MURSYS - North Sea and Baltic Sea - Report 4 2002





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MURSYS - North Sea and Baltic Sea - Report 4 2002

   
 
 

Marine Environmental Reporting System - Abstract - Reporting Period: 1 October - 31 December 2002

 

North Sea

Weather

October was 1 - 2 K too cold, at mean temperatures of 8 - 9 °C on the coasts and 10.3 °C at Helgoland. Heavy rainfalls caused 50 - 100 % exceedance of the reference values. The 90 - 110 hours of sunshine in October were close to the monthly mean. The cyclone "Jeanett" brought hurricane-force squalls and had a death toll of nearly 30 in Europe.
November, too, was too cold. A monthly mean temperature of about 6 °C was recorded on the coasts. Precipitation ranged between 65 and 100 mm (70 - 90 % of the monthly mean), and only 30 - 40 hours of sunshine were recorded (50 - 80 % of the reference values).
In December, mean temperatures in the coastal area were 0 - 1 °C (2 - 2.5 K below the reference values). 15 - 20 days with frost and 5 - 14 days with ice were recorded. Precipitation, at 30 - 50 mm, was only 50 - 65 % of the monthly mean. The duration of sunshine, at 40 - 55 hours, was 10 - 20 % above normal.

Water temperatures

The mean water temperatures in the North Sea were above the climatological mean: in October 13.1 °C, November 10.1 °C, December 7.9 °C.

Salinity

In November, salinity in the North Sea at Nordseeboje II station was about 34.0 at 6 m depth.

Phytoplankton (Helgoland)

In early October, diatoms were less abundant but still species-rich. Compared to the preceding month, the total number and abundance of flagellates had hardly changed. Phytoplankton stocks were unchanged but included a higher proportion of diatoms. The biomass of flagellates decreased, and there were fewer small species than the week before. Odontella sinensis still was the dominant diatom species. By mid-October, phytoplankton stocks had dropped to a very low level. Odontella sinensis continued to be the dominant diatom species. Also cell concentrations of flagellates were lower than the week before. At the end of October, phytoplankton stocks had dropped to their low winter level.

Mass mortality of seals in the North Sea and Baltic

From May through mid-October, a total of 19,470 dead seals (Phoca vitulina) were counted in the Kattegat and Skagerrak, Wadden Sea, and North Sea (status of 16 October 2002). Examinations in the Netherlands, Denmark, Sweden, and Germany led to the identification of the phocine distemper virus (PDV) as the cause of the epidemic. On 26. Sept. 2002, the marine biological laboratory at Tjärnö (Sweden) declared the end of the seal epidemic in the Skagerrak and Kattegat.
In the Wadden Sea of the Netherlands, 2,141 dead seals had been counted since mid-June (status: 14 Oct. 2002).
In the Schleswig-Holstein Wadden Sea, the number of dead seals stagnated from the second week of October. 2,676 dead animals had been reported since 26 August (status: 14 Oct. 2002).
England reported 288 dead seals between 9 and 15 October. This raised the total number since the beginning of the epidemic to 2,653 (status: 16 Oct. 2002). The phocine distemper virus was identified in 34 cases. In November 2002, about 21,000 dead seals (Phoca vitulina) were reported in the North Sea and Baltic (status: 1 November 2002). Numerous examinations proved that PDV had caused the epidemic. Besides, bacterial (Bordetella bronchiseptica) and parasitic infections were found which had also caused pneumonia in the animals. In Denmark, Sweden, and Norway, the PDV epidemic seems to have come to an end. In the period from 24 to 30 October, the number of dead seals found on the coasts of Schleswig-Holstein increased again slightly. The stormy weather left sick animals and many older carcasses on the beaches.
Between May and December, a total of about 22,050 dead seals (Phoca vitulina) were reported in the North Sea and Baltic (status: 6 December 2002).
In the UK and northern Ireland, the number of dead seals continued to increase.

Ice conditions

In mid-December, thin new ice was reported in the Wadden Sea, on the river Ems, and on the Elbe upstream of Glückstadt.

Baltic Sea

Weather

October was sunny at first, but a change toward autumnal weather occurred in the second half of the month. Mean temperatures ranged from 8 to 9 °C, which made the month 1.0 - 1.6 K too cold. Abundant rainfall was reported especially in the second half of the month, at 75 - 90 mm, which was nearly twice the normal precipitation. Despite the sunny spell at the beginning of the month, the duration of sunshine in October was 10 - 30 % below normal, at 76 to 96 hours. On 27 and 28 October, the cyclone "Jeanett" brought hurricane-force squalls and had a death toll of nearly 30 in Europe.
Also November was too cold, at mean temperatures between 3.7 and 5.6 °C. Precipitation was mostly between 60 and 80 mm and exceeded the reference values by up to 60 %. The duration of sunshine was 40 - 50 hours, which was about 10 - 30 % below normal.
The end of the year was too cold and dry, with much sunshine. The monthly mean temperatures in December ranged between 0 °C at the western Baltic coast and -2.3 °C at the coast of Mecklenburg-Vorpommern. They were 1 - 3 K below the reference values. Freezing temperatures were recorded in all nights from 8 to 26 December. Precipitation, at 10 - 13 mm, was only 20 - 30 % of the monthly mean. The sun shone between 39 hours (Fehmarn) and 57 hours (Stettin Lagoon), exceeding the mean values by up to 50 %.

Water temperatures

In October, the mean water temperatures in the Baltic were 12.7 °C in Warnemünde and 11.2 °C in Koserow, in November 7.3 °C in Warnemünde and 6.8 °C in Koserow, in December 3.8 °C in Warnemünde and 2.6 °C in Koserow.

Salinity

In late October/early November, salinity at the Fehmarn Belt station fluctuated between 17 and 20 at 6 m depth.

Phytoplankton (coastal waters of Mecklenburg-Vorpommern)

In October, more or less unchanged chlorophyll-a concentrations were measured in the outer coastal waters. The cause of higher phytoplankton concentrations at the station east of Sassnitz was the spreading of large Coscinodiscus species which were observed along the entire outer Baltic coast and dominated the autumnal phytoplankton, although at low abundances.

In October, the spatial distribution of chlorophyll-a concentrations in the inner coastal waters was similar to the month before. Concentrations ranged between 3.3 µg/litre (Salzhaff) and 123 µg/litre (Darß-Zingst bodden waters). Higher concentrations than the long-term mean were also measured in the Lower Warnow (UW4), at 9.4 µg/litre. In the Stettin Lagoon, Coscinodiscus rothii was the prevailing autumnal phytoplankton species, at 1.9 mm³/litre.

Ice conditions

The Baltic ice winter of 2002 began about three weeks earlier than usual. On the northern coast of the Bay of Bothnia, first ice formed in the inner skerries in early November, and in the inner Bay of Kronstadt at the beginning of the 46th week. In the Finnish harbours of Tornio, Kerni, and Oulu, the first restrictions to navigation became effective on 19 November. In the week of 18 - 24 November, with mostly moderate frost, the ice thickness increased on the north coast of the Bay of Bothnia. A 10 - 25 cm thick belt of fast ice developed in the skerries. In the second week of December, ice formation began in the inner bodden waters of the German coast. By mid-December, most of the inner bodden waters had a 5 - 15 cm thick ice cover.

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