Suchocki, C. R. | Search bioRxiv

bioRxiv2025

Nature vs nurture? Light availability drives phenotypic plasticity within a reef coral species

Scleractinian corals exhibit wide intra-specific phenotypic variations. However, the extent to which these variations are explained by genotypic variation or phenotypic plasticity remains unclear. To elucidate this question, we devised a replicated experiment in which nine Montipora capitata coral colonies were cut into six pieces each, three of which were placed in shaded conditions (with a 73% reduction in light intensity) whereas the other three were kept in natural conditions as a control. After one year, we detected statistically significant morphological differences between corals of the same genotypes grown in different light environments, but no significant change in symbiont community structure. Colonies kept in control conditions exhibited high surface complexity and converged towards more digitate or corymbose morphs compared to shaded corals, which exhibited planar-like surfaces and converged toward laminar and foliose forms. Our data demonstrate the high level of light-driven phenotypic plasticity of Montipora capitata and suggest a trade-off between the amount of biomass per space area and the amount of absorption of incident light.

ecology↗

bioRxiv2024

Shading does not lower thermal tolerance in the coral Montipora capitata: implications for conservation intervention

Marine heatwaves trigger severe coral bleaching events that result in dramatic losses of coral reefs worldwide. An increasingly common method used to mitigate coral bleaching is to shade portions of reefs. However, as shaded corals become less exposed to environmental stress, shading has also been hypothesized to lower their thermal tolerance, which would be detrimental for their survival. Here, we investigated how long-term shading modifies the response of Montipora capitata to both light and temperature stressors. After two years of growth, we used the Coral Bleaching Automated Stress System (CBASS) to compare responses of 73% shaded and unshaded corals during 1) temperature stress under ambient light, 2) temperature stress under low light, and 3) ambient temperature with light stress. Results show that shaded corals are less resistant than control ones to light stress and to heat stress under high light, but not to heat stress under low light, where no difference was detected. We further demonstrate that low light intensity during heat stress reduces the decline of photosynthetic efficiency when compared to heat stress at ambient light, regardless of the light history of the coral colonies. Our data support light-mediated stress, both independent of and synergistic with heat-induced stress, and suggest that light and heat stresses trigger different molecular and cellular pathways. We hereby confirm the benefits of coral shading under both short- and long-term temperature stress, and underline the importance of light acclimation in the conservation and restoration of coral reefs.

ecology↗