Browsing by Author "Jeffree, RA"

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    Accumulation of radionuclide and metal contaminants in flesh and osteoderms of estuarine crocodiles (crocodylus porosus): pathways and histories of catchment-specific exposure
    (EDP Sciences, 2002-02) Jeffree, RA; Markich, SJ; Hammerton, KM; Russell, RA
    Flesh and osteoderms of estuarine crocodiles (C. porosus) from Kakadu National Park, Northern Australia, were analysed for a range of metals, including uranium, to assess their capability for accumulation, in relation to their catchment-specific exposure to i) uranium mine effluents and mineralisation and ii) lead shot ammunition through their consumption of fauna shot by the traditional owners of the Park. Uranium in osteoderms was significantly (P<0.05) elevated in the East Alligator River catchment, that contains the Ranger and Jabiluka uranium mine sites, relative to two other adjacent catchments. The mean concentrations of other elements in flesh and osteoderms were also significantly (P<0.05) different between catchments. Linear discriminant analysis was used to demonstrate that multi-element signatures in both flesh and osteoderms could be used to classify individual crocodiles to their respective catchments. This approach may be useful for the identification of source catchments of itinerant 'nuisance crocodiles' that find their way into Darwin Harbour, close to dense human habitation. Lead concentrations were significantly (P<0.05) enhanced in flesh and osteoderms of crocodiles sampled within two areas hunted with guns using Pb ammunition. Enhanced ratios of Pb:Ca in the annual laminations of their osteoderms are consistent with their history of continual exposure to elevated anthropogenic Pb sources. Subsequent experimental studies have demonstrated the ability of the crocodilian stomach to retain ingested Pb shot, that is readily solubilised and absorbed into the blood and then archived in the contemporary osteodermal lamination. © EDP Sciences, 2002
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    Comparison of concentrations of natural and artificial radionuclides in plankton from French Polynesian and Australian coastal waters
    (The Institution of Engineers Australia, 1994-05-01) Poletiko, C; Twining, JR; Jeffree, RA
    Zooplankton samples from French Polynesian and Australian coastal waters were analysed for natural and artificial radionuclides. Quality control was assured by correlating replicate analyses between three laboratories and by participation in an international intercomparison exercise. Pu239/240 was detected sporadically among samples from both regions, with the highest levels being more consistently found in Tuamotu-Gambier samples. The artificial radionuclides Cs-137, Cs-134, Sr-90 and Co-60 were not detected. Of the natural nuclides, Ac-228 was detected in shallow continental waters off Northern Australia and an inverse relationship (P<0.02) was established between plankton density and their Po-210 concentration.
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    Crocodile bones as archives of pollution exposure: lead contamination in Kakadu National Park, and what's in Sweetheart's Osteoderms?
