MURSYS - North Sea and Baltic Sea - Report 1 2002





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MURSYS - North Sea and Baltic Sea - Report 1 2002

   
 
 

Marine Environmental Reporting System - Abstract - Reporting Period: 1 January - 31 March 2002

 

North Sea

Weather

January was considerably too mild (mean temperatures: 3 - 4 °C), with average rainfall (55 - 70 mm) and 45 to 55 hours of sunshine.
An unusually mild (mean temperatures: 5.0 - 6.5 °C) and wet (100 - 120 mm precipitation) February was followed by a dry March (20 - 40 mm precipitation) with more sun than usual (140 - 150 hours), which was slightly too mild (mean temperatures: 5.0 - 6.5 °C).

Water temperatures

The mean water temperatures in all four months were above the climatological values (January: 7.0 °C, February: 7.2 °C, March: 6.9 °C, April: 7.8 °C).

Ice conditions

At the North Frisian coast, thin local drift ice occurred only on 6/7 January.

Phytoplankton

From the end of March, cell concentrations of the large diatom Odontella sinensis increased near Norderney, reaching over 2000 cells/litre in the third decade of April.
Off Helgoland, numerous small and medium-sized dinoflagellates and ciliates were abundant at the end of March. Dip nets showed high concentrations of large diatoms (Coscinodiscus wailesii and C. concinnus).

In the North Sylt Wadden Sea, a high diversity of plankton species dominated by diatoms (Thalassiosira and Odontella) was present during the winter months. An early bloom was not observed.

Fish

Stocks of bottom-living fishes in the German Bight have deteriorated further. Two-year and older cod were hardly caught, plaice were absent from the coastal waters, and dab were found only in a small area west of Helgoland.

Baltic Sea

Weather

January had mean temperatures around 2 - 3 °C and was too warm and wet (35 - 60 mm rainfall), with little sunshine. February was extraordinarily wet (50 - 120 mm rainfall), clearly too mild (4.3 - 5.5 °C), with much sun (80 - 105 hours) and wind. The monthly mean temperatures in March were hardly different from those in February, but precipitation was considerably lower (15 - just under 50 mm). At the beginning of spring, a stable high pressure situation developed which lasted into the first decade of April.

Water temperatures

In the coastal waters of Mecklenburg-Vorpommern, negative departures from normal were recorded in January. Positive departures were observed in February, which increased in March. Bottom water showed the same trend. Stratification did not yet occur.

Salinity

Salinities in the coastal waters of Mecklenburg-Vorpommern were slightly sub-normal both in January and February. Measurement values in March showed no uniform pattern.

Water levels

While average water levels were measured in January, the monthly mean values in February were up to 23 cm above the reference series. On 21 February, the heaviest of seven storm surges since November 2001 was recorded. Water levels in March were 29 cm above the reference values.

Ice conditions

In the northern Baltic, the ice season began around 6 November 2001, about one week earlier than usual. The ice extent around 20 January 2002 was comparable to the average long-term ice conditions. Because of unusually mild weather in the northern Baltic since the beginning of the year, the 2001/2002 ice season ended as a weak ice winter, as in the preceding year.
The ice winter on the German coasts was also weak. Appreciable local ice formation occurred only during the cold spells in late December and early January.

Phytoplankton

At the monitoring station "Seebrücke Heiligendamm", primarily crypto-flagellates (Teleaulax sp.) were found during the winter period.
A strong growth of Mesodinium rubrum in mid-March was followed by the typical diatom spring bloom (Chaetoceros species, Rhizosolenia setigera, Thalassiosira anguste-lineata). In the second half of March, this bloom was replaced by Skeletonema costatum, which typically marks the late phase of the diatom bloom. On 9 April, it was followed by a mass development of athecate dinoflagellates (Gymnodinium cf. lohmannii). Mesodinium rubrum developed parallel to this population change. Also the occurrence of the Chrysophycea Pseudopedinella is worth mentioning.

In the outer coastal waters of Mecklenburg-Vorpommern, the typical winter minimum was observed in January/February. Nevertheless, chlorophyll-a values 3 to 4 times higher than usual were measured in the waters north of Boltenhagen in an area extending towards Darss Sill.
Also in the inner coastal waters, the usual values were clearly exceeded locally. As in the preceding year, the cryptoflagellates Teleaulax acuta and Plagioselmis prolonga were dominant besides Skeletonema costatum.
While in March the spring algal development ended in the western sea areas, a spring bloom developed in the eastern areas. The dominant species were diatoms such as Skeletonema costatum and Fragilaria ulna and cryptoflagellates like Teleaulax acuta and Plagioselmis species. In the Wismar Bight, only 15 % of the long-term average chlorophyll concentration was measured. In the Firth of Stettin, Teleaulax acuta continued to form a monoculture, and in the sea area of Strelasund Sound/Greifswald Lagoon, Skeletonema costatum was dominant.

Fish

A survey of fish stocks in February/March confirmed the poor condition of commercial-sized cod stocks in the southwestern Baltic. Compared to the spring of 2001, however, the recruitment situation has improved both in the Mecklenburg Bight and in the Arkona Sea.
In the fisheries areas Kattegat, Kiel Bight, and Bornholm Sea, cod catches on a catch-per-hour basis were at last year's level.

Nutrients

At the coast of Mecklenburg-Vorpommern, phosphate and nitrate concentrations in January and February were farther below the long-term monthly mean than in 2001. However, extreme rainfall, especially in February, led to considerably higher nitrate concentrations in the Lower Warnow and Odra estuary (up to 370 µmol N/litre).
In March, phosphate in the outer coastal waters was about one third lower, with even lower values in the inner coastal waters. Nitrate concentrations showed marked local differences.
In the western Baltic, nutrient concentrations at the beginning of the year differed hardly from the long-term means. The nutrient situation in the bottom water layers reflected the oxygen situation.

Oxygen

Oxygen concentrations in the first few months of the year were normal in the coastal waters of Mecklenburg-Vorpommern.
Several minor inflows of saline water in October and November 2001 transported oxygen-rich, high-salinity water into the Baltic, causing complete oxidation of hydrogen sulphide in the Bornholm Basin. In the eastern Gotland Basin, H2S levels at the beginning of the year were low. However, this situation was of short duration.

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