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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.


Preprint: ISASO2 : Recent trends and regional patterns of Ocean Dissolved Oxygen change

Abstract.

"Recent estimates of the global inventory of dissolved oxygen (DO) have suggested a decrease of 2 % since the 1960s. However, due to the sparse historical oxygen data coverage, the DO inventory exhibits large regional uncertainties at interannual timescale. Using ISASO2, a new DO Argo-based optimally interpolated climatology https://doi.org/10.17882/52367 (Kolodziejczyk et al.,2021), we have estimated an updated regional oxygen inventory. Over the long term (~1980–2013), comparing the ISASO2 Argo fields with the first guess WOA18 built from the DO bottle samples fields extracted from WOD18, the broad tendency to global ocean deoxygenation remains robust in the upper 2000 m with -451±243 Tmol per decade. [...]".

 

Source: Earth System Science Data
Authors: Nicolas Kolodziejczyk et al.
DOI: https://doi.org/10.5194/essd-2024-106

Read the full article here.


Preprint: Reviews and syntheses: Biological Indicators of Oxygen Stress in Water Breathing Animals

Abstract.

"Anthropogenic warming and nutrient over-enrichment of our oceans have resulted in significant, and often catastrophic, reductions in dissolved oxygen (deoxygenation). Stress on water-breathing animals from this deoxygenation has been shown to occur at all levels of biological organization: cellular; organ; individual; species; population; community; and ecosystem. Most climate forecasts predict increases in ocean deoxygenation, thus it is essential to develop reliable biological indicators of oxygen stress that can be used by regional and global oxygen monitoring efforts to detect and assess the impacts of deoxygenation on ocean life. [...]".

 

Source: EGUsphere 
Authors: Michael R. Roman et al.
DOI: https://doi.org/10.5194/egusphere-2024-616

Read the full article here.


Preprint: Signatures of Oxygen-Depleted Waters along the Sumatra-Java Coasts in the Southeastern Tropical Indian Ocean

Abstract.

"A prominent ocean region exhibiting depleted oxygen concentration is the northern Indian Ocean, whose projected deoxygenation trend in response to climate change requires a comprehensive understanding of the roles of ocean dynamics. We present newly compiled in situ data across platforms (e.g. cruises, Argo, buoy) in the Indonesian coasts of Sumatra and Java between 2010–2022. Combined with reanalysis products, our data detect oxygen-depleted waters attributed to the eastward advection of the northern Indian Ocean waters and monsoon-driven coastal upwelling. [...]".

 

Source: EGUsphere
Authors: Faisal Hamzah et al.
DOI: https://doi.org/10.5194/egusphere-2024-451

Read the full article here.


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.


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.


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.


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.


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.


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