    (Australian Nuclear Science and Technology Organisation, 2001-08-23) Jeffree, RA; Markich, SJ; Hammerton, KM; Russell, RA
    Experimental findings made it then possible to evaluate the hypothesis that the estuarine crocodile osteodermal laminations would record enhanced blood lead concentrations resulting from the ingestion of lead shot. At about 140 days following lead shot ingestion, two osteoderms were removed from each exposed and control animal. SIMS analysis of Pb-208 and Ca-42 signal intensities was then performed on sections that were prepared and analysed using similar methods previously used on field-collected specimens (Twining et al., 1999). These initial findings are consistent with the hypothesis that incremental laminations of the osteoderm will archive a lead signal that responds to enhanced levels of lead in the animal's blood during its life. SEM analysis identified the laminated structure of the osteoderm, however microprobe analysis did not detect appreciable amounts of even Ca and P, although the organic matrix was obviously present. It is proposed that this anomalous result is due to the preparatory tanning of the skin, in acid solution, that could be expected to leach elements from the organic matrix. An analogy is drawn with the decalcified skeletons in the bodies of the Druid sacrifices due their deposition in acid swamp waters in the UK. The challenge is now to sample osteoderms from large crocodiles in the Finniss River, preferably in close proximity to the Rum Jungle mine site, where any archived pollution signal would be more intense, and then repeat this analytical investigation of the osteodermal history of contaminant loadings. © 2002 Commonwealth of Australia
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    The Finniss River: a natural laboratory of mining impact- past present and future
    (Australian Nuclear Science and Technology Organisation, 2002-08) Markich, SJ; Jeffree, RA
    The Rum Jungle uranium-copper mine in tropical northern Australia has been a source of acid rock drainage contaminants since the 1950s which have had adverse impacts on the receiving waters of the Finniss River. Mine site remediation began in 1982 followed by long-term monitoring of water quality and flow based on daily measurements within the Finniss River system. A decade or more after the initiation of these remedial activities a set of investigations have been completed that have measured the post-remedial ecological status of the Finniss River system relative to this environmental benchmark. These studies have also been complemented by studies on various other ecological endpoints. Moreover the Finniss River system has provided unique opportunities for broader scientific goals to be pursued. Because it has been so well-monitored it can be viewed as a natural laboratory to investigate the impacts of acid rock drainage on tropical freshwater biodiversity. The scientific papers presented at this symposium address a broad spectrum of issues that are directly related to environmental sustainability and mining. The topics range across future contaminant scenarios and their predicted ecological impacts the various metrics used to assess ecological detriment to biodiversity the abilities of laminated biological structures to act as archives of pollution history and also spin-off applications in environmental and wildlife management. Furthermore the participation of many stakeholders in open discussion during the symposium provided an important set of views and opinions on the needs for future studies in the Finniss River system.
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    From Rum Jungle to Wismut - Reducing the environmental impact of uranium mining and milling
    (The Institution of Engineers Australia, 1994-05-01) Zuk, WM; Jeffree, RA; Levins, DM; Lowson, RT; Ritchie, AIM
    Australia has a long history of uranium mining. In the early days, little attention was given to environmental matters and considerable pollution occurred. ANSTO has been involved in rehabilitation of a number of the early uranium mining sites, from Rum Jungle in Australia's Northern Territory to Wismut in Germany, and is working with current producers to minimise the environmental impact of their operations. ANSTO's expertise in amelioration of acid mine drainage, radon measurements and control, treatment of mill wastes, management of tailings, monitoring of seepage plumes, mathematical modelling of pollutant transport and biological impacts in a tropical environment are summarized.
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    The IAEA handbook on radionuclide transfer to wildlife
    (Elsevier B.V., 2013-07-01) Howard, BJ; Beresford, NA; Copplestone, D; Telleria, D; Proehl, G; Fesenko, S; Jeffree, RA; Yankovich, TL; Brown, JE; Higley, K; Johansen, MP; Mulye, H; Vandenhove, H; Gashchakk, S; Wood, MD; Takatam, H; Andersson, P; Dale, P; Ryan, J; Bollhöfer, A; Doering, C; Barnett, CL; Wells, C
    An IAEA handbook presenting transfer parameter values for wildlife has recently been produced. Concentration ratios (CRwo-media) between the whole organism (fresh weight) and either soil (dry weight) or water were collated for a range of wildlife groups (classified taxonomically and by feeding strategy) in terrestrial, freshwater, marine and brackish generic ecosystems. The data have been compiled in an on line database, which will continue to be updated in the future providing the basis for subsequent revision of the Wildlife TRS values. An overview of the compilation and analysis, and discussion of the extent and limitations of the data is presented. Example comparisons of the CRwo-media values are given for polonium across all wildlife groups and ecosystems and for molluscs for all radionuclides. The CRwo-media values have also been compared with those currently used in the ERICA Tool which represented the most complete published database for wildlife transfer values prior to this work. The use of CRwo-media values is a pragmatic approach to predicting radionuclide activity concentrations in wildlife and is similar to that used for screening assessments for the human food chain. The CRwo-media values are most suitable for a screening application where there are several conservative assumptions built into the models which will, to varying extents, compensate for the variable data quality and quantity, and associated uncertainty. © 2012, Elsevier Ltd.
