Natural CO2 seepage sites
Natural CO2 seepage will be studied in ECO2 as analogues for CO2 leakage. A number of key processes controlling leakage pathways and impacts on biota will be studied in situ by including natural analogue sites as additional study sites. Moreover, natural analogues will serve as test beds for the development of high-end monitoring techniques. Volcanic CO2 seeps have been studied in detail by ECO2 partners in recent years. These include the Mediterranean Panarea gas seeps located in shallow waters off Panarea Island, the Jan Mayen gas vents located at ~700 m water depth in the North Atlantic, and the CO2 droplet seeps in the Okinawa Trough at ~2000 m water depth. The first sedimentary CO2 seep was discovered recently in the German sector of the North Sea. It is located above the Juist Salt Dome at ~30 m water depth. Water column imaging reveals a large number of gas flares emanating from the seabed while chemical sensors have detected strong acidification of ambient bottom waters probably caused by the injection and dissolution of CO2 gas bubbles. The emitted CO2 seems to originate from a deep sedimentary reservoir, apparently ascending to the surface through fractures formed during salt dome emplacement. These four natural analogues cover a wide range of water depths, geological settings, and biological communities. They will be used to study the ascent of CO2 through sedimentary strata, to decipher the dynamics of gas bubble and droplet plumes, to understand the impact of CO2 on benthic organisms and marine ecosystems, and to test and improve CO2 monitoring techniques.