MURSYS - North Sea and Baltic Sea - Report 1 2006





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MURSYS - North Sea and Baltic Sea - Report 1 2006

   
 
 

Marine Environmental Reporting System - Abstract - Reporting Period: 1 January - 30 June 2006

North Sea

Weather

January 2006 in the North Sea region began with typical winter weather and monthly mean temperatures of -0.5 °C to +2.0 °C, which was about 1 K below the mean values of the 1961 - 1990 reference period. The dry spell that had persisted for several months continued also in January. At 15 to 25 mm precipitation, only 30 - 40 % of the mean values was reached. The duration of sunshine, at 53 to 76 hours, exceeded the mean values by 15 - 65 %.
In February, monthly mean temperatures ranged from 1.5 - 2.0 °C, which was up to 0.7 K above the long-term means. The weather was generally too dry. Precipitation in East Friesland reached only 23 mm, 40 % below the mean, and in North Friesland 35 mm, just below average. The recorded 35 to 60 hours of sunshine were 30 - 50 % below the monthly means.
During the coldest March in 10 years, the monthly mean temperatures were 0.7 - 2.2 °C, or about 2 K, below the long-term reference values. 50 to 60 mm precipitation was recorded, partly as snow, which was about 10 % more than usual. Lower precipitation was recorded on the North Frisian islands. The duration of sunshine ranged from 100 to 150 hours, which was up to 20 % above average.
Monthly means in April ranged from 6 °C to 8 °C, up to 0.7 K above the reference values. Monthly precipitation in most areas was 50 to 70 mm, exceeding the means by up to 50 %. Only Sylt was too dry. 100 to 175 hours of sunshine were recorded, which was up to 40 % below the long-term means in most areas.
Despite the poor weather in the second half of May, the monthly mean temperature of 11 °C to 14 °C was 1 - 2 K too warm. 50 - 65 mm of rainfall was recorded, which exceeded the long-term means by up to 40 %. The duration of sunshine, at 200 to 250 hours, corresponded to the mean values or exceeded them locally by up to 10 %.
June in the North Sea region was too warm and too dry, with an above-average number of sunshine hours. Monthly mean temperatures ranged from 14.4 °C to 16.7 °C, which was 0.5 to 1 K above the values of the 30-year reference series. In many areas, only 10 to 20 mm - locally up to about 30 mm - rain fell, which was only 20 - 30 % of the monthly means. The number of sunshine hours was 240 to 265, exceeding the mean values by 10 - 20 %.

Water temperatures

The monthly mean sea surface temperatures (SST) were compared with the so-called climatological mean values (1971 bis 1993). The number in brackets indicates the ranking among the highest monthly mean SST since 1971:

In January 2006, the mean SST was 7.2 °C, about 0.7 K above the climatological mean (8).
The mean SST in February was 6.5 °C (as in 2005), 0.8 K above the climatological mean (10).
In March, the mean SST of 5.6 °C was 0.1 K below the climatological mean (23).
Also in April, the mean SST of 6.6 °C was 0.1 K below the climatological mean (23).
SST in May reached an average of 9.3 °C, or 0.2 K above the climatological mean (14).
In June, the mean SST of 11.9 °C again was 0.2 K lower than the climatological mean (19).
At 16.0 °C, the mean sea surface temperature in July was 1.7 K above the climatological mean value, ranking third after 1976 and 2003.

Surface runoff

The runoff volume of the river Elbe (Neu-Darchow gauge station) in April was more than 100 % above the long-term mean, which was due to the Elbe flood. Mean values in the other months during the first half of 2006 either were markedly lower than the runoff means of the 1926 to 2004 period (January to March 2006) or clearly higher (May, June).
Runoff volumes of the rivers Weser (Intschede station) and Ems (Versen station) in January were markedly lower than the 1951 - 2004 means, and still fell short of the reference means in February and March. Runoff means in April were somewhat higher than the long-term series, and in May and June they were on the order of the series.
Runoff of the river Rhine (Rees station) in January and February was markedly (by 40 and 30 %, respectively) below the values of the 1931 to 2004 long-term reference series. Mean values in March, May, and June exceeded the long-term series slightly, in April markedly (by about 50 %).

