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In the framework of the ICON project (Integrated Assessment of Contaminant Impacts on the North Sea), muscle tissue from a total of 135 common dab ( Limanda limanda ) (20–28 cm total length) was collected in seven offshore sampling areas in the North Sea, at Iceland and in the Baltic Sea during Aug/Sept and December 2008 for a chemical mercury speciation analysis by means of gas chromatography and detection by cold vapour atomic fluorescence spectroscopy (GC-CVAFS). There was a highly significant correlation between concentrations of methylmercury (MeHg + ) and inorganic mercury (Hg 2+ ) in individual fish, and the mean ratio of MeHg + compared to Σ Hg (MeHg + + Hg 2+ ) was 94.0%. The results revealed statistically significant differences in concentrations of MeHg + and Hg 2+ , respectively, between sampling areas. Mean concentrations in the German Bight (North Sea), in Icelandic waters and in Mecklenburg Bight (Baltic Sea) were low (MeHg + : 0.023–0.036; Hg 2+ : 0.001–0.002 mg/kg wet weight), while concentrations in dab from the Dogger Bank, Firth of Forth and the vicinity of the Ekofisk oil field (all North Sea) were significantly higher (MeHg + : 0.059–0.101; Hg 2+ : 0.003–0.004 mg/kg wet weight). Statistical correlation analysis on effects of host-specific factors revealed that neither length, weight, age, sex nor condition factor showed a significant relationship with Hg concentrations. However, Hg concentrations were significantly correlated with the Fish Disease Index (FDI), indicating a relationship between Hg concentrations and the health status of dab. Multiple linear regression analysis aiming to find factors affecting Hg concentrations revealed that only the sampling area had a highly significant main effect on Hg concentrations, and in some cases, additionally the condition factor contributed significantly to the final model. From the results, it cannot be excluded that elevated Hg concentration recorded in dab were linked to discharges from offshore oil and gas installations and that Hg affected the health status of dab. [ABSTRACT FROM AUTHOR]

In the framework of the ICON project (Integrated Assessment of Contaminant Impacts on the North Sea), common dab ( Limanda limanda ) from seven offshore sampling areas in the North Sea, Icelandic waters and the western Baltic Sea were examined in 2008 for the presence of externally visible diseases and parasites (EVD), macroscopic liver neoplasms (tumours) (MLN) and histopathological liver lesions (LH). Methodologies applied followed standardised ICES and BEQUALM protocols. The EDV results revealed pronounced spatial variation, with dab from the central and northern North Sea sampling areas showing the highest disease prevalence. MLN were recorded only in North Sea dab from the German Bight, Firth of Forth and Ekofisk at a low prevalence. LH results revealed a dominant prevalence of non-specific, mostly inflammatory, lesions and a low prevalence of early toxicopathic non-neoplastic lesions, tumour pre-stages (foci of cellular alteration) and liver tumours. For the analysis and assessment of spatial variation of EVD, a Fish Disease Index (FDI) was calculated for individual dab, summarising data on the presence/absence of EDV, their severity grades, effects on the host and compensating for effects of length, sex and season. FDI data confirmed that the health status of North Sea dab from the offshore areas Dogger Bank, Ekofisk and Firth of Forth was significantly worse than in dab from the German Bight, Icelandic areas and the western Baltic Sea. An assessment of the disease data following ICES/OSPAR criteria was accomplished by applying established numeric background (BAC) and ecological assessment criteria (EAC) for EDV, MLN and LH. The combined assessment of the three disease categories indicated that health effects classified as unacceptable were rare and mainly affected dab from the North Sea. Based on the findings of the present study, it is recommended to monitor wild fish diseases in the context of assessing the impact of hazardous substances and other stressors on the marine environment. The Fish Disease Index (FDI) is regarded as a strong tool for disease data analysis and assessment, suitable as ecosystem health indicator. [ABSTRACT FROM AUTHOR]

Abstract: In the framework of the ICON project, environmental genotoxicity and cytotoxicity levels were assessed in blood erythrocytes of dab (Limanda limanda) and haddock (Melanogrammus aeglefinus) collected at 25 stations in the North Sea and near the coast of Iceland in August–October 2008. Micronuclei, nuclear buds and bi-nucleated cells with nucleoplasmic bridges were assessed as environmental genotoxicity biomarkers, and the frequency of fragmented-apoptotic and bi-nucleated erythrocytes were assessed as environmental cytotoxicity biomarkers. The lowest frequencies of genotoxic and cytotoxic abnormalities were detected in fish from the Icelandic study stations. The highest frequencies of abnormalities were recorded in dab from the Dogger Bank and the German Bight, in haddock from the Egersund Bank and from an area off the Firth of Forth (North Sea). In fish from the Icelandic reference area, frequencies of genotoxicity and cytotoxicity responses were significantly lower than in fish from most areas of the North Sea. [Copyright &y& Elsevier]

Abstract: Micronuclei (MN), nuclear buds (NB) and fragmented-apoptotic cells (FA) were analyzed in mature peripheral blood and immature cephalic kidney erythrocytes of flounder (Platichthys flesus), dab (Limanda limanda) and cod (Gadus morhua) from 12 offshore sites in the Baltic Sea (479 specimens) and 11 sites in the North Sea (291 specimens), which were collected during three research vessel cruises in December 2002, 2003 and in September 2004. The highest levels of environmental genotoxicity (frequencies of MN up to 0.5‰, NB – up to 0.75‰) and cytotoxicity (FA – up to 0.53‰) were observed in flatfishes from areas close to oil and gas platforms in the North Sea and in zones related to the extensive shipping and potentially influenced by contamination from large European Rivers (Elbe, Vistula, Oder). In dab from the offshore zones of the North Sea, the levels of nuclear abnormalities were higher as compared to those in dab from the Baltic Sea. Responses in immature kidney erythrocytes were higher than in mature erythrocytes from peripheral blood. MN frequency lower than 0.05‰ (the Baltic Sea) and lower than 0.1‰ (the North Sea) could be suspected as a reference level in the peripheral blood erythrocytes of flatfish. [Copyright &y& Elsevier]

The North Sea is a highly productive area with large fish populations that have been extensively harvested over the past century. North Sea fisheries remain important to the surrounding countries despite declining fish stocks over the past decades. The main reason for declining fish stocks is nearly certainly overfishing, but other environmental pressures also affect fish populations, such as eutrophication, climate change, and exposure to metals and organic pollutants, including polyaromatic hydrocarbons (PAHs), alkylphenols, and organochlorine compounds. There are three main sources of organic pollutants in the North Sea: atmospheric, land-based sources, and inputs from offshore gas and oil installations. All three sources contribute to elevated concentrations of organic pollutants in the North Sea compared to the Norwegian Sea. There is evidence that chlorinated organic contaminants were present in sufficiently high concentrations in the southern North Sea two decades ago, to alter embryonal development in fish. The results from extensive, long-term monitoring programs show that some diseases decreased whereas other increased in the southern North Sea and that, among other factors, contaminants may play a role in the temporal changes recorded in disease prevalence. Recent studies demonstrated that components in offshore effluents may affect fish reproduction and that tissues of fish near oil rigs are structurally different to tissues of fish from reference areas. Data on effluents from offshore activities have recently become available through an international workshop (BECPELAG) and follow-up studies.