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ABSTRACT: In this study, the aqueous uptake and dietary assimilation (trophic transfer) of two endocrine disrupting compounds (dioxin and phathalic acid) in the green mussel Perna viridis were quantified. During short-term exposure period, dioxin rapidly sorbed onto phytoplankton and its accumulation was much higher than that of phthalate. The uptake of these two compounds by the mussels increased with increasing temperature and salinity (for dioxin only). The dietary assimilation of the two contaminants was rather modest (10-64% for dioxin and 20-47% for phthalate), and was greatly dependent on the food species and concentration. Interestingly, dietary assimilation increased with increasing diatom food concentration. Gut passage time was partially responsible for the variable dietary assimilation. Given the high dissolved uptake rate and the modest dietary assimilation, aqueous exposure was predicted to be the dominant bioaccumulation source for both dioxin and phthalate in the green mussels under most conditions.
Environmental pollution (Barking, Essex: 1987) 04/2013; · 3.43 Impact Factor
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ABSTRACT: Pearl River Estuary (PRE) is the largest estuary in Southern China and there has been an increasing concern of metal pollution due to regional industrialization. In this study, we investigated the spatial variation of metal pollution (Ag, As, Cd, Cu, Pb, and Zn) as well as their subcellular handling in the oyster Crassostrea hongkongensis. Hot spots of metal contamination in the oysters were found in different sites, suggesting that there were different sources of metals in the estuary associated with industrial activity. Metals differed in their subcellular bindings in the oysters from different locations. Metal distribution in the biologically detoxified fraction decreased for Cu but increased for Zn with increasing contamination in the oysters. For Zn, there was a significant difference in its two detoxification pools (metal-rich granules and metallothionein-like proteins) in response to Zn contamination. The high Cd concentrations in oysters may carry a high Cd hazard to the consumers.
Marine pollution bulletin 03/2013; · 2.63 Impact Factor
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ABSTRACT: Arsenic speciation and concentrations were determined in mollusks and crustaceans in the intertidal zone from twelve locations in Zhanjiang estuary, South China. Metal concentrations (Ag, As, Cd, Cu, Hg, Ni, Pb, and Zn) were also concurrently determined in these species. Arsenic speciation analysis showed that the less-toxic arsenobetaine (AsB) constituted 80.6-98.8 % of all As compounds, and dimethylarsinic acid (DMA) constituted 0.47-3.44 %. Monomethylarsonic acid (MMA) and As(V) were only detected in the whelk Drupa fiscella and the crab Heteropilumnus ciliatus, respectively. Arsenite [As(III)] was not detected in any of the sampled specimens, but there were also unidentified other As species. A strong spatial variation of metals in the oyster Saccostrea cucullata was found in the estuary, confirming that oysters can be used as a good biomonitor of metal contamination in the studied area. The concentrations of eight metals in the studied mollusks and crustaceans clearly revealed that these invertebrates accumulated different metals to different degrees. Furthermore, As, Cd, Cu, Hg, and Pb contents in mollusks and crustacean samples were below the Food and Agricultural Organization (FAO) safe concentrations, thus there was no obvious health risk from the intake of the metals through marine mollusks and crustaceans consumption.
Ecotoxicology 03/2013; · 2.36 Impact Factor
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ABSTRACT: We conducted a large scale investigation of the bioaccessibility of 12 trace elements from 11 marine mollusc species (scallop, oyster, clam, abalone, snail, and mussel) collected from five locations in Chinese coastal waters. The bioaccessibility of all the 12 trace elements was generally high, with the average values ranging from 42.5% to 90.7%. The highest bioaccessibility was observed for As, Cu, Ni and Se, and the lowest for Fe, Co and Pb. Steaming decreased the bioaccessibility of all 12 trace elements and thus diminished their risks. No correlation was observed between the bioaccessibility and the total concentration of the 12 elements. However, there was a significant correlation between the bioaccessibility of the 12 elements and their subcellular distribution. For most trace elements, a significantly negative relationship was demonstrated between the bioaccessibility and the elemental partitioning in the metal-rich granule fraction or in the cellular debris fraction, and a significantly positive correlation was observed between the bioaccessibility and the elemental partitioning in the heat-stable protein fraction and in the trophically available fraction. Hence, the elemental subcellular distribution, especially the elemental partitioning in the trophically available fraction, might be a good predictor of the bioaccessibility and risks of trace elements in molluscs.
