MEPS 192:181-193 (2000)  -  doi:10.3354/meps192181

Influence of a selective feeding behaviour by the blue mussel Mytilus trossulus on the assimilation of 109Cd from environmentally relevant seston matrices

Zainal Arifin1,2, Leah I. Bendell-Young1,*

1Dept. of Biological Sciences, Simon Fraser University, 8888 University Ave., Burnaby, British Columbia V5A 1S6, Canada
2R & D Centre for Oceanology, LIPI, Poka, Ambon 97233, Indonesia
*Corresponding author. E-mail:

ABSTRACT: The objective of this study was to determine the influence of a selective feeding strategy on the assimilation efficiency of 109Cd (109Cd-AE) by the blue mussel Mytilus trossulus. Two complementary experiments which used 5 seston matrices of different seston quality (SQ) were implemented: (1) algae labeled with 109Cd was mixed with unlabeled silt, and (2) labeled silt was mixed with unlabeled algae. 109Cd-AE was determined by a dual-tracer ratio (109Cd/241Am) method (DTR) and based on the ingestion rate of 109Cd by the mussel (IRM) (total amount of 109Cd ingested over the 4 h feeding period). As a result of the non-conservative behavior of 241Am, the DTR underestimated mussel 109Cd-AEs as compared to the IRM. Therefore only IRM-determined 109Cd-AE was considered further. When only algae was spiked, 109Cd-AEs were proportional to diet quality (DQ), (r = 0.98; p <\ 0.05) with maximum 109Cd-AE occurring at the mussel's filter-feeding 'optimum' and where maximum carbon assimilation rates have been observed. However, for the spiked-silt exposures, 109Cd-AE was independent of DQ, with maximum values of ~85% occurring in all diets except for silt alone. 109Cd-AE for the silt-only exposure was 36%, suggesting that digestive processes which occur in diets of both algae and silt were not operating as effectively in the silt-only exposures.109Cd-AE correlated with 109Cd in mussel tissue (r = 0.63; p <\ 0.05), with the radiotracer assimilated from the silt-labeled matrices corresponding to the greatest amounts of 109Cd activity within the mussel. These results suggest an active and passive assimilation of 109Cd from the algae and silt components of seston respectively. Active 109Cd-AE will be proportional to DQ with maximum assimilation possibly occurring at the mussel's filter-feeding optimum. Passive 109Cd-AE will be dependent on amounts of metal associated with the inorganic component of seston, with digestive processes that are activated in the presence of algae concurrently desorbing inorganic cadmium. Although both components of the diet will be important for determining amounts of Cd that can be potentially assimilated from seston by filter-feeding organisms, the contribution from the inorganic component of seston will likely overwhelm that from the organic fraction. Therefore, predictive models of metal accumulation by seston-ingesting organisms need to consider the role of both seston components in contributing to amounts of metal ultimately assimilated by the organism.

KEY WORDS: Mytilus trossulus · 109Cd-AE · Inorganic seston · Organic seston

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