Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Commission research helps identify causes of loss of wildlife in the Baltic Sea in summer 2002

18.09.2003


The dramatic loss of marine wildlife recorded last year in the Western Baltic Sea between Denmark, Germany and Sweden is largely the result of extreme weather conditions and an increase in man-made nutrients, according to the findings of a report recently released by the Helsinki Commission (HELCOM), to which the European Commission provided significant input. Last autumn, the two organisations joined forces to investigate exceptional oxygen depletion in the Western Baltic that had led to hundreds of dead fish being washed ashore along the east coast of Jutland, Denmark. The report reveals that the oxygen deficiency was caused in part by heavy rain and snow, leading to the run off of higher levels of nutrients from agriculture, urban wastewater and air pollution into the sea. In addition, low wind levels and high air pressure minimised exchanges between different water levels in the Baltic. The report recommends stricter controls on nutrients reaching this inland sea to prevent future oxygen depletion.



Research Commissioner Philippe Busquin said: “We must do more to reduce the level of man-made nutrients polluting the Baltic Sea and the destruction of its precious ecology. We cannot ignore nature’s alarm calls, and must ensure that our research findings help shape appropriate international policies.”

A preliminary version of the report was used in the preparatory work for the HELCOM Ministerial Meeting, which took place on 25th June 2003 in Bremen. Environment Commissioner Margot Wallström participated at this meeting on behalf of the European Commission. A wide-ranging package of measures for the protection of the Baltic marine environment was agreed upon by the Ministers. With regard to combating eutrophication , this package included the following agreements to:

  • make agriculture more environmentally sustainable;
  • ensure that EU directives such as the Nitrate and Urban Waste Water Directives are fully implemented;

  • improve agricultural practices to ensure efficient use of nutrients while minimising any adverse impact on the environment;
  • reduce pollution by nutrients from other sources.

Tackling a wildlife disaster

Widespread and long lasting severe oxygen depletion was observed in the Kattegat, the Sound and the Baltic Sea in late summer and autumn 2002 – amongst the worst ever recorded. In several areas, extreme oxygen deficiency led to the release of highly toxic hydrogen sulphide from marine sediments. As a result, creatures living near to the bottom of the sea died and, in October 2002, a large amount of dead marine wildlife was washed up on the Jutland coast.

Following the initiative of the HELCOM Monitoring and Assessment (MONAS) Group, an expert group was set up with Denmark, Germany, Sweden and the European Commission to analyse the development and causes of this worrying situation.

Eutrophication is still a major problem in the Baltic Sea. The symptomatic problems of eutrophication – serious oxygen deficiency, extensive algal blooms and floating mats of decaying seaweed in coastal waters – remain all too common, in spite of substantial efforts to reduce nutrient inputs over a wide area. In the EU as well, intensive agricultural methods make farmland a major source of waterborne nutrient pollution.

Analysis of the development and causes of the 2002 oxygen depletion required expertise from several disciplines, including marine biology, oceanography and satellite remote monitoring. The experts formed a Working Group to seek explanations and recommendations for decision-makers.

Identifying the cause


Comparisons between recent years marked by specific weather events in the area revealed the key roles of snow, rain, and wind and air pressure in the oxygen balance of marine bottom waters. The amount of snow and rain largely controls the nutrient loading of surrounding rivers by soil erosion. Unseasonably late rains, combined with sunlight can also indirectly enhance marine plant production in surface waters. Wind and air pressure acts on the local supply of oxygen through water exchanges with the oxygen-rich waters of the Skagerrak.

Field measurements show that in 2002 there was a higher nutrient discharge in the Baltic Sea in June and July as a result of above average rainfall. Microalgae biomass, measured by both traditional means and satellite remote sensing, showed slightly higher levels in July compared with previous years. However, 1999 levels were substantially higher than 2002, yet oxygen conditions were better.

Comparable results from three independent hydrological models (Denmark, Sweden and the Commission) provided the main explanation for particular sensitivity to oxygen consumption in 2002. August was marked by almost no water exchange at the bottom of the sea, between the Skagerak (oxygen-rich) and the Belt Sea area (oxygen-poor), and there was substantially lower inflow than usual in July and from September to November. Deep bottom oxygen depletion (at 15 to 60 metres) resulted from this particular low water exchange, the latter controlled mainly by wind and air pressure above the North and Baltic Seas. In addition, unusually low winds severely limited mixing in surface waters (down to 15 metres) and were responsible for oxygen deficiencies at shallow levels.

Reduced nutrient levels essential

While weather conditions were the main trigger of the 2002 event, investigations revealed that the Baltic Sea is particularly vulnerable to oxygen depletion. Permanent separation of water strata, minimal reaction with the sea bottom, restricted flow patterns resulting from semi-enclosed bays and estuaries and shallow bowl shapes in the sea bottom all favour the isolation of bottom water masses and therefore limit reoxygenation.

The Baltic Sea region is one of the most naturally sensitive to oxygen deficiency in Europe. Some confined regions – such as the Little Belt – were already experiencing oxygen deficiencies 100 years ago, when nutrient discharges were relatively low. For several decades the main original cause of extended oxygen deficiency has been the nutrient supply in surface marine waters.

The Commission contribution indicates that the Belt Sea area has a very limited capacity to digest the organic matter and, indirectly, to assimilate any additional supply of nutrients. Further efforts are necessary to meet the 50% nutrient reduction target set by HELCOM. But even this might turn out to be insufficient to drastically reduce the likelihood of severe oxygen depletion in terms of geographical coverage and duration in the Western Baltic.

Fabio Fabbi | European Commission
Further information:
http://www.dmu.dk/1_om_dmu/2_afdelinger/3_hav/oxdep2002/default.asp
http://ies.jrc.cec.eu.int/Units/imw/
http://www.helcom.fi/

More articles from Ecology, The Environment and Conservation:

nachricht Preservation of floodplains is flood protection
27.09.2017 | Technische Universität München

nachricht Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen

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: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

Im Focus: New nanomaterial can extract hydrogen fuel from seawater

Hybrid material converts more sunlight and can weather seawater's harsh conditions

It's possible to produce hydrogen to power fuel cells by extracting the gas from seawater, but the electricity required to do it makes the process costly. UCF...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Study suggests oysters offer hot spot for reducing nutrient pollution

17.10.2017 | Life Sciences

Breaking: the first light from two neutron stars merging

17.10.2017 | Physics and Astronomy

World first for reading digitally encoded synthetic molecules

17.10.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>