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The organic sulfur compound dimethylsulfoniopropionate (DMSP) is synthesized by numerous species of marine phytoplankton, and its volatile degradation products are a major source of biogenic sulfur to the atmosphere. A massive bloom of the dinoflagellate Akashiwo sanguinea occurred in Monterey Bay, CA, USA, in the fall of 2016 and led to exceptionally high seawater DMSP concentrations that peaked at 4,240 nM. Bacterial consumption rates showed that only a small fraction of the DMSP standing stock flowed through the dissolved DMSP pool per day, contributing to the high DMSP concentrations and creating conditions conducive to production of dimethylsulfide (DMS). Conservative calculations of DMS yield from this persistent A. sanguinea bloom suggest substantial regional-scale inputs of DMS-sulfur to the atmosphere. Other recently reported major coastal blooms of A. sanguinea, along with indications that this species may benefit from climate change conditions, reveal a mechanism that could alter oceanic contributions to atmospheric sulfur pools.

Plain Language Summary Marine phytoplankton produce the organic sulfur compound dimethylsulfoniopropionate (DMSP), which is used for osmotic balance and serves as a carbon and sulfur source to marine bacteria. A massive bloom of a dinoflagellate in Monterey Bay, CA, USA, in 2016 resulted in extremely high concentrations of DMSP over a 6-week period, the highest DMSP concentrations yet recorded. This extended bloom established ideal conditions for the release of volatile sulfur from the ocean. More frequent and extensive blooms of DMSP-producing phytoplankton have been observed and may affect ocean contributions to the atmospheric sulfur pool and the formation of cloud condensation nuclei.

Key Points

A dinoflagellate bloom of exceptional proportions occurred in Monterey Bay and offshore regions of the Pacific Ocean in fall 2016 DMSP concentrations during 46 days of the Akashiwo sanguinea bloom were the highest ever recorded Only a small fraction of the DMSP standing stock flowed through the dissolved pool each day, creating conditions conducive to high DMS flux