Effects of marine heatwaves on coral resilience
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Marine heatwaves are the defining challenge to coral reefs in the Anthropocene because they disrupt the mutualism between corals and their endosymbiotic algae, causing coral bleaching. However, the impacts of marine heatwaves are heterogeneous across the seascape and within coral communities. I investigate the causes and consequences of variable effects of marine heatwaves on coral reefs. I have shown that both the largest corals and the smallest coral recruits are the most vulnerable to mortality during bleaching events. This suggests that bleaching events may undermine the recovery potential of coral reefs by disproportionately affecting the corals most important for recovery (Speare et al. 2022, Global Change Biology). I have also shown how marine heatwaves reduce the fecundity of corals that survive bleaching events (Leinbach et al. 2021).
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Following coral-killing disturbances such as marine heatwaves, the number and success of new corals can determine how reefs recover. Marine heatwaves may reduce the recovery potential of reefs by killing large corals that produce a disproportionate number of gametes, and through sublethal effects that reduce the fecundity of corals that survive bleaching events. In my current work I am investigating how a global coral bleaching event shaped stock-recruitment relationships in corals using cross-region datasets in the Pacific.
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Local conditions interact with marine heatwaves
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Emerging evidence from many ecosystems has shown that local environmental conditions can either intensify or ameliorate the effects of heatwaves on foundation organisms. Understanding how local conditions interact with climate change is a major goal in ecology, and I answer this question through my work on coral reefs by investigating how nutrient pollution interacts with heat stress during marine heatwaves. My collaborative work has shown that nutrient pollution can lower the temperature at which corals bleach and die during marine heatwaves (Donovan et al. 2020, PNAS; Speare et al. In Prep). This work shows how nutrient pollution intensifies the effects of marine heatwaves and suggests that reducing anthropogenic nutrient inputs to coral reefs may reduce the negative effects of climate change at local scales.
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