Food and chemical toxicology: an international journal published for the British Industrial Biological Research Association 02/2013; · 2.99 Impact Factor
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ABSTRACT: Nassarid snails are important opportunistic scavengers widely found in marine intertidal shores and trophic transfer is a predominant source of metal accumulation in these species, thus there is a significant need to understand the controls of metal trophic transfer. In the present study, we took advantage of a severely contaminated estuary and collected two prey organisms (oysters Crassostrea angulata and barnacles Fistulobalanus albicostatus) with different contamination histories. These naturally contaminated prey were fed to a marine neogastropod Nassarius siquijorensis for a period of up to 7 weeks. We then investigated the influences of prey type, metal burden, and subcellular distribution in the prey on the metal accumulation, trophic transfer, and potential toxicity on N. siquijorensis. We demonstrated an obvious negative relationship between the trophic transfer and the metal concentration in prey or the metal dosage. N. siquijorensis exhibited food avoidance behavior to the Cu contaminated food, which effectively reduced the metal ingestion and resulted in a decrease of trophic transfer, as well as a potential toxic effect from dietary exposure. On the other hand, our results also implied the metal-specific impact of subcellular metal distribution in prey on the trophic transfer to N. siquijorensis. Our study suggested that metal burden and feeding avoidance should be considered in studying the trophic transfer of metals in marine benthic food chain.
Aquatic toxicology (Amsterdam, Netherlands) 02/2013; 132-133C:111-118. · 3.12 Impact Factor
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ABSTRACT: To investigate the potential influence of the contamination of copper (Cu) or zinc (Zn), the abalone Haliotis discus hannai was exposed to waterborne or macroalgae-borne Cu or Zn over a period of 8weeks. Both Cu and Zn were effectively accumulated by the abalones from water or macroalgae, but their concentration factors and trophic transfer factors were low due to the regulation of Cu and Zn accumulation. Following waterborne or dietary exposure, the abalones exhibited different accumulation patterns of Cu and Zn. The tissue Zn burden decreased quickly after the initial accumulation, and the incoming Zn was mainly deposited in the viscera. In contrast, the tissue Cu burden increased rapidly and gradually reached a steady state. The abalone muscle exhibited a comparable storage capacity of Cu as the viscera and the accumulated Cu in muscle was mainly derived from the dissolved phase instead of trophic transfer. The feeding and growth of the abalone were not influenced in all the exposure regimes. Moreover, the significant induction of metallothionein indicated that the bioaccumulated metals were actively detoxified. In the metal-exposed abalones, more Cu was distributed into the biologically detoxified fractions (metallothionein-like protein and/or metal-rich granule), whereas no significant subcellular redistribution of Zn was observed. Our study suggested that the abalone may have high endurance to the contamination of Cuor Zn.
Ecotoxicology and Environmental Safety 02/2013; · 2.29 Impact Factor
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ABSTRACT: Understanding the underlying mechanisms governing metal toxicity is crucial for predicting the risks and effects of metal pollutants. We hypothesized that metal toxicity is related to a threshold concentration of metabolically available metal but not to the total body metal concentration. Following a two-month laboratory Zn exposure, we characterized mortality and Zn bioaccumulation and subcellular partitioning in the oyster Crassostrea hongkongensis sampled from three sites with contrasting histories of Zn exposure and one multiple-metal contaminated site. Large differences in Zn sensitivity, lethal body concentration, and detoxification capability between sites were observed. Specifically, the oysters from the highly Zn-contaminated site were more tolerant to Zn exposure than those from the relatively clean ones, and the former accumulated and detoxified more Zn and had a significantly higher lethal body Zn concentration. The accumulation of Zn in the metabolically available pool (operationally defined as the metal-sensitive fraction) in the oysters from the multiple-metal contaminated site was relatively fast, and correspondingly they were highly sensitive to Zn exposure. The lethal threshold concentration of total body Zn varied significantly within the four sites, and thus total body Zn concentration could not serve as a suitable toxicity indicator. Importantly, Zn accumulation within the operationally defined metabolically available pool better explained variances in mortality than Zn accumulation in the whole body. Our results suggested that Zn toxicity is governed by its accumulation in the metabolically available pool, not the total accumulated Zn concentration.
