MURSYS - North Sea and Baltic Sea - Report 1 2005





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MURSYS - North Sea and Baltic Sea - Report 1 2005

   
 
 

Marine Environmental Reporting System - Abstract - Reporting Period: 1 January - 30 June 2005

 

North Sea

Weather

January 2005 in the North Sea area was characterised by very mild weather in the first half of the month. At monthly mean temperatures between 4.5 and 5 °C, it was about 3.5 K too mild. Precipitation was mostly below average. On the North Sea islands, for example, only 50 - 60 % of average precipitation was reached, at 30 - 35 mm. Above-average precipitation of 55 - 70 mm was only recorded in areas east of the Weser estuary. In spite of frequent stormy weather, the duration of sunshine was 25 - 50 % above average, at 50 - 70 hours.
In February, the monthly mean temperatures of 1 - 2 °C were on the order of the 1961 - 1990 mean values. Precipitation, at 30 - 45 mm, was ±10 % above or below the mean values. Also this month's 65 - 93 hours of sunshine mostly corresponded to the mean values, at ±10 %. A 30 % surplus was recorded only on Schleswig-Holstein's islands and coasts.
Also the mean temperatures of 2.5 - 4.5 °C in March were on the order of the long-term reference values. The 40 - 50 mm rainfall was 20 % below the long-term mean, and the duration of sunshine, at 117 - 175 hours, exceeded the long-term mean by 20 - 50 %.
April, at monthly mean temperatures ranging between 7.5 and 10.1 °C, was 1.5 - 2.5 K too warm. Precipitation during this month, at 40 - 65 mm, corresponded to the long-term mean or exceeded it by up to 50 %. At 215 - 230 hours of sunshine, the normal values were exceeded by 25 - 40 %.
May was mostly rather cold, but a few very warm days led to monthly mean temperatures of 10.5 - 12.8 °C, which corresponded to the long-term means or was up to 0.5 K above it. Precipitation in sea areas and on the islands, at 30 - 40 mm, was below average. Rainfall on the coast was up to 10 % above average, at 60 - 70 mm. The number of sunshine hours was 190 - 260; on the islands and at sea 10 % above the long-term average, on the coasts up to 10 % below it.
The monthly mean temperatures of 14 - 16 °C in June were close to normal, with the first half of the month rather cold and the fourth week unusually warm. Precipitation, at 40 - 60 mm, was mostly below average, in some places by up to 30 %. The number of sunshine hours, from 270 to 275 hours, was up to 20 % above normal.

Water temperatures

The monthly mean value of sea surface temperatures (SST) is compared to the so-called climatological value (1971 - 1993). The ranking among the highest SST monthly mean values since 1971 is given in brackets.

The mean SST in January 2005 was 7.7 °C, which was 1.2 K above the climatological value (rank 2). It was also the second warmest January temperature after 1990.
The mean SST in February was 6.5 °C, 0.8 K above the climatological mean (rank 10).
In March, the mean SST of 5.7 °C corresponded to the climatological value (rank 21).
The mean temperature in April reached 7.1 °C and was 0.5 K above the climatological value (rank 11).
The mean SST of 9.1 °C in May corresponded to the climatological value (rank 21).
The mean SST of 11.7 °C in June was 0.3 K below the climatological value (rank 21).

Ice conditions

The ice winter on the German North Sea coast was classified as weak. The coast of East Friesland and the North Sea tributaries remained completely free of ice, and only thin ice was observed in some small harbours and fairways on the coast of North Friesland on several days. There were hardly any obstructions to navigation.

