Abstract
A free‐floating drifter was designed to directly determine in situ photochemical production rates, photolysis rates, and light fluxes in seawater. This drifter consisted of six trays that were suspended in series from a single buoy line. The trays were constructed so that the attached quartz vessels, containing filtered seawater, were exposed to both downwelling and upwelling irradiation. The quartz vessels were sealed at both ends with ribbed TFE Teflon stoppers that permitted multiple subsampling without introduction of a headspace. The free‐floating drifter was used to study photochemical processes in antarctic waters. It performed well during 12–15‐h deployments, even in rough seas with sustained winds between 15 and 26 m s −1 . Although not tested here, the drifter should perform equally well in the study of photochemical processes in freshwater environments.