The use of the oyster Saccostrea glomerata as a biomonitor of trace metal contamination: intra-sample, local scale and temporal variability and its implications for biomonitoring Wayne A. Robinson, ab William A. Maher,* a Frank Krikowa, a John A. Nell c and Rosalind Hand c a Ecochemistry Laboratory University of Canberra, University Drive 2601 ACT Australia. E-mail: Bill.Maher@canberra.edu.au; Fax: þ61262015305; Tel: þ61262012531 b Faculty of Science, University of Sunshine Coast, Maroochydore DC 4558 QLD Australia c NSW Department of Primary Industries, Port Stephens Fisheries Centre, Taylors Beach 2316, NSW, Australia Received 1st October 2004, Accepted 24th December 2004 First published as an Advance Article on the web 9th February 2005 Cu, Cd, Zn, Pb and Se concentrations were measured in the bivalve mollusc Saccostrea glomerata (Iredale and Roughly) from two uncontaminated locations, Clyde River Estuary, Batemans Bay and Moona Moona Creek, Jervis Bay, to determine natural variability of metals associated with mass, gender, age, tissue type and site within location. Trace metals were also measured in the Clyde River Estuary over an 11 year period and in five other NSW estuaries (Hastings River, Hunter River, Georges River, Tillgerry Creek and Lake Pambula) over a 13-month period to determine temporal variability and if diploid and triploid oysters accumulate trace metals differently. There were few significant relationships between trace metal concentrations and mass and no significant differences in trace metal concentrations between female and male oysters. Younger oysters (1.3 years) had significantly higher copper concentrations and higher trace metal variability than mature oysters (3 years). Different tissues have different trace metal concentrations with muscle tissues having lower concentrations. Considerable inherent variability occurs in oyster cohorts. Analysing specific tissues did not reduce variability of trace metal concentrations. Comparison of trace metal concentrations at two sites within the Clyde Estuary showed a significant difference in zinc concentrations. Cu, Cd, Zn and Se concentrations were generally higher and less variable in triploids than diploids. Pb had a variable pattern of accumulation with no consistent elevation in diploids or triploids. Inter annual variability of trace metal concentrations was considerable and trace metal concentrations also fluctuated throughout an annual cycle with no clear seasonal trends. Measurement of trace metals at known contaminated locations showed that Saccostrea glomerata accumulates metals in response to contamination. Saccostrea glomerata meet most of the requirements to be a biomonitor of trace metal contamination as they are abundant, sessile/sedentary, easy to identify, provide sufficient tissue for analysis, and accumulate trace metals in response to contamination. However, as trace metal concentrations can vary with mass, age, estuary position, ploidy type and temporally, care must be taken to collect individual organisms of similar mass, age and ploidy type to minimise variability, and from similar consistent positions and times to allow for seasonal changes in environmental conditions. Trace metal concentration variability is higher in young animals, thus to reduce variability, older mature animals could be selected. However, with immature oysters there are no complications because of the effects of spawning i.e. sudden loss of trace metals or body mass. Introduction Australia is an arid country with limited freshwater resources. Over 90% of the population live within 50 km of the coast and most industries are located on coastal plains or adjacent to estuaries. 1 Similarly to most industrialised countries, urban and industrial waste enters into coastal waterways and has resulted in the degradation of aquatic ecosystems. 1,2 Trace metals and metalloids are of particular concern as discharges from coal-fired power stations, smelters, stormwater drains and sewage enter estuaries, which are important commercial and recreational fisheries. 3 Before threats to aquatic ecosystems can be evaluated, assessment of the contamination occurring needs to be under- taken. Measurements of contaminants can be made in water, sediment and biota. 4,5 Measurements of contaminants in waters and sediments only give a measure of potential expo- sure. As pointed out by Phillips, 4 measurements of contami- nants in biota need to be made if the bioavailable fraction is to be determined. Bivalves molluscs such as oysters and mussels are considered suitable for this purpose as they are hardy, sessile and do not regulate contaminants. 6 There are a number of extrinsic and intrinsic factors that affect trace metal accumulation and retention by aquatic organisms. Extrinsic factors include food availability, salinity, and temperature. 7 Mass, size, age, gender and reproductive status are examples of intrinsic factors. 5,7–12 Each of these factors, as well as the combined effect of all factors, governs the rate of metal uptake, assimilation and accumulation in organisms. The oyster Saccostrea glomerata (diploid and triploid forms), which is cultivated commercially along the NSW and Queensland coast, has been used extensively in Australia as a biomonitor of trace metal contamination. 13–20 However, little attention has been given to understanding the intrinsic factors that affect trace metal accumulation and retention by these oysters and designing sampling programs to minimise varia- bility due to these factors. This paper uses trace metal con- centration measurements of oysters, undertaken over the last 20 years to examine the influence of mass, gender, age and PAPER www.rsc.org/jem DOI: 10.1039/b415295f 208 J. Environ. Monit., 2005, 7 , 208–223 This journal is & The Royal Society of Chemistry 2005