Nutrients

Studies of nutrient concentrations in North Sea coastal waters in January/February 2005 showed a phosphate mean value of 0.96 ±0.24 µmol/L; this was still 70 % above the reference value of 1936 but clearly below the concentration measured in 1978, which had been four times the reference value.
In the German Bight and central North Sea, mean values of 0.67 ±0.23 and 0.57 ±0,23 µmol/L, respectively, were measured. In November 2004, higher phosphate levels had been found especially near the coast, which was probably attributable to phosphate inputs from the Wadden Sea.
Nitrite+nitrate concentrations had increased to typical winter levels as compared to November 2004, in the near-shore coastal waters from 26.5 ±4.7 to 38.9 ±2.8 µmol/L. In the German Bight and central North Sea, measured values increased on average from 11.5 ±4,1 to 18.5 ±2.8 µmol/L and from 6.6 ±4.6 to 11.8 ±2.8 µmol/L, respectively.
For silicate, which is less subject to anthropogenous impacts, concentrations of 26.9 ±3.6 µmol/L were found in the near-shore coastal waters... In the German Bight and central North Sea, values on the order of the 1936 reference levels were measured, at 12.3 ±3.5 and 7.4 ±3.5 µmol/L, respectively.

Phytoplankton

Coast of Lower Saxony
In the first half of 2005, no samples were taken for monitoring bloom-forming and toxic algae off the coast of Lower-Saxony.

Helgoland Roads
In March, at water temperatures below those of the preceding year, few diatoms and a growing number of small flagellates were observed.
In April, the abundance of phytoplankton increased markedly, especially due to the diatoms Coscinodiscus concinnus and, to a lesser extent, Coscinodiscus wailesii, as well as small flagellates and Raphidophyceae and the autotrophic ciliate Myrionecta rubra.
In May, Coscinodiscus stocks initially were still high, with a Myrionecta maximum on 3 May, followed by the Raphidophyceae maximum on 17 May. Cell concentrations of Noctiluca scintillans increased beyond mid-May but declined toward the end of the month. With decreasing cell concentrations of the two Coscinodiscus species, the abundance of phytoplankton decreased again. At the end of the month, increasing cell concentrations of the Haptophycea Phaeocystis globosa were observed.
In June, algae stocks were small at first, with the maximum of Phaeocystis development observed on 7 June (a substantially stronger maximum was recorded in the preceding year, on 11 June). At the end of the month, phytoplankton stocks were high because of abundant Rhizosolenia pungens and Guinardia flaccida, the dominant diatom species. A second maximum of Myrionecta was observed on 28 June.

North Sylt Wadden Sea
In 2005, the seasonal cycle of phytoplankton biomass showed a very shallow spring bloom with a maximum around 1 April, which was dominated by the diatoms Odontella aurita and Skeletonema costatum. The Phaeocystis bloom, which follows the spring bloom in most seasons, was very pronounced this year and peaked in mid-May. Phaeocystis was observed frequently until early June.
Potentially toxic species (Alexandrium, Dinophysis, Chatonella) were observed several times but at low cell concentrations.

Schleswig-Holstein coastal waters
In early June, the foam-forming alga Phaeocystis globosa was found to be abundant along the entire west coast of Schleswig-Holstein, at substantially higher cell concentrations than last year. Toward the end of June, the Phaeocystis globosa bloom decreased markedly, and some remaining algal colonies were only observed near the North Frisian islands, conspicuous by streaks of foam on the water. Noctiluca scintillans was quite frequent, which is typical of the season. The small diatom Pseudonitzschia delicatissima and the autotrophic ciliate Myrionecta rubra were abundant in some areas.

Fish stocks

A survey of young-fish stocks in the North Sea at the beginning of the year showed that both total catches and the numbers of most commercial fish species were below the minimum values of the preceding years. Very low numbers of the youngest age class of most species were found, so that an improvement of the precarious stock levels is not to be expected.
At the end of February/beginning of March, a survey of the frequency and distribution of malformations of pelagic fish embryos was carried out in the German Bight and southern North Sea. The malformation rate of whiting, at 14.68 %, had doubled from the preceding year. Dab embryos, which are abundant, had a malformation rate of 3.1 %, which is 1.3 % higher than last year. The malformation rates of other fish species ranged mostly between 0 and 2.5 %.
In view of the increasing number of serious infringements to EU common fisheries policy (CFP) rules, the EU Commission proposed that the Member States should not only impose markedly higher fines but should also apply administrative sanctions like, e.g., the temporary withdrawal of fishing licences.

