DCE - Nationalt Center for Miljø og Energi

Aarhus Universitets segl
Du er her: DCE - Nationalt Center for Miljø og Energi Udgivelser Tidligere udgivelser Danmarks Miljøundersøgelser Faglige rapporter Nr. 800-849 Abstracts No. 800: The marine environment 2009. NOVANA. Status and developments in environmental quality

No. 800: The marine environment 2009. NOVANA. Status and developments in environmental quality

Petersen, D.L.J. & Hjorth, M. (red.) 2010: Marine områder 2009. NOVANA. Tilstand og udvikling i miljø- og naturkvaliteten. Danmarks Miljøundersøgelser, Aarhus Universitet. 127 s. - Faglig
rapport fra DMU nr. 800.

Summary

The environmental status of Danish marine waters in terms of the status of algae, water transparency (Secchi depth) and other important parameters has generally not improved during 2009 compared to previous years. The lowering of nutrient concentrations in our waters has not led to the expected improvement of environmental conditions. Air and sea temperatures in 2009 were higher than normal during most of the year, but at a comparable level to the average of the last 10 years. Oxygen conditions in 2009 were a little better than the average of the previous years. The nationwide status of the Danish marine environment can be summarised in the following points:

Climate and hydrography

  • The year 2009 was very sunny, relatively warm and with weak winds during the winter.
  • Freshwater run-off was 15 % below normal, and the year can be categorised as relatively dry.
  • Temperatures were higher than normal in 9 out of 12 months, but the year was not particularly warm compared to the last 10 years.
  • April was unusually hot and sunny, whereas June, October, and December were relatively cold.
  • Sea temperatures have increased by 1.5°C during the last 40 years.
  • Irradiation was generally high in 2009 and has been increasing during the summer period in the last 10 years.
  • Acidification of the marine waters has increased over the last 25 years.
  • Surface water in the inner Danish waters is increasing in alkalinity, probably caused by an increased export of alkaline water from the Baltic Sea water sheds.

 Nutrient loads and concentrations

  • When variations in fresh water run-off are taken into consideration, nitrogen and phosphorus loads have been decreasing since 1990. However, there is a tendency of stagnation in phosphorus loads after 1997. Nitrogen and phosphorous loads to inner Danish waters in 2009 were lower than normal because of a reduced freshwater run-off.
  • Nutrient concentrations in 2009 were generally low, especially nitrogen concentrations. A relatively large run-off from land in November and December increased nutrient concentrations to similar levels as in previous years.
  • The influence of water masses from the Jutland coastal current on the inner Danish waters has probably been insignificant in 2009.
  • Nitrogen and phosphorus concentrations have shown a clear decrease since 1989, especially when data are adjusted with year to year variations in freshwater run-off. However, there is a tendency of stagnation in phosphorus concentrations after 1997, and a similar stagnation in nitrogen concentrations after 2002.
  • These results have to a large degree been attributed to waste water treatment with regard to phosphorus (VMP I), and to reductions in agricultural nitrogen surplus (VMP I and II) with regard to nitrogen. There is a positive effect of the Danish effort. Similar initiatives in our neighbouring countries may have contributed to the lower concentrations in open waters. DIN levels in water masses from the Jutland costal current have been reduced considerably through the years as a result of reduced loadings from central European rivers.
  • Model studies from three Danish fjords indicate that reductions in total nitrogen are mainly caused by reductions in the fraction of dissolved inorganic nitrogen, while the dissolved organic nitrogen fraction only drops slightly and the particular fraction remains unchanged.
  • The potential phosphorus limitation has decreased during recent years in fjords and coastal areas as well as in open waters.

Phytoplankton and water clarity

  • The average climate corrected water clarity (Secchi depth) in 2009 was 6.9 m in open waters and just above 4.2 m in fjords, which are improvements compared to 2008 with 0.3 and 0.2 m, respectively. However, the climate corrected water clarity is still characterised by a significant fall since 2001 (P < 0.05) in all areas.
  • Water clarity was high in July with 8.4 m in open waters. At this time, primary production was remarkably low.
  • In general, chlorophyll a concentrations were low in the fjords from April and throughout the year, with values almost 1 µg l-1 below the average concentration. In 2009, the average chlorophyll concentration in the fjords reached 2.8 µg l-1, which is the lowest level recorded, for the second year in a row.
  • In open waters the spring bloom occurred early in 2009 and led to an unusually high chlorophyll concentration of approx. 5 µg l-1 in February, which also was characterised by low water clarity and a high primary production.
  • The primary production in the open waters increased during the spring bloom in February, and the highest measured production in April of 444 mg C m-2 d-1.
  • In open waters, there were remarkably low primary production rates in June and July of 455 and 480 mg C m-2 d-1, respectively.
  • In the last 2 years, primary production in the open waters has peaked in September, which is approximately 2 months later than the average since 1998.
  • The primary production in the fjords followed a cycle close to normal, although with slightly lower rates from August to October.
  • In 2009, high concentrations of two groups of potentially fish toxin producing planktonic algae were recorded: ’Chattonella sp.’ (= Pseudochattonella farcimen) and the genus Chrysochromulina.
  • There were low abundances of dinoflagellates of the genus Dinophysis, known to produce toxins, which through accumulation in mussels can cause shellfish poisoning.

