The Preliminary Study Of Enteromorpha Absorption And Release Properties Of Nitrogen And Phosphorus And The Competition With Skeletonema Costatum

With the rapid development of economy and society, the water quality deterioration has been increasingly severe in the coastal area of China, while the red tide and alga bloom caused by eutrophication appeared much more serious. On the one hand, nutrients could be absorbed by macroalgae, then water was purified; on the other hand, accumulation of macroalgae such as Ulva pertusa and Enteromorpha may result in stinking of water which would influence the marine ecosystem and cause significant loss to fishery, breeding industry and tourism industry.The thesis concentrated on three problems in the lifecycle of Enteromorpha. Starting with the growth of Enteromorpha, in order to find out the nutrient kinetic characteristic; the absorption characteristic of Enteromorpha to two different N was compared through experiment determining the nutrient kinetic parameters (Km, Vmax) of Enteromorpha to N and P. Then take Initial inoculum dosage of Enteromorpha and Skeletonema costatum respectively as variable to analyse the competition of these two kinds of algae, in the mean time, find out the effect of Enteromorpha filtrate to the growth of Skeletonema costatum. The extinction process was simulated in the lab and the culture solution of the Enteromorpha was measured (N, P and DOC). Conclusions were summarized as follows:1. The experiment of the nutrient absorption characteristic of Enteromorpha shows that the absorption of Enteromorpha to NO3-N,NH4-N and PO4-P can be explained with Michaelis-Menten equation. The Km to NO3-N,NH4-N and PO4-P were respectively 376.32,283.11 and 24.57μmol·L-1,while the Vmax were 26.67,23.92 and 1.50μmol·g-1·h-1, respectively. The uptake rate of Enteromorpha to these three nutrients became bigger with the higher concentration of nutrient in the culture medium. The Ks of NO3-N is greater than the Ks of NH4-N, and the Vmax of NO3-N is greater than that of NH4-N. The rapid absorption rate of NO3-N and NH4-N at the beginning of the experiment indicated that the Enteromorpha had the characteristic of fast absorption and storage to the nutrients.2. The co-culturing competition experiment of Enteromorpha and Skeletonema costatum in which the initial inoculum dosage of Enteromorpha was taken as the variable showed that the growth of Skeletonema costatum was inhibited by Enteromorpha (p<0.01),and the inhibition became greater with the initial inoculums dosage of Enteromorpha. In the competition between Enteromorpha and Skeletonema costatum which was mainly nutrient competition, Enteromorpha was absolutely dominant. The experiment in which Skeletonema costatum was taken as the variable validated that the existence of Skeletonema costatum can influence the growth of Enteromorpha(p<0.05), while the difference between the two teams was not very big(p>0.05). The growth of Skeletonema costatum was suppressed in Enteromorpha filtrate (p<0.05), and the 8 days inhibition was stronger than the 4 days inhibition.3. The water condition experiment in the process of Enteromorpha extinction proved that the concentration of NO3-N and PO4-P did not rise after absorbed by Enteromorpha and degradation of Enteromorpha would not result in NO3-N and PO4-P pollution. In the mean time, the concentration enrichment of NH4-N induced the increase of DIN concentration but which was still in the range of TypeII sea water quality of China.The DOC concentration in the culture medium became higher.