However, only 1 or 2 species of native fish will eat zebra mussels directly thus limiting the importance of this route. There exists a second indirect route in which contaminants pass through zebra mussels' guts and are eliminated into their fecal material. Subsequent ingestion of contaminated zebra mussel feces by gammarids and midges then results in contaminated invertebrates. Since benthic invertebrates are widely consumed by most species of fish at some point in their life cycle, the indirect route of contaminant transfer may result in pervasive foodchain contamination. The ecological relationships between zebra mussels and round gobies appear to take advantage of both the direct and indirect routes of contaminant transfer.
Round gobies feed heavily on zebra musels and also upon gammarids and midges.
Thus, round gobies may acquire contaminants such as PCBs directly from zebra mussel tissue and from consumption of invertebrates that have fed on contaminanted zebra mussel feces. As a result, the introduction of the round goby into the Great Lakes presents a unique opportunity to test a contemporary research hypothesis which states that PCBs will magnify 3-5 fold with every trophic link in a foodchain. In short, the proposed research will contribute not only to our understanding of foodchain dynamics and contaminant cycling, but will permit us to test basic ecological research hypotheses as well. We will use the pulse-chase methodology to feed contaminated algal cells to zebra mussels. We will then calculate assimilation efficiency for each PCB into the zebra mussel.