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The distribution of iodine in the surface ocean – of which iodide-iodine is a large destructor of tropospheric ozone (O₃) – can be attributed to bothin situ(i.e., biological) andex situ(i.e., mixing) drivers. Currently, uncertainty regarding the rates and mechanisms of iodide (I^-) oxidation render it difficult to distinguish the importance ofin situreactions vsex situmixing in driving iodine’s distribution, thus leading to uncertainty in climatological ozone atmospheric models. It has been hypothesized that reactive oxygen species (ROS), such as superoxide (O₂^•−) or hydrogen peroxide (H₂O₂), may be needed for I^-oxidation to occur at the sea surface, but this has yet to be demonstrated in natural marine waters. To test the role of ROS in iodine redox transformations, shipboard isotope tracer incubations were conducted as part of the Bermuda Atlantic Time Series (BATS) in the Sargasso Sea in September of 2018. Incubation trials evaluated the effects of ROS (O₂^•−, H₂O₂) on iodine redox transformations over time and at euphotic and sub-photic depths. Rates of I^-oxidation were assessed using a¹²⁹I^-tracer (t_1/2~15.7 Myr) added to all incubations, and¹²⁹I/¹²⁷I ratios of individual iodine species (I^-, IO₃^-). Our results show a lack of I^-oxidation to IO₃^-within the resolution of our tracer approach – i.e., <2.99 nM/day, or <1091.4 nM/yr. In addition, we present new ROS data from BATS and compare our iodine speciation profiles to that from two previous studies conducted at BATS, which demonstrate long-term iodine stability. These results indicate thatex situprocesses, such as vertical mixing, may play an important role in broader iodine species’ distribution in this and similar regions.