Shen Yinwu

The correlation between the variation of microcystin content and environment factors in Dianchi Lake

This paper analyzed the distribution and variation of microeystin ( M C) and physicochemical factors in Macun and Haidong bay of Dianchi Lake from April to December in 2003. The correlation of some physiochemical factors, including the concentration of total nitrogen, total phosphorous, dissolve oxygen, chlorophyll-a and Seechi depth, light intensity, pH, water temperature and dominance of Microcystis population, with microcystin was evaluated. Correlation analysis showed that the distribution of MC was significantly positive correlated with TN and N: P (P < 0. 01); and affected by Seechi depth, light intensity, dominance of Microcystis ( P < 0. 05). Multiple continuously factors analysis indicated that the distribution of MC in water of the two bays was mainly affected by total nitrogen, Seechi depth, chlorophyll-a, dissolve oxygen and total phosphorous (R-2= 0. 560, P < 0. 017).

The micobial mechanism of horizonal constructed wetland used to treated black-odor river.

To study the mechanism of horizontal subsurface constructed wetland, three full scale constructed wetland used to treat black-odor river were studied on pH, NH 4+-N , NO 2- -N, NO 3- -N and the number of ammonia oxidizing bacteria and nitrite oxidizing bacteria. Shaking conical flasks method was used to observe the transformation of NH +4-N under the aerobic condition. It was found that pH was alkalescence and changed slightly along with the length of con-structed wetland. Dissolved oxygen concentration ranged from 0.09 mg/L to 0.35 mg/L. The concentrations of ammonia nitrogen were characterized by a trend of decrease along with the length of all CWs. NO 3- -Nand NO -2 -Nwas always low along with the length of constructed wetlands. There were more ammonia oxidizing bacteria than nitrite oxidizing bacteria in LDP constructed wetland, whereas, the number of ammonia oxidizing bacteria was approximately equal to the number of nitrite oxidizing bacteria. In onsite artificial aeration system, it was found that partial nitrification and denitrification occurred in the CWS. Approximately 50% nitrogen was removed by partial nitrification and denitrifica-tion in two Lao duanpu constructed wetlands, and 20% in Beixia constructed wetland.

ISOLATION, IDENTIFICATION AND CHARACTERIZATION OF A STRAIN OF BLUE-GREEN ALGAE-LYSING BACTERIUM FROM LAKE DIANCHI

In this study, one high-effect algae-lysing bacterium was isolated and purified from Lake Dianchi, which was tabled as the strain DC-L5. The effect, host range, biosafety, lysing mechanism and lysing phenomenon of the algae-lysing bacteria were analyzed. Results were as the followings: The strain was identified as Bacillus pumilus by means of morphological observation and 16S rDNA sequence analysis in the CCTCC (China Center for Type Culture Collection). Toxicity test with mouse primarily showed that the strain was non-toxic. 4 kinds of DC-L5 cultures of different growth phases were added to Microcystis aeruginosa, and the strongest algae-lytic ability was found in the log phase of DC-L5 cultures, Chlorophyll a contents in culture of Microcystis aeraginosa reduced by 83.33% in 5 days. For the host range experiment, 4 kinds of dominant cyanobacteria in Lake Dianchi was researched, and average reduction rates of Chlorophyll a of 62.25% in cultures of Microcystis viridis, Microcystis wesenbergii, Aphanizomenon flos-aquae and Anabaena flos-aquae was observed with the highest 67.6% and the lowest 58.5% in 4 days respectively. After centrifugation and sedimentation, both the cells of bacteria and the cell-free suspension had strong algae-lytic activity, but the bacteria culture had the strongest algae-lytic activity, so it maybe showed the strain DC-L5 could directly cause the cyanobacterial cells agglomerated, sinked down and further lysed while the strain could excrete extra-cellular substances able to lyse cyanobacterial cells. In order to improve the algae-lytic activity of the strain DC-L5 to nature bloom, the bacteria cultures were added to nature cyanobacterial bloom dominant with Microcystis aeruginosa, which were sampled from Lake Dianchi and cultured in the lab. The result of nature bloom experiment showed the strain DC-L5 firstly disaggregated the cyanobacterial colony, reduced the floatability, degraded the pigments and then released inclusions of algal cells.

Effects of alkalinity variations on photosynthetic activity and exopotysaccharides of Chlorella pyrenoidosa

Effects of bicarbonate (HCO3-) alkalinity on the photosynthetic performance of Chlorella pyrenoidosa was investigated in present study. Photosynthetic activity, pigments, MDA and ultrastructure of Chlorella pyrenoidosa were measured for when they were cultured at two different alkalinities including 2.3mmol/L (ALK2.3) and 12.4mmol/L (ALK12.4), respectivily. At ALK2.3, photosynthetic activity was stimulated at the prophase of culture and then inhibited at the anaphase. At ALK 12.4, it represented the same phenomenon, but inhibition effects were weaker than those at ALK2.3. Ratios of Chl.b/Chl.a was increased, but Caro/TChl ratios was decreased at elevated alkalinities. The contents of MDA increased at ALK2.3 and decreased at ALK12.4. In addition, secretion of glycocalix-like layer was remarkably stimulated at elevated alkalinities. These results showed that elevated alkalinities promoted algae carbon assimilation and stimulated secretion of glycocalix-like layer. Carbohydrate could alleviate stresses at elevated alkalinities. Secretion of glycocalix-like layer could decrease the synthesis of excess products of photosynthesis and relieve feedback inhibition, which will increase the stress tolerance of C. pyenoidosa at elevated alkalinities.