MURSYS - North Sea and Baltic Sea - Report 2 2006





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MURSYS - North Sea and Baltic Sea - Report 2 2006

   
 
 

Marine Environmental Reporting System - Abstract - Reporting Period: 1 July - 31 December 2006

North Sea

Weather

The very warm month of July had monthly mean temperatures ranging from 19.6 to 21.8 °C, in some areas the highest July temperatures on record. The values of the 1961 - 1990 reference period were exceeded by 4 - 5 K. The dry spell continued; in North Friesland, only 20 - 30 mm rainfall was recorded (30 - 40 % of normal), and in Lower Saxony 50 - 70 mm (70 - 90 % of normal). The duration of sunshine in July, at 315 to 360 hours, was unprecedented and exceeded the monthly means by 50 - 70 %.
In August, monthly mean temperatures ranged between 16.4 °C (Ems estuary) and about 18 °C (Helgoland), the former slightly below and the latter about 1 K above average. Rainfall, at 150 - 200 mm (Helgoland 251 mm), was 2 - 3 times (Helgoland: 4 times) higher than usual. The duration of sunshine, at 123 - 190 hours, was 20 - 40 % below normal.
Monthly mean temperatures in September ranged from 17.0 to 18.5 °C, exceeding those of the 1961 - 1990 reference period by 3 - 4 K. With precipitation below 30 mm in most places, only 10 - 40 % of the monthly means was reached. The duration of sunshine was 180 - 210 hours, 30 - 40 % above the mean values.
Also October was 3 - 4 K too warm; at monthly mean temperatures of 13 to 14 °C, it was the warmest October on record. However, it was also too wet, with monthly totals of 80 - 120 mm; the monthly means were exceeded by up to 40 %. The duration of sunshine, at 80 to 90 hours, was 10 - 20 % below the mean values in most places.
With monthly mean temperatures of 9 °C - 10.5 °C, November set a temperature record for this month, at about 3 K above the reference means. Rainfall, at 70 - 90 mm in most areas, was up to 15 % below the mean values. At 35 - 60 hours of sunshine, values were up to 30 % below normal (coast of Lower Saxony) or up to 10 % above normal (East Frisian islands, North Friesland).
December, at monthly mean temperatures of 7 to 8.6 °C, was 4 - 5 K above the mean values of the reference series, setting a new record. Precipitation, at 50 - 70 mm, was up to 25 % below average (exception: North Friesland, which was 40 % above average, at 80 - 100 mm). The 20 to 30 hours of sunshine recorded were up to 20 - 30 % below normal (Helgoland up to 40 %).

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:

The mean SST in July was 16.0 °C, 1.7 K above the climatological mean and ranking third since 1971, after 1976 and 2003.
In August 2006, the mean SST, at 17.3 °C, was 2,2 K above the climatological mean, which corresponded to rank 4 (after 1997, 2002, and 2003).
Also September was 2.2 K too warm, at a monthly mean SST of 15.9 °C (rank 2, after 2002).
In the warmest October since 1971, the mean SST of 14.2 °C was 2.4 K above the climatological mean (rank 1).
November was 1.7 K above the climatological mean, occupying rank 2 (after 2005) at a mean SST of 11.4 °C.
In December, the mean SST still was as high as 9.5 °C, or 1.7 K above the climatological mean (rank 1).

Surface runoff

In the second half of 2006, the Elbe runoff volumes (Neu-Darchow gauge station) were slightly below (July, August, September) or markedly below (October, November) the runoff means of the 1926 - 2004 reference period. December runoff was only about 37 % of the mean value.
Also the rivers Weser (Intschede gauge station) and Ems (Versen gauge station) had runoff means that were clearly below those of the 1951 - 2004 reference period. Values measured in December were only 37 % and 51 %, respectively, of the mean runoff values.
The Rhine runoff (Rees gauge station) in September and October exceeded the mean values of the 1931 - 2004 reference series, but was up to 30 % below the reference values in the other months of the second half of 2006.

