News

The vulnerability of sharks, skates, and rays to ocean deoxygenation: Physiological mechanisms, behavioral responses, and ecological impacts

Abstract.

"Levels of dissolved oxygen in open ocean and coastal waters are decreasing (ocean deoxygenation), with poorly understood effects on marine megafauna. All of the more than 1000 species of elasmobranchs (sharks, skates, and rays) are obligate water breathers, with a variety of life-history strategies and oxygen requirements. This review demonstrates that although many elasmobranchs typically avoid hypoxic water, they also appear capable of withstanding mild to moderate hypoxia with changes in activity, ventilatory responses, alterations to circulatory and hematological parameters, and morphological alterations to gill structures. [...]".

 

Source: Wiley Online Library
Authors: Matt J. Waller et al.
DOI: https://doi.org/10.1111/jfb.15830

Read the full article here.


Retrieval of subsurface dissolved oxygen from surface oceanic parameters based on machine learning

Abstract.

"Oceanic dissolved oxygen (DO) is crucial for oceanic material cycles and marine biological activities. However, obtaining subsurface DO values directly from satellite observations is limited due to the restricted observed depth. Therefore, it is essential to develop a connection between surface oceanic parameters and subsurface DO values. Machine learning (ML) methods can effectively grasp the complex relationship between input attributes and target variables, making them a valuable approach for estimating subsurface DO values based on surface oceanic parameters. [...]".

 

Source: Science Direct
Authors: Bo Ping et al.
DOI: https://doi.org/10.1016/j.marenvres.2024.106578

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Diversity and endemism of hard-shelled benthic foraminifera in permanently oxygen-depleted bottom waters: An analysis from the eastern Pacific

Abstract.

"Benthic foraminifera are single-celled organisms inhabiting all marine environments. Despite their high tolerance to oxygen depletion, the prevailing hypothesis anticipates a reduction in their diversity in permanently oxygen-depleted environments, including oxygen minimum zones. Here we re-evaluate diversity and study the endemism of benthic foraminifera in the eastern Pacific, an oceanic area hosting the largest permanently oxygen-depleted waters of the world. [...]".

 

Source: Science Direct
Authors: Paula Diz et al.
DOI: https://doi.org/10.1016/j.pocean.2024.103277

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Prokaryotic community assembly patterns and nitrogen metabolic potential in oxygen minimum zone of Yangtze Estuary water column

Abstract.

"It is predicted that oxygen minimum zones (OMZs) in the ocean will expand as a consequence of global warming and environmental pollution. This will affect the overall microbial ecology and microbial nitrogen cycle. As one of the world's largest alluvial estuaries, the Yangtze Estuary has exhibited a seasonal OMZ since the 1980s. In this study, we have uncovered the microbial composition, the patterns of community assembly and the potential for microbial nitrogen cycling within the water column of the Yangtze Estuary, with a particular focus on OMZ. [...]".

 

Source: Science Direct
Authors: Yihua Sun et al.
DOI: https://doi.org/10.1016/j.envres.2024.119011

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Regional Fluctuations in the Eastern Tropical North Pacific Oxygen Minimum Zone during the Late Holocene

Abstract.

"This study presents a high-resolution record of δ15Nsed, which serves as a proxy for water column denitrification and oxygen minimum zone (OMZ) intensity, from the Soledad Basin in the Eastern Tropical North Pacific OMZ. The Soledad Basin δ15Nsed record is compared to the Pescadero Slope and Santa Barbara Basin (SBB) δ15Nsed records to gain insight into regional variations in the ETNP OMZ. During the Medieval Climate Anomaly (MCA; 950–1250 CE), Soledad Basin, Pescadero Slope, and SBB records exhibit coherent trends suggesting that there was general water column oxygenation stability. [...]".

 

Source: MDPI
Authors: Caitlin E. Tems & Eric Tappa
DOI: https://doi.org/10.3390/oceans5020021

Read the full article here.


Prokaryotic community structure and key taxa in the Arabian Sea’s oxygen minimum zone

Abstract.

"Microbial communities within oxygen minimum zones (OMZs) play crucial roles in the marine biogeochemical cycling. Arabian Sea (AS) has one of the largest OMZs among the global oceans, however, knowledge about the microbial ecology of the AS OMZ remained limited. In the present study, 44 water samples collected from six stations across the AS, spanning from the deep chlorophyll maximum (DCM) layer to 4000m depth were analyzed. High-throughput sequencing of 16S rRNA genes revealed the structural diversity of bacterial and archaeal communities, influenced primarily by depth and dissolved oxygen (DO) levels. [...]".

 

Source: Frontiers in Marine Science
Authors: Ding Li et al.
DOI: https://doi.org/10.3389/fmars.2024.1380819

Read the full article here.


