MEPS 129:177-187 (1995)  -  doi:10.3354/meps129177

Survival, weight-specific ammonia fluxes, blood ammonia levels and pH values were measured in individual mussels Mytilus edulis (L.) (n = 6 in each group) sampled after various acute exposures (max. 2 h) in normal or ammonia-enriched seawater. Ammonia influxes occurred when external ammonia was >=100 umol l^-1 when, within 5 min, mean blood ammonia levels increased significantly by an amount directly proportional to the medium ammonia concentration. Blood pH showed an initial alkalosis followed by a slow acidosis. Blood ninhydrin-positive substance (NPS) levels showed a less rapid medium-NH₄ concentration-dependent elevation and only the 100 mmol l^-1-treated mussels showed a significant increase in blood NPS after 5 min exposure. Within the 2 h test period, no mortalities occurred in any group, though 50% of the 100 mmol l^-1-treated group subsequently died after 6 h exposure. Apart from those in the most concentrated test medium, all mussels were seen to use apparently normal pumping behaviour, and it was concluded that M. edulis is an ammonia-tolerant species, capable of tolerating very high blood ammonia levels for extended periods of time. The toxic effect may be related more to the rate at which ammonia influx occurs, with the attendant level of disruption to the regulation of blood NPS levels, rather than to the actual blood ammonia concentration attained.

Ambient ammonia . Haemolymph ammonia . Haemolymph NPS . Mytilus edulis