| dc.description.abstract | Related species have been assumed to have a similar sensitivity to exposure to environmental pollution. Atlantic cod (Gadus morhua) is an important commercial fish and a key-species in monitoring. With the recent decline in Atlantic cod populations in the Oslofjord and a change in dominating species, knowledge about sensitivity in species related to Atlantic cod that are also present in the Oslofjord may be important for future monitoring and management of populations. The Oslofjord is divided into the urban inner Oslofjord and a less polluted outer Oslofjord. This study aimed to identify location differences between the urban and more polluted inner Oslofjord and the less polluted outer Oslofjord, to identify differences between species in the Gadidae family (Atlantic cod, whiting (Merlangius merlangus), Norway pout (Trisopterus esmarkii) and haddock (Melanogrammus aeglefinus)), to identify seasonal differences in exposure and effects of contaminants in the Oslofjord, and to identify differences in effect of exposure to contaminants between tissues. This was done by sampling 8 fish from each species in the inner and outer Oslofjord in the spring and fall. Concentrations of polycyclic aromatic hydrocarbon (PAH) metabolites were quantified in the bile and mercury concentration was determined in liver samples to get estimates of exposure to environmental pollution. Hepatic, gill, and heart cytochrome P4501A (CYP1A) activity was determined from the ethoxyresorufin O-deethylase (EROD) assay to get estimates of effect of exposure to environmental pollution as the activity can be induced by exposure to contaminants such as PAHs. The study identified significantly higher concentrations of PAH-metabolites in bile in the inner Oslofjord. Species differences and seasonal differences varied among the three groups of PAH metabolites, indicating differences in exposure and sources through the year. There was identified a location difference in mercury exposure in Norway pout in the inner Oslofjord, which could be due to differences in age between locations. Atlantic cod had higher hepatic mercury concentrations than one or more species in both locations in both seasons, which could be due to differences in age or diet between species. There was significantly lower hepatic CYP1A activity in spring in the inner Oslofjord, which may be due to inhibition of CYP1A activity by reproductive hormones or other CYP1A inhibitors. There were no species differences in hepatic CYP1A activity. However, there are known differences in baseline activity, which could indicate a difference in sensitivity, as the activity was not induced to the same degree in all species. The hepatic CYP1A activity was higher in fall than in spring, with median activity almost one order of magnitude higher in fall. This is not in accordance with activity determined in previous years and could indicate that there is a new source of contamination that induces the activity. Gill CYP1A activity was significantly different between Norway pout and Atlantic cod, whiting, and haddock in the inner Oslofjord and between Norway pout and Atlantic cod and whiting in fall. The gill CYP1A activity was higher in the spring and showed a positive correlation with exposure to pyrene, indicating that gill CYP1A activity could be a good biomarker for exposure to water-borne contaminants. There were species differences in heart CYP1A activity, with significantly higher activity in Atlantic cod than in whiting in the inner Oslofjord in spring, higher activity in Atlantic cod than in whiting and Norway pout in fall, higher activity in Atlantic cod than in haddock in the outer Oslofjord in fall, higher activity in Atlantic cod in haddock and whiting in the inner Oslofjord and higher activity in haddock than in Norway pout in the outer Oslofjord in fall. Hepatic CYP1A activity was generally the highest of the three tissues, followed by gill CYP1A activity. To correctly interpret results and identify species differences, estimates of baseline activity in more species and tissues needs to be determined. | eng |