Ocean deoxygenation dampens resistance of diatoms to ocean acidification in darkness

Abstract.

"Respiratory activity in the oceans is declining due to the expansion of hypoxic zones and progressive deoxygenation, posing threats to marine organisms along with impacts of concurrent ocean acidification. Therefore, understanding the combined impacts of reduced pO2 and elevated pCO2 on marine primary producers is of considerable significance. Here, to simulate diatoms’ sinking into the aphotic zone of turbid coastal water, we exposed the diatoms Thalassiosira pseudonana and Thalassiosira weissflogii in darkness at 20°C [...]".

 

Source: Frontiers in Marine Science
Authors: Jia-Zhen Sun et al.
DOI: https://doi.org/10.3389/fmars.2024.1387552

Read the full article here.


Effects of water flow and ocean acidification on oxygen and pH gradients in coral boundary layer

Abstract.

"Reef-building corals live in highly hydrodynamic environments, where water flow largely controls the complex chemical microenvironments surrounding them—the concentration boundary layer (CBL). The CBL may be key to alleviate ocean acidification (OA) effects on coral colonies by partially isolating them. However, OA effects on coral CBL remain poorly understood, particularly under different flow velocities. Here, we investigated these effects on the reef-building corals Acropora cythereaPocillopora verrucosa, and Porites cylindrica. [...]".

 

Source: Nature
Authors: Catarina P. P. Martins et al.
DOI: https://doi.org/10.1038/s41598-024-63210-9

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Editorial: Drivers and consequences of ocean deoxygenation in tropical ecosystems

Abstract.

"Coastal habitats are under increasing anthropogenic pressures that jeopardize the survival and persistence of ecologically important marine life. One such stressor, increasingly recognized as a significant threat to marine coastal habitats, is deoxygenation (Breitburg et al., 2018; IPCC, 2023). The United Nations Decade of Ocean Science for Sustainable Development has identified deoxygenation as a top international priority for ocean research, with efforts being led by the Global Ocean Oxygen Network (GO2NE) and affiliated programs (Global Ocean Oxygen Decade program). [...]".

 

Source: Frontiers in Marine Science
Authors: Maggie D. Johnson et al.
DOI: https://doi.org/10.3389/fmars.2024.1425902

Read the full article here.


Effect of nutrient reductions on dissolved oxygen and pH: a case study of Narragansett bay

Abstract.

"To assess the consequences of nutrient reduction strategies on water quality under climate change, we investigated the long-term dynamics of dissolved oxygen (DO) and pH in Narragansett Bay (NB), a warming urbanized estuary in Rhode Island, where nitrogen loads have declined due to extensive wastewater treatment plant upgrades. We use 15 years (January 2005-December 2019) of measurements from the Narragansett Bay Fixed Site Monitoring network. Nutrient-enhanced phytoplankton growth can increase DO in the upper water column while subsequent respiration can reduce water column DO and enhance bottom water acidification, and vice-versa. [...]".

 

Source: Frontiers in Marine Science
Authors: Hongjie Wang et al.
DOI: https://doi.org/10.3389/fmars.2024.1374873

Read the full article here.


Emergent constraint on oxygenation of the upper South Eastern Pacific oxygen minimum zone in the twenty-first century

Abstract.

"As a consequence of on-going global warming, the ocean is losing oxygen, which has implications not only in terms of marine resources management and food supply but also in terms of the potentially important feedback on the global carbon cycle and climate. Of particular scrutiny are the extended zones of already low levels of oxygen called the oxygen minimum zones (OMZs) embedded in the subsurface waters of the productive Eastern Boundary Upwelling Systems (EBUS). These OMZs are currently diversely simulated by state-of-the-art Earth System Models (ESM) hampering a reliable projection of ocean deoxygenation on marine ecosystem services in these regions. [...]".

 

Source: Nature 
Authors: Ivan Almendra et al.
DOI: https://doi.org/10.1038/s43247-024-01427-2

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Oxygen declination in the coastal ocean over the twenty-first century: Driving forces, trends, and impacts

Abstract.

"Oxygen declination in coastal oceans has accelerated drastically in recent decades, both in terms of severity and spatial extent, and such disappearance of oxygen leads to dead zones where life can't survive. This phenomenon is mainly attributed to nutrient pollution and climate change due to intensified anthropogenic activities. The annual statistical oxygen mean concentrations showed the current deoxygenation trends based on (WOA_2001–2018) data comparison of 200 m below the surface water from the first two decades of the 21st century. [...]".

 

Source: Science Direct
Authors: Md Mesbah Uddin Bhuiyan et al.
DOI: https://doi.org/10.1016/j.cscee.2024.100621

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Disparity between Toarcian Oceanic Anoxic Event and Toarcian carbon isotope excursion

Abstract.