Oxygen deficiency

  • The amount of oxygen deficiency in 2009 in the inner Danish waters was less than the average for the period 2003-2007 and at the level of 2008.
  • The duration of oxygen deficiency was shorter and of lesser extend than in 2008, partly due to frequent events of strong winds which enhanced mixing.
  • The largest coverage of oxygen deficiency was observed in September, after which conditions improved gradually.
  • The area affected by severe oxygen deficiency during 2009 was similar to 2008.
  • Particular affected areas in 2009 included Limfjorden, the archipelago south of Funen, the south-western Belt Sea, Aabenraa Fjord and Flensborg Fjord. In several of these areas oxygen concentrations remained critical for 3 months and thus damage to bottom fauna and flora is expected. Furthermore, development of toxic hydrogen sulphide was observed several times.

Bottom flora and fauna

  • Through the period 1989-2009 the main abundance of eel grass moved to deeper waters in the outer fjords. In contrast, the maximum depth limit became lower in the inner fjords, and eel grass covered generally less of the sea floor both in shallow water (1-2 m) and in medium depths (2-4 m) in the fjords and in shallow areas of open waters. The decrease in nutrients has not yet substantially improved eel grass conditions in our waters, which may be linked to the lack of water clarity improvement.
  • The total algal cover in the deeper parts of selected stone reefs in the open parts of Kattegat was generally lower than the average for the period 1994-2001, it was, however, not significant. Grazing of macroalgae by sea urchins is still a problem on many reefs in the Belt Sea.
  • There has been a marked drop in bottom fauna biodiversity in many areas of the open waters during 1994-2008. The development in 2009 is unknown due to lack of data.
  • The limited data material from 2009 – both in open waters and fjords and coastal areas – makes it difficult to asses if previously documented negative trends in bottom fauna parameters have continued.
  • A marked deterioration of bottom fauna has been observed locally in Isefjord and Roskilde Fjord. The cause is unknown, since the common stress factor, oxygen deficiency, is absent.
  •  
  • The metal contents in mussels and fish were close to background levels of zinc (Zn) and cadmium (Cd).
  • Lead (Pb) in fish was below detection limits and close to background levels; in mussels 2/3 of the samples were close to background levels. Concentrations above EU limits were only found for Pb in mussels.
  • The contents of mercury (Hg) were at background levels in 2/3 of the mussel samples and in < 1/3 of the fish samples.
  • The highest Cu concentrations were found in soft clams from Ringkøbing Fjord.
  • OSPAR and HELCOM assessments in 2010 indicate metals as the reason why convention goals of background levels cannot be reached.
  • Imposex and intersex in whelks, caused by pollution of the antifouling substance TBT, are still widespread and present an environmental problem in Danish waters. Based on OSPAR environmental quality classification of imposex and intersex, a general good environmental status can only be achieved in the North Sea and the Skagerrak. Levels of imposex in the inner Danish waters are so high, that the environmental status must be regarded as either unsatisfactory or bad around certain polluted harbours and docks. The levels have been falling significantly during recent years, indicating further improvement of the environmental status in this regard.
  • Investigations of lysosomal membrane stability in blue mussels indicated that approximately 50 % of the investigated coastal areas were affected by hazardous substances, and these effects could be related to increased levels of compounds such as PAHs and PCBs.
  • Investigations of eelpout showed notable differences in the degree of effects between areas, both concerning the presence of maldevelopment in fry and CYP1A enzyme activity. The highest effect levels were observed in fjords with a high impact from urban and industrial areas. Endocrine disruptions are also widespread in eelpouts from Danish waters. More chemical and biological investigations of eelpout and their reproduction are needed to identify the compounds causing the observed effects.
  • Levels of PCB-118 and PCB-180 were above EAC in 33 % and 83 % of fish liver samples, indicating possible effects of PCB pollution in fish in the Sound, the Baltic Sea and the Great Belt. In sediments, most of the PCB concentrations were below levels expected to have an environmental effect (ERL), but especially PCB-118 was found in concentrations above ERL in several areas. The compound was also found above OSPAR assessment criteria (EAC) in mussels from Kattegat. In mussels from several fjords, the Wadden Sea and the southwest Belt Sea, PCB-118 was found in concentrations above ERL.
  • There were no PAHs in concentrations above EAC in mussels, and no effects are to be expected on mussels in Danish waters. In contrast, concentrations in sediments were above ERL in several cases. Especially benz(a)anthracene, pyrene and chrysene/triphenylene were above ERL, but patterns were different between stations. There was no connection between mussel and sediment PAH contents, since sediment contents are expected to reflect the latest 3-10 years of impact, where mussel contents are the result of a more recent (< 1 year) impact.
  • TBT was found above EAC in 66 % of samples, which means there can still be effects of TBT on mussels in Danish waters. In certain areas TBT concentrations were too high for the mussels to be suitable for human consumption.
  • OSPAR and HELCOM status reports show that concentrations of TBT, PCB and PAH have generally been falling through the last 5-10 years, but the environmental status of the inner Danish waters are judged to be ’moderate’ (few places in Kattegat are ’good’), Odense Fjord and Limfjorden are ’poor’, and the western Baltic is ’poor’-’very poor’.
  • In 2008/2009 screenings of chlorinated alkanes were made in sediments and methylmercury and hexachlorobutadiene (HCBD) in biota. Chlorinated alkanes were measured in both marine and freshwater sediments. In all cases concentrations were below the EU water quality criteria (EQS). HCBD was not found in mussels, fish, otters, seals or cormorants and the detection limit was below EQS. Methylmercury was found in all mussel samples in concentrations below EQS, but above EQS in fish and top predators. The main part of mercury in fish, otters, and seals was in a methylated form, where only a third of the mercury in mussels and cormorant was methylated.

