Metal-rich Sites Research Articles

Effective removal of Pb(II) and Ni(II) ions by Bacillus cereus and Bacillus pumilus: An experimental and mechanistic approach

Herein, we report a bacteria-based strategy as an efficient, reasonable, benign, and promising methodology for remediating heavy metals fed waterbodies. The contemporary study deals with isolating, screening, and characterizing heavy metal resistive bacteria from metal-rich sites. The transcriptome analysis reveals the identity of the isolated species as Bacillus pumilus and Bacillus cereus. Batch studies put forth the bioremoval results in designed conditions of different pH, concentration, dose, and time. The mechanistic actions are drawn using complementary techniques such as Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). The theory of surface adsorption of lead (Pb(II)) and nickel (Ni(II)) is further fostered by the application of adsorption isotherms. The conducted studies establish the bacterial morphological stratagems and multifarious biochemical approaches for countering metallic ions of Pb(II) and Ni(II). The exhibition of significant removal results by the isolated bacterial strains in simulated water samples with remarkable proliferation rates has opened up its favorability for industrial platforms.

RETHINKING EARLY MEDIEVAL ‘PRODUCTIVE SITES’: WEALTH, TRADE, AND TRADITION AT LITTLE CARLTON, EAST LINDSEY

AbstractThe rising popularity of hobbyist metal detecting has provided early medieval scholars with various important new datasets, not least the concentrations of metalwork commonly known as ‘productive sites’. Awareness of these foci derives almost exclusively from archaeological evidence, yet they continue to be interpreted through a documentary lens, and are frequently labelled ‘monasteries’. Using the recently discovered site of Little Carlton, Lincolnshire, as a case study, it is argued that comprehension of metal-rich sites is significantly furthered by turning to archaeologically-orientated research agendas and terminologies. As a consequence, seventh- to ninth-century Little Carlton can be understood as one element of a high-status ‘meshwork’ within early medieval East Lindsey, in which elite power was articulated in the landscape through a number of contemporary centres. On site, archaeology indicates the presence of occupation, burial and craft working, but shows that highly symbolic indigenous practices were taking place too, including intentional deposition into a naturally-occurring pond. Evidence for activity either side of the seventh to ninth centuries also stresses the importance of long-term trajectories in shaping the character of places previously celebrated for their finds-rich phases alone.

Metabolic potentials of members of the class Acidobacteriia in metal‐contaminated soils revealed by metagenomic analysis

The relative abundance of Acidobacteriia correlated positively with the concentrations of arsenic (As), mercury (Hg), chromium (Cr), copper (Cu) and other metals, suggesting their adaptation of the metal-rich environments. Metagenomic binning reconstructed 29 high-quality metagenome-assembled genomes (MAGs) associated with Acidobacteriia, providing an opportunity to study their metabolic potentials. These MAGs contained genes to transform As, Hg and Cr through oxidation, reduction, efflux and demethylation, suggesting the potential of Acidobacteriia to transform such metal(loid)s. Additionally, genes associated with alleviation of acidic and metal stress were also detected in these MAGs. Acidobacteriia may have the capabilities to resist or transform metal(loid)s in acidic metal-contaminated sites. Moreover, these genes encoding metal transformation could be also identified in the Acidobacteriia-associated MAGs from five additional metal-contaminated sites across Southwest China, as well as Acidobacteriia-associated reference genomes from the NCBI database, suggesting that the capability of metal transformation may be widespread among Acidobacteriia members. This discovery provides an understanding of metabolic potentials of the Acidobacteriia in acidic metal-rich sites.

Hvordan har metallgjenstander funnet veien til pløyelaget?

Due to increasing hobby metal detecting, archaeological museums receive thousands of finds each year. To improveour understanding of their depositing history and possible connection to structures beneath the plough-zone, theDirectorate for Cultural Heritage selected the find-rich field at Storhov in Elverum for a pilot study. This article presentsan outline of the results from the three-part methodological survey at Storhov; comparing and assessing metaldetecting finds, results from archaeological excavation, and interpretations from GPR survey on the site.In light of these results, the article discusses how the metal detecting finds ended up in the ploughsoil. Based on types,dates and distribution of finds and structures, we conclude that most of the finds – ornaments, tools, and small itemscarried in a belt or in a pouch – were distributed through manuring or lost while working in the field. Thus, whensystematic metal detecting on a site predominantly produces such finds, it is a suitable method to bring forth informationon cultivation in the Iron and Middle Ages. The results also suggest that in sites where such metal finds dominate, thereis potential for finding remains from settlements and graves, either on the site or nearby. However, such finds cannot beregarded as a reliable guidance to the precise location of such structures – if at all preserved. We regard our analysisand tentative conclusions as a step towards developing a methodological package and a set of assessment criteria forheritage management of the metal rich sites and research on the finds.

