Carbon and Nitrogen Fixation byAnabaena fertilissimaunder Elevated CO2and 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.