Surface area:biomass relationship for Sargassum fluitans and Sargassum natans from Sisal Beach, Mexico

To establish the surface area : biomass relationship of pelagic Sargassum spp., individual thalli of beach-cast Sargassum fluitans and Sargassum natans were collected at Sisal Beach, Yucatan peninsula, Mexico in November 2016. 22 thalli each of both species were collected. Additionally, three thalli of an additional species were collected. This species could not be clearly identified and the thalli were not further considered for analysis. Each thalli was blotted with tissue paper to remove adherent seawater and weighed on the beach using a spring balance. Subsequently, the single parts of the thalli (blades, pneumatocysts, stipes) were separated from each other, spread in a tray and photographed together with a ruler as a size reference and a label. The two dimensional projection area of each thallus part was determined using an image analysis software from which the surface area of each three dimensional structure was calculated to obtain the total surface area of the thallus.