The response of Thalassiosira pseudonana to long-term exposure to increased CO <inf>2</inf> and decreased pH

Publication Type:
Journal Article
PLoS ONE, 2011, 6 (10)
Issue Date:
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The effect of ocean acidification conditions has been investigated in cultures of the diatom Thalassiosira pseudonana CCMP1335. Expected end-of-the-century pCO 2 (aq) concentrations of 760 μatm (equivalent to pH 7.8) were compared with present-day condition (380 μatm CO 2, pH 8.1). Batch culture pH changed rapidly because of CO 2 (aq) assimilation and pH targets of 7.8 and 8.1 could not be sustained. Long-term (~100 generation) pH-auxostat, continuous cultures could be maintained at target pH when cell density was kept low (<2×10 5 cells mL -1). After 3 months continuous culture, the C:N ratio was slightly decreased under high CO 2 conditions and red fluorescence per cell was slightly increased. However, no change was detected in photosynthetic efficiency (F v/F m) or functional cross section of PS II (σ PSII). Elevated pCO 2 has been predicted to be beneficial to diatoms due to reduced cost of carbon concentration mechanisms. There was reduced transcription of one putative δ-carbonic anhydrase (CA-4) after 3 months growth at increased CO 2 but 3 other δ-CAs and the small subunit of RUBISCO showed no change. There was no evidence of adaptation or clade selection of T. pseudonana after ~100 generations at elevated CO 2. On the basis of this long-term culture, pH change of this magnitude in the future ocean may have little effect on T. pseudonana in the absence of genetic adaption. © 2011 Crawfurd et al.
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