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bioRxiv · 10.1101/2024.02.23.581783

Short periods of decreased water flow may modulate long-term ocean acidification in reef-building corals

Martins, C. P. P.·Simancas-Giraldo, S. M.·Schubert, P.·Wall, M.·Wild, C.·Wilke, T.·Ziegler, M.
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Abstract

Ocean acidification (OA) poses a major threat to reef-building corals. Although water flow variability is common in coral reefs and modulates coral physiology, the interactive effects of flow and OA on corals remain poorly understood. Therefore, we performed a three-month OA experiment investigating the effect of changes in flow on coral physiology. We exposed the reef-building corals Acropora cytherea, Pocillopora verrucosa, and Porites cylindrica to control (pH 8.0) and OA (pH 7.8) conditions at moderate flow (6 cm s-1) and monitored OA effects on growth. Throughout the experiment, we intermittently exposed all corals to low flow (2 cm s-1) for 1.5 h and measured their photosynthesis:photosynthesis (P:R) ratio under low and moderate flow. On average, corals under OA calcified 18 % less and grew 23 % less in surface area than those at ambient pH. We observed species-specific interactive effects of OA and flow on coral physiology. P:R ratios decreased after 12 weeks of OA in A. cytherea (22 %) and P. cylindrica (28 %) under moderate flow, but were unaffected by OA under low flow. P:R ratios were stable in P. verrucosa. These results suggest that short periods of decreased water flow may modulate OA effects on some coral species, indicating that flow variability is a factor to consider when assessing long-term effects of climate change.

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Martins, C. P. P., Simancas-Giraldo, S. M., Schubert, P., Wall, M., Wild, C., Wilke, T., Ziegler, M.. 2024-02-28. Short periods of decreased water flow may modulate long-term ocean acidification in reef-building corals. https://doi.org/10.1101/2024.02.23.581783

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