News

A well-oxygenated eastern tropical Pacific during the warm Miocene

Abstract.

"The oxygen content of the oceans is susceptible to climate change and has declined in recent decades, with the largest effect in oxygen-deficient zones (ODZs), that is, mid-depth ocean regions with oxygen concentrations <5 μmol kg−1 (ref.). Earth-system-model simulations of climate warming predict that ODZs will expand until at least 2100. The response on timescales of hundreds to thousands of years, however, remains uncertain. Here we investigate changes in the response of ocean oxygenation during the warmer-than-present Miocene Climatic Optimum (MCO; 17.0–14.8 million years ago (Ma)). [...]".

 

Source: Nature
Authors: Anya V. Hess et al.
DOI: https://doi.org/10.1038/s41586-023-06104-6

Read the full article here.


A Selected Review of Impacts of Ocean Deoxygenation on Fish and Fisheries

Abstract.

"Oxygen is crucial for the survival of marine species. Yet, the ocean has experienced a loss of approximately 2% of its oxygen inventory since the last century, resulting in adverse impacts on marine life and ecosystems. In particular, changes in the gap between the supply and demand for dissolved oxygen lead to physiological and ecological variations, which cause alterations in habitats and food webs for fish and ecosystem services. These changes vary over time and by region, and the heterogeneous characteristics of marine species bring about non-linear consequences to human society. [...]".

 

Source: MDPI
Authors: Hongsik Kim et al.
DOI: https://doi.org/10.3390/fishes8060316

Read the full article here. 


Oxygen dynamics in marine productive ecosystems at ecologically relevant scales

Abstract.

"The decline of dissolved oxygen in the oceans could be detrimental to marine life and biogeochemical cycles. However, predicting future oxygen availability with models that mainly focus on temporal and spatial large-scale mean values could lead to incorrect predictions. Marine ecosystems are strongly influenced by short temporal- and small spatial-scale oxygen fluctuations. Large-scale modelling neglects fluctuations, which include the pervasive occurrence of high oxygen supersaturation on a daily time scale in productive ecosystems such as coral reefs, seagrass meadows and mangrove forests and the spatial heterogeneity in oxygen availability at microclimatic scales. [...]".

 

Source: Nature
Authors: Folco Giomi et al.
DOI: https://doi.org/10.1038/s41561-023-01217-z

Read the full article here.


Impact of deoxygenation and warming on global marine species in the 21st century

Abstract.

"Ocean temperature and dissolved oxygen shape marine habitats in an interplay with species' physiological characteristics. Therefore, the observed and projected warming and deoxygenation of the world's oceans in the 21st century may strongly affect species' habitats. Here, we implement an extended version of the Aerobic Growth Index (AGI), which quantifies whether a viable population of a species can be sustained in a particular location. We assess the impact of projected deoxygenation and warming on the contemporary habitat of 47 representative marine species covering the epipelagic, mesopelagic, and demersal realms. [...]".

 

Source: Biogeosciences
Authors: Anne L. Morée et al.
DOI: https://doi.org/10.5194/bg-20-2425-2023

Read the full article here.


GO2NE Webinar on Ocean Deoxygenation

GO2NE Webinar on Ocean Deoxygenation. 

"Do you want to know more about deoxygenation in the ocean?
Join us for the upcoming webinar!

Wednesday, 26th July 2023, 13:00 h – 14:00 CEST

Registration link

Please join the Global Ocean Oxygen Network (IOC Expert Working Group GO2NE) for a new session of its webinar series on ocean deoxygenation. The 21st webinar will take place 26 July 2023, 13:00 h CEST. The webinar will feature presentations by a more senior and an early-career scientist, 20 minutes each followed by 10 minutes moderated discussion sessions. 

If you are interested to present at one of the upcoming webinars please submit a short abstract here.

Moderation
Damodar Shenoy
CSIR-National Institute of Oceanography, Goa, India

Speakers:
Sudheesh Valliyodan
Central University of Kerala, India
"Oxygen Minimum Zone dynamics of eastern Arabian Sea"

Zouhair Lachkar
New York University Abu Dhabi, United Arab Emirates
"Recent and future trends in the Arabian Sea oxygen minimum zone: processes and uncertainties" 

If you want to receive further information about upcoming webinars please register here." 