Ice conditions

In the North Frisian coastal waters, new ice began to form in mid-January. At the end of January, thin ice also formed in the Lower Elbe and in the Weser near Bremen, which decreased again in the course of the first week of February.

Nutrients

In January 2006, phosphate levels in the coastal waters of the North Sea on average were on the order of 1.19±0.14 µmol/L, in the German Bight 0.77±0.13 µmol/L, and in the central North Sea 0.64±0.13 µmol/L.
DIN levels (nitrate+nitrite+ammonium) reached values of 35.0±4.2 µmol/L in the coastal waters, 17.0±4.1 µmol/L in the German Bight, and 10.9±4.1 µmol/L in the central North Sea.
Silicate levels of 25.2±3.1 µmol/L were measured close to shore, 11.9±3.0 µmol/L in the German Bight, and 7.4±3.0 in the central North Sea.
Ammonium values were still high compared to the preceding years (5.2 - 8.8 µmol/L). This suggests incomplete decomposition of organic matter.
Compared to the January values, considerably lower nutrient levels that had been found in the coastal waters and German Bight during monitoring in November 2005. On the one hand, remineralisation at that time still was in full progress and, on the other hand, the anticyclonic weather situation prevailing until early November 2005 favoured phytoplankton growth, causing part of the released nutrients to be depleted.
Until March 2006, average concentrations of DIN (nitrate+nitrite+ammonium) continued to increase to levels of 43.6±4.3 µmol/L near the shore, 20.0±4.2 µmol/L in the German Bight, and 12.1±4.2 µmol/L in the central North Sea. It should be noted that nitrate levels continued to rise until the beginning of the first spring algal bloom, while nitrite and ammonium decreased accordingly. Also silicate values rose, reaching 28.7±4.2 µmol/L near the shore, 12.6±4.1 µmol/L in the German Bight, and 7.2±4.1 µmol/L in the central North Sea. Phosphate values in near-shore waters reached 0.97±0.20 µmol/L, in the German Bight 0.64±0.20 µmol/L, and in der central North Sea 0.53±0.20 µmol/L. In the tidal flats and close to shore, the behaviour of phosphate is opposite to that of nitrate. By complex formation with iron(III) oxide, especially phosphate is enriched, and in late summer/autumn, when anoxic conditions reach the sediment surface, it is released again, causing rising phosphate levels in late autumn.
Nutrient monitoring in May 2006 after the spring flood of 2006 showed silicate levels on the order of the detection limit (<0.6 µmol/L) in the central German Bight. The diatom bloom in spring had depleted silicate almost completely. Also phosphate levels had decreased to values between 0.18 and 0.07 µmol/L. Nitrite+Nitrate concentrations had fallen to values between 15 and 30 µmol/L. Only the values near Sylt were almost unchanged from March, probably due to major freshwater influence.

Pollutants

In the German EEZ (Exclusive Economic Zone), four monitoring campaigns were carried out in 2006 to analyse surface sediments for trace metals. The January and March data showed that mercury, lead, copper, and zinc levels were within the fluctuation range of the preceding years. The final evaluation of sediment samples from the mud sedimentation area southeast of Helgoland and from the disposal area for dredged material from the river Elbe is not yet available.

Phytoplankton

Coast of Lower Saxony
In the first half of 2006, no samples were taken to check for bloom-forming and toxic algae off the coast of Lower Saxony.

Helgoland Roads
Water temperatures at the end of March were slightly lower than the year before, and few diatoms were observed but a growing number of small flagellates, with carbon levels remaining below 20  µg C/dm³.

In the course of April, phytoplankton biomass increased from 40 to 120 µg C/dm³, initially due to the diatom Coscinodiscus wailesii, and at the end of the month Rhizosolenia hebetata semispina (first reported as Rhizosolenia setigera), small flagellates, and Raphidophyceae.