"The Toarcian Oceanic Anoxic Event (T-OAE, Early Jurassic) is marked by widespread marine deoxygenation and deposition of organic carbon (OC)-rich strata. The genesis of the T-OAE is thought to be associated with environmental changes caused by the emission of 12C-enriched greenhouse gasses (CO2, CH4), manifested in a negative Toarcian carbon isotope excursion (nT-CIE). The nT-CIE is commonly used to stratigraphically define the T-OAE, and despite the complex interrelationship of the different environmental phenomena, both terms (nT-CIE and T-OAE) are commonly used interchangeable. [...]".

 

Source: Springer Nature
Authors: Wolfgang Ruebsam & Lorenz Schwark 
DOI: https://doi.org/10.1007/s00531-024-02408-8

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Re-Evaluating Hydrogen Sulfide as a Sink for Cadmium and Zinc in the Oxic to Suboxic Upper Water Column of the Pacific Ocean

Abstract.

"Hydrogen sulfide is produced by heterotrophic bacteria in anoxic waters and via carbonyl sulfide hydrolysis and phytoplankton emissions under oxic conditions. Apparent losses of dissolved cadmium (dCd) and zinc (dZn) in oxygen minimum zones (OMZs) of the Atlantic and Pacific Oceans have been attributed to metal-sulfide precipitation formed via dissimilatory sulfate reduction. It has also been argued that such a removal process could be a globally important sink for dCd and dZn. However, our studies from the North Pacific OMZ show that dissolved and particulate sulfide concentrations are insufficient to support the removal of dCd via precipitation. [...]".

 

Source: Wiley Online Library
Authors: Nicole Buckley et al.
DOI: https://doi.org/10.1029/2023GB007881

Read the full article here.


Regional differences in sediment oxygen uptake rates in polymetallic nodule and co-rich polymetallic crust mining areas of the Pacific Ocean

Abstract.

"The potential impact of manganese mining on benthic remineralization in the Pacific Ocean was assessed in this study. We estimated total sediment oxygen uptake rates (TOU) using in situ autonomous benthic chambers at the polymetallic nodule and Co-rich polymetallic crust mining sites of Korea: at the Clarion-Clipperton Fracture Zone (PILOT site) in the eastern Pacific and the open-sea seamounts (OSM) 9-1 and OSM17 in the western Pacific, respectively. [...]".

 

Source: Science Direct
Authors: Sung-Uk An et al.
DOI: https://doi.org/10.1016/j.dsr.2024.104295

Read the full article here.


Shifts in magnetic mineral assemblages support ocean deoxygenation before the end-Permian mass extinction

Abstract.

"Expansion of oceanic anoxia is a prevailing hypothesis for driving the marine end-Permian mass extinction and is mainly based on isotopic geochemical proxies. However, long-term oceanic redox conditions before the end-Permian mass extinction remain unresolved. Here we report a secular redox trend based on rock magnetic experiments and cerium anomalies through the Changhsingian and across the Permian-Triassic boundary at the Meishan section, China. Magnetic mineral assemblages changed dramatically at ca. 252.8 million years age (Ma), which indicates that oceanic deoxygenation started about 0.9 million years earlier than the end-Permian mass extinction. [...]".

 

Source: Nature
Authors: Min Zhang et al.
DOI: https://doi.org/10.1038/s43247-024-01394-8

Read the full article here.


Expanding oxygen minimum zones in the northern Indian Ocean predicted by hypoxia-related bacteria

Abstract.

"Oxygen minimum zones (OMZs) in the ocean are areas with dissolved oxygen (DO) concentrations below critical thresholds that impact marine ecosystems and biogeochemical cycling. In the northern Indian Ocean (NIO), OMZs exhibit a tendency to expand in mesopelagic waters and contribute significantly to global nitrogen loss and climate change. However, the microbial drivers of OMZ expansion in the NIO remain understudied. [...]".

 

Source: Frontiers in Marine Science
Authors: Jinyan Liu et al.
DOI: https://doi.org/10.3389/fmars.2024.1396306

Read the full article here.


Simulated Abrupt Shifts in Aerobic Habitats of Marine Species in the Past, Present, and Future

Abstract.

"The physiological tolerances of marine species toward ambient temperature and oxygen can jointly be evaluated in a single metric: the metabolic index. Changes therein characterize a changing aerobic habitat tailored to species-specific thermal and hypoxia sensitivity traits. If the geographical limits of marine species as indicated by critical thresholds of the metabolic index shift abruptly in response to ocean warming and deoxygenation, aerobic habitat could potentially be lost abruptly. [...]".

