Remote sensing of Sargassum biomass, nutrients, and pigments Geophysical Research Letters

Field and laboratory experiments are designed to measureSargassumbiomass per area(density), surface reflectance, nutrient contents, and pigment concentrations. An alternativefloating algaeindex-biomass density model is established to link the spectral reflectance toSargassumbiomass density,with a relative uncertainty of ~12%. Monthly mean integratedSargassumbiomass in the Caribbean Sea andcentral West Atlantic reached at least 4.4 million tons in July 2015. The average %C, %N, and %P per dryweight are 27.16, 1.06, and 0.10, respectively. The mean chlorophyll-a (Chl-a) concentration is ~0.05% of thedry weight. With these parameters, the amounts of nutrients and pigments can be estimated directly fromremotely sensedSargassumbiomass. During bloom seasons,Sargassumcarbon can account for ~18% of thetotal particulate organic carbon in the upper water column. This study provides thefirst quantitativeassessment of the overallSargassumbiomass, nutrients, and pigment abundance from remote sensingobservations, thus helping to quantify their ecological roles and facilitate management decisions Grant no. NA17NOS4510099