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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 13, issue 22
Biogeosciences, 13, 6247–6259, 2016
https://doi.org/10.5194/bg-13-6247-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 13, 6247–6259, 2016
https://doi.org/10.5194/bg-13-6247-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 21 Nov 2016

Research article | 21 Nov 2016

Physiological responses of coastal and oceanic diatoms to diurnal fluctuations in seawater carbonate chemistry under two CO2 concentrations

Futian Li1, Yaping Wu1, David A. Hutchins2, Feixue Fu2, and Kunshan Gao1 Futian Li et al.
  • 1State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361102, China
  • 2Department of Biological Sciences, University of Southern California, Los Angeles, California, USA

Abstract. Diel and seasonal fluctuations in seawater carbonate chemistry are common in coastal waters, while in the open-ocean carbonate chemistry is much less variable. In both of these environments, ongoing ocean acidification is being superimposed on the natural dynamics of the carbonate buffer system to influence the physiology of phytoplankton. Here, we show that a coastal Thalassiosira weissflogii isolate and an oceanic diatom, Thalassiosira oceanica, respond differentially to diurnal fluctuating carbonate chemistry in current and ocean acidification (OA) scenarios. A fluctuating carbonate chemistry regime showed positive or negligible effects on physiological performance of the coastal species. In contrast, the oceanic species was significantly negatively affected. The fluctuating regime reduced photosynthetic oxygen evolution rates and enhanced dark respiration rates of T. oceanica under ambient CO2 concentration, while in the OA scenario the fluctuating regime depressed its growth rate, chlorophyll a content, and elemental production rates. These contrasting physiological performances of coastal and oceanic diatoms indicate that they differ in the ability to cope with dynamic pCO2. We propose that, in addition to the ability to cope with light, nutrient, and predation pressure, the ability to acclimate to dynamic carbonate chemistry may act as one determinant of the spatial distribution of diatom species. Habitat-relevant diurnal changes in seawater carbonate chemistry can interact with OA to differentially affect diatoms in coastal and pelagic waters.

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Ongoing ocean acidification is being superimposed on the natural carbonate buffer system to influence the physiology of phytoplankton. Here, we show that coastal and oceanic diatoms respond differentially to diurnal fluctuating carbonate chemistry in current and ocean acidification scenarios. We propose that the ability to acclimate to dynamic carbonate chemistry may act as one determinant of the spatial distribution of diatom species.
Ongoing ocean acidification is being superimposed on the natural carbonate buffer system to...
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