Faucher et al. (2025): Growth response of Emiliania huxleyi to ocean alkalinity enhancement

Giulia Faucher, Mathias Haunost, Allanah Joy Paul, Anne Ulrike Christiane Tietz, Ulf Riebesell IN: Biogeosciences 22, 405-415, https://doi.org/10.5194/bg-22-405-2025

The urgent necessity of reducing greenhouse gas emissions is coupled with a pressing need for widespread implementation of CDR techniques to limit the increase in mean global temperature to levels below 2 °C compared to pre-industrial times. One proposed CDR method, OAE, mimics natural rock weathering processes by introducing suitable minerals into the ocean, thereby increasing ocean alkalinity and promoting CO₂ chemical absorption. While theoretical studies hold promise for OAE as a climate mitigation strategy, careful consideration of its ecological implications is essential. Indeed, the ecological impact of enhanced alkalinity on marine organisms remains a subject of investigation, as it may lead to changes in species composition. OAE implicates favorable conditions for calcifying organisms by enhancing the saturation state of calcium carbonate and decreasing the energetic costs for calcification. This may affect marine primary production by improving conditions for calcifying phytoplankton, among which coccolithophores play the leading role. They contribute < 10 % to the global marine primary production but are responsible for a large proportion of the marine calcite deposition. While previous research has extensively studied the effects of ocean acidification on coccolithophores, fewer studies have explored the impacts of elevated pH and alkalinity. In this context, the authors studied the sensitivity of Emiliania huxleyi, the most widespread coccolithophore species, to ocean alkalinity enhancement in a culture experiment.

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