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Sensitivity of the thermohaline circulation during the Messinian: Toward constraining the dynamics of Mediterranean deoxygenation

Abstract.

"During the Messinian, the sensitivity of the Mediterranean Basin to ecosystem perturbation was enhanced in response to the progressive restriction of water exchange with the Atlantic Ocean. The widespread deposition of organic-rich layers (i.e. sapropel) during the Messinian testifies the perturbation of the carbon and oxygen cycles; indeed, these sediments were deposited under conditions of oxygen starvation, presumably in response to a periodic deterioration of the thermohaline circulation strength. [...]".

 

Source: Science Direct 
Authors: Alan Maria Mancini et al.
DOI: https://doi.org/10.1016/j.dsr.2023.104217

Read the full article here.


Benthic foraminifera and gromiids from oxygen-depleted environments – survival strategies, biogeochemistry and trophic interactions

Abstract.

"The oceans are losing oxygen (O2), and oxygen minimum zones are expanding due to climate warming (lower O2 solubility) and eutrophication related to agriculture. This trend is challenging for most marine taxa that are not well adapted to O2 depletion. For other taxa this trend might be advantageous because they can withstand low O2 concentrations or thrive under O2-depleted or even anoxic conditions. Benthic foraminifera are a group of protists that include taxa with adaptations to partly extreme environmental conditions. [...]".

 

Source: Biogeosciences
Authors: Nicolaas Glock
DOI: https://doi.org/10.5194/bg-20-3423-2023

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Cretaceous southern high latitude benthic foraminiferal assemblages during OAE 2 at IODP Site U1516, Mentelle Basin, Indian Ocean

Abstract.

"At Site U1516 (Mentelle Basin, southeast Indian Ocean, offshore western Australia), the International Ocean Discovery Program (IODP) Expedition 369 recovered an almost complete pelagic record of the Upper Cretaceous, including the Oceanic Anoxic Event 2 (OAE 2). To better understand paleoenvironmental changes across OAE 2, 32 samples were analysed for benthic foraminiferal abundance data that represent one of the few benthic foraminiferal datasets spanning the OAE 2 in the southern high latitudes. [...]".

 

Source: Science Direct
Authors: Erik Wolfgring et al.
DOI: https://doi.org/10.1016/j.cretres.2023.105555

Read the full article here.


Reconstructing ocean oxygenation changes from U/Ca and U/Mn in foraminiferal coatings: Proxy validation and constraints on glacial oxygenation changes

Abstract. 

"Deep-sea oxygen concentrations reflect combined effects of air-sea exchange in high-latitude surface waters, ventilation through ocean circulation and the organic carbonremineralization at depth. Reconstruction of past bottom water oxygen (BWO) concentrations has been challenging due to limitations of each existing BWO proxy whose fidelity may be complicated by diagenetic or depositional factors. Therefore, evaluations on BWO changes with multi-proxy approach are always preferred. In this study, we exploit the authigenic uranium content on mixed planktonic foraminiferal coatings as a BWO proxy by presenting new foraminiferal [...]".

 

Source: Science Direct
Authors: Rong Hu et al.
DOI: https://doi.org/10.1016/j.quascirev.2023.108028

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Spatial heterogeneity in benthic foraminiferal assemblages tracks regional impacts of paleoenvironmental change across Cretaceous OAE2

Abstract. 

"The impact of global climate events on local ecosystems can vary spatially. Understanding this potential heterogeneity can illuminate which environments will be most impacted and the proximal drivers of ecosystem responses. Cenomanian–Turonian marine deposits of the Western Interior Seaway (WIS) record paleoceanographic changes associated with the Greenhorn transgression and the onset of Oceanic Anoxic Event 2 (OAE2). They provide an ideal setting to study basin-wide paleoecological responses during a global perturbation. [...]".

 

Source: Cambridge University Press
Authors: Raquel Bryant & Christina L. Belanger
DOI: https://doi.org/10.1017/pab.2022.47

Read the full article here.


Calcium isotope ratios of malformed foraminifera reveal biocalcification stress preceded Oceanic Anoxic Event 2

Abstract. 

