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

Scholz, Florian; Hensen, Christian; Noffke, Anna; Rohde, Anne; Liebetrau, Volker; Wallmann, Klaus

doi:10.1016/j.gca.2011.08.007

Cited by 230 publications

(192 citation statements)

References 98 publications

(176 reference statements)

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“…5D). Concurrently with these increasing O 2 levels, Fe : Al ratios were above the average detrital background concentrations of 0.47 (Andean andesite; Scholz et al 2011). In contrast, at all shallower stations Fe : Al ratios were at and below the average (Fig.…”

Section: Resultsmentioning

confidence: 86%

“…On the shallow shelf, Fe oxyhydroxides are mainly supplied by the discharge of detrital sediments and reoxidation of dissolved Fe 2+ when the shelf is oxygenated. Below 600-m water depth, Fe oxyhydroxides accumulate in the sediments, mainly due to the precipitation of dissolved Fe 2+ at the lower oxycline (Scholz et al 2011). However, at these stations both Fe and P are recycled within the sediment, resulting in low to zero fluxes.…”

Section: Discussionmentioning

confidence: 99%

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Benthic iron and phosphorus fluxes across the Peruvian oxygen minimum zone

Noffke

Hensen

Sommer

et al. 2012

Limnology & Oceanography

147

144

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Benthic fluxes of dissolved ferrous iron (Fe 2+ ) and phosphate (TPO 4 ) were quantified by in situ benthic chamber incubations and pore-water profiles along a depth transect (11uS, 80-1000 m) across the Peruvian oxygen minimum zone (OMZ). Bottom-water O 2 levels were , 2 mmol L 21 down to 500-m water depth, and increased to , 40 mmol L 21 at 1000 m. Fe 2+ fluxes were highest on the shallow shelf (maximum 316 mmol m 22 yr 21 ), moderate (15.4 mmol m 22 yr 21 ) between 250 m and 600 m, and negligible at deeper stations. In the persistent OMZ core, continuous reduction of Fe oxyhydroxides results in depletion of sedimentary Fe : Al ratios. TPO 4 fluxes were high (maximum 292 mmol m 22 yr 21 ) throughout the shelf and the OMZ core in association with high organic carbon degradation rates. Ratios between organic carbon degradation and TPO 4 flux indicate excess release of P over C when compared to Redfield stoichiometry. Most likely, this is caused by preferential P release from organic matter, dissolution of fish debris, and/or P release from microbial mat communities, while Fe oxyhydroxides can only be inferred as a major P source on the shallow shelf. The benthic fluxes presented here are among the highest reported from similar, oxygen-depleted environments and highlight the importance of sediments underlying anoxic water bodies as nutrient sources to the ocean. The shelf is particularly important as the periodic passage of coastal trapped waves and associated bottom-water oxygenation events can be expected to induce a transient biogeochemical environment with highly variable release of Fe 2+ and TPO 4 .

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Section: Resultsmentioning

confidence: 86%

Section: Discussionmentioning

confidence: 99%

Benthic iron and phosphorus fluxes across the Peruvian oxygen minimum zone

Noffke

Hensen

Sommer

et al. 2012

Limnology & Oceanography

147

144

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“…This form is highly surface-reactive and removed to the sediment together with vanadyl ions formed from vanadate ions transported across the chemocline into the anoxic waters. Thus, in oxygen minimum zones (OMZs) where anoxic waters overlay sediments, and in euxinic basins, V is enriched together with Mo and U (17,(21)(22)(23). In summary, coenrichments of V, Mo, and U occur under anoxic water column conditions, whereas V release from sediments only occurs under bottom water oxygenation (see Supporting Information for further discussion).…”

Section: Evidence For Bottom Water Oxygenationmentioning

confidence: 98%

Sufficient oxygen for animal respiration 1,400 million years ago

Zhang

Wang

Bjerrum

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

287

237

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The Mesoproterozoic Eon [1,600-1,000 million years ago (Ma)] is emerging as a key interval in Earth history, with a unique geochemical history that might have influenced the course of biological evolution on Earth. Indeed, although this time interval is rather poorly understood, recent chromium isotope results suggest that atmospheric oxygen levels were <0.1% of present levels, sufficiently low to have inhibited the evolution of animal life. In contrast, using a different approach, we explore the distribution and enrichments of redox-sensitive trace metals in the 1,400 Ma sediments of Unit 3 of the Xiamaling Formation, North China Block. Patterns of trace metal enrichments reveal oxygenated bottom waters during deposition of the sediments, and biomarker results demonstrate the presence of green sulfur bacteria in the water column. Thus, we document an ancient oxygen minimum zone. We develop a simple, yet comprehensive, model of marine carbon−oxygen cycle dynamics to show that our geochemical results are consistent with atmospheric oxygen levels >4% of present-day levels. Therefore, in contrast to previous suggestions, we show that there was sufficient oxygen to fuel animal respiration long before the evolution of animals themselves.atmosphere | Mesoproterozoic | oxygen minimum zone | trace metals | biomarkers

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“…For typical particulate S content on the shelf of 1.5 wt.% and sediment mass accumulation rate of 1 g m −2 d −1 (Suits and Arthur, 2000;Scholz et al, 2011;Dale et al, 2016), S burial amounts to ca. 0.4 mmol m −2 d −1 , equivalent to around 15% of sulfate reduction (see Results).…”

Section: Fractionmentioning

confidence: 99%

Strong and Dynamic Benthic-Pelagic Coupling and Feedbacks in a Coastal Upwelling System (Peruvian Shelf)

2017

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Monthly time-series data (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)) of bottom water oxygen, nitrate and nitrite concentrations from the outer shelf (150 m water depth) in the oxygen minimum zone offshore Peru were coupled to a layered biogeochemical sediment model to investigate benthic-pelagic coupling over multi-annual time scales. The model includes the mineralization of four reactive pools of particulate organic carbon (POC) with lifetimes of 0.13, 1.3, 20, and 1700 year that were constrained using empirical data. Total POC rain rates to the seafloor were derived from satellite based estimates of primary production. Solute fluxes and concentrations in sediment porewater showed highly dynamic behavior over the course of a typical year. Conversion of fixed N to N 2 by denitrification varied from 1.1 mmol m −2 d −1 of N in winter to 1.8 mmol m −2 d −1 of N in summer with a long term mean N loss for the shelf of 1.5 mmol m −2 d −1 of N. Fixed N loss across the whole time-series agreed very well with a previously-published vertically-integrated sediment model for coupling the benthic and pelagic N cycle in regional and global models. Dissimilatory nitrate reduction to ammonium (DNRA) emerges as a major process in the benthic N cycle, producing on average 1.9 mmol m −2 d −1 of ammonium: more than twice the rate of ammonification of organic nitrogen. The model predicts sulfide emissions from the sediment of up to 1 mmol m −2 d −1 when POC rain rate exceeds 20 mmol m −2 d −1 , in agreement with past observations of benthic sulfide fluxes and sulfide plume distributions in the water column. This study demonstrates that sediments on the Peruvian shelf are not static repositories that are independent of changes taking place in the water column. Our results strongly suggest the shelf sediments must exert an important feedback on biogeochemical processes in the overlying waters, and should be considered in regional model studies.

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

Cited by 230 publications

References 98 publications

Benthic iron and phosphorus fluxes across the Peruvian oxygen minimum zone

Benthic iron and phosphorus fluxes across the Peruvian oxygen minimum zone

Sufficient oxygen for animal respiration 1,400 million years ago

Strong and Dynamic Benthic-Pelagic Coupling and Feedbacks in a Coastal Upwelling System (Peruvian Shelf)

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