On the stagnation and recent turnover of the water in the Baltic

A short description of the hydrography and water balance of the Baltic is given. The different pycnoclines in the Baltic proper are described. The inflow of salt water through the Danish sounds and the development of stagnant conditions in the deep basins are described. The renewal of the stagnant deep water and the “fertilization” of the surface water with nutrients are discussed.

The oxygen utilization and the accumulation of nutrients through decay of organic matter in the deep water are described. The formation of ammonia, nitrogen and hydrogen sulphide in the stagnant water is briefly explained. The oxygen decrease in the Baltic deep water during the present century and possible reasons to this phenomenon are discussed. The recent stagnation and deep water renewal during 1969 are described by help of figures. The “Baltic Year” programme is described and some results are discussed. The accumulation of phosphate during the stagnation and the spreading of phosphate in the deep water and the “fertilization” of the surface water during the water renewal in 1969 are shown by help of figures.

An increased primary production in the surface water is predicted and a prognosis for the future development of the oxygen conditions in the Baltic is given. It is concluded that Man has increased the oxygen utilization in the deep water by the enormously increased discharge of untreated waste water from industries and communities and that the Baltic therefore has been “overstrained”. Finally it is suggested that measures against future waste discharge have to be taken in order to give the Baltic a chance to recover.