The effects of reduced and elevated CO2 and O2 on the seaweed Lomentaria articulata

Authors:
  • KÜKübler
    Kübler
  • AJAndrew M. Johnston
    Andrew M. Johnston
  • JRJohn A. Raven
    John A. Raven
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Abstract
We grew a non‐bicarbonate using red seaweed, Lomentaria articulata (Huds.) Lyngb., in media aerated with four O2 concentrations between 10 and 200% of current ambient [O2] and four CO2 concentrations between 67 and 500% of current ambient [CO2], in a factorial design, to determine the effects of gas composition on growth and physiology. The relative growth rate of L. articulata increased with increasing [CO2] up to 200% of current ambient [CO2] but was unaffected by [O2]. The relative growth enhancement, on a carbon basis, was 52% with a doubling of [CO2] but fell to 23% under 5× ambient [CO2]. Plants collected in winter responded more extremely to [CO2] than did plants collected in the summer, although the overall pattern was the same. Discrimination between stable carbon isotopes (Δ13C) increased with increasing [CO2] as would be expected for diffusive CO2 acquisition. Tissue C and N were inversely related to [CO2]. Growth in terms of biomass appeared to be limited by conversion of photosynthate to new biomass rather than simply by diffusion of CO2, suggesting that non‐bicarbonate‐using macroalgae, such as L. articulata, may not be directly analogous to C3 higher plants in terms of their responses to changing gas composition.

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