Elevated mercury concentrations in biota despite reduced sediment concentrations in a contaminated coastal area, Harboøre Tange, Denmark.

Metals sequestered in coastal sediments are normally considered to be stable, but this investigation shows - somewhat surprisingly - that mercury concentrations in a previously contaminated area, Harboøre Tange, Denmark, have decreased since the 1980s. Mercury concentrations were determined in sediment and benthic biota and present values were compared to values in the 1980s and values from areas without known; history of mercury contamination. Concentrations in both the upper 20 cm of the sediments and; biota are considerably lower now compared to latest monitoring (1980s). Sediment. concentrations at most locations have decreased from the 100-300 ng Hg g-1 dry weight (dw) level to levels below the Background Concentration (BC) of 50 ng Hg g-1 dw defined by Oslo-Paris Convention for the Protection of the Marine Environment of the North-East Atlantic; some stations are at the 2-10 ng Hg g-1 dw level characteristic of Danish coastal sediments with no known history of mercury contamination. Concentrations of mercury in the benthic biota along Harboøre Tange have also decreased since the 1980s but despite the lowered mercury concentrations in the sediments, concentrations in most samples of benthic invertebrate fauna still exceed those in uncontaminated coastal areas and also the Environmental Quality Standard (EQS) of 20 ng Hg g-1 wet weight (≈100 ng Hg g-1 dry weight) defined by the European Union's Water Framework Directive. Concentration ranges in selected organisms are: (Harboøre Tange l980s/Harboøre Tange now/uncontaminated areas - given in ng Hg g-1 dw): Periwinkles Littorina littorea 9000/150-450/55-77, blue mussels Mytilus edulis up to 9000/300-500/40-170, cockles Cerastoderma edule up to 8000/400-1200/200, brown shrimp Crangon crangon 700-2200/150-450/47, eelgrass Zostera marina up to 330/25-70/12. The present results - together with a literature review - show that a simple and straight forward relationship between the concentrations of mercury in sediment and benthic organisms does not necessarily exist.

Investigation of the potential endocrine effect of nitrate in zebrafish Danio rerio and brown trout Salmo trutta.

Nitrate has the potential to affect steroid production. Nitrate concentrations in streams in agricultural areas may exceed concentrations showing effects in laboratory studies. The effects of nitrate and/or nitrite on endocrine relevant endpoints were tested in zebrafish and brown trout. Zebrafish were exposed in two experiments to nitrate (8.8 to 89 mg NO3-/L) and nitrite (3.6 to 19 mg NO2-/L) during the period of sexual differentiation and sex ratios were determined. Vitellogenin concentrations were determined in the second experiment. The sex ratio was unaffected by the exposure to nitrate and nitrite. Vitellogenin concentrations were slightly elevated in males (but not females) in all of the groups exposed to nitrate. Juvenile brown trout were exposed to 5.7, 14, and 31 mg NO3-/L for 8 days and vitellogenin levels in liver were determined. Vitellogenin concentrations in the females were not affected by exposure, but in the males, there was an overall statistically significant effect of exposure to nitrate with the group exposed to 5.7 mg NO3-/L showing a trend of higher vitellogenin concentrations than the control group; levels in the males of the groups exposed to 14 and 31 mg NO3-/L were not statistically different from those of the control group. In conclusion, some marginal effect of nitrate in male fish on endocrine activity was observed but the present results for zebrafish, using environmentally relevant concentrations, do not define nitrate and nitrite as endocrine disrupting chemicals according to the generally accepted WHO/IPCS definition because no adverse effects (altered sex ratios) were demonstrated.