Systematics of past changes in ocean ventilation: a comparison of Cretaceous Ocean Anoxic Event 2 and Pleistocene to Holocene Oxygen Minimum Zones

Abstract. Present day oceans are generally well ventilated except mid-depth oxygen minimum zones (OMZs) under high surface water productivity regimes, regions of sluggish circulation, and restricted marginal basins. In the Mesozoic, however, entire oceanic basins transiently became dysoxic or even anoxic. In particular the Cretaceous Ocean Anoxic Events (OAEs) were characterised by laminated organic-carbon rich shales and low-oxygen indicating trace fossil assemblages preserved in the sedimentary record. Yet both, qualitative and quantitative assessments of intensity and extent of Cretaceous near-bottom water oxygenation have been hampered by deep or long-term diagenesis and the evolution of marine biota serving as oxygen indicators in today's ocean. Sedimentary features similar to those found in Cretaceous strata were observed in deposits underlying Recent OMZs, where bottom-water oxygen levels, the flux of organic matter, and benthic life are well known. Their implications for constraining past bottom-water oxygenation are addressed in this review, with emphasis on comparing OMZ sediments from the Peruvian upwelling with deposits of the late Cenomanian OAE 2 from the Atlantic NW African shelf. Holocene laminated sediments were encountered at bottom-water oxygen levels of <7 μmol kg−1 under the Peruvian upwelling and <5 μmol kg−1 in California Borderland basins and the Pakistan Margin. Changes of sediment input on seasonal to decadal time scales are necessary to create laminae of different composition. However, bottom currents may shape similar textures that are difficult to discern from primary seasonal laminae in sediment cores. The millimetre-sized trace fossil Chondrites was commonly found in Cretaceous strata and Recent oxygen-depleted environments where its diameter increased with oxygen levels from 5 to 45 μmol kg−1. This ichnogenus has not been reported from Peruvian sediments but cm-sized crab burrows appeared around 10 μmol kg−1, which may indicate a minimum oxygen value for bioturbated Cretaceous strata. Organic carbon accumulation rates ranged from 0.7 and 2.8 g C cm−2 kyr−1 in laminated sections of OAE 2 in the Tarfaya Basin, Morocco, matching late Holocene accumulation rates of the majority of laminated Peruvian sediment cores under Recent oxygen levels below 5 μmol kg−1. Sediments deposited at >10 μmol kg−1 showed an inverse exponential relationship of bottom-water oxygen levels and organic carbon accumulation depicting enhanced bioirrigation and decomposition of organic matter with increased oxygen supply. In absence of seasonal laminations and under conditions of low burial diagenesis, this relationship may facilitate quantitative estimates of paleo-oxygenation under suboxic conditions. Similarities and differences between Cretaceous OAEs and late Quaternary OMZs have to be further explored to improve our understanding of sedimentary systems under hypoxic conditions.

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Records of past mid-depth ventilation: Cretaceous ocean anoxic event 2 vs. Recent oxygen minimum zones

Biogeosciences ◽

10.5194/bg-12-1169-2015 ◽

2015 ◽

Vol 12 (4) ◽

pp. 1169-1189 ◽

Cited By ~ 10

Author(s):

J. Schönfeld ◽

W. Kuhnt ◽

Z. Erdem ◽

S. Flögel ◽

N. Glock ◽

...

