Analyses of the genetic structure of Sargassum horneri in the Yellow Sea: implications of the temporal and spatial relations among floating and benthic populations

Abstract

Sargassum horneri is one of the most common seaweeds in China growing on solid substrates in the sublittoral zones along the Chinese coast. Large-scale drifting biomass of S. horneri has been reported in the Yellow Sea since 2010. Huge amount of the stranded biomass of this alga on the cultivation rafts of Pyropia yezoensis has drawn wide attention after damaging the local Pyropia farming industry. The original sources of the drifting biomass in the Yellow Sea remain unknown. In this study, 16 populations including three benthic and 13 drifting ones were sampled from the Yellow Sea and the East China Sea. Results of microsatellite analyses revealed that there were significant genetic differentiations among most of the investigated populations. Cluster analysis demonstrated that the drifting individuals from the same year, rather than from the same sampling locations, were clustered together. The existence of marked admixture in six populations also implies that the same drifting population could be of different origins. These results provide evidence suggesting that the drifting populations, in particular the populations occurring in different years, originated from multiple sources. Satellite imagery observation combined with genetic analyses of more benthic and drifting populations in the future are expected to elucidate, on a clearer level, the exact locations of the origin of the drifting populations.