In alpine lakes of the Sierra Nevada, the widespread stocking of non-native trout has been implicated in the decline of amphibians and invertebrates. The objectives of this project are to determine natural rates of recovery of these species after the eradication of exotic trout and the effect of trout introduction on the functioning of the lake ecosystem. Recovery of frogs and invertebrates after trout removal will be studied by performing whole-lake experiments in which lakes from which trout are removed are compared to lakes with trout. The investigators will also perform a broad-scale survey of Sierra lakes that vary in the length of time since trout populations have died out naturally. Changes in ecosystem function will be estimated by measuring the relative contributions to overall lake productivity of algae found in the water column versus algae on substrate. The introduction of exotic species has caused extinctions of native species and large changes in the functioning of ecosystems. Although the effects of exotic species introduction have been studied widely, quantitative studies of ecosystem recovery after exotic species eradication are exceedingly rare. Such studies are essential to determine whether ecosystems typically return to their natural condition after the species are removed, and how long such recovery takes. In addition, much can be learned about the natural process of community assembly from experimental study of exotic eradication.
