Distribution patterns and biogeography of Sargassum (Fucales, Phaeophyceae) along the coast of Vietnam

Abstract Sargassum species form large beds that play an important role in coastal ecosystems. The beds are abundant and Sargassum is often used as food and in Asian medicine in Vietnam. As a base for future use and conservation, we surveyed 14 species of Sargassum at eight locations during April-May of 2018 and 2019. Sargassum species from Vietnam were divisible into northern and southern groups; the northern group comprised Sargassum graminifolium , Sargassum herklotsii , and Sargassum cotoense , which occur in the North and North Central zones. The southern group comprised Sargassum bicorne , Sargassum feldmannii , Sargassum ilicifolium , Sargassum swartzii , and two endemic species, Sargassum phamhoangii and Sargassum quinhonense , which occur in the Central to South West zones. Three species, Sargassum aquifolium , Sargassum oligocystum , and Sargassum polycystum , were widespread along the long coast of Vietnam. This is the first report on distribution patterns of Sargassum species along the long coast of Vietnam. Our study provides baseline data for evaluating ecological disturbance and risks of Sargassum -associated ecosystems.