Photosynthetic inorganic carbon utilization and growth of Porphyra linearis (Rhodophyta)

Alvaro Israel, Shlomit Katz, Zvy Dubinsky, John E. Merrill, Michael Friedlander

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85 Scopus citations


Photosynthetic (oxygen evolution) and growth (biomass increase) responses to ambient pH and inorganic carbon (Ci) supply were determined for Porphyra linearis grown in 0.5 L glass cylinders in the laboratory, or in 40 L fibre-glass outdoor tanks with running seawater. While net photosynthetic rates were uniform at pH 6.0-8.0, dropping only at pH 8.7, growth rates were significantly affected by pH levels other than that of seawater (c. pH 8.3). In glass cylinders, weekly growth rates averaged 76% at external pH 8.0, 13% at pH 8.7 and 26% at pH 7.0. Photosynthetic O2 evolution on a daily basis (i.e. total O2 evolved during day time less total O2 consumed during night time) was similar to the growth responses at all experimental pH levels, apparently due to high dark respiration rates measured at acidic pH. Weekly growth rates averaged 53% in algae grown in fibreglass tanks aerated with regular air (360 mg L-1 CO2) and 28% in algae grown in tanks aerated with CO2-enriched air (750 mg L-1 CO2). The pH of the seawater medium in which P. linearis was grown increased slightly during the day and only rarely reached 9.0. The pH at the boundary layer of algae submerged in seawater increased in response to light reaching, about pH 8.9 within minutes, or remained unchanged for algae submerged in a CO2-free artificial seawater medium. Photosynthesis of P. linearis saturated at Ci concentrations of seawater (K0.5 560 μM at pH 8.2) and showed low photosynthetic affinity for CO2(K0.5 61 μM) at pH 6.0. It is therefore concluded that P. linearis uses primarily CO2 with HCO3- being an alternative source of Ci for photosynthesis. Its fast growth could be related to the enzyme carbonic anhydrase whose activity was detected intra- and extracellularly.

Original languageEnglish
Pages (from-to)447-453
Number of pages7
JournalJournal of Applied Phycology
Issue number5
StatePublished - 1999


  • Algal growth
  • Inorganic carbon (Ci)
  • Photosynthesis
  • Porphyra


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