Heavy metals in Australian grown and imported rice and vegetables on sale in Australia: health hazard.

Dietary exposure to heavy metals is a matter of concern for human health risk through the consumption of rice, vegetables and other major foodstuffs. In the present study, we investigated concentrations of cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) in Australian grown and imported rice and vegetables on sale in Australia. The mean concentrations of Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn in Australian grown rice were 7.5 µg kg(-1), 21 µg kg(-1), 144 µg kg(-1), 2.9 mg kg(-1), 24.4 mg kg(-1), 166 µg kg(-1), 375 µg kg(-1), and 17.1 mg kg(-1) dry weight (d. wt.), respectively. Except Cd, heavy metal concentrations in Australian grown rice were higher than Bangladeshi rice on sale in Australia. However, the concentrations of Cd, Cr, Cu, and Ni in Indian rice on sale in Australia were higher than Australian grown rice. The concentrations of Cu and Ni in Vietnamese rice, and that of Cd, Cr, Cu, Ni, and Pb in Thai rice on sale in Australia were also higher than Australian grown rice. Heavy metal concentrations in Pakistani rice on sale in Australia were substantially lower than that in Australian grown rice. In Australian grown rice varieties, the concentrations of heavy metals were considerably higher in brown rice varieties than white rice varieties, indicating Australian brown rice as a potential source of dietary heavy metals for Australian consumers. The mean concentrations of heavy metals in Australian grown and Bangladeshi vegetables on sale in Australia were also determined. Some of the Australian grown and Bangladeshi vegetables contained heavy metals higher than Australian standard maximum limits indicating them as potential sources of dietary heavy metals for Australian consumers. Further investigation is required to estimate health risks of heavy metals from rice and vegetables consumption for Australian consumers.

Toxicity of arsenic species to three freshwater organisms and biotransformation of inorganic arsenic by freshwater phytoplankton (Chlorella sp. CE-35).

In the environment, arsenic (As) exists in a number of chemical species, and arsenite (As(III)) and arsenate (As(V)) dominate in freshwater systems. Toxicity of As species to aquatic organisms is complicated by their interaction with chemicals in water such as phosphate that can influence the bioavailability and uptake of As(V). In the present study, the toxicities of As(III), As(V) and dimethylarsinic acid (DMA) to three freshwater organisms representing three phylogenetic groups: a phytoplankton (Chlorella sp. strain CE-35), a floating macrophyte (Lemna disperma) and a cladoceran grazer (Ceriodaphnia cf. dubia), were determined using acute and growth inhibition bioassays (EC50) at a range of total phosphate (TP) concentrations in OECD medium. The EC50 values of As(III), As(V) and DMA were 27 ± 10, 1.15 ± 0.04 and 19 ± 3 mg L(-1) for Chlorella sp. CE-35; 0.57 ± 0.16, 2.3 ± 0.2 and 56 ± 15 mg L(-1) for L. disperma, and 1.58 ± 0.05, 1.72 ± 0.01 and 5.9 ± 0.1 mg L(-1) for C. cf. dubia, respectively. The results showed that As(III) was more toxic than As(V) to L. disperma; however, As(V) was more toxic than As(III) to Chlorella sp. CE-35. The toxicities of As(III) and As(V) to C. cf. dubia were statistically similar (p>0.05). DMA was less toxic than iAs species to L. disperma and C. cf. dubia, but more toxic than As(III) to Chlorella sp. CE-35. The toxicity of As(V) to Chlorella sp. CE-35 and L. disperma decreased with increasing TP concentrations in the growth medium. Phosphate concentrations did not influence the toxicity of As(III) to either organism. Chlorella sp. CE-35 showed the ability to reduce As(V) to As(III), indicating a substantial influence of phytoplankton on As biogeochemistry in freshwater aquatic systems.

Leaf litter breakdown along an elevational gradient in Australian alpine streams.