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Bottom Water ◽

Carbon Accumulation ◽

Marine Biota ◽

Accumulation Rates ◽

Oxygen Minimum Zones ◽

Oxygen Levels ◽

Water Oxygen ◽

Oxygen Minimum

Abstract. Present day oceans are well ventilated, with the exception of mid-depth oxygen minimum zones (OMZs) under high surface water productivity, regions of sluggish circulation, and restricted marginal basins. In the Mesozoic, however, entire oceanic basins transiently became dysoxic or anoxic. The Cretaceous ocean anoxic events (OAEs) were characterised by laminated organic-carbon rich shales and low-oxygen indicating trace fossils preserved in the sedimentary record. Yet assessments of the intensity and extent of Cretaceous near-bottom water oxygenation have been hampered by deep or long-term diagenesis and the evolution of marine biota serving as oxygen indicators in today's ocean. Sedimentary features similar to those found in Cretaceous strata were observed in deposits underlying Recent OMZs, where bottom-water oxygen levels, the flux of organic matter, and benthic life have been studied thoroughly. Their implications for constraining past bottom-water oxygenation are addressed in this review. We compared OMZ sediments from the Peruvian upwelling with deposits of the late Cenomanian OAE 2 from the north-west African shelf. Holocene laminated sediments are encountered at bottom-water oxygen levels of < 7 μmol kg−1 under the Peruvian upwelling and < 5 μmol kg−1 in California Borderland basins and the Pakistan Margin. Seasonal to decadal changes of sediment input are necessary to create laminae of different composition. However, bottom currents may shape similar textures that are difficult to discern from primary seasonal laminae. The millimetre-sized trace fossil Chondrites was commonly found in Cretaceous strata and Recent oxygen-depleted environments where its diameter increased with oxygen levels from 5 to 45 μmol kg−1. Chondrites has not been reported in Peruvian sediments but centimetre-sized crab burrows appeared around 10 μmol kg−1, which may indicate a minimum oxygen value for bioturbated Cretaceous strata. Organic carbon accumulation rates ranged from 0.7 and 2.8 g C cm−2 kyr−1 in laminated OAE 2 sections in Tarfaya Basin, Morocco, matching late Holocene accumulation rates of laminated Peruvian sediments under Recent oxygen levels below 5 μmol kg−1. Sediments deposited at > 10 μmol kg−1 showed an inverse exponential relationship of bottom-water oxygen levels and organic carbon accumulation depicting enhanced bioirrigation and decomposition of organic matter with increased oxygen supply. In the absence of seasonal laminations and under conditions of low burial diagenesis, this relationship may facilitate quantitative estimates of palaeo-oxygenation. Similarities and differences between Cretaceous OAEs and late Quaternary OMZs have to be further explored to improve our understanding of sedimentary systems under hypoxic conditions.

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Coastal hypoxia and sediment biogeochemistry

Biogeosciences ◽

10.5194/bg-6-1273-2009 ◽

2009 ◽

Vol 6 (7) ◽

pp. 1273-1293 ◽

Cited By ~ 339

Author(s):

J. J. Middelburg ◽

L. A. Levin

Keyword(s):

Organic Matter ◽

Bottom Water ◽

Water Exchange ◽

Transport Processes ◽

Ecosystem Dynamics ◽

Ecosystem Functions ◽

Oxygen Levels ◽

Concise Review ◽

Water Oxygen ◽

Sediment Biogeochemistry

Abstract. The intensity, duration and frequency of coastal hypoxia (oxygen concentration <63 μM) are increasing due to human alteration of coastal ecosystems and changes in oceanographic conditions due to global warming. Here we provide a concise review of the consequences of coastal hypoxia for sediment biogeochemistry. Changes in bottom-water oxygen levels have consequences for early diagenetic pathways (more anaerobic at expense of aerobic pathways), the efficiency of re-oxidation of reduced metabolites and the nature, direction and magnitude of sediment-water exchange fluxes. Hypoxia may also lead to more organic matter accumulation and burial and the organic matter eventually buried is also of higher quality, i.e. less degraded. Bottom-water oxygen levels also affect the organisms involved in organic matter processing with the contribution of metazoans decreasing as oxygen levels drop. Hypoxia has a significant effect on benthic animals with the consequences that ecosystem functions related to macrofauna such as bio-irrigation and bioturbation are significantly affected by hypoxia as well. Since many microbes and microbial-mediated biogeochemical processes depend on animal-induced transport processes (e.g. re-oxidation of particulate reduced sulphur and denitrification), there are indirect hypoxia effects on biogeochemistry via the benthos. Severe long-lasting hypoxia and anoxia may result in the accumulation of reduced compounds in sediments and elimination of macrobenthic communities with the consequences that biogeochemical properties during trajectories of decreasing and increasing oxygen may be different (hysteresis) with consequences for coastal ecosystem dynamics.

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Coastal hypoxia and sediment biogeochemistry

Biogeosciences Discussions ◽

10.5194/bgd-6-3655-2009 ◽

2009 ◽

Vol 6 (2) ◽

pp. 3655-3706 ◽

Cited By ~ 29

Author(s):

J. J. Middelburg ◽

L. A. Levin

Keyword(s):

