MURSYS - North Sea and Baltic Sea - Report 2 2005





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MURSYS - North Sea and Baltic Sea - Report 2 2005

   
 
 

Marine Environmental Reporting System - Abstract - Reporting Period: 1 July - 31 December 2005

 

North Sea

Weather

July was 1 - 2 K too warm, at monthly mean temperatures between 17 and 18 °C. Due to above-average rainfall of 64 mm to 130 mm, up to 160 % of normal precipitation was recorded. The duration of sunshine was 160 - 190 hours, which was 20 - 25 % below the mean values.

August, at mean temperatures between 15.6 and 16.5 °C, was 0.7 K too cold, and no hot days (daily maximum temperature at least 30 °C) were recorded. It was mostly too wet and, at 80 - 95 mm precipitation, monthly mean values were exceeded by up to 30 %. Only a few islands were slightly too dry, at 55 - 70 mm rainfall. 135 - 180 hours of sunshine were recorded, which was 15 - 30 % below the long-term means.
Monthly mean temperatures in September, at 15.6 to 16.4 °C, almost corresponded to those in August and were up to 2.2. K too warm. On the North Sea coast and on the islands, it was clearly too dry. With precipitation of only 40 - 50 mm, a 25 - 50 % rain deficit was recorded. The 195 - 205 hours of sunshine, which was 30 - 50 % above the mean values, were unusual for the season.
The monthly mean temperatures between 12 and 14 °C recorded in October exceeded the mean values of the 1961 - 1990 reference period by 2 - 3 K. Precipitation, at 45 - 75 mm, was 10 - 50 % below the long-term means. A low-pressure system at the end of the month finally brought strong rainfall. The sunniest October on record since 1951 brought 175 - 195 hours of sunshine, which was 80 - 90 % above normal.
Owing to a very warm first half of the month, also November was too mild, at monthly means of 7 - 8 °C, which was 1 - 2 K above the 1961 - 1990 reference values. The first spell of winter weather, with snow and up to 5 days of frost, occurred at the end of the month. The recorded precipitation of 65 - 86 mm corresponded to a deficit of 10 - 30 %. The total duration of sunshine was 54 - 66 hours, which corresponded to the local means or exceeded them locally by up to 40 %.
December temperatures ranged between 3.5 °C in North Friesland and 5.6 °C on Helgoland, which was about 1 K above normal. At 6 - 10 frost days and up to 2 days of ice, the long-term means were not reached. Precipitation ranged mostly from 40 - 60 mm, which was 15 - 40 % below the monthly means. The number of sunshine hours was 40 - 50 hours in most areas, which was above normal. A record number of 68 hours of sunshine, or 160 % of normal, was recorded on Sylt.

Water temperatures

The mean values of the sea surface temperatures (SST) were compared to the so-called climatological values (1971 - 1993); their ranking among the highest SST monthly means since 1971 is indicated in brackets:

The mean SST of the North Sea in July was 14.8 °C, which was 0.5 K above the climatological value (rank 13).
In August, the mean temperature of 14.9 °C was 0.1 K below the climatological value (rank 23).
A monthly mean of 14.9 °C was also recorded in September, causing the climatological value in this month to be exceeded by 1.2 K (rank 7).
In October, the mean SST was 13.3 °C, 1.5 K above the climatological value and the warmest October temperature on record since 1971 (rank 1).
November, too, had the highest mean SST since 1971 (rank 1). At 11.5 °C, the climatological value was exceeded by 1.9 K.
The mean value in December was 9.0 °C, which was 1.2 K above the climatological value (rank 3).

Ice conditions

In the ice season of 2005/2006, no ice had formed on the German North Sea coast by the end of December 2005.

Nutrients

In September 2005, low nutrient concentrations were found in the surface layer of the German Bight, which were due to plankton growth: phosphate 0.02 - 0.15 µmol/L, nitrate near the detection limit of 0.1 µmol/L. Higher concentrations occurred only in the coastal waters and Elbe outflow.
Elevated levels of nitrate, phosphate and silicate in the bottom layer were found in areas with temperature stratification and near the shore. Elevated ammonium levels near the bottom (between 2.2 µmol/L offshore, and 6,8 µmol/L in the Elbe estuary) indicated the beginning of remineralisation.
During monitoring in November 2005, phosphate values of 1.09 ±0.25 µmol/L, nitrate+nitrite values of 19.4 ±6.0 µmol/L, and silicate values of 13.1 ±5.4 µmol/L were found in the coastal waters of the German Bight. In offshore waters, phosphate levels reached 0.66 ±0.24 µmol/L, nitrate+nitrite 8.7 ±5.7 µmol/L, and silicate 6.4 ±5.2 µmol/L. In all areas, the values were below those of November 2004.

