Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Breath-taking moments in the Black Sea: Periodic hypoxia affects seafloor fauna and carbon turnover

13.02.2017

Periodic oscillations of bottom-water oxygen concentrations can alter benthic communities and carbon storage for decades, reveals a new study published in Science Advances. This is particularly relevant as low oxygen conditions are on the rise in the world’s oceans.

The seafloor plays a key role in the global elemental cycles. Its inhabitants consume and recycle organic matter sinking to the bottom. Usually, only a minor part of that material gets buried in the seafloor. The lion’s share is remineralised by seafloor life – i.e. broken down and fed back to the ecosystem for the production of new biomass. Thus, the fate of this material at the seafloor crucially impacts global carbon and nutrient cycling and, as a consequence, marine productivity and our climate.


Sediment was retrieved with a Multicorer to allow for a detailed analysis of sediment biogeochemistry and its inhabitants along a transect of oxygen concentrations.

R. North, Eawag, Switzerland


Retrieval of cores from the seafloor with the submersible JAGO. Below the black layer that is visible close to the sediment surface the sediment is free of oxygen.

JAGO-Team, GEOMAR Kiel

Temporary shortage, long-term storage

Animals need oxygen to breathe. Hence, declining bottom-water oxygen supply negatively impacts the community composition and activity of marine sediments. To which extent it also determines remineralisation and thus carbon burial rates remained controversial.

Gerdhard Jessen from Max Planck Institute for Marine Microbiology in Bremen, Germany, and an international team of researchers reveal in Science Advances that declining bottom-water oxygen concentrations significantly influence carbon storage in the seafloor for decades. This effect happens earlier then previously thought and over larger areas of seafloor. When oxygen runs short, substantially less organic matter is remineralised and substantially more gets buried. And what gets buried stays buried for a long time.

„The amount of organic matter ending up in the seafloor increases by half when the seafloor is periodically short of oxygen”, says Jessen. „Even tasty and easily available bits, such as freshly deposited algal material, are not consumed.”

The Black Sea as a natural laboratory

Simulating such long-term and complex processes in the lab is hard to do. Therefore, Jessen and his colleagues took research vessel Maria S. Merian to the Black Sea, the largest naturally anoxic water body in the world, within the framework of the EU FP7 project HYPOX.

There, stable stratification results in a natural gradient of bottom-water oxygen concentrations at the outer shelf, ranging from well-oxygenated shallow waters over variable oxygen conditions to anoxic deeper waters below about 160 metres water depth. This provides for close-to-perfect experimental conditions. „We used the Black Sea seafloor as a natural laboratory. It allowed us to investigate what might be coming up to many party of the world’s oceans”, Jessen says.

„Low-oxygen areas in the oceans are on the rise, mainly as a consequence of anthropogenic nutrient inputs and climate change”, explains Antje Boetius, senior author of the study and group leader of the HGF-MPG Research Group for Deep Sea Ecology and Technology. „Thus, it is particularly important to understand and measure what oxygen stress in the oceans means for their inhabitants as well as the global biogeochemical cycles.”

Changing seafloor life

How come that the effects are so drastic if the seafloor runs periodically out of breath? „Oxygen deficiency changes the faunal community of the seafloor “, Boetius elaborates. In particular larger animals, such as worms and mussels, cannot survive without it. These animals rummage through the sediment looking for food and shelter, intermixing oxygen and nutrients for smaller seafloor inhabitants in the process. „The large organisms disappear when oxygen is scarce. Sediment bacteria alone are then responsible for the remineralisation of the organic matter arriving at the seafloor, but they move slowly and take very long to break down complex materials without the help of animals.”

As a result, under hypoxic conditions more organic material is buried and thus removed from the system. Anaerobic microorganisms, gaining their energy without oxygen for example by fermentation or sulphate reduction, take the helm. These also produce toxic sulphide, further slowing down the breakdown of materials.

„The Black Sea can teach us many lessons”, says Boetius, „as it clearly reveals the effects of fluctuating and low oxygen conditions on the ocean ecosystem, causing tremendous changes in the services of the ecosystem to us humans. Investigations as the current one are thus essential in the face of global change, to detect warning signals from the ocean in time.“

Original publication
Gerdhard L. Jessen, Anna Lichtschlag, Alban Ramette, Silvio Pantoja, Pamela E. Rossel, Carsten J. Schubert, Ulrich Struck, Antje Boetius: Hypoxia causes preservation of labile organic matter and changes seafloor microbial community composition (Black Sea). Science Advances 2017. DOI: 10.1126/sciadv.1601897

Participating institutes
Max Planck Institute for Marine Microbiology, Bremen, Germany
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany

University of Concepción, Concepción, Chile
ICBM-MPI Bridging Group, University of Oldenburg, Oldenburg, Germany
Eawag: Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland
Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Berlin, Germany

Please direct your queries to

Dr. Gerdhard Jessen
E-Mail: gjessen(at)mpi-bremen.de or

Prof. Dr. Antje Boetius
Phone: +49 421 2028 860
E-Mail: aboetius(at)mpi-bremen.de

or the press office

Dr. Fanni Aspetsberger
Dr. Manfred Schlösser
Phone: +49 421 2028 947
E-Mail: presse(at)mpi-bremen.de

Weitere Informationen:

http://www.mpi-bremen.de/en/Breathtaking_moments_in_the_Black_Sea.html

Dr. Fanni Aspetsberger | Max-Planck-Institut für marine Mikrobiologie

More articles from Earth Sciences:

nachricht Wintertime Arctic sea ice growth slows long-term decline: NASA
07.12.2018 | NASA/Goddard Space Flight Center

nachricht Why Tehran Is Sinking Dangerously
06.12.2018 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Researchers develop method to transfer entire 2D circuits to any smooth surface

What if a sensor sensing a thing could be part of the thing itself? Rice University engineers believe they have a two-dimensional solution to do just that.

Rice engineers led by materials scientists Pulickel Ajayan and Jun Lou have developed a method to make atom-flat sensors that seamlessly integrate with devices...

Im Focus: Three components on one chip

Scientists at the University of Stuttgart and the Karlsruhe Institute of Technology (KIT) succeed in important further development on the way to quantum Computers.

Quantum computers one day should be able to solve certain computing problems much faster than a classical computer. One of the most promising approaches is...

Im Focus: Substitute for rare earth metal oxides

New Project SNAPSTER: Novel luminescent materials by encapsulating phosphorescent metal clusters with organic liquid crystals

Nowadays energy conversion in lighting and optoelectronic devices requires the use of rare earth oxides.

Im Focus: A bit of a stretch... material that thickens as it's pulled

Scientists have discovered the first synthetic material that becomes thicker - at the molecular level - as it is stretched.

Researchers led by Dr Devesh Mistry from the University of Leeds discovered a new non-porous material that has unique and inherent "auxetic" stretching...

Im Focus: The force of the vacuum

Scientists from the Theory Department of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science (CFEL) in Hamburg have shown through theoretical calculations and computer simulations that the force between electrons and lattice distortions in an atomically thin two-dimensional superconductor can be controlled with virtual photons. This could aid the development of new superconductors for energy-saving devices and many other technical applications.

The vacuum is not empty. It may sound like magic to laypeople but it has occupied physicists since the birth of quantum mechanics.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

Expert Panel on the Future of HPC in Engineering

03.12.2018 | Event News

Inaugural "Virtual World Tour" scheduled for december

28.11.2018 | Event News

 
Latest News

A new molecular player involved in T cell activation

07.12.2018 | Life Sciences

High-temperature electronics? That's hot

07.12.2018 | Materials Sciences

Supercomputers without waste heat

07.12.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>