The first ECO₂ research expedition has just concluded on Tuesday 14^th June 2011 in Kiel (Germany). The research crew on board the R/V Alkor investigated the natural CO₂ seep site Salt Dome Juist in the German North Sea and the industrial CO₂ storage site Sleipner in the Norwegian North Sea.

At the Salt Dome Juist site, the scientists detected acoustic signals for gas seepage during their first day of operation. However, subsequent investigations with video-guided sensors including sampling of bottom water showed no signs of active gas escape. This suggests that gas seepage are ephemeral, and vary significantly in time and space, meaning that long-term observations will be needed to fully resolve the dynamics of the system.

After leaving the natural seep site Salt Dome Juist, the scientists moved to study the seabed above the CO₂ storage site at Sleipner. CO₂ has been stored on an industrial scale at Sleipner for the past 15 years, and we wanted to see if there were any signs of gas seepage. The researchers again deployed video-guided sensors to detect for methane, carbon dioxide, and pH and they also pumped bottom water directly into a mass spectrometer on board the ship for analysis. These observations were performed above abandoned wells close to the CO₂ injection point as well as above the storage site itself. At the wells, escape of shallow methane gas, produced naturally by the degradation of organic matter, was observed. However, no seepage of CO₂ was observed at the Sleipner site, either at the wells or above the storage site. Additionally, sediment samples were taken at Sleipner for geochemical analysis and physiological experiments back onshore. Finally, a benthic lander was placed on the seabed above the central injection point for 36 hours to investigate the natural oxygen consumption and carbon dioxide production by the shallow sub-seabed ecosystem.