Influence of a selective feeding behaviour by the blue mussel Mytilus trossulus on the assimilation of 109Cd 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 lo9Cd (Io9Cd-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 Io9Cd was mixed with unlabeled silt, and (2) labeled silt was mixed with unlabeled algae. Io9Cd-A~ was determined by a dual-tracer ratio ( 1 0 9~d / 2 4 1~m ) method (DTR) and based on the ingestion rate of '09Cd by the mussel (IRM) (total amount of Io9Cd ingested over the 4 h feeding period). As a result of the non-conservative behavior of u '~m , the DTR underestimated mussel lo9Cd-AEs as compared to the IRM. Therefore only IRM-determined 'O@C~-AE was considered further. When only algae was spiked, j d g c d -A~s were proportional to diet quality (DQ), (r = 0.98; p < 0.05) with maximum 'OgCd-AE occurring at the mussel's filter-feeding 'optimum' and where maximum carbon assimilation rates have been observed. However, for the spiked-silt exposures, I W c d -A~ was independent of DQ, with maximum values of -85 % occurring in all diets except for silt alone. lo9Cd-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 e x p o s~r e s .~~~C d -A E correlated with Io9Cd in mussel tissue (r = 0.63; p c 0.05), with the radiotracer assimilated from the silt-labeled matrices corresponding to the greatest amounts of Io9Cd activity within the mussel. These results suggest an active and passive assimilation of '09Cd from the algae and silt components of seston respectively. Active I o g c d -A~ will be proportional to DQ with maximum assimilation possibly occurring at the mussel's filter-feeding optimum. Passive 'OgCd-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.

Tracing cadmium contamination kinetics and pathways in oysters (Crassostrea gigas) by multiple stable Cd isotope spike experiments

“…In fact, at the 20 mg L -1 Cd exposure level the trophic transfer to oysters was~9% for Skeletonema costatum and ~ 20% for Tetraselmis suecica, whereas at the extremely high level of 200 mg L -1 it was ~5% for both species. Thus, by comparing studies, we can conclude that trophic Cd transfer in oysters mainly depends on algae species and that the exposure level appeared to be less significant which is consistent with trophic transfer studies conducted on mussel contamination (Wang and Fisher, 1996;Reinfelder et al, 1997;Arifin and Bendell-Young, 2000).…”

Modeling of cadmium bioaccumulation in two populations of the green mussel Perna viridis

“…The complex influence of the food environment on Cd assimilation in marine bivalves has been examined rather extensively. The AE of Cd in the mussel Mytilus trossulus from silt particles increased from 36% at 50 mg/L of silt to 92% with the addition of 20,000 cells/ml of the diatom T. pseudonana [39]. Chong and Wang [40] found that the presence of sediment reduced Cd assimilation from ingested diatoms by the green mussels.…”

“…An increase in food concentration from 1 to 15 mg/L during digestion resulted in a significant decrease in the AEs of metals bound with either sediments or diatoms. Therefore, concerns have been raised whether the Cd AEs determined under laboratory conditions that typically employed simplified experimental conditions are representative of those in the natural environment [39]. In addition, bivalves are highly selective filter feeders and are able to reject unwanted materials as pseudofeces.…”

Manganese content records seasonal upwelling in Lake Tanganyika mussels

“…Particulate sources of Mn should be available as bivalves accumulate metal in their tissues from the organic and inorganic components of their diet, actively through digestive processes, and passively through desorption (Arifin and Bendell-Young, 2000). However, the peak of (Mn/Ca) shell cannot be simply explained by the bimodal pattern of total Mn p variations.…”