The breakdown of allochthonous organic matter, is a central step in nutrient cycling in stream ecosystems. There is concern that increased temperatures from climate change will alter the breakdown rate of organic matter, with important consequences for the ecosystem functioning of alpine streams. This study investigated the rate of leaf litter breakdown and how temperature and other factors such as microbial and invertebrate activities influenced this over elevational and temporal gradients. Dried leaves of Snow Gum (Eucalyptus pauciflora) and cotton strips were deployed in coarse (6 mm), and fine (50 µm) mesh size bags along an 820 m elevation gradient. Loss of mass in leaf litter and cotton tensile strength per day (k per day), fungal biomass measured as ergosterol concentration, invertebrate colonization of leaf litter, and benthic organic matter (mass and composition) were determined. Both microbial and macroinvertebrate activities were equally important in leaf litter breakdown with the abundance of shredder invertebrate taxa. The overall leaf litter breakdown rate and loss of tensile strength in cotton strips (both k per day) were greater during warmer deployment periods and at lower elevations, with significant positive relationships between mean water temperature and leaf breakdown and loss of tensile strength rate, but no differences between sites, after accounting for the effects of temperature. Despite considerably lower amounts of benthic organic matter in streams above the tree line relative to those below, shredders were present in coarse mesh bags at all sites. Ergosterol concentration was greater on leaves in coarse mesh bags than in fine mesh bags, implying differences in the microbial communities. The importance of water temperatures on the rate of leaf litter breakdown suggests the potential effects of climate change-induced temperature increases on ecological processes in such streams.

Benthic macroinvertebrate assemblages in remediated wetlands around Sydney, Australia.

To investigate potential high organisational level impacts of persistent organic pollution in the wetlands in the Sydney Olympic Park (SOP) remediated site, the benthic macroinvertebrate assemblages of seven wetlands within SOP and two off-site reference wetlands were examined. Sediment cores were collected, stained and preserved from each study site and the macroinvertebrates identified to the appropriate taxonomic level (Class, Order, Family, Subfamily). Data were analysed for taxon richness and macroinvertebrate abundance and multivariate techniques were used to identify chemical/physical characteristics of the sediment, which were important influences on the differences in the assemblage between study sites. Macroinvertebrate abundance was highly variable between study sites and taxon richness was low across all sites. Oligochaetes, nematodes, ostracods and chironomids were the most common taxa found and were the most important in influencing differences between the macroinvertebrate assemblages among the study sites. Sediment grain size and chemical characteristics of the sediments (ΣPAH, ΣPCB, TCDDeq and heavy metal concentrations) were important in separating the study sites based on taxon richness and abundance. Canonical correspondence analysis separated the macroinvertebrate assemblages at newly two created wetlands from those at other study sites including the urban reference sites. Increased sediment POP contamination (particularly as measured TCDDeq and ΣDDT concentrations) is a likely contributor in excluding pollution sensitive taxa and, therefore, alterations to benthic macroinvertebrate assemblages. Further, the influence of TOC suggests the significance of catchment inputs in contributing to changes in macroinvertebrate assemblage. The SOP remediation led to the establishment of wetlands with benthic communities representative of those expected in urban wetlands.

Bioactivity of POPs and their effects in mosquitofish in Sydney Olympic Park, Australia.

The site of the 2000 Olympic Games (Sydney Olympic Park (SOP), Sydney, Australia) was contaminated by persistent organic pollutants (POPs) prior to remediation in the 1990s. This study investigates the bioactivity of POPs in the sediment and water of wetlands across SOP by in vitro 2,3,7,8-TCDD equivalence (TCDDeq) measurement (H4IIE cell line bioassay). Further, it examines whether disturbance of these sediments is likely to mobilise ligands for this receptor into the water column. Exposure to aryl hydrocarbon receptor (AhR) ligands was measured in vivo using hepatic cytochrome P4501A (CYP1A) induction (EROD) in the mosquitofish (Gambusia holbrooki). Aqueous TCDDeq ranged from 0.013 to 0.057 pM in SOP wetlands which was significantly (p<0.05) less that in urban reference sites. These concentrations were not correlated to physical or chemical characteristics of the wetlands. In the sediments, TCDDeq ranged from 0.0016 to 7.06 microg/kg and these were not significantly (p>or=0.05) different to that measured in urban reference sites. Simulated disturbance of small quantities of sediment in water samples significantly (p<0.05) increased the levels of TCDDeq measured in the water. Sediment TCDDeq was correlated to sediment SigmaPAH concentration in 2006 and sediment SigmaPCB, SigmaDDT concentrations and fine sediment grain size in 2005. While fish at one SOP wetland had hepatic EROD activity elevated above the estimated basal level for this species, these were at the lower end of the range measured in urban impacted, non-remediated wetlands. EROD activity was positively correlated with both the sediment SigmaPCB load and aqueous TCDDeq. Increased catchment size was correlated with increased EROD activity suggesting an even spread of POPs throughout the residential areas of the Sydney metropolitan area. The concentration of bioactive POPs in the wetlands of SOP is therefore low relative to urban reference sites demonstrating the ongoing success of the remediation program.

