Phytoplankton-produced dimethylsulfoniopropionate (DMSP) provides underwater and atmospheric foraging cues for several species of marine invertebrates, fish, birds, and mammals. However, its role in the chemical ecology of marine planktonic microbes is largely unknown, and there is evidence for contradictory functions. By using microfluidics and image analysis of swimming behavior, we observed attraction toward microscale pulses of DMSP and related compounds among several motile strains of phytoplankton, heterotrophic bacteria, and bacterivore and herbivore microzooplankton. Because microbial DMSP cycling is the main natural source of cloud-forming sulfur aerosols, our results highlight how adaptations to microscale chemical seascapes shape planktonic food webs, while potentially influencing climate at the global scale.