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Zn Accumulation (zn + accumulation)
Selected AbstractsSubcellular distribution of zinc in Daphnia magna and implication for toxicityENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2010Wen-Xiong Wang Abstract We examined the subcellular partitioning of zinc (Zn) in Daphnia magna both under acute and chronic exposures. In the acute Zn toxicity tests, the daphnids were exposed to different Zn concentrations for 48,h or to one lethal concentration (1,000,µg/L) for different durations (time to death for up to 47,h). Significant mortality of daphnids was observed when the newly accumulated Zn concentration reached a threshold level of approximately 40,µg/g wet weight (or 320,µg/g dry wt), approximately 3.5 times higher than the background tissue concentration (92,µg/g dry wt). Chronic exposure (14 d) to Zn resulted in nonobservable effect on survivorship and growth at newly accumulated tissue concentration of over 40,µg/g wet weight. With increasing Zn acute exposure, more Zn was partitioned into the cellular debris fraction, indicating that this fraction was presumably the first targeted site of binding for Zn upon entering the animals. The importance of other subcellular fractions either decreased accordingly or remained comparable. We found that the metal-sensitive fraction (Zn distribution in the organelles and heat-denatured proteins) did not predict the acute Zn toxicity in Daphnia. During chronic exposure, however, no major change of the subcellular partitioning of Zn with increasing Zn exposure was documented. Zinc was mainly found in the organelles and heat-stable protein fractions during chronic exposure, suggesting that any subcellular repartitioning occurred primarily during acute exposure. Metallothioneins were induced upon chronic Zn exposure, but its induction evidently lagged behind the Zn accumulation. Our present study showed that the subcellular fractionation approach could not be readily used to predict the acute and chronic toxicities of Zn in Daphnia. A tissue-based Zn accumulation approach with a threshold Zn tissue concentration was better in predicting acute Zn toxicity. Environ. Toxicol. Chem. 2010; 29:1841,1848. © 2010 SETAC [source] Kinetic uptake of bioavailable cadmium, selenium, and zinc by Daphnia magnaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2002Ri-Qing Yu Abstract Kinetic uptake of Cd, Se(IV), and Zn by Daphnia magna from the dissolved phase was determined using radiotracer techniques in moderately hard water. The metal influx rate and distribution in the soft tissue and the exoskeleton of the daphnids as influenced by metal concentration, inorganic ligands including pH, Ca2+ and SO42,, and body size were quantified. When the metal concentrations were <180 nM for Cd and <769 nM for Zn, the concentration factor in daphnids increased linearly within the 12 h of exposure. At a higher concentration, apparent steady state was reached after 3 h of exposure. Cadmium and Zn distribution in the soft tissues was not affected by the total ambient concentrations, whereas Se distribution in the soft tissue decreased by 7 to 10% with increasing Se concentration from 16 to 643 nM. A linear positive power relationship was found between the influx rates of the metals and the ambient concentrations. The concentration factor for Se, however, decreased significantly with increasing Se concentration in water. The influx rate of metals was inversely related to the body size in a power function. When the pH in ambient water increased from 5.0 to 7.0, the influx rate of Cd, Se, and Zn increased by 2.9, 16.6, and 4.1 times, respectively. The influx rates of Cd, Se, and Zn decreased by 6.9, 8.7, and 4.4 times, respectively, with an increase in Ca2+ concentration from 0.6 to 5.1 mM. In contrast, the uptake rates of all three metals were not significantly affected by the SO42, concentration. The majority of accumulated Se was distributed in the soft tissues after 12 h of exposure, whereas Cd and Zn were about evenly distributed in the soft tissue and exoskeleton. Any changes in pH, Ca2+, and SO42, concentrations did not apparently affect their distributions in the daphnids. Our study provides important kinetic data necessary for delineating the exposure routes and for further development of the biotic ligand model in Daphnia. Using a bioenergetic-based kinetic model, we showed that the dissolved uptake is dominant for Zn accumulation (>50%). For Cd and Se, dietary exposure is dominant when the bioconcentration factors of these metals in phytoplankton are at the high end. [source] Reaction norms of life history traits in response to zinc in Thlaspi caerulescens from metalliferous and nonmetalliferous sitesNEW PHYTOLOGIST, Issue 1 2007Caroline Dechamps Summary ,,We examined phenotypic plasticity of fitness components in response to zinc (Zn) in the Zn hyperaccumulator, Thlaspi caerulescens. ,,Two populations from Zn-enriched soils (M) and two populations from normal soils (NM) were grown in pots at three Zn concentrations (0, 1000 and 8000 mg kg,1 Zn), for an entire life cycle. Growth, Zn accumulation and fitness components were assessed. ,,Based on vegetative growth, M and NM populations had similar Zn