Congratulations to my student Ariana Huffmyer, one of three winners of the 2018 UHM Tester Symposium for her presentation of work in the Gates Lab on the physiological effects of conditioning juveniles to thermal stress.
GETTING A HEAD START: THERMAL AND NUTRITIONAL CONDITIONING OF JUVENILE CORALS
Thermal stress from ocean warming destabilizes the nutritional symbiosis between corals and their intracellular symbionts, leaving an energy deficit for the coral host. Corals with large energy reserves or those that can compensate for this deficit through heterotrophic feeding may have a greater chance of surviving thermal stress events. Heterotrophic nutrition plays a different role in the energetic status of corals during warm and cool seasonal periods, but little is understood on the role of cool seasonal cycles on coral growth, development, and thermal resilience. Although recent research focuses on the response of adults to bleaching events, it is unclear how post-settlement environments shape juvenile coral response to thermal stress. We evaluated the effects of conditioning regimes on the growth, survivorship, physiology, and thermal stress response of juvenile Pocillopora acuta corals. Larvae collected from parental colonies in Kāne‘ohe Bay, Hawai‘i were settled and exposed to cool (25.7°C) or ambient (27.3°C) temperatures either the presence or absence of a heterotrophic food source. Juveniles were conditioned in these temperature and nutritional treatments for one month before being exposed to a thermal stress test (max. temperature ca. 32°C). There was a positive effect of cool temperature on survivorship and a positive effect of heterotrophic nutrition on growth. Cooler temperatures and heterotrophic nutrition also increased tissue thickness, symbiont densities, and thermal resilience, indicating that these conditions shape physiological responses in warming conditions. These results suggest that cool seasonal periods and heterotrophic feeding enhances resilience of juvenile corals to elevated temperatures and bleaching events.