Effects of temperature on ventilatory behavior of fish exposed to sublethal concentrations of endosulfan and chlorpyrifos.

The ventilation amplitude and frequency of silver perch Bidyanus bidyanus, and the ventilation frequency of rainbow fish Melanotaenia duboulayi and rainbow trout Oncorhynchus mykiss, were determined at different temperatures upon exposure to endosulfan and chlorpyrifos, respectively. Silver perch and rainbow fish were tested at 15, 20, 25, 30, and 35 degrees C, while rainbow trout was tested at 10, 15, 20, and 25 degrees C. Although some trend of increasing amplitudes with increasing temperature was evident; there was no significant temperature response of ventilation frequency rates over time in silver perch pre-exposed to 10 microg L(-1) endosulfan for 18 h. The rate of ventilation frequency of rainbow fish pre-exposed to 200 microg L(-1) of chlorpyrifos for 96 h was lower in treatments than in the control at 15 degrees C. However, between 20 and 35 degrees C, rates were significantly higher in the treatments than those of the control. In rainbow trout pre-exposed to 100 microg L(-1) of chlorpyrifos, the rates of frequency were significantly lower than those of controls in temperatures between 10 and 20 degrees C but higher at 25 degrees C. The amplitude of silver perch seemed to increase with the increase in temperature; however, the corresponding temperature quotient values at various temperature regimes and over exposure time showed no significant differences. The ventilation frequency of rainbow fish and rainbow trout significantly increased at the higher test temperatures, and their corresponding temperature quotient values for both fish also increased at the elevated temperatures.

Contamination and screening level toxicity of sediments from remediated and unremediated wetlands near Sydney, Australia.

The present study assessed contamination and toxicity of sediments from seven remediated and remnant wetland sites within Sydney Olympic Park, Australia, and four unremediated sites adjacent to its boundary using chemical analysis and a luminescent bacterial biosensor assay (Escherichia coli). Concentrations of metals (Pb, Cr, Cu, Ni, Zn, Cd, and As) and persistent organic chemicals (DDT and its metabolites, dichlorodiphenyldichloroethane and dichlorodiphenyldichloroethylene; polycyclic aromatic hydrocarbons; polychlorinated biphenyls; and polychlorinated dibenzo-p-dioxins and dibenzofurans) in sediments and their pore-water samples were determined. Zinc concentrations were the highest of the metals in the sediments (84-618 mg/kg), and at eight sites, metal concentrations in sediments exceeded the Australian ecological trigger values for Pb, Zn, and Ni. Concentrations of organic contaminants in the sediments exceeded the trigger values at all 11 sites for DDTs, at 6 sites for polycyclic aromatic hydrocarbons, and 5 sites for polychlorinated biphenyls. Sediment samples from the four unremediated sites outside the Sydney Olympic Park had dioxin concentrations greater than 200 pg (toxic equivalency per gram). The same four sites were identified as contaminated in pore-water toxicity tests with the luminescent biosensor, generally consistent with the bioavailable fractions of the contaminants (pore-water and Tenax extraction data), as well as dioxin levels, in the sediments. Preliminary toxicity identification and evaluation tests of the pore water from the four sites outside the park demonstrated that organic contaminants were the main cause of toxicity to E. coli, with no evidence that metals contributed to the toxicity of the pore water.

Distribution of inorganic and organic contaminants in sediments from Sydney Olympic Park and the surrounding Sydney metropolitan area.