In May, carbon production varied between 85 and 185 µg C/dm³. The predominant diatom initially was Rhizosolenia hebetata semispina. In the middle of the month, many species became very abundant, with Cerataulina pelagica, Lauderia annulata, Pseudo-nitzschia seriata s.l., Ditylum brighwellii and Rhizosolenia imbricata contributing essentially to carbon production. At the end of May, Coscinodiscus wailesii prevailed. While the estimated carbon contribution of flagellates in early May was dominated by Raphidophyceae, cell concentrations of the Haptophycea Phaeocystis globosa increased toward the end of the month and reached its seasonal maximum of 7.2 µg C/dm³ (lower than in 2005) on 29 May.
In June, phytoplankton production ranged from 65 to 100 µg C/dm³. The prevailing diatom species were Coscinodiscus wailesii, followed by Lauderia annulata, Rhizosolenia hebetata semispina and Rhizosolenia imbricata, and finally Pseudo-nitzschia seriata s.l. and Leptocylindrus danicus. Among flagellates, there was a large proportion of small dinoflagellates at the end of June. Also the autotrophic ciliate Myrionecta rubra was temporarily abundant in June, at up to 18.4 µg C/dm³.

North Sylt Wadden Sea
Report will follow in the : "reporting period Juli to December"

Schleswig Holstein coastal waters
In early June, diatoms were very abundant in the sampling area, with Plagiogrammopsis vanheurckii and Odontella species prevailing in the southern coastal waters and in the North Frisian Wadden Sea, and Rhizosolenia imbricata and Cerataulina pelagica in the western part.
By late June, the number of dinoflagellate species had increased markedly in some areas. The foam-forming alga Phaeocystis globosa was observed only in a few places, at low cell concentrations.

Fish stocks

A winter survey of species (January 2006) in the Exclusive Economic Zone showed that herring catches in the reference area northwest of Helgoland had increased from the preceding year. Whiting catches continued at an extremely low level, and cod catches also were very low. Large herring schools were observed in the reference area west of Sylt.
Juvenile fish stocks in the central and northern North Sea were surveyed in January/February. Fishing hauls provided evidence that the recruitment situation of cod and Norway pout had improved markedly in comparison with the preceding years, whereas cod and whiting showed minor positive changes; the indices of both species remained below the long-term means.
In late February/early March, the frequency and distribution of malformations in pelagic fish embryos in the German Bight and southern North Sea were investigated.
Whiting embryos were found to have a malformation rate of 3.2 %, which was 11.4 % lower than in 2005. The very abundant dab embryos had a malformation rate of 3.1 %, which was 2.2 % less than the preceding year. The malformation rates of other fish species mostly ranged between 0.7 and 1.9 %.
During a hydroacoustic survey of pelagic fish stocks in the North Sea, 15 fish species were caught in June/July. The following species had the highest abundance: sprat (86 % of total weight of catches), herring (11 %), grey gurnard, and mackarel.
According to the CFP Compliance Scoreboard published within the framework of the EU Common Fisheries Policy (GFP), more than two thirds of fishery violation proceedings instituted against Member States concern cases of overfishing. Several states were fined because they had exceeded their quotas.

