Assimilation of Po-210 by the mussel Mytilus edulis from the alga Isochrysis galbana

Marine invertebrates are thought to accumulate Po-210 primarily from their food. In this study, a pulse-chase methodology was used to examine the assi milation and depuration of Po-210 by Mytilus edulis from the common marine alga Isochrysis galbana. The digestion of Po-210 from I. galbana occurred v ia a biphasic process, characteristic of a rapid (extracellular) and slow ( intracellular) digestion typical of marine bivalves. The mantle/gill and fo ot have no known digestive role, yet their Po-210 specific activities incre ased after 24 h. It is proposed that this increase in Po-210 specific activ ity was related to Po-210 being incorporated into these tissues from Po-210 assimilated from I. galbana during extracellular digestion. It is proposed that the linear loss of Po-210 previously accumulated by control mussels w as related to the continual state of renewal and replacement of cellular pr oteins, with Po-210 turnover and metabolism governed by protein turnover an d metabolism. M. edulis' assimilation efficiency of Po-210 from the Po-210- labelled alga was calculated to be 17.2 +/- 2.1%, and thus similar to that of Ag, Cd, Co, Se and Zn by bivalves from other marine algae species. It is proposed that the assimilation efficiency of Po-210 is a function of prote in assimilation.