Green Bay sediments exhibit a generally decreasing gradient of polychlorinated biphenyl (PCB) concentrations from the mouth of the Fox River at the city of Green Bay to the more pristine northern end of the bay.  Our question was whether there is a similar concentration gradient for a suspension feeder, the invasive quagga mussel, along Green Bay's rocky (hence not depositional) eastern coast.  If so, there would likely be a concentration gradient for the main predator on quagga mussels, the invasive round goby.  Such a situation would illustrate that these exotic benthos focused contaminants in nearshore regions in a manner that parallels sedimentation in deeper water.  It would also indicate a PCB entry point into the benthic system. We performed congener-specific PCB analyses on quagga mussels and round gobies collected from ten sites along the east shore of Green Bay. Total PCB concentration (?PCB) results were compared with the sediment data. Linear regression showed that mussel tissue ?PCB followed sediment ?PCB (P = 0.007) with the exception of two locations near Sturgeon Bay where cleaner Lake Michigan water enters in tidal pulses. Analysis of Covariance showed that in areas where high sediment ?PCBs were reported, fish length dictated round goby's ?PCB (F1,14 = 7.46, P=0.016) and that the variation between sites did not influence ?PCB in individual fish. In addition, lipid-normalized ?PCB in round gobies generally declined with fish length. This result agrees with modeling predictions previously made in our lab and suggests that an ontogenetic diet shift might be influencing ?PCB in round gobies.

Reexamining legacy PCB concentrations in Green Bay benthos: The effects of invasive species

248th National Meeting (2014)

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