Ocean acidification drives species-specific and time-dependent pigment responses in three phytoplankton taxa

Date

2026-01-01

Author

Kocaman, Emel
Özhan, Koray
Mantıkcı, Asım Mustafa

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Phytoplankton are primary producers in marine ecosystems and play a central role in biogeochemical cycles, yet their physiological responses to altered seawater pH vary among taxa and over time. Here, we examined the effects of sustained pH manipulation on pigment composition, growth, and dark respiration in three ecologically important phytoplankton taxa - a diatom (Pseudo-nitzschia spp.), a dinoflagellate (Heterocapsa pygmaea), and a haptophyte (Emiliania huxleyi) - during a 15-day controlled laboratory experiment. Cultures were maintained at pH 8.1, 7.8, and 7.5, representing present-day and enhanced acidification conditions. Responses to pH were species-specific and strongly time-dependent. Growth and cell-specific respiration rates showed relatively small and often transient differences among pH treatments, suggesting short-term metabolic adjustment under altered pH. In contrast, pigment composition exhibited clearer and more consistent pH-related responses, primarily expressed as shifts in temporal patterns rather than uniform directional changes. In Pseudo-nitzschia spp. and H. pygmaea, several key pigments displayed pronounced pH-dependent trajectories, whereas E. huxleyi showed greater temporal variability and weaker separation among pH treatments. Overall, these results demonstrate that photophysiological traits respond sensitively to sustained pH changes even when population-level growth and respiration remain comparatively stable, highlighting pigment composition as a potentially sensitive indicator of short-term phytoplankton acclimation to ocean acidification.

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https://hdl.handle.net/11511/120844

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Graduate School of Marine Sciences, Article