News

Autonomous profiling float observations reveal the dynamics of deep biomass distributions in the denitrifying oxygen minimum zone of the Arabian Sea

Abstract.

"Data from 13 autonomous profiling BGC-Argo floats, equipped with biogeochemical and bio-optical sensors deployed between 2011 and 2016, were used to explore the potential of bio-optical methods to map deep biomass distribution in the Arabian Sea oxygen minimum zone (OMZ). Dissolved oxygen sensors revealed concentrations below 5 μmol kg−1 for much of the depth range between 200 and 400 m and below 1 μmol kg−1 in the centre of the OMZ, which is well below climatological values. [...]"

Source: Journal of Marine Systems
Authors: Bożena Wojtasiewicz et al.
DOI: 10.1016/j.jmarsys.2018.07.002

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Fixed nitrogen loss from the eastern tropical North Pacific and Arabian Sea oxygen deficient zones determined from measurements of N2:Ar

Abstract.

"Previous work estimating the N2excess above background due to denitrification has suggested that nitrate deficit-type methods may be an underestimate of fixed nitrogen (N) loss in the major oxygen deficient zones of the ocean. The N2excess approach has the advantage over nitrate deficit-type methods in that it does not depend on stoichiometric assumptions of fixed N to phosphate or oxygen utilization and avoids any uncertainly regarding the pathway of N loss. [...]"

Source: Global Geochemical Cycles (2012)
Authors: Bonnie X. Chang, Allan H. Devol and Steven R. Emerson
DOI: 10.1029/2011GB004207

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Slaking the world’s thirst with seawater dumps toxic brine in oceans

"Growing populations and tightening water supplies have spurred people in many places—including the Middle East, Australia, California and China—to look to the oceans and other salty waters as a source of new drinking water. But desalination plants are energy intensive and create a potentially environment-harming waste called brine (made up of concentrated salt and chemical residues), which is dumped into the ocean, injected underground or spread on land.

Despite the ecological threats, “there was no comprehensive assessment about brine—how much we produce,” says Manzoor Qadir, assistant director of the United Nations University Institute on Water, Environment and Health. So he and his colleagues calculated that figure and found it is 50 percent greater than the desalination industry’s previous rough estimate. In fact, it is enough to cover Florida with 30 centimeters of brine every year. [...]"

Source: Scientific American

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Vertical partitioning of nitrogen-loss processes across the oxic-anoxic interface of an oceanic oxygen minimum zone

Abstract.

"We investigated anammox, denitrification and dissimilatory reduction of nitrite to ammonium (DNRA) activity in the Eastern Tropical South Pacific oxygen minimum zone (OMZ) off northern Chile, at high‐depth resolution through the oxycline into the anoxic OMZ core. This was accompanied by high‐resolution nutrient and oxygen profiles to link changes in nitrogen transformation rates to physicochemical characteristics of the water column. Denitrification was detected at most depths, but anammox was the most active N2‐producing process, while DNRA was not detectable. [...]"

Source: Environmental Microbiology
Authors: Loreto De Brabandere et al.
DOI: 10.1111/1462-2920.12255

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The impact of primary and export production on the formation of the secondary nitrite maximum: A model study

Abstract.

"The so-called secondary nitrite maximum (SNM) is a pronounced subsurface feature in many oxygen deficient zones of the ocean. A nitrite layer of up to several hundred meters thickness indicates high microbial activity and nitrogen loss from the system. To study the effects of primary and export production on the SNM, we have developed a one-dimensional ecosystem model for oxygen deficient zones. Our model couples the marine nitrogen and oxygen cycles with physical water column processes, includes euphotic, aphotic, aerobic and anaerobic processes and thereby dynamically describes source and sink processes for nitrite. [...]"

Source: Ecological Modelling
Authors: Aike Beckmann and Inga Hense
DOI: 10.1016/j.ecolmodel.2017.05.014

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Planktonic food web structure and trophic transfer efficiency along a productivity gradient in the tropical and subtropical Atlantic Ocean

Abstract.

"Oligotrophic and productive areas of the ocean differ in plankton community composition and biomass transfer efficiency. Here, we describe the plankton community along a latitudinal transect in the tropical and subtropical Atlantic Ocean. Prochlorococcus dominated the autotrophic community at the surface and mixed layer of oligotrophic stations, replaced by phototrophic picoeukaryotes and Synechococcus in productive waters. [...]"

Source: Scientific Reports
Authors: Laia Armengol et al.
DOI: 10.1038/s41598-019-38507-9

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Job Offer: PhD candidate in the field biogeochemistry/microbiology

PhD candidate in the field biogeochemistry/microbiology within our upwelling project EVAR. 
The position should focus on governing parameters on nitrous oxide and/or methane cycling in the Benguela upwelling system, linking microbiology and trace gas biogeochemistry. It is really a very interesting and promising PhD-project, with support of two Post-Docs already hired within the project.

The deadline is February 15th.

For further information please read the attached document.


Metabolic preference of nitrate over oxygen as an electron acceptor in foraminifera from the Peruvian oxygen minimum zone

Abstract.

"Benthic foraminifera populate a diverse range of marine habitats. Their ability to use alternative electron acceptors—nitrate (NO3−) or oxygen (O2)—makes them important mediators of benthic nitrogen cycling. Nevertheless, the metabolic scaling of the two alternative respiration pathways and the environmental determinants of foraminiferal denitrification rates are yet unknown. We measured denitrification and O2 respiration rates for 10 benthic foraminifer species sampled in the Peruvian oxygen minimum zone (OMZ). [...]"

Source: PNAS
Authors: Nicolaas Glock et al.
DOI: 10.1073/pnas.1813887116

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Enhanced North Pacific deep-ocean stratification by stronger intermediate water formation during Heinrich Stadial 1

Abstract.

"The deglacial history of CO2 release from the deep North Pacific remains unresolved. This is due to conflicting indications about subarctic Pacific ventilation changes based on various marine proxies, especially for Heinrich Stadial 1 (HS-1) when a rapid atmospheric CO2 rise occurs. Here, we use a complex Earth System Model to investigate the deglacial North Pacific overturning and its control on ocean stratification. [...]"

Source: Nature Communications
Authors: X. Gong et al.
DOI: 10.1038/s41467-019-08606-2

Read the full article here.


Job Offer: Postdoctoral Researcher

Postdoctoral Researcher in the area of ocean physical and biogeochemical coupling to work with Professor Resplandy in the Princeton University Geosciences department. The postdoc will investigate the physical and biological processes at both global and local scale that control the evolution of the tropical Oxygen Minimum Zone in the Indian Ocean. Details of the project can be found at https://environment.princeton.edu/grandchallenges/research/energy/dead_zones. Ideally, candidates will have a strong background in numerical modeling, but candidates with the necessary background in geophysical fluid dynamics and/or ocean biogeochemistry will be given full consideration.

Applicants should include a cover letter, a curriculum vitae including a publication list, and contact information for three references by applying at https://www.princeton.edu/acad-positions/position/9941. Applications should be received by April 15, 2019.


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