Baltic Sea

Weather

January 2005 in the Baltic Sea area was too mild despite the cold weather in the last third of the month, at monthly mean temperatures of 3 - 4 °C, and was 3 - 4 K above the long-term reference values. Precipitation in the regions differed considerably: on the islands, at 25 - 35 mm, only 70 - 80 % of normal precipitation was recorded, whereas east of Rügen, at 50 - 65 mm, precipitation reached about 160 % of average values. 70 hours of sunshine on the islands led to a surplus of up to 85 %, and up to 30 % in the coastal areas, where mean values of 45 - 55 hours were recorded.
Mean temperatures in February ranged between -0.4 °C and 0.8 °C and were on the order of the 1961 - 1990 mean values. The precipitation of 40 - 60 mm measured in the eastern part of the Baltic coast was 40 - 110 % above normal, while the 30 - 40 mm in the western part were normal values. The duration of sunshine was 61 to 72 hours, which was ±10 % of the monthly means.
March was cold, with mean temperatures of 1 - 3 °C that were 1 K below the long-term means. Precipitation, at 27 - 40 mm, was up to 30 % below the mean values. The recorded 140 - 171 hours of sunshine were 20 - almost 60 % above the long-term mean.
April, at monthly mean temperatures between 6.7 and 9 °C, was 1 - 2 K too warm and unusually dry. At 10 - 20 mm precipitation, only 30 - 60 % of normal values was reached. The recorded 230 - 272 hours of sunshine were 30 - 50 % above the normal level.
May, too, at monthly mean temperatures of 10.8 - 12.6 °C, was 0.4 - 1.3 K too warm although there were some rather cold spells, which were compensated toward the end of the month by inflowing subtropical air in the coastal area. The measured rainfall of 60 - 70 mm exceeded the mean values by up to 60 %. The duration of sunshine, mostly 215 - 230 hours, was up to 10 % below normal (exception: Fehmarn, with an above-average 254 hours of sunshine).
In June, the monthly mean values of 14 - 16 °C were about average, with temperatures in the first half of the month too low, and very high temperatures in the second half. The precipitation of 20 - 40 mm was 35 - 70 % below normal. The duration of sunshine, at 245 - 300 hours, was up to 16 % above normal.

Water temperatures

Water temperatures on the Baltic coast of Mecklenburg-Vorpommern (measured at 3 m depth off Warnemünde and Koserow) in January were on average above the reference temperatures (2.3 and 1.7 °C, respectively). Temperatures in February corresponded to the reference series (2.1 and 1.6 °C, respectively), while the mean sea surface temperatures in March were below the reference series (3.1 and 2.6 °C). Water temperatures in April (only in Warnemünde) were slightly below those of the reference series (at 5.4 °C). In May and June, the mean water temperatures in 3 m of water corresponded to the reference series values (10.4 and 11.6, 15.0 and 15.5 °C, respectively).

Water levels

Water levels on the Baltic Sea coasts of Schleswig-Holstein and Mecklenburg-Vorpommern in January reached monthly means that were up to 26 cm above the reference series. The lowest value of 334 cm was measured in Flensburg on 9 January, and the highest level of 612 cm was recorded in Koserow on 24 January. The mean water levels in February were also up to 19 cm above the reference series. The minimum level of 430 cm was recorded in Wismar on 10 February, the maximum level of 644 cm in Schleswig on 23 February. In March, the monthly mean values were below the reference series at almost all stations, sometimes by up to 17 cm. The minimum level of 423 cm was measured in Flensburg on 10 March, the maximum level of 579 cm in Wismar on 12 March. Also in April the monthly mean values at nearly all stations were below those of the reference series. On 11 April, Stralsund reported the lowest level of 444 cm, while this month's highest value of 542 cm was observed in Flensburg on 18 April, and in Greifswald on 19 April. Mean water levels in May were slightly below those of the reference series. On 31 May, the lowest level of 436 cm was recorded in Flensburg, and the highest level of 525 cm in Eckernförde on 14 May. In June, the monthly means again were slightly above the reference series. The minimum level of 454 cm was measured in Flensburg on 5 June, the maximum level of 560 cm in Wismar.

