Heavy metal pollution affects consumption and reproduction of the landsnail Cepaea nemoralis fed on naturally polluted Urtica dioica leaves

Co-exposure of polystyrene microplastics influence cadmium trophic transfer along the "lettuce-snail" food chain: Focus on leaf age and the chemical fractionations of Cd in lettuce

Cadmium (Cd) and polystyrene microplastics (PS) co-contamination always occurs in environment; however, the trophic transfer of Cd and PS is still poorly understood. A hydroponic experiment was conducted to investigate the behavior of Cd in lettuce, together with the root or foliar exposure of different sized PS. Accumulation and chemical form distributions of Cd in leaves were distinguished into young and mature leaves. Subsequently, a 14-day snail feeding experiment was performed. Data showed that Cd accumulation in roots, rather than in leaves, are significantly affected by PS coexistence. However, mature leaves had a higher Cd content than young leaves under the root exposure of PS, while a reverse effect was observed in the foliar exposure. There existed a positive correlation between the food-chain transfer associated Cd (CdFi+Fii+Fiii) in mature leaves and Cd content in snail soft tissue (r = 0.705, p < 0.001), but not in young leaves. Though no bio-amplification of Cd in food chain was observed, an increase of Cd transfer factor (TF) from lettuce to snail was noted in the root exposure of 5 μm PS and the foliar exposure of 0.2 μm PS. Moreover, we observed a highest increase rate of 36.8 % in TF values from lettuce to snail viscera, and a chronic inflammatory response in snail stomach tissue. Therefore, more attentions should be paid to study the ecological risks of heavy metals and microplastics co-contamination in environment.

Level of oxidative stress for the land snail Cepaea nemoralis from aged and bioremediated soil contaminated with petroleum products

Here, we investigated whether the widely distributed snail Cepaea nemoralis could be used as a suitable sentinel animal for assessing the effects of soil contaminants-petroleum oil derivatives-after years of soil ageing and treatment with a bacterial formulation. Oxidative stress was assessed in the foot and hepatopancreas of C. nemoralis L. exposed to soil contaminated with unleaded petrol, spent engine oil or diesel oil and bioremediated with a bacterial formulation (soil was used 2 years after contamination and bioremediation process). We measured total antioxidant capacity, catalase and glutathione transferase activity and concentrations of superoxide anions, hydrogen peroxide and protein carbonyls in the foot and hepatopancreas of snails after 2 and 4 weeks of treatment. The studied antioxidant responses appeared largely to be tissue and remediation process specific, while the concentrations of superoxide anions, hydrogen peroxide and protein carbonyls depended on time of exposure, tissue type and the type of contaminants, but mostly not on the remediation process. Generally, changes in the concentrations of superoxide anions, hydrogen peroxide and protein carbonyls in the hepatopancreas of snails seemed to be a suitable measure to assess the risk of animals exposed to soil contaminated with petroleum substances and used after many years of ageing and treatment with a microbial formulation.

Bio-accumulation effects of heavy metals Pb, Zn and Cd on Procecidochares utilis parasitism to Eupatorium adenophorum at Suzu metal mines, Yunnan

Procecidochares utilis is an obligatory parasitic insect to Eupatorium adenophorum. Both organisms have been spread to some metal mines areas. The objective of this study is to comprehend the trend of heavy metals transfer and the process of their bio-accumulation in the soil-E. adenophorum-P. utilis system and particularly their impact on the parasitic effect of P. utilis to E. adenophorum to reflect the impact of heavy metals on obligate parasitic insect and its host. Therefore, a detailed investigation was carried out at the Suzu Lead–Zinc Mine in Yunnan Province using the concentric circle's method. The results showed that the parasitic rate of P. utilis to a single plant and branch is positively correlated with distance. The metals content of the soil in E. adenophorum and P. utilis, decreased dramatically with an increase in distance away from the center of the mining area. From which is cleared that these metals could enter to E. adenophorum and P. utilis through the soil-E. adenophorum-P. utilis system which likely to affect its parasitic activities. In addition, the parasitic rate is impacted by per Zn content greatly, and the parasitic rate per plant is affected by Cd content enormously. This work could provide important basis of data for further understanding and clarifying the effects of bioaccumulation and heavy metals pollution on various aspects of the food chain. Simultaneously, it could clarify and simplify whether heavy metal contamination affects the parasitic behaviour of some obligatory parasitic insects.