../common/calendar Start Date: 7/26/23

Can Oxygen Utilization Rate Be Used to Track the Long-Term Changes of Aerobic Respiration in the Mesopelagic Atlantic Ocean?

Abstract.

"Quantifying changes in oceanic aerobic respiration is essential for understanding marine deoxygenation. Here we use an Earth system model to investigate if and to what extent oxygen utilization rate (OUR) can be used to track the temporal change of true respiration (Rtrue). Rtrue results from the degradation of particulate and dissolved organic matter in the model ocean, acting as ground truth to evaluate the accuracy of OUR. Results show that in thermocline and intermediate waters of the North Atlantic Subtropical Gyre (200–1,000 m), vertically integrated OUR and Rtrue both decrease by 0.2 molO2/m2/yr from 1850 to 2100 under global warming. [...]".

 

Source: Wiley Online Library
Authors: Haichao Guo et al.
DOI: https://doi.org/10.1029/2022GL102645

Read the full article here.


Mercury isotope evidence for recurrent photic-zone euxinia triggered by enhanced terrestrial nutrient inputs during the Late Devonian mass extinction

Abstract.

"Widespread oceanic anoxia marked by globally extensive deposition of organic-rich black shale during the Late Devonian was a major factor in the mass extinctions at the Frasnian-Famennian (FFB, ∼372 million years ago) and Devonian-Carboniferous boundaries (DCB, ∼359 million years ago), although the triggers for these deoxygenation events are still under debate. Here, we apply a novel paleoredox proxy, Hg isotopes, to investigate Late Devonian ocean redox variation and its causes. [...]".

 

Source: Science Direct
Authors: Wang Zheng et al.
DOI: https://doi.org/10.1016/j.epsl.2023.118175

Read the full article here.


Oceanic anoxic events, photic-zone euxinia, and controversy of sea-level fluctuations during the Middle-Late Devonian

Abstract.

"This paper reviews global records of anoxic events of the Middle Devonian – earliest Mississippian, as well as the possible triggers and controls of these events. These “anoxic events” are complex multistage paleoenvironmental disturbances manifested in multiple proxies, which we showcase with the Horn River Group (HRG) – a succession of basinal organic-rich shales and cherts deposited during the latest Eifelian – earliest Late Frasnian(∼386–373 My ago) on the western continental margin of Laurentia near the paleo-equator. [...]".

 

Source: Science Direct
Authors: Pavel Kabanov et al.
DOI: https://doi.org/10.1016/j.earscirev.2023.104415

Read the full article here.


Spatial and Temporal Redox Heterogeneity Controlled by a Fe(II), Anoxic Upwelling System in the Early Mesoproterozoic Ocean

Abstract. 

"The availability of oxygen and nutrients during the Mesoproterozoic (1.6–1.0 Ga) is thought to influence the rate of eukaryote evolution. The cause of the transition from low productivity in the upper Wumishan Formation to organic-rich sediments in the Hongshuizhuang Formation remains unknown. We report FeHR/FeT, Fepy/FeHR, MoEF, UEF, VEF, and [Ce/Ce*]SN in one core of the Yanliao Basin to study the redox evolution and compare it with other sections in different depths of the Yanliao Basin to get clues of the spatial and temporal redox heterogeneity. [...]".

 

Source: Wiley Online Library
Authors: Mingze Ye et al.
DOI: https://doi.org/10.1029/2023GL103598

Read the full article here.


Phosphorus controls on the formation of vivianite versus green rust under anoxic conditions

Abstract.

"The formation of green rust (GR; a mixed ferric/ferrous hydroxide) and vivianite (ferrous phosphate) are likely to have exerted a major control on phosphorus (P) cycling in ancient anoxic oceans. However, the factors that influence the formation of these minerals under different chemical conditions are poorly constrained, which limits understanding of the pathways that ultimately result in P drawdown and retention in anoxic sediments. This, in turn, limits understanding of P cycling in anoxic oceans and hence potential productivity feedbacks. [...]".

 

Source: Science Direct
Authors: Yijun Xiong et al.
DOI: https://doi.org/10.1016/j.gca.2023.04.032

Read the full article here.


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