Organic and inorganic contamination was assessed for sediments from wetlands and water bodies within the Sydney Olympic Park (SOP, remediated sites) and its surroundings (unremediated sites) and urban reference sites in the Sydney Basin. Among the seven elements analysed (As, Cd, Cr, Cu, Pb, Ni and Zn), Zn concentrations were the highest, followed by Pb, Cu and Cr in the sediments of SOP. Significantly higher concentrations (p < 0.05) of DDTs were found in sediments of the Homebush Bay and Parramatta River sites compared with the urban reference sites, mainly due to past manufacturing of DDT in the Homebush Bay area. However, no significant differences (p > 0.05) in concentrations were found for polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) as well as DDTs between sediments from SOP and the urban reference sites. Source indicators suggest that PAHs in the sediments originated from combustion processes. Two distinct groups of dioxin profiles were observed within SOP and its surroundings. Levels of dioxins were more than 100 pg WHO-TEQ/g dry weight of sediment at five sites adjacent to the SOP boundaries. Based on the findings of the chemical profiles of the contaminants, the remediated sites in SOP can be regarded as similar to the urban reference sites within the Sydney Basin, while the adjacent unremediated sites have higher concentrations, especially of dioxins, that could still affect organisms in the aquatic environment.

Assessing the biological relevance of exposing freshwater organisms to atrazine and molinate in environmentally realistic exposure test systems.

Assessing the toxicity of chemicals in treated laboratory water may not accurately represent the toxicity of chemicals in natural aquatic systems. In natural water, dissolved organic matter, suspended particulate matter, and sediment play key roles in the sorption of contaminants from the water. Our previously published series of papers illustrated that the presence of sediment in aquatic toxicity testing systems significantly (p < 0.05) reduced the bioavailability of the herbicides atrazine and molinate to five Australian freshwater organisms. It is not clear whether the reduced bioavailability means that the trigger values (TVs) in the current Australian and New Zealand water quality guidelines, which are calculated using toxicity data from water-only toxicity tests, provide appropriate environmental protection. Several new sets of TVs were derived in the present study and were compared to each other and to the current Australian and New Zealand TVs for atrazine and molinate. The current Australian and New Zealand TVs for atrazine and molinate provided appropriate protection to Australian freshwater species. Australian freshwater species have a sensitivity distribution similar to those of overseas species to atrazine and molinate.

Skeletal morphology and maturation of male Gambusia holbrooki exposed to sewage treatment plant effluent.

Sewage effluent has been identified as a major source of endocrine disrupting chemicals (EDCs) in the aquatic environment. The modified hemal spines (modified skeletal structures important in reproduction) of mosquitofish, Gambusia spp. have been shown to be under androgenic control and to be affected by exposure to estrogen. The current study aimed to investigate the effects of two sewage treatment plants (STPs) in Sydney, Australia on the morphology of hemal spines in populations of Gambusia holbrooki and on the ability of the fish to reach sexual maturity. The effluent from the two STPs had different effects on the hemal spines of males. At St. Marys differences in hemal spine morphology between fish upstream and downstream of the STP were not attributable to effluent from the STP. At Quakers Hill, results suggest that the effluent is generally estrogenic to G. holbrooki. There was a decrease in the proportion of males that were morphologically mature downstream of both STPs indicating potential population level effects that were associated with the presence of the STPs.

Effects of river water and salinity on the toxicity of deltamethrin to freshwater shrimp, cladoceran, and fish.

Deltamethrin is a pyrethroid insecticide used extensively to control invertebrate pests on cotton and other crops. It is acutely toxic to nontarget aquatic organisms, but existing toxicity data are mostly from toxicity tests using purified laboratory water that differs greatly from the turbid, high-conductivity rivers in the cotton-growing regions of Australia. The aim of this study was to determine whether the water quality variables conductivity, suspended particles, and dissolved organic matter alter the toxicity of deltamethrin to freshwater crustaceans and a fish. We tested three Australian native species: a cladoceran (Ceriodaphnia cf. dubia), a freshwater shrimp (Paratya australiensis), and larvae of the eastern rainbow fish (Melanotaenia duboulayi). Conductivity of the test solutions ranged from 200 to 750 microS/cm, but such changes did not modify the toxicity of deltamethrin to any of the test species. However, the toxicity of deltamethrin to C. cf. dubia and P. australiensis in river water was significantly decreased (1.8-fold to 6.3-fold reduction) compared to that in laboratory water. Variability in the toxicity data limited our ability to detect differences between laboratory and river water for M. duboulayi. Despite reductions in toxicity in natural waters, deltamethrin remained highly toxic [all L(E)C(50) values <0.26 microg/L] to all organisms tested; thus, further investigation of the hazard of deltamethrin is warranted.

