总氨态氮对海湾扇贝幼体存活和生长的影响

为确定海湾扇贝Argopecten irradias育苗用水的水质指标,进行了总氨态氮对海湾扇贝幼体存活和生长的影响试验。结果表明:在pH为8.20~8.30、水温为21.5~22.5℃、盐度为27~28条件下,总氨态氮对海湾扇贝受精卵孵化率的24 h半数有效浓度(EC_(50))为3.089 mg/L(非离子氨态氮NH_3-N=0.194mg/L),最大毒物允许浓度(MATC)为0.86~1.80 mg/L(非离子氨态氮NH_3-N=0.054~0.113 mg/L);在pH为7.95~8.10、水温为23~25℃、盐度为27~28条件下,总氨态氮对浮游期幼虫(2日龄)存活的48 h半致死浓度(LC_(50))为7.801 mg/L(NH_3-N=0.342 mg/L),96 h LC_(50)为2.445 mg/L(NH_3-N=0.107mg/L),144 h LC_(50)为1.294 mg/L(NH_3-N=0.057 mg/L);对浮游期生长的144 h EC_(50)为2.023 mg/L(NH_3-N=0.089 mg/L);浮游期的MATC为0.37~0.66 mg/L(NH_3-N=0.016~0.029 mg/L);总氨态氮浓度≤2.03 mg/L(NH_3-N≤0.089 mg/L)时,均有幼体变态为稚贝;变态期(眼点出现至变态成稚贝)幼体眼点出现率的192 h EC_(50)为1.460 mg/L(NH_3-N=0.064 mg/L),变态率的408 h EC_(50)为1.927 mg/L(NH_3-N=0.085 mg/L)。研究表明,根据各个时期的EC5推测,海湾扇贝育苗期间,在pH为7.95~8.10条件下总氨态氮浓度控制在0.40 mg/L(NH_3-N=0.018 mg/L)以下最佳,本研究结果为完善海湾扇贝生态学及育苗期间的水质调控技术提供了参考。

Impact of total ammonia nitrogen on survival and growth of larval and juvenile bay scallop Argopecten irradians

The effect of total ammonia nitrogen evel on survival and growth of larval and juvenile bay scallop Argopecten irradians was studied to regulate water quality during bay scallop larva rearing. The results showed the 24 h median effective concentration (EC50) of total ammonia nitrogen was 3.089 mg/L(NH3-N=0.194 mg/L) for hatching rate, with the maximum acceptable toxicant concentration(MATC)of 0.86-1.80 mg/L(NH3-N=0.054-0.113 mg/L) at water temperature of (21.5±22.5)℃, pH 8. 20-8. 30, and a salinity of 27-28. The LC50 of total ammonia nitrogen for 2-day-old pelagic larvae was 7. 801 mg/L(NH3-N=0.342 mg/L) in 48 h, 2. 445 mg/ L (NH3-N=0.107 mg/L) in 96 h, and 1. 294 mg/L(NH3 -N=0.057 mg/L) in 144 h, with EC50 of 2. 023 mg/L (NH3-N=0.089mg/L)in 144 h at pH 7. 95-8. 10, temperature 23-25℃ and a salinity of 27-28. The pelagic larvae had maximum allowable toxicant concentration (MATC) of 0.37-0.66 mg/L(NH3-N=0.016-0.029 mg/L) and the metamorphic larvae were observed at total ammonia nitrogen concentrations of 2.03 mg/L(NH3-N≤0. 089 mg/L) or lower. During metamorphosis stages(from eye-spot larva to juvenile), there was 192 h EC50 of 1. 460 mg/L(NH3-N=0.064 mg/L), 408 h EC50 of 1. 927 mg/ L (NH3-N=0.085 mg/L). It is suggested that total ammonia nitrogen concentration be controlled under 0.40 mg/L(NH3-N=0.018 mg/L) at pH 7.95-8.10, which provides some reference for bay scallop developmental ecology and water quality control in larva rearing.