Baltic Sea

Weather

Monthly mean temperatures in January 2006 ranged between -0,7 °C in Kiel and -4.7°C in the area of Kleines Haff, which was 1 K to just under 4 K below the 1961 - 1990 mean. Precipitation was very low due to the influence of high-pressure systems. At 7 to 20 mm, only 20 - 35 % of the monthly means was reached. The duration of sunshine increased markedly toward the east: from 46 hours in Kiel to 78 hours at Kleines Haff, which was 20 - 110 % above normal.
Winter temperatures continued in February, with monthly mean temperatures ranging between -0.4 °C in Szczecin Lagoon and 1.0 °C at Fehmarn, which was on the order of the long-term means. Precipitation was higher than in the North Sea region, 30 - 50 mm in most areas, which was 20 to 60 % above average. About 40 to 53 hours of sunshine were recorded, which was 15 to 35 % below the monthly means.
During the coldest March in 10 years, monthly mean temperatures ranged from 0 - 1 °C, which was 1.6 - 2.7 K below average. With rainfalls between 40 and 60 mm, March was too wet in most areas; the mean values were exceeded by up to 60 %. Below-average rainfall, at 30 mm, was only recorded east of Rügen. On the islands, 130 hours of sunshine were recorded on average, which was up to 20 % above normal. With 90 to 110 hours in the other areas, there was up to 25 % less sunshine than normal.
In April, there was a marked temperature increase. With monthly mean temperatures ranging from 5.6 °C at Cape Arkona to 7.7 °C at Kleines Haff, the month of April was up to 1 K too mild. During this month, 25 mm rain fell on Rügen and 60 mm in the bay of Boltenhagen, which was 74 to 155 % of monthly means. The recorded 130 to 160 hours of sunshine were 10 to 25 % below normal.
Although much of May was too cold, it was on the whole up to 1 K too warm, at monthly mean temperatures between 10 and 12 °C. There was almost no rainfall in the first half of the month, but total precipitation nevertheless reached 45 to 80 mm, corresponding to the monthly means in almost all places or exceeding them by up to 70 %. The duration of sunshine, at 150 to 280 hours, was up to 17 % above normal.
June was too warm and dry, with an above-average duration of sunshine. Monthly mean temperatures ranged from 15.5 °C at Cape Arkona to 17.2 °C at Kleines Haff, which was 1 - 1.5 K above the 1961 - 1990 means. There were large variations in local precipitation. At 20 to 55 mm, only 40 - 60 % of the monthly means was reached in many areas. 250 to 290 hours of sunshine were recorded, exceeding normal values by up to 10 %.
July 2006 was the warmest July on record since regular measurements were begun, with the longest duration of sunshine. Monthly mean temperatures ranged between 21 and 22 °C, about 5 K above average. The dry spell continued. At 6 - 40 mm precipitation, not even half the monthly means were reached. This month's 340 to 390 hours of sunshine marked a record in many areas, with monthly means exceeded by 50 to 70 %.

Water temperatures

In January, water temperatures (at 3 m depth) at the coast of Mecklenburg-Vorpommern, off Warnemünde and Koserow on average reached 2.8 °C (0.5 K above the long-term means) and 0.6 °C (0.9 K below the series), respectively.
In February, mean values of 1.5 and -0.1 °C, respectively, were measured at these stations, both of which were below the long-term series (by 0.6 and 1.5 K, respectively)
Also in March, the mean values of 1.9 and 0.2 °C, respectively, were below the long-term means (by 1.1 and 2.4 K, respectively).
The water temperature of 5.5 °C measured in April off Warnemünde corresponded to the mean value; off Koserow, at 5.2 °C, the temperature was 0.5 K below the series.
Mean temperatures in May reached 9.5 and 9.8 °C, respectively, both below the long-term means of 0.8 and 1.6 K.
In June, a water temperature of 14.9 °C was measured off Warnemünde, and 14.7 °C off Koserow, which was slightly below the values of the reference series (by 0.1 and 0.7 K, respectively).

Water levels

Water levels on the Baltic coasts of Schleswig-Holstein and Mecklenburg-Vorpommern in January reached monthly means that were 21 cm below the values of the reference series. The lowest gauge level was recorded in Wismar on 10 January, at 419 cm, the highest level of 574 cm in Lübeck on 21 January.
Also in February, the mean water levels were up to 14 cm below the reference values. The lowest level of 423 cm was measured in Eckernförde on 7 February, the highest level of 556 cm in Flensburg on 4 February.
Also in March, the monthly means at all stations were up to 24 cm below the values of the reference series. The lowest water level, at 429 cm, was recorded in Travemünde on 19 March, the highest level of 577 cm in Lübeck.
In April, the water level mean values in Schleswig-Holstein corresponded to those of the reference series, while in Mecklenburg-Vorpommern they were up to 5 cm lower. The minimum value of 440 cm was measured at Flensburg on 9 April, the maximum of 549 cm in Lübeck on 22 April.
In May, the mean water levels in Schleswig-Holstein were 2 cm below the values of the reference series, and in Mecklenburg-Vorpommern 5 - 6 cm below them. The lowest water level, at 432 cm, occurred in Eckernförde on 24 May, and the highest level of 543 cm was recorded in Lübeck on 31 May.
In June, the monthly mean values in Schleswig-Holstein were up to 4 cm above the reference values, while in Mecklenburg-Vorpommern there was no deviation from the reference series. The lowest level of 457 cm was measured in Eckernförde on 27 June, while the maximum level of 537 cm was recorded in Kiel and Warnemünde on 1 June, and in Eckernförde on 15 June.

