Mytilus edulis as a quantitative indicator of dissolved cadmium. Final study and synthesis

403

407

ABSTRACT. Laboratory experiments employing radiotracer methodology were conducted to determine the assimilation efficiencies from ingested natural seston, the influx rates from the dissolved phase and the efflux rates of 6 trace elements (Ag, Am, Cd, Co. Se and Zn) in the mussel Mytilus edulis. A kinetic model was then employed to predict trace element concentration in mussel tissues in 2 locations for which mussel and environmental data are well described: South San Francisco Bay (California, USA) and Long Island Sound [New York, USA). Assimilation efficiencies from natural seston ranged from 5 to 18": for Ag, 0.6 to 1% for Am, 8 to 20% for Cd, 12 to 16% for CO, 28 to 34% for Se, and 32 to 41 ' :, for Zn. Differences in chlorophyll a concentration in ingested natural seston did not have significant impact on the assimilation of Am, CO, Se and Zn. The influx rate of elements from the dissolved phase increased with the dissolved concentration, conforming to Freundlich adsorption isotherms. The calculated dissolved uptake rate constant was greatest for Ag, followed by Zn > Am -; Cd > CO > Se. The estimated absorption efficiency from the d~ssolved phase was 1.53 % for Ag, 0.34 % for Am, 0.31 X for Cd, 0.11 % for CO, 0.03"' for Se and 0.89% for Zn. Salinity had an inverse effect on the influx rate from the dissolved phase and dissolved organic carbon concentration had no significant effect on trace element uptake. The calculated efflux rate constants for all elements ranged from 1.0 to 3.0% d-' The route of trace element uptake (food vs dissolved) and the duration of exposure to dissolved trace elements (12 h vs 6 d) did not significantly influence trace element efflux rates. A model which used the experimentally determined influx and efflux rates for each of the trace elements, following exposure from ingested food and from water, predicted concentrations of Ag. Cd, Se and Zn in mussels that were directly comparable to actual tissue concentrations independently measured in the 2 reference sites in national monitoring programs. Sensitivity analysis indicated that the total suspended solids load, which can affect mussel feeding activity, assimilation, and trace element concentration in the dissolved and particulate phases, can significantly influence metal bioaccumulation for particlereactive elements such as Ag and Am. For all metals, concentrations in mussels are proportionately related to total metal load in the water column and their assimilation efficiency from ingested particles. Further, the model predicted that over 96% of Se in mussels is obtained from ingested food, under conditions typical of coastal waters. For Ag, Am, Cd, CO and Zn, the relative contribution from the dissolved phase decreases significantly with increasing trace element parhtion coefficients for suspended particles and the assimilation efficiency in mussels of ingested trace elements, values range between 33 and 67% for Ag, 5 and 1 7 % for Am, 47 and 82% for Cd, 4 and 30% for CO, and 17 and 51 ?h for Zn.

Section: Trace Element Uptake From the Dissolved Phasementioning

confidence: 99%

Kinetic determinations of trace element bioaccumulation in the mussel Mytilus edulis

Wang¹,

Fisher²,

Luoma³

1996

403

407

“…Accumulation of Cd is proportional to dissolved Cd, and a Cd/shell-wt index of 5 yg g-' relates to mussels grown in 1 pg 1-' dissolved Cd and 15 %o salinity (Fischer 1988).…”

Section: Field and Laboratoly Workmentioning

confidence: 99%

“…1). In summer 1984, juveniles were suspended from navigational buoys (additional test on the influence of TBT-antifouling paint: no effect on Cd accumulation), and retrieved after 2 mo growth in their new environment (importance of growth : Fischer 1988).…”