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Concentric circles method was used to assess heavy metals accumulation.

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Heavy metals pollution in mining area reduced the amount of Procecidochares utilis.

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The content of heavy metals uptrend alongside drawing closer to mine center.

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The parasitic rate is positively correlated with the distance from mine center.

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Metals bioaccumulation lowered parasitic effect of P. utilis on Crofton weed.

Toxicity and accumulation of lead and cadmium in the land snail, Archachatina papyracea, in a tropical Alfisol from Southwestern Nigeria

Snails are an important link in the transfer of contaminants, especially metals in the food chain. Yet, few studies have examined the toxicity and accumulation of metals in snails in the tropics. This study assessed the toxicity and accumulation of two non-essential metals (cadmium and lead) to the tropical snail Archachatina papyracea. Specimens of the snail A. papyracea were exposed in a loamy soil collected from Ile-Ife, Nigeria and spiked with varying concentrations of Cd and Pb over 28 days. Survival and weight change of snails were monitored weekly, while tissue accumulation was assessed at the end of the 28-day period. Survival was a more sensitive endpoint than the weight change of snails. The Cd median lethal concentration (LC50) value was 93 ± 4.4 mg/kg, while the median effect concentration (EC50) for snail weight change was 131 ± 41 mg/kg. For Pb, LC50 value was 1121 ± 457 mg/kg, while the EC50 value for weight change was higher at 4541 ± 1180 mg/kg. Therefore, Cd was a factor of about 10 to 30 × more toxic than Pb, consistent with findings on the relative toxicity of Cd and Pb to other soil organisms, including earthworms, springtails, and mites. Although not included initially as an endpoint, egg production in the snails decreased with increasing Cd and Pb concentrations in the substrate. Metal analysis of the foot and visceral mass of surviving snails showed progressive accumulation of Cd and Pb as concentration increased, showing the tendency to use body residue of A. papyracea as an indicator of metal pollution. It further suggests the role of this snail species in above-ground metal transfer in the food chain and highlights the potential danger for human consumption.

Physiological and behavioral responses of land molluscs as biomarkers for pollution impact assessment: A review

Environmental pollution caused by human activities is a global public health concern. This review discusses the impact of different types of pollutants such as pesticides, metals, nanoparticles and others on land molluscs. These molluscs are of great interest as good model organisms for studying biomarker responses in ecotoxicological monitoring programs. Several biomarkers are utilized to characterize and quantify the exposure and harmful impacts of various pollutants. In this review, we have identified physiological and behavioral endpoints (feeding, growth, avoidance, mucus secretion, locomotion and reproductive behavior) for the diagnosis of environmental pollution. The present review displays that all types of pollutants can disturb physiological and behavioral endpoints of gastropods, and these impacts depend on the matrix, exposure time and route as well as the type and concentration of the pollutants in the environment. We have also confirmed that terrestrial gastropods particularly snails as sentinel species could be used as potential bioindicator organisms for environmental quality assessment and thus for predicting potential hazards to human health.