Oxygen

In August 2005, oxygen saturation was found to be very good in all North Sea areas monitored. Saturation values just under 80 % were measured only in the outer German Bight and off the coast of Jutland, and about 66 % saturation between the Dogger Bank and Little Fisher Bank. Monitoring data from the German Bight in September 2005 showed good oxygen saturation even in deeper layers. The lowest saturation of 70 % (approx. 6 mg/L) was found in the area of Little Fisher Bank and in the Elbe glacial river valley.

Pollutants

Pollutant data for 2005 are not yet available for the North Sea. They will be published later, possibly in the "MURSYS retrospective".

Phytoplankton

Coast of Lower Saxony
The sampling programme in the coastal waters of East Friesland to check for bloom-forming and toxic algae at seven near-shore stations was started by Lower Saxony's "Landesbetrieb für Wasserwirtschaft, Küsten- und Naturschutz" (NLWKN) at the end of July. Throughout the sampling period from late July to early October, no dangerous quantities of toxic plankton species or HAB (Harmful Algal Bloom) forming phytoplankton species were found.

The non-toxic dinoflagellate Dinophysis rotundata occurred only at the beginning of August, in der Jade estuary, at 100 ind./L.
The bioluminescent Noctiluca scintillans, a non-toxic heterotrophic dinoflagellate, was observed in the Jade region at the end of July, at up to 86 ind./L, increasing to maximally 121 ind./L by the end of August. After this, numbers of individuals decreased steadily to a low of maximal 17 ind./L at the end of the monitoring period.
Throughout the sampling period, critical densities of microflagellates of the genus Chrysochromulina (Prymnesiophyceae) did not occur in the survey area.
Only few colonies of the foam-forming alga Phaeocystis, which also belongs to Prymnesiophyceae, were found at the stations; a slightly higher number of colonies - 65 colonies/L - was observed between the Ems and Norderney as late as the beginning of August.
The ciliate Myrionecta rubra was counted at densities of up to 900 ind./L at the end of July (Jade), after which it decreased steadily until, by early September, it was no longer present at any of the stations. Until early October, up to 100 ind./L were still counted at individual stations.
Diatoms of the potentially toxic genus Pseudo-nitzschia were dominant among phytoplankton at the end of July, at 10,000 to 14,000 ind./L, in the western part of the monitoring area, whereas farther east they were hardly found at all. In August, concentrations at all stations rose to max. 47,000 ind./L in early August, and max. 72,000 ind./L by the end of the month. Low numbers of 9,000 ind./L were found only in the Jade region. From early September, diatoms were clearly less dominant, with concentrations of max. 5,700 ind./L observed only at the eastern stations. At the beginning of October, numbers in this area once more rose to max. 10,800 ind./L.

Helgoland Roads
In July, concentrations decreased from 112 to 19 µg C/dm³, and few diatoms were observed. Ceratium fusus reached its maximum of 66 µg C/dm³ on 11 July.
In August, phytoplankton stocks ranged between 21 and 97 µg C/dm³ and were dominated by diatoms of the following species: Bacteriastrum hyalinum (maximum on 1 August: 11 µg C/dm³), Leptocylindrus minimus (on 15 August: 7 µg C/dm³), Rhizosolenia shrubsolei (on 15 August: 13 µg C/dm³), Chaetoceros debilis (maximum on 22 August: 13 µg C/dm³), Guinardia delicatula (on 22 August: 15 µg C/dm³), and Pseudo-nitzschia seriata s.l. (on 22 August: 10 µg C/dm³).
In September, phytoplankton decreased from 76 to 32 µg C/dm³ and showed a high species diversity, comparable to September 2004. Maxima were reached by Leptocylindrus danicus on 5 September, at 12 µg C/dm³, Guinardia striata at 16 µg C/dm³, and Ceratium furca at 9 µg C/dm³ on 12 September.
In early October, phytoplankton densities continued to decrease from 13 to 9 µg C/dm³.