tolerance at 1000 mg kg,1 Zn. However, reproductive output was markedly decreased in NM at 1000 and 8000 mg kg,1 Zn. In M populations, Zn did not affect fitness. However, low Zn status enhanced reproductive output in year 1 compared with year 2 and decreased survival after the first flowering season. ,,M populations are able to achieve equal fitness across a broad range of Zn concentrations in soil by different combinations of fecundity and longevity. No cost of higher tolerance was demonstrated in M populations. Reproductive traits appeared to be a more sensitive indicator of tolerance than vegetative growth. [source] Within and between population genetic variation for zinc accumulation in Arabidopsis halleriNEW PHYTOLOGIST, Issue 1 2002Mark R. Macnair Summary ,,Hyperaccumulator plants in the field show significant variation in the metal concentration in their aerial parts, but little is known of the causes of this variation. This paper investigates the role of soil zinc (Zn) concentration and genetic variation in causing between and within population variation in Zn accumulation in Arabidopsis halleri. ,,Seed from 17 populations of A. halleri collected in central Europe were grown under standard conditions at three external Zn concentrations and tested for Zn concentration in the leaves. ,,Between population variation was highest at low external zinc concentrations. At 10 µm Zn some plants had very low leaf Zn concentrations, and were indistinguishable from nonaccumulators. However, at higher Zn concentrations, all plants showed hyperaccumulation. There were no differences in the accumulating abilities of populations from sites with different degrees of contamination. ,,Heritability of accumulation, determined for individual families from three populations, was quite high (25,50%), indicating that selection for increased accumulating ability should be possible, although selection would be easier at low external Zn concentrations. The Zn concentration of field collected plants was affected partly by plant genotype but not by the total soil Zn around their roots. [source] Vegetation Response to Lime and Manure Compost Amendments on Acid Lead/Zinc Mine Tailings: A Greenhouse StudyRESTORATION ECOLOGY, Issue 3 2000Z. H. Ye Abstract Land disturbed by mining in China is a serious problem and lead/zinc (Pb/Zn) mine tailings constitute the majority of the metal mine tailings produced in Guangdaong Province, China. A greenhouse study was therefore conducted to evaluate the effects of lime (40, 80, 120, and 160 t/ha) and manure compost (50 and 100 t/ha) amendment on the revegetation of the Pb/Zn mine tailings using Cynodon dactylon (Bermuda grass) and Agropyron elongatum (tall wheatgrass). The results showed that a combination of lime and manure compost amendment together with deionized water leachating was able to increase pH, reduce electrical conductivity and diethylenetraminepentaacetic acid (DTPA)-extractable concentrations of Zn and Pb in tailings. Using 80 t/ha lime amendment with the supplement of fertilizer or manure compost was able to effectively improve germination of both C. dactylon and A. elongatum. The highest dry weight yields were obtained in tailings receiving 80 t lime/ha and 100 t manure compost/ha for both plant species. Plant tissue analysis showed that lime amendment at 120,160 t/ha reduced Zn accumulation in both shoot and root of C. dactylon. However, this trend was not observed for Pb. [source] Field contamination of the starfish Asterias rubens by metals.ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2003Part 1: Short-, long-term accumulation along a pollution gradient Abstract The accumulation of Cd, Pb, Zn, and Cu in the starfish Asterias rubens was studied in a Norwegian fjord characterized by a gradient of metal pollution in the sediments, ranging from very high metal concentrations at its head to much lower levels at its opening. The concentrations of metals in starfish from natural populations along the gradient (long-term accumulation) and in starfish that were transferred up the gradient (short-term accumulation) were compared. At long-term, Cd and Pb accumulations by starfish living at normal salinity (30,) were related to the level of contamination of of the environment while Cu and, to a lesser extent, Zn accumulations appeared strictly controlled. At short-term, Pb was accumulated steadily, Cd and Zn were accumulated transiently in the pyloric caeca (fast compartment), and Cu was not accumulated at all. Depuration experiments (transfer down the gradient) showed that Cd and Pb were efficiently eliminated from the pyloric caeca but not from the body wall (slow compartment). It is concluded that Pb is chronically accumulated, without apparent control, Cd is subjected to a regulating mechanism in the pyloric caeca which is overwhelmed over the long-term; Zn is tightly controlled in the pyloric caeca and Cu in both pyloric caeca and body wall. A distinct color variety of starfish is restricted to the low salinity (22-26,) superficial water layer. This variety showed a different pattern of metal accumulation over the long-term. This pattern is attributed to the particular hydrological conditions prevailing in this upper layer. [source] | ||||||||||