Population- and sex-specific sensitivity of the marine amphipod Allorchestes compressa to metal exposure

The sensitivity to contaminants of natural populations varies greatly depending on their historical exposure and on the sex of the individual. These factors result in great uncertainty in ecotoxicological risk assessments and challenge the protection of marine biodiversity. This study investigated the role of background pollution in the environment in shaping the sensitivity of males and females of the common marine amphipod Allorchestes compressa to the common trace marine pollutant, copper (Cu). Female and male amphipods were collected from two sites: Geelong (the polluted site) and Clifton Springs (the clean site). Amphipods were exposed to Cu treatments of 0, 50, 100, and 250 μg/L for 10 days, followed by a 10-day recovery period. Cu-exposed males from Geelong showed a reduction in feeding rate at a higher Cu concentration than males from Clifton Springs, suggesting that they have a higher tolerance to Cu than males from Clifton Springs. This can be explained by their higher base level of metallothioneins (MTs) and glutathione-S-transferase (GST), the key physiological responses for detoxification and defence against damages from Cu toxicity. Males showed a higher tolerance to Cu than females. This pattern was similar in both populations, which may be associated with a higher level of GST. During the recovery period, only males from Geelong fully recovered to the control level. Our results emphasize the importance of considering population- and sex-specific sensitivity of invertebrates to contaminants in ecotoxicological risk assessments.

Responsiveness of metallothionein and hemocyanin genes to cadmium and copper exposure in the garden snail Cornu aspersum

Terrestrial gastropods express metal-selective metallothioneins (MTs) by which they handle metal ions such as Zn²⁺ , Cd²⁺ , and Cu⁺ /Cu²⁺ through separate metabolic pathways. At the same time, they depend on the availability of sufficient amounts of Cu as an essential constituent of their respiratory protein, hemocyanin (Hc). It was, therefore, suggested that in snails Cu-dependent MT and Hc pathways might be metabolically connected. In fact, the Cu-specific snail MT (CuMT) is exclusively expressed in rhogocytes, a particular molluscan cell type present in the hemocoel and connective tissues. Snail rhogocytes are also the sites of Hc synthesis. In the present study, possible interactions between the metal-regulatory and detoxifying activity of MTs and the Cu demand of Hc isoforms was explored in the edible snail Cornu aspersum, one of the most common European helicid land snails. This species possesses CdMT and CuMT isoforms involved in metal-selective physiological tasks. In addition, C. aspersum expresses three different Hc isoforms (CaH ɑD, CaH ɑN, CaH β). We have examined the effect of Cd²⁺ and Cu²⁺ exposure on metal accumulation in the midgut gland and mantle of C. aspersum, testing the impact of these metals on transcriptional upregulation of CdMT, CuMT, and the three Hc genes in the two organs. We found that the CuMT and CaH ɑD genes exhibit an organ-specific transcriptional upregulation in the midgut gland of Cu-exposed snails. These results are discussed in view of possible interrelationships between the metal-selective activity of snail MT isoforms and the synthesis and metabolism of Hc isoforms.

Cadmium Uptake, MT Gene Activation and Structure of Large-Sized Multi-Domain Metallothioneins in the Terrestrial Door Snail Alinda biplicata (Gastropoda, Clausiliidae)

Terrestrial snails (Gastropoda) possess Cd-selective metallothioneins (CdMTs) that inactivate Cd²⁺ with high affinity. Most of these MTs are small Cysteine-rich proteins that bind 6 Cd²⁺ equivalents within two distinct metal-binding domains, with a binding stoichiometry of 3 Cd²⁺ ions per domain. Recently, unusually large, so-called multi-domain MTs (md-MTs) were discovered in the terrestrial door snail Alinda biplicata (A.b.). The aim of this study is to evaluate the ability of A.b. to cope with Cd stress and the potential involvement of md-MTs in its detoxification. Snails were exposed to increasing Cd concentrations, and Cd-tissue concentrations were quantified. The gene structure of two md-MTs (9md-MT and 10md-MT) was characterized, and the impact of Cd exposure on MT gene transcription was quantified via qRT PCR. A.b. efficiently accumulates Cd at moderately elevated concentrations in the feed, but avoids food uptake at excessively high Cd levels. The structure and expression of the long md-MT genes of A.b. were characterized. Although both genes are intronless, they are still transcribed, being significantly upregulated upon Cd exposure. Overall, our results contribute new knowledge regarding the metal handling of Alinda biplicata in particular, and the potential role of md-MTs in Cd detoxification of terrestrial snails, in general.