"Ocean acidification causes biocalcification stress. The calcium isotope composition of carbonate producers can archive such stress because calcium isotope fractionation is sensitive to precipitation rate. Here, we synthesize morphometric observations of planktic foraminifera with multi-archive calcium isotope records from Gubbio, Italy and the Western Interior Seaway spanning Cretaceous Ocean Anoxic Event 2 (~94 million years ago). Calcium isotope ratios increase ~60 thousand years prior to the event. [...]". 

 

Source: Nature
Authors: Gabriella D. Kitch et al.
DOI: https://doi.org/10.1038/s43247-022-00641-0

Read the full article here.


Placing North Pacific paleo-oxygenation records on a common scale using multivariate analysis of benthic foraminiferal assemblages

Abstract. 

"Dysoxic events are well-studied in Pleistocene and Holocene marine sediment records from the North Pacific using faunal, sedimentological, and geochemical paleo-oxygenation proxies. However, differences in proxy sensitivity and local conditions make it difficult to quantify the relative severity of dysoxia across the North Pacific. Here, we use multivariate analyses of taxonomically standardized benthic foraminiferal assemblages to quantitatively compare the severity and duration of dysoxic events at four intermediate depth sites within oxygen minimum zones in the Gulf of Alaska (GoA), Santa Barbara Basin, and Baja California Sur. Unlike previous faunal dissolved oxygen indices, the metric developed here incorporates the total faunal assemblage and is better correlated with co-registered geochemical proxies. [...]". 

 

Source: Science Direct

Authors: Sharon Sharon et al.

DOI: https://doi.org/10.1016/j.quascirev.2022.107412

Read the full article here.


Calculating dissolved marine oxygen values based on an enhanced Benthic Foraminifera Oxygen Index

Abstract. 

"Marine oxygen minimum zones (OMZs) trap greenhouse gases, reduce livable habitats, a critical factor for these changes is the amount of dissolved oxygen (DO). The frequently used tool to reconstruct DO values, the Benthic Foraminifera Oxygen Index (BFOI), showed major shortcomings and lacks effectiveness. Therefore, we enhanced the BFOI and introduce enhanced BFOI (EBFOI) formulas by using all available data benthic foraminifers provide, calculating the whole livable habitat of benthic foraminifers, including bottom water oxygenation (BWO) and pore water oxygenation (PWO). Further, we introduce for the first time a transfer function to convert EBFOI vales directly into DO values, increasing efficiency by up to 38%. [...]".

 

Source: Nature Scientific Reports

Authors: Matthias Kranner et al. 

DOI: https://doi.org/10.1038/s41598-022-05295-8

Read the full article here.


I/Ca in epifaunal benthic foraminifera: A semi-quantitative proxy for bottom water oxygen in a multi-proxy compilation for glacial ocean deoxygenation

Abstract.

"The decline in dissolved oxygen in global oceans (ocean deoxygenation) is a potential consequence of global warming which may have important impacts on ocean biogeochemistry and marine ecosystems. Current climate models do not agree on the trajectory of future deoxygenation on different timescales, in part due to uncertainties in the complex, linked effects of changes in ocean circulation, productivity and organic matter respiration. [...]"

Source: Earth and Planetary Science Letters
Authors: Wanyi Lu et al.
DOI: 10.1016/j.epsl.2019.116055


Neritic ecosystem response to Oceanic Anoxic Event 2 in the Cretaceous Western Interior Seaway, USA

Abstract.

"Cretaceous oceanic anoxic events (OAEs) were periods of geologically short (<1 million years) global change characterized by elevated temperatures, changes in ocean biogeochemistry, ecological turnover, and the global-scale deposition of black shales. After decades of OAE research, the intensity and spatiotemporal heterogeneity of ocean anoxia and its direct effects on marine ecology remain areas of active study. We present high-resolution organic geochemical and foraminiferal records from the western margin of the Western Interior Seaway (WIS) during the Cenomanian-Turonian Oceanic Anoxic Event 2 (OAE2, ~94 Ma) that indicate reorganization of a neritic ecosystem in response to sea-level rise, and dynamic changes in redox conditions that were likely driven by enhanced marine productivity. [...]"

Source: Palaeogeography, Palaeoclimatology, Palaeoecology
Authors: F. Garrett Boudinot et al.
DOI: 10.1016/j.palaeo.2020.109673

Read the full article here.


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