Biomimetic approach for multifarious synthesis of nanoparticles using metal tolerant fungi: A mechanistic perspective

In present study, fungi isolated from metal rich site were explored for metal tolerance capacity and potential of multifarious synthesis of metal nanoparticles (NPs). Total 9 different fungi were isolated from rhizospeheric soils and molecularly characterized. Penicillium janthinellum DJP06 showed maximum metal tolerance capacity and synthesized gold and silver NPs. Detailed characterization confirmed the synthesis of protein capped, crystalline natured, spherical shaped gold and silver NPs. Mechanistic studies suggested involvement of fungal secretome proteins in the NPs synthesis. To find out the active protein(s) responsible for multifarious synthesis of NPs, the dialyzed proteins were fractionated by chromatography technique. Individual protein fractions were separately checked for their ability to synthesize NPs. Results suggested involvement of multiple proteins in an interactive manner for NPs synthesis. Testing the ability of these proteins for multifarious synthesis of other commercially important NPs will be an exciting future possibility.

Exploring Spatial Patterns at “Nørholm”, a Metal-rich Site by the Limfjord, Northern Denmark

Private metal detecting currently has a massive impact on North European archaeology. However, due to the poor contextual data of the finds, the unsystematic search methods and not least insufficient excavations at detected sites, the spatial understanding of the sites and the knowledge potentially to be gained from metal finds from the plough layer is still limited. This paper presents a programme of investigations at the most productive detector site in Jutland, “Nørholm”, which offers a framework for interpretation of distribution patterns of the metal finds recovered over more than two decades by private detectorists. It is argued that overall changes in settlement patterns as well as changes in the associated field systems are major dynamics behind the spread of metal detector finds. A detailed, chronological mapping of the distribution of finds thus allow a reconstruction of the history of settlement and land use during the Late Iron Age and the Middle Ages.

Synthetic nanodiamonds (SNDs) containing bimetallic Ni(Co)–Fe composites: preparation, characterization and catalytic performance in the reaction of CO2 methanation

In this article, we present the preparation, characterization, and catalytic performance of bimetallic Co93Fe07 and Ni80Fe20 active mass loaded on synthetic nanodiamonds (SNDs) in the carbon dioxide (CO2) methanation. The pristine SNDs possessing a developed specific surface are thermally stable and inert to the reaction mixture of CO2 and dihydrogen. However, it is shown that 100% conversion of CO2 into methane can be reached at the lower temperature than that for a massive Co93Fe07 or Ni80Fe20 catalyst when 20 wt.% of the catalyst mass was loaded on the surface of SNDs. The catalytic activity of the prepared bimetallic/SNDs composites is estimated as the minimum temperature at the maximum conversion of CO2 at atmospheric pressure: it is 325 and 290 °C for Co93Fe07/SNDs and Ni80Fe20/SNDs, respectively. Thermal desorption studies showed that the methanation over Co-Fe/SNDs and Ni-Fe/SNDs catalysts run through the stage of CO2 dissociation into carbon and oxygen atoms and their subsequent interaction with hydrogen to form methane and water molecules. Scanning electron microscopy studies have shown that the presence of transition metal-rich sites on the surface of the carrier contributes to the improvement of efficiency of the Ni80Fe20 catalyst action.

Free metal ion availability is a major factor for tolerance and growth in Physcomitrella patens