Linking fish tolerance to water quality criteria for the assessment of environmental flows: A practical method for streamflow regulation and pollution control.

The survival of aquatic biota in stream ecosystems depends on both water quantity and quality, and is particularly susceptible to degraded water quality in regulated rivers. Maintenance of environmental flows (e-flows) for aquatic biota with optimum water quantity and quality is essential for sustainable ecosystem services, especially in developing regions with insufficient stream monitoring of hydrology, water quality and aquatic biota. Few e-flow methods are available that closely link aquatic biota tolerances to pollutant concentrations in a simple and practical manner. In this paper a new method was proposed to assess e-flows that aimed to satisfy the requirements of aquatic biota for both the quantity and quality of the streamflow by linking fish tolerances to water quality criteria, or the allowable concentration of pollutants. For better operation of water projects and control of pollutants discharged into streams, this paper presented two coefficients for streamflow adjustment and pollutant control. Assessment of e-flows in the Wei River, the largest tributary of the Yellow River, shows that streamflow in dry seasons failed to meet e-flow requirements. Pollutant influx exerted a large pressure on the aquatic ecosystem, with pollutant concentrations much higher than that of the fish tolerance thresholds. We found that both flow velocity and water temperature exerted great influences on the pollutant degradation rate. Flow velocity had a much greater influence on pollutant degradation than did the standard deviation of flow velocity. This study provides new methods to closely link the tolerance of aquatic biota to water quality criteria for e-flow assessment. The recommended coefficients for streamflow adjustment and pollutant control, to dynamically regulate streamflow and control pollutant discharge, are helpful for river management and ecosystems rehabilitation. The relatively low data requirement also makes the method easy to use efficiently in developing regions, and thus this study has significant implications for managing flows in polluted and regulated rivers worldwide.

The effects of three organic chemicals on the upper thermal tolerances of four freshwater fishes.

The upper temperature tolerance limits of four freshwater fish species, silver perch Bidyanus bidyanus, eastern rainbowfish Melanotaenia duboulayi, western carp gudgeon Hypseleotris klunzingeri, and rainbow trout Oncorhynchus mykiss, were determined using the critical thermal maximum (CTMaximum) method. The CTMaximum tests were carried out with unexposed fish and fish exposed to sublethal concentrations of endosulfan, chlorpyrifos, and phenol to determine whether or not the CTMaximum was affected. The CTMaximum temperature of B. bidyanus decreased by 2.8, 3.8, and 0.3 degrees C on exposure to endosulfan, chlorpyrifos, and phenol, respectively. Similarly, in M. duboulayi, the CTMaximum was decreased by 4.1, 2.5, and 0 degrees C, while in H. klunzingeri it decreased by 3.1, 4.3, and 0.1degrees C, respectively, and in O. mykiss by 4.8, 5.9, and 0.7 degrees C, respectively. Exposure to sublethal test concentrations of endosulfan and chlorpyrifos caused significant (p < or = 0.0001) reductions in CTMaximum values for all fish species compared to that of unexposed fish. However, exposure to phenol did not cause any significant (p > or = 0.05) change of CTMaximum temperatures.

Chronic effects of atrazine exposure and recovery in freshwater benthic diatoms from two communities with different pollution histories.

Diffuse agricultural runoff into rivers can result in contamination with herbicides for prolonged periods of time. Chronic exposure to herbicides has the potential to alter toxic impacts in primary producers such as benthic diatoms. Determining how individual diatom taxa respond to herbicide exposure over varied exposure durations is essential for assessing herbicide impacts. This study investigated the responses of various benthic diatom taxa and effects at the community level over 12days of atrazine exposure. Diatom communities were collected from two sites with differing exposure histories; a relatively unpolluted site (Alligator Creek) and an agricultural stream (Barratta Creek) known to be polluted by atrazine and other herbicides. Diatom community composition and the proportion of healthy cells per taxon were assessed at 0, 2, 3, 6, 9 and 12days of atrazine exposure. Pollution history altered the response of the diatom community to atrazine exposure. In the Alligator Creek diatom community there was a shift in composition towards more tolerant taxa and the loss of sensitive taxa in atrazine exposed treatments. The sensitive taxon (Gomphonema truncatum) was consistently affected by atrazine toxicity. Conversely, the polluted Barratta Creek diatom community was not strongly affected by atrazine exposure. Our study shows that during chronic atrazine exposure some taxa demonstrated the ability to recover despite initial toxicity response. Recovery could be an important trait for understanding the ecological effect of herbicide exposure on diatom species in nature and in applied circumstances such as biomonitoring indices.

