Studies on the Water Bloom of Toxic Alga, Microcystis Viridis

对毒藻绿微囊藻的水华进行了野外和室内试验研究。1988-1990年夏季至秋季，对霞aura湖微囊藻优势种的变化进行了野外调查。夏季以铜绿假单胞菌和水花假单胞菌为主，秋季以绿芽假单胞菌为主。铜绿假单胞菌（M. aeruginosa）的立地产量与水温呈高度相关，而绿芽假单胞菌（M. viridis）和绿芽假单胞菌（M. wesenbergii）的立地种群与水温无相关性。采用批量培养的方法，研究了温度和光照对绿芽胞杆菌N-1和绿芽胞杆菌NIES 102特定生长速率和产藻量的影响。病毒分枝杆菌N-1和病毒分枝杆菌NIES 102分别在25℃和30℃条件下具有最大的特定生长率。与其他种类的微囊藻相比，绿芽胞杆菌可以在较低的温度下生长。M. viridis N-1在2000 lx以上的连续光照下不能生长，但在周期性光照下可以生长。绿芽胞杆菌的特定生长速率低于其他种类的微囊藻。这些结果表明，绿芽胞杆菌在夏季比其他微囊藻更难占优势。此外，我们还研究了重金属对微囊藻生长的影响。在液体培养基中测定了铜、镉和钴对绿芽胞杆菌（M. aeruginosa K3A）、绿芽胞杆菌（M. viridis）、仿水藻（Anabaena affinis）和绿藻小球藻（Chlorella ellipsoidea）生长的毒性。铜对M. aeruginosa K3A、M. viridis、A. arrinis和C. ellipsoidea的EC_<50>（有效浓度，50%抑制对照特定生长速率）分别为0.019muM、0.023muM、0.018muM和0.58muM，与镉和钴相比，铜对这些菌的生长毒性最大。3种蓝绿藻对铜的敏感性比绿藻C. lipsoidea高30倍。EDTA、EGTA等螯合剂对铜毒性有较强的还原作用。Kasumigaura湖地表水铜浓度为0.017muM，与蓝藻EC_<50>基本一致。湖水中铜绿假单胞菌K3A的EC_<50>值是液体中的3倍。从这些事实可以推测，湖水中的天然配体刺激了蓝绿藻的生长，造成了藻华。少

We studied the water bloom of toxic alga Microcystis viridis in the field and laboratory experiment. A field study was carried out from summer to fall between 1988-1990 to clarify the change in the dominant species of Microcystis in Lake Kasumigaura. M. aeruginosa f. aeruginosa and M. flos-aquae were dominant in te summer, but M. viridis became dominant in the fall. A high correlation was found between the standing crop of M. aeruginosa and the water temperature, but the standing croup of M. viridis and M. wesenbergii showed no correlation in the water temperature. Effects of temperature and illumination on the specific growth rates and the algal yield of M. viridis N-1 and M. viridis NIES 102 were studied with a batch culture. Maximum specific growth rates of M. viridis N-1 and M. viridis NIES 102 were observed at 25 and 30^0C, respectively. M. viridis could grow at lower temperatures than the other species of Microcystis. M. viridis N-1 could not grow at the continuous illumination o … More f 2,000 lx but could grow at the periodic illumination. The specific growth rate of M. viridis was lower than those of other species of Microcystis. These results suggested that M. viridis was more difficult to dominate than other Microcystis in summer.Moreover, we studied the effect of heavy metals on the growth of Microcystis spesies. Toxicity of copper, cadmium and cobalt on the growth of blue-green algae M. aeruginosa K3A, M. viridis, Anabaena affinis and green algae Chlorella ellipsoidea was determined in the liquid medium. The EC_<50> (effective concentration, 50% inhibition of the specific growth rate of control) of copper for M. aeruginosa K3A, M. viridis, A. arrinis, C. ellipsoidea were 0.019muM, 0.023muM, 0.018muM and 0.58muM, respectively, Copper showed the severest toxicity to the growth of these glgae compared with cadmium and cobalt. The sensitivity to copper of three species of blue-green algae was 30 times higher than that of the green algae C. llipsoidea. Chelating agents such as EDTA and EGTA showed the stroug reducing effect on the copper toxicity. Copper concentratin in the surface water of Lake Kasumigaura was 0.017muM, which was the almost same to the value of EC_<50> for blue-green algae. However, the EC_<50> of copper for M. aeruginosa K3A in the lake water was found to be 3 times larger than in the liquid medium. From these facts, it is assumed that natural ligands in the lakewater stimulated the growth of blue-green algae to make algal bloom. Less