中文摘要：

采用室内培养方法，通过检测纤细裸藻生长、光合色素含量、抗氧化酶活性及DNA损伤（彗星实验）研究了高浓度氨氮胁迫对纤细裸藻（Euglenagracilis）的毒性效应，以期为氨氮的水生态风险评价以及藻类污水净化提供科学依据．结果表明，氨氮在所设定的浓度范围内抑制藻类的生长，浓度越高，抑制越明显，2000mg·L-1。时相比对照抑制率达55．7％；叶绿素含量随氨氮浓度增加先升高后下降，蛋白质含量与叶绿素变化趋势基本吻合；抗氧化酶系统中超氧化物歧化酶（SOD）和过氧化物酶（POD）活性随氨氮浓度增加而上升，2000mg·L-1。时比对照分别增加了30．7％和49．4％，提示氨氮胁迫可诱导抗氧化酶活性增加；彗星实验中，纤细裸藻细胞DNA损伤程度随氨氮浓度增加而加重，表明高浓度氨氮具有潜在的致突变性．

英文摘要：

Ammonia is among the common contaminants in aquatic environments. The present study aimed at evaluation of the toxicity of ammonia at high concentration by detecting its effects on the growth, pigment contents, antioxidant enzyme activities, and DNA damage （comet assay） of a unicellular microalga, Euglena gracilis. Ammonia restrained the growth of E. gracilis, while at higher concentrations, ammonia showed notable inhibition effect, the growth at 2 000 mg. L -1 was restrained to 55.7% compared with that of the control; The contents of photosynthetic pigments and protein went up with increasing ammonia dosage and decreased when the ammonia concentration was above 1 000 mg.L-1 ; In addition, there was an obvious increase in SOD and POD activities, at higher concentration （2 000 mg.L-1） , activities of SOD and POD increased by 30. 7% and 49.4% compared with those of the control, indicating that ammonia could promote activities of antioxidant enzymes in E. gracilis; The degree of DNA damage observed in the comet assay increased with increasing ammonia concentration, which suggested that high dose of ammonia may have potential mutagenicity on E. gracilis.