 

Source: Wiley Online Library
Authors: Friederike Fröb et al.
DOI: https://doi.org/10.1029/2023EF004141

Read the full article here.


Adjusting metabolic rates and critical oxygen tension in planktonic copepods under increasing hypoxia in highly productive coastal upwelling zones

Abstract.

"Ongoing ocean deoxygenation is threatening marine organisms globally. In eastern boundary upwelling systems, planktonic copepods dominate the epipelagic zooplankton, being crucial in the marine food web. Yet, they must cope with severe hypoxia caused by shoaling of the oxygen minimum zone. Based on laboratory experiments during 2021, we found differential responses in the metabolic rate (MR) and critical oxygen partial pressure of three abundant copepods. Calanoides patagoniensis doubled its MR during the upwelling season, so better exploiting the spring phytoplankton bloom for feeding and reproduction while maintaining their critical oxygen partial pressure unchanged between seasons. [...]".

 

Source: Wiley Online Library
Authors: Leissing Frederick et al.
DOI: https://doi.org/10.1002/lno.12556

Read the full article here.


The global energy transition offers new options for mitigation of coastal hypoxia: Do we know enough?

Abstract.

"The mitigation of climate change and pollution-related hypoxia and anoxia is a growing challenge for coastal communities. Known ocean conservation measures do not show the desired fast results counteracting deoxygenation. The new infrastructure related to the coastal production of renewable energies linked to the production of green hydrogen can provide new possibilities of artificial ocean reoxygenation to mitigate coastal hypoxia, but has to be treated urgently and seriously from different scientific, engineering and socio-economic angles. [...]".

 

Source: Wiley Online Library
Authors: Patricia Handmann & Douglas Wallace
DOI: https://doi.org/10.1111/gcb.17228

Read the full article here.


Intra-colony spatial variance of oxyregulation and hypoxic thresholds for key Acropora coral species

Abstract.

"Oxygen (O2) availability is essential for healthy coral reef functioning, yet how continued loss of dissolved O2 via ocean deoxygenation impacts performance of reef building corals remains unclear. Here, we examine how intra-colony spatial geometry of important Great Barrier Reef (GBR) coral species Acropora may influence variation in hypoxic thresholds for upregulation, to better understand capacity to tolerate future reductions in O2 availability. We first evaluate the application of more streamlined models used to parameterise Hypoxia Response Curve data, models that have been used historically to identify variable oxyregulatory capacity. [...]".

 

Source: Wiley Online Library
Authors: Nicole J. Dilernia et al.
DOI: https://doi.org/10.1002/ece3.11100

Read the full article here.


The Ocean's Meridional Oxygen Transport

Abstract.

"Quantification of oxygen uptake at the ocean surface and its surface-to-interior pathways is crucial for understanding oxygen concentration change in a warming ocean. We investigate the mean meridional global oxygen transport between 1950 and 2009 using coupled physical-biogeochemical model output. We introduce a streamfunction in latitude-oxygen coordinates to reduce complexity in the description of the mean meridional oxygen pathways. [...]".

 

Source: Wiley Online Library
Authors: Esther Portela et al.
DOI: https://doi.org/10.1029/2023JC020259

Read the full article here.


New approaches to combat eutrophication and hypoxia

"The satellite event 'New approaches to combat eutrophication and hypoxia' brought together partners under the GEF-8 Clean and Healthy Ocean Integrated Program (CHO-IP) for introductions and to begin the next phase of tackling eutrophication and hypoxia in 14 national child projects.

Representatives of partner organisations, the Food and Agriculture Organization of the United Nations (FAO), Asian Development Bank (ADB), Development Bank for Latin America (CAF), European Bank for Reconstruction and Development (EBRD), together with the  IOC-UNESCO Global Ocean Oxygen Network (GO2NE) and the Global Water Partnership (GWP) discussed the program aims and objectives over the course of a 90 minute deoxygenation primer, panel discussion and Q&A session.

Keys points expressed by participants included that:

  • Partners across scales and sectors must be involved early, with appropriate financing mechanisms, and engaged throughout to foster project ownership and outcome longevity.
  • Scientific data, and methods of access, must be shared openly.
  • Science will be unheeded unless it is delivered in a manner that is clear, timely, intelligible, and contextualised and translated to those who have, or will have, the capacity to use it.
  • Collaboration with regional actors must be enhanced to aid identification of the most effective science-based actions that will have the highest impact in regional contexts, rather than following global trends.
  • International institutions must be encouraged to identify and engage with initiatives of actors in their networks that may already be addressing or adapting to hypoxic conditions.
  • Scientifically well-versed personnel are needed in Development Banks and other institutions positioned to leverage existing networks to tackle deoxygenation and other marine issues.