Surface runoff

From January to June 2005, the runoff volumes of the Odra river (Hohensaaten-Finow) were below or identical to the runoff mean values of the 1941 - 2000 reference period.

Ice conditions

Ice formation in the northern Baltic area began as late as 17 November, one week later than normal, and continued very slowly in December and January because of the mild weather. Until mid-February, it lagged several weeks behind normal ice development. Extensive, strong ice formation did not set in until the second decade of February, when a four-week period of continuous frost began. The maximum of ice formation was reached on 16 March, with complete ice coverage of the Gulfs of Finland and Riga and the northern Gulf of Bothnia, and almost complete coverage of the Sea of Bothnia and northern part of the northern Baltic. Ice thicknesses between 10 and 70 cm led to considerable obstructions to navigation. The ice winter ended at the average date and, with a maximum extent of 177,000 km², was classified as a moderate ice winter.
Two periods of ice formation were recorded in the southern and western Baltic. First ice formed in small harbours and shallow inner fairways in late January/early February, but disappeared by mid-February. The second period of ice formation began on the last days of February and lasted for about 4 weeks.
On the coasts of Schleswig-Holstein and Mecklenburg, ice was observed on 4 - 20 days, but it hardly caused any obstructions to navigation.
In the shallow coastal lagoons (bodden waters) of Vorpommern, the ice season lasted 30 days on average. At the time of maximum ice formation in the first decade of March, ice thicknesses between 5 and 15 cm were recorded. Smaller, low-powered vessels could only navigate with assistance.

Nutrients

In February 2005, investigations in the area from the Kiel Bight to the northern Gotland Basin showed surface water concentrations of phosphate ranging from 0.52 to 1.22 µmol/L, most of which exceeded the long-term values significantly. Phosphate concentrations in the bottom water (controlled by oxygen conditions) reached the expected levels between 0.54 µmol/L (Kiel Bight) and 5.3 µmol/L (Bornholm Deep). The nitrite+nitrate concentrations of 2.5 to 4.5 µmol/L were normal for the season (exception: Pomeranian Bight, at 54.55 µmol/L).
In April, concentrations of nitrite+nitrate (64.05 µmol/L) and silicate (52.00 µmol/L) continued to be very high in surface water of the Pomeranian Bight, while phosphate levels were low (0.08 µmol/L), causing high plankton concentrations. In the other areas from Kiel Bight to the northern Gotland Basin, phosphate levels ranged between 0.06 and 0.84 µmol/L, nitrate between 0.04 and 1.62 µmol/L, and silicate between 1.30 und 17.70 µmol/L.
In May, nutrient levels in surface water reflected the normal spring development. Nitrate reserves in the entire study area were almost depleted. Phosphate levels ranged mostly between 0.1 and 0.2 µmol/L. Extraordinarily high values were measured in the Bornholm Basin, at 0.61 µmol/L. In near-bottom layers, stations where oxygen was present had low phosphate and relatively high nitrate values, as expected, while anoxic stations had elevated phosphate levels and zero nitrate.

