A common species of zooplankton—the smallest animals in the freshwater food web—can evolve genetic tolerance to moderate levels of road salt in as little as two and a half months, according to new research published online today in the journal Environmental Pollution. The study is the first to demonstrate that the animals can rapidly evolve higher tolerance to road salt, and indicates that freshwater ecosystems may possess some resilience in the face of a 50-fold increase in road deicing salt applications since the 1940s.