Aquatic toxicology (Amsterdam, Netherlands) 02/2013; 132-133C:26-33. · 3.12 Impact Factor
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ABSTRACT: The toxicity of manufactured silver nanoparticles (AgNPs) has been widely studied, but the influence of AgNPs on the major ions (such as sodium [Na] and calcium [Ca]) regulations are unknown. In the present study, a freshwater cladoceran Daphnia magna was exposed to commercial AgNPs coated with polyvinylpyrrolidone. After 48 h, the Na body content was significantly reduced by AgNO(3) exposure, but the Ca body content was significantly increased under AgNO(3) and AgNPs exposures, respectively. No effect was observed on the body concentrations of Na and Ca at 50- to 500-µg/L AgNPs with 1-µM cysteine addition. Exposure of AgNO(3) and AgNPs inhibited the Na influx and elevated the Na efflux. In contrast, their exposure increased the Ca influx, but did not affect the Ca efflux. Our results demonstrated the significant influences of AgNO(3) and AgNPs (without cysteine) on Na and Ca regulations. Such effect of AgNPs on Na and Ca regulation disappeared after cysteine addition, indicating that the soluble Ag released from AgNPs played a major role in the ionoregulatory dysfunction. Environ. Toxicol. Chem. © 2013 SETAC.
Environmental Toxicology and Chemistry 01/2013; · 2.81 Impact Factor
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ABSTRACT: Gastropods are often the top predators in marine benthic environments, and trophic transfer is the predominant route by which metals are accumulated in these predators. In the present study, the potential influences of prey composition on the trophic transfer, accumulation, subcellular distribution and metallothionein induction of six metals (Ag, As, Cd, Cu, Pb and Zn) in a predator Nassarius siquijorensis were investigated. The snails were fed venerid clams Ruditapes philippinarum, mussels Perna viridis, oysters Crassostrea angulata or barnacles Fistulobalanus albicostatus, each differing greatly in their metal accumulation and handling patterns. N. siquijorensis showed prey-specific bioaccumulation and trophic transfer of the six metals. In general, the body burdens of metals in the viscera and muscles of N. siquijorensis increased with increasing exposure period and metal concentration in the four prey. The calculated trophic transfer factors (TTFs) of the metals in different prey varied and were the highest for clams and mussels prey, indicating that metal bioavailability from these prey was higher than that from barnacles and oysters. All the studied metals except Pb were enriched during transfer to the snails. The subcellular metal distribution in the viscera was affected by prey composition. Exposure to the four natural prey induced MTs, which may be used as a better biomarker for muscle than for viscera for metal stress. Our results imply that metals from different natural prey have different bioavailability and may help better understand the trophic transfer of metals in marine benthic food chain.
