Comparison of environmental responding strategies between Ulva prolifera and Sargassum horneri: an in-situ study during the co-occurrence of green tides and golden tides in the Yellow Sea, China in 2017

Large-scale green tides in the Yellow Sea occurred for 13 consecutive years since 2007. The unusual co-occurrence of green tides and golden tides occurred in the Yellow Sea in 2017. The causative species are Ulva prolifera and/or Sargassum horneri. Previous studies on physiological response characteristics of U. prolifera and S. horneri are done in the laboratory mainly, and there is no in-situ comparative study in this regard. In this study, the in-situ physiological response characteristics of both species were measured. The results indicated that cyclic electron flow and antioxidant system play more important roles in protecting U. prolifera, while non-photochemical quenching is more important for adapting to the environment in S. horneri. U. prolifera has a stronger ability to utilize nutrients to rapidly increase its biomass under a suitable condition compared to S. horneri.