Effects of CO2 on benthic biota: An in situ benthic chamber experiment in Storfjorden (Norway)

► Free fall type high CO2 exposure testing device for deep-sea benthos was developed. ► In situ experiments were carried out with this devise at Storfjorden, Norway. ► Three types of controlled pCO2 which were 500, 5000 and 20,000 μatm was examined. ► Biological activity (CH4 production, etc.) was enhanced in 5000 μatm of CO2. ► Influence of pCO2 to deep-sea benthos was not linear relationship with pCO2 conc.