The Effect Of Environmental Factors On The Gowth Of Microcystis

In recent years, as the rapid economic development, a great amount of pollutants riches in nutrients such as nitrogen and phosphorus is poured into the water, making the lake eutrophication is more and more serious. Algal bloom is the most common ecological problems that come with the lake eutrophication. Microcystis blooms, as its advantage in the number and frequency of occurrence, has become the most concerned and studied algal blooms. Currently, there have been many studies on the formation of algal blooms. The common understanding is that Microcystis’ own physiological characteristics as well as the environmental factors such as temperature, light, nutrients and many other organism is the most important factors and the inter-relationship of those factors are very complex.In this article, we choose unicellular Microcystis aeruginosa and wild Microcystis colonies for the study. Design three factors and three levels orthogonal of nutrition, light, temperature, a two factors and two levels orthogonal of particle size and nutrient levels, a nutritional stress experiment. Observe their growth performance of Microcystis aeruginosa and wild Microcystis colonies under different environmental conditions inorder to get a deeper understanding of the physiological characteristics of Microcystis. Find out the main environmental factors that affect the growth condition of Microcystis, lead to the further explanation of why cyanobacteria, especially Microcystis, becomes the dominant species of the algal blooms. The results show that:1). Nutrition, light, temperature all effect the specific growth rate of Microcystis aeruginosa significantly (P<0.01) and the P consumption (P<0.05). As for the final biomass and specific growth rate, the influence order is light>temperature>nutrition; as for the P consumption, the influence order is light>nutrition>temperature. Microcystis aeruginosa get their biggest final biomass and specific growth rate under260mgN/L,3000lx,30℃. The specific growth rate of Microcystis aeruginosa is negative when light is0lx, shows no growth and a certain degree of decomposition, the P consumption is negative as well for the Microcystis aeruginosa release a certain amount P into the culture medium.2). The wild Microcystis colonies diffused to smaller colonies and eventually become unicellular Microcystis. Chla content of the Microcystis goes up and down, up and down, so there are two peaks and the second is much higher. The particle size of the wild Microcystis colonies shows a significant effect on the Chla content (P<0.05). The Chla content of the big and small colonies various under differenr nutrient levels (P<0.01). As for the small colonies, the two peaks of the Chla content get higher when the nutrient levels rise. As for the small colonies, the result is just the opposite, the best growth performance shows at the D nutrient level. Those results show the small colonies are more changeable to the environment nutrient level.3). Compared to the wild Microcystis colonies, the Chla content of unicellular Microcystis aeruginosa is much higher under nutrient stress. N, P stress is not conducive to the synthesis of Chla and inhibit the growth of both unicellular Microcystis aeruginosa and wild Microcystis colonies (P<0.01). Wild Microcystis colonies are more tolerant to N stress while unicellular Microcystis aeruginosa is more tolerant to P stress. C stress doesn’t effect the wild Microcystis colonies significantly (P>0.05). C stress has no significant effect on the wild Microcystis colonies Chla content (P>0.05), while unicellular Microcystis aeruginosa Chla content have significant difference compared to AI (P<0.05). Wild Microcystis colonies are more tolerant to N stress.