Developmental acclimation of Porites astreoides larvae enhances

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Mary Beth Decker
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In recent years, global coral cover has declined due to increased frequency and intensity of thermal disturbance events. While the impacts of thermal stress on adult corals are well studied, the latent effects on coral larvae remain poorly understood, including the potential for developmental acclimatization. Thermal performance curves (TPCs) were used to assess the effects of brooding period heat exposure on the metabolic performance of Porites astreoides (Yellow Mustard Hill coral) larvae. Adult colonies of P. astreoides were collected from a Bermuda patch reef and maintained under thermal stress (31°C) and ambient (28°C) scenarios. Released larvae were exposed to temperatures between 17.5°C to 36.5°C and size-normalized dark respiration was quantified. I expected to observe elevated thermal performance of larvae brooded under thermal stress, indicated by an increased thermal optimum. Larval size differed significantly by brooding temperature and day of release, with heat-treated colonies releasing smaller larvae. However, larvae brooded under heat stress showed an increased thermal tolerance (Topt ≥ 36.5°C) compared to larvae brooded under ambient conditions (Topt = 34.7°C), suggesting developmental acclimation effects. These results indicate that developmental heat stress (1) significantly reduces larval size, but (2) increases larval thermal tolerance.