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    Plankton as monitors of radionuclides in the South Pacific
    (Australian Institute of Nuclear Science and Engineering, 1994-11-16) Twining, JR; Poletiko, C; Jeffree, RA
    Aims and rationale Zooplankton are known for their ability to accumulate a variety of elements to levels up to 104 times higher than their concentration in associated water. Thus, they have been sampled for use as biomonitors of radionuclides in the waters surrounding the French nuclear test sites at Mururoa and Fangataufa as well as in the more populated areas of French Polynesia (Figure 1). Given the global distribution of fallout from atmospheric testing in past decades it was important to determine background levels within similar latitudes. For this reason, sampling was also undertaken in Australian coastal waters. These organisms also have a fundamental importance in marine foodchains, particularly in relation to biomagnification of isotopes such as polonium to humans, and are also significant factors in the biogeochemistry of radionuclides in the marine environment. This paper summarises our results to date on the concentrations of natural and artificial radionuclides in zooplankton from the two regions, and discusses the implications of the findings to dose assessment in areas of low planktonic productivity. Methods Samples were collected between 18/8/90 and 29/6/92 from waters of the Maquesas (n = 12), Society (10), Tuamotu-Gambier (6) and Austral (2) island groups in French Polynesia as well as from the Gulf of Carpentaria (27) and the waters off Sydney (3) (Figure 1). Depths between the surface and 100m were sampled by trawled plankton nets and the filtered volumes determined using meters positioned at the opening of the nets. Samples were dried at 60°C for 7 days to give an average FW/DW ratio of 7.5. The dried samples were split between laboratories for replicant analyses and quality control. Gamma analyses were performed using shielded, HP Ge, coaxial detector systems and efficiencies determined using mixed nuclide standards in similar geometry to the samples. For the alpha emitters, 239/240Pu and 2l0Po, extra replicates were also analysed by the Service Centrale de Protection Centre les Rayonnments lonisants, France as part of our quality assurance program. Detection efficiency was determined using 238Pu or 208Po yield tracers. Results and Discussion Average zooplankton densities varied from 0.47 to 50.0 mg (DW)/m3. The lowest densities were recorded in samples from French Polynesian waters which were between 1 and 2 orders of magnitude lower than those measured in Australian samples. In all regions Copepods (primarily Calanoid then Podoploid) numerically dominated the taxonomic composition of the samples. As part of the quality assurance program, the results for replicate sample analyses for individual isotopes were linearly regressed between each laboratory. In all comparisons the regression coefficients were highly significant (p < 0.005, r= 0.54 to 0.95). These results imply good quality control despite the errors implicit in such low level determinations and the fact that split, not homogenised, samples were used. The results for specific activities detected by each laboratory showed that: • I3i>Cs, 137Cs, 60Co and 90Sr were not detected. This in part reflects the low concentration factor for some elements, but also indicates that levels of these isotopes in French Polynesian waters were not high enough to generate significant concentrations in the plankton; • 239/240Pu was detected in some samples from each region except the Austral Archipelago and the waters off Sydney. The measured low levels ranged from 0.05 to 2.15 Bq/kg DW with the highest levels consistently found in the Tuamotu-Gambier group. Subsequent observations showed that these high values were from samples collected during a single trip in 1991; • 228Ac was only detected in samples from the Gulf of Carpentaria which is consistent with their collection from a shallow coastal environment. Its progenitor, 232Th, is derived from erosion of continental masses but is quickly adsorbed onto particles and drops out of solution once it enters the marine environment; and • Average 210Po concentrations were inversely correlated with plankton density (figure 2). This result was consistent with the greater removal rate for Po by adsorption onto sinking biogenic particulates (eg faecal pellets) which are produced more frequently in higher productivity regions. This is combined with the major source of 210Po being decay of atmospheric 222Rn and aerial deposition of its progeny 2l0Pb directly into the