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

2015 ◽  
Vol 12 (8) ◽  
pp. 6003-6035
Author(s):  
B. Srain ◽  
S. Pantoja ◽  
J. Sepúlveda ◽  
C. B. Lange ◽  
P. Muñoz ◽  
...  
Keyword(s):  
Low Frequency ◽  
Oxygen Depletion ◽  
Oxygen Minimum Zone ◽  
Anaerobic Microorganisms ◽  
The Pacific ◽  
Bottom Waters ◽  
Minimum Zone ◽  
Positive Correlations ◽  
Molecular Indicators ◽  
Oxygen Minimum

Abstract. 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.

scholarly journals Interdecadal changes in intensity of the oxygen minimum zone off Concepción, Chile (~ 36° S), over the last century

2015 ◽  
Vol 12 (20) ◽  
pp. 6045-6058 ◽  
Author(s):  
B. Srain ◽  
S. Pantoja ◽  
J. Sepúlveda ◽  
C. B. Lange ◽  
P. Muñoz ◽  
...  
Keyword(s):  
Low Frequency ◽  
Time Interval ◽  
Tight Coupling ◽  
Anaerobic Microorganisms ◽  
The Pacific ◽  
Bottom Waters ◽  
Minimum Zone ◽  
Positive Correlations ◽  
Molecular Indicators ◽  
Oxygen Minimum

Abstract. 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.

scholarly journals The control of hydrogen sulfide on benthic iron and cadmium fluxes in the oxygen minimum zone off Peru

2019 ◽  
Author(s):  
Anna Plass ◽  
Christian Schlosser ◽  
Stefan Sommer ◽  
Andrew W. Dale ◽  
Eric P. Achterberg ◽  
...  
Keyword(s):  
Hydrogen Sulfide ◽  
Trace Metals ◽  
Pore Water ◽  
Oxygen Minimum Zone ◽  
Benthic Fluxes ◽  
Benthic Chamber ◽  
Bottom Waters ◽  
Minimum Zone ◽  
Oxygen Minimum

Abstract. Sediments in oxygen-depleted marine environments can be an important sink or source of bio-essential trace metals in the ocean. However, the key mechanisms controlling the release from or burial of trace metals in sediments are not exactly understood. Here, we investigate the benthic biogeochemical cycling of Fe and Cd in the oxygen minimum zone off Peru. We combine bottom water profiles, pore water profiles, as well as benthic fluxes determined from pore water profiles and in-situ from benthic chamber incubations along a depth transect at 12° S. In agreement with previous studies, both concentration-depth profiles and in-situ benthic fluxes indicate a Fe release from sediments into bottom waters. Diffusive Fe fluxes and Fe fluxes from benthic chamber incubations are roughly consistent (0.3–17.1 mmol m−2 y−1), indicating that diffusion is the main transport mechanism of dissolved Fe across the sediment-water interface. The occurrence of mats of sulfur oxidizing bacteria on the seafloor represents an important control on the spatial distribution of Fe fluxes by regulating hydrogen sulfide (H2S) concentrations and, potentially, Fe sulfide precipitation within the surface sediment. Removal of dissolved Fe after its release to anoxic bottom waters is rapid in the first 4 m away from the seafloor (half-life

Future Expansion of the Pacific Oxygen Minimum Zone

2021 ◽  
Author(s):  
Julius J.M. Busecke ◽  
Laure Resplandy ◽  
Jasmin Gail John
Keyword(s):  
Oxygen Minimum Zone ◽  
The Pacific ◽  
Minimum Zone ◽  
Oxygen Minimum

scholarly journals A suboxic chlorophyll-a maximum persists within the Pacific oxygen minimum zone off Mexico

2019 ◽  
Vol 169-170 ◽  
pp. 104686 ◽  
Author(s):  
Amaru Márquez-Artavia ◽  
Laura Sánchez-Velasco ◽  
Eric D. Barton ◽  
Aurelién Paulmier ◽  
Eduardo Santamarı́a-Del-Ángel ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Oxygen Minimum Zone ◽  
The Pacific ◽  
Minimum Zone ◽  
Oxygen Minimum

scholarly journals Sediment release of dissolved organic matter to the oxygen minimum zone off Peru

2020 ◽  
Author(s):  
Alexandra N. Loginova ◽  
Andrew W. Dale ◽  
Frédéric A. C. LeMoigne ◽  
Sören Thomsen ◽  
Stefan Sommer ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Pore Water ◽  
Oxygen Minimum Zone ◽  
Water Interface ◽  
Sediment Release ◽  
Bottom Waters ◽  
Minimum Zone ◽  
Oxygen Minimum