Partners will now move ahead with the program's Global Coordination Project and begin to make connections to national actors and networks working to address eutrophication and hypoxia and implement the program in the 14 participating countries.

The program will synergise with the Global Ocean Oxygen Database and Atlas (GO2DAT), an endorsed action under the UN Ocean Decade of Ocean Science for Sustainable Development and may lead to the development of new Actions as the program is implemented."

 

Contact: go2ne-secretariat@unesco.org

More information:

The 'New approaches to combat eutrophication and hypoxia' event

The GEF Clean and Healthy Ocean Program

IOC-UNESCO program announcement


Eddy-Mediated Turbulent Mixing of Oxygen in the Equatorial Pacific

Abstract.

"In the tropical Pacific, weak ventilation and intense microbial respiration at depth give rise to a low dissolved oxygen (O2) environment that is thought to be ventilated primarily by the equatorial current system (ECS). The role of mesoscale eddies and vertical mixing as potential pathways of O2 supply in this region, however, remains poorly known due to sparse observations and coarse model resolution. Using an eddy resolving simulation of ocean circulation and biogeochemistry, we assess the contribution of these processes to the O2 budget balance and find that vertical mixing of O2 [...]".

 

Source: Wiley Online Library
Authors: Yassir A. Eddebbar et al.
DOI: https://doi.org/10.1029/2023JC020588

Read the full article here.


Copepoda community imprints the continuity of the oceanic and shelf oxygen minimum zones along the west coast of India

Abstract.

"The largest continental shelf Oxygen Minimum Zone (OMZ) in the world is formed along the Indian western shelf in the eastern Arabian Sea during the Southwest Monsoon [(SWM); June–September], which is a natural pollution event associated with the coastal upwelling. This study examines the composition, abundance, and distribution of copepods during the Northeast Monsoon [(NEM); November to February] and SWM in 50 m depth zones along the Indian western shelf in the eastern Arabian Sea. [...]".

 

Source: Science Direct
Authors: Vidhya Vijayasenan et al.
DOI: https://doi.org/10.1016/j.marenvres.2024.106380

Read the full article here.


Decreasing available O2 interacts with light to alter the growth and fatty acid content in a marine diatom

Abstract.

"Hypoxic zones and oceanic deoxygenation are spreading worldwide due to anthropogenic activities and climate change, greatly affecting marine organisms exposed to lowered O2. Yet, the effects of the lowered O2 on phytoplankton are often neglected when studying O2 effects as they are the O2 producers. Here we showed that low O2 (dissolved O2, 150 ± 10 μmol L−1) enhanced the growth of the marine diatom Thalassiosira pseudonana in limited light but reduced it in moderate to inhibitory light and that hypoxia (40 ± 7.5 μmol L−1) reduced its growth at any growth lights. [...]".

 

Source: Science Direct
Authors: Bokun Chen et al.
DOI: https://doi.org/10.1016/j.envexpbot.2024.105667

Read the full article here.


Critical swimming speed of juvenile rockfishes (Sebastes) following long- and short-term exposures to acidification and deoxygenation

Abstract.

"Reef fishes in the California Current Ecosystem have evolved in habitats affected by seasonally variable, episodic upwelling of high pCO2 (acidified, low pH) and low dissolved oxygen (deoxygenated) water, which suggests that these fishes might exhibit resilience to ocean acidification (OA) and deoxygenation. Yet, how the fitness of these fish are affected by natural variability in pH and DO over short time scales remains poorly understood, as do the effects of longer-term trends in pH and DO driven by climate change. [...]".

 

Source: Science Direct
Authors: Corianna Flannery & Eric P. Bjorkstedt
DOI: https://doi.org/10.1016/j.jembe.2024.151993

Read the full article here.


Whole transcriptome analysis of demersal fish eggs reveals complex responses to ocean deoxygenation and acidification

Abstract.

"Ocean acidification and deoxygenation co-occur in marine environments, causing deterioration of marine ecosystems. However, effects of compound stresses on marine organisms and their physiological coping mechanisms are largely unknown. Here, we show how high pCO2 and low dissolved oxygen (DO) cause transcriptomic changes in eggs of a demersal fish (Sillago japonica), which are fully exposed to such stresses in natural environment. Overall gene expression was affected more strongly by low DO than by high pCO2. Enrichment analysis detected significant stress responses such as glycolytic processes in response to low DO. [...]".

 

Source: Science Direct
Authors: Akira Iguchi et al.
DOI: https://doi.org/10.1016/j.scitotenv.2023.169484

Read the full article here.


Marine anoxia initiates giant sulfur-oxidizing bacterial mat proliferation and associated changes in benthic nitrogen, sulfur, and iron cycling...

