Chemical characterization of the Punta de Fuencaliente CO.sub.2-enriched system : a new natural laboratory for ocean acidification studies

We present a new natural carbon dioxide (CO.sub.2) system located off the southern coast of the island of La Palma (Canary Islands, Spain). Like CO.sub.2 seeps, these CO.sub.2 submarine groundwater discharges (SGDs) can be used as an analogue to study the effects of ocean acidification (OA) on the marine realm. With this aim, we present the chemical characterization of the area, describing the carbon system dynamics, by measuring pH, A.sub.T and C.sub.T and calculating Ω aragonite and calcite. Our explorations of the area have found several emission points with similar chemical features. Here, the C.sub.T varies from 2120.10 to 10 784.84 µmol kg.sup.-1, A.sub.T from 2415.20 to 10 817.12 µmol kg.sup.-1, pH from 7.12 to 8.07, Ω aragonite from 0.71 to 4.15 and Ω calcite from 1.09 to 6.49 units. Also, the CO.sub.2 emission flux varies between 2.8 and 28 kg CO.sub.2 d.sup.-1, becoming a significant source of carbon. These CO.sub.2 emissions, which are of volcanic origin, acidify the brackish groundwater that is discharged to the coast and alter the local seawater chemistry. Although this kind of acidified system is not a perfect image of future oceans, this area of La Palma is an exceptional spot to perform studies aimed at understanding 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 CO.sub.2, or to predict the consequences of present fossil fuel usage on the marine ecosystem of the future oceans.