Aquatic toxicology (Amsterdam, Netherlands) 10/2012; · 3.12 Impact Factor
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ABSTRACT: Metal (Cd, Pb, Cr, Ni, Mn, Cu, and Zn) concentrations in different fish species sampled from two distinct (phytoplankton- and macrophyte-dominated) lake zones of a large, shallow freshwater lake, Taihu Lake, were investigated. Concentrations of most metals in muscle of the small-sized fish (Protosalanx hyalocranius, Pseudorasbora parva, and Rhodeus ocellatus) were always significantly higher than those of the large-sized (Carassius auratus, Cyprinus carpio, and Aristichthys nobilis) and carnivorous fish (Pelteobagrus fulvidraco, Cultrichthys erythropterus, and Erythroculter ilishaeformis). Metal accumulation in the small-sized fish from the phytoplankton-dominated lake zone was always greater than those from the macrophyte-dominated lake zone in summer. However, no significant differences were observed between the two lake zones for most metals in the small-sized fish collected in winter. Metal accumulation in gills, liver, and intestine of the large-sized fish from the phytoplankton-dominated lake zone was generally greater than those from the macrophyte-dominated lake zone in summer. The presence of distinct ecological regions in the lake might affect the metal distribution in the small-sized or large-sized fish. For the carnivorous fish, however, metal concentrations in fish tissues from the two different lake zones were not significantly different, suggesting that metal accumulation in carnivorous fish might be less influenced by the ecological status of the lake.
Ecotoxicology and Environmental Safety 09/2012; · 2.29 Impact Factor
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ABSTRACT: The toxicity of silver nanoparticles (AgNPs) has been widely investigated, but the process of bioaccumulation such as uptake remains less studied. In the present study, we employed the radioisotope ((110m)Ag) to trace the behaviors of commercial AgNPs with three nominal particle sizes (20, 50, and 100 nm) and two surface coatings (citrate and tannic acid) in a model organism Daphnia magna . The size distributions of AgNPs in the medium increased continuously as the exposure time increased, especially for the smallest AgNPs (20 nm). Cysteine, the amino acid containing thiol group, significantly enhanced particle aggregation, with a 30-fold increase of the hydrodynamic size for AgNPs with 20 nm nominal size after 6 h of exposure. We demonstrated that the influx rates of AgNPs into daphnids were size-dependent. At 500 μg/L AgNPs with 1 μM cysteine, the influx rates of AgNPs were in the sequence 20 nm > 50 nm > 100 nm (nominal size) for both types of surface coatings. Such sequence was consistent with the size distribution in the medium. More than 60% of AgNPs were distributed in the gut of daphnids, indicating that ingestion was the dominant uptake pathway. The size-dependent influx rate was also observed at different AgNPs concentrations. The measured uptake rate constant was lower than that of AgNO(3) at low AgNPs concentration, but it became higher at high AgNPs concentrations. Our study highlighted the indispensability of characterizing the size distribution of AgNPs dispersed in the medium in studying the AgNPs uptake. The accurate quantification of AgNPs influx rate suggested an uptake pathway entirely different from that of AgNO(3) in the daphnids.
Environmental Science & Technology 09/2012; 46(20):11345-51. · 4.80 Impact Factor
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Aquaculture 08/2012; 356-357:98-104. · 2.04 Impact Factor
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ABSTRACT: We demonstrate that a two-photon excitation fluorescence lifetime imaging technology can rapidly and noninvasively assess the cadmium (Cd)-induced toxic effects in a marine diatom Thalassiosira weissflogii. The chlorophyll, an intrinsic fluorophore, was used as a contrast agent for imaging of cellular structures and for assessment of cell toxicity. The assessment is based on an imaging-guided statistical analysis of chlorophyll fluorescence decay. This novel label-free imaging method is physically based and free of tedious preparation and preprocessing of algal samples. We first studied the chlorophyll fluorescence quenching induced by the infrared two-photon excitation laser and found that the quenching effects on the assessment of Cd toxicity could be well controlled and calibrated. In the toxicity study, chlorophyll fluorescence lifetime images were collected from the diatom samples after exposure to different concentrations of Cd. The alteration of chloroplast structure at higher Cd concentration was clearly identified. The decay of chlorophyll fluorescence extracted from recorded pixels of high signal-to-noise ratio in the fluorescence lifetime image was analyzed. The increase of average chlorophyll fluorescence lifetime following Cd treatment was observed, indicating the Cd inhibition effect on the electron transport chain in photosynthesis system. The findings of this study show that the temporal characteristics of chlorophyll fluorescence can potentially be utilized as a biomarker for indicating Cd toxicity noninvasively in algal cells.
