Document Type



Virginia Institute of Marine Science

Publication Date



Climate Change Ecology






Global climate change and anthropogenic nutrient inputs are responsible for increased frequency of cyanobac- terial blooms that potentially contain 55 classes of bioactive metabolites. This study investigated the effects of CO2 availability and concomittant pH levels on two cyanobacteria that produce microcystins: a marine cf. Syne- chocystis sp. and a freshwater Microcystis aeruginosa. Cyanobacterial strains were semi-continuously cultured in mesotrophic growth media at pH 7.5, 7.8, 8.2, and 8.5 via a combination of CO2 addition and control of alkalinity. The cell concentration between treatments was not significantly different and nutrient availability was not lim- ited. Concentration of most known cyanobacterial bioactive metabolites in both cyanobacterial strains increased as CO2 increased. At pH 7.8, bioactive metabolite intracellular concentration in M. aeruginosa and Synechocystis was 1.5 and 1.2 times greater than the other three treatments, respectively. Intracellular concentration of mi- croginin in M. aeruginosa at pH 7.5 was reduced by 90% compared to the other three treatments. Intracellular concentration of microcyclamide-bistratamide B was lower in M. aeruginosa and higher in Synechocystis at ele- vated CO2 concentration. M. aeruginosa products were more diverse metabolites than Synechocystis. The diversity of accumulated metabolites in M. aeruginosa increased as CO2 increased, whereas the metabolite diversity in Syne- chocystis decreased as pH decreased. Overall, intracellular concentration of bioactive metabolites was higher at greater CO2 concentrations; marine and freshwater cyanobacteria had different allocation products when exposed to differing CO2 environments.


doi: 10.1016/j.ecochg.2021.100018