Research On Floating Characteristics And Mechanism About Water-blooms Cyanobacteria

In recent years, outbreaks of algae-blooms in Taihu Lake cause wide attention, and the outbreak mechanism become focus of environmental study. Floating is the critical stage about algae bloom, if understand the floating mechanism, we can effectively control the outbreak of algae-bloom and ease the water crisis. It has great significance in studying water-blooms formatting mechanism, especially microcystis buoyancy regulation and vertical migration characteristics and mechanism induced algal blooms.In order to reveal the integrated biology and ecology mechanism about outbreak of algal blooms in shallow and medium-sized Taihu Lake, and to provide scientific basis in predicting algal bloom; As well as to establish technical principles of ecological system in controlling algal blooms, and to propose strategic prevention about cyanobacteria bloom and to provide a solid scientific basis for the realization of water ecological safety, temperature, pH, characteristics of surface water pollution and other factors about water-blooms formation were studied by in-situ monitoring and laboratory experiments, and combined effect about physical and chemical factors driving algal blooms floating in the water column were clarified, and the laws of floating algal blooms were revealed; the main driving factors of floating algal blooms were analysised, and the formation of algal blooms and transport law were revealed. In situ monitoring key physical and chemical factors in the Taihu Lake and algae blooms floating status characteristics were studied, laboratory simulation by using cylindrical reactor to simulate the process of algae floating, of the physical chemistry and the interaction of floating algae blooms, and interactions between floating algae bloom and the chemical and physical factors were explored, basing on the third topic "The whole lake process and the driving mechanism of algae growth and transport" of the national key basic research and development program "973"(No:2008CB418003).The main conclusions are as follows:(1) Dominant species was cymobacteria(microcystis) in Taihu Lake, and seasonal water bloom biomass reached 1.35×108 cells-L-1, there were also green algae, diatoms and hidden algae, competition existed between cyanobacteria and green algae;(2) In spring nitrate nitrogen, ammonia nitrogen, total nitrogen up to the maximal concentration, however total phosphorus, orthophosphate concentration and N/P varied indistinctively. (Representational difference analysis) RDA analysis expresses that effects of TN is bigger than TP on growth of microcystis; Remarkable correlation exists between TN, TP, DIN/SRP, NO2-N and biomass of microcystis. It should also simultaneously control nitrogen and phosphorus, particularly control DIN and SRP to control the blooms, it provides some scientific evidences in controlling water bloom;(3) There is no significant correlation between situ chemical factors and algae floating rate, the reason may be complex situ habitat and more complex factors. In addition to chemical factors, other hydraulic condition maybe affect algae floating rate;(4) Floating rate in the surface was significantly higher than it in the bottom, and in the day it is lower than that in the night, r22:00>r10:00>r14:00;(5) Changes about pH and phosphate were similar to the law that their values emerged in the surface and bottom was less than that in the middle;(6) Correlation analysis showed that carbohydrates, ammonia and dissolved oxygen were the main factors affecting algae floating in reactor, cyanobacteria adjust its float maybe by changing the carbohydrate concentration in cells and controlling synthesis of pseudo-bubble.