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Sedimentary molybdenum and uranium: Improving proxies for deoxygenation in coastal depositional environments

Abstract. 

"Sedimentary molybdenum (Mo) and uranium (U) enrichments are widely used to reconstruct changes in bottom water oxygen conditions in aquatic environments. Until now, most studies using Mo and U have focused on restricted suboxic-euxinic basins and continental margin oxygen minimum zones (OMZs), leaving mildly reducing and oxic (but eutrophic) coastal depositional environments vastly understudied. Currently, it is unknown: (1) to what extent Mo and U enrichment factors (Mo- and U-EFs) can accurately reconstruct oxygen conditions in coastal sites experiencing mild deoxygenation, and (2) to what degree secondary [...]". 

 

Source: Science Direct 
Authors: K. Mareike Paul et al.
DOI: https://doi.org/10.1016/j.chemgeo.2022.121203

Read the full article here.


Otoliths of marine fishes record evidence of low oxygen, temperature and pH conditions of deep Oxygen Minimum Zones

Abstract.

"The deep-sea is rapidly losing oxygen, with profound implications for marine organisms. Within Eastern Boundary Upwelling Systems, such as the California and the Benguela Current Ecosystems, an important question is how the ongoing expansion, intensification and shoaling of Oxygen Minimum Zones (OMZs) will affect deep-sea fishes throughout their lifetimes. One of the first steps to filling this knowledge gap is through the development of tools and techniques to track fishes’ exposure to hypoxic (<45 μmol kg-1), low-temperature (∼4–10°C) and low-pH (∼7.5) waters when inhabiting OMZs. [...]".

 

Source: Science Direct 
Authors: Leticia Maria Cavole et al.
DOI: https://doi.org/10.1016/j.dsr.2022.103941

Read the full article here.


Nature Scientific Reports collection on ocean hypoxia: Call for papers

Call for paper manuscripts

We would like to draw your attention to a new collection on ocean hypoxia in Scientific Reports.

The paper manuscript submission deadline is 4 April 2023.

For further information about the call, visit: https://www.nature.com/collections/bgdgcgahcf/


Oxygen availability driven trends in DOM molecular composition and reactivity in a seasonally stratified fjord

Abstract. 

"Ocean deoxygenation could potentially trigger substantial changes in the composition and reactivity of dissolved organic matter (DOM) pool, which plays an important role in the global carbon cycle. To evaluate links between DOM dynamics and oxygen availability, we investigated the DOM composition under varying levels of oxygen in a seasonally hypoxic fjord through a monthly time-series over two years. We used ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to characterize DOM on a molecular level. [...]".

 

Source: Science Direct 
Authors: Xiao Chen et al.
DOI: https://doi.org/10.1016/j.watres.2022.118690

Read the full article here.


Coastlines at Risk of Hypoxia From Natural Variability in the Northern Indian Ocean

Abstract. 

"Coastal hypoxia—harmfully low levels of oxygen—is a mounting problem that jeopardizes coastal ecosystems and economies. The northern Indian Ocean is particularly susceptible due to human-induced impacts, vast naturally occurring oxygen minimum zones, and strong variability associated with the seasonal monsoons and interannual Indian Ocean Dipole (IOD). We assess how natural factors influence the risk of coastal hypoxia by combining a large set of oxygen measurements with satellite observations to examine how the IOD amplifies or suppresses seasonal hypoxia tied to the Asian Monsoon. We show that on both seasonal and interannual timescales hypoxia is controlled by wind- and coastal Kelvin wave-driven upwelling of oxygen-poor waters onto the continental shelf and reinforcing biological feedbacks (increased subsurface oxygen demand). [...]".

 

Source: Global Biogeochemical Cycles
Authors: Jenna Pearson et al.
DOI: https://doi.org/10.1029/2021GB007192

Read the full article here.


Widespread oxyregulation in tropical corals under hypoxia

Abstract. 

"Hypoxia (low oxygen stress) is increasingly reported on coral reefs, caused by ocean deoxygenation linked to coastal nutrient pollution and ocean warming. While the ability to regulate respiration is a key driver of hypoxia tolerance in many other aquatic taxa, corals' oxyregulatory capabilities remain virtually unexplored. Here, we examine O2-consumption patterns across 17 coral species under declining O2partial pressure (pO2). All corals showed ability to oxyregulate, but total positive regulation (Tpos) varied between species, ranging from 0.41 (Pocillopora damicornis) to 2.42 (P. acuta). [...]".

 

Source: Science Direct 
Authors: David J. Hughes et al.
DOI: https://doi.org/10.1016/j.marpolbul.2022.113722

Read the full article here.


Temperature and oxygen supply shape the demersal community in a tropical Oxygen Minimum Zone

Abstract. 

"The organisms that inhabit Oxygen Minimum Zones (OMZ) have specialized adaptations that allow them to survive within a very narrow range of environmental conditions. Consequently, even small environmental perturbations can result in local species distribution shifts that alter ecosystem trophodynamics. Here, we examined the effect of changing sea water temperatures and oxygen levels on the physiological performance and metabolic traits of the species forming marine demersal communities along the OMZ margins in the Costa Rican Pacific. The strong temperature and oxygen gradients along this OMZ margin provide a “natural experiment” to explore the effects of warming and hypoxia on marine demersal communities. [...]".

 

Source: Environmental Biology of Fishes

Authors: Tayler M. Clarke et al. 

DOI: https://doi.org/10.1007/s10641-022-01256-2

Read the full article here.


Evidence of hypoxia in the eastern coast of the Gulf of California as induced by stable nitrogen isotopes in surface sediments

Abstract. 

"The Gulf of California is a highly biodiverse marine basin located in the northeast Mexican Pacific Ocean. In the past three decades, this basin has experienced increased hypoxia in shallow waters, which threatens its coastal ecosystems. The aim of this study is to analyze δ15N and δ13C isotopes of organic matter in coastal sediments to characterize sources of primary production and shifts in biogeochemical processes that reflect increasing oxygen deficiency in the shallow coast of the eastern Gulf of California. Surface sediments samples were collected from 8 to 47 m deep along the coastal margin of Sinaloa and Sonora. This region is characterized by the development of anthropogenic activities, which could be the main source of organic matter evidenced in the marine environment. [...]". 

 

Source: Science Direct

Authors: Alberto Sánchez et al. 

DOI: https://doi.org/10.1016/j.csr.2022.104716

Read the full article here.


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

Read the full article here.


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

Read the full article here.


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