太湖微囊藻对几种枝角类种群影响的实验生物学分析

Experimental biological approach to the effects of Microcystis on some cladoceran population in Lake Taihu

微囊藻是形成蓝藻水华最普遍的一种，不同枝角类受微囊藻的影响不同。实验从太湖梅梁湾分离天然的微囊藻，研究了其对长刺溞、隆线溞、短尾秀体溞和角突网纹溞四种枝角类存活和生殖的影响。在微囊藻食物浓度为1×10^6cells／ml，测得四种枝角类的半致死时间（LT50）分别为长刺溞3．03d、隆线溞3．79d、短尾秀体溞8．48d和角突网纹溞9．25d，体长较小的短尾秀体溞和角突网纹溞的半致死时间相对较长；实验过程中没有观察到长刺溞和隆线溞有新生幼体，而短尾秀体溞和角突网纹溞在少数几天里产出了少量新生幼体。以不同浓度微囊藻（0．5×10^6-8×10^6cells／m1）喂养枝角类，测得四种枝角类的24h半致死浓度（LC50）分别为：4．10×10^6、4．78×10^6、6．21×10^6和7．77×10^6cells／ml，参照以栅藻喂养的枝角类生长情况，可知太湖微囊藻对四种枝角类的存活和生殖有很强的负面作用，其中体长较大的长刺溞和隆线溞受的影响相对较大。

Microcystis is one of the most common and most studied bloom-forming cyanobacteria and a well-known producer of microcystins. Different cladocerans usually exhibited different responses to the toxicity of Microcystis. In the present study, the effects of toxic Microcystis from Lake Taihu were investigated by performing, acute tests on cladocerans（ Daphnia longispina , Daphnla carinata , Diaphanosoma brachyurum and Ceriodaphnla cornuta ） , using crude gicrocystis extract. On a diet of gicrocysits （ 1 10^6 cells/ml）, the median lethal time （LT50） of four cladocerans were 3.03,3.79,8.48 and 9.25 days, respectively. The longer LT50 were recorded for D. brachyurum and C. cornuta which have small size. Among the experiment, there was no new neonates of D. longispina and D. carinata, and few new neonates of D. brachyurum and C. cornuta. The 24h-LC50 of D. longispina, D. carinata, D. brachyurum and C. cornuta were 4.10 × 10^6, 4.78×10^6 ,6.21×10^6 and 7.77×10^6 cells/ml. So, the effects of Microcystis on the survivorship and fecundity of cladoceran population in Lake Taihu were very intense, and the effects of D. brachyurum and C. cornuta which have small size were relatfvely gently.