Metal rich sites are populated by only a few specialized vascular plant species allowing less competitive bryophytes to inhabit these ecological niches. On such sites, many different stress factors may interact with the plants and foreclose statements on the individual effects of a single factor, therefore the means for this tolerance are difficult to investigate. This study uses the cultivation of the moss Physcomitrella patens on solid media under controlled environmental conditions in order to study the growth inhibiting effects of copper, zinc and cadmium and the contribution of corresponding anions as chlorides, sulfates and ethylenediaminetetraacetic acid, respectively. Availability of the metals to plants was estimated both by water extraction with subsequent measurement by inductively coupled plasma mass spectroscopy and by modeling metal speciation using Visual MINTEQ a free chemical equilibrium model software.A decreased ratio of gametophyte to protonema growth (G:P) was observed as a first reaction to even very low metal levels; G:P measurements can therefore be used as sensitive stress indicators in P. patens. Though all metals caused inhibiting effects with all anions, ethylenediaminetetraacetic acid chelates showed up to three orders of magnitude less toxic. Using Visual MINTEQ, we modeled the water solubility of zinc almost perfectly but achieved less accurate results for copper. For both metals, water solubility was rather under- than overestimated, indicating that adsorption to the agar played only a minor role in controlling metal solubility. Free metal cations were useful to explain growth inhibition which could not be fully explained by total metal concentration, calculated or experimentally determined water solubility. Especially the low toxicity of ethylenediaminetetraacetic acid chelates could be explained satisfactory by shielding of the metal ions.

UMBRELLA: Using MicroBes for the REgulation of heavy metaL mobiLity at ecosystem and landscape scAle

This special issue focuses on metal-contaminated areas resulting from mining activities. These sites are characterized by low nutrient availability, poor soil quality, and low pH, in addition to high metal loads. The contamination at former mining sites most often is associated with acid mine drainage leading to the dispersal of metals. The resulting areas are compromised with respect to both use of land for, e.g., agronomy and forestry, and groundwater, the main source of drinking water, restricting future use. In addition, the contamination can spread, if not attended to, contaminating additional, previously non-contaminated ecosystems. Government regulations for effective management of contaminated sites exist worldover, and reclamation of acid mine drainage-influenced areas attracts growing interest. Remediation actions are necessary, which, in addition to geo-engineering strategies, increasingly include monitored natural attenuation and bioremediation. This needs to be based on a detailed understanding of processes in bio-geo interactions at metal-contaminated sites, which is addressed here to provide an integrated approach summarized in a scheme for useful application of each of these remediation actions shown in this special issue at a generalized former mining site. The proposed applications help to minimize the risk to human health and environmental impact and are cost-efficient. Soil is the basis of terrestrial life and has a major impact on human life through its use for agriculture, forestry, or general land use. In addition, it remains the largest terrestrial ecosystem that is shaped by high numbers of microorganisms and plant roots. The metabolic activities of both microorganisms and plants sustain pedogenesis which, however, differs with respect not only to base rock material and climatic conditions, but also to, e.g., pollution. Root exudates as well as microbiological acidification and release of chelating agents take part in heavy metal mobilization and immobilization processes, which are of high impact at metal-rich sites. The ecotoxicologically relevant heavy metal concentrations are dependent on interaction with soil particles and microbial surfaces; hence, inoculation strategies may improve future land use. Mobilization and distribution pathways for metals from source, where geo-engineering techniques may be deployed, to sink need to be re-evaluated. Nature has evolved ecosystems able to cope with high metal loads, and by learning from the evolutionary and biological processes, it may be feasible to adopt additional strategies for bioremediation. During natural attenuation, new minerals can be formed. This might lead to supergenic ore formation and hence provides means to even use these metals without disturbing new, natural sites. In this special issue, we will discuss all mentioned mobilization and immobilization mechanisms to contribute to a general understanding of bioremediation potentials. Thus, we may draw on the potential of natural attenuation instead of premature application of high-cost geo-engineering, depending on sitespecific parameters. This concept will allow for the reduction of the costs of an estimated 38 billion Euro per year incurred by society at large for soil destruction and environmental degradation. The formation of acid mine drainage (AMD) or also of acid rock drainage (ARD) is a process related to unearthing metal ores, many of which are sulfidic ores. Similar processes leading to AMD apply to coal mining, since coal also contains sulfur in pyrite and marcasite as well as organically bound sulfur. The anoxic environment in the mine does provide Responsible editor: Philippe Garrigues

CadA of Mesorhizobium metallidurans isolated from a zinc-rich mining soil is a PIB-2-type ATPase involved in cadmium and zinc resistance