Ice conditions

In the 2006/2007 ice season, no ice had formed on the German North Sea coast by the end of December 2006.

Nutrients

By August 2006, phytoplankton had almost depleted nutrients in the surface water of the German Bight. Phosphate was still present at low concentrations of 0.04 to 0.2 µmol/L; nitrate levels in the central German Bight and Entenschnabel ("duck's bill") area were as low as 0.1 to 0.3 µmol/L. Higher nitrate and phosphate levels were found in the coastal waters and in the Elbe plume, attributable to riverine nutrient inputs and quick remineralisation in the well-mixed water column.
Above-average water temperatures in summer had supported the remineralisation process. Especially in the northeastern part of the German Bight, silicate levels exceeded those in the summer of 2005 by the factor 7 in places, and nitrate levels by up to the factor 10.

Oxygen

In August 2006, oxygen saturation in the bottom layer of large areas of the German Bight and in the Entenschnabel ("duck's bill") area was 80 to 100 %. However, only 60 % saturation was found at three stations northeast of the Elbe glacial valley.

Pollutants

2006 pollutant data are not yet available for the North Sea. They will be published later, possibly under the item "MURSYS-retrospective".

Phytoplankton

Coast of Lower Saxony

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

The diatom Pseudonitzschia sp. increased strongly from mid-July to the end of July, reaching local peak values of up to 88,000 ind./L.. From early August to early September, very high concentrations were observed which reached 240,000 ind./L. at individual stations. By the end of September, there was a dramatic decline in numbers, down to 1,200 to 6,300 ind./L.. At the beginning of October, Pseudonitzschia sp. once more increased up to 33.000 ind./L. at a few stations.
The non-toxic dinoflagellate Dinophysis rotundata occurred at the station Accumer Ee at the end of July, and in the river Jade (Alte Mellum) in mid-August, both with 100 ind./L.. In early September, the toxic dinoflagellate Dinophysis acuminata, which causes DSP (=Diarrhetic Shellfish Poisoning), increased slightly at the stations of Accumer Ee, Voslapp, and Alte Mellum (100 to 200 ind./L.), but disappeared by the end of September.
The scum forming alga Phaeocystis globosa, which belongs to the class of Prymnesiophyceae, occurred at clearly elevated concentrations of 97 colonies/L. in the Osterems in early July, but was hardly detectable by the end of July and remained unconspicuous until the end of the monitoring period throughout the area monitored.
Noctiluca scintillans (bioluminescent alga), a non-toxic heterotrophic dinoflagellate, reached 139 to 407 ind./L. at the beginning of July, after which it declined gradually to as few as 5 - 22 ind./L. in October.
The first appearance of the ciliate Myrionecta rubra was as late as the end of July, with elevated numbers of individuals (1,800 ind./L. in the river Jade). However, numbers decreased quickly until early September; maximally 100 - 200 ind./L. were found at various stations in August. In late September, numbers of individuals once more rose to 300 - 400 ind./L. at some stations, before Myrionecta rubra finally disappeared in the course of October.
Microflagellates of the genus Chrysochromulina sp. remained inconspicuous, with maximally 1,000 - 4,000 ind./L. at the majority of stations. Only in early August did Chrysochromulina sp. become slightly more abundant in the eastern part of the monitoring region, at up to 9,000 ind./L.; in early and late September, numbers of up to 7,000 ind./L. were counted locally in the eastern part of the coast and in the Osterems waters, respectively.