Cadmium bioaccumulation and antioxidant enzyme activity in hepatopancreas, kidney, and stomach of invasive apple snail Pomacea canaliculata

The acute toxicity of Cd was tested, and metal bioaccumulation in tissue was determined for the alien invasive species Pomacea canaliculata and its native competitor Sinotaia quadrata under experimental conditions. The invasive species was more tolerant to Cd toxicity than native species, for which the LC₅₀ values were 4.26, 2.24, and 1.98 mg/L at exposure times of 48, 72, and 96 h, respectively, approximately three times higher than those of the native snails. The viscera accumulated the highest Cd concentration, followed by the foot and shell in both species. Metal concentrations in the above three tissues of P. canaliculata were much higher than those of S. quadrata, irrespective of Cd dose and exposure time. For P. canaliculata, the highest concentration of metal was further observed in the hepatopancreas (0.64-3.98 mg/g) followed by the kidney (0.067-3.78 mg/g), with lowest levels in the stomach (0.062-1.53 mg/g). Among the five antioxidant enzymes, the most responsive enzymes were CAT, ALP, and GST in the hepatopancreas; CAT, POD, and GST in the kidney; and POD in the stomach of exposed animals. These results, demonstrating a high Cd tolerance, may partly explain the ability of P. canaliculata to displace S. quadrata in Cd-contaminated habitat. The Cd was accumulated mainly in the hepatopancreas and kidney of invasive species, which changed the activity of antioxidant enzymes allowing the animals to cope with the toxicity. Graphical abstract Cadmium bioaccumulation and antioxidant enzyme activity in the invasive Pomacea canaliculata.

Cigarette butts may have low toxicity to soil-dwelling invertebrates: Evidence from a land snail

Cigarette butts are a common form of litter that is often deposited on soil, where toxins from butts may affect soil-dwelling organisms. We examined possible toxicity of cigarette butts to the woodland snail Anguispira alternata using a toxicity study with cigarette butt effluent and a lab-based habitat choice experiment in which snails could feed or rest on areas with different butt densities. No mortality occurred during the 32-day toxicity study, which used six effluent concentrations ranging from 0 to 4butts/l (0 to 0.92butts/kg of soil). Neither food consumption nor snail growth differed among the effluent concentrations. When provided a choice among four habitats with 0 to 4 cigarette butts, snails selected to preferentially rest in the 0-butt habitat and avoided the 4-butt habitat. This distribution pattern was strong during the first wk. but became weaker over time and largely disappeared by the end of the 3-wk experiment. Snails did not discriminate among butt densities when feeding. This is the first toxicity test using cigarette butts on soil-dwelling invertebrates. Declining aversion to cigarette butts over a 3-wk period may indicate declining toxicity of terrestrially deposited butts as they age, but further testing is needed.

Genetic effects in Helix aspersa near a coal plant revealed by the micronucleus test

Coal plants can be a major source of mutagenic pollutants. In this study we used the common land snail Helix aspersa, to detect the mutagenic effect of pollution from a coal plant in central Italy applying the micronucleus test (MN) on snail's haemocytes and evaluating trace elements concentration (As Cd, Pb, Hg, and Zn) in soil and snails. Snails from a biological farm were exposed for 13 days in five locations at different distances from the plant. Wild snails collected in the same locations were also analysed. MN frequency in exposed snails was significantly higher in four locations within 10 km from to the plant, with respect to the control and the farthest location. Comparing the MN frequency between farmed and wild snails, a significantly higher frequency emerged for the exposed snails in all locations except the farthest, likely indicating adaptation or selection of the wild organisms due to chronic exposure to pollutants. In natural snails significantly higher MN frequencies with near the plant emerged as well. Trace elements analysis showed significant correlations between MN frequencies and both Zn and As concentrations in soil, for both exposed and wild snails, and Zn and Pb concentrations in exposed snails. Our results were consistent with those previously obtained when evaluating primary DNA damage in natural snails from the same area and show that the snails near the plant were affected by a permanent cytogenetic damage. Moreover, they confirm the suitability of snails for biomonitoring the presence of pollutants with mutagenic effect.

