Influence of a selective feeding behaviour by the blue mussel Mytilus trossulus on the assimilation of Cd-109 from environmentally relevant seston matrices
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| Authors: | Arifin, Z; Bendell-Young, LI |
| Year: | 2000 |
| Journal: | Marine Ecology-Progress Series 192: 181-193 |
| Title: | Influence of a selective feeding behaviour by the blue mussel Mytilus trossulus on the assimilation of Cd-109 from environmentally relevant seston matrices |
| Abstract: | The objective of this study was to determine the influence of a selective feeding strategy on the assimilation efficiency of Cd-109 (Cd-109-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 Cd-109 was mixed with unlabeled silt, and (2) labeled silt was mixed with unlabeled algae. Cd-109-AE was determined by a dual-tracer ratio (Cd-109/Am-241) method (DTR) and based on the ingestion rate of Cd-109 by the mussel (IRM) (total amount of Cd-109 ingested over the 4 h feeding period). As a result of the non-conservative behavior of Am-241, the DTR underestimated mussel Cd-109-AEs as compared to the IRM. Therefore only IRM-determined Cd-109-AE was considered further. When only algae was spiked, Cd-109-AEs were proportional to diet quality (DQ), (r = 0.98; p < 0.05) with maximum Cd-109-AE occurring at the mussel's filter-feeding 'optimum' and where maximum carbon assimilation rates have been observed. However, for the spiked-silt exposures, Cd-109-AE was independent of DQ, with maximum values of similar to 85% occurring in all diets except for silt alone. Cd-109-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. Cd-109-AE correlated with Cd-109 in mussel tissue (r = 0.63; p < 0.05), with the radiotracer assimilated from the silt-labeled matrices corresponding to the greatest amounts of Cd-109 activity within the mussel. These results suggest an active and passive assimilation of Cd-109 from the algae and silt components of seston respectively. Active Cd-109-AE will be proportional to DQ with maximum assimilation possibly occurring at the mussel's filter-feeding optimum. Passive Cd-109-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. |
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