60
u40
OJ
::J..
20.
0.9
dt 0.. 0..7
(5
5. 0..5
Fig. 12. In the Bay of Helgoland (German North Sea) the trend to eutrophication seems to be
predominant. Regular measurements of the phosphorus in the seawater near Helgoland show an
increase in the yearly average from approximately 0.5 ILmol/1 in 1962 to approximately 0.9 ILmol/1
in 1976 (lower diagram). Note that the amounts vary greatly from year to year and depend very
strongly on the amounts of freshwater that are transported into the German Bight by the Elbe
and Weser Rivers. In years of heavy rainfall, the average salinity is lower and the average phosphate
concentration higher. Even stronger are the annual variations of the average phytoplankton-biomass (in ILg carbon/I, upper diagram). The regression line is not significant; it is therefore doubtful
whether an increase of the phytoplankton has actually occurred in the German Bight (Hagmeier
1978; according to a personal communication)
There is definite hope that eutrophication of coastal waters by phosphates will
decrease in the coming years. At present, 40% of the phosphate load in rivers of the
Federal Republic of Germany originates from phosphate in washing powder, the
component that softens the water by binding calcium. For a number of years it has
been well known that zeolites have the same softening effect in washing powder, and
they are nontoxic sodium-aluminum-silicates which do not cause eutrophication.
Zeolites are minerals with a peculiar cristal structure; they work like ion exchange
devices and take up calcium, heavy metals, and other substances from solutions.
When incorporated in the zeolites, these substances are particulate and settle down in
the sediment. Zeolites occur naturally as a product of vulcanism, and they can be
produced by the chemical industry. At present, a plant for the production of 65,000 t
of zeolites per year is under construction close to Cologne, and the government of
the Federal Republic of Germany issued a regulation which reduces the permissable
amount of phosphates in washing powder to 50% before 1984 (Anon 1980a).
2.4 The Situation in the Baltic
Mixed with some seawater, freshwater from the numerous rivers that flow into the
Baltic moves on the surface of the Baltic to the Skagerak. This brackish water covers
the saltier deep water like a blanket (Figs. 13 and 14). Because of this, all effective
contact between the deep water and the atmosphere is prevented. Only a certain small
degree of transportation of oxygen to the deep water takes place by means of diffusion and downwelling.
20
u40
OJ
::J..
20.
0.9
dt 0.. 0..7
(5
5. 0..5
Fig. 12. In the Bay of Helgoland (German North Sea) the trend to eutrophication seems to be
predominant. Regular measurements of the phosphorus in the seawater near Helgoland show an
increase in the yearly average from approximately 0.5 ILmol/1 in 1962 to approximately 0.9 ILmol/1
in 1976 (lower diagram). Note that the amounts vary greatly from year to year and depend very
strongly on the amounts of freshwater that are transported into the German Bight by the Elbe
and Weser Rivers. In years of heavy rainfall, the average salinity is lower and the average phosphate
concentration higher. Even stronger are the annual variations of the average phytoplankton-biomass (in ILg carbon/I, upper diagram). The regression line is not significant; it is therefore doubtful
whether an increase of the phytoplankton has actually occurred in the German Bight (Hagmeier
1978; according to a personal communication)
There is definite hope that eutrophication of coastal waters by phosphates will
decrease in the coming years. At present, 40% of the phosphate load in rivers of the
Federal Republic of Germany originates from phosphate in washing powder, the
component that softens the water by binding calcium. For a number of years it has
been well known that zeolites have the same softening effect in washing powder, and
they are nontoxic sodium-aluminum-silicates which do not cause eutrophication.
Zeolites are minerals with a peculiar cristal structure; they work like ion exchange
devices and take up calcium, heavy metals, and other substances from solutions.
When incorporated in the zeolites, these substances are particulate and settle down in
the sediment. Zeolites occur naturally as a product of vulcanism, and they can be
produced by the chemical industry. At present, a plant for the production of 65,000 t
of zeolites per year is under construction close to Cologne, and the government of
the Federal Republic of Germany issued a regulation which reduces the permissable
amount of phosphates in washing powder to 50% before 1984 (Anon 1980a).
2.4 The Situation in the Baltic
Mixed with some seawater, freshwater from the numerous rivers that flow into the
Baltic moves on the surface of the Baltic to the Skagerak. This brackish water covers
the saltier deep water like a blanket (Figs. 13 and 14). Because of this, all effective
contact between the deep water and the atmosphere is prevented. Only a certain small
degree of transportation of oxygen to the deep water takes place by means of diffusion and downwelling.
20