Freshwater habitats in parts of the world that get snow and ice are experiencing increased salinity due to the use of road salts. We used experimental evolution to test how the ciliate Tetrahymena thermophila, which is endemic to the northeastern United States and a key player in the microbial food web, will adapt to increasing salinity. Populations of T. thermophila were evolved in either no salt or constant or increasing concentrations of NaCl or MgCl₂, two of the most commonly used road salts. Following about 175 generations of evolution all populations were tested for survival and growth in different salt concentrations. We found that Tetrahymena adapt quickly to survive and grow better in increasing salinity with the IC50 increasing significantly in populations grown in the highest salt concentrations. However, populations adapted to the highest salts also experienced fitness tradeoffs when grown in salt-free conditions. These results demonstrate the rapidity with which microbial populations can respond to anthropogenic changes to their environment, yet highlight the potential costs associated with this adaptation.