Chemical characterization of Punta de Fuencaliente CO 2 seeps system (La Palma Island, NE Atlantic Ocean): a new natural laboratory for ocean acidification studies

Abstract. We present a new natural carbon dioxide (CO2) system located off the southern coast of La Palma Island (Canary Islands, Spain). Like others CO2 seeps, these seeps can be used as an analogue to study the effects of ocean acidification (OA) on the marine realm. With this aim, we present an accurate chemical characterization of the seeps system carbon emissions, describing the carbon system dynamics, by measuring pH, AT and CT, as well as, Ω aragonite and calcite. Our explorations on the area have found several emission points with similar chemical features. Here, the CO2 emission flux varies between 2.8 kg CO2 d−1 to 28 kg CO2 d−1, becoming a significant source of carbon. CO2 seeps are of volcanic origin and the alteration of local ocean chemistry is due to acid brackish water discharges. Although this kind of acidified system is not a perfect image of future oceans, this area of La Palma island is an exceptional spot to perform studies aimed to understand the effect of different levels of OA on the functioning of marine ecosystems. These studies can then be used to comprehend how life has persisted through past Eras, with higher atmospheric CO2, or to predict the consequences of present fossil fuel usage on the marine ecosystem of the future oceans.