Award: OCE-1935305

Award Title: RAPID: Collaborative Research: Studies of recovery from bleaching in Acropora hyacinthus: epigenetic shifts, impacts on reproductive biology and carry-over effects
Funding Source: NSF Division of Ocean Sciences (NSF OCE)
Program Manager: Michael E. Sieracki

Outcomes Report

Marine heatwaves are occurring globally and can have large impacts on species that already live at the higher edge of their thermal limits. In 2019, a marine heatwave in Moorea French Polynesia caused coral bleaching, where the close symbiotic relationship between coral and algae breaks down, ultimately starving the coral and leading to mortality. Coral bleaching and the mass mortality of reef-building corals impacts coastal ecosystems and the humans that inhabit them in significant ways, such as reductions in biodiversity of species used as a primary food source, protection from storm damage, and tourism, to name a few. However, it remains unknown how coral reefs can rebound from significant disturbances, and how sensitive these ecosystems are to multiple disturbances back-to-back. Our work suggests that while there was a mass mortality event in Moorea, French Polynesia in 2019 that led to significant death of reef-building corals, there were some corals that persisted, either through recovery of symbionts following the marine heatwave, or resistance to the heatwave altogether. We found that resistant colonies hosted a different symbiont type and fed more on particulate organic matter from offshore water, which could have contributed to their high resistance to bleaching. Alternatively, we also found colonies that recovered completely from bleaching, and these corals hosted a different symbiont, and coral bleaching depleted their energy reserves severely to the point where they could not make as many eggs and sperm for the next generation. We also found that while this species experienced a population bottleneck after the marine heatwave, this mortality may have opened physical space that allowed immigration of corals from neighboring islands, which increased genetic diversity in the population above what it was initially. Finally, we have found that there are legacy effects of this marine heatwave evident in the epigenome of corals. Taken together, our work suggests that there are resilience mechanisms in play within this ecosystem, so long as suitable habitat remains for coral recruitment, and there is sufficient time for adults that survived the marine heatwave to recover their reproductive capacity. Our project thus provides a better understanding of the dynamics of reef resilience following a marine heatwave. Last Modified: 04/23/2024 Submitted by: GretchenEHofmann

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Principal Investigator: Gretchen E. Hofmann (University of California-Santa Barbara)