Quantifying the lake food web

Wisconsin’s fish are what they eat, but is the pantry stocked exclusively from within the lake food web?

“The basic question is: To what extent are fish made of terrestrial plants?” says Stephen Carpenter, UW–Madison zoology professor, who thinks the answer could be as high as 50 percent. “People think of fish as eating little bugs in the water, which eat plankton in the water, but a considerable amount of Wisconsin fish production relies on land matter that falls into lakes.”

By comparing levels of deuterium — an isotope of hydrogen found in greater concentrations in terrestrial biomass than aquatic flora — in samples of fish and plants (both aquatic and terrestrial) taken from 15 to 20 Wisconsin lakes, Carpenter will get an idea of how much of that fish was built up on food that made its way into the lake system from land.

The research will be funded by a $519,443 grant from the National Science Foundation, taking advantage of funding made available by the American Recovery and Reinvestment Act.