Increased Temperature and Nitrogen Enrichment Inhibit the Growth of the Golden Tide Blooming Macroalgae Sargassum horneri in the Yellow Sea, China

The golden tide, a large biomass bloom of the brown macroalgae Sargassum horneri, occurs yearly in the Yellow Sea, where it causes enormous economic and ecologic losses. To investigate the response of S. horneri to global warming and eutrophication, S. horneri was cultured under six conditions of varying temperature combinations (20 and 24 degrees C) and nitrogen levels (5, 30, and 300 mu M). The growth, photosynthetic performance, pigment content, and contents of soluble protein were assessed. The growth of S. horneri followed an increasing trend with increasing N concentration at ambient temperature. Elevated temperatures had an inhibitory effect on growth and photosynthesis in S. horneri, which was further enhanced by eutrophication. This suggests that in the globally warming environment of the future, eutrophication may reduce the frequency and scale of gold tide outbreaks during the hot season.