Helgoland Roads

In July, carbon production of phytoplankton was estimated at between 190 and 75 µg C/dm³. Abundant diatoms were Leptocylindrus danicus (maximum on 20.7. at 79.7 µg C/dm³), Pseudo-nitzschia seriata s.l., Rhizosolenia imbricata, Chaetoceros debilis, and other small Chaetoceros species (seasonal maximum of Chaetoceros socialis on 24.7. at 6.6 µg C/dm³). The carbon values of flagellates were higher due to the presence of unspecified small dinoflagellates (maximum on 31.7. at 7.2 µg C/dm³) and Ceratium fusus.
In August, phytoplankton reached levels between 25 and 120 µg C/dm³. The diatoms Guinardia delicatula, Pseudo-nitzschia seriata s.l., and Rhizosolenia hebetata semispina contributed substantially to carbon production; among flagellates, small dinoflagellates and Ceratium furca (maximum 16.2 µg C/dm³ on 7.8.) were temporarily abundant. Also Myrionecta rubra (maximum on 28.8. at 20.0 µg C/dm³) was observed.
In September, an increase in phytoplankton to 80 - 100 µg C/dm³ was observed in the middle of the month, the prevailing diatom species being Guinardia delicatula, Odontella sinensis, Chaetoceros debilis, and Eucampia zodiacus, and among flagellates Prorocentrum triestinum (maximum on 11.9. at 35.2 µg C/dm³).
In early October, phytoplankton stocks decreased to estimated values below 15 µg C/dm³, with a wide variety of different phytoplankton species but low numbers of cells and higher water temperatures than in 2005.

Phytoplankton, Helgoland Roads 2006

Species in comparison with preceding years:
(numbers of cells per dm³ are given for species that may occur at higher concentrations or in toxic variants)


Pseudo-nitzschia seriata s.l.: 2006: May - October, maximum 369,000 (3.7.).
2005: July - October, maximum 98,000 on 22.8..
2004: June - October in smaller numbers, maximum 7,600 (7.9.)
Ceratium furca:
2006: June - October, maximum 4,040 on 7.8..
2005: (July), August - October, maximum 2,300 (12.9.).
2004: July - October, up to 2,800 (22.9.)
Ceratium fusus:
2006: late April - June, August, September, maximum 2,900 (31.7.). Numbers smaller than in 2005.
2005: (March, April, May), June - July, (August, September), maximum 26,000 (11.7.) and
2004: July - October, up to 5,400 (3.8.).
Ceratium longipes (+ horridum):
2006: Few cells from April to September.
2005: July - September, maximum 360 on 12.9., numbers as low as in 2004
2004: Sept. - October, up to 280 (12.10.)
Dinophysis acuminata:
2006: May - October, maximum 1,160 on 12.6., more numerous than in 2005
2005: from May to October at moderate concentrations, maximum 360 on 22.8..
2004: (May, June) mid-August - October, maximum 640 on 24.8..
Noctiluca scintillans:
2006: End of May - early August, maximum on 24.7.: 972. More numerous than in 2005
2005: May - August (September), up to 312 (15.8.) and
2004: Maximum on 3.8.: 590.
Phaeocystis globosa:
2006: Mid-April - early October, maximum 723,000 (29.5.), less abundant than in 2005
2005: Maximum 1,526,000 on 7.6. and
2004: Maximum 10,493,000 on 11.5..
Prorocentrum micans:
2006: from late May - September, maxima 280 (6.6.), 1,320 (7.8.), and 1,500 (11+18.9.).
2005: June - September, Maximum 3 200 on 29.8..
2004: only August - October, not abundant.
Prorocentrum triestinum:
2006: Mid-July - September, maximum 88,000 on 11.9..
2005: less abundant (maximum 16,000 on 22.8).,
2004: only up to 320, on 28.9..
Raphidophyceae (species not determined):
2006: April - August, October, occurrence and days of maxima similar as in preceding years:
late April - early May (up to 371,000), but lower numbers
2005: April - October, maxima up to 646,000 on 10.5..
2004: April - October, much lower cell concentrations than in 2005, maximum on 4.5.: 38,000.
Myrionecta rubra:
2006: As in 2005 throughout the survey period March - October. Maxima: 9,200 (19.6.), 5,700 (3.7.), 10,000 (28.8.) and 8,400 (4.9.), lower numbers than in 2005
2005: Maxima 8,300 (3.5.) and 27,400 (28.6.).
2004: less abundant, up to 11,400 (10.8.)