Abundances
Comparison with the preceding year:
(species which may occur at higher concentrations or in toxic variants)

Pseudo-nitzschia seriata s.l.:
2005 from July - October, maximum on 22 August: 98,000 cells/dm³.
2004 from June to October lower concentrations, maximum of 7,600 on 7 September 2004.
Ceratium furca:
2005: (July), August - October, maximum of 2,300 (12 September).
2004: July - October, up to 2,800 cells/dm³ (22 September 2004).
Ceratium fusus:
2005: (March, April, May), June - July, (August, September), maximum of 26,000 (11 July), more frequent than in
2004: July - October, up to 5,400 cells/dm³ (3 August 2004).
Ceratium longipes (+ horridum):
2005: July - September, maximum of 360 on 12 September, low numbers as in the preceding year:
2004: September - October, up to 280 cells/dm³ on 12 October 2004.
Dinophysis acuminata:
2005 moderate concentrations from May to October (as in 2004), maximum im August (360 cells/dm³ on 22 August 2005).
Noctiluca scintillans:
2005: abundance from May - August (September), higher numbers: 186 (28 June) - 312 (maximum on 15 August)
2004: moderate numbers in June and July, then slightly more frequent until mid-August (maximum on 3 August 2004, 590 cells/dm³)
Phaeocystis globosa:
2005: late May - early June (maximum of 1,526,000 on 7 June), much less abundant than in
2004: (maximum of 10,493,000 on 11 May 2004).
Prorocentrum micans:
2005: earlier (June - September) and more numerous (maximum of 3,200 on 29 August) than in
2004 (August - October, maximum of 800 on 14 September 2004).
Prorocentrum triestinum (synonym: P. redfieldii):
2005 as in the preceding years: August - September, maximum of 16,000 (22 August), more numerous than in
2004 (up to 320 cells/dm³ on 28 September 2004).

Phytoplankton in selected samples at the Helgoland Roads station, GIF-Graphic=14,0 KB

Figure 1: Phytoplankton in selected samples at the Helgoland Roads station (µg C/dm³ estimated on the basis of counts)

North Sylt Wadden Sea
The dominant phytoplankton species in summer was Rhizosolenia imbricata. Also Phaeocystis globosa was observed frequently, especially in August.
Phytoplankton in autumn showed the typical seasonal aspect of a very high species diversity. The maximum was reached in early October (62 diatom species, 16 dinoflagellate species).
Potentially toxic algae (Alexandrium, Dinophysis, Chattonella, Gymnodinium) were observed several times, but at small cell concentrations.
Compared to the preceding years, the autumnal increase in nutrients was very late this year. By the end of October, a marked increase was not yet visible. According to recent data, the increase began as late as early November, which is about 6 weeks later than normal. The summer values of nutrients were in the normal range (Si: 0 - 3 µM; NO3: 0 - 2.6 µM; NH4: 0.2 - 2.6 µM). PO4 increased continuously from the end of April, as usual, and reached its summer maximum of about 0.6 µM at the end of September.

The three most conspicuous observations of this year were the rather late and rather weak spring bloom in mid-April, the rather intensive subsequent Phaeocystis bloom in mid-May, and the very long growth season lasting through October (late onset of autumnal nutrients increase).

Seasonal cycle of phytoplankton biomass in 2005, GIF-Graphic=5,75 KB

Figure 2: Seasonal cycle of phytoplankton biomass in 2005 (µg chlorophyll-a/L)

Schleswig-Holstein coastal waters
In early July, the composition of phytoplankton changed completely.
Typical summmer diatom species increased strongly, with Odontella species and Guinardia flaccida prevailing in the Meldorf Bay, Rhizosolenia similoides south of Eiderstedt, in the area of the North Frisian islands, and near Helgoland. Dinoflagellates were less abundant than normal for the season, and only Noctiluca scintillans was frequent.
By this time, the foam-forming Phaeocystis globosa had disappeared completely.
At the end of July, diatoms were still dominant, and a decrease in their concentrations was not observed in the area of the North Frisian islands until early to mid-August. The abundance of Phaeocystis globosa continued to increase in this area and south of Eiderstedt.

