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Inorganic carbon acquisition in potentially toxic and non‐toxic diatoms: the effect of pH‐induced changes in seawater carbonate chemistry
Author(s) -
Trimborn Scarlett,
Lundholm Nina,
Thoms Silke,
Richter KlausUwe,
Krock Bernd,
Hansen Per Juel,
Rost Björn
Publication year - 2008
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.2007.01038.x
Subject(s) - total inorganic carbon , carbonic anhydrase , chemistry , photosynthesis , carbon fixation , domoic acid , seawater , ocean acidification , environmental chemistry , intracellular ph , carbonate , dissolved organic carbon , extracellular , botany , carbon dioxide , biochemistry , biology , ecology , enzyme , organic chemistry , toxin
The effects of pH‐induced changes in seawater carbonate chemistry on inorganic carbon (C i ) acquisition and domoic acid (DA) production were studied in two potentially toxic diatom species, Pseudo‐nitzschia multiseries and Nitzschia navis‐varingica , and the non‐toxic Stellarima stellaris . In vivo activities of carbonic anhydrase (CA), photosynthetic O 2 evolution and CO 2 and HCO 3 − uptake rates were measured by membrane inlet MS in cells acclimated to low (7.9) and high pH (8.4 or 8.9). Species‐specific differences in the mode of carbon acquisition were found. While extracellular carbonic anhydrase (eCA) activities increased with pH in P. multiseries and S. stellaris , N. navis‐varingica exhibited low eCA activities independent of pH. Half‐saturation concentrations (K 1/2 ) for photosynthetic O 2 evolution, which were highest in S. stellaris and lowest in P. multiseries , generally decreased with increasing pH. In terms of carbon source, all species took up both CO 2 and HCO 3 − . K 1/2 values for inorganic carbon uptake decreased with increasing pH in two species, while in N. navis‐varingica apparent affinities did not change. While the contribution of HCO 3 − to net fixation was more than 85% in S. stellaris , it was about 55% in P. multiseries and only approximately 30% in N. navis‐varingica . The intracellular content of DA increased in P. multiseries and N. navis‐varingica with increasing pH. Based on our data, we propose a novel role for eCA acting as C i ‐recycling mechanism. With regard to pH‐dependence of growth, the ‘HCO 3 − user’ S. stellaris was as sensitive as the ‘CO 2 user’ N. navis‐varingica . The suggested relationship between DA and carbon acquisition/C i limitation could not be confirmed.