Assessing the effect of high concentration of CO_2 on deep-sea benthic microorganisms using a benthic chamber system

摘要

In order to evaluate the impact of storage of CO_2 in the ocean on deep-sea benthic microorganism community, in situ experiments by using a free fall type benthic chamber system was carried out in the Kumano Trough at a depth of 2,000 m and the Norwegian fjord (Storfjorden) at a depth of 400 m. The experiment exposure concentration of CO_2 averaged 20,000 and 5,000 uatm for the two exposure groups and intact as for control has prepared. At KumanoTrough, the meiobenthos declined whereas bacteria increased in abundance under the condition of 20,000 μatm compared with the control. On the other hand, at Storfjorden, the meiobenthos varied greatly and bacteria was not changed during exposure. However, nanobenthos was significantly increased in the exposure chambers compared with the control. These results suggest that bacteria and/or nanobenthos adapted to high CO_2 were increased because grazing activity of meiobenthos in the exposure chamber became lower than for the control. The respiration rate of the exposure groups was different compared with the control, its change agreed well with variation of biomass of taxa in the each chamber, suggesting the possibility of high CO_2 influencing biological activities such as feeding and respiration.