Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Nitrogen losses off the Coast of Oman

02.08.2011
Intensive Nitrogen losses off the coast of Oman
Caused by Coupling of two microbial processes

Nitrogen is an essential nutrient and often a limiting factor for all life on our planet. It is present in proteins and DNA. In the oceans, microbial processes regulate the concentrations and fluxes of biological relevant nitrogen compounds like ammonia, nitrite and nitrate, which have to be available for the marine life. The major sink through which nitrogen can escape from the marine food web into the atmosphere is as nitrogen gas, N2. The driving forces balancing this system are more complex than previously thought.


The Arabian Sea is part of the Indian Ocean and is bordered by India, Pakistan, Oman and Somalia.
Manfred Schloesser, Max Planck Institute for Marine Microbiology


N-losses as a result of the coupling of two reaction pathways. In the Arabian Sea off the coast of Oman, DNRA (blue) provides ammonia for the anammox reaction (yellow), thus producing nitrogen gas N2that can escape from the water column. Nitrate reduction and nitrification also take place and act as sources of nitrite, and also of ammonia by the former reaction. Meanwhile, there is little evidence for denitrification activity (red dashes).
modified from Lam et al., PNAS, 106:4752-4757).

Now scientists from the Max Planck Institute for Marine Microbiology and their colleagues have taken a very close look at the microbial processes in the Arabian Sea and published their results in two scientific papers.

The marine food web stores huge amounts of organic carbon compounds. The carbon cycle is interacting with both the dissolved molecular oxygen (O2) and the nitrogen cycle. Global warming results in a diminished solubility of oxygen, and the influx of waste-water loaded with organic compounds from the human civilization further consumes oxygen. Consequently, the oxygen-deficient waters or oxygen minimum zones (OMZ), which originally constituted only
The Arabian Sea harbors one of the three largest OMZs in the world and about 10-20 % of all global marine N-losses is thought to happen there. Thus far, it has been regarded as a fact that a bacterial process called denitrification was the major pathway resulting in N-losses from the Arabian Sea, via the stepwise reduction of nitrate to nitrite, then to nitric oxide, nitrous oxide and eventually gaseous nitrogen N2. Earlier studies from other authors claimed low oxygen and simultaneously high nitrite concentrations to be an indicator for denitrification and subsequent N-losses, but actual activity measurements have been rare. To solve this puzzle, researchers from the Max Planck Institute for Marine Microbiology including Phyllis Lam, Marlene Jensen and Marcel Kuypers, teamed up with scientists from Kiel, Oldenburg, Hamburg, Aarhus (Denmark), Nijmegen, (the Netherlands) and Princeton (USA), to trace the individual reaction steps in the nitrogen cycle by following the fate of compounds labeled with the stable isotope of 15N. Additionally, they identified the responsible microorganisms and active expression of the corresponding biomarker genes.

Their findings were surprising. The central-northeastern area of the Arabian Sea, which was thought to be the stronghold, was proven to be almost inactive in N-losses during their visit. The scientists now explain the high nitrite concentrations found there by a slow nitrate reduction and little oxidation of ammonia. Both reactions can run under low oxygen conditions and form nitrite as a final product. Satellite data from the past 10 years show that surface phytoplankton production in this region is not particularly high on average. Due to such likely missing organic matter, nitrite cannot be reduced further. Together with the sluggish water circulation, nitrite therefore accumulates in this region of the Arabian Sea.

On the contrary, in the northwestern part off the coast of Oman, which was previously assumed to be irrelevant regarding nitrogen balances, the researchers detected very high N-loss activity. As shown in their publications, two coupled reactions in the nitrogen cycle can do the trick: the anammox reaction (anaerobic oxidation of ammonia) and the dissimilatory nitrate reduction to ammonia (DNRA). Like in a detective story, the scientists found the telltale evidence of 15N-labeled compounds, as double-15N-labeled N2 was formed from labeled nitrite through a combination of anammox and DNRA. DNRA provides the important ammonia for the anammox reaction, which needs both ammonia and nitrite to form gaseous N2. Further proof came from gene expression studies showing which microbial genes were actively engaged in the pathways. This DNRA-anammox coupling, in addition to some anammox alone, explains the high N-loss in these waters.

Dr. Marcel Kuypers, Max Planck director, says: “Our findings fit very well with our previous results from other OMZs like the upwelling regions off the coasts of Peru, Chile and Namibia, where we also found anammox to be the most important N-loss pathway. The high nitrite concentrations in the central-northeastern Arabian Sea are presumably the last traces of earlier events which are now leveling off.”

Dr. Phyllis Lam from the Max Planck Institute adds: “In the future, the Arabian Sea should remain in our research focus, as reactions therein have strong impacts on the global nitrogen balance. It is unlikely that active nitrogen cycling remains the same throughout the year with respect to the seasonal monsoons, and it will continue to alter with the increasing amounts of nitrogen inputs from the atmosphere and land due to human activities. Unfortunately, pirate activities will not allow further research expeditions in the area any time soon.”

Manfred Schloesser

Further information
Dr. Phyllis Lam
Max Planck Institute for Marine Microbiology
Phone +49 (0)421 2028 644; plammpi-bremen.de
Dr. Marcel Kuypers
Max Planck Institute for Marine Microbiology
Phone +49 (0)421 2028 602; mkuypersmpi-bremen.de
Dr. Marlene Mark Jensen
Technical University of Denmark
Phone +45 45251437; mmajenv.dtu.dk
Press officer
Dr. Manfred Schloesser, phone +49 (0)421 2028 704;
mschloesmpi-bremen.de
1. Original article
Origin and fate of the secondary nitrite maximum in the Arabian Sea. P. Lam, M. M. Jensen , A. Kock , K. A. Lettmann, Y. Plancherel, G. Lavik, H. W. Bange , and M. M. M. Kuypers. Biogeosciences, 8, 1565–1577, 2011

doi:10.5194/bg-8-1565-2011

Institutions
Max Planck Institute for Marine Microbiology, Bremen, Germany
IFM-GEOMAR, Kiel, Germany
Institut für Chemie und Biologie des Meeres, Universität Oldenburg, Germany
Department of Geosciences, Princeton University, USA
2. Original article
Intensive nitrogen loss over the Omani Shelf due to anammox coupled with dissimilatory nitrite reduction to ammonium. Marlene M Jensen, Phyllis Lam, Niels Peter Revsbech, Birgit Nagel, Birgit Gaye, Mike SM Jetten and Marcel MM Kuypers. The ISME Journal (2011) 1-11. doi:10.1038/ismej.2011.44

Institutions

Max Planck Institute for Marine Microbiology, Bremen, Germany
Institute of Biological Sciences, University of Aarhus, Aarhus, Denmark
Institute of Coastal Research, GKSS Research Center, Geesthacht, Germany
Institute of Biogeochemistry and Marine Chemistry, University of Hamburg, Germany

Department of Microbiology, IWWR, Radbound University Nijmegen, The Netherlands

Dr. Manfred Schloesser | Max-Planck-Institut
Further information:
http://www.mpi-bremen.de/

More articles from Ecology, The Environment and Conservation:

nachricht Global threat to primates concerns us all
19.01.2017 | Deutsches Primatenzentrum GmbH - Leibniz-Institut für Primatenforschung

nachricht Reducing household waste with less energy
18.01.2017 | FIZ Karlsruhe – Leibniz-Institut für Informationsinfrastruktur GmbH

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>