Carbon and Nitrogen Fixation by Anabaena fertilissima under Elevated CO₂ and Temperature

ABSTRACT

We studied the growth of Anabaena fertilissima under graded CO₂ and temperature conditions to assess its suitability as a CO₂ scavenger for carbon recycling. A. fertilissima reached maximum growth at 6% CO2, but growth declined above this CO₂ level; yet, at no CO₂ concentration growth was less than that at ambient CO₂. High temperature (>30°C) reduced growth of the cyanobacterium, but presence of elevated (6%) CO₂ lessened the intensity of that reduced growth. High temperature also reduced biomass, pigments, total protein, and nitrogen fixation, but elevated CO₂ significantly moderated this negative effect. Elevated CO₂ reduced ¹⁴CO₂ uptake by 50% at 30°C and >44% at higher temperatures compared to uptake at ambient CO₂ at 30°C. Similarly, carbonic anhydrase activity also showed inhibition at high CO₂.