From tiny streams to gigantic rivers like the Mississippi—microbes in sediments work tirelessly to maintain key biogeochemical cycles. However, as temperatures rise, they tend to operate frequently in stress mode. This is the conclusion of an international study led by the University of Duisburg-Essen, which analyzed DNA and mRNA from 20 North American rivers. The results, recently published in the journal Microbiome, confirm patterns that have also been observed for European rivers.