oceans. Ingrowth of 210Po then occurs with a 138 day half-life. It is proposed that plankton in lower productivity regions are exposed to and thus accumulate higher concentrations of 210Po. One hypothesis arising from the higher concentration of 2l0Po in plankton is that secondary consumers, eg fish, could be expected to have similarly increased 2l0Po concentrations in lower productivity areas. It follows that humans consuming these fish could therefore be expected to be exposed to higher dose from 210Po due to consumption of these fish. Some support for this hypothesis can be found in the limited data bases for edible fish in low productivity regions around the Marshall Islands, located in the mid North Pacific Ocean. The values from two studies, when compared with global averages for commercial fisheries, indicate higher concentrations in both pelagic and reef fish from the low productivity area. When this result is compounded by the higher intake of fish as a proportion of total diet in these environments and by the proposed changes in the transfer factors for ingested polonium in the latest ICRP models, then the dose from 210Po may become radiologically significant.
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    Po-210 and Pb-210 concentration factors for zooplankton and faecal pellets in the oligotrophic South-West Pacific
    (International Atomic Energy Agency, 2004-10-24) Jeffree, RA; Szymczak, R; Peck, GA
    In a previous study on zooplankton sampled from very low productivity waters of French Polynesia [1], their Po-210 concentrations were found to be unexpectedly elevated, compared to values measured in marine zooplankton from various other geographical regions of the world. For the French Polynesian samples their Po-210 concentrations also increased appreciably as their biomass declined. A simple conceptual and mathematical model, that incorporated the established role of zooplankton faecal pellets in the removal of Po-210 and particle-reactive radionuclides and stable metals from the water column, could capture the shape of this empirical relationship between Po-210 concentration and their biomass and also explained the biomass-related mechanism that increases Po-210 concentrations in zooplankton [2]. Similarly, a field investigation in the Timor Sea showed that a range of particle-reactive elements showed elevated water concentrations as particle removal rates, as inferred from Th-234: U-238 disequilibria, reduced in the euphotic zone [3]. However, in these previous studies simultaneous in situ measurements of a range of parameters valuable in assessment of the role of zooplankton in the biogeochemical cycling of particle-reactive elements like Po-210 and Pb-210 were not made. Here we report preliminary results of a field study, that was undertaken in the oligotrophic waters of the South-West Pacific between New Caledonia and Fiji, where we simultaneously measured a) zooplankton biomass and their faecal pellet production rates, b) Po-210 and its progenitor Pb-210 in water, zooplankton and their faecal pellets and c) particle flux rates using U-238:Th-234 disequilibria, to further assess the role of zooplankton in Po-210 and Pb-210 biogeochemistry in the euphotic zone of oligotrophic systems [4]. Zooplankton sampled from the oceanic region of the South-West Pacific between Fiji and New Caledonia had biomasses ranging from 0.1 to 7.1 mgDW/m3, with a median value of 3.6 and mean of 2.65 mgDW/m3. Their faecal pellet production rates were measured on board and varied between 1.82.10-4-3.78.10-3 g dry faecal pellet. g dry zooplankton-1. hour-1, median ). Their measured Po-210 and Pb-210 concentrations were 830-2655 Bq.KgDW-1 and 44-617Bq. KgDW-1, respectively. Po-210 and Pb-210 concentrations in zooplankton varied between 565-1736 Bq.Kg dry weight-1 and 47-551 Bq.Kg dry weight-1, respectively. Po-210 concentration factors that only varied between 1.3 –3.3. 105 were elevated compared to the IAEA recommended value of 3.104 based on previous values [5]. Similarly, Pb-210 concentration factors ranging from 0.9-9.1. 104, were considerably elevated compared to the IAEA recommended value of 1.103 [5], indicating the presence of a further concentrating mechanism. Our results for Po-210 and Pb-210 show a consistency with published values [5,6] in that the concentration factor for Po-210 is elevated relative to Pb-210, but contrast with previous reported values in both being elevated by about an order of magnitude. Their comparably elevated concentrations in faecal pellets suggest that enhanced concentrations in zooplankton are a reflection of the heightened concentrations in their dietary phytoplankton.