Full title: "Marine anoxia initiates giant sulfur-oxidizing bacterial mat proliferation and associated changes in benthic nitrogen, sulfur, and iron cycling in the Santa Barbara Basin, California Borderland"

Abstract.

"The Santa Barbara Basin naturally experiences transient deoxygenation due to its unique geological setting in the southern California Borderland and seasonal changes in ocean currents. Long-term measurements of the basin showed that anoxic events and subsequent nitrate exhaustion in the bottom waters have been occurring more frequently [...]".

 

Source: Biogeosciences
Authors: David J. Yousavich et al.
DOI: https://doi.org/10.5194/bg-21-789-2024

Read the full article here.


Enhanced ocean deoxygenation in the Bering Sea during MIS 11c

Abstract.

"Accelerated Arctic warming has raised concerns about future environmental conditions in the Bering Sea, one of the world's most productive marine ecosystems. Marine Isotope Stage (MIS) 11 (424–374 ka), a period with orbital parameters similar to those of the current interglacial (Holocene), is thought to be a suitable analog to predict future marine environments. Here, we reconstruct paleoredox changes in the Bering Sea over the last 800 kyr using high-resolution U/Th ratios from four sites, which were sampled by the Integrated Ocean Drilling Program (IODP) Expedition 323. [...]".

 

Source: Science Direct
Authors: Xuguang Feng et al.
DOI: https://doi.org/10.1016/j.palaeo.2023.111982

Read the full article here.


Climate, Oxygen, and the Future of Marine Biodiversity

Abstract.

"The ocean enabled the diversification of life on Earth by adding O2 to the atmosphere, yet marine species remain most subject to O2 limitation. Human industrialization is intensifying the aerobic challenges to marine ecosystems by depleting the ocean's O2 inventory through the global addition of heat and local addition of nutrients. Historical observations reveal an ∼2% decline in upper-ocean O2 and accelerating reports of coastal mass mortality events. The dynamic balance of O2 supply and demand provides a unifying framework for understanding these phenomena across scales from the global ocean to individual organisms. [...]".

 

Source: Annual Review of Marine Science
Authors: Curtis Deutsch et al.
DOI: https://doi.org/10.1146/annurev-marine-040323-095231

Read the full article here.


Global oceanic oxygenation controlled by the Southern Ocean through the last deglaciation

Abstract.

"Ocean dissolved oxygen (DO) can provide insights on how the marine carbon cycle affects global climate change. However, the net global DO change and the controlling mechanisms remain uncertain through the last deglaciation. Here, we present a globally integrated DO reconstruction using thallium isotopes, corroborating lower global DO during the Last Glacial Maximum [19 to 23 thousand years before the present (ka B.P.)] relative to the Holocene. [...]".

 

Source: Science Advances  
Authors: Yi Wang et al.
DOI: 10.1126/sciadv.adk2506

Read the full article here.


Highly active fish in low oxygen environments: vertical movements and behavioural responses of bigeye and yellowfin tunas to oxygen minimum zones...

Full title: "Highly active fish in low oxygen environments: vertical movements and behavioural responses of bigeye and yellowfin tunas to oxygen minimum zones in the eastern Pacific Ocean"

Abstract.

"Oxygen minimum zones in the open ocean are predicted to significantly increase in volume over the coming decades as a result of anthropogenic climatic warming. The resulting reduction in dissolved oxygen (DO) in the pelagic realm is likely to have detrimental impacts on water-breathing organisms, particularly those with higher metabolic rates, such as billfish, tunas, and sharks. [...]".

 

Source: Springer Nature 
Authors: Nicolas E. Humphries et al.
DOI: https://doi.org/10.1007/s00227-023-04366-2

Read the full article here.


Divergent responses of the coral holobiont to deoxygenation and prior environmental stress

Abstract.

"Ocean deoxygenation is intensifying globally due to human activities – and is emerging as a grave threat to coral reef ecosystems where it can cause coral bleaching and mass mortality. However, deoxygenation is one of many threats to coral reefs, making it essential to understand how prior environmental stress may influence responses to deoxygenation. To address this question, we examined responses of the coral holobiont (i.e., the coral host, Symbiodiniaceae, and the microbiome) to deoxygenation in corals with different environmental stress backgrounds. [...]".

 

Source: Frontiers in Marine Science
Authors: Sara D. Swaminathan et al.
DOI: https://doi.org/10.3389/fmars.2023.1301474

Read the full article here.


Redox geochemical signatures in Mediterranean sapropels: Implications to constrain deoxygenation dynamics in deep-marine settings

Abstract.

"Global warming and anthropogenic activity are boosting marine deoxygenation in many regions around the globe. Deoxygenation is a critical ocean stressor with profound implications for marine ecosystems and biogeochemical cycles. Understanding the dynamics and evolution of past deoxygenation events can enhance our knowledge of present-day and future impacts of climate change and anthropogenic pressure on marine environments. Many studies have reconstructed the evolution redox conditions of past deoxygenation events using geochemical proxies. [...]".

