January and February 2000 were mild and very sunny. Precipitation, especially in February, was 40 to 140 % above the monthly mean. Sea surface temperatures in both months were above average. On 8/9 February, stormy westerly winds in the German Bight caused two storm surges with water levels between 1.5 m and 2.5 m above normal.
March was warm and rainy, with few hours of sunshine. The temperatures around 4 - 6 °C were 2 K above the average. The sea surface temperatures accordingly reached above-average values (March: 6.5 °C). In the winter of 1999/2000, the North Sea coastal waters remained ice-free.
In February, near-shore North Sea coastal waters were homothermal and homosaline. The nutrient concentrations measured during a monitoring cruise of RV GAUSS showed the normal seasonal pattern. Related to a salinity of 30, the phosphate concentrations measured in February 2000 (0.91 ± 0.13 µmol/L) in the German Bight approached those measured in 1936(0.56 ± 0.13 µmol/L).
The abundance of plankton in the period from January to March was low, in line with the season. In the North Sylt Wadden Sea, diatoms prevailed (Thalassiosira and Odontella species), and only few flagellate and dinoflagellate species were found. In early March, the first colonies of foam-producing Phaeocystis globosa were observed.
Haddock appears to have a good 1999 year-class. Investigations of herring, whiting, and Norway pout have shown an improvement of stocks.
Petroleum hydrocarbon concentrations (THC) in the German Bight in 1999, at 0.12 - 1.1 µg/L, were of the same order as in the preceding years, indicating a low overall pollution. Hexachlorocyclohexane (HCH) concentrations in 1999 were clearly lower than in the past years. Concentrations of the endocrine disrupting tin organic compounds tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) in the German Bight varied between 0.5 and 8 ng/L. The long-term measuring series of the BSH in the German Bight indicate that concentrations of the heavy metals lead, copper, nickel, zinc, and mercury have been decreasing slowly.
January and February 2000 were mild and very sunny. Precipitation, especially in February, was 40 to 140 % above the monthly mean. Sea surface temperatures in both months were above average.
As in the preceding year, March was up to 2.0 K too warm, with temperatures around 4.3 °C. Precipitation was high. The
high air temperatures led to above-average water temperatures (Wismar Bight, Unterwarnow: deviation <3 K).
Only weak vertical salinity gradients occurred in the Baltic coastal waters of Mecklenburg- Vorpommern in March. Since March 1999, decreasing salinities (0.11 - 0.18) have been recorded in the bottom layers of the Gotland and Faroe Deeps.
The mean sea level in March was considerably above the long-term mean.
In the northern Baltic area, ice formation generally was very weak, ranking last among the winter seasons of the past one hundred years.
In February, nutrients in the surface water between the Kiel Bight and northern Gotland Basin largely showed the normal seasonal levels. Also in late March/early April, nutrient levels in the surface layer of the large basins still reflected winter conditions. The phosphate and ammonium levels in the bottom layers were high. Nitrate concentrations were close to zero. Low nutrient levels as compared to the long-term monthly mean values were found in the coastal waters of Mecklenburg-Vorpommern. In March, elevated nitrate levels were measured in the Pomeranian Bight, Wismar Bight, and Unterwarnow due to riverine inputs in spring. Oxygen levels in the coastal waters of Mecklenburg-Vorpommern, at 10 - 14 mg/L, were good to very good both in the surface and bottom water. Hydrogen sulphide was found in the bottom water at all stations of the Baltic Proper, Faroe Deep and Landsort Deep. Anoxic conditions prevailed below 125 m in the Faroe and Gotland Deeps, below 200 m also in the Landsort Deep.
The low abundance of plankton in the Baltic Sea was typical of the season. At the measuring station "Seebrücke Heiligendamm", cryptophyceae prevailed, as in the preceding years. While diatoms (Skeletonema costatum, Chaetoceros wighamii) became quite abundant toward the end of February, dinoflagellates (Peridiniella catenata) prevailed in early March. This species usually does not develop a spring bloom until April.
At the Danish coast, diatoms (Skeletonema costatum) and the fish-toxic flagellate Chattonella spp. were observed. Although cell concentrations of the latter were elevated, they did not present a risk. In the northern Kattegat and Sound, an increased fluorescence indicated the beginning of the spring bloom.
Investigations showed that the spawning period of cod in 2000 will begin earlier than in the past years.
In the Baltic Sea, the petroleum hydrocarbon levels (THC) measured in 1999 indicated a very low overall pollution. Hexachlorocyclohexane levels (HCH) showed a long-term declining trend which continued also in 1999.