Section: Field and Laboratoly Workmentioning

confidence: 99%

See 1 more Smart Citation

Cadmium in seawater recorded by mussels: regional decline established

Fischer¹

1989

Self Cite

The mussel Mytilus edulis is used as a quantitative indicator of dissolved cadmium in the water of the K~eler Forde in comparison with a reference site in the b e l e r Bucht (Western Baltic Sea). As recorded by the mussel, the baseline Cd concentration in the h e l e r Bucht declined from ca 65 ng I-' in 1980 to 35 ng I-' in 1984. Recalculations of literature data suggest that the 1975-1976 Keler Bucht level was ca 110 ng 1-' The 'normal' distribution of dissolved Cd in the Kieler Forde was characterized by ca 140 % of the baseline in the harbour area, 85 % in the inner fjord, and 120 to 140% in the outer fjord. Other patterns indicated by the mussel are considered to reflect occasional coincidence of hydrographic stagnation and specific events (harbour dredging, sewage pollution, industrial discharges). After collapses of oxybiotic life the mussel indicated approximately half normal Cd levels, but there is doubt that 'mussel watch' records may be relied upon if the mussels had been affected by anoxic conditions. 'Mussel watch' estimates of chemical water quality documented a downward trend of dissolved Cd in the SW Kieler Bucht, which corresponds to the information available from analytical seawater chemistry. According to the regional hydrography, t h s is conceived to reflect a decline of dissolved Cd and possibly other metals on a broader geographical scale. Implications suggested relate to the following of natural fluxes in the management of chemically similar wastes.

“…Bivalves concentrate many metals in their soft tissue (e.g. Jackim et al 1977, Borchardt 1983, Fischer 1988) and the tissue metal levels represent a time-integrated response to bioavailable metal in food and water (bioaccumulation). In addition to the influence of metal concentration, bioaccumulation can be complicated by external environmental factors and internal biological processes (Luoma 1989, Rainbow et al 1990, Wright 1995.…”

Section: Introductionmentioning

confidence: 99%

Uptake and loss kinetics of Cd, Cr and Zn in the bivalves Potamocorbula amurensis and Macoma balthica:effects of size and salinity

Lee¹,

Wallace²,

Luoma³

1998

115

Radiotracer studies were employed to quantitat~vely compare the biokinetics of uptake from the dissolved phase (influx rates) and loss (efflux) between 2 bivalves, Potamocorbula arnurensls and Macoma balthica, and among the metals Cd, Cr and Zn. Effects of salinity on influx rate were evaluated in these 2 highly euryhaline species as were effects of animal size on uptake and loss. Metal speciation and biological attributes interacted to differentiate bioaccumulation processes among metals and between species. Influx rates of the 3 metals (pg g-I [dry wt] d-') increased linearly with dissolved metal concentrations. Influx rates of Zn in both clams were 3 to 4x those for Cd and 15x those for Cr. However, influx on the basis of free ion activities would be faster for Cd than for Zn. Relative influx rates among the metals were similar in the 2 bivalves. But, absolute influx rates of all 3 metals were 4 to 5 x greater in P. arnurensis than in M. balthica, probably because of differences in biological attributes (i.e. clearance rate or gill surface area). As salinity was reduced from 30 to 5 psu, the influx rate of Cd for P. amurensis increased 4-fold and that for M. balthica increased 6-fold, consistent with expected changes in speciation. However the influx rates of Cr in both clams also increased 2.4-fold over the same range, indicating a biological contribution to the salinity effect. Influx rates of Zn were not significantly affected by salinity. Weight specific metal influx rates (pg g-' [dry wt] d-') \Yere negatively correlated with the tissue dry weight of the clams, but most rate constants determining physiological turnover of assimilated metals were not affected by clam size. The exception was the rate constant for Cd loss, which resulted in faster turnover in large M. balthica than in smaller clams. The rate constant of loss for P. arnurensis increased in the order of Cd (0.011 d-') < Zn (0.027 d-l) < Cr (0.048 d-l). This was different from the hierarchy of rate constants for M. balthica: Zn (0.012 d-l) < Cd (0.018 d-l) < Cr (0.024 d.').