title: Short-term elevated CO2exposure stimulated photochemical performance of a coastal marine diatom.
abstract: Ocean acidification changes seawater chemistry, with increased CO2and decreased pH regarded as the most important factors that impact marine organisms. This study employed an unconventional methodology to distinguish the independent effects of pH versus CO2. Changes in CO2dominated the photochemical responses of the coastal diatom Phaeodactylum tricornutum to short-term ocean acidification. Increased CO2lowered non-photochemical quenching of excitation and stimulated the electron transport rates of photosynthesis, with the largest effects on both parameters when CO2and pH were altered simultaneously. Changes in pH alone did not show significant effects upon non-photochemical quenching (NPQ) nor upon electron transport rates, but can synergistically amplify CO2effects under low light. Maximal induction of NPQ after illumination showed only a limited response to increasing CO2under stable pH, across a range of increasing light levels, but maximal induced NPQ declined rapidly with increasing CO2under variable pH, when measured under exposure to sub-saturating light, but not under saturating light. These findings show that aqueous CO2and pH affect different physiological processes independently or interactively, which should be taken into account in future research for better understanding of responses to ocean acidification at the mechanistic level.
authors.affiliation: State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China.
authors.forename: Yaping
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Biology Department, Mount Allison University, Sackville, New Brunswick, Canada.
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Campbell
authors.affiliation: State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China. Electronic address: ksgao@xmu.edu.cn.
authors.forename: Kunshan
authors.initials: K
authors.lastname: Gao
mesh_terms: D002245:Carbon Dioxide / Q000633:toxicity*; D017377:Diatoms / Q000187:drug effects / Q000502:physiology*; D004579:Electron Transport; D006863:Hydrogen-Ion Concentration; D010788:Photosynthesis / Q000187:drug effects*; D012623:Seawater / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D002245:Carbon Dioxide
keywords: CO(2); Combined effects; Diatom; Ocean acidification; Photosynthesis; pH