The acquisition of inorganic carbon by the seagrass Zostera marina

Sven Beer*, Jon Rehnberg

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


In this work, it is elucidated to what degree the seagrass Zostera marina L. can utilise HCO3/as an external inorganic-carbon source for photosynthesis, and which of two possible systems for its acquisition is in effect. It was found that HCO3/- was used as a major source of inorganic carbon at the normal seawater-pH of 8.2, and that bulk CO2 contributed only marginally (less than 20%) to photosynthesis at that pH. By comparing photosynthetic rates at pH 8.2 and 9.0, it was deduced that CO3/2- could not be utilised. It was further found that HCO3/- could be acquired via extracellular dehydration to CO2, as catalysed by external/surface-bound carbonic anhydrase, prior to inorganic-carbon uptake. Indications for active, ATPase-mediated, HCO3/- transport was also found, but an inhibitor of extracellular carbonic anhydrase affected photosynthetic rates more than did the less specific ATPase inhibitors. The rationale for HCO3/- dehydration versus its direct uptake is discussed with regard to the photosynthetic performance of seagrasses, many of which are inorganic-carbon limited in their natural habitats.

Original languageEnglish
Pages (from-to)277-283
Number of pages7
JournalAquatic Botany
Issue number3-4
StatePublished - Apr 1997


  • Carbon acquisition
  • Carbonic anhydrase
  • Photosynthesis
  • Seagrass
  • Zostera marina


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