Fish stocks

The annual surveys of fish fauna, which have been carried out at 12 permanent monitoring stations in the North Sea since 1987, again confirmed in August 2005 that despite intensive efforts to rebuild cod stocks in the North Sea there still are no signs of a recovery. Losses of demersal species like cod, plaice, and whiting have been compensated by increases in pelagic stocks (mainly herring) and stocks of small, bottom-dwelling species like dragonet, solenette, and scaldfish which used to be decimated by whiting and cod in the past.

Health monitoring of North and Baltic Sea fish in September confirmed the preceding years' findings for dab, which had shown regional differences in infections with viral and bacterial skin diseases, parasites, and liver tumors. The prevalence of lymphocystis and liver tumors in the North Sea was generally low, whereas dab in the area of oil and gas platforms had a higher prevalence of lymphocystis, skin tumours, and parasites.

In view of the poor condition of many demersal stocks in the entire area covered by the ICES Convention, it was recommended at the autumn meeting of ACFM (Advisory Committee for Fisheries Management) of ICES (International Council for the Exploration of the Sea) to limit many mixed fisheries. Among the stocks with sufficient reproduction capacity and sustainable management, the important species for German fisheries in the North Sea are haddock, sole and saithe, as well as the spring-spawning Norwegian herring. Critical stocks in the North Sea are cod, whiting, sand-eel, Norway pout, picked dogfish, and porbeagle.

In December, the European Commission adopted a 2006 - 2008 Action Plan for Simplifying and Improving the Common Fisheries Policy (CFP). Priority initiatives in the next three years will affect two important areas: the conservation of fishery resources, and monitoring of fishing activities. Also the publication of the CFP Compliance Scoreboard has to be seen in this context. While improvements were noted in fleet management and in the implementation of programmes of structural policy, there were major deficits regarding timely and comprehensive reporting. A big problem was the exceedance of quota; the Member States will have to intensify their efforts to prevent overfishing.

Baltic Sea

Weather

Monthly mean temperatures in July, at 17.7 - 18.6 °C, were about 1.5 K above the long-term mean. Precipitation deficits from the preceding month were compensated. At 60 - 105 mm, up to 170 % of the normal monthly mean of July was recorded. The duration of sunshine was 180 - 277 hours, increasing toward the east. In the western Baltic, values were 10 % below the mean, east of Rügen up to 10 % above it.
Monthly mean temperatures in August, at 16 - 16.8 °C, were up to 0.5 K below average. Rainfall was below-average, too, at about 50 - 60 mm, which was up to 30 % below the monthly mean. In some areas precipitation was considerably lower. The duration of sunshine was 180 - 220 hours, up to 15 % below normal, and values above normal were only recorded on the island of Rügen.
September mean temperatures ranged from 15.2 - 15.8 °C, which was 1.6 - 2.0 K too warm. Monthly rainfall at the southern and eastern Baltic Sea was 5 bis 20 % below normal, and precipitation in some areas of Schleswig-Holstein reached only 30 % of the long-term monthly total. The recorded 165 - 210 hours of sunshine were 15 - 30 % above normal.
Monthly mean temperatures in October were 11 - 12 °C, exceeding the long-term mean by about 2 K. In the course of the month, 29 mm (Kleines Haff) to 8 mm (Kiel) rain was recorded, with local mean values up to 20 % below normal or up to 40 % above normal. Sunshine was recorded during 170 - 205 hours, exceeding normal by 60 - 90 %. This month was the sunniest October on record since 1951.
Temperatures in November ranged from 4.8 °C (Kleines Haff) to 7 °C (Fehmarn), exceeding the long-term reference values by up to 1 K. With sub-zero temperatures on 4 to 9 days, the mean values were reached or exceeded by up to 2 days. Only 14 to 44 mm of rain was recorded, which corresponds to a deficit of 50 - 70 % in the western Baltic, and 20 - 35 % in the southern Baltic. With 70 - 88 hours of sunshine, the mean values were exceeded by 30 - 70 %.
In December, the monthly mean temperatures between 1 °C (Kleines Haff) and 3 °C (Fehmarn) were up to 1 K above the reference values, with wintry temperatures prevailing in the second half of the month. This month's 10 - 16 days of frost corresponded to the coastal mean values, while the recorded 1 - 4 of days with ice were up to 3 below the reference values. With rainfall between 40 and 70 mm, monthly means were mostly exceeded, locally by up to 46 %. About 30 - 50 hours of sunshine were recorded, exceeding the long-term means in most areas by up to 33 %.