Phytoplankton 2006 in selected samples from Helgoland Roads station, GIF-Graphic=13,8 KB

Figure 1: Phytoplankton 2006 in selected samples from Helgoland Roads station ( µg C/dm³ estimated on the basis of counts)
(Data compiled by Biologische Anstalt Helgoland der Stiftung Alfred Wegener Institut für Polar- und Meeresforschung, with funding from Landesamt für Natur und Umwelt des Landes Schleswig-Holstein)

North Sylt Wadden Sea

The 2006 seasonal cycle of phytoplankton biomass showed a normal spring bloom which reached its maximum on 10 April, with the diatom Odontella aurita the dominant species. The typical Phaeocystis bloom which usually the spring bloom of diatoms was not clearly visible this year. From mid-May to mid-June, a second diatom bloom was observed, with Cerataulina pelagica and Helicotheca tamesis the dominant species.
In the course of summer, Rhizosolenia imbricata was the dominant phytoplankton species. Phytoplankton in autumn was characterized by a very high species diversity.The maximum (63 diatom species, 31 dinoflagellate species) was reached in mid-October.
Potentially toxic algae (Alexandrium, Dinophysis, Chattonella, Gymnodinium) occurred several times, but at low cell concentrations. Dinophysis acuminata was observed almost continuously from early May to early July, and from late August to the end of September. Dinophysis rotundata was present almost continuously from the end of May to early July. Summer levels of nutrients were in the normal range: (Si: 0 - 5 µM; NO3: 0 - 1 µM; NH4: 0 - 4 µM). PO4 remained low until early July (about 0 - 0.2 µM) and reached its maximum values exceeding 1 µM in late July.
Remarkable occurrences this year were the long growth season, which lasted until October, a very late autumnal increase in nutrient levels (late October/early November), and the unusually high autumn and December temperatures.

Seasonal cycle of phytoplankton biomass, GIF-Graphic=5,58 KB

Figure 2: Seasonal cycle of phytoplankton biomass (chlorophyll a, µg/L)
(Data compiled by Alfred Wegener Institut für Polar- und Meeresforschung, Wattenmeerstation Sylt)

Schleswig-Holstein coastal waters

In early July, higher concentrations of the scum producing alga Phaeocystis globosa were observed nearly everywhere, followed by a marked decrease toward the end of the month; the Red Tide producing dinoflagellate Noctiluca scintillans decreased as well. Phytoplankton generally was distributed heterogeneously, the largest spectrum of species being observed south of Eiderstedt, with a conspicuous decrease in northward direction. Phaeocystis globosa and Noctiluca scintillans continued to decrease in early August. In the waters south of Eiderstedt and toward Helgoland, the diatom genus Pseudonitzschia was rather abundant, and near the North Frisian islands the species Rhizosolenia imbricata.