 

Source: Science Direct
Authors: Ricardo D. Monedero-Contreras et al.
DOI: https://doi.org/10.1016/j.palaeo.2023.111953

Read the full article here.


The past to unravel the future: Deoxygenation events in the geological archive and the anthropocene oxygen crisis

Abstract.

"Despite the observation that we are witnessing a true oxygen crisis, the ocean deoxygenation theme is getting less attention from the media and population compared to other environmental stressors concerning climate change. The current ocean oxygen crisis is characterized by a complex interplay of climatic, biological, and oceanographic processes acting at different time scales. Earth system models offer insights into future deoxygenation events and their potential extent [...]".

 

Source: Science Direct
Authors: Alan Maria Mancini et al.
DOI: https://doi.org/10.1016/j.earscirev.2023.104664

Read the full article here.


The early Toarcian Oceanic Anoxic Event (Jenkyns Event) in the Alpine-Mediterranean Tethys, north African margin...

Full title: "The early Toarcian Oceanic Anoxic Event (Jenkyns Event) in the Alpine-Mediterranean Tethys, north African margin, and north European epicontinental seaway"

Abstract.

"The early Toarcian Oceanic Anoxic Event (Jenkyns Event) was associated with major world-wide climatic changes with profound effects on the global carbon cycle. This review revisits the available literature covering the Jenkyns Event applying an updated common stratigraphic definition, allowing illustration of the development and evolution of anoxia in the Alpine-Mediterranean Tethys [...]".

 

Source: Science Direct 
Authors: Gabriele Gambacorta et al.
DOI: https://doi.org/10.1016/j.earscirev.2023.104636

Read the full article here.


Interactive effects of ocean deoxygenation and acidification on a coastal fish Sillago japonica in early life stages

Abstract.

"Acidification and deoxygenation are major threats to ocean environments. Despite the possibilities of their co-occurrence, little is known about their interactive effects on marine organisms. The effects of low pH and low dissolved oxygen (DO) on the early life stages of the coastal fish Sillago japonica were investigated. Twenty-five experimental treatments fully crossed in five levels of pH 7.6–8.1 and DO 50–230 μmol/kg (20–100 % saturation degree) were tested, and hatching rate of the embryos and survivability of the larvae after 24 h at 25 °C were investigated. [...]".

 

Source: Science Direct 
Authors: Makiko Yorifuji et al.
DOI: https://doi.org/10.1016/j.marpolbul.2023.115896

Read the full article here.


A Reconstructing Model Based on Time–Space–Depth Partitioning for Global Ocean Dissolved Oxygen Concentration

Abstract.

"Dissolved oxygen (DO) is essential for assessing and monitoring the health of marine ecosystems. The phenomenon of ocean deoxygenation is widely recognized. Nevertheless, the limited availability of observations poses a challenge in achieving a comprehensive understanding of global ocean DO dynamics and trends. The study addresses the challenge of unevenly distributed Argo DO data by developing time–space–depth machine learning (TSD-ML), a novel machine learning-based model designed to enhance reconstruction accuracy in data-sparse regions. [...]".

 

Source: MDPI
Authors: Zhenguo Wang et al.
DOI: https://doi.org/10.3390/rs16020228

Read the full article here.


Job Offer in Geomicrobiology/ Environmental Microbiology

PhD position at the Ludwig-Maximilians-Universität München

"The Department of Earth and Environmental Sciences at LMU Munich invites applications for one PhD position in Geomicrobiology/ Environmental Microbiology to experimentally investigate the diversity and activity of marine microbial communities in the context of ocean deoxygenation.

Together with warming and acidification, ocean deoxygenation is considered one of the three major impacts of climate change in global oceans according to IPCC, and a main research scientific topic for organizations such as UNESCO or IUCN. In the DFG Emmy-Noether Research Group in Biogeochemistry and Climate Change, we investigate the effects of ocean deoxygenation on dissolved organic matter (DOM) sequestration, due to interactions with microbial communities and the marine carbon and sulfur cycles. By combining field work experiments with state-of-art laboratory techniques from different disciplines, we aim to decipher new links between microbes and DOM, in the context of a changing, deoxygenated ocean."

You can find more details here


GOOD News Issue 4

The 4th Issue of GOOD News is now available here

Previous issues are available in the archive here.


High-frequency dynamics of pH, dissolved oxygen, and temperature in the coastal ecosystems of the Tanga-Pemba Seascape...