Indices of stress and immune function in Arctic barnacle goslings (Branta leucopsis) were impacted by social isolation but not a contaminated grazing environment

In many areas around the Arctic remains and spoil heaps of old mines can be found, which have been abandoned after their heydays. Runoff from tailings of these abandoned mines can directly contaminate the local environment with elevated concentrations of trace metals. Few studies have investigated the possible negative effects of contaminants on Arctic terrestrial animals that use these areas. Trace metals can accumulate in animals and this accumulation has been linked to negative effects on fitness. Both, the hypothalamus-pituitary-adrenal (HPA) axis and/or the immune system have been named as possible underlying causes for these observations. Free-living animals are often exposed to multiple stressors simultaneously, however, and this is often not considered in studies on the effects of contaminants on animal physiology. Here, we performed a study on Spitsbergen (Svalbard) taking both potential effects of trace metal contamination and social stress into account. We investigated experimentally effects of exposure to contaminants from a historic coal mine area on plasma corticosterone levels and on four innate immune parameters (haemolysis, haemagglutination, haptoglobin-like activity and nitric oxide) before and after social isolation in human-raised barnacle goslings (Branta leucopsis). Baseline corticosterone and immune parameters were not affected by mine-exposure. After social isolation, mine goslings tended to show decreased haemagglutination in comparison with control goslings, but we detected no difference in the other measures. Social isolation increased corticosterone and decreased haptoglobin-like activity in all goslings. Immunology and corticosterone levels of barnacle goslings thus seem unaffected, at least on the short term, by Arctic coal mining contamination.

Changes in fatty acid metabolism induced by varied micro-supplementation with zinc in snails Helix pomatia (Gastropoda Pulmonata)

We analyzed the changes in the profile of fatty acids (FA) in the foot tissues and hepatopancreas (HP) of snails Helix pomatia exposed to five microdoses of zinc (0.1, 0.25, 0.5, 0.75, or 1mg/l) administered in the form of a pure salt solution and in the form of EDTA and lysine chelates. Selection from a pool of 56 fatty acids analyzed in snail tissues yielded a set of 12 biomarker acids undergoing significant changes in contact with toxic substances. The selection criteria included the greatest percentage among the FA profile and their significant role in physiological processes. The proposed palette of acids of the biomarker FAs comprised C16:0; C18:0; C23:0; C18:1 n-9; C20:1 n-9; C18:2 n-6; C18:3 n-3; C20:2; C20:4 n-6; C20:5 n-3; C22:4 n-6; and C22:5 n-3, and saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs), determined separately in the foot tissues and hepatopancreas. The significant (p=0.01) influence of the dose as well as the source of the zinc on its' concentration in the tissues and on changes in the fatty acid profiles. Among the three zinc forms administered to the snails, the highest bioaccumulation of zinc in both tissues was noted in the group receiving the Zn-EDTA chelate. The content of PUFAs increased as the supplementation with zinc increased up to 0.75mg/l, but at 1mg/l, the share of these FAs began to decrease. This trend was observed in both analyzed tissue types - foot and hepatopancreas. The dose of 1mg Zn/l might be considered as a threshold dose above which the saturation of FAs increases. The results proved that determination of FA profile in snails can be used in ecotoxicological research as a reliable test of the effect of trace doses of stressors. The micro-supplementation of the mollusks diet with zinc is an example of a non-routine approach to issues connected with both diet and toxicology.