Fish stocks

During a hydroacoustic survey of pelagic fish stocks in the North Sea in June/July, 15 fish species were caught, the most abundant of which were sprat (86 % by weight of total catch), herring (11 %), grey gurnard, and mackarel.
Monitoring of bottom fish stocks in the North Sea in July/August showed that there were no increases in the recruiting year-class strengths of whiting, haddock, and particularly cod. A positive trend was found for Norway pout.
In August 2006, during this year's so-called box fisheries, catches in the German Bight and off the Danish coast were found to have decreased by 17 % and nearly 50 %, respectively, whereas the third largest catch per unit effort in the 15-year time series was recorded in the central North Sea. Dab was among the prevailing species in all areas.
According to the results of the qualitative and quantitative survey of demersal fish fauna in the German EEZ (Exclusive Economic Zone) in November/December, grey gurnard and dab were the most abundant species, whereas only small numbers of cod, haddock, and whiting were present.
In the course of long-term health monitoring for diseases and parasites in marine fishes, the preceding year's findings concerning macroscopic diseases in dab from the North Sea and western Baltic Sea were confirmed in December 2006. In the German Bight, a further increase in prevalences of hyperpigmentation of the skin (as in the past 10 years) and of liver nodules was observed. Prevalences of other regularly occurring diseases in dab (such as lymphocystis, epidermal hyperplasia/papilloma, skin ulcers) were at a relatively low level.
With regard to 2007 catch quota, ACFM (Advisory Committee for Fisheries Management) of the International Council for the Exploration of the Sea (ICES) had recommended in December 2006 that cod fishing in the North Sea should be banned, and catches of sole and plaice should be reduced. It had allowed higher catches of Norwegian spring-spawning herring.

Baltic Sea

Weather

July 2006 was the warmest July on record, with the highest number of sunshine hours. Monthly mean temperatures ranged between 21 and 22 °C, exceeding the mean values by about 5 K. The dry spell continued. At 6 to 40 mm rain, not even half the monthly means was reached. The duration of sunshine, at 340 to 390 hours, set new records in many areas, and the monthly means were exceeded by 50 to 70 %.
Although August was 3 - 4 K colder than the exceptionally hot July, the mean temperatures of 17 - 18 °C still were up to 1.5 K above those of the 1961 - 1990 reference period. Despite a dry first decade, rainfall in August reached 90 to 190 mm, which was twice to three times higher than the monthly means in most areas. At 220 hours of sunshine, values at Fehmarn were just below normal, whereas the 146 hours measured at Kleines Haff were nearly 40 % below the long-term mean.
September, at monthly mean temperatures of 17 - 18 °C, was 3 - 4 K too warm. With rainfalls ranging from 25 mm (Kleines Haff) to 62 mm (Rügen/Hiddensee), precipitation was up to 50 % below the monthly means or exceeded it by some 20 %. At 200 - 240 hours of sunshine, the monthly means in most areas were exceeded by 30 to 40 %.
New temperature records were set in October, when monthly mean temperatures between 12.5 and 13,6 °C caused long-term reference values to be exceeded by 3 - 3.5 K. Rainfall in many areas reached 40 to 50 mm, and up to 90 mm in the western part of the Baltic coast, which was up to 40 % above the monthly means. The recorded 80 - 100 hours of sunshine were up to 15 % below the long-term means; east of Rügen, 100 - 110 hours of sunshine were recorded, which was above normal in some areas.
Heat records were reached in November 2006. At 7 - 9 °C, monthly mean temperatures were up to 3 K above the mean values of the 1961 - 1990 reference period. Precipitation ranged between 50 and 70 mm, which was on the order of the mean values or up to 50 % above them. The duration of sunshine, at 45 - 60 hours, corresponded to the long-term means. Normal values were only exceeded in the area of Kleines Haff, by up to 40 %, where 70 hours of sunshine was recorded.
Monthly mean temperatures in December, at 6 - 7 °C, were 4 - 5 K above the long-term reference values and exceeded the record values of December 1974 by about 1 K. Precipitation mostly was 20 to 40 mm, and at the coast of Schleswig-Holstein up to 66 mm, which was up to 50 % below the mean values. At only 30 - 40 hours of sunshine on the coast of Schleswig-Holstein, values were below normal, whereas they were 10 bis 20 % above normal on the coast of Mecklenburg-Vorpommern.

