Oxygen depletion during sapropel deposition: Reassessing redox proxies for reconstructing surface and bottom water oxygen conditions

Abstract The history of Burlington Bay for the last 8,400 years has recorded two significant changes in its environment. The first occurred about 2,540 years ago, resulting from a change in mean annual temperature. This, in turn, changed the chemistry of the bay water. The second change occurred about 125 years ago (ca. 1865 A.D.). This time, it was the impact of agricultural practices and industrialization. Agricultural practices caused the lake to become eutrophic. This rapidly (within 40 years) changed the bottom water oxygen conditions to anaerobic. Industrialization had an impact on the fauna and the flora. Some fauna became locally extinct while some phytoplankton became deformed.

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Rapid changes in primary productivity and oxygen depletion during sapropel deposition: implications for reconstructing seawater oxygen levels

10.5194/egusphere-egu21-2240 ◽

2021 ◽

Author(s):

Ricardo D. Monedero-Contreras ◽

Francisca Martinez-Ruiz ◽

Francisco J. Rodríguez-Tovar ◽

David Gallego-Torres ◽

Gert de Lange

Keyword(s):

Bottom Water ◽

Eastern Mediterranean ◽

Oxygen Depletion ◽

Enrichment Factors ◽

Water Interface ◽

Enhanced Production ◽

Monsoon Variability ◽

Oxygen Conditions ◽

Natural Archive ◽

High Resolution Reconstruction

<p>The deposition of Organic-Rich Layers (ORLs) and sapropels in the Mediterranean Sea basins represents an exceptional record of severe changes in oxygenation over the recent geological past. Such changes are also associated to rapid productivity oscillations that involved a major increase in export fluxes of organic carbon. These episodes of enhanced production and preservation of organic matter can be used as a natural archive for studying oxygen fluctuations and deoxygenation events, and a better comprehension of the causes and consequences of past events will provide valuable information to further understand oxygen level variations in future scenarios. In general, sapropel deposition has been related to increased productivity and sluggish water circulation in response to African monsoon variability. To further understand how such conditions led to bottom water oxygen depletion, a multiproxy approach, including diverse geochemical and ichnological proxies, has been applied. Obtained results have provided new insights into the relationship between productivity and oxygen conditions in the water column and at the sediment-water interface. Sapropels intervals from cores recovered at four ODP Leg 160 sites were selected across an East-West transect of the Eastern Mediterranean basin entailing diverse depths and oceanographic regimes. At these sites, sapropel layers had been well characterized in terms of productivity (i.e. Ba/Al and TOC), and new analyses have been performed to provide additional redox proxies, i.e. degree of pyritization (DOP), trace elements ratios, and enrichment factors (EF) that have allowed a high-resolution reconstruction of bottom-water ventilation. Also, a preliminary ichnological approach is coupled with the geochemical information to assess the response of the macrobenthic trace maker community to the redox changes at the sediment-water interface. Trace metal proxies indicate a significant, though variable, decreasing oxygenation during sapropel deposition, also supported by important pyritization within sapropel layers.</p>

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Investigating hypoxia in aquatic environments: diverse approaches to addressing a complex phenomenon

Biogeosciences ◽

10.5194/bg-11-1215-2014 ◽

2014 ◽

Vol 11 (4) ◽

pp. 1215-1259 ◽

Cited By ~ 113

Author(s):

J. Friedrich ◽

F. Janssen ◽

D. Aleynik ◽

H. W. Bange ◽

N. Boltacheva ◽

...

Keyword(s):

