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Long-term physiological responses to combined ocean acidification and warming show energetic trade-offs in an asterinid starfish


While organismal responses to climate change and ocean acidification are increasingly documented, longer-term (> a few weeks) experiments with marine organisms are still sparse. However, such experiments are crucial for assessing potential acclimatization mechanisms, as well as predicting species-specific responses to environmental change. Here, we assess the combined effects of elevated pCO2 and temperature on organismal metabolism, mortality, righting activity, and calcification of the coral reef-associated starfish Aquilonastra yairi. Specimens were incubated at two temperature levels (27 °C and 32 °C) crossed with three pCO2 regimes (455 µatm, 1052 µatm, and 2066 µatm) for 90 days. At the end of the experiment, mortality was not altered by temperature and pCO2 treatments. Elevated temperature alone increased metabolic rate, accelerated righting activity, and caused a decline in calcification rate, while high pCO2 increased metabolic rate and reduced calcification rate, but did not affect the righting activity. We document that temperature is the main stressor regulating starfish physiology. However, the combination of high temperature and high pCO2 showed nonlinear and potentially synergistic effects on organismal physiology (e.g., metabolic rate), where the elevated temperature allowed the starfish to better cope with the adverse effect of high pCO2 concentration (low pH) on calcification and reduced skeletal dissolution (antagonistic interactive effects) interpreted as a result of energetic trade-offs.

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The datasets generated during and/or analyzed throughout the present study are available from the corresponding author on reasonable request.


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We are grateful to the Ministry of Education, Culture, Research, and Technology (MoECRT), Republic of Indonesia—Asian Development Bank (ADB) AKSI Project for a doctoral scholarship granted to MK. Andreas Kunzmann (ZMT) is thanked for his advice on the starfish A. yairi as a model organism. We thank Silvia Hardenberg, José Garcia, Nico Steinel of the ZMT Marine Experimental Ecology Facility (MAREE) for providing advice, support, and technical assistance, and ZMT laboratory staff Matthias Birkicht, Fabian Hüge, and Stefanie Bröhl for assistance in the chemistry and biology laboratories. The authors thank the reviewers for their comments, which greatly improved the article.


This research project was supported by the Leibniz Centre for Tropical Marine Research (ZMT) Academy–Doctoral Research Grant, and by the MoECRT, Republic of Indonesia–ADB AKSI Project [grant number L3749-INO] to MK. SSD was funded by the Alexander von Humboldt Stiftung Foundation Postdoctoral Fellowship.

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MK and HW conceptualized and designed the research. MK, SSD, MS, and HW developed the research methodology. MK conducted the laboratory experiments, data curation, sample processing, sample analyses, data visualization, original draft preparation, and served as the primary author of the manuscript. HW supervised the research project. All authors contributed to interpretation and discussion of the results. MK wrote the manuscript with contributions from all authors. All authors gave final approval for publication and agree to be held accountable for the work performed therein.

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Correspondence to Munawar Khalil.

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All animal procedures were in accordance with the German Animal Welfare Act regulations and were approved by the local authorities.

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Khalil, M., Doo, S.S., Stuhr, M. et al. Long-term physiological responses to combined ocean acidification and warming show energetic trade-offs in an asterinid starfish. Coral Reefs 42, 845–858 (2023).

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