Dynamics of the phycotoxin domoic acid: accumulation and excretion in two commercially important bivalves

Batch cultures of the toxigenic diatom Nitzschia pungens Grunow f. multiseries Hasle were fed to blue mussels (Mytilus edulis ) and deep sea Atlantic scallops (Placopecten magellanicus ) to elucidate conditions under which domoic acid (DA) was accumulated and excreted (depurated). Mussels accumulated the toxin to a maximum level of 13 mu g/g, at rates of 0.21 to 3.7 mu g/h/g dry weight. Accumulation efficiency (the proportion of accumulated DA to estimated net uptake) ranged from 1-5%. The highest filtration rate of 1.71/h occurred at concentrations of 4-8 x 10 super(6) Nitzschia) cells/l with no formation of pseudofeces. Depuration rates between fed and starved mussels over a 2 h test period were the same. The depuration rate of domoic acid was about 17%/d and did not account for the low uptake efficiencies, so it is suggested that most of the DA is lost from mussels in the solution during the feeding process.