Climate Change ◽

Spatial Patterns ◽

Bottom Water ◽

Oxygen Depletion ◽

Aquatic Systems ◽

In Situ Monitoring ◽

Aquatic Environments ◽

Basin Scale ◽

Gas Seepage ◽

Oxygen Conditions

Abstract. In this paper we provide an overview of new knowledge on oxygen depletion (hypoxia) and related phenomena in aquatic systems resulting from the EU-FP7 project HYPOX ("In situ monitoring of oxygen depletion in hypoxic ecosystems of coastal and open seas, and landlocked water bodies", http://www.hypox.net). In view of the anticipated oxygen loss in aquatic systems due to eutrophication and climate change, HYPOX was set up to improve capacities to monitor hypoxia as well as to understand its causes and consequences. Temporal dynamics and spatial patterns of hypoxia were analyzed in field studies in various aquatic environments, including the Baltic Sea, the Black Sea, Scottish and Scandinavian fjords, Ionian Sea lagoons and embayments, and Swiss lakes. Examples of episodic and rapid (hours) occurrences of hypoxia, as well as seasonal changes in bottom-water oxygenation in stratified systems, are discussed. Geologically driven hypoxia caused by gas seepage is demonstrated. Using novel technologies, temporal and spatial patterns of water-column oxygenation, from basin-scale seasonal patterns to meter-scale sub-micromolar oxygen distributions, were resolved. Existing multidecadal monitoring data were used to demonstrate the imprint of climate change and eutrophication on long-term oxygen distributions. Organic and inorganic proxies were used to extend investigations on past oxygen conditions to centennial and even longer timescales that cannot be resolved by monitoring. The effects of hypoxia on faunal communities and biogeochemical processes were also addressed in the project. An investigation of benthic fauna is presented as an example of hypoxia-devastated benthic communities that slowly recover upon a reduction in eutrophication in a system where naturally occurring hypoxia overlaps with anthropogenic hypoxia. Biogeochemical investigations reveal that oxygen intrusions have a strong effect on the microbially mediated redox cycling of elements. Observations and modeling studies of the sediments demonstrate the effect of seasonally changing oxygen conditions on benthic mineralization pathways and fluxes. Data quality and access are crucial in hypoxia research. Technical issues are therefore also addressed, including the availability of suitable sensor technology to resolve the gradual changes in bottom-water oxygen in marine systems that can be expected as a result of climate change. Using cabled observatories as examples, we show how the benefit of continuous oxygen monitoring can be maximized by adopting proper quality control. Finally, we discuss strategies for state-of-the-art data archiving and dissemination in compliance with global standards, and how ocean observations can contribute to global earth observation attempts.

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Evidence for differential degradation of alkenones under contrasting bottom water oxygen conditions: implication for paleotemperature reconstruction

Geochimica et Cosmochimica Acta ◽

10.1016/s0016-7037(98)00283-x ◽

1999 ◽

Vol 63 (3-4) ◽

pp. 405-411 ◽

Cited By ~ 104

Author(s):

Changrui Gong ◽

David J Hollander

Keyword(s):

Bottom Water ◽

Water Oxygen ◽

Oxygen Conditions ◽

Differential Degradation

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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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Correlation of <i>Virgulinella fragilis</i> Grindell & Collen (benthic foraminiferid) with near-anoxia in Aso-kai Lagoon, central Japan

Journal of Micropalaeontology ◽

10.1144/jm.24.2.159 ◽

2005 ◽

Vol 24 (2) ◽

pp. 159-167 ◽

Cited By ~ 9

Author(s):

Hiroyuki Takata ◽

Koji Seto ◽

Saburo Sakai ◽

Satoshi Tanaka ◽

Katsumi Takayasu

Keyword(s):

Cluster Analysis ◽

Pore Water ◽

Coastal Lagoon ◽

Bottom Water ◽

Low Oxygen ◽

Central Japan ◽

Reactive Iron ◽

Predominant Species ◽

Oxygen Conditions ◽

Cluster A

Abstract. The distribution of Virgulinella fragilis and the hydro-environment of Aso-kai Lagoon, central Japan, were studied to clarify the foraminifer’s adaptation to low-oxygen conditions. The hypolimnion of the lagoon is oxygen-poor during much of the year. Two faunas (A and B) are recognized, based on cluster analysis. Cluster A fauna consists of species common in brackish lagoons, such as the genera Trochammina and Ammonia, and occurs in seasonally oxygenated waters. Virgulinella fragilis, the predominant species of Cluster B fauna, dominates the central part of the lagoon. This species can tolerate more severe oxygen deficiencies than the typical brackish foraminifers (e.g. Trochammina spp.) and can adapt to long periods of oxygen-poor conditions in coastal lagoon environments, as well as in pelagic to hemi-pelagic settings. In order to survive in the near-anoxia of Aso-kai Lagoon, V. fragilis may have adapted to environments in which little reactive iron is available in the sediment, leaving pore-water and bottom-water sulphide available for symbionts, or may utilize sulphur denitrification processes.

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A comparison of benthic foraminiferal Mn / Ca and sedimentary Mn / Al as proxies of relative bottom-water oxygenation in the low-latitude NE Atlantic upwelling system

Biogeosciences ◽

10.5194/bg-12-5415-2015 ◽

2015 ◽

Vol 12 (18) ◽

pp. 5415-5428 ◽

Cited By ~ 22

Author(s):

C. L. McKay ◽

J. Groeneveld ◽

H. L. Filipsson ◽

D. Gallego-Torres ◽

M. J. Whitehouse ◽

...

