Project summary: Golden tides are massive accumulations of floating brown seaweed in the genus Sargassum that began affecting Caribbean, American, and African coasts in 2011. Observations and models have concluded that these events are mainly driven by widespread eutrophication and warmer sea surface temperatures in the Atlantic resulting from climate change. A single golden tide can strand as much as 96,000 m3 of algae per Km of coastline and affect large expanses of shoreline, often coinciding with the location of coastal communities and highly frequented tourist destinations. Various health hazards may result directly or indirectly from the accumulation of this algal biomass, including increased risk of drowning, skin irritations from contact with algal mats, proliferation of biting flies from beached algal biomass, and the production of harmful gases from algal decomposition. These hazards disproportionately affect Hispanic- and Afro-Caribbean communities, representing one of the least studied areas of health disparities. This research will focus on gas emissions from decomposing algal accumulations, with the aim of quantifying risk of exposure to hydrogen sulfide produced during these events in the US Virgin Islands. The study will use a combination of decomposition chamber experiments to measure sulfide gas production and direct field measurements of the gas in affected areas. It will also compare two available techniques for measuring H2S to explore more user-friendly technologies that can be adopted by Sargassum cleanup crews to monitor potential risks.