Water temperatures

Water temperatures (at 3 m depth) at the coast of Mecklenburg-Vorpommern, off Warnemünde and Koserow, averaged 20.2 °C in July, which was 2.7 and 0.4 K, respectively, above the values of the 1997 - 2006 reference series. Also the maximum values were exceptionally high.
In August, water temperatures at these two stations were 20.2 and 20.0 °C, respectively, which was 2.2 and 0.9 K above the values of the reference series.
In September, water temperatures at 3 m depth in Warnemünde and Koserow were 17.4 °C and 17.1 °C, respectively, which was 1.5 K and 0.5 K above the reference values.
At 15.0 and 14.3 °C, respectively, the mean water temperatures in October were more than 2 K above the reference values at both stations.
In November, water temperatures of 9.8 and 7.9 °C were measured at the two stations, which was 1.7 and 0.7 K above their respective reference values.
Also in December, the mean water temperatures of 7.6 and 6.5 °C, respectively, at the two stations exceeded their reference values by almost 3 K.

Water levels

In July, mean water levels at the Baltic coast of Schleswig-Holstein and Mecklenburg-Vorpommern were up to 11 cm (Koserow) below the values of the reference series (Schleswig-Holstein: 1991 - 2000; Mecklenburg-Vorpommern: 1995 - 2004). The lowest levels, 460 cm in Flensburg and 468 cm in Wismar, were measured on 10 July, and the highest levels, 545 cm in Lübeck and 536 cm at the Greifwalder Bodden station on 15 July.
Mean water levels in August were 2 to 4 cm above the reference values. The lowest water level was recorded in Flensburg, at 441 cm, on 15 August, and the highest levels of 555 cm and 564 cm were measured in Wismar and Lübeck, respectively, on 5 August.
In September, the monthly mean water levels were up to 6 cm above the values of the reference series. The lowest level of 443 cm was recorded in Flensburg on 4 September, and the highest level of 577 cm at the Schleswig gauge station on 16 September.
The monthly means in October were up to 4 cm above the reference series. Here, too, the lowest level of 375 cm was recorded at Flensburg, on 27 October, as was the maximum level of 602 cm measured on 29 October.
In November, the mean water levels in Schleswig-Holstein (Travemünde) and Mecklenburg-Vorpommern (Koserow) were 11 cm and 21 cm, respectively, above the values of the reference series. The lowest value of 426 cm was recorded in Flensburg on 1 November, and the highest values of 684 cm and 654 cm were measured on 1 November in Schleswig-Holstein (Heiligenhafen) and Mecklenburg-Vorpommern (Koserow/Usedom), respectively.
Also in December, monthly mean water levels exceeded the reference values, in Kiel by 3 cm, in Koserow by 14 cm. The minimum level of 402 cm was recorded in Wismar on 11 December, and the highest level of 569 cm in Koserow on 20 December.

Surface runoff

In July 2006, the runoff volume of the Odra (Hohensaaten-Finow gauge station) reached only about 53 % of the values of the 1941 - 2004 reference period. In the other months of the second half of 2006, the values were 10 - 27 % below the mean values.

Ice conditions

The first ice of this winter season formed during the first days of November at the northern coast of the Bay of Bothnia, about one week earlier than average. In the 47th calendar week, ice formation was interrupted by a spell of warm weather, and by Christmas only the inner archipelago of the northern Bay of Bothnia was covered with ice. It was not until the 52th calendar week that new ice formation continued in the northern Bay of Bothnia and easternmost part of the Gulf of Finland. The beginning of the 2006/2007 ice season thus was the latest on record.

Nutrients

Nutrient levels in the bottom water of the area extending from Kiel Bight to the northern Gotland Basin in July reflected the current stagnation phase. Concentrations of phosphate, silicate, and ammonium in the anoxic layers had continued to increase since May 2006 and since the preceding year; nitrate was not present. Nutrient levels in the surface water had their seasonal low.
By November, slightly oxic conditions in the bottom layer of the Bornholm basin had caused nitrate levels to rise again. West of Darss Sill, nutrient levels in the surface water had already increased, also in the Landsort and Karlsö Deeps, but were relatively low in the central Gotland Sea.

