Environmental Science & Technology Online has this interesting report about a study of food web dynamics and pollution in Lake Michigan. Calumet Harbor is a part of the lake that is dominated by zebra mussels (Dreissena polymorpha) and round gobies (Neogobius melanostomus). Juvenile round gobies love to eat fish eggs as well as crustaceans that live in the lake sediment. Unfortunately, the crustaceans are feeding on the waste of the zebra mussels, and this waste and fish eggs are two of the links in the food chain where PCBs accumulate in high concentrations.
Testing showed that the young gobies have much higher levels of PCBs than the adult gobies or the smallmouth bass that also live in the lake, a detour off the typical path of biomagnification that suggests a change is needed in the policy of recommending that people eat smaller fish to avoid exposure to toxins.