Study On The Uptake Of Different Nitrogen By Ulva Prolifera And Ulva Linza

In the Yellow Sea of China, large-scale green tides have broken out for eight consecutive years from 2007 to 2014, which has destroyed the coastal water quality, ecological system and economic development. Satellite imagery, modeling, and field observations have demonstrated that the green tide blooms in the Yellow Sea originate from the Subei Shoal, where there are large areas of intertidal sand flats and ridges extending many kilometers offshore and that favorable oceanographic conditions contributed to the development and northward transport of the bloom into the Yellow Sea. In addition, about 50,000 tons of fermented chicken manure and bait were used annually in aquaculture ponds in Subei Shoal contribute to increased organic nutrient concentrations in Subei coastal waters. Nutrients are the most important substantial foundation in Ulva prolifera green tides occurrence. Besides the inorganic nutrients, the organic nutrients especially the organic nitrogen are also controlling factors that promote Ulva prolifera growth. Therefore, Ulva prolifera is selected as experimental macroalgae to study the nutrient absorption characteristics. And the nutrient competition between Ulva prolifera and Ulva linza are also studied. This work definitely provides a valuable foundation for revealing the occurrence mechanism of green tides in the southern Yellow Sea. The main work and conclusions are as follows:1. Effect of fermented chicken manure and bait collected from Jiangsu aquaculture on the growth of Ulva prolifera and Ulva linzaThe experiment to explore the effect of organic matter on the growth of Ulva prolifera and Ulva linza show that fermented chicken manure and bait would achieve the dissolution equilibrium in 36h, the DON (dissolved organic nitrogen) concentrations are much higher than the DIN(dissolved inorganic nitrogen) concentrations and after the dissolution, the both would decline the seawater pH. Bait can release about 600.00μmol DON and 49.00μmol DIN per gram, while the fermented chicken manure can release about 338.00μmol DON and 83.00μmol DIN per gram. Fermented chicken manure and bait can promote the growth of Ulva prolifera and Ulva linza, but when the same amount was added, bait made a bigger effect on Ulva prolifera and Ulva linza than fermented chicken manure.2. Growth of Ulva prolifera under different ratio of DIN to DONThe experiment about the impact of the different nitrogen sources and different ratio show that Ulva prolifera is preferred assimilate inorganic nutrients (NH4-N and NO3-N), which has been confirmed by in vitro studies. In the first three days of the culture period, the higher inorganic nitrogen content, the better U.prolifera growth momentum, and then when a high concentration of urea contained in the culture system, U.prolifera grow better.3. Nutrient competition of Ulva prolifera with Ulva linza under different nitrogen sourcesIn the experiment on the competition of U.prolifera with Ulva linza, when adding organic matter, Ulva prolifera have a better growth than Ulva linza. When adding nitrate to the culture system, these two kind macroalgae show the obvious advantages than the organic matter group. U.prolifera is the dominant algae in the entire culture process.