AB 23:109-118 (2015)  -  DOI: https://doi.org/10.3354/ab00619

ABSTRACT: Variability in pH is a common occurrence in many aquatic environments, due to physical, chemical and biological processes. In coastal waters, lagoons, estuaries and inland waters, pH can change very rapidly (within seconds or hours) in addition to daily and seasonal changes. At the same time, progressive ocean acidification caused by anthropogenic CO₂ emissions is superimposed on these spatial and temporal pH changes. Photosynthetic organisms are therefore unavoidably subject to significant pH variations at the cell surface. Whether this will affect their response to long-term ocean acidification is still unknown, nor is it known whether the short-term sensitivity to pH change is affected by the pCO₂ to which the cells are acclimated. We posed the latter open question as our experimental hypothesis: Does acclimation to seawater acidification affect the response of phytoplankton to acute pH variations? The diatom Skeletonema costatum, commonly found in coastal and estuarine waters where short-term acute changes in pH frequently occur, was selected to test the hypothesis. Diatoms were grown at both 390 (pH 8.2, low CO₂; LC) and 1000 (pH 7.9, high CO₂; HC) µatm CO₂ for at least 20 generations, and photosynthetic responses to short-term and acute changes in pH (between 8.2 and 7.6) were investigated. The effective quantum yield of LC-grown cells decreased by ca. 70% only when exposed to pH 7.6; this was not observed when exposed to pH 7.9 or 8.2. HC-grown cells did not show significant responses in any pH treatment. Non-photochemical quenching showed opposite trends. In general, our results indicate that while LC-grown cells are rather sensitive to acidification, HC-grown cells are relatively unresponsive in terms of photochemical performance.

KEY WORDS: Diatoms · Ocean acidification · pH · CO₂ · Photosynthesis

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Cite this article as: Zheng Y, Giordano M, Gao K (2015) Photochemical responses of the diatom Skeletonema costatum grown under elevated CO2 concentrations to short-term changes in pH. Aquat Biol 23:109-118. https://doi.org/10.3354/ab00619 Export citation Share:    Facebook - - linkedIn