Oxygen

In the first half of 2005, oxygen in surface water along the outer coasts of Mecklenburg-Vorpommern reached saturation levels. In near-bottom layers, that was still the case in February, at 6 – 9 ml/L O2, while in May the measured levels of 4 – 9 ml/L already reflected a trend toward low oxygen values (e.g. in the Mecklenburg Bight). Oxygen levels in the near-bottom layer in June reached 3 – 7 ml/L, with the lowest values measured in the Lübeck and Mecklenburg Bights where a marked thermohaline stratification was observed.
In the inner coastal waters of Mecklenburg-Vorpommern, measurements in February and May showed good oxygen saturation. Oxygen levels in June ranged from 5 ml/L (Unterwarnow) to 11 ml/L (Darss-Zingst coastal lagoons). Near the bottom, values in February still reached 8 – 11 ml/L, while the trend found in May and June, at 4 – 9 ml/L and 3 – 9 ml/L respectively, resembled that observed in the outer coastal waters.
Monitoring in the area from the Kiel Bight to the northern Gotland Basinin February showed that the water column was well oxygenated down to the bottom layer, at 6.5 – 9 ml/L O2. Oxygen depletion (below 2 ml/L O2) was observed in the Bornholm basin below 70 m depth, and in the western and eastern Gotland Basin from a depth of 60 – 80 m. H2S was found below 225 m depth in the eastern Gotland Basin, and below 100 m in the western Gotland Basin. In April, the western Baltic was found to be well oxygenated to a depth of 50 m. In the Bornholm Basin, only 2.5 ml/L O2 was found at about 70 m depth, with a decreasing trend toward the bottom. H2S occurred locally. In the Gotland Deep and Faroe Deep, H2S occurred at depths below 220 m and 190 m, respectively, and in the Landsort Deep in an intermediate layer at 125 to 200 m depth.
In May, this H2S containing layer in the Landsort Deep was found in 100 – 150 m of water; below it, O2 concentrations ranged between 0.05 und 1.19 ml/L.

Phytoplankton

Baltic coast of Schleswig-Holstein
Only few of the typical summer species of microalgae were observed by the end of May because of the late onset of summer. In the inner Flensburg Fjord, a diatom bloom of Skeletonema costatum developed, which was weaker in the outer Fjord waters and decreased noticeably by mid-June. On the whole, the algal situation showed the typical early-summer pattern.

Monitoring station "Seebrücke Heiligendamm"
Until mid-March, the phytoplankton biomass was small, dominated by Cryptophyceae (Teleaulax sp., Plagioselmis prolonga, Hemiselmis sp.) and with an abundance of typical spring species like Chaetoceros curvisetus, Ch. brevis und Mesodinium rubrum. The spring bloom, which began rather late on 22 March, was dominated by Rhizosolenia setigera, Skeletonema costatum, and Thalassiosira spp. and the Chaetoceros species Ch. curvisetus and Ch. brevis, and ended on 6 March. By early May, a diatom bloom of Rhizosolenis setigera and Chaetoceros similis had developed. It was followed by dinoflagellates (e.g. Heterocapsa rotundata, Katodinium glaucum) and Chrysophyceae (Dictyocha speculum), which were much less abundant than in the preceding years, though. An unusual, brief occurrence of Aphanizomenon sp. was observed on 3 May. By 10 May, all phytoplankton components had decreased noticeably, an exception being Cryptophyceae, Rhizosolenis setigera and, from 19 May, once more Dictyocha speculum, which were still abundant. At the end of May, the phytoplankton biomass collapsed. In June and July, Cryptophyceae (Teleaulax sp., Plagioselmis prolonga, Hemiselmis sp.) as well as dinoflagellates (Heterocapsa rotundata, Ceratium tripos), and especially the typical summer diatom Dactyliosolen fragilissimus, increased in abundance.

