MURSYS - North Sea and Baltic Sea - Report 4 1997





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MURSYS - North Sea and Baltic Sea - Report 4 1997

   
 
 

Marine Environmental Reporting System - Abstract - Reporting Period: 1 September - 30 November 1997

 

September 1997 was extraordinarily warm, at air temperaturesbetween 14.0 and 15.5 °C. Compared to long-term mean values, October and November were up to 1.5 K below the long-term mean temperatures. All three months covered by the report were too dry.

Sea surface temperatures during this period were above the climatological mean values (1971 - 93). In the eastern Gotland Basin, hydrogen sulfide was found below 130 m. Anoxic areas had spread in this basin since August.

North Sea

On the coasts of Lower-Saxony, plankton samples in September showed a mode-rate concentration of diatoms. Flagellates in the plankton were dominated by dinoflagellates. Colonies of the foam-forming Phaeocystis and light-emitting Noctiluca algae occurred only sporadically. With falling water temperatures in October and November, the abundance of plankton decreased as well. Potentially toxic species of the genus Dinophysis were found at the stations Osterems, Jade, and Harle. In the North Sylt Wadden Sea, rod-shaped plankton dominated by the species Rhizosolenia imbricata was frequent, with mass development in some places. On the west coast of Schleswig-Holstein, a marked increase in the range of species was observed in the two large groups of diatoms and dinoflagellates in September. In the following months, falling water temperatures caused a decrease in the algal population.

Baltic Sea

In the September plankton in the near-shore area of the Arkona Sea, the blue-green algae Nodularia spumigena and Anabaena spp. continued to be present. Dinophyceae were present from late September to early October. From mid-October, the overall plankton concentration was conspicuously low.

In September large-scale blooms of blue-green algae did not occur any more in the northern Baltic Sea.

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