Anadara trapezia from Lake Macquarie NSW was investigated for its potential use as a bioindicator of cadmium, copper and zinc pollution. The study consisted of four main parts.

• Quantitative assessment of the reproductive cycle of A. trapezia
• Measurement of the accumulation of cadmium, copper and zinc in A. trapezia from polluted and unpolluted environments in order to establish whether A. trapezia is a net accumulator or regulator of trace metals. Factors affecting accumulation of metals; mass, shell length, height, width, volume, gender and gonad and somatic condition were examined.
• Measurement of temporal variation in cadmium, copper and zinc concentrations in A. trapezia between August 1995 to July 1996. Possible factors influencing the temporal variations of the trace metals; mass, gender, tissues distribution, gonad and somatic condition, reproductive cycle, temperature and salinity were examined.
• Investigation whether A. trapezia store and detoxify of trace metals by formation of metallothioneins.

Spawning in A. trapezia occurs from spring to summer and gametogenesis late autumn to winter. A short resting period was recorded in April and May. The mature oocytes were maximum in summer and minimum in winter. Spawning in A. trapezia was probably triggered by warmer water temperature.

A. trapezia was found to accumulate significantly higher concentrations of cadmium and copper from a polluted estuarine environment but not zinc. This suggests that A. trapezia is a net accumulator of cadmium and copper but a regulator of zinc. Cadmium, copper and zinc concentrations were found to be higher in smaller animals (presumably younger) than larger ones. The accumulation of zinc was found to depend on organism mass, morphological measurements (shell length, height, width and volume), gender and gonad and somatic condition. Copper accumulation was weakly related with mass while cadmium was independent of the organisms’ physiology. Gender had no effect on copper and cadmium accumulation.

All three metals showed significant temporal variations. The temporal variations of zinc was related to mass fluctuation which was triggered by the availability of food supply and spawning in warmer months and gametogenesis in cooler months. The temporal variation of cadmium and copper concentrations were not related to mass or the reproductive cycle of A. trapezia.

A cadmium binding protein of molecular weight 10,000 Da was isolated from intestine tissues of A. trapezia by using gel filtration HPLC. 61.8% of cadmium was bound to this protein. Further separation of this 10,000 Da protein by anion-exchange chromatography resolved this protein into three isoforms. The first isoform had a similar retention time to standard rabbit liver MT-1. The second isoform had a retention time similar to MT-2. Amino acid sequences need to be measured to establish whether the separated proteins are true metallothioneins.

A. trapezia can be used as a bioindicator of cadmium and copper, but the effect of mass on copper concentration needs to be considered. A. trapezia was found to regulate zinc, therefore, A. trapezia is not a suitable bioindicator for zinc.