Iron is an essential fuel for life in the oceans. The influence of this element on biogeochemistry — and nitrogen cycling in particular — varies across environments and time.
Response of export production and dissolved oxygen concentrations in oxygen minimum zones to pCO2 and temperature stabilization scenarios
"Dissolved oxygen (DO) concentration in the ocean is an important component of marine biogeochemical cycles and will be greatly altered as climate change persists. In this study a global oceanic carbon cycle model (HAMOCC 2.0) is used to address how mechanisms of oxygen minimum zone (OMZ) expansion respond to changes in CO2 radiative forcing. Atmospheric pCO2 is increased at a rate of 1 % annually and the model is stabilized at 2 ×, 4 ×, 6 ×, and 8 × preindustrial pCO2 levels. With an increase in CO2 radiative forcing, the OMZ in the Pacific Ocean is controlled largely by changes in particulate organic carbon (POC) export, resulting in increased remineralization and thus expanding the OMZs within the tropical Pacific Ocean. A potential decline in primary producers in the future as a result of environmental stress due to ocean warming and acidification could lead to a substantial reduction in POC export production, vertical POC flux, and thus increased DO concentration particularly in the Pacific Ocean at a depth of 600–800 m. In contrast, the vertical expansion of the OMZs within the Atlantic is linked to increases POC flux as well as changes in oxygen solubility with increasing seawater temperature. Changes in total organic carbon and increase sea surface temperature (SST) also lead to the formation of a new OMZ in the western subtropical Pacific Ocean. [...]"
SFB 754 International Conference
The distribution of oxygen in the ocean is controlled by physical, biogeochemical and biological processes. Both the supply and consumption of oxygen are sensitive to climate change in ways that are not fully understood.
Recent observations suggest that the oxygen content of the ocean is declining (ocean deoxygenation) and that oxygen minimum zones and coastal hypoxia sites are expanding with tremendous effects on the ocean’s ecosystems and living organisms.
- focused on the past, present and future state of oxygen in the ocean on global, regional and local scales
- analysed mechanisms and feedbacks critical to identify natural and anthropogenic causes of oxygen variability
- determined impacts on biogeochemical cycles and ecosystems
Start Date: 9/3/18
AGU fall meeting 2017
Start Date: 12/10/17
Good Hope For Earth Sciences, IAPSO-IAMAS-IAGA Joint Assembly
"The Local Organising Committee is thrilled to welcome you to the 2017 Joint IAPSO-IAMAS-IAGA Assembly in Cape Town, South Africa. The Joint Assembly, endorsed by the University of Cape Town and the South African Department of Science and Technology, will take place from 27 August to 1 September 2017 at the Cape Town International Convention Centre (CTICC)."
Read more about the 2017 Joint IAPSO-IAMAS-IAGA Assembly.
Sessions related to this websites context:
Session P03: Deoxygenation and de- nitrification, Convenors: Wajih Naqvik, Bo Thamdrup
Start Date: 8/26/17
"The Goldschmidt Conferences® were started in 1988 by the international Geochemical Society (GS) to provide a forum for its members to discuss their latest research. The conference is named in honour of Victor M. Goldschmidt (1888 - 1947), whose classification of the behaviour of the elements in the Earth and meteorites laid the basis of modern geochemistry. Each year, the conference brings together thousands of scientists from throughout the world to talk about subjects including the origin of the Earth and planets, the chemical processes that have shaped Earth's evolution over time, the interconnections between life and the physical world, the search for new resources, and the environmental challenges facing today's world."
Read more about the Goldschmidt Conference 2017.
Start Date: 8/12/17
Origin and fate of methane in the Eastern Tropical North Pacific oxygen minimum zone
"Oxygen minimum zones (OMZs) contain the largest pools of oceanic methane but its origin and fate are poorly understood. High-resolution (<15 m) water column profiles revealed a 300 m thick layer of elevated methane (20–105 nm) in the anoxic core of the largest OMZ, the Eastern Tropical North Pacific. Sediment core incubations identified a clear benthic methane source where the OMZ meets the continental shelf, between 350 and 650 m, with the flux reflecting the concentration of methane in the overlying anoxic water. Further incubations characterised a methanogenic potential in the presence of both porewater sulphate and nitrate of up to 88 nmol g−1day−1 in the sediment surface layer. In these methane-producing sediments, the majority (85%) of methyl coenzyme M reductase alpha subunit (mcrA) gene sequences clustered with Methanosarcinaceae ([above] 96% similarity to Methanococcoides sp.), a family capable of performing non-competitive methanogenesis. Incubations with C-CH4 showed potential for both aerobic and anaerobic methane oxidation in the waters within and above the OMZ. Both aerobic and anaerobic methane oxidation is corroborated by the presence of particulate methane monooxygenase (pmoA) gene sequences, related to type I methanotrophs and the lineage of Candidatus Methylomirabilis oxyfera, known to perform nitrite-dependent anaerobic methane oxidation (N-DAMO), respectively."
MSM61: DIVE INTO THE DEEP
"The deep sea is the largest environment on the planet. Most of the deep sea consists of the water column above the seafloor, the pelagic zone. In many parts of the pelagic ocean, no scientific sample or observation has ever been collected. Consequently, knowledge on deep-sea pelagic biodiversity and on the biology and ecology of organisms in this realm remain largely unknown.
During MSM61 we perform deployments with the pelagic in situ observation system or PELAGIOS. This ocean instrument collects high definition video during horizontal transects while being towed on a CTD cable at various depths of interest.[...]"
Widespread loss of ocean oxygen to become noticeable in 2030s
Upwelling intensity modulates nitrous oxide concentrations over the western Indian shelf
"Repeat measurements of dissolved nitrous oxide (N2O) along two transects of the western continental shelf of India in 2012 revealed high concentrations of 45 ± 32 nM (off Kochi) and 73 ± 63 nM (off Mangalore) during the summer monsoon (SM). N2O concentrations increased nonlinearly during the peak of the SM upwelling, when low O2 (<25 µM) conditions prevailed in the water column. Off Kochi, N2O levels fell gradually from the fall intermonsoon (20 ± 8 nM) to the winter monsoon (8.8 ± 2 nM) and remained low (9.2 ± 5.2 nM) through the spring intermonsoon season. The N2O supersaturation off Kochi (574 ± 720%) was presumably due to its high yield during sediment denitrification, whereas the higher N2O supersaturation observed off Mangalore (1046 ± 885%) was due to its production during denitrification in both the anoxic water column and the underlying sediments. Such distinctive biogeochemical behavior between these two shelf segments is at first augmented by the natural origin of intense upwelling at Mangalore relative to Kochi wherein suboxic to anoxic oxygen minimum zone waters spread from offshore to the shelf of Mangalore, over which the runoff and terrestrial nutrients supply acts in unison.[...]"
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