Influence of sediment metal spiking procedures on copper bioavailability and toxicity in the estuarine bivalve Indoaustriella lamprelli.

The effect of three methods for spiking sediments with Cu on the reburial behavior, mortality, and tissue Cu accumulation of a lucinid bivalve (Indoaustriella lamprelli) and the influence of the bivalve on the sediment geochemistry were investigated. Methods used to create Cu concentration gradients were direct spiking with and without pH adjustment to pH 7 and also dilution of sediment, previously spiked with Cu and adjusted to pH 7, using a low-Cu sediment (known to produce the lowest pore-water Cu concentrations). The presence of the bivalve within Cu-spiked sediment increased the flux of Cu and Mn to overlying waters at high Cu concentrations (550 microg/g). Bivalve behavioral response, metal accumulation, and mortality varied with the method by which Cu was spiked. In direct Cu-spiked sediment, the bivalves were inactive at concentrations of 550 and 1,100 microg/g, with mortality induced in sediment spiked with 1,100 microg/g (pH 6.5-7.1). Complete bivalve inactivity was observed only at 1,100 microg/g in direct Cu-spiked sediment with pH adjustment, whereas percentage reburial was reduced to 30% at 1,100 microg/g for sediment prepared by the dilution method. Relative reburial rates in the three spiked sediment types (direct << direct pH-7 < dilution) were proportional to dissolved Cu concentrations in the overlying water. Bivalve reburial, in addition to the method of Cu addition, affected tissue Cu accumulation. Inhibition of bivalve reburial decreased the amount of accumulated Cu, confounding relationships between tissue Cu and pore water, overlying water, or extractable metal fractions.