News

Microscale dynamics promote segregated denitrification in diatom aggregates sinking slowly in bulk oxygenated seawater

Abstract.

"Sinking marine particles drive the biological pump that naturally sequesters carbon from the atmosphere. Despite their small size, the compartmentalized nature of particles promotes intense localized metabolic activity by their bacterial colonizers. Yet the mechanisms promoting the onset of denitrification, a metabolism that arises once oxygen is limiting, remain to be established. Here we show experimentally that slow sinking aggregates composed of marine diatoms—important primary producers for global carbon export—support active denitrification even among bulk oxygenated water typically thought to exclude anaerobic metabolisms. [...]".

 

Source: Nature
Authors: Davide Ciccarese et al.
DOI: https://doi.org/10.1038/s43247-023-00935-x

Read the full article here.


Sulfur isotopic evidence for global marine anoxia and low seawater sulfate concentration during the Late Triassic

Abstract.

"Marine anoxia during the Late Triassic has mostly been reported from the western Tethysand Panthalassa, which were near the Central Atlantic Magmatic Province (CAMP), but whether it developed in global open oceans (e.g., the eastern Tethys) is unknown. Whether the marine anoxia was global or regional requires more research. Here, we present carbonate-associated sulfate (CAS) and pyrite δ34Spy data for the Late Triassic–Early Jurassic interval from the Wenquan Section in Qiantang Basin, Tibet. [...]".

 

Source: Science Direct
Authors: Wei Tang et al.
DOI: https://doi.org/10.1016/j.jseaes.2023.105659

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Sulfate triple-oxygen-isotope evidence confirming oceanic oxygenation 570 million years ago

Abstract.

"The largest negative inorganic carbon isotope excursion in Earth’s history, namely the Ediacaran Shuram Excursion (SE), closely followed by early animal radiation, has been widely interpreted as a consequence of oceanic oxidation. However, the primary nature of the signature, source of oxidants, and tempo of the event remain contested. Here, we show that carbonate-associated sulfate (CAS) from three different paleocontinents all have conspicuous negative 17O anomalies (Δ′17OCAS values down to −0.53‰) during the SE. [...]".

 

Source: Nature
Authors: Haiyang Wang et al.
DOI: https://doi.org/10.1038/s41467-023-39962-9

Read the full article here.


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.


Redox-sensitive elements of Ediacaran black shales in South China with implications for a widespread anoxic ocean

Abstract.

"The high enrichment of redox-sensitive elements (RSEs), Mo, U, V, and Cr, in Ediacaran shales was attributed to the Neoproterozoic Oxygenation Event (NOE). However, recent studies have shown that contemporaneous shales from NW Canada do not exhibit RSE enrichment, whereas those from South China exhibit varying degrees of RSE enrichment. Here we investigate RSE records in a broader spatial and temporal distribution of shales within the Ediacaran Doushantuo Formation from South China. [...]".

 

Source: Science Direct
Authors: Yufei Hao et al.
DOI: https://doi.org/10.1016/j.jseaes.2023.105670

Read the full article here.


Deoxygenation of the Baltic Sea during the last millennium

Abstract.

"Over the last 1,000 years, changing climate strongly influenced the ecosystem of coastal oceans such as the Baltic Sea. Sedimentary records revealed that changing temperatures could be linked to changing oxygen levels, spreading anoxic, oxygen-free areas in the Baltic Sea. However, the attribution of changing oxygen levels remains to be challenging. This work simulates a preindustrial period of 850 years, covering the Medieval Climate Anomaly (MCA) and the Little Ice Age using a coupled physical-biogeochemical model. [...]".

 

Source: Frontiers in Marine Science
Authors: Florian Börgel et al.
DOI: https://doi.org/10.3389/fmars.2023.1174039

Read the full article here.


Impacts and uncertainties of climate-induced changes in watershed inputs on estuarine hypoxia

Abstract.

"Multiple climate-driven stressors, including warming and increased nutrient delivery, are exacerbating hypoxia in coastal marine environments. Within coastal watersheds, environmental managers are particularly interested in climate impacts on terrestrial processes, which may undermine the efficacy of management actions designed to reduce eutrophication and consequent low-oxygen conditions in receiving coastal waters. However, substantial uncertainty accompanies the application of Earth system model (ESM) projections to a regional modeling framework when quantifying future changes to estuarine hypoxia due to climate change. [...]".

 

Source: Biogeosciences
Authors: Kyle E. Hinson et al.
DOI: https://doi.org/10.5194/bg-20-1937-2023

Read the full article here.


Natural hypoxic conditions do not affect the respiration rates of the cold-water coral Desmophyllum pertusum (Lophelia pertusa) ...

Full title: "Natural hypoxic conditions do not affect the respiration rates of the cold-water coral Desmophyllum pertusum (Lophelia pertusa) living in the Angola margin (Southeastern Atlantic Ocean)"

Abstract.

"Large, well-developed and flourishing reefs dominated by the cold-water coral Desmophyllum pertusum have recently been discovered along the Angola margin in the southeastern Atlantic Ocean living under very low oxygen concentrations (0.6–1.5 mL L−1). This study assessed the respiration rates of this coral in a short-term (10 days) aquarium experiment under naturally [...]".

 

Source: Science Direct
Authors: Andrea Gori et al.
DOI: https://doi.org/10.1016/j.dsr.2023.104052

Read the full article here.


Role of climate variability on deep-water dynamics and deoxygenation during sapropel deposition ...

Full title: "Role of climate variability on deep-water dynamics and deoxygenation during sapropel deposition: New insights from a palaeoceanographic empirical approach"

Abstract.

"Modern marine settings are experiencing rapid deoxygenation mainly forced by global warming and anthropogenic eutrophication. Therefore, studies that assess the role of climate variability in large spatiotemporal deoxygenations during past climate changes are needed to better comprehend the consequences of the current global warming and ocean deoxygenation. [...]".

 

Source: Science Direct
Authors: Ricardo D. Monedero-Contreras et al.
DOI: https://doi.org/10.1016/j.palaeo.2023.111601

Read the full article here.


Hypoxia and warming take sides with small marine protists: An integrated laboratory and field study

Abstract.

"Hypoxia and ocean warming are two mounting global environmental threats influencing marine ecosystems. However, the interactive effects of rising temperature and depleted dissolved oxygen (DO) on marine protists remains unknown. Here, we conducted a series of laboratory experiments on four protozoa with distinct cell sizes to investigate the combined effects of temperature (19, 22, 25, 28, and 31 °C) and oxygen availability (hypoxia, 2 mg DO L−1 and normoxia, 7 mg DO L−1) on their physiological performances (i.e., growth, ingestion, and respiration rates). The hypoxia-induced inhibition in three physiological rates increased with the biovolume of the protists. [...]".

 

Source: Science Direct
Authors: Cheng Qian et al.
DOI: https://doi.org/10.1016/j.scitotenv.2023.163568

Read the full article here.


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