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In this study, we present the levels of organochlorine (∑DDT, ∑HCH, ∑chlordane, HCB, and ∑PCBs) and metal (Pb, Hg, and Se) contaminants and their relationship to stable carbon and nitrogen isotope values in the Gulf of the Farallones marine food web. This food web consisted of two species of euphausiids (Euphausia pacifica and Thysanoessa spinifera), two fish species [short-bellied rockfish (Sebastes jordani) and anchovy (Engraulis mordax)], four bird species [common murre (Uria aalge), Brandt's cormorant (Phalacrocorax penicillatus), rhinoceros auklet (Cerorhinca monocerata), and pigeon guillemot (Cepphus columba)], and the northern sea lion (Eumetopias jubatus). We used a novel method of using egg albumen to determine stable isotope values. The values of δ13C ranged from −20.1‰ in the euphausiids to −15.0‰ in the northern sea lion and were consistant with a pelagic/offshore vs benthic/inshore results found in other studies. Values of δ15N in the Gulf of the Farallones food web ranged from 11.2‰ in the euphasiids to 19.8‰ in the northern sea lion and generally demonstrate an equivalence with trophic level. The levels of organochlorine compounds were lowest in the euphausiids [∑DDT 11, and ∑PCB 4.5 μg/kg dry weight geometric mean (GM)] and highest in the northern sea lion blubber (∑DDT 9500 and ∑PCB 3500 μg/kg dry weight GM). The highest levels of organochlorine compounds in the birds were in the common murre (∑DDT 8200 and ∑PCB 5900 μg/kg dry weight GM). Levels of Pb, Hg, and Se ranged from 80 to 1000, from 100 to 19000, and from 1900 to 4100 μg/kg dry weight GM, respectively. All of the organochlorine compounds and Hg were significantly correlated with δ15N values in the food web. Lower values of δ15N in egg albumen than in the muscle tissue from common murres reflect a switch in diet to a lower trophic position during the egg formation period. The high contaminant levels in the murre suggest a mobilization of stored lipids into the eggs.

A novel brominated and chlorinated compound, C 10 H 6 N 2 -Br 4 Cl 2 , bioaccumulating in seabird eggs was identified and characterized by low-and high-resolution electron impact ionization (EI), electron capture negative ionization (ECNI), and ammonia positive chemical ionization (PCI) mass spectrometry. This compound is the major congener of a series of four hexahalogenated species. The major congener was determined in egg samples from Leach's stormpetrel, rhinoceros auklet, glaucous-winged gull, and blackfooted albatross from the Pacific coast area; Leach's stormpetrel, Atlantic puffin, and herring gull from the Atlantic coast; and herring gull from the Great Lakes using GC-ECNI-MS. The concentrations of C 10 H 6 N 2 Br 4 Cl 2 in the Pacific Ocean samples ranged from 1.8 to 140 ng/g (wet weight), and were significantly higher than the Atlantic Ocean samples (p ) 0.037). The Pacific Ocean samples contained levels of C 10 H 6 N 2 Br 4 Cl 2 approximately 1.5-2.5 times higher than in the Atlantic Ocean samples of the same or ecologically similar species. The compound was not detected in any of the samples from the Great Lakes. The Pacific Ocean offshore surface feeders had the highest concentrations (34-140 ng/g) when compared to the other samples (0.61-5.6 ng/g). Its strictly marine occurrence and relatively high nitrogen content indicate that C 10 H 6 N 2 -Br 4 Cl 2 probably is a marine natural product, found at highest concentrations in the Pacific Ocean surface feeding birds. A possible structure of C 10 H 6 N 2 Br 4 Cl 2 is 1,1′-dimethyltetrabromodichloro-2,2′-bipyrrole.

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