The Influencing Study Of Environmental Factors On Freshwater Algae Growth In Yellow River

The Huajiangyingzi Reservoir is a plain-type reservoir, which water-body has the variation that is transiting from torrential flow to static water. In this paper, the raw water of reservoir was selected as objective and the forming algal characters by the effect of different environment factors were also analyzed. The changes of algae's and dominant species's composition, quantity were researched in different current speed water and the patterns of phytoplankton's growth changes were identified in the different flow water. It can be afforded the foundation and research basis for eutrophication in this Reservoir. From August in 2008 to July in 2009 the reservoir water was investigated, and the effect of water temperature, pH value, TN, TP and other physical and chemical indexes were mainly determined, while phytoplankton species, the number of other biological indicators were identified and counted, and planktonic algae composition, density, and other dominant species of different water flow were monitored at the same time in the laboratory.The results show that:Nitrogen concentration which was too high or too low were not conducive to the growth of algae, and the high concentration of nitrogen also had inhibiton on the growth of algae, the nitrogen of 5-10mg/L was more appropriate to the growth of algae; The ratio of KH2PO4 and KNO3 was 1:2, which was the most suitable for the growth of algae, and Phosphate is a limiting factor for growth and reproduction of algae.Above 30℃and below 4℃algae had almost no growth. At 15-25℃, the exponential growth phases were obvious, and with increasing temperature, algae proliferation rate was increased, but at 25℃was more suitable for algal growth and reproduction.In the light of 200-3000lx, the higher of light intensity, the faster of cell division, and the higher biomass. Scenedesmus obliquus'growth was limited by low light of 200,500lx and had the best growth under the 3000lx; from the outset, the growth of Chlorella pyrenoidosa was accelerated with the light enhanced, and also had restrictions under low light of 200,500lx.Under the certain conditions of temperature, light, water nutrient concentrations, the velocity v=0.22m/s was suited for algae growth in the experimental design flow, when v≤0.19m/s , Chla was increased with the increase of v, when v> 0.22m/s, Chla was decreased with the increases of v. It showed that there was existed a critical value of v0 between 0.19m/s and 0.22m/s. The orthogonal experiment of affecting algal growth's factors showed that the dynamic factors had the most significant on algae growth, the affecting order of four factors on the growth of freshwater algae was as follows: Velocity>> illumination = nutrient concentration > temperature.In the course of algae growth, hydrological, meteorological elements by changing the environmental factors in water, which can alter the subsistence of the alga, are directly or indirectly affected the occurrence of algal blooms. Therefore, in the management of Lake Eutrophication, the right way to change the hydrological, meteorological conditions, can more effectively achieve the control objective, and curb the development trend of eutrophication.