Organic Matter ◽

Bottom Water ◽

Water Exchange ◽

Transport Processes ◽

Ecosystem Dynamics ◽

Ecosystem Functions ◽

Oxygen Levels ◽

Concise Review ◽

Water Oxygen ◽

Sediment Biogeochemistry

Abstract. The intensity, duration and frequency of coastal hypoxia (oxygen concentration <63 μM) are increasing due to human alteration of coastal ecosystems and changes in oceanographic conditions due to global warming. Here we provide a concise review of the consequences of coastal hypoxia for sediment biogeochemistry. Changes in bottom-water oxygen levels have consequences for early diagenetic pathways (more anaerobic at expense of aerobic pathways), the efficiency of re-oxidation of reduced metabolites and the nature, direction and magnitude of sediment-water exchange fluxes. Hypoxia may also lead to more organic matter accumulation and burial and the organic matter eventually buried is also of higher quality, i.e. less degraded. Bottom-water oxygen levels also affect the organisms involved in organic matter processing with the contribution of metazoans decreasing as oxygen levels drop. Hypoxia has a significant effect on benthic animals with the consequences that ecosystem functions related to macrofauna such as bio-irrigation and bioturbation are significantly affected by hypoxia as well. Since many microbes and microbial-mediated biogeochemical processes depend on animal induced transport processes (e.g. re-oxidation of particulate reduced sulphur and denitrification), there are indirect hypoxia effects on biogeochemistry via the benthos. Severe long-lasting hypoxia and anoxia may result in the accumulation of reduced compounds in sediments and elimination of macrobenthic communities with the consequences that biogeochemical properties during trajectories of decreasing and increasing oxygen may be different (hysteresis) with consequences for coastal ecosystem dynamics.

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Carbon Sequestration Rate Estimates in Delaware Bay and Barnegat Bay Tidal Wetlands Using Interpolation Mapping

Data ◽

10.3390/data5010011 ◽

2020 ◽

Vol 5 (1) ◽

pp. 11

Author(s):

Champlin ◽

Velinsky ◽

Tucker ◽

Sommerfield ◽

Laurent ◽

...

Keyword(s):

Spatial Analysis ◽

Carbon Sequestration ◽

Organic Carbon ◽

Sediment Cores ◽

Delaware Bay ◽

Carbon Accumulation ◽

Tidal Wetlands ◽

Accumulation Rates ◽

Barnegat Bay ◽

Carbon Accumulation Rates

Quantifying carbon sequestration by tidal wetlands is important for the management of carbon stocks as part of climate change mitigation. This data publication includes a spatial analysis of carbon accumulation rates in Barnegat and Delaware Bay tidal wetlands. One method calculated long-term organic carbon accumulation rates from radioisotope-dated (Cs-137) sediment cores. The second method measured organic carbon density of sediment accumulated above feldspar marker beds. Carbon accumulation rates generated by these two methods were interpolated across emergent wetland areas, using kriging, with uncertainty estimated by leave-one-out cross validation. This spatial analysis revealed greater carbon sequestration within Delaware, compared to Barnegat Bay. Sequestration rates were found to be more variable within Delaware Bay, and rates were greatest in the tidal freshwater area of the upper bay.

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Sedimentation rate and organic matter dynamics shape microbiomes across a continental margin

10.5194/bg-2021-25 ◽

2021 ◽

Author(s):

Sabyasachi Bhattacharya ◽

Tarunendu Mapder ◽

Svetlana Fernandes ◽

Chayan Roy ◽

Jagannath Sarkar ◽

...

Keyword(s):

Fatty Acids ◽

Organic Matter ◽

Organic Carbon ◽

Sedimentation Rate ◽

Bottom Water ◽

Sediment Cores ◽

Sediment Surface ◽

Geochemical Data ◽

Sediment Layer ◽

Shelf Slope

Abstract. Marine sedimentation rate and bottom-water O2 concentration control the remineralization/sequestration of organic carbon across continental margins; but whether/how they shape microbiome architecture (the ultimate effector of all biogeochemical phenomena), across shelf/slope sediments, is unknown. Here we reveal distinct microbiome structures and functions, amidst comparable pore fluid chemistries, along 300 cm sediment horizons underlying the seasonal (shallow coastal) and perennial (deep sea) oxygen minimum zones (OMZs) of the Arabian Sea, situated across the western-Indian margin (water-depths: 31 m and, 530 and 580 m, respectively). The sedimentary geomicrobiology was elucidated by analyzing metagenomes, metatranscriptomes, and enrichment cultures, and also sedimentation rates measured by radiocarbon and lead excess (210Pbxs); the findings were then evaluated in the light of the other geochemical data available for the cores investigated. Along the perennial- and seasonal-OMZ sediment cores, microbial communities were dominated by Gammaproteobacteria and Alphaproteobacteria, and Euryarchaeota and Firmicutes, respectively. As a perennial-OMZ signature, a cryptic methane production-consumption cycle was found to operate near the sediment-surface (within the sulfate reduction zone); overall diversity, as well as the relative abundances of simple-fatty-acids-requiring anaerobes (methanogens, anaerobic methane-oxidizers, sulfate-reducers and acetogens), peaked in the topmost sediment-layer and then declined via synchronized fluctuations until the sulfate-methane transition zone was reached. The entire microbiome profile was reverse in the seasonal-OMZ sediment horizon. In the perennial-OMZ sediments organic carbon deposited was higher in concentration and marine components-rich, so it potentially degraded readily to simple fatty acids; lower sedimentation rate afforded higher O2 exposure time for organic matter degradation despite perennial hypoxia in the bottom-water; thus, the resultant abundance of reduced carbon substrates sustained multiple inter-competing microbial processes in the upper sediment-layers. Remarkably, the whole geomicrobial scenario was opposite in the sediments of the seasonal/shallow-water OMZ. Our findings create a microbiological baseline for understanding carbon-sulfur cycling across distinct marine depositional settings and water-column oxygenation regimes.