Oxygen

In July, in the area extending from Kiel Bight to the northern Gotland Basin, the deepwater oxygen situation was found to have further deteriorated. Both the concentration and vertical spread of hydrogen sulphide had increased since May. Also in the Bornholm Deep, hydrogen sulphide was found in the bottom water in July; however, the situation in the area improved toward November at oxygen concentrations below 1 ml/L. The Landsort and Karlsö Deeps remained anoxic below 70 m depth, and hydrogen sulphide occurred below 90 - 100 m. In the Farö Deep, hydrogen sulphide was found below 80 m depth. Intrusions of H2S free, slightly oxic water were found within the anoxic water mass of the Farö Deep and Gotland Basin.
West of Darss Sill, low oxygen values below 2 ml/L were found only in the Lübeck Bay.

Pollutants

2006 pollutant data for the Baltic Sea will be published under the item: "MURSYS-retrospective".

Phytoplankton

Baltic coast of Schleswig-Holstein

After an increase in cell concentrations of filamentous blue-green algae had been observed in early July, westerly winds toward the end of the month reduced them to mostly low to normal seasonal levels. In the inner Baltic fjord waters, diatoms prevailed but elevated cell concentrations of flagellates and dinoflagellates were observed as well.

On the first weekend in August, high concentrations of blue-green algae (mainly Nodularia spumigena and Aphanizomenon) occurred off Travemünde and Heiligenhafen, but just a few days later water samples showed low concentrations. Diatoms and dinoflagellates had decreased markedly. Small flagellates were locally abundant.

Monitoring station "Seebrücke Heiligendamm"

In early July, numbers of Dictyocha speculum and Ceratium tripos increased, and by 17 July a bloom of Anabaena sp. had formed which was gradually replaced by Nodularia spumigena by the end of July.
In 2006, blooms of cyanobacteria were particularly strong but showed considerable regional differences in intensity. In north-west Mecklenburg, bathing was prohibited at several beaches in mid-August; strong blooms also occurred in the waters off Warnemünde.
Off Heiligendamm, blooms were weaker. Here, Ceratium tripos and Plagioselmis prolonga, and for a short time Coscinodiscus granii, prevailed in mid-August. The summer peak of phytoplankton biomass was recorded on 29 August, at 1,732 mg/m³, the bulk being unspecified algae.
By 12 September, the species spectrum had changed, with Ceratium fusus and Ceratium tripos prevailing besides Coscinodiscus granii, but also Proboscia alata and Cerataulina pelagica were present. At the end of September, both biomass and abundances decreased sharply. Ceratium and diatoms all but disappeared, and Cryptophyceae (Teleaulax spp., Plagioselmis prolonga) prevailed. From early October, the dominant algae were Ceratium tripos (during water inflow from the Belt Sea) and Coscinodiscus granii (water outflow into the Belt Sea).

Composition of phytoplankton biomass and concentrations of chlorophyll a, GIF-Graphic=17,4 KB

Figure 3: Composition of phytoplankton biomass and concentrations of chlorophyll a between 3.1. and 23.10.2006 at Seebrücke Heiligendamm (surface water samples)
(Data compiled by Leibniz-Institut für Ostseeforschung, Warnemünde)

