Browsing by Author "Nugegoda, D"

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    Bioaccumulation and retention kinetics of cadmium in the freshwater decapod Macrobrachium australiense
    (Elsevier, 2014-03) Cresswell, T; Simpson, SL; Smith, REW; Nugegoda, D; Mazumder, D; Twining, JR
    The potential sources and mechanisms of cadmium bioaccumulation by the native freshwater decapods Macrobrachium species in the waters of the highly turbid Strickland River in Papua New Guinea were examined using 109Cd-labelled water and food sources and the Australian species Macrobrachium australiense as a surrogate. Synthetic river water was spiked with environmentally relevant concentrations of cadmium and animals were exposed for 7 days with daily renewal of test solutions. Dietary assimilation of cadmium was assessed through pulse-chase experiments where prawns were fed separately 109Cd-labelled fine sediment, filamentous algae and carrion (represented by cephalothorax tissue of water-exposed prawns). M. australiense readily accumulated cadmium from the dissolved phase and the uptake rate increased linearly with increasing exposure concentration. A cadmium uptake rate constant of 0.10 ± 0.05 L/g/d was determined in synthetic river water. During depuration following exposure to dissolved cadmium, efflux rates were low (0.9 ± 5%/d) and were not dependent on exposure concentration. Assimilation efficiencies of dietary sources were comparable for sediment and algae (48–51%), but lower for carrion (28 ± 5%) and efflux rates were low (0.2–2.6%/d) demonstrating that cadmium was well retained by M. australiense. A biokinetic model of cadmium accumulation by M. australiense predicted that for exposures to environmentally relevant cadmium concentrations in the Strickland River, uptake from ingestion of fine sediment and carrion would be the predominant sources of cadmium to the organism. The model predicted the total dietary route would represent 70–80% of bioaccumulated cadmium © 2014, Elsevier B.V.
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    Challenges with tracing the fate and speciation of mine-derived metals in turbid river systems: implications for bioavailability
    (Springer, 2013-11-01) Cresswell, T; Smith, REW; Nugegoda, D; Simpson, SL
    The fast-flowing and highly turbid Lagaip River (0.5-10 g/L suspended solids) in the central highlands of Papua New Guinea receives mine-derived metal inputs in both dissolved and particulate forms. Nearest the mine, metal concentrations in suspended solids were 360, 9, 90, 740 and 1,300 mg/kg for As, Cd, Cu, Pb and Zn, while dissolved concentrations were 2.7, 0.6, 3.1, 0.1 and 25 mu g/L, respectively. This creates a significant metal exposure source for organisms nearer the mine. However, because the Lagaip River is diluted by a large number of tributaries, the extent to which mine-derived metals may affect biota in the lower catchments is uncertain. To improve our understanding of the forms of potentially bioavailable metals entering the lower river system, we studied the partitioning and speciation of metals within the Lagaip River system. Dissolved and particulate metal concentrations decreased rapidly downstream of the mine due to dilution from tributaries. As a portion of the particulate metal concentrations, the more labile dilute acid-extractable forms typically comprised 10-30 % for As and Pb, 50-75 % for Cu and Zn, and 50-100 % for Cd. Only dissolved Cd, Cu and Zn remained elevated relative to the non-mine-impacted tributaries (< 0.03, 0.5 and 0.3 mu g/L), but the concentrations did not appreciably change with increasing dilution downriver. This indicated that release of Cd, Cu and Zn was likely occurring from the more labile metal phases of the mine-derived particulates. Chelex-labile metal analyses and speciation modelling indicated that dissolved copper and lead were largely non-labile and likely complexed by naturally occurring organic ligands, while dissolved cadmium and zinc were predominantly present in labile forms. The study confirmed that mine-derived particulates may represent a significant source of dissolved metals in the lower river system; however, comparison with water quality guidelines indicates the low concentrations would not adversely affect aquatic life.© 2013, Springer
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    Comparing trace metal bioaccumulation characteristics of three freshwater decapods of the genus Macrobrachium
    (Elsevier, 2014-07-01) Cresswell, T; Smith, REW; Nugegoda, D; Simpson, SL