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    Po-210 and Pb-210 concentration factors for zooplankton and faecal pellets in the oligotrophic South-West Pacific
    (International Atomic Energy Agency, 2006) Jeffree, RA; Szymczak, R; Peck, GA
    In a previous study on zooplankton sampled from very low productivity waters of French Polynesia [1], their Po-210 concentrations were found to be unexpectedly elevated, compared to values measured in marine zooplankton from various other geographical regions of the world. For the French Polynesian samples their Po-210 concentrations also increased appreciably as their biomass declined. A simple conceptual and mathematical model, that incorporated the established role of zooplankton faecal pellets in the removal of Po-210 and particle-reactive radionuclides and stable metals from the water column, could capture the shape of this empirical relationship between Po-210 concentration and their biomass and also explained the biomass-related mechanism that increases Po-210 concentrations in zooplankton [2]. Similarly, a field investigation in the Timor Sea showed that a range of particle-reactive elements showed elevated water concentrations as particle removal rates, as inferred from Th-234: U-238 disequilibria, reduced in the euphotic zone [3]. However, in these previous studies simultaneous in situ measurements of a range of parameters valuable in assessment of the role of zooplankton in the biogeochemical cycling of particle-reactive elements like Po-210 and Pb-210 were not made. Here we report preliminary results of a field study, that was undertaken in the oligotrophic waters of the South-West Pacific between New Caledonia and Fiji, where we simultaneously measured a) zooplankton biomass and their faecal pellet production rates, b) Po-210 and its progenitor Pb-210 in water, zooplankton and their faecal pellets and c) particle flux rates using U-238:Th-234 disequilibria, to further assess the role of zooplankton in Po-210 and Pb-210 biogeochemistry in the euphotic zone of oligotrophic systems [4]. Zooplankton sampled from the oceanic region of the South-West Pacific between Fiji and New Caledonia had biomasses ranging from 0.1 to 7.1 mgDW/m3, with a median value of 3.6 and mean of 2.65 mgDW/m3. Their faecal pellet production rates were measured on board and varied between 1.82.10-4-3.78.10-3 g dry faecal pellet. g dry zooplankton-1. hour-1, median ). Their measured Po-210 and Pb-210 concentrations were 830-2655 Bq.KgDW-1 and 44-617Bq. KgDW-1, respectively. Po-210 and Pb-210 concentrations in zooplankton varied between 565-1736 Bq.Kg dry weight-1 and 47-551 Bq.Kg dry weight-1, respectively. Po-210 concentration factors that only varied between 1.3 –3.3. 105 were elevated compared to the IAEA recommended value of 3.104 based on previous values [5]. Similarly, Pb-210 concentration factors ranging from 0.9-9.1. 104, were considerably elevated compared to the IAEA recommended value of 1.103 [5], indicating the presence of a further concentrating mechanism. Our results for Po-210 and Pb-210 show a consistency with published values [5,6] in that the concentration factor for Po-210 is elevated relative to Pb-210, but contrast with previous reported values in both being elevated by about an order of magnitude. Their comparably elevated concentrations in faecal pellets suggest that enhanced concentrations in zooplankton are a reflection of the heightened concentrations in their dietary phytoplankton.
