Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Environmental history told by sludge: Global warming lets the dead zones in the Black Sea grow


Geoscientists from the Warnemünde Leibniz Institute for Baltic Sea Research, the universities of Oldenburg and Hannover as well as the Rutgers University (USA) succeeded now in reconstructing the depositional environment of the last interglacial (Eemian, 128,000 years ago) in the Black Sea with unprecedented details. This enabled for the first time a direct comparison between the current oxygen-depleted conditions in the deep water with those during the Eemian when the water temperatures in summer were 3° higher. It shows that the dead zones of the Black Sea will most probably expand by a future global warming leading to a significant shrinking of the productive zone in the surface water.

Oxygen deficiency together with the occurrence of toxic hydrogen sulphide below water depths of 100 – 150 m are the most prominent features of the Black Sea, the world´s largest brackish basin. Today, up to 90 % of the Black Sea water body is a harsh and hostile oxygen-free environment where no higher life can survive.

Dark sediments represent „dead zones“ during warm periods like Eemian and Holocene. The warmer Eemian might serve as a bench mark for a potential future climate.

It is critical to understand how these dead zones will develop in response to the ongoing global warming and sea level rise. The detailed analyses of sediments from the last interglacial (Eemian) in the Black Sea, recently published in the international journal “Palaeogeography, Palaeoclimatology, Palaeoecology“ offer insights into a potential future.

Oxygen depletion in the bottom waters of the Black Sea causes a decelerated decomposition of the organic matter sinking to the seafloor. These organic-rich muds form the so-called sapropels that are quite common among both recent and Eemian deposits.

By means of detailed analyses of redox-sensitive chemical elements in these sapropels, the team succeeded in reconstructing a differentiated picture of the deep-water conditions during the Holocene and Eemian periods in the Black Sea.

As environmental witnesses (so-called proxies) the geoscientists used, for example, the trace elements molybdenum and rhenium, which react differently and specifically on oxygen deficiency and the presence of sulphide. In total, the analysis of more than 10 of such proxies enabled the reconstruction of a complex picture.

IOW geologist Antje Wegwerth summarizes the results: ”During the Eemian period the deep water of the Black Sea showed a significantly higher concentration of sulphide and, thus, was more toxic than today. The hostile conditions expanded over thousands of years and finally reached the so called photic zone, the highly productive surface water layer exposed to light.”

In such a resolution and quality, no Eemian sediments have been investigated so far, because these deep lying deposits are normally accessible only by expensive deep-sea drillings. However, during a cruise on R/V METEOR sediments from both Holocene and Eemian periods could be retrieved by conventional gravity coring from a prominent bathymetric ridge structure. Thus, the direct comparison of both interglacials became possible.

Postglacial warming during the Eemian and the Holocene caused significant changes in the Black Sea. The large polar ice sheets disappeared, the global sea level rose, and once flooding the shallow Bosporus sill, the salty and dense water masses of the Mediterranean Sea intruded the formerly Black Sea “Lake”. This led to a strong stratification with saline deep waters below the brackish surface waters.

At the same time, elevated sea surface temperatures resulted in an increased productivity and flux of organic matter, ultimately exhausting oxygen in the basin during its decomposition. The interaction of these processes finally lead to the generation of enormous “dead zones” in the Black Sea.

Wegwerth, A., Eckert, S., Dellwig, O., Schnetger, B., Severmann, S., Weyer, S., Brüske, A., Kaiser, J., Köster, J., Arz, H.W., Brumsack, H.-J. Redox evolution during Eemian and Holocene sapropel formation in the Black Sea. Palaeogeography, Palaeoclimatology, Palaeoecology (2018) 489, 249-260

Scientific expert:
Dr. Antje Wegwerth, +49 381 5197 3481,

Press and public relation:
Dr. Barbara Hentzsch | +49 381 5197-102 |

IOW is a member of the Leibniz Association with currently 91 research institutes and scientific infrastructure facilities. The focus of the Leibniz Institutes ranges from natural, engineering and environmental sciences to economic, social and space sciences as well as to the humanities. The institutes are jointly financed at the state and national levels. The Leibniz Institutes employ a total of 18.100 people, of whom 9.200 are scientists. The total budget of the institutes is 1.6 billion Euros. (

Dr. Barbara Hentzsch | idw - Informationsdienst Wissenschaft

Further reports about: Black Sea Holocene Ostseeforschung dead zones sapropels sea level sediments sulphide

More articles from Earth Sciences:

nachricht Massive impact crater from a kilometer-wide iron meteorite discovered in Greenland
15.11.2018 | Faculty of Science - University of Copenhagen

nachricht The unintended consequences of dams and reservoirs
14.11.2018 | Uppsala University

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: UNH scientists help provide first-ever views of elusive energy explosion

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

Latest News

Purdue cancer identity technology makes it easier to find a tumor's 'address'

16.11.2018 | Health and Medicine

Good preparation is half the digestion

16.11.2018 | Life Sciences

Microscope measures muscle weakness

16.11.2018 | Life Sciences

Science & Research
Overview of more VideoLinks >>>