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Inter-decadal changes in the intensity of the Oxygen Minimum Zone off Concepción, Chile (~ 36° S) over the last century

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  • We reconstructed oxygenation changes in the Oxygen Minimum Zone of the upwelling ecosystem off Concepción (36° S), Chile, using inorganic and organic proxies in a sediment core covering the last ca. 110 years of sedimentation in this area. Authigenic enrichments of Mo, U and Cd were observed between ca. 1935–1971 CE indicating a prolonged period of more reduced conditions in bottom waters and surface sediments. Significant positive correlations (p < 0.05; Spearman) between redox sensitive metals, algal sterols, biomarkers of anaerobic microorganisms, and archaeal glycerol dialkyl glycerol tetraether indicated a coupling among bottom water oxygen depletion, and increased primary and export production, suggesting that the period with low O₂ of ca. 35 years, follows low frequency inter-decadal variation of the Pacific Decadal Oscillation, which may have resulted in O₂ depletion over the entire continental shelf off Concepción. Taken together with the concurrent increase in sedimentary molecular indicators of anaerobic microbes allow us to suggest that the prokaryote community has been influenced by changes in oxygenation of the water column.
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  • Srain, B., Pantoja, S., Sepúlveda, J., Lange, C. B., Muñoz, P., Summons, R. E., McKay, J., and Salamanca, M. (2015) Inter-decadal changes in the intensity of the Oxygen Minimum Zone off Concepción, Chile (~ 36° S) over the last century, Biogeosciences Discussions, 12, 6003-6035, doi:10.5194/bgd-12-6003-2015
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  • 12
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  • This research was funded by the Center for Oceanographic Research in the eastern South Pacific (COPAS, grant #FONDAP 15010007) and the COPAS Sur-Austral Program PFB-31 the Gordon and Betty Moore Foundation (MI_LOCO Project, Oregon_Concepcion, grant #1661), the MIT International Science and Technology Initiatives (MIT-MISTI-Chile), and the NASA Astrobiology Institute. Additionally, FONDECyT grant #1061214 funded radiocarbon analysis. B. Srain acknowledges a student fellowship from the Ministry of Education's MECESUP grant UCO0602; the Department of Atmospheric, Earth and Planetary Sciences of MIT; the Fulbright Chilean Commission; and the MI_LOCO Project for supporting a research visit to MIT. S. Pantoja acknowledges support from the Hanse Wissenschaftskolleg, Delmenhorst (Germany). We acknowledge the support provided by the COPAS Oceanographic Time Series St. 18 off Concepción.
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