ABSTRACT
Marine heatwaves are increasing in frequency and intensity, with potentially catastrophic consequences for marine ecosystems such as coral reefs. An extended heatwave and recovery time-series that incorporates multiple stressors and is environmentally realistic can provide enhanced predictive capacity for performance under climate change conditions. We exposed common reef-building corals in Hawai‘i, Montipora capitata and Pocillopora acuta, to a 2-month period of high temperature and high PCO2 conditions or ambient conditions in a factorial design, followed by 2 months of ambient conditions. High temperature, rather than high PCO2, drove multivariate physiology shifts through time in both species, including decreases in respiration rates and endosymbiont densities. Pocillopora acuta exhibited more significantly negatively altered physiology, and substantially higher bleaching and mortality than M. capitata. The sensitivity of P. acuta appears to be driven by higher baseline rates of photosynthesis paired with lower host antioxidant capacity, creating an increased sensitivity to oxidative stress. Thermal tolerance of M. capitata may be partly due to harboring a mixture of Cladocopium and Durusdinium spp., whereas P. acuta was dominated by other distinct Cladocopium spp. Only M. capitata survived the experiment, but physiological state in heatwave-exposed M. capitata remained significantly diverged at the end of recovery relative to individuals that experienced ambient conditions. In future climate scenarios, particularly marine heatwaves, our results indicate a species-specific loss of corals that is driven by baseline host and symbiont physiological differences as well as Symbiodiniaceae community compositions, with the surviving species experiencing physiological legacies that are likely to influence future stress responses.
Footnotes
Author contributions
Conceptualization: E.L.S., H.M.P.; Methodology: E.L.S., K.H.W., A.F., S.G., A.M., H.M.P.; Software: E.L.S., H.M.P.; Validation: E.L.S., H.M.P.; Formal analysis: E.L.S., H.M.P.; Investigation: E.L.S., H.M.P.; Resources: E.L.S., H.M.P.; Data curation: E.L.S., K.H.W., A.F., S.G., A.M., H.M.P.; Writing - original draft: E.L.S., H.M.P.; Writing - review & editing: E.L.S., K.H.W., A.F., S.G., A.M., H.M.P.; Visualization: E.L.S., H.M.P.; Supervision: E.L.S., H.M.P.; Project administration: E.L.S., H.M.P.; Funding acquisition: H.M.P.
Funding
This work was supported by the USDA National Institute of Food and Agriculture, Hatch Formula project accession number 1017848, and the National Science Foundation Award number 1756623.
Data availability
All data and code used to produce results and complete analyses are available at https://github.com/hputnam/Acclim_Dynamics and Open Science Framework (OSF) doi:10.17605/OSF.IO/Q9HMC. Laboratory protocols and processing can be found on Emma Strand's Open Laboratory Notebook at https://emmastrand.github.io/EmmaStrand_Notebook/. ITS2 Sequencing FASTQ files have been uploaded to NCBI under project no. PRJNA761780.