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Sedimentation rate and organic matter dynamics shape microbiomes across a continental margin

10.1101/2020.10.03.324590 ◽

2020 ◽

Author(s):

Sabyasachi Bhattacharya ◽

Tarunendu Mapder ◽

Svetlana Fernandes ◽

Chayan Roy ◽

Jagannath Sarkar ◽

...

Keyword(s):

Fatty Acids ◽

Organic Matter ◽

Organic Carbon ◽

Sedimentation Rate ◽

Bottom Water ◽

Sediment Cores ◽

Sediment Surface ◽

Sediment Layer ◽

Depositional Settings ◽

Shelf Slope

AbstractMarine sedimentation rate and bottom-water O2 concentration control the remineralization/sequestration of organic carbon across continental margins; but whether/how they shape microbiome architecture (the ultimate effector of all biogeochemical phenomena), across shelf/slope sediments, is unknown. Here we reveal distinct microbiome structures and functions, amidst comparable pore-fluid chemistries, along ~3 m sediment-horizons underlying the seasonal (shallow coastal) and perennial (deep sea) oxygen minimum zones (OMZs) of the Arabian Sea, situated across the western-Indian margin (water-depths: 31 m and, 530 and 580 m, respectively). Along the perennial- and seasonal-OMZ sediment-cores microbial communities were predominated by Gammaproteobacteria/Alphaproteobacteria and Euryarchaeota/Firmicutes respectively. As a perennial-OMZ signature, a cryptic methane production-consumption cycle was found to operate near the sediment-surface; overall diversity, as well as the relative abundances of simple-fatty-acids-requiring anaerobes (methanogens, anaerobic methane-oxidizers, sulfate-reducers and acetogens), peaked in the topmost sediment-layer and then declined via synchronized fluctuations until the sulfate-methane transition zone was reached. The entire microbiome profile was reverse in the seasonal-OMZ sediment-horizon. We discerned that in the perennial-OMZ sediments organic carbon deposited was higher in concentration, and marine components-rich, so it potentially degraded readily to simple fatty acids; lower sedimentation rate afforded higher O2 exposure time for organic matter degradation despite perennial hypoxia in the bottom-water; thus, the resultant abundance of reduced metabolites sustained multiple inter-competing microbial processes in the upper sediment-layers. Remarkably, the whole geomicrobial scenario was opposite in the sediments of the seasonal/shallow-water OMZ. Our findings create a microbiological baseline for understanding carbon-sulfur cycling across distinct marine depositional settings and water-colum n oxygenation regimes.

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Distribution and origin of organic matter in the Baltic Sea sediments dated with 210Pb and 137Cs

Geochronometria ◽

10.2478/s13386-011-0058-x ◽

2012 ◽

Vol 39 (1) ◽

pp. 1-9 ◽

Cited By ~ 29

Author(s):

