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Inter-Research |
Kinetic determinations of trace
element bioaccumulation in the mussel Mytilus
edulis
Wang WX, Fisher NS, Luoma SN
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
dissolved phase was 1.53% for Ag, 0.34% for Am, 0.31% 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-1. 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 particle-reactive 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 partition coefficients for suspended particles and the
assimilation efficiency in mussels of ingested trace elements; values range
between 33 and 67% for Ag, 5 and 17% for Am, 47 and 82% for Cd, 4 and 30% for
Co, and 17 and 51% for Zn. KEY WORDS: Bioaccumulation ·
Kinetic modeling · Metals · Mussels · Americium · Cadmium · Cobalt · Selenium
· Silver · Zinc Published in MEPS Vol. 140
(1996) on September 12 |
