“水华”微囊藻的种群动力学和微囊藻毒素的归趋

Freshwater "bloom" like marine "red tide" has been generating the prominent environmental problems in the world. It still remains unknown for understanding the occurrence mechanisms of algal bloom which is concomitant toxin release and transfer, thus the practice for prevention and control is confronted with more difficulties. In natural waters, the happening of bloom is depended upon many kinds of environmental factors like temperature, light, nutrients. Constant climate condition, the proper background concentration of alga tend to bring about the outbreak of bloom as well. As for this project we paid attention to the aspects as follows: 1) confirming the leading factor on the general investigation basis, 2) finding out the "promoter" for cells to duplicate speedily, and 3) learning the toxin-releasing appearance from algal cells (condition, rate, number). Therefore, we fell together room and field conditions on the survey of cyanobacterial blooms respectively and acquired a great many data. Under room conditions, we cultured the single Microcystis strain in homemade grown systems imitating the blooming process and toxin-producing pattern. The results showed that ammonium in concentration below 2.54 mgoL-1 or above 15.8mg·L-1 would inhibit Microcystis growth, but that ranging from 7mg·L-1 to 15mg·L-1would trigger the cyanobacterium into a "eruptive" growth. The maximal toxin yield was observed at stationary stage of the algal growth. We conducted a year-round survey on 2 eutrophic ponds in which the Microcystis bloom was observed to occur in recent years. Some novel and interesting results were obtained by detailed analysis. For example, in the two ponds, ammonium and phosphate appeared to play the leading role in promoting Microcystis bloom to break out respectively, however, both ammonium and phosphate possessed "threshold values" of which below or over would restrict the bloom formation. Appropriate N/P ratio was necessary to blooming. The peaks of Microcystis toxicity presented itself later than those of the growth. Moreover, the higher the growth peaks, the longer the delay time of the toxicity peaks. The toxin production implied somewhat ecological signification in that it might inhibit the growth of other organisms and resume superiority of population itself. MCYST-RR was the major microcystin isomer, oppositive to the MCYST-LR dominance in the mixed component according to the publications at hand. MCYST-YR was checkable hard all year round which was identical to the reports. In addition, it was noted that there was transformation of unknown microcystin isomer into MCYST-RR. The investigation was characterized with all-round pursuit of Microcystis blooming and microcystin changing patterns in nature and performed within a duration as long as 2 years by more than 30 persons and over 100 sampling arrangements. Therefore, the results would provide dependable evidences for elucidating the mechanism of Microcystis bloom in its development and disappearance, accompanied with microcystin isomers changes in nature. During the research, we carried out the new explorations in cyanophage and vacuole of cyanobacteria. We reported the first cyanophage isolated in China and preliminarily investigated the temporal and spatial distribution of cyanophages in freshwater. Overall 14 research（including 2 in SCI journals）papers were published. In addition, 7 were accepted by journals and 11 abstracts were adopted by national congresses. During the time, 8 postgraduates were educated in the research, additional 4 obtaining MSc. degree.

定点、定期采集微囊藻水华，调查分析导致囊细胞爆发性生长的“促进”因子；寻找和发现新毒株、新毒素；研究藻毒素产生与环境因子的关系；毒素从藻细胞释放的规律；分析有毒水华对水质的影响和毒素的归趋；选取出2-3种对毒素富积能力强的生物控制水华。在理论辖沂净肪骋蛩赜胨⑸哪承┠谠诹担谟τ蒙辖峁┲卫硭囊谰莺褪侄巍?..