Full title: "High-frequency dynamics of pH, dissolved oxygen, and temperature in the coastal ecosystems of the Tanga-Pemba Seascape: implications for upwelling-enhanced ocean acidification and deoxygenation"

Abstract.

"Ocean acidification, deoxygenation, and warming are three interconnected global change challenges caused by increased anthropogenic carbon emissions. These issues present substantial threats to marine organisms, ecosystems, and the survival of coastal communities depending on these ecosystems. Coastal upwelling areas may experience significant [...]".

 

Source: Frontiers in Marine Science
Authors: Rushingisha George et al. 
DOI: https://doi.org/10.3389/fmars.2023.1286870

Read the full article here.


Editorial: Constraining uncertainties in hindcasts and future projections of marine deoxygenation

Abstract.

"Ocean deoxygenation is a key stressor for marine ecosystems and biogeochemical cycles (Gruber, 2011; Breitburg et al., 2018). Climate projections based on Earth system models (ESMs) suggest that the global oxygen inventory will undergo a significant decline over the next century under persistent greenhouse gas emissions (Bopp et al., 2013; Kwiatkowski et al., 2020). Oxygen minimum zones (OMZs) located close to productive eastern boundary upwelling systems (EBUSs) and the Arabian Sea may expand or shift in spatial extent dramatically, thereby impacting regional marine habitats (Stramma et al., 2012) and ecosystem services (Lachkar et al., 2023). [...]".

 

Source: Frontiers in Marine Science
Authors: Masahito Shigemitsu et al.
DOI: https://doi.org/10.3389/fmars.2023.1355015

Read the full article here.


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.


Seasonality and response of ocean acidification and hypoxia to major environmental anomalies in the southern Salish Sea, North America (2014–2018)

Abstract.

"Coastal and estuarine ecosystems fringing the North Pacific Ocean are particularly vulnerable to ocean acidification, hypoxia, and intense marine heatwaves as a result of interactions among natural and anthropogenic processes. Here, we characterize variability during a seasonally resolved cruise time series (2014–2018) in the southern Salish Sea (Puget Sound, Strait of Juan de Fuca) and nearby coastal waters for select physical (temperature, T; salinity, S) and biogeochemical (oxygen, O2; carbon dioxide fugacity, fCO2; aragonite saturation state, Ωarag) parameters. [...]".

 

Source: Biogeosciences
Authors: Simone R. Alin et al.
DOI: https://doi.org/10.5194/bg-21-1639-2024

Read the full article here.


Hypoxia also occurs in small highly turbid estuaries: the example of the Charente (Bay of Biscay)

Abstract.

"The French coast facing the Bay of Biscay (North-East Atlantic) is characterised by the presence of small macrotidal and turbid estuaries, including the Charente, which is geographically located between the two large estuaries of the Gironde and the Loire (south-west France). Multi-year, multi-site and high-frequency water quality surveys have shown that the Loire and, to a lesser extent, the Gironde suffer from summer hypoxia. These observations raised the question of the possible occurrence of hypoxia, particularly in one of these small estuaries, the Charente, which flows into the Bay of Marennes-Oléron, the first oyster-farming area in France. [...]".

 

Source: Biogeosciences
Authors: Sabine Schmidt & Ibrahima Iris Diallo
DOI: https://doi.org/10.5194/bg-21-1785-2024

Read the full article here.


Bottom-water hypoxia in the Paracas Bay (Peru, 13.8°S) associated with seasonal and synoptic time scale variability of winds and water stratification

Abstract.

"Coastal hypoxia can occur naturally in inshore areas of the Eastern Boundary Upwelling Systems, influenced by the nutrient-rich and low-oxygen upwelling waters. This study aims to explore the influence of water stratification and winds on bottom-water hypoxia of the Paracas Bay, an area subjected to the most intense alongshore winds and active coastal upwelling in the Peruvian coast. Monitoring data of the Pisco-Paracas water properties [...]".

 

Source: Science Direct
Authors: Lander Merma-Mora et al.
DOI: https://doi.org/10.1016/j.jmarsys.2023.103918

Read the full article here.


Linking northeastern North Pacific oxygen changes to upstream surface outcrop variations

Abstract.

"Understanding the response of the ocean to global warming, including the renewal of ocean waters from the surface (ventilation), is important for future climate predictions. Oxygen distributions in the ocean thermocline have proven an effective way to infer changes in ventilation because physical processes (ventilation and circulation) that supply oxygen are thought to be primarily responsible for changes in interior oxygen concentrations. Here, the focus is on the North Pacific thermocline, where some of the world's oceans' largest oxygen variations have been observed. [...]".

 

Source: Biogeosciences
Authors: Sabine Mecking & Kyla Drushka
DOI: https://doi.org/10.5194/bg-21-1117-2024

Read the full article here.


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