The surface ocean productivity and bottom water oxygen signals in deep water benthic foraminiferal assemblages

Abstract. The importance of particulate organic carbon and phosphorus (P) delivered from shelves on open ocean productivity, oxygen, and reactive P burial during glacial times has been assessed using a biogeochemical ocean model of the carbon (C), P and iron cycles. The model shows that in simulations of the Last Glacial Maximum (LGM) without any inputs of terrigenous material from shelves there is a moderate increase in productivity (+5 %) and mean deep water oxygen (+29 %) relative to the preindustrial simulation. However, when the input of terrigenous particulate organic C and P is considered as an additional forcing in the LGM simulation, ocean productivity increases by 46 %, mean deep water oxygen concentration decreases by 20 %, and the global rate of reactive P burial is 3 times over the preindustrial value. The associated pattern of negative oxygen anomalies at 1000 m induces a deepening of the Atlantic and Indian Ocean oxygen minimum (OMZ), while in the Pacific Ocean the OMZ is shifted to the eastern basin north of the Equator relative to preindustrial times. In addition, negative trends in oxygen extend globally below 2000 m depth, though their magnitude is rather weak, and in particular bottom waters remain above suboxic levels. Changes in dust deposition can be responsible for positive trends in reactive P burial as simulated at the LGM in open ocean regions, notably over the Southwest Atlantic and Northwest Pacific; on the other hand, inputs of terrigenous material from shelves cause an increase in P burial over the continental slope and rise regions which accounts for 47 % of the total reactive P burial change. Although the glacial-interglacial trends in P burial in our model compare well with the available observations, this study highlights the need of much more core records of C and P in open ocean settings.

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A seventy-two-year record of diminishing deep-water oxygen in the St. Lawrence estuary: The northwest Atlantic connection

Limnology and Oceanography ◽

10.4319/lo.2005.50.5.1654 ◽

2005 ◽

Vol 50 (5) ◽

pp. 1654-1666 ◽

Cited By ~ 123

Author(s):

Denis Gilbert ◽

Bjorn Sundby ◽

Charles Gobeil ◽

Alfonso Mucci ◽

Gilles-H. Tremblay

Keyword(s):

Deep Water ◽

Northwest Atlantic ◽

Lawrence Estuary ◽

Water Oxygen ◽

St Lawrence Estuary

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14C in the Deep Water of the East Atlantic

Radiocarbon ◽

10.1017/s0033822200007505 ◽

1986 ◽

Vol 28 (2A) ◽

pp. 391-396 ◽

Cited By ~ 2

Author(s):

Reiner Schlitzer

Keyword(s):

Deep Water ◽

Large Scale ◽

Bottom Water ◽

Source Parameters ◽

Potential Temperature ◽

Source Terms ◽

East Atlantic ◽

The West ◽

Model Calculations ◽

Inflowing Water

The renewal of east Atlantic deep water and its large-scale circulation and mixing have been studied in observed distributions of temperature, silicate, ΣCO2, and 14C. 14C variations in northeast Atlantic deep water below 3500m depth are small. Δ14C values range from − 100‰ to −125‰. 14C bottom water concentrations decrease from Δ14C =−117‰ in the Sierra Leone Basin to Δ14C = − 123‰ in the Iberian Basin and are consistent with a mean northward bottom water flow. The characteristic of the water that flows from the west Atlantic through the Romanche Trench into the east Atlantic was determined by inspection of θ/Δ14C and θ/SiO2 diagrams. A mean potential temperature of θ = 1.50 ± .05°C was found for the inflowing water. A multi-box model including circulation, mixing, and chemical source terms in the deep water has been formulated. Linear programing and least-squares techniques have been used to obtain the transport and source parameters of the model from the observed tracer fields. Model calculations reveal an inflow through the Romanche Trench from the west Atlantic, which predominates over any other inflow, of (5 ± 2) Sv (potential temperature 1.50°C), a convective turnover of (150 ± 50) years and a vertical apparent diffusivity of (4 ± 1) cm2/s. Chemical source terms are in the expected ranges.

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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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Review of "Characterizing deep-water oxygen variability and seafloor community responses using a novel autonomous lander” written by Natalya D. Gallo, Kevin Hardy, Nicholas C. Wegner, Ashley Nicoll, Haleigh Yang, and Lisa A. Levin

10.5194/bg-2020-75-rc1 ◽

2020 ◽

Author(s):

SungHyun Nam

Keyword(s):

Deep Water ◽

Community Responses ◽

Water Oxygen

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

10.7185/gold2021.4601 ◽

2021 ◽

Author(s):

Ricardo Monedero-Contreras ◽

Francisca Martinez-Ruiz ◽

Francisco J. Rodríguez-Tovar ◽

David Gallego-Torres ◽

Gert J. de Lange

Keyword(s):

Bottom Water ◽

Oxygen Depletion ◽

Water Oxygen ◽

Oxygen Conditions

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Extreme Transport Velocities of Antarctic Bottom Water in the Deep-Water Vema Channel

Doklady Earth Sciences ◽

10.1134/s1028334x19060060 ◽

2019 ◽

Vol 486 (2) ◽

pp. 659-662 ◽

Cited By ~ 1

Author(s):

E. G. Morozov ◽

D. I. Frey ◽

V. G. Neiman ◽

N. I. Makarenko ◽

R. Yu. Tarakanov

Keyword(s):

Deep Water ◽

Bottom Water ◽

Antarctic Bottom Water

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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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