Water temperatures

Water temperatures (at 3 m depth) on the Baltic coast of Mecklenburg-Vorpommern (measured off Warnemünde and off Koserow/Usedom) in July averaged 17.7 and 19.3 °C, respectively, and were up to 1.3 K above the values of the reference series (1997 to 2005). Mean water temperatures in August were 17.0 and 18.4 °C, respectively, corresponding to the reference values. In September, 16.0 and 17.7 °C were measured on average; these values were up to 1.1 K above those of the reference series. In October, mean water temperatures at 3 m depth were 14.0 and 13.3 °C, respectively, which was up to 2 K above the values of the reference series. Water temperatures in November were 10.0 and 7.7 °C, respectively, exceeding the reference values by 1 to 2 K. In December, the mean water temperature of 6.3 °C measured off Warnemünde was 1.7 K above the reference series, while the mean value of 3.1 °C recorded at Koserow corresponded to that of the reference series.

Water levels

Mean water levels off the Baltic coast of Mecklenburg-Vorpommern in July were up to 6 cm above the reference values at all stations of the long-term series. The lowest monthly value was 456 cm, measured at Flensburg. The highest level of 551 cm was recorded at Heiligenhafen.
Also in August , monthly values exceeding the reference series by up to 11 cm were measured at all stations. The lowest value of 459 cm was measured at the Flensburg gauge station, the highest value of 548 cm at Eckernförde.
Monthly mean values in September were up to 5 cm above those of the reference series. Both the maximum value of 553 cm (10 September) and the minimum value of 441 cm (15 September) were recorded at the Flensburg station.
In October, the monthly mean values at three of four stations of the long-term series were up to 10 cm below the reference values. The lowest water levels of the month were recorded in Lübeck, at 412 cm, and Rostock, at 413 cm, and the highest level in Flensburg, at 553 cm.
Mean water levels in November were below the values of the reference series at all stations (by up to 8 cm). The minimum of 373 cm was measured at the Flensburg gauge station on 15 November, while the maximum of 563 cm was recorded in Koserow on 21 November.
The monthly mean values in Dezember exceeded the reference values at all stations, locally by up to 11 cm. The lowest value of 401 cm was recorded at Wismar on 11 December, the highest value of 604 cm in Lübeck on 29 December.

Surface runoff

Also during the second half of the year, from July to December 2005, part of the Odra runoff measurements (Hohensaaten-Finow) were found to be clearly below the mean values of the 1941 - 2000 series.

Ice conditions

Seasonal ice formation in the northern Baltic began on 1 December 2005 in the near-shore Archipelago area of the northern Bay of Bothnia, about three weeks after the mean date. Strong frost led to an increase in the ice cover in all areas of the northern Baltic Sea by the end of December.
In the 2005/2006 ice season on the German Baltic coast, only temporary ice formation occurred in the inner coastal waters by the end of 2005.