Surface runoff

In the first half of 2006, the runoff volumes of the river Odra (Hohensaaten-Finow gauge station) were clearly below the runoff means of the 1941 - 2004 reference period from Januar through March, whereas in April they exceeded the mean values by almost 50 %. In May, the runoff volumes were slightly higher, in June somewhat lower than the long-term means.

Ice conditions

In the northernmost Baltic region, new ice formation began in early December, about one week later than the long-term mean, spreading southward and increasing in thickness in the course of December. After a relatively mild phase in January, the ice cover in the northern Baltic continued to increase. In the second half of March, the Baltic Sea reached its maximum extent of ice cover. The entire area of the Gulfs of Bothnia, Finland, and Riga and the northernmost part of the Northern Baltic were covered with ice. From early April, mild weather led to a steady decline of ice, and the Baltic Sea ice season ended on 24 May 2006, which is close to the long-term mean.
In the German coastal waters, ice formation this winter began later than usual. Although the first cold spell at the end of November already led to local ice formation in the inner bodden waters, this first ice melted quickly, and the ice season proper did not begin until early January, when ice development set in slowly. A major cold spell began in the 4th calendar week (late January), in the course of which the maximum extent of ice coverage on the German Baltic coast was reached. Ice in the inner fairways increased noticeably, and on some of them navigation became impossible. After a slight decline of ice in the following weeks, another cold spell occurred in the 10th/11th calendar weeks (early/mid March), which led to extensive new-ice formation during the night.
However, long periods of sunshine with strong insolation led to an overall retreat of ice. The ice season in the western Baltic Sea ended on 29 March.

Nutrients

Im January/February 2006, monitoring in the area from Kiel Bight to the northern Gotland Basin showed that phosphate concentrations in the surface water were below levels found the year before and were on the order of the long-term means. Nitrate levels (2.2 - 4 µmol/L) were slightly below the long-term means. In May, nitrate concentrations were depleted almost everywhere, whereas phosphate was still found in the surface water (0.1 - 0.35 µmol/L).
Levels of phosphate and nitrate in the bottom layer, controlled by oxygen and hydrogen sulphide concentrations, were of the expected order of magnitude.

In the outer coastal waters of Mecklenburg-Vorpommern, phosphate levels in the surface water continued to decline from January to April and were often on the order of the long-term means. In April, with the onset of plankton growth, concentrations sometimes were close to the detection limit of 0.02 µmol PL. Nitrate levels increased from January to March but were mostly low in comparison with the long-term means; from April, concentrations fell sharply to less than 1 µmol N/L in most areas.
In the inner coastal waters of Mecklenburg-Vorpommern, phosphate concentrations had decreased steadily to values of 0.2 to 0.3, locally even below 0.1 µmol/L due to the onset of primary production. Frequent rains in February/March had caused nitrate levels to more than double compared to their long-term means. In April, peak values were measured in the Lower Warnow (260 µmol/L) and in the waters of Barther Bodden (98 µmol/L) and Salzhaff (95 µmol/L). In contrast, nitrate was almost depleted in the Greifswalder Bodden waters.

Oxygen

In the outer coastal waters of Mecklenburg-Vorpommern, oxygen in the surface water reached saturation levels from January to April. In the bottom layer, levels of 5.5 mg/L (50 % saturation) were measured in the Bay of Lübeck in January. The other parts of this sea area had good oxygen values until March. In April, first signs of oxygen deficiency in the bottom layer (60 % saturation) were observed in the western part of Mecklenburg Bight, at 6 - 7 mg/L oxygen.

Elevated oxygen levels measured in surface water of the inner coastal waters of Mecklenburg-Vorpommern from January to April 2006 resulted from higher seasonal primary production in spring.

Monitoring in the area extending from Kiel Bight to the northern Gotland Basin in January/Februar 2006 showed good oxygen levels in the western Baltic Sea and Arkona Basin, including the bottom layer. Oxygen depletion with values of less than 2 ml/L O2 was found below 70 m in the Bornholm Basin. In the deep basins, hydrogen sulphide was found at water depths below 100 and 150 m, respectively.
By May, oxygen in the bottom water of the Bornholm Sea was almost depleted. The situation in the deep basins had not changed significantly.

