High summer temperatures amplify functional differences between coral- and algae-dominated reef communities

Florian Roth, Nils Rädecker, Susana Carvalho, Carlos M. Duarte, Vincent Saderne, Andrea Anton Gamazo, Luis Silva, Maria de Lluch Calleja Cortes, Xose Anxelu G. Moran, Christian R. Voolstra, Benjamin Kürten, Burton Jones, Christian Wild

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


Shifts from coral to algal dominance are expected to increase in tropical coral reefs as a result of anthropogenic disturbances. The consequences for key ecosystem functions such as primary productivity, calcification, and nutrient recycling are poorly understood, particularly under changing environmental conditions. We used a novel in situ incubation approach to compare functions of coral- and algae-dominated communities in the central Red Sea bi-monthly over an entire year. In situ gross and net community primary productivity, calcification, dissolved organic carbon fluxes, dissolved inorganic nitrogen fluxes, and their respective activation energies were quantified to describe the effects of seasonal changes. Overall, coral-dominated communities exhibited 30% lower net productivity and 10 times higher calcification than algae-dominated communities. Estimated activation energies indicated a higher thermal sensitivity of coral-dominated communities. In these communities, net productivity and calcification were negatively correlated with temperature (>40% and >65% reduction, respectively, with +5°C increase from winter to summer), while carbon losses via respiration and dissolved organic carbon release were more than doubled at higher temperatures. In contrast, algae-dominated communities doubled net productivity in summer, while calcification and dissolved organic carbon fluxes were unaffected. These results suggest pronounced changes in community functioning associated with phase shifts. Algae-dominated communities may outcompete coral-dominated communities due to their higher productivity and carbon retention to support fast biomass accumulation while compromising the formation of important reef framework structures. Higher temperatures likely amplify these functional differences, indicating a high vulnerability of ecosystem functions of coral-dominated communities to temperatures even below coral bleaching thresholds. Our results suggest that ocean warming may not only cause but also amplify coral-algal phase shifts in coral reefs.
Original languageEnglish (US)
StatePublished - Oct 17 2020

Bibliographical note

KAUST Repository Item: Exported on 2020-10-19
Acknowledgements: We are grateful to the personnel from the King Abdullah University of Science and Technology (KAUST) Coastal and Marine Resources Core (CMOR) Laboratory for logistical support. The authors would also like to acknowledge Rodrigo Villalobos and João Cúrdia who helped during fieldwork. Figure 5 was produced by Xavier Pita, scientific illustrator at KAUST. We would liketo thank the two anonymous reviewers and the editor for their helpful suggestions and comments. The research was supported by KAUST baseline funding to BHJ and by grant Wi 2677/9-1 from the German Research Foundation (DFG) to CW. Author contributions:FR, CW and SC conceptualized and designed research. FR, LS, MLC, and VS performed research. FR, NR, VS, AA, LS, BK, and MLC analyzed data. CMD, XAGM, CRV, and BHJ contributed to research materials, logistics and to interpreting data. FR wrote original draft of the manuscript with support by CW. All authors read and approved the final manuscript


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