氮源对塔玛亚历山大藻生长和毒性的影响

Effects of nitrogen sources on the growth and toxicity of Alexandrium tamarense

为了掌握不同氮源对塔玛亚历山大藻(Alexandrium tamarense)生长和毒性的影响,实验选定硝酸钠、氯化铵、尿素和甘氨酸作为4种氮源,在温度和光强分别为20℃和200μmol photons·m-2·s-1的培养箱中,采用人工海水一次性培养藻细胞,培养基N和P浓度分别以F/20加富,并收集对数期细胞用于斑马鱼胚胎48 h急性毒理实验。结果表明:4种氮源都可以支持细胞生长,但不同氮源培养的藻细胞生长速率不同,表现为铵氮(0.25 d^(-1))>硝氮(0.20 d^(-1))>尿素=甘氨酸(0.12 d^(-1));4种氮源对细胞色素的含量无显著影响;与对照组(胚胎培养液)相比,在细胞密度为2×10~4cells·mL^(-1)时,塔玛亚历山大藻细胞粗提液对斑马鱼胚胎表现出显著的毒性作用,可造成胚胎的凝固、发育迟缓、卵黄膜破裂、卵黄囊水肿及尾巴弯曲等;当细胞密度增加到8×10~4cells·mL-1时,毒性进一步增加,且4种氮源对毒性的影响出现显著差异,表现为硝氮>尿素=甘氨酸>铵氮。综上所述,塔玛亚历山大藻的生长和毒性对氮源的响应机制存在差异,但4种氮源都支持生长,因此,在环境变化和水体营养盐结构复杂化的情况下,塔玛亚历山大藻仍可维持生长并持续爆发藻华,对生态环境造成威胁。

In order to understand the effect of nitrogen sources on the growth and toxicity of harmful dinoflagellate Alexandrium tamarense,four nitrogen sources（nitrate,ammonium,urea and glycine） were added into artificial seawater enriched with F/20 and cells were batch-cultured at 20 oC and 200 μmol photons·m-2·s^-1.Cells of A.tamarense at exponential phase were collected to test the acute toxic effect on zebrafish embryo in 48 hours.The results showed that four nitrogen sources were all utilized by A.tamarense,but the growth rate was different,being ammonium（0.25 d^-1） nitrate（0.20 d^-1） urea = glycine（0.12 d^-1）.However,the pigment contents were not influenced.Compared with the control group（embryo medium）,the rude extract of A.tamarense at 2×10^4cells·mL-1 had significantly teratogenic effects on the zebrafish embryos,resulting in embryo coagulation,developmental retardation,vitelline membrane rupture,yolk sac edema and tail bending.When the cell density increased to 8×10^4cells·mL^-1,the toxicity increased accordingly,moreover,a significant difference was found among the four nitrogen sources,showing nitrate urea = glycine ammonium.In summary,A.tamarense can maintain relatively high growth rate and make algal blooms outbreak continuously regardless of environmental changes,which threatens the ecological environment in coastal areas.