Phytoplankton

Baltic coast of Schleswig-Holstein
From mid-June, the abundance of dinoflagellates increased slightly. Small flagellates occurred at moderate to elevated concentrations, whereas very few diatoms were observed. First blue-green algae were found at very low concentrations. In the first week of July, all blue-green algae increased noticeably in abundance.

Monitoring station "Seebrücke Heiligendamm"
In mid-January, phytoplankton included major concentrations of typical autumn dinoflagellates (Ceratium tripos) and spring diatom species, with the following temporal sequence of genera: Actinocyclus, Thalassiosira, Porosira, Rhizosolenia, Skeletonema. At the beginning of the spring bloom on 7.3., Porosira glacialis prevailed, but also Skeletonema marinoi was very abundant. On 28.3., the diatom bloom decayed, and the abundance of dinoflagellates increased. The bloom peaked on 11.4. with Dictyocha speculum. On 25.4., the Prymnesiophycea Chrysochromulina sp. developed. After biomass had decreased markedly by 9.5., a variety of summer species developed which had a relatively low biomass. In early June, the period of minimum growth ended when various dinoflagellate species increased in abundance. Also Chrysochromulina sp. was frequent on 6.6., and by 13.6. the dinoflagellate Cryptaulax marina prevailed.

Outer coastal waters of Mecklenburg-Vorpommern
In March, chlorophyll-a levels in the area still were below the long-term means. In early to mid-April, the mean values were clearly exceeded, with a new extreme value of 11.4 µg/L (long-term mean: 2.0 µg/L) measured in the Mecklenburg Bight. The biovolume in the area was unusually high, at 3.2 mm³/L, and was dominated by Dictyocha speculum. All other measuring stations in this sea area showed only slightly elevated chlorophyll-a concentrations.
In the eastern sea areas (Pomeranian Bight), Chl-a values were clearly elevated, with the diatoms Chaetoceros and Achnanthes taeniata and the cryptoflagellate Teleaulax the dominant species.

Inner coastal waters of Mecklenburg-Vorpommern
In the inner coastal waters, extremely high chlorophyll-a levels were observed as early as March. For example, in the Strelasund waters the long-term mean was exceeded by 704 %, with a chlorophyll-a value of 40.1 µg/L, and in the Greifswalder Bodden by 352 % at 39.1 µg/L Chl-a. The phytoplankton biovolume in the Strelasund reached a maximum value of 9.3 mm³/L due to strong growth of the centric diatoms Thalassiosira and Achnanthes taeniata.

Fish stocks

The CFP Compliance Scoreboard published within the framework of the EU Common Fisheries Policy (GFP) again called for better and timely reporting by the Member States, especially with regard to quota use. Once again, numerous Member States were fined because they had exceeded their quotas.
In May/June 2006, a hydroacoustic survey of pelagic fish stocks was carried out in the Baltic Sea, co-ordinated by the ICES working group "Baltic International Fish Survey Working Group". As is typical of the season, sprat was dominant among the catches; herring and cod were caught regularly, at weight percentages of 10 % and 7 %, respectively.
In the ecologically important areas off the German Baltic Sea coast (Kiel and Mecklenburg Bights, Darss Sill, Arkona Sea, east of Jasmund, and western edge of the Odra Bank), a survey of demersal fish fauna using bottom trawl nets was carried out in June/July. During the four-year survey period, numbers of the four most important bottom-living species cod, dab, flounder, and plaice had decreased in all areas surveyed ("boxes"). Only in the Arkona Sea was the number of cod unchanged from the preceding years, but their size was mostly below 38  cm.
In July, the EU Commission adopted a several-year plan for the two Baltic Sea cod stocks. Research data has shown that the eastern stock is overfished and threatened by a complete breakdown. Also in the western stock, which is in a slightly better condition, catches are clearly below the long-term potential level. The plan is aimed at reducing fishing mortality to such an extent that stable harvesting is achieved in the long run. The problem of under-reported catches also affects cod stocks in the Baltic Sea considerably.

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