Oxygen situation in Gulf of Finland improved

Mild winters boost oxygen content

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Many boaters and bathers have noticed that the water in the Gulf of Finland is slightly clearer this summer, and there is less algae than before.
      The observations bear witness to the fact that the Gulf of Finland is in better shape now than it has been in years. The situation is the best that it has been at any time since 1999.
      Experts on the research vessel Muikku, which surveyed the Gulf of Finland in August, noticed that the oxygen content of the water has improved in many locations. A third of the locations were without oxygen, down from more than 80 per cent in 2006.
     
The main reason for the positive development was the weather. The mild winters of recent years and the lack of a lengthy period of ice cover on the sea have allowed the water of the Gulf of Finland to be more thoroughly mixed, bringing oxygen even to deeper layers. If there is no mixing of the layers in the water, oxygen is eventually depleted at the bottom.
      Also easing the situation has been the fact that large amounts of low-oxygen water have not flowed into the Gulf of Finland from the main basin of the Baltic.
      There is cautious optimism at the Finnish Environment Institute that the improved situation of the Gulf of Finland might continue.
      “At best, the state of the Gulf of Finland could get more impetus as measures taken in sewage treatment in St. Petersburg move forward”, says limnologist Seppo Knuuttila, the director of the most recent voyage of the Muikku.
     
The oxygenated water has helped the sediments on the bottom of the sea to tie down phosphorous. As the phosphorous content of the water decreases, algae growth is hindered. Consequently, the researchers noticed that there was less algae than before.
      “The amount of algae in the summer was about half of what it was in 2004", Knuuttila calculates.
      Oxygen also makes animal life possible on the sea bottom. Fauna was found at the bottom in nearly all locations under observation, whereas most had shown no life in previous years.
      The first creature to appear on the bottom was the Marenzelleria viridis. Although the worm is an invasive species of North American origin, Knuuttila does not consider it to be harmful.
      “The return of bottom fauna is much more important. Fish are just as able to use this species for nutrition as any other.”
     
There are still problems in the Gulf of Finland. The oxygen system in the open sea areas of the western part of the gulf has not improved, and in the Inkoo Archipelago, for instance, there are areas that are completely oxygen-free.
      Things also look bad outside the Gulf of Finland, in the main basin of the Baltic Sea.
      The research vessel Aranda, which sailed to the area near the Swedish island of Gotland, noticed that the area of oxygen-free water at the bottom with high levels of hydrogen sulphide had grown wider and thicker.


Previously in HS International Edition:
  Improvements seen in sea bottom in Finnish coastal areas (25.8.2008)
  Baltic Sea needs urgent attention (14.4.2008)
  Progressively tighter emission standards for ships on Baltic Sea (9.4.2008)
  Research vessel Aranda to chart distribution of comb jellies in Baltic Sea (5.8.2008)

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