Abstract. The eastern tropical South Pacific (ETSP) represents one of the most productive areas in the ocean that is characterized by a pronounced oxygen minimum zone (OMZ). Particulate organic matter (POM) that sinks out of the euphotic zone is supplied to the anoxic sediments and utilized by microbial communities. The degradation of POM is associated with dissolved organic matter (DOM) production and reworking. The release of recalcitrant DOM to the overlying waters may represent an important organic matter escape mechanism from remineralization within sediments but received little attention in OMZ regions so far. Here, we combine measurements of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) with DOM optical properties in the form of chromophoric (CDOM) and fluorescent (FDOM) DOM from pore waters and near-bottom waters of the ETSP off Peru. We evaluate diffusion–driven fluxes and net in situ fluxes of DOC and DON in order to investigate processes affecting DOM cycling at the sediment–water interface along a transect 12° S. To our knowledge, these are the first data for sediment release of DON and pore water CDOM and FDOM for the ETSP off Peru. Pore-water DOC and DON accumulated with increasing sediment depth, suggesting an imbalance between DOM production and remineralization within sediments. High DON accumulation resulted in very low pore water DOC / DON ratios (> 1) which could be caused by either an imbalance in DOC and DON remineralization, or to the presence of an additional nitrogen source. Diffusion driven fluxes of DOC and DON exhibited high spatial variability. They varied from 0.2–0.1 mmol m−2 d−1 to 2.52–1.3 mmol m−2 d−1 and from −0.042–0.02 mmol m−2 d−1 to 3.32–1.7 mmol m−2 d−1, respectively. Generally low net in situ DOC and DON fluxes as well as steepening of spectral slope (S) of CDOM and accumulation of humic-like FDOM at the near-bottom waters over time indicated active microbial DOM utilization at the sediment–water interface, potentially stimulated by nitrate (NO3−) and nitrite (NO2−). The microbial DOC utilization rates, estimated in our study, may be sufficient to support denitrification rates of 0.2–1.4 mmol m−2 d−1, suggesting that sediment release of DOM contributes substantially to nitrogen loss processes in the ETSP off Peru.

scholarly journals Underwater Glider Observations in the Oxygen Minimum Zone off Central Chile

2016 ◽  
Vol 97 (10) ◽  
pp. 1783-1789 ◽  
Author(s):  
Oscar Pizarro ◽  
Nadin Ramírez ◽  
Manuel I. Castillo ◽  
Ursula Cifuentes ◽  
Winston Rojas ◽  
...  
Keyword(s):  
Low Frequency ◽  
Oxygen Minimum Zone ◽  
Northern Chile ◽  
Underwater Glider ◽  
Central Chile ◽  
Southern Patagonia ◽  
Minimum Zone ◽  
Frequency Changes ◽  
Oxygen Minimum ◽  
Future Plans

Abstract Gliders have become an efficient and reliable oceanographic platform for measuring physical and biogeochemical properties of the seawater, and the global glider fleet is rapidly expanding. In Chile, glider observations have been carried out in very different oceanographic environments, from the mild upwelling region of subtropical northern Chile to the channels of southern Patagonia. Herein, we briefly present observations and results obtained in the oxygen minimum zone off Concepcion (∼36°30′S). Many new features have been observed in this region thanks to the relatively high resolution of the glider measurements. Future plans for the glider program include an oceanic time series off central Chile that will contribute to the regional observing system of the ocean and allow evaluations of low-frequency changes like those associated with El Niño and La Niña events.

scholarly journals Simulated effects of southern hemispheric wind changes on the Pacific oxygen minimum zone

2016 ◽  
Vol 43 (2) ◽  
pp. 728-734 ◽  
Author(s):  
Julia Getzlaff ◽  
Heiner Dietze ◽  
Andreas Oschlies
Keyword(s):  
Oxygen Minimum Zone ◽  
The Pacific ◽  
Minimum Zone ◽  
Oxygen Minimum

The Equatorial Undercurrent and the Oxygen Minimum Zone in the Pacific

2019 ◽  
Vol 46 (12) ◽  
pp. 6716-6725 ◽  
Author(s):  
Julius J. M. Busecke ◽  
Laure Resplandy ◽  
John P. Dunne
Keyword(s):  
Oxygen Minimum Zone ◽  
Equatorial Undercurrent ◽  
The Pacific ◽  
Minimum Zone ◽  
Oxygen Minimum

Foraminifera on the Demerara Rise offshore Surinam: crustal subsidence or shallowing of an oxygen minimum zone?

2014 ◽  
Vol 152 (5) ◽  
pp. 788-801 ◽  
Author(s):  
BRENT WILSON ◽  
LEE-ANN C. HAYEK
Keyword(s):  
Late Quaternary ◽  
Low Frequency ◽  
Oxygen Minimum Zone ◽  
Stratigraphic Correlation ◽  
Ocean Drilling Program ◽  
Frequency Signal ◽  
Foraminiferal Assemblage ◽  
Sequence Stratigraphic ◽  
Minimum Zone ◽  
Oxygen Minimum

AbstractThe lower bathyal Ocean Drilling Program Hole 1261A was sampled near an upper Quaternary oxygen minimum zone (OMZ). Glauconite, the percentage of the foraminiferal assemblage as benthic specimens and assemblage composition were used to investigate the behaviour of the OMZ. Benthic foraminifera and glauconite were comparable with the upper margin of the modern OMZ off California. The percentage abundances of U. peregrina and C. laevigata were on the Demerara Rise negatively correlated, the proportional abundance of U. peregrina increasing upwards through the section. This reflects variations in proximity to the upper margin of the OMZ. This might reflect either crustal subsidence or long-term shallowing of the OMZ during the earlier late Quaternary. Neither hypothesis can be accepted unequivocally. The purported subsidence can be ascribed to crustal loading by the Amazon and Orinoco deep-sea fans, but this would require that the palaeodepth to the top of the OMZ remains constant across several glacial–interglacial cycles. In contrast, it is difficult to envisage any mechanism that could have caused progressive shallowing of the OMZ across several glacial–interglacial cycles. The epifaunal Planulina wuellerstorfi is related to more oxic waters and enhanced current action. This suggests that intervals with more abundant P. wuellerstorfi were somewhat less dysoxic than those with few. These intervals approximate to those with more abundant C. laevigata. Superimposed on this low-frequency signal is a higher-frequency signal, indicated by a between-sample assemblage turnover index (ATIs) that might prove useful for long-range sequence stratigraphic correlation at bathyal depths.

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