Spatial and temporal trends and effects of contaminants in the Canadian Arctic marine ecosystem: a review

Recent studies have added substantially to our knowledge of spatial and tem poral trends of persistent organic pollutants and heavy metals in the Canad ian Arctic marine ecosystem. This paper reviews the current state of knowle dge of contaminants in marine biota in the Canadian Arctic and where possib le, discusses biological effects. The geographic coverage of information on contaminants such as persistent organochlorines (OCs) (PCBs, DDT- and chlo rdane-related compounds, hexachlorocyclohexanes, toxaphene) and heavy metal s (mercury, selenium, cadmium, lead) in tissues of marine mammal and sea bi rds is relatively complete. Ah major beluga, ringed seal and polar bear sto cks along with several major sea bird colonies have been sampled and analys ed for OC and heavy metal contaminants. Studies on contaminants in walrus a re limited to Fore Basin and northern Quebec stocks, while migratory harp s eals have only been studied recently at one location. Contaminant measureme nts in bearded seal, harbour seal, bowhead whale and killer whale tissues f rom the Canadian Arctic are very limited or non-existent. Many of the tempo ral trend data for contaminants in Canadian Arctic biota are confounded by changes in analytical methodology, as well as by variability due to age/siz e, or to dietary and population shifts. Despite this, studies of OCs in rin ged seal blubber at Holman Island and in sea birds at Prince Leopold Island in Lancaster Sound show declining concentrations of PCBs and DDT-related c ompounds from the 1970s to 1980s then a levelling off during the 1980s and early 1990s. For other OCs, such as chlordane, HCH and toxaphene, limited d ata for the 1980s to early 1990s suggests few significant declines in conce ntrations in marine mammals or sea birds. Temporal trend studies of heavy m etals in ringed seals and beluga found higher mean concentrations of mercur y in more recent (1993/1994) samples than in earlier collections (1981-1984 in eastern Arctic, 1972-1973 in western Arctic) for both species. Rates of accumulation of mercury are also higher in present day animals than 10-20 years ago. Cadmium concentrations in the same animals (eastern Arctic only) showed no change over a 10-year period. No temporal trend data are availab le for metals in sea birds or polar bears. There have been major advances i n knowledge of specific biomarkers in Canadian Arctic biota over the past f ew years. The species with the most significant risk of exposure to PCBs an d OC pesticides may be the polar bear which, based on comparison with EROD activity in other marine mammals (beluga, ringed seal), appears to have ele vated CYP1A-mediated activity. The MFO enzyme data for polar bear, beluga a nd seals suggest that even the relatively low levels of contaminants presen t in Arctic animals may not be without biological effects, especially durin g years of poor feeding. (C) 1999 Elsevier Science B.V. All rights reserved .