Browsing by Author "Adams, MS"

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    Dietary ingestion of fine sediments and microalgae represent the dominant route of exposure and metal accumulation for Sydney rock oyster (Saccostrea glomerata): a biokinetic model for zinc
    (Elsevier, 2015-08-01) Lee, JH; Birch, GF; Cresswell, T; Johansen, MP; Adams, MS; Simpson, SL
    Past studies disagree on the extent to which dissolved or dietary uptake contribute to metal bioaccumulation in the filter-feeding Sydney rock oyster (Saccostrea glomerata) in urbanized estuaries. Although most data support the assumption that fine sediments are a major route of metal uptake in these bivalves, some studies based in the Sydney estuary, Australia, have indicated a poor correlation. In the present study, seawater, sediment and microalgae were radiolabelled with 65Zn tracer and exposed to S. glomerata to assess the influence of dissolved and dietary sources to Zn bioaccumulation. Oysters in the dissolved-phase uptake experiment (5, 25 and 50 μg L−1 65Zn for 4 d followed by 21 days of depuration) readily accumulated 65Zn for all three concentrations with an uptake rate constant of 0.160 ± 0.006 L dry weight g−1 d−1. Oysters in the dietary assimilation experiment (1 h pulse-feed of either 65Zn-radiolabelled suspended fine-fraction (<63 μm) sediment or the microalgae Tetraselmis sp.) accumulated 65Zn, with assimilation efficiencies of 59 and 67% for fine sediment and microalgae, respectively. The efflux rates were low for the three experiments (0.1–0.5% d−1). A bioaccumulation kinetic model predicts that uptake of Zn will occur predominantly through the dietary ingestion of contaminated fine sediment particles and microalgae within the water column, with considerably greater metal bioaccumulation predicted if oysters ingested microalgae preferentially to sediments. However, the model predicts that for dissolved Zn concentrations greater than 40 μg L−1, as observed during precipitation events, the uptake of the dissolved phase may contribute ≥50% to accumulation. Overall, the results of the present study suggest that all three sources may be important exposure routes to S. glomerata under different environmental conditions, but contributions from dietary exposure will often dominate. © 2015 Elsevier
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    Uptake and accumulation of cadmium, manganese and zinc by fisheries species: trophic differences in sensitivity to environmental metal accumulation
    (Elsevier, 2019-11-10) O'Mara, K; Adams, MS; Burford, MA; Fry, B; Cresswell, T
    Fishery targeted species living in estuaries face multiple anthropogenic pressures including habitat contamination. However, trace metal concentrations in aquatic organisms can be highly variable, making it difficult to interpret accumulation responses. Understanding sources for metal accumulation in these organisms and their biokinetics is important for management of local fisheries and ensuring safety and quality of consumed seafood, particularly in urbanised areas. In this study, we exposed Australian sand clams, school prawns and sand whiting to a combination of cadmium (Cd), manganese (Mn) and zinc (Zn) radioisotopes 1) dissolved in seawater, 2) adsorbed to suspended sediment particles and 3) in radiolabelled food. Sand clams were sensitive to Cd, Mn and Zn uptake and accumulation from all sources because of their filter feeding physiology. Mean Cd and Zn assimilation efficiencies (AE) were higher in clams fed benthic diatoms (51, 43, 63% for Cd, Mn and Zn, respectively) than clams fed an algal flagellate species (22, 32, 33% for Cd, Mn and Zn, respectively). Metal uptake by prawns from seawater was low, whereas assimilation from diet was high (67, 59, 64% mean AEs from Cd, Mn and Zn, respectively). Sand whiting did not accumulate metals from seawater, even after concentrations were increased. Assimilation from diet (labelled prawns) was also low for sand whiting, particularly for Cd and Zn (11, 26, 14% mean AEs from Cd, Mn and Zn, respectively). These results may help explain the persistence of sand whiting in contaminated estuaries. Suspended sediment exposures showed that prawns and fish are less likely than clams to be negatively affected by disturbance events such as floods, which can bring metals into estuaries. The findings of this study have implications for fisheries management, both for protection and remediation of important habitats, and to ensure safe standards for seafood consumption by humans. © 2019 Elsevier B.V