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Impacts of hypoxic events surpass those of future ocean warming and acidification

Abstract.

"Over the past decades, three major challenges to marine life have emerged as a consequence of anthropogenic emissions: ocean warming, acidification and oxygen loss. While most experimental research has targeted the first two stressors, the last remains comparatively neglected. Here, we implemented sequential hierarchical mixed-model meta-analyses (721 control–treatment comparisons) to compare the impacts of oxygen conditions associated with the current and continuously intensifying hypoxic events (1–3.5 O2 mg l−1) with those experimentally yielded by ocean warming (+4 °C) and acidification (−0.4 units) conditions[...]"

 

Source: Nature Ecology & Evolution 
Authors: Eduardo Sampaio et al.
DOI: https://doi.org/10.1038/s41559-020-01370-3

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Bacteriohopanepolyols signature in sediments of the East China Sea and its indications for hypoxia and organic matter sources

Abstract.

"The bacterial biomarker group of bacteriohopanepolyols (BHPs) has shown a significant potential to track terrestrial inputs and to respond to environmental changes. A total of 12 BHPs were detected in surface sediments of the East China Sea (ECS), with the contents of 3.79–361 μg/g TOC. The spatial distribution patterns and correlation analyses of bacteriohopanetetrol (BHT) and soil marker BHPs in sediments of the ECS indicate that they were mainly derived from marine autochthonous and terrestrial sources[...]"

 

Source: Science Direct
Authors: Meiling Yin et al.
DOI: https://doi.org/10.1016/j.orggeochem.2021.104268

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Variable coastal hypoxia exposure and drivers across the southern California Current

Abstract.

"Declining oxygen is one of the most drastic changes in the ocean, and this trend is expected to worsen under future climate change scenarios. Spatial variability in dissolved oxygen dynamics and hypoxia exposures can drive differences in vulnerabilities of coastal ecosystems and resources, but documentation of variability at regional scales is rare in open-coast systems. Using a regional collaborative network of dissolved oxygen and temperature sensors maintained by scientists and fishing cooperatives from California, USA, and Baja California, Mexico, we characterize spatial and temporal variability in dissolved oxygen[...]"

 

Source: Nature Scientific Reports
Authors: Natalie H. N. Low et al.
DOI: https://doi.org/10.1038/s41598-021-89928-4

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Increase of a hypoxia-tolerant fish, Harpadon nehereus (Synodontidae), as a result of ocean deoxygenation off southwestern China

Abstract.

"We report a sudden explosive rise in abundance off southeastern China of a fish species that is hypoxia-tolerant, Bombay duck (Harpadon nehereus, Family Synodontidae), belonging to an Order (the Aulopiformes) encompassing overwhelmingly deep-sea fishes, but which predominantly occurs in coastal water. We suggest that this is made possible by the very high water content of its muscle and other tissues (about 90%, vs 75–80% for other coastal fish), which reduces its oxygen requirements and allows it to outcompete other fish in low-oxygen[...]"

 

Source: Environmental Biology of Fishes
Authors: Bin Kang et al.
DOI: https://doi.org/10.1007/s10641-021-01130-7

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Modeling the role of riverine organic matter in hypoxia formation within the coastal transition zone off the Pearl River Estuary

Abstract.

"Globally expanding hypoxia in estuaries and coastal oceans has largely been attributed to the elevated river nutrient inputs, whereas the role of river-delivered terrestrial organic matter (OMterr) in hypoxia formation has been less investigated. This study uses a coupled physical-biogeochemical model and observations to investigate how OMterr directly (via remineralization) and indirectly (via the nutrients released from OMterr remineralization) promotes hypoxia development in the coastal transition zone[...]"

 

Source: Association for the Sciences of Limnology and Oceanography
Authors: Liuqian Yu et al.
DOI: https://doi.org/10.1002/lno.11616

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Response of benthic nitrogen cycling to estuarine hypoxia

Abstract.

"The effects of bottom water oxygen concentration on sediment oxygen uptake, oxygen penetration depth, nitrate and ammonium fluxes, anammox, denitrification, dissimilatory nitrate reduction to ammonium, nitrification, and mineralization were investigated off the Changjiang estuary and its adjacent East China Sea, by combining a seasonal comparison[...]"

 

Source: ASLO- Association for the Sciences Limnology and Oceanography
Authors: Guodong Song et al.
DOI: https://doi.org/10.1002/lno.11630

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Benthic fluxes of oxygen and heat from a seasonally hypoxic region of Saanich Inlet fjord observed by eddy covariance

Abstract.

"Benthic habitats within fjords are predominantly insulated from the high energy physical dynamics of open coastlines. As a result, fjords may have atypical mass and heat transfer rates at the seafloor. This study presents aquatic eddy covariance (EC) measurements made continuously from late May 2013 through December 2013, in Saanich Inlet fjord, British Columbia, to assess areal-averaged benthic fluxes of dissolved oxygen and heat, and their relationships to bottom boundary layer dynamics and water properties. The measurements were achieved by the connection of a system of underwater EC sensors to Ocean Network Canada's Victoria Experimental Network Under the Sea (VENUS) observatory that has a primary seafloor node[...]"

 

Source: Science Direct
Authors: Clare E. Reimers et al.
DOI: https://doi.org/10.1016/j.ecss.2020.106815

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Recovery from multi-millennial natural costal hypoxia in the Stockholm Archipelago, Baltic Sea, terminated by modern human activity

Abstract.

"Enhanced nutrient input and warming have led to the development of low oxygen (hypoxia) in coastal waters globally. For many coastal areas, insight into redox conditions prior to human impact is lacking. Here, we reconstructed bottom water redox conditions and sea surface temperatures (SSTs) for the coastal Stockholm Archipelago over the past 3000 yr. Elevated sedimentary concentrations of molybdenum indicate (seasonal) hypoxia between 1000 b.c.e. and 1500 c.e. Biomarker[...]"

 

Source: Association for the Sciences of Limnology and Oceanography
Authors: Niels A. G. M. van Helmond et al.
DOI: https://doi.org/10.1002/lno.11575

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Benthic fluxes of oxygen and nutrients under the influence of macrobenthic fauna on the periphery of the intermittently hypoxic zone in the Baltic Sea

Abstract.

"Understanding the role of benthic organisms in marine sediments is becoming increasingly important with the growing problem of eutrophication of marine ecosystems around the world, including the Baltic Sea. Therefore, we have conducted a series of incubation experiments on sediment cores collected from sites characterized by varying oxygen conditions and measured the influx (uptake by sediment) of oxygen as well as the sediment–water exchange of phosphate, ammonia and silicate.[...]"

 

Source: Science Direct
Authors: Halina Kendzierska et al.
Doi: https://doi.org/10.1016/j.jembe.2020.151439

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Impacts of climate change on dissolved oxygen concentration relevant to the costal and marine environment around the UK

Abstract.

"The decline in dissolved oxygen and onset of oxygen deficiency and hypoxia are naturally occurring phenomenon in aquatic environments, typically occurring on seasonal timescales. Over decadal timescales, there has been a measurable decline in dissolved oxygen concentrations in the global ocean due to warming caused by anthropogenic activity. Approximately 15% of the global decline in oxygen has been attributed to reduced solubility in response to ocean warming, with the remaining 85% due to intensified stratification. The relative contribution of these factors in coastal and shelf-sea waters is currently unknown. In UK waters, sustained observations in the North[...]"

 

Source: MCCIP Science Review
Authors: Mahaffey, C et al.
DOI: https://doi.org/10.14465/2020.arc02.oxy

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