Bottom-water deoxygenation at the Peruvian margin during the last deglaciation recorded by benthic foraminifera

Abstract

Abstract. Deciphering the dynamics of dissolved oxygen in the mid-depth ocean during the last deglaciation is essential to understand the influence of climate change on modern oxygen minimum zones (OMZs). Many paleo-proxy records from the eastern Pacific Ocean indicate an extension of oxygen-depleted conditions during the deglaciation, but the degree of deoxygenation has not been quantified to date. The Peruvian OMZ, one of the largest OMZs in the world, is a key area to monitor such changes in near-bottom-water oxygenation in relation to changing climatic conditions. Here, we analysed the potential to use the composition of foraminiferal assemblages from the Peruvian OMZ as a quantitative redox proxy. A multiple regression analysis was applied to a joint dataset of living (rose-bengal-stained, fossilizable calcareous species) benthic foraminiferal distributions from the Peruvian continental margin. Bottom-water oxygen concentrations ([O2]BW) during sampling were used as the dependant variable. The correlation was significant (R2=0.82; p<0.05), indicating that the foraminiferal assemblages are rather governed by oxygen availability than by the deposition of particulate organic matter (R2=0.53; p=0.31). We applied the regression formula to three sediment cores from the northern part of the Peruvian OMZ between 3 and 8∘ S and 997 and 1250 m water depth, thereby recording oxygenation changes at the lower boundary of the Peruvian OMZ. Each core displayed a similar trend of decreasing oxygen levels since the Last Glacial Maximum (LGM). The overall [O2]BW change from the LGM and the Holocene was constrained to 30 µmol kg−1 at the lower boundary of the OMZ.

Climate-Biogeochemistry Interactions in the Tropical Ocean: Data Collection and Legacy

“…The rates were calculated from linear steady-state gradients of nitrous oxide or oxygen in glass microcapsules (after Høgslund et al, 2008;Piña-Ochoa et al, 2010;Glock et al, 2019). Abundances of living benthic foraminifera were determined on three cruises to the Peruvian OMZ (Mallon et al, 2012;Glock et al, 2013;Erdem et al, 2020). Total abundances and individual metabolic rates were used to upscale to the total contribution of foraminifers to benthic N-fluxes and nitrate storage (Glock et al, 2013(Glock et al, , 2019.…”

Climate-Biogeochemistry Interactions in the Tropical Ocean: Data collection and legacy

“…The rates were calculated from linear steady-state gradients of nitrous oxide or oxygen in glass microcapsules (after Høgslund et al, 2008;Piña-Ochoa et al, 2010;Glock et al, 2019). Abundances of living benthic foraminifera were determined on three cruises to the Peruvian OMZ (Mallon et al, 2012;Glock et al, 2013;Erdem et al, 2020). Total abundances and individual metabolic rates were used to upscale to the total contribution of foraminifers to benthic N-fluxes and nitrate storage (Glock et al, 2013;Glock et al, 2019).…”

Ecological and Environmental Stability in Offshore Southern California Marine Basins Through the Holocene

“…Benthic foraminiferal assemblages are an effective and established metric to quantify past changes in marine oxygenation (Balestra et al., 2018; Belanger et al., 2020; Bernhard et al., 1997, 2003; Bernhard & Gupta, 1999; Cardich et al., 2015, 2019; Caulle et al., 2014; De & Gupta, 2010; Kaiho, 1994; Moffitt et al., 2014; Murgese & De Deckker, 2005; Ohkushi et al., 2013; Praetorius et al., 2015). Benthic foraminiferal assemblages are sensitive to small changes in oxygenation in the North Pacific, even in suboxic environments, not exclusively across biological thresholds of anoxic or sulfidic conditions (Sharon et al., 2021).…”

“…Paleorecords provide an important archive to investigate temporal and spatial scales of changes to marine oxygenation. In general, warm intervals during the late Quaternary were associated with decreased global ocean oxygenation and cool intervals were associated with increased oxygenation (Cannariato & Kennett, 1999;Cardich et al, 2019;Erdem et al, 2019;Jaccard et al, 2014;Praetorius et al, 2015). The Holocene is an ideal epoch to investigate marine oxygenation because it has well documented intervals of oceanographic change and provides an opportunity to investigate ecological response to stress, including changes to temperature, oxygenation, carbon cycling and ocean circulation (Addison et al, 2017;Barron et al, 2003;Fisler & Hendy, 2008;Moffitt et al, 2015;Praetorius et al, 2015).…”