Keyword(s):

Inductively Coupled Plasma ◽

Bottom Water ◽

Secondary Ion Mass Spectrometry ◽

Younger Dryas ◽

Icp Oes ◽

Low Oxygen ◽

Ne Atlantic ◽

Low Latitude ◽

Upwelling System ◽

Oxygen Conditions

Abstract. Trace element incorporation into foraminiferal shells (tests) is governed by physical and chemical conditions of the surrounding marine environment, and therefore foraminiferal geochemistry provides a means of palaeo-oceanographic reconstructions. With the availability of high-spatial-resolution instrumentation with high precision, foraminiferal geochemistry has become a major research topic over recent years. However, reconstructions of past bottom-water oxygenation using foraminiferal tests remain in their infancy. In this study we explore the potential of using Mn / Ca determined by secondary ion mass spectrometry (SIMS) as well as by flow-through inductively coupled plasma optical emission spectroscopy (FT-ICP-OES) in the benthic foraminiferal species Eubuliminella exilis as a proxy for recording changes in bottom-water oxygen conditions in the low-latitude NE Atlantic upwelling system. Furthermore, we compare the SIMS and FT-ICP-OES results with published Mn sediment bulk measurements from the same sediment core. This is the first time that benthic foraminiferal Mn / Ca is directly compared with Mn bulk measurements, which largely agree on the former oxygen conditions. Samples were selected to include different productivity regimes related to Marine Isotope Stage 3 (35–28 ka), the Last Glacial Maximum (28–19 ka), Heinrich Event 1 (18–15.5 ka), Bølling Allerød (15.5–13.5 ka) and the Younger Dryas (13.5–11.5 ka). Foraminiferal Mn / Ca determined by SIMS and FT-ICP-OES is comparable. Mn / Ca was higher during periods with high primary productivity, such as during the Younger Dryas, which indicates low-oxygen conditions. This is further supported by the benthic foraminiferal faunal composition. Our results highlight the proxy potential of Mn / Ca in benthic foraminifera from upwelling systems for reconstructing past variations in oxygen conditions of the sea floor environment as well as the need to use it in combination with other proxy records such as faunal assemblage data.

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Foraminiferal response to Albian relative sea-level changes in northwestern and central Alberta, Canada

Canadian Journal of Earth Sciences ◽

10.1139/e99-079 ◽

1999 ◽

Vol 36 (10) ◽

pp. 1617-1643 ◽

Cited By ~ 6

Author(s):

Rebecca A Stritch ◽

Claudia J Schröder-Adams

Keyword(s):

Sea Level ◽

Bottom Water ◽

Gradual Increase ◽

Western Canada ◽

Sea Level Changes ◽

Relative Sea Level ◽

Sea Level Fluctuations ◽

Faunal Assemblages ◽

Water Oxygen ◽

Southern Alberta

Albian foraminiferal assemblages from three wells in northwestern (Imperial Spirit River No. 1, 12-20-78-6W6), central (AngloHome C&E Fort Augustus No. 1, 7-29-55-21W4), and southern Alberta (Amoco B1 Youngstown, 6-34-30-8W4) provide the basis to track a fluctuating sea-level history in western Canada. Two global second-order marine cycles (Kiowa - Skull Creek and Greenhorn) were punctuated by higher frequency relative sea-level cycles expressed during the time of the Moosebar-Clearwater, Hulcross, Joli Fou, and Mowry seas. A total of 34 genera and 93 subgeneric taxa are recognized in these Albian-age strata. Foraminiferal abundance and species diversity of the latest Albian Mowry Sea were higher than in the early to middle Albian Moosebar-Clearwater and Hulcross seas. The two earliest paleo-seas were shallow embayments of the Boreal Sea, and relative sea-level fluctuations caused variable marine to brackish conditions expressed in a variety of faunal assemblages. Towards the late Albian, relative sea level rose, deepening the basin and establishing increased marine conditions and more favourable habitats for foraminifera. In the deeper Joli Fou Seaway and Mowry Sea, however, reduced bottom water oxygen through stratification or stagnant circulation caused times of diminished benthic faunas. The Bluesky Formation in northwestern Alberta contains the initial transgression of the early Albian Moosebar-Clearwater Sea and is marked by a sudden faunal increase. In contrast, transgression by the late late Albian Mowry Sea was associated with a gradual increase of foraminiferal faunas. Numerous agglutinated species range throughout the entire Albian, absent only at times of basin shallowing. However, each major marine incursion throughout the Albian introduced new taxa.

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