Planta 07/2012; 236(5):1653-63. · 3.00 Impact Factor
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Environmental Toxicology and Chemistry 06/2012; · 2.81 Impact Factor
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ABSTRACT: There is growing awareness of the toxicological effects of metal-contaminated invertebrate diets on the health of fish populations in metal-contaminated habitats, yet the mechanisms underlying metal bioaccumulation and toxicity are complex. In the present study, marine fish Terapon jurbua terepon were fed a commercial diet supplemented with specimens of the polychaete Nereis diversicolor or the clam Scrobicularia plana, collected from four metal-impacted estuaries (Tavy, Restronguet Creek, West Looe, Gannel) in southwest England, as environmentally realistic metal sources. A comparative toxicological evaluation of both invertebrates showed that fish fed S. plana for 21 d exhibited evident mortality compared to those fed N. diversicolor. Furthermore, a spatial effect on mortality was observed. Differences in metal doses rather than subcellular metal distributions between N. diversicolor and S. plana appeared to be the cause of such different mortalities. Partial least squares regression was used to evaluate the statistical relationship between multiple-metal doses and fish mortality, revealing that Pb, Fe, Cd and Zn in field-collected invertebrates co-varied most strongly with the observed mortality. This study provides a step toward exploring the underlying mechanism of dietary toxicity and identifying the potential causality in complex metal mixture exposures in the field.
Aquatic toxicology (Amsterdam, Netherlands) 04/2012; 120-121:1-10. · 3.12 Impact Factor
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ABSTRACT: Bivalves are employed widely as biomonitors of metal pollution and proteomics has increasingly been applied to solve ecotoxicological issues. This study aimed to investigate the effects of Cd exposure on the bioaccumulation of other trace elements and reveal the molecular mechanisms using proteomics technologies. The results showed that Cd exposure resulted in remarkable changes in body concentrations of Zn, Cu, Ag, Co, Ni, Pb, and Se in four marine bivalves (scallop Chlamys nobilis, clam Ruditapes philippinarum, mussel Perna viridis, and oyster Saccostrea cucullata). Generally, the bivalves exposed to higher Cd concentration accumulated higher concentrations of Zn, Cu, and Se, but a lower concentration of Co. The accumulation of Ag, Ni, and Pb was specific for different species. The data strongly suggest that the influences of one metal exposure on the bioaccumulation of other metals/metalloids need to be considered in interpreting body concentrations of the elements in the biomonitors. Cd exposure had little effect on bivalve proteomes, and the identified proteins were insufficient to explain the observed disruption of trace element metabolism. However, protein expression signatures composed of the altered proteins could distinguish the clams and the mussels with different body Cd levels. The strong up-regulation of galectin in Cd-exposed oysters indicated the protein as a novel biomarker in environmental monitoring.
Environmental Toxicology and Chemistry 04/2012; 31(6):1292-300. · 2.81 Impact Factor
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ABSTRACT: In the present study, the dissolved uptake, dietary assimilation, and elimination of arsenic (initially added as arsenate) in the freshwater cladoceran Daphnia magna were examined. A biphasic correlation between the arsenic uptake rate and its ambient concentration, as well as a two-saturation-site arsenic uptake competition with phosphate was observed. The calculated uptake rate constant, as influenced by the ambient phosphorus concentration, ranged from 0.035 to 0.35 L/g/d. Food concentration substantially decreased (by 23.2-64.4%) the arsenic assimilation efficiency with the incipient limiting algal food concentration of 3.86 mg/L dry weight. Arsenic assimilation by the daphnids was independent of their own phosphorus status, but was lower when their algal diet was phosphorus-limited and thus contained a higher proportion of arsenite due to the enhanced biotransformation. Arsenic efflux rate constant ranged from 0.34 to 0.44 d(-1) with increased food concentration slightly facilitating its loss. Excretion, accounting for 51.3 to 60.6% of total loss, was the dominant pathway for arsenic elimination with a remarkable contribution from offspring production (24.7-29.8%), whereas molting (3.64-4.05%) and egestion (7.9-11.9%) had minor roles only. According to the well-established biokinetic model, dietary assimilation was predicted to be the main pathway for arsenic bioaccumulation in the daphnids, and arsenic has a great potential to be biodiminished along the food chain.