Nutrients

Nutrient concentrations in surface water in the area extending from the Kiel Bight to the northern Gotland Basin in July ranged between zero (western Gotland Sea) and 0.35 µmol/L (Arkona Basin and Pomeranian Bight) for phosphate, and mostly between zero and 0,34 µmol/L (Arkona Basin) for nitrate+nitrate.
Surface water phosphate values in October/November ranged from 0.2 µmol/L in the central Gotland Sea to 0.84 µmol/L in the Pomeranian Bight. Nitrate+nitrate levels ranged between 0.07 µmol/L in the Mecklenburg Bight and 0.49 µmol/L in the central Gotland Sea.
High phosphate levels (4 µmol/L  - >7 µmol/L) and almost no nitrate were found in the anoxic bottom water layer, while 0.3 - >7 µmol/L nitrate and 0.8 - 3 µmol/L phosphate were measured at the other stations.
In the outer coastal waters of Mecklenburg-Vorpommern, falling oxygen levels in the Mecklenburg and Lübeck Bights from early July led to reduced nitrification. NH4-N levels of up to 8.0 µmol/L were measured near the bottom, and a maximum value of 9.3 µmol/L NH4-N was found at 16 m depth. Ortho-phosphate values in deeper layers ranged from 0.93 to 1.04 µmol/L o-PO4-P, and at the surface from 0.12 to 0.20 µmol/L o-PO4-P. In the first decade of August, nitrate levels in this area to a depth of 16 m were below the detection limit of <0.1 µmol/L, while 7.86 µmol/L was measured at the bottom. NH4-N concentrations rose from <0.1 µmol/L at the surface to 3.47 µmol/L near the bottom. o-PO4-P levels ranged between 0.21 µmol/L near the surface to 1.07 µmol/L near the bottom.
In early August, in the sea area north-west of Fischland extending to the area north of Darsser Ort, nutrient values were normal for the season: nitrate levels in surface water and near the bottom were below the detection limit (<0.10 µmol/L), and NH4-N levels ranged from 0.23 - 0.33 µmol/L at the surface and 0.32 - 0.47 µmol/L near the bottom. Concentrations of phosphate were well balanced between the surface and bottom, ranging between 0.16 and 0.24 µmol/L o-PO4-P.

In mid-August, NH4-N concentrations <0,1 µmol/L were recorded farther to the east, between Kap Arkona and east of Sassnitz, with local maxima of up to 2.35 µmol/L in deeper layers. Surface nitratevalues reached 0.21 µmol/L, locally up to 2.72 µmol/L in deeper layers. Concentrations of o-PO4-P near the surface, at 0.48 µmol/L, and near the bottom, between 0.55 und 1.07 µmol/L, corresponded to the long-term means.

Oxygen

Oxygen deficiency in bottom water of the western Baltic is monitored annually in late summer and autumn at a dense network of monitoring stations.
As early as July, a trend toward low oxygen levels clearly below 4 mg/L was observed in the bottom water of some areas with weak water exchange (Bay of Lübeck, Kiel and Mecklenburg Bights).
High deepwater salinities led to a particularly strong seasonal vertical stratification, which prevented oxygenation of the bottom water. Oxygen depletion was a wide-spread phenomenon in August/September 2005 and was comparable to the two preceding years, although conditions were not as catastrophic as in 2002.
The following relative frequencies (in per cent) of oxygen levels in near-bottom water at water depths of more than 15 m were determined for September: 70 % of all oxygen data were in the life-threatening range of less than 2 mg/L O2 (85 % in 2002), and some 20 % of measurements (4 % in 2002) ranged between 2 and 4 mg/L O2. The proportion of good to very good oxygen levels (greater than 4 mg/L O2) was only 11 % (6% in 2002). Hydrogen sulphide, a strong cell toxin, was found in near-bottom water at nine stations in low-exchange areas of the Kiel Bight.
Measurements in the outer coastal waters of Mecklenburg-Vorpommern indicated that oxygen levels in the near-bottom layer decreased progressively from the south-western Mecklenburg Bight toward the Bay of Lübeck. In August, the measurement transect showed critical oxygen levels of 0.4 and 1.6 mg/L O2, respectively, at the stations in the Bay of Lübeck and Mecklenburg Bight. In the coastal waters east of Darss Sill, oxygen levels in the bottom layer were still sufficient in August.
Also from September through November, major oxygen deficiency was found below 20 m water depth at the stations between Kühlungsborn and Boltenhagen. For the first time since monitoring started in 1975, values below 1 mg/L O2 were still measured in November.
In the inner coastal waters, oxygen levels in the outer Wismar Bight fell to 2 mg/L O2 in November, and in the Unterwarnow to a minimum of 3 - 4 mg/L O2 in October.
During the monitoring cruise in July, which covered the area from the Kiel Fjord to the northern Gotland Basin, oxygen deficiency was found in the Bornholm Basin below 75 m depth, in the central gotland Basin and Faroe Deep below 120 - 130 m, and in the Landsort and Karlsö Deeps below 80 m water depth. Hydrogen sulphide was found in the bottom water of all deeps monitored.
The oxygen situation continued to deteriorate until October/November: H2S was found in bottom water in the Bay of Lübeck and at many stations in the Bornholm Sea, and also the O2 levels in bottom water of the Arkona Sea dropped close to zero.