Coastal waters of Mecklenburg-Vorpommern

In the second half of the year, special monitoring for blue-green algae was carried out in some areas of the coastal waters of Mecklenburg-Vorpommern.
In late July, in the waters off Sassnitz and north of Cape Arkona, the cynobacteria Nodularia spumigena, sporadically also Anabaena sp. and Aphanizomenon flos-aquae, were observed on the water surface without, however, forming any blooms.
Satellite images also showed elevated levels of cyanobacteria in the coastal waters between Warnemünde and Dierhagen, off Hiddensee and Usedom.
During sampling in the Pomeranian Bight, the formation of blue-green algal mats (Nodularia spumigena and Aphanizomenon flos-aquae) was observed in the process. Also in the Lower Warnow, these Cyanobacteria were observed on the surface, but there was no floc formation.
Around 9 August, only few filamentous blue-green algae (e.g. Nodularia spumigena, Anabaena spp., and Aphanizomenon flos-aquae) were observed in the sea area of the northern Rügen bodden waters, with coccoid algae prevailing (Microcystis aeruginosa/ Microcystis flosaquae) but without any formation of algal mats. Among the typical seasonal range of plankton, Prorocentrum micans, Coscinodiscus, Wronichinia spp., and Merimopedia were the prevailing species.
In mid-August (sampling of the sea area between Warnemünde and Hiddensee), hardly any Cyanophyceae were observed at the monitoring site off Warnemünde. In the waters between Darsser Ort and Zingst, Nodularia spumigena and Aphanizomenon flos-aquae were the dominant species forming algal mats in some places; north-west of Hiddensee, Nodularia spumigena prevailed.
The waters of the Wismar Bight were sampled on 23 August, with abundant Nodularia spumigena found only in the outer waters. Algal mats were observed northwest of Poel, and accumulations of blue-green algae were identified on satellite images of the sea area extending from Fehmarn to Hiddensee/Rügen.
At the end of August, sampling was carried out in the Pomeranian Bight, Szczecin Lagoon, and Greifswalder Bodden. In the waters of Szczecin Lagoon, blue-green algae such as Aphanizomenon flos-aquae, Microcystis flosaquae/Microcystis aeruginosa formed smears on the water surface. In the Greifswalder Bodden, Aphanizomenon flos-aquae prevailed although major accumulations occurred only in the inner waters. Also in the Pomeranian Bight, Aphanizomenon flos-aquae was the dominant alga. Off Rügen, Nodularia spumigena was the only potentially toxic blue-green alga observed.

Fish stocks

Integrated monitoring of marine fishes carried out in nine North and Baltic Sea regions in August/September included examinations of dab, Baltic Sea cod and flounder for visible macroscopic signs of external and internal diseases. Last year's trend found for macroscopic diseases in dab was largely confirmed. A slight increase in the prevalence of lymphocystis was found both in the North Sea and Baltic Sea. A marked increase in the prevalence of liver nodules was observed in the North Sea. Prevalences of hyperpigmentation continued to be high in the North Sea but had clearly decreased from the preceding year in the German Bight.
The prevalence of acute skin ulcers in Baltic cod ranged from 0.0 to 11.9 % in the four areas, comparable to last year's results.
December monitoring of fish diseases in the North and Baltic Seas largely confirmed last year's trend for macroscopic diseases in dab in the North Sea and western Baltic, but in the German Bight an increase in the prevalences of skin hyperpigmentation and liver nodules was observed. Other diseases like, e.g., lymphocystis, epidermal hyperplasia/papillomas, skin ulcers were at relatively low levels. The prevalences of acute skin ulcers and skeletal deformation in Baltic cod were comparable to those found in the preceding years.

In October, the EU Fisheries Council decided to reduce the catch quota for the eastern and western cod stocks by 10 and 6 %, respectively. Also the catch quota for salmon were reduced slightly, whereas somewhat higher quota were decided for sprat and herring. Catch quota for plaice have been unchanged.
Monitoring of pelagic fish stocks in the Arkona Sea, the Belts, Sound and Kattegat in October using hydroacoustic methods showed that sprat in the western Baltic had almost tripled in comparison with the long-term mean, with an extremely strong current recruiting year class. Herring stocks in the western Baltic corresponded to the average.
The ground trawl survey in the Arkona Sea and Mecklenburg Bight in November 2006 confirmed the poor condition of cod stocks. Local catches of plaice, flounder stocks, and the situation of dab gave rise to optimism.

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 © 2016 Bundesamt für Seeschifffahrt und Hydrographie Last Update: 19.04.2013 18:00:01  
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