The Preliminary Study On Uptake Of Nutrients By Ulva Prolifera And Competition Of Ulva Prolifera With Red Tide Algae

With the development of economy, society and people’s living standard, a largenumber of industrial and agricultural wastewater, breeding water and sewagedischarged into the sea, so the eutrophication degree of coastal water increased. Inrecent years, the green tide globally occurred and it continuously outbroke in Chinafrom2007to2013. This ecological disaster endangered the coastal water quality,ecological system and economic development. Therefore, Ulva Prolifera was selectedas experimental object and researched by controlled experiment in the laboratory. Theuptake properties of nutrients by U.Prolifera were studied to know the requirement ofnutrients during the process of U.Prolifera growth and reproduction. The competitionof U.Prolifera with two kinds of red tide algae were also discussed. Through theabove experiments, the nutrients uptake characteristics of U.Prolifera and itsinfluence factors were preliminary understood to provide scientific basis for theprediction and prevention of U.Prolifera green tide. The competition of U.Proliferawith red tide algae can furnish experimental basis and theoretical support for thereason why U.Prolifera large-scale outbreak with the co-existence of U.Prolifera andmicroalgae. The main work and conclusions are as follows:1. The experiment about uptake properties of nutrients by U.Prolifera under thecondition of different nitrogen and phosphorus ratio (N/P) showed that, U.Proliferacan quickly absorb and reserve a large amount of nutrients in a short time. Theoptimal condition of U.Prolifera growth was from16to24. The weight of U.Proliferaincreased in3d and6d, respectively corresponding to rapid absorption of nutrients in1~2d and4~5d. The U.Prolifera growth was not same because the absorption ofnutrients was different. Later in experiment, nitrogen restrained when N/P was from12to24, and phosphate restrained when N/P was from28to40.2. The experiment on the interaction between nitrate and urea absorption byU.Prolifera showed that, U.Prolifera can take advantage of nitrate and urea in waterat the same time. When the concentration of nitrate and urea in water was same, U.Prolifera gave priority to absorb nitrate. Nitrate and urea would inhibit theabsorption of each other, but the inhibition action of urea was weaker.3. The impact of heavy metals on U.Prolifera uptake of nitrate was explored.The results showed that, when in low concentration, Cu(II)(<0.03mg/L) and Zn(II)(<0.10mg/L) had a promoting effect on the U.Prolifera uptake of nitrate. When theconcentration of heavy metal reached a certain concentration (Cu(II)>0.10mg/L andZn(II)>0.20mg/L), the heavy metal had inhibition effect, and the more theconcentration, the stronger the inhibition. Pb(II) had inhibition effect on U.Proliferauptake of nitrate, and the inhibition bacame stronger when the concentration increased.When the concentration of added heavy metal was0.20mg/L and0.50mg/L, thetoxicity of Cu(II) on the U.Prolifera uptake of nitrate was the strongest, followed byPb(II), and Zn(II) was the smallest. When the concentration of added heavy metal was1.00mg/L, the toxicity of Cu(II) was the strongest, followed by Zn(II), and Pb(II) wasthe smallest.4. In the experiment on the competition of U.Prolifera with red tide algae, weselected the common red tide dinoflagellates in China coastal port water,Amphidinium carterae and Prorocentrum dentatum. U.Prolifera had inhibition effecton the growth of A.carterae, and the effect became stronger when the biomassincreased. The growth of U.Prolifera was also suppressed. There was nutritioncompetition effect between U.Prolifera and A.carterae. When U.Prolifera wasco-cultured with P.dentatum. U.Prolifera had inhibition effect on the growth ofP.dentatum, and the more the biomass, the stronger the effect. When the biomass ofU.Prolifera reached1.5g, its inhibition on P.dentatum was obvious. The growth ofU.Prolifera was not suppressed obviously. There was less nutrition competition effectbetween U.Prolifera and A.carterae. U.Prolifera as a kind of green tide algae, caninhibit the growth and reproduction of microalgae, so when U.Prolifera co-exist withred tide algae, it can still outbreak.