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In 1998, temperatures were higher than usual, although sunshine hours
were below the long-term mean (1961-1990). In addition it was clearly too
wet. During the warming-period water temperatures were 0,5 - 2 K higher,
from July to the end of 1998 they were lower than in
1997.
North Sea:
In 1998, Phaeocystis globosa algae occurred
around the island of Norderney, while they had not been observed during the
past two years. Due to the cool summer, phytoplankton growth was low.
In May the fish toxic algae Chattonella developed to a bloom
which caused fish kills in Danish and Norwegian waters.
Sprat stocks were observed at a low level. The year-class 1998
of cod, plaice and dab was low.
The seal population in the Schleswig-Holstein Wadden Sea had continued
to grow.
At the end of October, a bulkcarrier run aground near Amrum. About
50 tons of Diesel oil and heavy fuel oil contaminated the Wadden Sea. The
number of birds killed by the oil pollution was estimated at 15 000 ones.
Most organic contaminant concentrations measured within the regular
monitoring programme lay in the same range as the years before. Since
1982 a clear decrease of alpha-HCH is noticed, an even longer
decline of gamma-HCH was registered. In sediments of the inner German
Bight, concentrations for cadmium, copper and zinc were observed
declining as well as for mercury and lead.
Baltic Sea:
No remarkable inflow of salt water was
registered in 1998. The decrease of oxygen concentrations in
the deep water of the central Baltic Sea indicated continuation of stagnation.
From May onward, toxic hydrogen sulphide was measured in the
Bornholm Basin and since June, in the eastern Gotland Basin. Over
the last years a decrease of winter concentrations of anorganic
nutrients was observed in the central and western Baltic Sea.
In Baltic waters no exceptional phytoplankton bloom was observed.
The development of the dinoflagellates was unusually sparse; the development
of diatoms was very high. Large scale blooms of blue-green algae did not
occur in summer 1998.
In the Gulf of Finland the common jellyfish Aurelia aurita formed mass
concentrations in August and September 1998.
In the Odra bank area, flounder showed a good recruitment, with a
strong year-class 1996. There are first indications for a strong
herring year-class 1998. Turbot and plaice stocks were
not satisfactory. The cod year-class 1997 did not comply with the
expected results. The occurrence of 0-year-class of pike-perch and
perch was appraised below average.
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