| dc.description.abstract | During the last decades there has been an increasing awareness of pollution in tunnel wash water and highway runoff, and its ecotoxicological effects. The objectives of the present thesis were to investigate trace element accumulation and the levels of the biomarkers metallothionein (MT), 7-Ethoxyresorufin O-deethylase (EROD), glutathione S-transferase (GST) and reduced glutathione (GSH) in common frog (Rana temporaria) embryos and tadpoles inhabiting Vassum and Skullerud sedimentation ponds along E6 in southeast Norway. A naturally occurring rainwater pond was also included in the study. Tadpoles and water samples were collected weekly in May and June 2012 and analyzed for 34 elements, including several metals of environmental concern. The chemical analyses detected total chromium (Cr), copper (Cu) and zinc (Zn) concentrations in the two sedimentation ponds high enough for the water quality to be classified as ‘poor’ or ‘very poor’ at several samplings, according to the classification system developed by the Climate and Pollution Agency. However, the highest concentrations of the majority of the trace elements were identified in the naturally occurring rainwater pond, probably due to impact from an abandoned shooting range nearby. For practically all of the rest of the elements the highest concentrations were detected in Vassum, while more moderate concentrations of most elements were measured in Skullerud.
Frog embryos and tadpoles in all three ponds showed a significant time dependent trace element accumulation. The statistics were performed using the first principal component site scores derived from a principal component analysis (PCA) on tadpole tissue element concentrations as representative values for overall element accumulation (henceforth referred to simply as ‘overall tissue element concentrations’). The overall tissue element concentrations reached the highest levels in Vassum tadpoles although the highest total and dissolved water concentrations of most elements were detected in the naturally occurring pond. No significant correlation was found between trace element concentrations in water and tadpoles, respectively.
The levels of MT, EROD, GST and GSH varied significantly with time in tadpoles in all three ponds. Overall tissue element concentrations could not explain the variation in MT, EROD or GSH as no significant correlation was found between overall tissue element concentrations and these biomarkers. However, significant positive correlation was found between MT and tissue lead (Pb) concentrations when testing this separately. Significant positive correlation was also found between overall tissue element concentrations and GST, and between GST and tissue cadmium (Cd) concentrations, and GST and tissue Pb concentrations when testing this separately. Hence, the results suggest that overall tissue element concentrations, as well as tissue Cd and Pb concentrations, can possibly explain some of the variation in GST. Altogether, the lack of an adequate reference group makes it difficult to conclude whether any of the biomarkers are induced above basal level.
The results suggest that R. temporaria tadpoles growing up in the sedimentation ponds as well as the naturally occurring pond may be adversely affected by contaminants in the water. Controlled exposure studies or field studies including a proper reference group are needed to identify the basal level of biomarkers in tadpoles and demonstrate any departures from the natural variation. | no_NO |
