Trace metal uptake in cockles Anadara trapezium from Lake Macquarie, New South Wales

Abstract

Trace metal contamination of waters, sediments and animals in northern Lake Macquarie has been identified as a matter of concern by regulatory authonties. Expenmental procedures using the benthic bivalve Anadara trapezium (Sydney cockle) were developed to examine hypotheses relating to whether the cockle accumulated trace metals free in the water or from the sediment in which it is partially buried. Experiments were done in 1989 and 1991 to determine whether the concentration of trace metals in cockles was related to the concentration of metals in surrounding water or sediments. Pilot experiments indicated that it was poss~ble to translocate tubs of sediments from impacted areas to unimpacted areas with no loss of trace metals from contarnmated sediments and conversely with no increase in metals in uncontaminated sediments. Other expenments showed clearly that the presence of elevated levels of lead, copper and zinc in the water led to much greater levels in the cockles, irrespective of the concentration in surrounding sediments. There were no significant trends for cadmium. It was concluded that the sediments in which a cockle was living had little bearing on the levels of zinc, copper and lead that were accumulated in the cockle, whereas the surrounding waters had a considerable effect.

Sponges as sentinels: Metal accumulation using transplanted sponges across a metal gradient

“…Metals are often bound to particulates, both organic and inorganic, which are subsequently ingested by sponges and other suspension feeders, following sediment resuspension. In contrast to this assertion, there is some experimental evidence that metals in suspension may drive metal accumulation . Scanes transplanted sediment among locations within Lake Macquarie and concluded for the suspension–feeding clam ( Anadara trapezia ) that metals in suspension, rather than resuspended sediment, were the key determinant of metal accumulation.…”

“…In contrast to this assertion, there is some experimental evidence that metals in suspension may drive metal accumulation . Scanes transplanted sediment among locations within Lake Macquarie and concluded for the suspension–feeding clam ( Anadara trapezia ) that metals in suspension, rather than resuspended sediment, were the key determinant of metal accumulation. However, his experimental units were relatively small (tubs measuring <0.25 m −2 ), limiting the opportunity for resuspension of the sediment he transplanted.…”