Distributions of PCB Congeners and Homologues in White Sucker and Coho Salmon from Lake Michigan

Abstract

We tested the hypothesis of the proportion of higher chlorinated biphenyl (PCB) congeners increasing with increasing trophic level by comparing the respective PCB homologue distributions in an omnivore, white sucker ( Catostomus commersoni), and a top predator, coho salmon ( Oncorhynchus kisutch), from Lake Michigan. Adult females had the same congener and homologue proportions of total PCB concentration (ΣPCB) as adult males in both species. Hexachlorinated congeners comprised the largest proportion (32%) found in white sucker, followed by heptachlorinated (21%) and octochlorinated (18%) congeners. In contrast, pentachlorinated congeners comprised the largest proportion (33%) of ΣPCB found in coho salmon, followed by hexachlorinated (26%) and tetrachlorinated (24%) congeners. Coho salmon contained significantly higher proportions of tri-, tetra-, and pentachlorinated congeners, whereas white sucker contained significantly higher proportions of hexa- through decachlorinated congeners. Our results were opposite of the hypothesis of greater degree of PCB chlorination with increasing trophic level, and supported the contention that the PCB congener proportions in fish depends mainly on diet, and does not necessarily reflect the trophic level of the fish. Our results also supported the contention that diets do not vary between the sexes in most fish populations.

Ratio of Mercury Concentration to PCB Concentration Varies with Sex of White Sucker (Catostomus commersonii)

“…However, carbon and nitrogen stable isotope ratios did not significantly vary between the sexes of white suckers from the Kewaunee River population based on the results from an earlier study [48], indicating that this explanation was unlikely. Moreover, the PCB congener and homolog distributions did not significantly differ between the sexes of white suckers from the Kewaunee River population [49], corroborating the contention that habitat use and food habits did not vary between the sexes. Because the females grew faster than the males, the growth dilution effect could have also contributed to the males having a greater Hg concentration than the females.…”

What can we learn from 28 years of monitoring of fish tissue polychlorinated biphenyls in Michigan's rivers?

“…Congener quantification is valuable because it enables the assessment of toxicity by PCB categories (Klocke & Lein, 2020), it can reveal congener‐specific metabolism (Rodenburg & Delistraty, 2019), and it can reveal sources—both fresh and weathered (Megson et al, 2019; Rodenburg et al, 2011). Michigan quantifies total PCBs using a relatively large subset (83 congeners); however, this subset is still likely to underpredict total PCB concentrations and confound comparisons across studies (Stapanian et al, 2018; Megson et al, 2019). The Michigan program is notable, however, in that other states still quantify total PCBs based on Aroclor methods (e.g., Ohio, Wisconsin, Minnesota).…”