Fitness of Isidorella newcombi Following Multi-generational Cu Exposures: Mortality, Cellular Biomarkers and Life History Responses.

The effects of multigenerational Cu exposure on the freshwater gastropod Isidorella newcombi were investigated. Snails were exposed to a range of treatment-specific Cu concentrations in the parental to F2 generations, and a common Cu concentration in the F3 generation. In the parental to F2 generations, some general responses to 3 days Cu exposures included reduced survival and feeding in snails exposed to higher Cu concentrations. This suggested that the snails exposed to the high Cu concentration were experiencing Cu-induced stress that may apply selection pressure. In the F3 generation, when all treatments were exposed to a common Cu concentration, increased survival was correlated with the pre-exposure Cu concentration history. Snails that had been pre-exposed to Cu also displayed reduced stress at a sub-lethal level, indicated by lower lysosomal destabilisation (LD). Mortality and LD responses in the F3 generation were not related to Cu tissue concentrations, indicating increased tolerance and reduced stress were not related to changes in Cu bioaccumulation. Total antioxidant capacity increased in the higher Cu concentration pre-exposure treatments which could be associated with lower Cu-induced stress, however, this is not supported by the oxidative damage marker lipid peroxidation, which also increased. While Cu tissue concentrations and oxidative stress markers were assessed to determine underlying reasons for increased tolerance in snails from a population with a multi-generational exposure history to Cu, the results were not conclusive. Despite this, it was demonstrated through increased survival and reduced LD that Cu tolerance can develop over a short evolutionary time scale.

The Response of the Planorbid Snail Isidorella newcombi to Chronic Copper Exposure Over a 28-Day Period: Linking Mortality, Cellular Biomarkers, and Reproductive Responses.

The native freshwater gastropod Isidorella newcombi attacks the roots of developing rice plants in southern Australia and is controlled using copper sulphate. The apparent tolerance of this species to moderate levels of copper (Cu) exposure led us to investigate its potential usefulness as a biomonitor species. To assess its response to chronic Cu exposure, adult I. newcombi were exposed to 0-120 µg L-1 of Cu for 28 days. Lethal and sublethal responses were investigated. The relationships between subcellular biomarkers and life history traits also were explored. At exposure concentrations of 60 µg L-1 Cu and above, 100% mortality was observed during the 28-day exposure period. In these treatments, there was an exposure concentration dependent decrease in the time that the snails survived. In the surviving snails, there was an exposure concentration-dependent increase in tissue Cu concentration. In the snails exposed to Cu concentrations above 15 µg L-1, no eggs were produced during the final week of copper exposure, indicating that populations would not persist at Cu concentrations above 15 µg L-1. The general stress biomarker lysosomal membrane destabilisation (LD) indicated organisms exposed to 10 µg L-1 Cu and above were experiencing Cu induced stress. This suggests that LD could act as an early warning system for responses at higher levels of biological organisation in I. newcombi exposed to copper.

Factors influencing arsenic concentrations and species in mangrove surface sediments from south-east NSW, Australia.

Arsenic concentrations and speciation of 55 mangrove surface sediment samples from the south-eastern coast of NSW, Australia, have been measured. Arsenic concentrations were in the range 1.6-8.6 µg/g dry mass. All arsenic concentration values were well below 20 µg/g, the ANZEC/ARMCANZ interim sediment quality guideline-low trigger value. The bulk sediment pH was 6.0-7.3 and Eh -80 to -260 mV. The sediments contained variable silt-clay (2-30 % w/w), iron (668-12721 µg/g), manganese (1-115 µg/g), sulphur (70-18400 µg/g) and carbon (5-90 mg/g) concentrations. Arsenic concentrations correlated with silt and clay content, iron and manganese concentrations, indicating silt-clay particles covered and coated with iron and manganese (oxy) hydroxides scavenged arsenic. Arsenic extracted with 0.5 M phosphoric acid (68-95 %) was present only as inorganic arsenic (55-91 %), indicating that other arsenic species such as arsenobetaine derived from marine animal tissues rapidly degrade in sediments. The unextractable arsenic was correlated with increases in organic carbon, iron and manganese content. In conclusion, the cycling of arsenic in mangrove sediments is essentially the cycling of inorganic arsenic and primarily controlled by the redox cycling of carbon, sulphur, iron and manganese.

The use of the marine gastropod, Cellana tramoserica, as a biomonitor of metal contamination in near shore environments.

The use of the marine gastropod, Cellana tramoserica, as a biomonitor of metal exposure was investigated. The factors influencing metal concentrations, such as mass, gender, substrate, shoreline position and temporal variation were examined. Tissue metal concentrations were mostly found to be independent of mass and gender. When metal concentrations were significantly correlated with mass, correlations were low and explained little variability. The underlying substrate and position in the littoral zone had only a small influence on metal concentrations. Variation between individuals, inherent variability due to genetic variability, was the most significant contribution to the overall variation in metal concentrations, resulting in positive skewing of population distributions. The mean metal concentrations varied temporally; metal masses were relatively constant with fluctuations in metal concentrations related to fluctuations in metal body burdens. The populations from a metal-contaminated site had significantly higher tissue Cu, Zn, As and Pb concentrations than the populations from relatively uncontaminated locations. C. tramoserica therefore can be considered to be a net accumulator of metals. A sample number of >10 is required to detect changes of 25 % from the mean concentrations at uncontaminated locations. This species meets the requirements of a suitable biomonitor for metal contaminants in the environment i.e. hardy, sessile, widespread, sufficient tissue mass and a metal accumulator. As the measurement of metal concentrations in C. tramesoria were influenced by substrate and shore position and, sometimes, mass, sites with similar substrates and organisms of similar mass and shoreline position should be chosen for comparison. When comparing metal concentrations in gastropods from different locations, they should be collected over the same period to minimise variability due to mass differences, spawning and other seasonal/temporal effects.