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    Tolerance of fish to contaminated habitats: underlying mechanisms probed with isotopic tracers
    (International Atomic Energy Agency, 2006) Jeffree, RA; Markich, SJ; Twining, JR; Gale, S
    Future scenarios indicate agricultural and industrial expansions in major river basins and enhanced world populations focusing in coastal watersheds [1], particularly in SE Asia. Such scenarios are consistent with increasing concentrations of various contaminants, including metals and radionuclides. It is important to assess the likely impacts on fisheries, their response and possible adaptability to enhanced contaminant levels and the implications for resulting transfer factors and contaminant levels in fisheries, that can be the major sources of subsistence and livelihood for coastal communities. The likely future responses of fisheries to projected increases in contaminant loadings over broad geographical scales can be probed through the employment of currently highly contaminated aquatic environments. Such a system with these attributes, that we have investigated periodically since the early 1970s, is the Finniss River in tropical northern Australia, that has continued to receive acid mine drainage from the Rum Jungle U/Cu mine since the 1950s. Prior to mine-site remediation in the early 1980’s measured loadings of Cu, Zn, Mn and sulfate caused severe impact to fish diversity and abundanc e, including fish kills observed in the main Finniss River and its East Branch. Following mine-site remediation and measured reductions in contaminant loadings, there has been recovery of fish communities in the main Finniss River and considerable recolonisation of the still highly contaminated region of the East Branch, that was virtually devoid of fish populations prior to remediation [2]. Following mine site remediation reductions in annual-cycle contaminant loads of sulfate, Cu, Zn, and Mn by factors of 3-7 were accompanied by an unexpected degree recovery in fish community structure in the contaminated region of the Finniss River, to the extent that they were not statistically (P > 0.05) distinguishable from unexposed environments [2]. However, these fish communities continue to be exposed to considerable annual tonnages of these contaminants, as well as the naturally-occurring radionuclides associated with uranium mine wastes. Hence their capacity to accumulate contaminants under these conditions of long-term exposure and their adaptive response can be critically investigated, and is of concern to local stakeholders, both Aboriginal and European, who consume some of these fish species [ 3]. A more unexpected field observation was made in 1993 when five small fish species were found living in the East Branch of the Finniss River, where individual species penetrated the pollution gradient to varying degrees, but with one species (Melanotaenia nigrans) occurring at extremely high concentrations of Cu [4]. A laboratory-based study investigated the mechanisms of copper tolerance in M. nigrans from the polluted East Branch, compared to unexposed or reference populations. The bioconcentration of cyclotron-generated 64/67Cu in fish was used to investigate the mechanism of copper tolerance in exposed fish. In this shortterm experiment Cu concentrations in all tissue sections were significantly (P<0.05) less (up to 50%) in exposed fish compared with the respective tissue sections of reference fish, when exposed to both low and elevated Cu water concentrations. The mechanism of copper tolerance was concluded to be reduced copper uptake in the gills, rather than increased binding or elimination. Initial and subsequent allozyme electrophoresis showed that heterozygosity was reduced in exposed fish compared with that of reference fish. Collectively, these results suggest that genetic selection may have occurred in the exposed fish population. This was the first study on the mechanisms of copper tolerance in a wild fish population that has been exposed to elevated copper concentrations [5]. A pilot study of Cu, U, Zn, Co, Ni, Pb, Mn, Ra and Po-210 in several edible species of fish that now occur in abundance in the region of the main Finniss exposed to mine effluents has shown the following. Each contaminant water concentration was enhanced in the contaminated zone at the time of sampling. Compared to unexposed control sites, flesh samples from two species [Bony bream (Nematalosa erebi) and Eel- tailed catfish (Neosilurus ater)] were not significantly (P>0.05) enhanced in mean concentrations of any of these contaminants, with some being actually reduced (P<0.05) in the most contaminated region. This pattern of reduced accumulation in the exposed populations under field conditions is comparable to that obtained experimentally for Cu uptake in M. nigrans.