Mesorhizobium metallidurans STM 2683T is a nitrogen-fixing bacterium that nodulates Anthyllis vulneraria in mine tailings highly contaminated in zinc, lead and cadmium. To study the mechanisms whereby this bacterium copes with metals, we functionally screened a cosmid genomic library of M. metallidurans for zinc or cadmium tolerance. A cosmid clone harbored a gene encoding PIB-type ATPase homologous to CadA that leads to cadmium and zinc resistance in Escherichia coli. The CadA protein structure presents one duplication of the two N-terminal metal binding domains (i.e. a heavy metal-associated domain followed by a histidine-rich domain) which allows specific binding to zinc and cadmium cations. A cadA-deleted strain of M. metallidurans failed to grow at high zinc concentrations (2mM) and its growth was delayed at lower zinc concentrations. Expression studies using a transcriptional fusion of cadA promoter to gfp showed that cadA is specifically induced in a dose-dependent manner by zinc and cadmium in M. metallidurans in vitro conditions and into A. vulneraria nodules after Zn stress. Metal induction sensitivity was increased in the strain where cadA gene was deleted.This study identified cadA as a first mesorhizobial resistance determinant involved in detoxification of cadmium and zinc and which confers upon M. metallidurans greater capacity for coping with high zinc concentrations. This improves the knowledge of this bacterium for potential use as a symbiotic inoculant of Anthyllis in phytostabilization strategies of metal-rich sites.

Metal leaching, acidity, and altitude confine benthic macroinvertebrate community composition in Andean streams

Andean streams drain metal-rich bedrock and are subjected to an extreme altitude gradient, which may create highly selective conditions for life. The aim of the present study was to evaluate the combined effects of metals and altitude on benthic macroinvertebrate community composition in Andean streams. Metal-rich sites were characterized by high metal concentrations and low pH, and high-altitude sites were characterized by high ultraviolet-B radiation and low concentrations of dissolved organic matter. Canonical correspondence analysis indicated that the patterns in faunal composition were best explained by metals followed by altitude, with dipterans and collembolans occurring mostly under harsh conditions of high altitude and high metal levels. Interaction between metals and altitude was most evident at metal-rich sites. It is suggested that in Andean streams, metal leaching from igneous rock and altitude may be important factors confining benthic macroinvertebrate communities, reducing their numbers and changing their composition toward specialized taxa.

BioRem—Database for Remediation of Heavy Metal Rich Habitats and Protection of Their Biodiversity

BioRem is an open access on-line resource, which aims to document the biodiversity of terrestrial heavy metal rich sites around the globe that are the habitats of specialized metal tolerant organisms (MTOs). A comprehensive inventory of MTOs together with an analysis of environmental conditions and research about the adaptations of MTOs shall support the development of holistic models about the functioning of heavy metal ecosystems and lead to an improved understanding of interactions and adaptation strategies of MTOs. Furthermore, the database enables the identification of plants and microorganisms suited for remediation actions where protection of the population and the environment is needed. Information about scientific data shall lay the ground for the definition of heavy metal habitats with unique biocoenoses as reservoirs of biodiversity: accordingly, BioRem shall be a resource for education and for dissemination of our knowledge about the ecology of heavy metal rich sites and their habitats, and it shall provide tools for the evaluation of socio-economic strategies for either remediation or preservation of heavy metal habitats. Where needed, alternative strategies for the survival of MTOs shall be developed, hence contributing to the aim of the G?teborg 2010 target to halt loss of biodiversity.

Accumulation and toxic effect of arsenic and other heavy metals in a contaminated area of West Bengal, India, in the lichen Pyxine cocoes (Sw.) Nyl.

Ecological indicators can be used to assess the condition of the environment, to provide an early warning signal of changes in the surrounding environment or to diagnose the causes of an environmental problem. The study aims to evaluate the applicability of a common foliose lichen Pyxine cocoes (Sw.) Nyl., as an indicator to evaluate the arsenic and heavy metal rich sites. The naturally growing lichen and its substratum (bark) were utilized to biomonitor the accumulation of arsenic (As) and other heavy metals (Al, Cd, Cr, Cu, Fe, Pb and Zn) in Chinsurah, a highly As contaminated area of West Bengal. Significantly higher levels of Al, Cr, Fe, Pb and Zn (p<0.01), Cd and Cu (p<0.05) were found in the lichens especially in samples collected from road sites. Higher As concentration (48.1±2.1μgg−1) in samples were found near the paddy field, indicating pesticide-herbicides as its source used in agriculture. The substrate exhibits lower concentration of most of the metals while Cr, Cd and Pb were below detection limit. As evident from the bioaccumulation factor most of the metals accumulated in lichen thallus are air borne. Chl a and Chl b concentrations decreased significantly with increasing distance from roadside whereas the carotenoid and protein showed an enhanced level. The chlorophyll stability index, chlorophyll degradation and carotenoid contents were found to be the most sensitive parameters to assess the vitality of lichen thallus against changing environment.

