Impacts of CO2 on Microbial Communities in a Mesocosm experiment

Abstract

Ocean sequestration of CO2 is one of the feasible options to mitigate atmospheric CO2 increase. On the basis of detailed investigations to date, it has been widely recognized that the CO2 sequestration in the ocean is a promising option from the points of view of its capacity, economy and effectiveness. The impacts of CO2 ocean sequestration on microbial communities and their metabolism are of great concern because they play an important role in the biogeochemical cycles. A mesocosm experiment was conducted to study the responses of marine microbial communities to different concentrations of CO2. Seawater was delivered to four tanks on land from the offshore, using a tube pump. Four CO2 conditions of experimental ecosystems were formed by CO2 enriched air under dark conditions. Chemical and biological parameters were analyzed to evaluate the impacts of CO2 on the microbial communities. The biomass of each tank was not affected considerably by the different CO2 conditions, but the potential activities of ectoenzyme were decreased under high concentration of CO2. The effects of CO2 on bacterial communities were also confirmed using molecular biological methods. To clarify the impact of CO2 on marine ecosystem, experiment should be planned to take interactions of variety of marine species into account. Bacteria play important role in ecosystem of mid-depth ocean where CO2 is assumed to be injected. Bacteria are not only the major decomposers of organic material in the ocean but also the most important potential genetic resource. Further experiments are needed to generalize the impacts of CO2 on the marine ecosystem.