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    Tolerance of fish to contaminated habitats: underlying mechanisms probed with isotopic tracers
    (International Atomic Energy Agency, 2004-10-24) Jeffree, RA; Markich, SJ; Twining, JR; Gale, S
    Future scenarios indicate agricultural and industrial expansions in major river basins and enhanced world populations focusing in coastal watersheds [1], particularly in SE Asia. Such scenarios are consistent with increasing concentrations of various contaminants, including metals and radionuclides. It is important to assess the likely impacts on fisheries, their response and possible adaptability to enhanced contaminant levels and the implications for resulting transfer factors and contaminant levels in fisheries, that can be the major sources of subsistence and livelihood for coastal communities. The likely future responses of fisheries to projected increases in contaminant loadings over broad geographical scales can be probed through the employment of currently highly contaminated aquatic environments. Such a system with these attributes, that we have investigated periodically since the early 1970s, is the Finniss River in tropical northern Australia, that has continued to receive acid mine drainage from the Rum Jungle U/Cu mine since the 1950s. Prior to mine-site remediation in the early 1980’s measured loadings of Cu, Zn, Mn and sulfate caused severe impact to fish diversity and abundanc e, including fish kills observed in the main Finniss River and its East Branch. Following mine-site remediation and measured reductions in contaminant loadings, there has been recovery of fish communities in the main Finniss River and considerable recolonisation of the still highly contaminated region of the East Branch, that was virtually devoid of fish populations prior to remediation [2]. Following mine site remediation reductions in annual-cycle contaminant loads of sulfate, Cu, Zn, and Mn by factors of 3-7 were accompanied by an unexpected degree recovery in fish community structure in the contaminated region of the Finniss River, to the extent that they were not statistically (P > 0.05) distinguishable from unexposed environments [2]. However, these fish communities continue to be exposed to considerable annual tonnages of these contaminants, as well as the naturally-occurring radionuclides associated with uranium mine wastes. Hence their capacity to accumulate contaminants under these conditions of long-term exposure and their adaptive response can be critically investigated, and is of concern to local stakeholders, both Aboriginal and European, who consume some of these fish species [ 3]. A more unexpected field observation was made in 1993 when five small fish species were found living in the East Branch of the Finniss River, where individual species penetrated the pollution gradient to varying degrees, but with one species (Melanotaenia nigrans) occurring at extremely high concentrations of Cu [4]. A laboratory-based study investigated the mechanisms of copper tolerance in M. nigrans from the polluted East Branch, compared to unexposed or reference populations. The bioconcentration of cyclotron-generated 64/67Cu in fish was used to investigate the mechanism of copper tolerance in exposed fish. In this shortterm experiment Cu concentrations in all tissue sections were significantly (P<0.05) less (up to 50%) in exposed fish compared with the respective tissue sections of reference fish, when exposed to both low and elevated Cu water concentrations. The mechanism of copper tolerance was concluded to be reduced copper uptake in the gills, rather than increased binding or elimination. Initial and subsequent allozyme electrophoresis showed that heterozygosity was reduced in exposed fish compared with that of reference fish. Collectively, these results suggest that genetic selection may have occurred in the exposed fish population. This was the first study on the mechanisms of copper tolerance in a wild fish population that has been exposed to elevated copper concentrations [5]. A pilot study of Cu, U, Zn, Co, Ni, Pb, Mn, Ra and Po-210 in several edible species of fish that now occur in abundance in the region of the main Finniss exposed to mine effluents has shown the following. Each contaminant water concentration was enhanced in the contaminated zone at the time of sampling. Compared to unexposed control sites, flesh samples from two species [Bony bream (Nematalosa erebi) and Eel- tailed catfish (Neosilurus ater)] were not significantly (P>0.05) enhanced in mean concentrations of any of these contaminants, with some being actually reduced (P<0.05) in the most contaminated region. This pattern of reduced accumulation in the exposed populations under field conditions is comparable to that obtained experimentally for Cu uptake in M. nigrans.