The influence of reduced light intensity on the response of benthic diatoms to herbicide exposure.

Herbicide pollution events in aquatic ecosystems often coincide with increased turbidity and reduced light intensity. It is therefore important to determine whether reduced light intensity can influence herbicide toxicity, especially to primary producers such as benthic diatoms. Benthic diatoms collected from 4 rivers were exposed to herbicides in 48 h rapid toxicity tests under high light (100 µmol m(-2) s(-1) ) and low light (20 µmol m(-2) s(-1) ) intensities. The effects of 2 herbicides (atrazine and glyphosate) were assessed on 26 freshwater benthic diatom taxa. There was no significant interaction of light and herbicide effects at the community level or on the majority (22 of 26) of benthic diatom taxa. This indicates that low light levels will likely have only a minor influence on the response of benthic diatoms to herbicides. Environ Toxicol Chem 2016;35:2252-2260. © 2016 SETAC.

How benthic diatoms within natural communities respond to eight common herbicides with different modes of action.

Herbicides are common pollutants of rivers in agricultural regions. These contaminants include various types of chemicals with different modes of toxic action. Herbicides can have toxic effects on freshwater benthic diatoms, the base of the aquatic food web. We examined the effects of (non-mixture) herbicide exposure to the health of diatoms for eight common herbicides with three different modes of action; the photosystem II (PSII) inhibitors: atrazine, simazine, hexazinone, tebuthiuron and diuron; two auxinic herbicides: MCPA and 2,4-D; and the EPSP synthase inhibitor: glyphosate. Benthic diatoms within riverine communities were exposed to each herbicide in rapid toxicity tests at concentrations of 50, 200 and 500µgL(-1). The most sensitive taxa were Gomphonema spp. and Encyonema gracilis. Navicula cryptotenella was the most tolerant to herbicide exposure. There was no significant effect of the different herbicide modes of action at the community level. Herbicide mode of action did not alter which taxa were most sensitive within the community and sensitivity rankings of the dominant diatom taxa were similar for each of the eight herbicides. The consistency of the results between herbicides suggests that freshwater benthic diatoms may be suitable in situ indicators for detecting the toxicity of herbicides with differing modes of action.

The impact of variations of influent loading on the efficacy of an advanced tertiary sewage treatment plant to remove endocrine disrupting chemicals.

The impact of changes in influent load on the removal of endocrine disrupting chemicals (EDCs) by sewage treatment has not been fully characterised. This study assessed the efficacy of an advanced tertiary sewage treatment plant (STP) to remove EDCs during normal and peak flow events of sewage influent using trace chemical analysis of selected EDCs and four estrogenic in vitro bioassays. During the summer holiday season, influent volume increased by 68%, nutrient concentrations by at least 26% and hydraulic retention time was reduced by 40% compared with base flow conditions. Despite these pressures on the treatment system the concentrations and mass loading of estrone, 17ß-estradiol, estriol, Bisphenol A, 4-t-octylphenol and technical nonylphenol were not significantly higher (p>0.05) during the peak flow conditions compared with base flow conditions. Chemical analysis and in vitro bioassays showed that the efficacy of the STP in removing EDCs was not affected by the different loadings between baseline and peak flow regimes. This study demonstrates that large flow variations within the design capacity of advanced multi-stage STPs should not reduce the removal efficacy of EDCs.

Interactions between water temperature and contaminant toxicity to freshwater fish.

