Winter storms improve oxygen situation at bottom of Gulf of Finland

There has been a considerable increase in the oxygen content of the water at the bottom of the Gulf of Finland. The higher oxygen levels in the small body of water are attributed to powerful storms in the late autumn and winter that have helped mix up the layers of the gulf.
      According to the results of a three-week voyage by the marine research vessel Aranda, there has been little change in the northern Baltic and in the main basin of the Baltic Sea.
      The layers of the Gulf of Finland have undergone a thorough upheaval, except for areas nearest the shore. The oxygen level at the bottom of the gulf had been at a record low after last summer, but now it is good again. The salinity of the depths of the Gulf of Finland has also declined considerably.
     
The Aranda was not granted permission by Russian authorities to take samples at the eastern end of the Gulf of Finland, which is considered the most difficult part. Therefore, it was not possible to see if a new sewage treatment plant in St. Petersburg has had a positive impact, even though Finland and the other Nordic Countries took part in the financing of the project.
      In the northern part of the Baltic, oxygen levels continue to be high, and nutrients remain at the same low levels that they had been in previous years.
      The water temperatures were also at record highs for this time of the year in many areas.
     
Oxygen depletion at the bottom of the main basin of the Baltic Sea was approximately as extensive as it was last year. Not even the powerful storms of the winter have managed to mix the water in the way that has taken place in the Gulf of Finland.
      However, hydrogen sulphide levels were lower than last year.
      In spite of the winter storms, there have been no oxygen-rich saline pulses from the North Sea this winter.
      The Baltic currently contains so much water, that pulses of salty water have not managed to surge into the Baltic through the shallow Straits of Denmark and Öresund.
      Saline pulses take place 10 to 15 times in a century in situations in which the water volume in the Baltic is lower than usual, just before strong and continuous southwesterly storms, which push salty water rich in oxygen into the brackish waters of the Baltic. The last time that a powerful saline pulse occurred was in 1993.


Previously in HS International Edition:
  Gulf of Finland in record-poor shape; bottom is dead and oxygen low in many areas (18.8.2006)
  Bottom of Gulf of Finland remains in poor condition (22.8.2005)
  Weekend winter storm may improve water quality in Gulf of Finland (12.1.2005)
  Gulf of Finland still in bad shape (23.8.2004)
  Removal of phosphorous from St Petersburg waste water to begin next year (11.10.2005)
  Water quality in Gulf of Finland deteriorates alarmingly from last year (11.8.2003)
  Expedition detects little life at bottom of Gulf of Finland (9.6.2003)
  No algae problem on St. Petersburg beaches despite massive sewage emissions (29.7.2002)