Environmental Toxicology and Chemistry 04/2012; 31(6):1283-91. · 2.81 Impact Factor
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ABSTRACT: In field-collected juvenile blackhead seabream Acanthopagrus schlegeli schlegeli, measured total mercury (THg) and methylmercury (MeHg) concentrations were related to 0.19 and 0.33 power of fish mass over a wide size range (more than 50-fold). The causative factors remain unclear. In this study, size-dependent biokinetic parameters for both inorganic mercury [Hg(II)] and MeHg were estimated, and their relative contributions to size-related Hg accumulation were further assessed. Except for the MeHg dietary assimilation efficiency (AE), which was not affected by the fish size, other examined biokinetic parameters showed either positive (Hg(II) AE) or negative correlations (growth rate constant-g, dissolved uptake rate constant-k(u) and efflux rate constant-k(e)) with fish size. The biokinetic variation explained the observed allometric pattern of Hg accumulation in juveniles. Especially, both size-related g and k(e) were the key drivers. The current study addressed the importance of size-related biokinetics, in particular the k(e) and g, which have important implications to manage Hg contamination in fisheries.
Environmental pollution (Barking, Essex: 1987) 04/2012; 163:192-8. · 3.43 Impact Factor
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ABSTRACT: The toxic effects of inorganic mercury [Hg(II)] and methylmercury (MeHg) on the photosynthesis and population growth in a marine diatom Thalassiosira weissflogii were investigated using two methods: two-photon excitation fluorescence lifetime imaging (FLIM) and flow cytometry (FCM). For photosynthesis, Hg(II) exposure increased the average chlorophyll fluorescence lifetime, whereas such increment was not found under MeHg stress. This may be caused by the inhibitory effect of Hg(II) instead of MeHg on the electron transport chain. For population growth, modeled specific growth rate data showed that the reduction in population growth by Hg(II) mainly resulted from an increased number of injured cells, while the live cells divided at the normal rates. However, MeHg inhibitory effects on population growth were contributed by the reduced division rates of all cells. Furthermore, the cell images and the FCM data reflected the morphological changes of diatom cells under Hg(II)/MeHg exposure vividly and quantitatively. Our results demonstrated that the toxigenicity mechanisms between Hg(II) and MeHg were different in the algal cells.
Aquatic toxicology (Amsterdam, Netherlands) 04/2012; 110-111:133-40. · 3.12 Impact Factor
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ABSTRACT: We investigated the kinetics of Hg(II) and MeHg accumulation and the synthesis of phytochelatins (PCs), cysteine (Cys), glutathione (GSH), and γ-glutamylcysteine (γ-EC) in a marine diatom Thalassiosira weissflogii during a 3-h (short-term) and a 96-h (long-term) exposure period, and during a subsequent 96-h recovery period. MeHg induced the synthesis of a significant level of GSH, but it was Hg(II) that gave rise to significant levels of other non-protein thiol compounds. The thiol compounds Cys, γ-EC, and PC(2-3) were induced in T. weissflogii within the first 30 min of exposure, followed by PC(4), but the concentrations of all six compounds returned to the control levels after the 96-h recovery period. The kinetics of these non-protein thiol compounds pointed to a rapid cellular response to environmental mercury pollution. After a first decrease, the molar ratio of PC-SH (sulfhydryl in PCs) to intracellular Hg increased slightly which demonstrated the role of PCs in Hg(II) detoxification. However, PC-SH was bound with Hg(II) at a stoichiometric ratio of 0.1-0.3, indicating the involvement of other detoxification mechanisms. Elucidating the effects of mercury on intracellular non-protein thiol pools may help us better understand the metal detoxification in phytoplankton.
Journal of hazardous materials 03/2012; 217-218:271-8. · 4.14 Impact Factor
