Biomagnification of α- and γ-Hexabromocyclododecane Isomers in a Lake Ontario Food Web

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Abstract
The extent of bioaccumulation of hexabromocyclododecane (HBCD) isomers (α, β, and γ) was determined in the Lake Ontario pelagic food web using liquid chromatography tandem mass spectrometry (LC/MS/MS). Concentrations of the α-isomer were consistently higher than that of the γ-isomer. The β-isomer was below method detection limits in all samples. Whole body concentrations (ng/g, wet wt) of α- and γ-HBCD were highest in the top predator lake trout samples ranging from 0.4 to 3.8 ng/g for the α-isomer and 0.1 to 0.8 ng/g for the γ-isomer. For the prey fish species, the trends in α- and γ-HBCD levels were slimy sculpin > smelt > alewife. Mean concentrations of total (Σ) HBCD (sum of α- and γ-isomers) in the macrozooplankter Mysis relicta (0.14 ± 0.02 ng/g wet wt) and in the benthic invertebrate Diporeia hoyi (0.16 ± 0.02 ng/g, wet wt) were similar and approximately twice as high as in plankton (0.06 ± 0.02 ng/g, wet wt). A strong positive linear relationship was found between ΣHBCD concentrations (wet wt) and trophic level based on δ15N suggesting that HBCD biomagnifies in the Lake Ontario food web. The trophic magnification factor (TMF = 6.3) derived from the slope of the ΣHBCD − trophic level relationship was slightly higher than TMFs for p,p‘-DDE (6.1) and ΣPCBs (5.7) found previously. Biomagnification factors (BMF, calculated as the ratio of lipid corrected concentration in predator/lipid corrected concentration in prey) were variable between feeding relationships and ranged from 0.4 to 10.8 for the α-isomer and from 0.2 to 10 for γ-isomers.

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