Warming of freshwaters as a result of climate change is expected to have complex interactions with the toxicity of contaminants to aquatic organisms. The present study evaluated the effects of temperature on the acute toxicity of endosulfan, chlorpyrifos, and phenol to 3 warm water species of fish-silver perch, rainbowfish, and western carp gudgeon-and 1 cold water species, rainbow trout. Endosulfan was more toxic to silver perch at 30 °C and 35 °C than at 15 °C, 20 °C and 25 °C during short exposures of 24 h, but at 96 h, temperature had no effect on toxicity. Toxicity to rainbow trout increased with increasing temperature, whereas warm water species exhibited maximum toxicity at around 30 °C, decreasing again toward 35 °C. Chlorpyrifos became more toxic to all species with increasing temperature. Phenol toxicity to all species decreased at low to intermediate temperatures; but as temperatures increased further toward the upper thermal limit, phenol became more toxic. Increasing toxicity in the upper thermal range of cold water species may contribute to upstream range contraction in rivers with high toxicant loads. In contrast, warm water species may not exhibit a range shift within rivers as a result of interactions between temperature and toxicity. Catchment management to offset global warming at local scales may present opportunities to mitigate increased toxicity of contaminants to fish.

Insights into the mechanisms of copper tolerance of a population of black-banded rainbowfish (Melanotaenia nigrans) (Richardson) exposed to mine leachate, using 64/67Cu.

This study investigates the mechanisms of copper tolerance of a population of black-banded rainbowfish (Melanotaenia nigrans) (Richardson). The population has been exposed to elevated copper concentrations for over 40 years, due to leachate from the Rum Jungle uranium/copper mine. At the time of collection the 96 h EC(50) of exposed [E] fish was 8.3 times higher than that of reference [R] fish. The bioconcentration of 64/67Cu in fish was used to investigate the mechanism of copper tolerance in E fish. Both E and R fish were exposed to low (L(Cu), 30 microg Cu l(-1)) and elevated (E(Cu), 300 microg Cu l(-1)) copper concentrations for 24 and 48 h, respectively. Radioactivity was measured at seven or eight time points in four tissue sections: head (including gills, heart and brain), internal organs (including gastrointestinal tract, liver, kidneys and gonads), muscle and whole body. One-compartment bioconcentration models were fit to data and compared using an F-test. Copper concentrations in all tissue sections were significantly (P<0.05) less (up to 50%) in E fish compared with the respective tissue sections of R fish when exposed to both L(Cu) and E(Cu). The exception was copper accumulation in the internal organs, which was not significantly different between E and R fish exposed to E(Cu). The mechanism of copper tolerance was concluded to be reduced copper uptake in the gills, rather than increased binding or elimination. Allozyme electrophoresis was performed to determine if genetic selection had occurred in the E fish population. Allozyme frequencies at the AAT-1 and GPI-1 loci were significantly (P<0.05) different between E and R fish. Heterozygosity was reduced in E fish compared with that of R fish. Collectively these results suggest that genetic selection may have occurred in the E fish population. Consequently, the selection of allozymes less sensitive to copper may be another mechanism of copper tolerance of E fish. This is the first study on the mechanisms of copper tolerance in a wild fish population that has been exposed to elevated copper concentrations. These findings aid the understanding of metal tolerance in fish and emphasise the importance of sample selection and its implication for toxicity testing.

The effect of 17beta-estradiol on the gonopodial development and sexual activity of Gambusia holbrooki.

Many chemicals have recently been demonstrated to possess estrogenic activity and may potentially interfere with normal sexual development. In the present study, we quantified the effects of waterborne exposure to 17beta-estradiol on the gonopodial development and sexual activity of male eastern mosquitofish (Gambusia holbrooki). Juvenile males were exposed during the period of sexual maturation to nominal concentrations of 20, 100, and 500 ng/L of 17beta-estradiol and a solvent control (0.00003% w/v ethanol) for 84 d under continuous-flow conditions. Following exposure, significant differences were found among the test treatments with respect to gonopodial length and degree of gonopodial elongation of the fish. Sexual activity, measured as the number of approaches and copulatory attempts made by the exposed males to nonexposed females, also significantly decreased with increasing concentrations of 17beta-estradiol. Because the degree of gonopodial maturation and frequency of sexual activity are important characteristics for the reproductive success of male mosquitofish, it is suggested that these traits provide sensitive and ecologically relevant endpoints for assessing estrogenic activity under both laboratory--and field-exposure conditions.