The Growth Potential And The Characteristics Of Buoyancy Changes Of Microcystis In Lake Chaohu

The buoyancy and buoyancy regulation are very important to the dominance of blue-green algae. The mesocosm experiment was used to study Microcystis aeruginosa's mechanisms of circadian changes in buoyancy. Water samples were collected from estuary of Nanfeihe River of Lake Chaohu, and the temporal-spatial variation of concentration of chlorophyll and water pollution were inspected. Seasonal changes of volumes of pseudo-vacuole of Microcystis aeruginosa were determined.The nutritional characteristics of Lake Chaohu in the autumn was investigated, and the potential test of algal growth (AGP experimental) was used to study the growth potential of Microcystis in autumn in Chaohu.1. In the district of Nanfeihe River in Chaohu Lake, the temporal and spatial variation characteristics of water pollution were studied. Ammonia in Nanfeihe River estuary region existed at high concentration inducing the most serious pollution problem. The district of Nanfeihe River mouth was heavily contaminated, where ammonia nitrogen content were at higher concentration, and the highest point was at Nanfeihe River mouth, with the average ammonia concentration of 10.29 mg·L^-1. The concentration of ammonia was decreased outward from the region Nanfeihe River mouth, and was at relatively high concentration from April to July. This was might be related to the high temperature in summer in Nanfeihe River mouth, as well as the further input of the pollutant.2. The nutritional characteristics of the whole Chaohu Lake in the fall were investigated, and the potential test of algal growth (AGP experimental) was used to study the growth of Microcystis growth potential in Chaohu Lake. The eutrophication in West half of Chaohu Lake was higher than that of the eastern half lake. The microcyst algae's growth potential in samples from west half lake and east half lake were analyzed, and the results indicated that, microcyst algae in the west half lake water samples grew faster than algae in the water samples from east half lake. The AGP experiment indicated that the algae's biggest stock and the maximum specific rate of Microcyst were 7.93×10⁵cells/ml and 0.25/d respectively when sufficient phosphorus was added into the water samples; but algae's biggest stock and the maximum specific rate were 2.54×10⁶cells/ml and 0.38/d respectively when sufficient nitrogen was added. The relativities between nitrogen and Microcyst algae's biggest stock and the maximum specific rate were obviously higher than those between phosphorus and Microcyst algae's biggest stock and the maximum specific rate. These data indicated that compared with the phosphorus, the increase of nitrogen level in water body of Chaohu in the autumn could obviously enhance blue-green algae concentration to form water bloom.These results might suggest that the increase of nitrogen in water in the autumn might significantly promote the outbreak extent of cyanobacteria algal in the fall of Chaohu.3. The volumes of the pseudo-vacuole of Microcystis aeruginosa changed accordingly. In the morning with high intensity of light the volumes of the pseudo-vacuole increased slowly, and then decreased gradually in the afternoon with low light intensity. The volumes of the pseudo-vacuole also changed according to the content of protein and sugar of M. aeruginosa cells.4. The floating pressure being needed to keep 50% floating is different in different lakes. The relationship between floating rate and pressure distribution were studied for Microcystin in Chaohu.The study found that when the floating population was at 50% level the pressure needing generally was between 0.35Mpa to 0.4Mpa. The remainder volume of gas vesicles and the pressure distribution for Microcystin was studied. When the volume of gas vesicles decreased to 20%, the pressure generally was between 0.5Mpa to 0.6Mpa, and when the pressure was close to 0.9Mpa the air content of gas vesicles was near 1%, with gas vesicles almost entirely broken.5. The Pseudo-vacuole, carbohydrate and protein content in cyanobacteria cells were affected by nutritional status of cells. The illumination was the key factor for diurnal buoyancy regulation of cyanobacteria,the regulation mechanism was the accumulation and consumption of sugar.