Assimilation efficiencies (AEs) of trace elements (Ag, Cd, Co, Se and Zn) i
n a marine deposit-feeding polychaete, Nereis succinea, from ingested sedim
ents were measured using a pulse-chase radiotracer feeding technique. Radio
labeled sediments were encapsulated and fed to the worms for 1 h, after whi
ch the worms were allowed to depurate their ingested materials for 3 d. The
ranges of AEs were 12 to 36 % for Ag, 5 to 44 % for Cd, 35 to 96 % for Co,
29 to 60% for Se and 21 to 59 % for Zn. Trace metal assimilation was littl
e affected by sediment source and sediment grain size. Metals (Ag, Cd, Co a
nd Zn) associated with anoxic sediments were assimilated with a significant
ly lower efficiency than metals from oxic sediments. The AE of Cd decreased
with the duration of sediment radiolabeling; AEs of Ag, Co, Se and Zn were
weakly affected by sediment aging. Metal uptake in worms from the dissolve
d phase was proportional to metal concentration in the dissolved phase, alt
hough there was some evidence of Cd and Zn regulation in response to an inc
rease in ambient concentrations. Uptake rate constants were highest for Ag,
followed by Zn > Co > Cd > Se. By incorporating metal influx from both the
dissolved and particulate (sediment) phases, a bioenergetic-based kinetic
model indicates that most (> 98 %) of the Cd, Co, Se and Zn in polychaetes
arises from sediment ingestion due to the high ingestion rates of these ani
mals and the low uptake rate of metals from the dissolved phase (porewater
or overlying water). For Ag, approximately 5 to 35 % is due to uptake from
the dissolved phase. Our study suggests that the establishment of sediment
quality criteria must consider sediment as a potentially important source f
or metal uptake in benthic invertebrates.