Pollutants

Pollutant data for 2005 are not yet available for the Baltic Sea. They will be published later, possibly in the "MURSYS retrospective".

Phytoplankton

Baltic coast of Schleswig-Holstein
In early July, high cell concentrations of typical summer diatoms like Dactyliosolen fragilissimus and Proboscia lalata occurred almost everywhere. The species spectrum of dinoflagellates increased markedly, though cell concentrations were still low. Sunny weather favoured the growth of filamentous blue-green algae, which appeared almost everywhere at medium to high cell concentrations (especially Anabaena, but also Aphanizomenon and Nodularia). Cooler weather in mid-July led to a noticeable decrease of filamentous blue-green algae in the coastal waters. Diatoms continued to be most abundant, but also the red-tide causing dinoflagellates Heterocapsa triqueta, H. rotundatum, and Prorocentrum minimum occurred in visible concentrations, even causing reddish water discoloration in the inner fjord areas.
In early August, typical summer species of microalgae were still quite abundant. Diatoms continued to be dominant, with Ceratium species increasing among dinoflagellates; increased cell concentrations of red-tide species were still observed in the fjords.
In late August and early September, a marked decrease in species diversity and cell concentrations of microalgae was observed nearly everywhere. A few diatom species (Guinardia flaccida, Rhizosolenia pungens, Pseudonitzschia) and dinoflagellate species (Ceratium tripos, C. fusus, Prorocentrum micans) dominated the overall picture. The non-toxic filamentous blue-green alga Aphanizomenon occurred at medium concentrations in the inner Lübeck Bay.

Monitoring station "Seebrücke Heiligendamm"
In June and July, Cryptophyceae (Teleaulax sp., Plagioselmis prolonga, Hemiselmis sp.), dinoflagellates (Heterocapsa rotundata, followed by Ceratium tripos), and especially that of the typical summer diatom Dactyliosolen fragilissimus, became more abundant. The minimum on 28 June (week 26) was attributable to problems of microscopic analysis resulting from a high proportion of sediment in the samples, and is thus an artefact. Dactyliosolen fragilissimus reached its biomass maximum of 3,560 mg/m³ on 26 July 2005. On 16 August 2005 (week 33), Mesodinium rubrum and Eutreptiella sp. (included here under "Others") were observed. On 23 August 2005, the composition of diatoms was found to be completely changed. Dactyliosolen fragilissimus had been replaced by Cerataulina pelagica, Guinardia flaccida, Proboscia alata, and Rhizosolenia pungens. The dominant species now was the dinoflagellate Ceratium tripos (470 mg/m³), which is typical of the season. After a different water mass (containing Dactyliosolen fragilissimus, Nodularia spumigena, and Aphanizomenon sp.) had obviously reached the station on 30 August 2005 (week 35), the status of 23 August 2005 was found to have returned to the station on 6 September 05. Biomasses subsequently decreased. The extremely low biomass in the 40th week again was an artefact resulting from the high sediment content, as had been the chlorophyll concentration.
By 18 October 2005 (week 42), an extreme bloom of Ceratium fusus (1853 mg/m³) and C. tripos (1841 mg/m³) had developed, which also included extremely small Ceratium stages. Such a strong growth within one week is unlikely. A more plausible explanation is another water mass (from the western Baltic) that had probably moved into the area, and which disappeared again the following week. On 2 November 2005 (week 44), also Guinardia flaccida, Dictyocha speculum, Teleaulax sp., Dactyliosolen fragilissimus, and Mesodinium rubrum were found besides Ceratium. Only one week later, Ceratium had disappeared completely, only to return on 15 and 23 November 2005 (weeks 46, 47) together with Guinardia flaccida. On 29 November 2005, Coscinodiscus granii was the dominant species, which points to the presence of a water mass originating in the Baltic Proper. Phytoplankton biomasses generally remained low after 9 November 2005 (week 45).

Composition of the phytoplankton biomass and concentration of chlorophyll-a at Seebrücke Heiligendamm, GIF-Graphic=18,5 KB

Figure 3: Composition of the phytoplankton biomass and concentration of chlorophyll-a (curve) from 5 January to 20 December 2005 at Seebrücke Heiligendamm (surface samples).

