Nitrogen isotope evidence for oxygenated upper ocean during the Cryogenian interglacial period
"The Cryogenian interglacial period have witnessed dramatic changes in climate, oceanic environment and biological evolution. The nitrogen isotopic composition, as an important biogeochemical proxy, has the potential to track both the nutrient cycling and redox conditions in the past. However, nitrogen isotopic data during this interglacial time is rather limited. Here, we present integrated data for nitrogen isotopes (δ15N), as well as organic carbon isotopes (δ13Corg), iron (Fe) speciation, pyrite morphology and trace elements from the Cryogenian interglacial Datangpo Formation derived from a drill core from South China to figure out the nitrogen cycling and coeval redox states. [...]".
Source: Science Direct
Authors: Guangyou Zhu et al.
Spatio-temporal variations in culturable bacterial community associated with denitrification in the Arabian Sea oxygen minimum zone
"The Arabian Sea (AS) oxygen minimum zone (OMZ) is a site of intense denitrification, contributing to 20% of the global oceanic denitrification, playing a significant role in the nitrogen cycle. In this study, the structure and diversity of culturable bacterial communities inhabiting the water column of the AS OMZ were investigated through phylogenetic analysis and nitrate-utilizing ability was studied through culture-based studies. A total of 248 isolates collected during pre-monsoon and post-monsoon season were analysed for 16S rRNA gene sequences. [...]".
Source: Marine Biology Research
Authors: Ujwala Amberkar et al.
Geochemistry of sediments in contact with oxygen minimum zone of the eastern Arabian Sea: Proxy for palaeo-studies
"The Arabian Sea encompasses oxygen minimum zone with denitrifying conditions. For the present study, sediments were collected across three transects off Goa transect (GT), Mangalore transect (MT) and Kochi transect (KT) in contact with water column dissolved oxygen (DO) range of 1.4–118.0 µM. Sediments were investigated for texture, clay mineralogy, total organic carbon (Corg), total nitrogen, CaCO3, δ15N, δ13C, metal content to infer their distribution with changing DO and their use as possible palaeo-proxies. The Corg (0.9–8.6%) is largely marine and δ15N from GT and MT preserves signatures of higher water column denitrification. [...]".
Source: Journal of Earth System Science
Authors: Pratima M. Kessarkar et al.
Evidence of hypoxia in the eastern coast of the Gulf of California as induced by stable nitrogen isotopes in surface sediments
"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.
Observed denitrification in the northeast Arabian Sea during the winter-spring transition of 2009
"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.
Denitrification Aligns with N2 Fixation in Red Sea Corals
"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 hemprichii, Millepora dichotoma, and Pleuractis granulosa. [...]"
Source: Scientific Reports
Authors: Arjen Tilstra et al.
Latitudinal variations in δ30Si and δ15N signatures along the Peruvian shelf: quantifying the effects of nutrient utilization versus denitrification..
..over the past 600 years
"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 (δ15NO−3) upwelled to the surface. [...]"
Authors: Kristin Doering et al.
Identifying the origin of nitrous oxide dissolved in deep ocean by concentration and isotopocule analyses
"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.
Nitrogen isotope evidence for expanded ocean suboxia in the early Cenozoic
"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. [...]"
Authors: Emma R. Kast et al.
Deep-sea sponge grounds as nutrient sinks: High denitrification rates in boreo-arctic sponges
"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. [...]"
Authors: Christine Rooks et al.
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