Aleksandra Szczepańska ◽

Agata Zaborska ◽

Anna Maciejewska ◽

Karol Kuliński ◽

Janusz Pempkowiak

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Carbon Cycle ◽

Baltic Sea ◽

Sediment Accumulation ◽

Carbon Accumulation ◽

Accumulation Rates ◽

The Baltic Sea ◽

The Baltic ◽

Carbon Accumulation Rates

Abstract Organic carbon deposited in marine sediments is an important part of the global carbon cycle. The knowledge concerning the role of shelf seas (including the Baltic Sea) in the carbon cycle has increased substantially, however organic carbon accumulation rates in the Baltic sediments still require clarification. This paper describes methods used for assessing organic carbon and nitrogen accumulation rates in six sediment cores collected in the sediment accumulation areas in the Baltic Sea. Mass sediment accumulation rates were based on 210Pb method validated by 137Cs measurements. The organic carbon accumulation rates ranged from 18 to 75 g·C·m−2·yr−1. The C/N ratios and δ13C were used to access sedimentary organic matter provenance. The C/N ratios in the investigated cores vary in the range from 7.4 to 9.6, while δ13C ranged from −24.4‰ to −26.4‰. Results of the terrestrial organic matter contribution in the sedimentary organic matter were calculated basing on δ13C using the end member approach. Large proportion (41–73%) of the sedimentary organic carbon originates on land. The obtained results indicate the Baltic Sea sediments as an important sink for organic carbon. Substantial fraction of the sedimentary load originates on land.

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

Biogeosciences ◽

10.5194/bg-17-3165-2020 ◽

2020 ◽

Vol 17 (12) ◽

pp. 3165-3182

Author(s):

Zeynep Erdem ◽

Joachim Schönfeld ◽

Anthony E. Rathburn ◽

Maria-Elena Pérez ◽

Jorge Cardich ◽

...

Keyword(s):

Bottom Water ◽

Sediment Cores ◽

Lower Boundary ◽

Climatic Conditions ◽

Last Deglaciation ◽

Oxygen Minimum Zones ◽

Proxy Records ◽

Water Deoxygenation ◽

The Last Deglaciation ◽

Oxygen Minimum

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.

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Multiproxy sedimentological and geochemical analyses across the Lower–Middle Pleistocene boundary: chemostratigraphy and paleoenvironment of the Chiba composite section, central Japan

Progress in Earth and Planetary Science ◽

10.1186/s40645-020-00393-5 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Kentaro Izumi ◽

Yuki Haneda ◽

Yusuke Suganuma ◽

Makoto Okada ◽

Yoshimi Kubota ◽

...

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Bottom Water ◽

Middle Pleistocene ◽

Oxygen Level ◽

Terrigenous Material ◽

Central Japan ◽

Water Oxygen ◽

Composite Section ◽

Geochemical Analyses

AbstractThe Chiba composite section (CbCS) in the Kokumoto Formation, Kazusa Group, central Japan is a thick and continuous marine succession that straddles the Lower–Middle Pleistocene boundary and the well-recognized Matuyama–Brunhes paleomagnetic polarity boundary. Although recent studies extensively investigated the CbCS, its chemostratigraphy, particularly around the Lower–Middle Pleistocene boundary, is poorly understood. Therefore, in this study, we performed multiproxy sedimentological and geochemical analyses of the CbCS, including the Chiba section, which is the Global Boundary Stratotype Section and Point for defining the base of the Middle Pleistocene Subseries. The aim of these analyses is to establish the high-resolution chemostratigraphy and to reconstruct the paleoenvironments of its sedimentary basin in detail. We used the K/Ti ratio as a broad proxy for the clastic material grain size of the sediments. Although the K/Ti ratio generally varies throughout the studied interval, the K/Ti ratio especially during Marine Isotope Stage (MIS) 19a shows a variation pattern like those of the foraminiferal oxygen isotope (δ18O) records. The records of the C/N ratio of bulk samples and carbon isotope ratio of the organic carbon (δ13Corg) suggest that the organic matter in the CbCS sediments during MIS 19c mostly originated from marine plankton, whereas the organic matter during MIS 18 and 19a was characterized by a mixture of marine plankton and terrestrial plants. These records are clearly indicative of changes in mixing ratio of marine vs. terrestrial organic matter in association with glacial–interglacial cycles from the late MIS 20 to the early MIS 18. In addition, we calculated the mass accumulation rates (MARs) of organic carbon, biogenic carbonate, and terrigenous material for quantitative interpretations on the paleoenvironmental changes. MAR calculations revealed that the contribution of marine organic carbon relative to terrestrial organic carbon increased during MIS 19c, and that the contribution of the terrigenous material relative to biogenic carbonate decreased during MIS 19c. Furthermore, we observed relatively large variations in the total organic carbon and total nitrogen contents during MIS 19a. These variations were probably caused by the relative decrease in bottom-water oxygen level, which is also supported by our trace-fossil data, although it is not certain whether the increase in organic-carbon flux at ~ 760 ka was due to the synchronous increase in biogenic productivity in surface water. Such a relative decrease in bottom-water oxygen level was partly due to the increased ocean stratification because of the northward displacement of the Kuroshio Extension Front.

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