Outer coastal waters of Mecklenburg-Vorpommern
During the special annual monitoring cruise in August, which was made to determine the algal and oxygen situation in the coastal waters of Mecklenburg-Vorpommern, no unusual concentrations of blue-green algae were observed because of the long spell of cold and rainy weather. The first signs of higher concentrations, which appeared as yellowish conglomerates of the filamentous blue-green algae Nodularia spumigena and Anabaena sp. on the water surface, were observed in the Greifswalder Bodden and Strelasund toward mid-August.

In early September, a strongly elevated chlorophyll-a value of 20.6 µg/L was found in the Pomeranian Bight, which was due to strong growth of blue-green algae and small flagellates. In October, chlorophyll levels in some areas, especially in the eastern parts of the Baltic, were markedly below the long-term means. The phytoplankton composition in the western coastal waters was characterised by typical autumn species, among which the Dinophyceae Ceratium tripos, C. fusus, Heterocapsa rotundata, and Prorocentrum micans were dominant, at single volumes of <0.1 to 1.8 mm³/L. Biovolumes in the eastern sea areas were clearly smaller (below 0.1 mm³/L), with an entirely different species spectrum: small flagellates of the genera Plagioselmis and Pyramimonas as well as cryptomonades of the genus Teleaulax marked the change to the typical winter species spectrum.

Inner coastal waters of Mecklenburg-Vorpommern
During the special annual monitoring cruise in August, which was made to determine the algal and oxygen situation in the coastal waters of Mecklenburg-Vorpommern, no unusual concentrations of blue-green algae were observed because of the long spell of cold and rainy weather. The first signs of higher concentrations, which appeared as yellowish conglomerates of the filamentous blue-green algae Nodularia spumigena and Anabaena sp. on the water surface, were observed in the Greifswalder Bodden and Strelasund toward mid-August.

In the inner coastal waters, chlorophyll-a concentrations in October ranged between 1.2 µg/L (Salzhaff) and 84.8 µg/L (Kleines Haff), where elevated values were measured from September through November. Also elevated regional biovolumes were found, with values ranging between <0,1 mm³/L in the Unterwarnow and 10 mm³/L in the waters of Kleines Haff.

In the Wismar Bight, up to 642,000 ind./L of the potentially toxic diatom Pseudonitzschia pungens were found, while the potentially toxic dinoflagellates Prorocentrum minimum and P. micans prevailed in the waters of Greifswalder Bodden. The dominant species in the waters of Kleines Haff in autumn were blue-green algae. The potentially toxic species Plankothrix agardhii and Aphanizomenon flos-aquae occurred at concentrations of up to 7.440.000 filaments/L.
A wide variety of potentially toxic filamentous Cyanophyceae was observed until mid-November.

Fish stocks

In bottom trawl surveys of demersal fish fauna, which were carried out in areas of high nature conservation interest off the German Baltic coast in June, the demersal species with the largest number of individual was dab, followed by cod, flounder, and whiting. The high abundance of plaice, especially west of the Odra Bank, was particularly noteworthy.

Within the framework of routine monitoring of the Institute for Fisheries Ecology concerning pollutant effects and fish diseases in marine fish, surveys were made in nine areas of the North Sea and four areas of the Baltic in August/September. The incidence of acute skin tumours in Baltic cod fluctuated between 0.0 % und 15.4 % in the four Baltic areas, and were thus higher than the year before.

Preliminary results of the bottom trawl survey in the Arkona Sea and Mecklenburg Bight in November confirmed the poor condition of adult cod stocks in the southwestern Baltic Sea. Especially the year classes 2004 and 2005 had to be classified as weak.

With regard to fishing opportunities and conditions in the Baltic Sea in 2006, the European Commission proposed in December that the catch quota for cod should be subject to certain restrictions in order to allow stocks to recover. Long-term plans for the recovery of stocks will be submitted to the European Council.

Besides, with respect to a simplification of fisheries regulations and measures within the framework of CFP, the Commission adopted an Action Plan covering the period from 2006 - 2008. The initiatives planned for the next three years are mainly aimed at maintaining stocks and monitoring fishing activities.

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 © 2016 Bundesamt für Seeschifffahrt und Hydrographie Last Update: 19.04.2013 17:59:56  
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