since natural recruitment can happen regardless of settlement cue suitability, larval seeding could be included in restoration efforts in the Caribbean to rehabilitate recently disturbed coral reefs, reducing costs and labor.
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Nepsis García Lara. 2023. Desperate Larva Or Death Before Dishonor: Can Old Coral Larvae Replenish Degraded Reefs?. Master's thesis. Nova Southeastern University. Retrieved from NSUWorks, . (154)