Ostreopsis blooms promote production of volatile organic sulfur compounds: environmental and health implications.

Abstract

Blooms of the benthic dinoflagellate Ostreopsis have been associated with occasional episodes of acute respiratory symptoms, skin irritations, and general discomfort in people exposed on adjacent beaches. This microalgae, well known for producing potent toxins, has been implicated in health issues during bloom events; however, the presence of these toxins in marine aerosols does not fully explain the variety and intensity of symptoms reported, suggesting that other factors, such as the emission of volatile compounds, may also play a role. This study aims to identify the volatile organic compounds (VOCs) present in both water and air during an Ostreopsis bloom, to characterize the VOCs produced by monoclonal Ostreopsis strains in culture, and to assess their potential risks to the environment and human health. Air and water samples collected during blooms revealed the presence of dimethyl sulfide, methanethiol, dimethyl disulfide and dimethyl trisulfide, with concentrations significantly exceeding established toxicity and ecotoxicity thresholds (e.g., MeSH up to 4.7 μmol.L^-1, exceeding the PNEC of 0.0021 μmol.L^-1 by ∼2000-fold; DMS up to 44 μmol.L^-1, exceeding PNEC of 0.0047 μmol.L^-1 by ∼9000-fold). In contrast, only dimethyl sulfide was detected in monoclonal cultures of Ostreopsis strains. These results indicate a possible contribution of microorganisms associated with Ostreopsis blooms in sulfur VOCs production.