Outer coastal waters of Mecklenburg-Vorpommern
In January, chlorophyll-a concentrations ranged between 1.8 mg/m³ east of Sassnitz and 4.3 mg/m³ in the Bay of Lübeck. By March, Chl-a levels in the western sea areas had decreased, while they continued to rise in the eastern areas. Phytoplankton increased from <0.1 to 1.1 mm³/L between January and March, with Chaetoceros spp, Plagioselmis and Teleaulax, Heterocapsa rotundata as well as small Thalassiosira the dominant species.
In the western sea areas (extending to the area NW of Hiddensee), spring maxima between 4.5 and 7.0 mg/m³ Chl-a were measured in early April, with Skeletonema costatum and Thalassiosira sp. the dominant species. In the eastern sea areas, the spring maxima were reached at the end of April, with values ranging from 12.1 (east of Sassnitz and Pomeranian Bight) to 23.0 mg/m³ Chl-a (Greifswalder Oie). While Chl-a levels east of Sassnitz were more than two-fold above the long-term mean, they reached only 50 % in the Pomeranian Bight. The spring bloom was dominated by Diatoma elongatum.
Chlorophyll-a levels in June ranged from 1.5 to 8.1 mg/m³, corresponding largely to the long-term means, an exception being the value of 8.1 mg/m³ in the Pomeranian Bight, which was only 50 % of the long-term mean. This plankton-poor period was dominated by small flagellates (Chrysophyceae), various armoured dinoflagellates of the genus Gymnodinium, and Cryptophyceae of the genusTeleaulax.

Inner coastal waters of Mecklenburg-Vorpommern
In January and February, the chlorophyll-a concentrations ranged between 0.8 and 27.1 mg/m³, with the highest levels in the waters of Strelasund and Greifswalder Bodden, where the long-term means were exceeded 3- to 4-fold. This early bloom was dominated by Skeletonema costatum.
By March/early April, Chl-a levels in the other inner coastal waters had also increased considerably, reaching values up to 3.4 mg/m³; the dominating algae were small Chrysophyceae, Teleaulax acuta, and Diatoma elongatum. In the waters of Stettiner Haff, Chl-a levels of 21.2 mg/m³ corresponding to the long-term means were measured in late March. By mid-April, explosive plankton growth in the area caused Chl-a levels to rise as high as 228 mg/m³ (long-term mean: 85.6 mg/m³), with Diatoma elongatum the dominant species.
In April, the spring bloom was accompanied by a strong decline of dissolved nutrients, with the exception of the Stettiner Haff waters where nutrient levels remained high.
From May to June, a strong increase in Chl-a concentrations to 3.1 - 93 mg/m³ was observed at all monitoring stations except Stettiner Haff, with Stefanodiscus cf. neoastrea (diatom), Teleaulax acuta (cryptoflagellate), and Woronichinia (coccal blue-green alga) the dominant species. In the waters of Stettiner Haff, the first filamentous blue-green algae of the potentially toxic species Aphanizomenon flos-aquae, Planktothrix agardhii, and Anabaena sp. occurred in June.

Fish stocks

In June 2005, the "Advisory Committee for Fisheries Management" (ACFM) of the International Council for the Exploration of the Sea (ICES) developed recommendations for maximum catches in 2006. It stated that the condition of some Baltic Sea fish stocks gave cause for concern. Especially the recovery of Baltic Sea cod stocks was found to be impaired by overfishing including the destruction of large quantities of under-sized young cod and unfavourable environmental conditions such as oxygen deficiency. Herring stocks in the Baltic Proper have stabilised close to their historic low. Only the situation of herring in the western Baltic Sea and that of sprat was still found unproblematic.
A study of the Helsinki Commission (HELCOM) showed that the contamination of Baltic Sea fish with lead and PCBs has decreased significantly in the past 20 to 25 years, which is attributable to substantially lower annual discharges of these substances to the Baltic Sea. Nevertheless, PCB and lead levels in Baltic Sea water are still several times higher than in the North Atlantic Ocean. The annual decrease of lead concentrations in herring and cod liver since 1981 has been 4 – 7 %, that of PCB in muscle tissue of herring 4 – 10 %.
Because of the continuing increase in the number of serious infringements to EU Common Fisheries Policy (CFP) rules, the EU Commission proposed that the Member States should not only impose markedly higher fines but also apply administrative sanctions like, e.g. the temporary withdrawal of fishing licences. The EU Commission also presented a proposal for simplified fisheries regulations to the International Baltic Sea Fishery Commission which includes a harmonisation of periods of prohibition, easier on-board checks, fewer categories of fishing gear and mesh sizes.

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