Dimethylsulfoniopropionate concentrations in Mediterranean coastal water and ambient aerosols during Ostreopsis cf. ovata blooms

Dimethylsulfoniopropionate (DMSP) is a major component of the organosulfur cycle in the oceans and plays a significant role in the global sulfur cycle. DMSP is naturally produced by, among others, dinoflagellates, some of which form harmful algal blooms (HABs). We studied DMSP in two field campaigns conducted near Barcelona, Spain, in seawater and aerosols during Ostreopsis cf. ovata blooms in 2017 and 2018. Seawater, sea surface microlayer, PM1 and PM10 aerosol samples, as well as other meteorological data, were collected during July-August to determine the sources of DMSP. The sea-surface microlayer where the HAB forming Ostreopsis can float as aggregates was enriched in DMSP relative to the underlying seawater. DMSP was detected in the PM10 aerosol fraction but not in the PM1 aerosol fraction demonstrating that DMSP was associated with coarse particles with a diameter greater than 1 micron. Significant positive correlations between DMSP in the PM10 aerosol fraction and the conservative marine tracers (e.g., sodium, chloride, and bromide) in the aerosols suggest that the DMSP in the coarse fraction was directly emitted into the atmosphere from the ocean through bursting bubbles and breaking waves as part of primary marine aerosols. The contribution of the recurrent blooms of Ostreopsis and other high biomass coastal blooms on the biogeochemical sulfur cycle will be discussed.