Microbial plankton experience short-term fluctua-tions in total solar irradiance and in its spectral composition as they are vertically moved by turbulence in the oceanic up-per mixed layer (UML). The fact that the light exposure is not static but dynamic may have important consequences for bio-geochemical processes and ocean–atmosphere fluxes. How-ever, most biogeochemical processes other than primary pro-duction, like bacterial production or dimethylsulfide (DMS) production, are seldom measured in sunlight and even less often in dynamic light fields. We conducted four experi-ments in oligotrophic summer stratified Mediterranean wa-ters, where a sample from the UML was incubated in ultra-violet (UV)-transparent bottles at three fixed depths within the UML and on a vertically moving basket across the same depth range. We assessed the response of the phyto-and bacterioplankton community with physiological indicators based on flow cytometry singe-cell measurements, fast repe-tition rate fluorometry (FRRf), phytoplankton pigment con-centrations and particulate light absorption. Dynamic light exposure caused a subtle disruption of the photoinhibition and photoacclimation processes associated with ultraviolet radiation (UVR), which slightly alleviated bacterial photoin-hibition but did not favor primary production. Gross DMS production (GP DMS) decreased sharply with depth in parallel to shortwave UVR, and displayed a dose-dependent response that mixing did not significantly disrupt. To our knowledge, we provide the first measurements of GP DMS under in situ UV-inclusive optical conditions.