Oxygenation variability in Mejillones Bay, off northern Chile, during the last two centuries

Abstract

Abstract. The Peru Chile Current ecosystem is characterized by high biological productivity and important fisheries. Although this system is likely to be severely affected by climate change, its response to current global warming is still uncertain. In this paper, we analyze 10-166 year-old sediments in two cores collected from Mejillones Bay, an anoxic sedimentary setting favorable for the preservation of proxies. Based on a 166-year chronology, we used proxies of bottom-water oxygenation (Mo, V, S, and the (lycopane+n-C 35 )/n-C 31 ratio) and surface water productivity (biogenic opal, counts of diatom valves, biogenic Ba, organic carbon, and chlorins) to reconstruct environmental variations in Mejillones Bay. During the last two centuries, a shift took place in the coastal marine ecosystem of Bahia Mejillones at decadal scales. This shift was characterized by intense ENSO-like activity, largescale fluctuations in biological export productivity and bottom water oxygenation, and increased eolian activity (inferred from Ti/Al and Zr/Al). This short-term variability was accompanied by a gradual increase of sulfidic conditions that has intensified since the early 1960s.

Anchovy population and ocean-climatic fluctuations in the Humboldt Current System during the last 700years and their implications

“…4), which represent similar values to those yielded in previous studies in this bay Vargas et al, 2004;Caniupán et al, 2009, Díaz-Ochoa et al, 2011. Moreover, these values are within the range of those reported for other high-productivity areas in Chile (Thamdrup and Canfield, 1996), and Perú Díaz-Ochoa et al, 2009;Gutiérrez et al, 2011).…”

Early diagenesis of redox-sensitive trace metals in the Peru upwelling area – response to ENSO-related oxygen fluctuations in the water column

“…This approach is of great relevance for upwelling areas or other oxygen-deficient settings where recent studies have attempted to reconstruct past OMZ extension and/or ENSO variability (e.g. Nameroff et al, 2004;Gutiérrez et al, 2009;Díaz-Ochoa et al, 2011). McManus et al (2006) derived an empirical relationship between sedimentary U/Mo ratios and oxygen concentrations in bottom water.…”

System controls of coastal and open ocean oxygen depletion

“…Proxies for water column denitrification, including sediment redox conditions, bioturbation and benthic foraminifera, among others, have been used to reconstruct past variation of subsurface oxygenation in the region (Higginson and Altabet, 2004;Morales et al, 2006;Gutiérrez et al, 2009;Salvatteci et al, 2014Salvatteci et al, , 2016Erdem and Schönfeld, 2017;Díaz-Ochoa et al, 2011;Castillo et al, 2017). At multidecadal to millennial timescales, the intensity and extension of the OMZ is modulated by changes in the Walker circulation, which controls the thermocline depth and thereby the productivity and respiration in the ETSP, as well as the subsurface ventilation associated with the equatorial currents (Agnihotri et al, 2008;Gutiérrez et al, 2009;Xu et al, 2015;Salvatteci et al, 2016).…”