Bioaccumulation and glutathione-mediated detoxification of copper and cadmium in Sphagnum squarrosum Crome Samml.

Physiological and biochemical responses, metal bioaccumulation and tolerance potential of Sphagnum squarrosum Crome Samml. to Cu and Cd were studied to determine its bioindication and bioremediation potential. Results suggest that glutathione treatment increases the metal accumulation potential and plays a definite role in heavy metal scavenging. High abundance of Sphagnum in metal-rich sites strongly suggests its high metal tolerance capabilities. This experiment demonstrates that S. squarrosum is able to accumulate and tolerate a high amount of metals and feasibility of its application as bioindicator and remediator test species of metal-contaminated environment.

Kinetics of trace metal accumulation and excretion in the polychaete Nereis diversicolor

The comparative kinetics of the accumulation of the trace metals copper, zinc and cadmium have been measured in the estuarine burrowing polychaete worm Nereis (Hediste) diversicolor from two sites: (a) a metal-rich site, Restronguet Creek, Cornwall, UK, which hosts a copper- and zinc-tolerant population of worms, and (b) the Blackwater estuary, Essex, UK as a control site. A sediment transfer experiment showed that the Blackwater worms responded to the increased copper bioavailability in Restronguet Creek sediment by accumulating significantly increasing copper concentrations over 50 days. The Restronguet Creek worms showed no significant change in copper concentration over 50 days in sediment from either site or in sand. Nevertheless, electron microscopy showed that some Restronguet Creek worms do appear to excrete accumulated copper, probably in association with renewal of the cuticle over a long time scale. The Blackwater worms did not accumulate extra zinc from the zinc-rich Restronguet Creek sediment, in probable reflection of the regulation of body zinc concentration by N. diversicolor. Radiolabelled zinc and cadmium were accumulated from labelled sediment and labelled solution by worms from both sites. The rate of uptake of labelled zinc from sediment was significantly greater in the Restronguet Creek worms, as was the rate of uptake of labelled cadmium from 10 μg l−1 dissolved exposure; other rates of uptake did not differ between populations. Mucus, which is secreted by Restronguet Creek worms in response to enhanced copper exposure, adsorbed very small proportions of zinc and cadmium present in solution, indicating that the mucus does not act as an adsorption barrier against excessive metal uptake by these worms.

Do seasonal changes affect metallothionein induction by metals in mussels, Mytilus edulis?

Mussels have been proposed as biomonitors of metal pollution based on the determination of metallothionein (MT) concentrations as a biomarker, but a comprehensive study taking into account both intersite and long-term temporal variations in MT and metal concentrations in different organs is lacking. Thus, the present study was designed to examine the concentrations of cytosolic and insoluble Cd, Cu, Zn, and MT in gills and digestive gland of mussels ( Mytilus edulis) of homogeneous size and age obtained from aquaculture and kept on a reference site or translocated to a metal-rich site throughout their reproductive season (March–October 1997). Relatively significant binding of metals to the insoluble fraction was observed in both tissues. In the digestive gland, monthly MT concentrations were strongly correlated to cytosolic metal levels. Moreover, despite significant temporal variations, the grand mean MT concentration based on all individual determinations in the digestive gland (reference, n = 54 ; transplants, n = 50 ) was significantly higher in mussels from the metal-rich site. On the other hand, gill MT concentrations did not reflect metal contamination as reliably.

Physiological attributes of the lichen Cladonia pleurota in heavy metal-rich and control sites near Sudbury (Ont., Canada)

The recovery of lichen communities on metal-rich historical ore-roasting beds west of Sudbury has been slow, and our objective was to locate and measure metals in Cladonia pleurota, the most frequently encountered roast bed lichen species. Particulates incorporated into the thallus on or near the roast bed contained high Fe, Al, Cu and Ni, and inductively coupled plasma-atomic emission spectroscopy showed lower concentrations of heavy metals in the control site 60 km upwind than in the roast bed or an immediately adjacent forest. Wavelength-dispersive X-ray spectrometry indicated potentially toxic levels of Cu, Ni, Fe and Al in both the mycobiont and photobiont in the roast bed. The physiology of roast bed lichens was consistent with damage found in metal-treated photobionts in culture: lower concentrations of chlorophyll a, chlorophyll b and total carotenoids on or near the roast bed than in the control site. In addition chlorophyll a on the roast bed was more subject to phaeophytinization and the yield of photosystem II, as measured by F v/ F m, was significantly less in both of the metal-rich sites than in the control. Thin-layer densitometry and UV spectrophotometry showed no significant difference in the amount of usnic acid between metal-rich and control sites, but heavy metals were associated with crystals of usnic acid, possibly forming complexes.

