Temporal trends of organochlorine contamination in Black Guillemots in Iceland from 1976 to 1996.

The levels of several different persistent organochlorines (OCs) in Black Guillemots Cepphus grylle, collected during the summers of 1976-1996 at Breioafjörour in W-Iceland, were investigated. The levels of about 40 different organochlorines (PCBs, DDTs, chlordanes, toxaphenes, HCH, HCB) were compared with respect to age, sex, fat content, and year of collection. The levels of PCBs correlated very closely with those of DDE, indicating long-range transport as the major source of these contaminants in Iceland, with the ratio PCBs/DDE mostly in the range of 2-5. Unlike the Gyrfalcon Falco rusticolus, the organochlorine levels did not seem to accumulate substantially with age, neither in males nor females. The variation in the levels of OCs at the age of 2 years was even greater than the variation in OC levels over an age range of 12 years. In immature birds the levels of PCBs, DDE, HCB and beta-HCH declined very slowly (T(1/2) from 12 to 20 years) over the years 1976-1996, whereas the levels of alpha-HCH and p,p'-DDT declined much faster. The levels of trans-nonachlor, alpha-chlordane, gamma-chlordane, oxychlordane, and toxaphene did not correlate with the year of collection. As the Black Guillemot is mostly a resident seabird, feeding mainly on small fish and invertebrates, this investigation should give a good indication of the temporal trends of organochlorine pollution at Breioafjörour, Iceland, during this 20 year period and is likely to reflect baseline trends in the marine environment of the North-Atlantic Ocean.