Interdecadal changes in 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 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 and 1971 CE, implying a prolonged period with predominantly more reduced conditions in bottom waters and surface sediments. Significant positive correlations between redox-sensitive metals, algal sterols, biomarkers of micro-aerophilic and anaerobic microorganisms, and archaeal glycerol dialkyl glycerol tetraethers point to a tight coupling among bottom water O₂ depletion and increased primary and export production. The time interval with low O₂ of ca. 35 years seems to follow low-frequency interdecadal variation of the Pacific Decadal Oscillation, and it may have resulted in O₂ depletion over the entire continental shelf off Concepción. Taking this together with the concurrent increase in sedimentary molecular indicators of micro-aerophilic and anaerobic microbes, we can suggest that changes in oxygenation of the water column are reflected by changes in microbial community. This study can inform our understanding of ecological consequences to projected trends in ocean deoxygenation.
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  • Srain, B., Pantoja, S., Sepúlveda, J., Lange, C. B., Muñoz, P., Summons, R. E., McKay, J., & Salamanca, M. (2015). Interdecadal changes in intensity of the oxygen minimum zone off Concepción, Chile (~ 36° S), over the last century, Biogeosciences, 12(20), 6045-6058, doi:10.5194/bg-12-6045-2015
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  • 12
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  • 20
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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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