Accumulation and soluble binding of cadmium, copper, and zinc in the polychaete Hediste diversicolor from coastal sites with different trace metal bioavailabilities.

Bioaccumulation of cadmium, copper, and zinc was examined in common ragworms Hediste diversicolor from control (Bay of Somme, Blackwater) and metal-rich (Seine estuary, Boulogne harbor, Restronguet Creek) sites in France and the United Kingdom. The degree of exposure in the field was assessed by considering both total concentrations in superficial sediment and the quantities of metals which may be released in vitro at different pH levels. Among the three contaminated sites, release of the three metals was not detectable in Boulogne harbor, in correlation with limited enhancement of the metal concentrations in the common ragworms from this site. Even at those sites where zinc could be released in vitro from the sediment, zinc concentrations were not enhanced in common ragworms, in agreement with previous findings indicating that the body content of this metal is regulated in H. diversicolor. At all the studied sites, bioaccumulated zinc was mainly in cytosolic form. The distribution of cadmium and copper varied according to the origin of the common rag-worms, the insoluble fraction increasing with the degree of contamination (cadmium in the Restronguet Creek, copper in the Seine estuary, and even more in Restronguet Creek). In the cytosolic fraction, metals were partly linked to cytosolic heat-stable thiolic compounds (CHSTC) with molecular masses (5-6 kDa and about 12 kDa) consistent with metallothionein-like proteins (MTLP). Metal-binding to MTLP varied with the degree of contamination and with the metal studied. In contrast to many invertebrates, the presence of metal-binding CHSTC (MM about 2 kDa) other than MTLP seems to be a peculiar feature of H. diversicolor.

Some methodological aspects of metallothionein evaluation

The specificity of the methods used for metallothioneins (MTs) determination in both field and laboratory studies is crucial to a relevant interpretation of the results. The technique applied in the present study is commonly used, but several potential problems may limit its validity: (i) the stability of the metal–SH links during heating and the possibility of metal exchanges between MTs and others compounds; (ii) the presence of heat-stable thiol compounds with high molecular weight or very low molecular weight, which may subsist in the supernatant and interfere during global analysis of MTs; (iii) the subsistence of metals not bound to MT in the supernatant after heating; and (iv) the impact of reducing agents such as mercaptoethanol on the metal-binding ligands. Our investigations were conducted mainly on oysters ( Crassostrea gigas) and polychaetes ( Hediste/Nereis diversicolor) sampled, respectively, in two French metal-rich sites, the Gironde estuary and Boulogne harbour. This study, which allowed us to clarify most of the potential problems noted above, indicates the importance of dealing with methodological difficulties.

Use of metallothionein in gills from oysters (Crassostrea gigas) as a biomarker: seasonal and intersite fluctuations

The use of oyster gills for the analytical determination of metallothionein (MT) concentration as a biomarker of metal exposure was investigated. Temporal variations in MT and metal concentrations (which can interfere with inter-site differences) were examined over a 7 month period (from spring to autumn) in Japanese oysters from a clean site (Bay of Bourgneuf, France) and a metal-rich site (Gironde estuary, France) as well as in individuals translocated from the clean to the contaminated area. The ratio between the annual average of MT concentrations in specimens from the clean and the metal-rich sites was 1.3. During the last 3 months of the experiment, significant differences were no longer registered between transplants and residents from the Gironde estuary. Metals concentrations in oyster gills differed consistently between the clean and the metal-rich sites (annual average ratios of 1.5, 2.7 and 9.8, respectively, for zinc, copper and cadmium) and a fast increase in metal concentrations (over a few months) was observed in transplants, mainly for cadmium. MT and soluble metal concentrations were found to be positively and significantly correlated over the period of the study. This relationship is a positive argument for a possible use of gill MT concentration as a biomarker of metal pollution in contrast to previous findings on the digestive gland, there being a smaller amount of seasonal variability in the weight of oyster gills.