Environmentally hazardous substances

  • The metal contents in mussels and fish were close to background levels of zinc (Zn) and cadmium (Cd).
  • Lead (Pb) in fish was below detection limits and close to background levels; in mussels 2/3 of the samples were close to background levels. Concentrations above EU limits were only found for Pb in mussels.
  • The contents of mercury (Hg) were at background levels in 2/3 of the mussel samples and in < 1/3 of the fish samples.
  • The highest Cu concentrations were found in soft clams from Ringkøbing Fjord.
  • OSPAR and HELCOM assessments in 2010 indicate metals as the reason why convention goals of background levels cannot be reached.
  • Imposex and intersex in whelks, caused by pollution of the antifouling substance TBT, are still widespread and present an environmental problem in Danish waters. Based on OSPAR environmental quality classification of imposex and intersex, a general good environmental status can only be achieved in the North Sea and the Skagerrak. Levels of imposex in the inner Danish waters are so high, that the environmental status must be regarded as either unsatisfactory or bad around certain polluted harbours and docks. The levels have been falling significantly during recent years, indicating further improvement of the environmental status in this regard.
  • Investigations of lysosomal membrane stability in blue mussels indicated that approximately 50 % of the investigated coastal areas were affected by hazardous substances, and these effects could be related to increased levels of compounds such as PAHs and PCBs.
  • Investigations of eelpout showed notable differences in the degree of effects between areas, both concerning the presence of maldevelopment in fry and CYP1A enzyme activity. The highest effect levels were observed in fjords with a high impact from urban and industrial areas. Endocrine disruptions are also widespread in eelpouts from Danish waters. More chemical and biological investigations of eelpout and their reproduction are needed to identify the compounds causing the observed effects.
  • Levels of PCB-118 and PCB-180 were above EAC in 33 % and 83 % of fish liver samples, indicating possible effects of PCB pollution in fish in the Sound, the Baltic Sea and the Great Belt. In sediments, most of the PCB concentrations were below levels expected to have an environmental effect (ERL), but especially PCB-118 was found in concentrations above ERL in several areas. The compound was also found above OSPAR assessment criteria (EAC) in mussels from Kattegat. In mussels from several fjords, the Wadden Sea and the southwest Belt Sea, PCB-118 was found in concentrations above ERL.
  • There were no PAHs in concentrations above EAC in mussels, and no effects are to be expected on mussels in Danish waters. In contrast, concentrations in sediments were above ERL in several cases. Especially benz(a)anthracene, pyrene and chrysene/triphenylene were above ERL, but patterns were different between stations. There was no connection between mussel and sediment PAH contents, since sediment contents are expected to reflect the latest 3-10 years of impact, where mussel contents are the result of a more recent (< 1 year) impact.
  • TBT was found above EAC in 66 % of samples, which means there can still be effects of TBT on mussels in Danish waters. In certain areas TBT concentrations were too high for the mussels to be suitable for human consumption.
  • OSPAR and HELCOM status reports show that concentrations of TBT, PCB and PAH have generally been falling through the last 5-10 years, but the environmental status of the inner Danish waters are judged to be ’moderate’ (few places in Kattegat are ’good’), Odense Fjord and Limfjorden are ’poor’, and the western Baltic is ’poor’-’very poor’.
  • In 2008/2009 screenings of chlorinated alkanes were made in sediments and methylmercury and hexachlorobutadiene (HCBD) in biota. Chlorinated alkanes were measured in both marine and freshwater sediments. In all cases concentrations were below the EU water quality criteria (EQS). HCBD was not found in mussels, fish, otters, seals or cormorants and the detection limit was below EQS. Methylmercury was found in all mussel samples in concentrations below EQS, but above EQS in fish and top predators. The main part of mercury in fish, otters, and seals was in a methylated form, where only a third of the mercury in mussels and cormorant was methylated.

Full report in PDF-format (5,79 MB).

Revideret 12.09.2023