Toxicity of ammonia to larvae and juveniles of the geoduck clam Panopea japonica.

The effects of total ammonium nitrogen (TAN) on hatching, metamorphosis and survival of the geoduck clam Panopea japonica in early life stages (larvae and juvenile) were studied. Ammonia had a significant impact on the hatching ratio at different concentrations. The survival ratio of larvae and juveniles was reduced significantly along with increasing TAN concentration. The maximum acceptable toxicant concentration (MATC) of TAN for larval relative growth ratio was 0.49 mg/L (equivalent to 0.013 mg/L of un-ionized ammonia), and EC50 for survival after 192 h was 1.04 mg/L (equivalent to 0.028 mg/L of un-ionized ammonia). The MATC of TAN on the metamorphosis ratio of P. japonica was 0.93 mg/L (equivalent to 0.030 mg/L of un-ionized ammonia). In juveniles, there was no significant difference in survival ratios with TAN concentrations ranging from 4.07 to 7.01 mg/L. MATC for survival was 7.01 mg/L (equivalent to 0.22 mg/L of un-ionized ammonia), and the LC50 after 96 h was 13.96 mg/L (equivalent to 0.44 mg/L of un-ionized ammonia). Our findings provided information of the larval and juvenile P. japonica in response to the TAN stress. [ABSTRACT FROM AUTHOR]