Atmospheric CO2 availability induces varying responses in net photosynthesis, toxin production and N2 fixation rates in heterocystous filamentous Cyanobacteria (Nostoc and Nodularia)

Abstract Heterocystous Cyanobacteria of the genus Nodularia form major blooms in brackish waters, while terrestrial Nostoc species occur worldwide, often associated biological soil crusts. Both genera, by virtue their ability to fix N 2 and conduct oxygenic photosynthesis, contribute significantly global primary productivity. Select produce hepatotoxin nodularin whether its production will change under climate conditions needs be assessed. In light this, effects elevated atmospheric CO availability on growth, carbon fixation as well were investigated toxin non-toxin producing both genera. Results highlighted following: Biomass volume specific nitrogen (BNF) rates respectively almost six 17 fold higher aquatic compared tested, conditions. There was a direct correlation between decreased dry weight cellular content diazotrophically grown species, regardless availability. Elevated levels correlated reduction biomass BNF non-toxic species. Nodularin producers exhibited stronger stimulation net photosynthesis (NP) growth (more positive Cohen’s d) less dark respiration per non-nodularin levels. This study is first provide information NP for replete diazotrophic