In this thesis, studies on organic contamination from both diffuse and point sources in Icelandic waters are presented. The aim was to investigate bioaccumulation and biological effects of the contaminants or biomarkers, and their applicability in environmental marine coastal monitoring, especially in areas with moderate or low levels of contamination such as Iceland.

In paper I, bioaccumulation and biomagnification of organochlorines (OCs) from diffuse sources were studied in a marine food web from a “pristine” site in Iceland. The results reveal that OC levels were low on the lower trophic levels, but an order of a magnitude larger in the top predator black guillemot (Cepphus grylle), except for ΣHCH and ΣChlordane levels, which were low and similar in all organisms. ΣPCB, ΣDDT, and HCB tissue concentrations were significantly correlated with trophic level of the organisms as defined by δ15N, indicating biomagnification of these compounds. The OC tissue levels observed here are within the range of levels in biota reported from the Arctic, but orders of magnitude lower than some levels in biota from the North Sea and the Baltic Sea. 

 Tributyltin (TBT) contamination from antifouling boat paint was evaluated by using imposex in the dogwhelk Nucella lapillus, and with chemical analysis in papers II and III. The results indicated widespread TBT contamination even in fairly remote and sparsely populated areas where boat traffic is limited. Seasonal fluctuations in TBT levels in tissues of dogwhelk and the blue mussel (Mytilus edulis) were observed. TBT levels were high during late summer and autumn, and low during winter and spring, which should be considered when monitoring TBT levels with chemical tissue analysis in organisms at high latitudes.

In papers IV and V the applicability of using DNA adduct analysis in blue mussels (Mytilus edulis) for monitoring genotoxic exposure was investigated with field studies in Iceland and with experiments. The results revealed that relatively low or moderate contamination can result in genotoxic effects such as DNA adduct formation in gills of indigenous blue mussels. Transplantation of mussels from a reference site to a subtidal zone at a contaminated site for 6 weeks on the other hand did not result in DNA adduct levels similar to those in native mussels in the contaminated site.