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Metals and metalloids concentrations in three genotypes of pelagic Sargassum from the Atlantic Ocean Basin-scale
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International audience. Since 2011, in Caribbean Islands, unprecedented massive stranding of a pelagic brown algae Sargassum spp. has damaged coastal ecosystems and disrupted the economy. Brown algae have a high capacity to concentrate heavy metals contaminants. Through accumulation of heavy metals during their journey, floating Sargassum can play a role of contaminant transfer from off shore to the coast. In July and August 2019, three morphotypes of sargasso (S. fluitans III, S. natans I and S. natans VIII) were sampled in seven stations, regularly spaced, along a 3,400 km transect from the middle of Atlantic Ocean to Guadeloupe Islands (French West Indies). For each of the 72 samples of sargasso algae, concentrations of 15 heavy metal(loid)s elements were analyzed by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). Mean metal concentrations in all morphotypes and stations were ranked in the following descending order: As > Fe > Al > Mn > Cd > Zn > Ni > V > Cu > Cr > Hg. The metalloid As is the most largely present in all our samples with a mean concentration of 92.72 μg.g −1 and an maximum value of 115 μg. g −1 which is in accordance with concentrations previously observed in the Caribbean area (80-150 ppm). Those value are above different maximum safety level, therefore, strategies proposed for valorization of Sargassum should consider this As content to avoid potential environmental and health issues. At the scale of the Atlantic Ocean, metallic element concentration do not present spatial longitudinal gradient. Morphotype of Sargassum present different metal(loids) contamination patterns with distinction between S. fluitans III and the two others morphotypes (S. natans I and VIII).
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