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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

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Observed denitrification in the northeast Arabian Sea during the winter-spring transition of 2009

Abstract. 

"The central and northeast Arabian Sea (AS) has an intense and thick oxygen minimum zone (OMZ) and denitrification zone. It is comparable with the strongest OMZ of the north-equatorial Pacific Ocean. Denitrification in the AS is revisited using a set of cruise observations collected during February–March of 2009 by the Centre for Marine Living Resources, India. The region possesses one of the most robust N* depleted water reaching as low as -20 μmol l−1 at depths (~600 m). In AS, the oxygen depletion is mainly due to sluggish circulation, weak lateral and vertical ventilation. The biological respiration in oxygen deficit condition depletes nitrate and further modifies the Redfield ratio at intermediate depths (200-600 m) from 16N:1P to 8N:1P. [...]".

 

Source: Science Direct

Authors: Anju Mallissery et al.

DOI: https://doi.org/10.1016/j.jmarsys.2021.103680

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Denitrification Aligns with N2 Fixation in Red Sea Corals

Abstract.

"Denitrification may potentially alleviate excess nitrogen (N) availability in coral holobionts to maintain a favourable N to phosphorous ratio in the coral tissue. However, little is known about the abundance and activity of denitrifiers in the coral holobiont. The present study used the nirS marker gene as a proxy for denitrification potential along with measurements of denitrification rates in a comparative coral taxonomic framework from the Red Sea: Acropora hemprichiiMillepora dichotoma, and Pleuractis granulosa. [...]"

Source: Scientific Reports
Authors: Arjen Tilstra et al.
DOI: 10.1038/s41598-019-55408-z

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Latitudinal variations in δ30Si and δ15N signatures along the Peruvian shelf: quantifying the effects of nutrient utilization versus denitrification..

..over the past 600 years

Abstract.

"The stable sedimentary nitrogen isotope compositions of bulk organic matter (δ15Nbulk) and the silicon isotope composition of diatoms (δ30SiBSi) both mainly reflect the degree of past nutrient utilization by primary producers. However, in ocean areas where anoxic and suboxic conditions prevail, the δ15Nbulk signal ultimately recorded within the sediments is also influenced by water column denitrification, causing an increase in the subsurface δ15N signature of dissolved nitrate (δ15NO3) upwelled to the surface. [...]"

Source: Biogeosciences
Authors: Kristin Doering et al.
DOI: 10.5194/bg-16-2163-2019

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Identifying the origin of nitrous oxide dissolved in deep ocean by concentration and isotopocule analyses

Abstract.

"Nitrous oxide (N2O) contributes to global warming and stratospheric ozone depletion. Although its major sources are regarded as bacterial or archaeal nitrification and denitrification in soil and water, the origins of ubiquitous marine N2O maximum at depths of 100–800 m and N2O dissolved in deeper seawater have not been identified. [...]"

Source: Scientific Reports 
Authors: Sakae Toyoda et al.
DOI: 10.1038/s41598-019-44224-0

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Nitrogen isotope evidence for expanded ocean suboxia in the early Cenozoic

Abstract.

"The million-year variability of the marine nitrogen cycle is poorly understood. Before 57 million years (Ma) ago, the 15N/14N ratio (δ15N) of foraminifera shell-bound organic matter from three sediment cores was high, indicating expanded water column suboxia and denitrification. [...]"

Source: Science
Authors: Emma R. Kast et al.
DOI: 10.1126/science.aau5784

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Deep-sea sponge grounds as nutrient sinks: High denitrification rates in boreo-arctic sponges

Abstract.

"Sponges are commonly known as general nutrient providers for the marine ecosystem, recycling organic matter into various forms of bio-available nutrients such as ammonium and nitrate. In this study we challenge this view. We show that nutrient removal through microbial denitrification is a common feature in six cold-water sponge species from boreal and Arctic sponge grounds. [...]"

Source: Biogeosciences
Authors: Christine Rooks et al.
DOI: 10.5194/bg-2019-135

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Role of organic components in regulating denitrification in coastal water of Daya Bay, southern China

Abstract.

"Both dissolved and particulate organic materials have been proposed to be important factors in regulating the heterotrophic denitrification in various aquatic environments. However, specific pathways and mechanisms remain elusive. In this study, water column samples were collected from Daya Bay, southern China, to examine the relationships between potential denitrification and different organic components in the water column. Bulk dissolved organic carbon (DOC) was categorized into three major components including terrigenous fluorescent (tFDOC), autochthonous fluorescent (bFDOC) and non-fluorescent (nFDOC) fractions, while the bulk particulate organic carbon (POC) was divided into terrigenous (tPOC) and autochthonous (bPOC) based on an isotope mixing model [...]"

Source: Environmental Science: Processes & Impacts
Authors: Jian Zeng
DOI: 10.1039/C8EM00558C

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Efficient recycling of nutrients in modern and past hypersaline environments

Abstract.

"The biogeochemistry of hypersaline environments is strongly influenced by changes in biological processes and physicochemical parameters. Although massive evaporation events have occurred repeatedly throughout Earth history, their biogeochemical cycles and global impact remain poorly understood. Here, we provide the first nitrogen isotopic data for nutrients and chloropigments from modern shallow hypersaline environments (solar salterns, Trapani, Italy) and apply the obtained insights to δ15N signatures of the Messinian salinity crisis (MSC) in the late Miocene. [...]"

Source: Scientific Reports
Authors: Y. Isaji et al.
DOI: 10.1038/s41598-019-40174-9

Read the full article here.


Anammox and denitrification in the oxygen minimum zone of the eastern South Pacific

Abstract.

"We quantified the removal of fixed nitrogen as N2 production by anammox and N2 and N2O production by denitrification over a distance of 1900 km along the coasts of Chile and Peru, using short‐term incubations with 15N‐labeled substrates. The eastern South Pacific contains an oxygen minimum zone (OMZ) characterized by an anoxic, nitrate‐ and nitrite‐rich layer of ∼ 200‐m thickness below 30–90 m of oxic water. [...]"

Source: Limnology and Oceanography
Authors: Tage Dalsgaard et al.
DOI: 10.4319/lo.2012.57.5.1331

Read the full article here.


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