Nutrient removal ability of seaweeds on Pyropia yezoensis aquaculture rafts in China's radial sandbanks

Nutrient removal ability of seaweeds on Pyropia yezoensis aquaculture rafts was studied during the P. yezoensis aquaculture season of 2012-2013 at the offshore farm along the radial sandbanks of Jiangsu Province, China. During the P. yezoensis cultivation season, three Ulva species, including Ulva prolifera, Ulva linza, and Ulva flexuosa, were present on the cultivation rafts. These Ulva spp. were then removed from the rafts or floated away when rafts were recycled in April 2013. The quantities of nitrogen and phosphorus removed by the harvest of P. yezoensis were 3688 and 106 tons, respectively. The nitrogen and phosphorus removal of Ulva were 77 and 3 tons, respectively. These results indicate that P. yezoensis can efficiently remove excess nutrients from coastal waters. The Ulva if harvested can also be utilized as an additional nutrient management tool in eutrophic waters. In addition, introduction of high-temperature adapted seaweeds would be a useful way to continue algal bioremediation during the off season of P. yezoensis aquaculture.