Understanding the recurrent large-scale green tide in the Yellow Sea: Temporal and spatial correlations between multiple geographical, aquacultural and biological factors

The coast of Jiangsu Province in China – where Ulva prolifera has always been firstly spotted before developing into green tides – is uniquely characterized by a huge intertidal radial mudflat. Results showed that: (1) propagules of U. prolifera have been consistently present in seawater and sediments of this mudflat and varied with locations and seasons; (2) over 50,000 tons of fermented chicken manure have been applied annually from March to May in coastal animal aquaculture ponds and thereafter the waste water has been discharged into the radial mudflat intensifying eutrophication; and (3) free-floating U. prolifera could be stranded in any floating infrastructures in coastal waters including large scale Porphyra farming rafts. For a truly integrated management of the coastal zone, reduction in nutrient inputs, and control of the effluents of the coastal pond systems, are needed to control eutrophication and prevent green tides in the future. ► Propagules of Ulva prolifera are consistently present in the radial mudflat. ► Seasonally discharged land-derived effluents intensify the eutrophication. ► Branched U. prolifera achieved floating within an hour. ► Nori nets strand floating Ulva biomass and enlarge it in the radial mudflat.