    Potential sources and kinetics of metal bioaccumulation by the three Macrobrachium prawn species M. australiense, M. rosenbergii and M. latidactylus were assessed in laboratory experiments. The prawns were exposed to two scenarios: cadmium in water only; and exposure to metal-rich mine tailings in the same water. The cadmium accumulation from the dissolved exposure during 7 days, followed by depuration in cadmium-free water for 7 days, was compared with predictions from a biokinetic model that had previously been developed for M. australiense. M. australiense and M. latidactylus accumulated significant tissue cadmium during the exposure phase, albeit with different uptake rates. All three species retained >95% of the bioaccumulated cadmium during the depuration phase, indicating very slow efflux rates. Following exposure to tailings, there were significant (p < 0.05) differences in tissue arsenic, cadmium, lead and zinc concentrations among species. Cadmium and zinc concentrations were increased relative to controls for all three species but were not different between treatments (direct/indirect contact with tailings), suggesting these metals were primarily accumulated via the dissolved phase. All species bioaccumulated significantly greater arsenic and lead when in direct contact with mine tailings, demonstrating the importance of an ingestion pathway for these metals. Copper was not bioaccumulated above control concentrations for any species. The differences between the metal accumulation of the three prawns indicated that a biokinetic model of cadmium bioaccumulation for M. australiense could potentially be used to describe the metal bioaccumulation of the other two prawn species, albeit with an over-prediction of 3–9 times. Despite these being the same genus of decapod crustacean, the study highlights the issues with using surrogate species, even under controlled laboratory conditions. It is recommended that future studies using surrogate species quantify the metal bioaccumulation characteristics of each species in order to account for any differences between species.© 2014, Elsevier B.V.
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    Sources and mechanisms of cadmium bioaccumulation by the freshwater decapod crustacean Macrobrachium australiense
    (Society of Environmental Toxicology and Chemistry, 2012-05-20) Cresswell, T; Simpson, SL; Twining, JR; Mazumder, D; Smith, REW; Nugegoda, D
    Metal bioaccumulation by aquatic invertebrates in the environment can often be explained by chemical parameters such as metal concentrations within the solution and particulate phases by exposure-dose-response relationships. Simple relationships of this type are not known for invertebrates in the highly turbid Strickland River, Papua New Guinea. Here, indigenous prawns demonstrate significant differences in bioaccumulated metal concentrations (predominantly cadmium) between populations exposed to mining effluents compared to those in reference tributaries. However, metal concentrations of waters and sediments are not significantly different between sites. This study investigated the potential sources and mechanisms of cadmium (Cd) bioaccumulation by the freshwater decapod Macrobrachium australiense using 109Cd-labelled 70 SETAC 6th World Congress/SETAC Europe 22nd Annual Meeting water and food sources. Synthetic river water (SRW) was spiked with environmentally relevant concentrations of Cd and prawns were exposed for seven days with daily renewal of test solutions. Prawns were subsequently allowed to depurate in Cd-free SRW for fourteen days. Dietary assimilation of Cd was assessed through pulse-chase experiments where prawns were fed 109Cd-labelled fine sediment, filamentous algae and carrion (represented by cephalothorax tissue of water-exposed prawns). Radioanalyses during the exposures were used to determine influx and efflux rate constants for Cd in water, and the assimilation efficiency (AE) and efflux rate (Ke) of Cd from each dietary source. Results indicated that M. australiense readily uptake Cd from solution and that uptake rate increased linearly with increasing exposure concentration. During depuration, water efflux rates were low (0.9 ± 5 % d-1) and were not dependent on exposure concentration. AEs of dietary sources were comparable for sediment and algae (approx 50 %), but lower for carrion (33 %) and efflux rates were low (0.2-2.6 % d-1). The results demonstrated that prawns are likely to bioaccumulate Cd readily from both water and food sources. The rapid uptake but slow efflux of bioaccumulated Cd may explain why monthly or weekly measurements of Cd in water and sediments provide inadequate information regarding exposure or dose to explain metal accumulation patterns. A biokinetic model of Cd accumulation by M. australiense is presented based on the findings.