Interdecadal changes in intensity of the oxygen minimum zone off Concepción, Chile (~ 36° S), over the last century

[摘要] We reconstructed oxygenation changes in the upwelling ecosystem offConcepción (36° S), Chile, using inorganic and organicproxies in a sediment core covering the last ca. 110 years of sedimentationin this area. Authigenic enrichments of Mo, U and Cd were observed betweenca. 1935 and 1971 CE, implying a prolonged period with predominantly morereduced conditions in bottom waters and surface sediments. Significantpositive correlations between redox-sensitive metals, algal sterols,biomarkers of micro-aerophilic and anaerobic microorganisms, and archaealglycerol dialkyl glycerol tetraethers point to a tight coupling among bottomwater O₂ depletion and increased primary and export production. Thetime interval with low O₂ of ca. 35 years seems to follow low-frequencyinterdecadal variation of the Pacific Decadal Oscillation, and it may haveresulted in O₂ depletion over the entire continental shelf offConcepción. Taking this together with the concurrent increase in sedimentarymolecular indicators of micro-aerophilic and anaerobic microbes, we cansuggest that changes in oxygenation of the water column are reflected bychanges in microbial community. This study can inform our understanding ofecological consequences to projected trends in ocean deoxygenation.

[学科分类] 地球化学与岩石