Effects of environmental factors on radiocadmium uptake by four species of marine bivalves

404

402

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 Phasesupporting

confidence: 93%

Kinetic determinations of trace element bioaccumulation in the mussel Mytilus edulis

Wang¹,

Fisher²,

Luoma³

1996

404

402

“…3) may be interpreted correspondingly. In this context, it is possible that toxic ambient Zn levels may affect Cd accumulation irrespective of the Zn:Cd ratio (laboratory tests: Phillips 1976, Jackim et al 1977; field exposure: Bryan & Gibbs 1983; laboratory growth study : Fischer 1986b).…”

Section: Dependency Of Cadmium Accumulation On Ambient Concentrationmentioning

confidence: 99%

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

Fischer¹

1988

Juvenile blue mussels Mytilus edulis were cultivated in flow-through aquaria to investigate the influence of dissolved cadmium on cadmium accumulation (in terms of the Cd/shell-wt index). Where the ratio (by weight) of dissolved Zn to Cd remains within the range 25:l to 60:1, accumulation of Cd is not significantly influenced by dissolved Zn. Higher levels of concomitant Zn reduce the Cd/shellwt index. A lower ratio of Zn to Cd may slightly increase Cd accumulation. The Cd/shell-wt index is proportional to ambient levels of dissolved Cd up to 100 yg 1-' There were no significant effects on growth up to ca 30 pg 1-' Cd. Results corresponded to earlier experimental work and to field surveillance data reported in the literature. A procedure is suggested by which the concentration of dissolved Cd In natural environments may be estimated from 'mussel watch' data (Cd body burden, shell weight) and salinity. Cd accumulation in the mussel is described by the integral of the Cd/shell-rut index with growth of shells by weight. A model of biochemical accumulation of metals requires laboratory and field transplant experiments to be designed such that considerable growth is allowed in a new environment in order to approximate a new balance of metal residues in organisms in relation to ambient levels.

“…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%

“…The species-specific aspects of bioaccumulation could result from difference in feeding mode (filter feeding vs deposit feeding), exposure routes (dissolved vs food or benthic vs pelagic food web) and duration of exposure, as well as internal processes such as storage, detoxification and loss (Jackim et al 1977, Roesijadi & Robinson 1994, Wallace & Lopez 1996, Reinfelder et al 1997. Experimental studies have shown, for example, differences in metal uptake between suspension feeding and deposit feeding bivalves exposed in the same metal-ennched system (Crecelius et al 1982, Bryan 1985 or between benthos that feed from the water column versus benthos that feed on the sediments (Hare et al 1994, Warren et al 1998.…”

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.').