The Shell of the Invasive Bivalve Species Dreissena polymorpha: Biochemical, Elemental and Textural Investigations

The zebra mussel Dreissena polymorpha is a well-established invasive model organism. Although extensively used in environmental sciences, virtually nothing is known of the molecular process of its shell calcification. By describing the microstructure, geochemistry and biochemistry/proteomics of the shell, the present study aims at promoting this species as a model organism in biomineralization studies, in order to establish a bridge with ecotoxicology, while sketching evolutionary conclusions. The shell of D. polymorpha exhibits the classical crossed-lamellar/complex crossed lamellar combination found in several heterodont bivalves, in addition to an external thin layer, the characteristics of which differ from what was described in earlier publication. We show that the shell selectively concentrates some heavy metals, in particular uranium, which predisposes D. polymorpha to local bioremediation of this pollutant. We establish the biochemical signature of the shell matrix, demonstrating that it interacts with the in vitro precipitation of calcium carbonate and inhibits calcium carbonate crystal formation, but these two properties are not strongly expressed. This matrix, although overall weakly glycosylated, contains a set of putatively calcium-binding proteins and a set of acidic sulphated proteins. 2D-gels reveal more than fifty proteins, twenty of which we identify by MS-MS analysis. We tentatively link the shell protein profile of D. polymorpha and the peculiar recent evolution of this invasive species of Ponto-Caspian origin, which has spread all across Europe in the last three centuries.

Bioaccumulation and tissue distribution of Pb and Cd and growth effects in the green garden snail, Cantareus apertus (Born, 1778), after dietary exposure to the metals alone and in combination

The present study was aimed at determining bioaccumulation and cell and tissue distribution of Pb and Cd in the green garden snail, Cantareus apertus (Born, 1778), exposed to different nominal dietary concentrations of Pb (25, 100 and 2500 mg Pb/kg), Cd (5, 10 and 100 mg Cd/kg) and their combination (25mg Pb+10 mg Cd/kg and 2500 mg Pb+100 mg Cd/kg) for 1 and 8 wk. Pb and Cd were bioaccumulated in the digestive gland in a dose-dependent manner and the degree of effects on growth was related to the level of exposure, though metal-metal interactions were observed after treatment with mixtures of Pb and Cd. The present results are absolutely comparable to those obtained in other terrestrial pulmonates in other regions and therefore they absolutely support that C. apertus is suitable as biomonitor for the assessment of the Pb and Cd levels and their biological effects in soil ecosystems in Northern Africa.

Transfer of heavy metals through terrestrial food webs: a review

Heavy metals are released into the environment by both anthropogenic and natural sources. Highly reactive and often toxic at low concentrations, they may enter soils and groundwater, bioaccumulate in food webs, and adversely affect biota. Heavy metals also may remain in the environment for years, posing long-term risks to life well after point sources of heavy metal pollution have been removed. In this review, we compile studies of the community-level effects of heavy metal pollution, including heavy metal transfer from soils to plants, microbes, invertebrates, and to both small and large mammals (including humans). Many factors contribute to heavy metal accumulation in animals including behavior, physiology, and diet. Biotic effects of heavy metals are often quite different for essential and non-essential heavy metals, and vary depending on the specific metal involved. They also differ for adapted organisms, including metallophyte plants and heavy metal-tolerant insects, which occur in naturally high-metal habitats (such as serpentine soils) and have adaptations that allow them to tolerate exposure to relatively high concentrations of some heavy metals. Some metallophyte plants are hyperaccumulators of certain heavy metals and new technologies using them to clean metal-contaminated soil (phytoextraction) may offer economically attractive solutions to some metal pollution challenges. These new technologies provide incentive to catalog and protect the unique biodiversity of habitats that have naturally high levels of heavy metals.

X-ray microtomography for imaging of developing spiders inside egg cocoons

Embryogenesis is especially sensitive to external factors. The changes in its course are often used as biomarkers of environmental impact. Since spider embryogenesis takes place inside cocoons, it is crucial to find a reliable tool to analyze this developmental phase with no intrusion into the cocoons. The aim of this study was to verify the efficacy of X-ray microtomography for non-invasive analysis of embryonic morphology and egg quantity in the cocoons of Xerolycosa nemoralis and Agelena labyrinthica from polluted and reference sites. X-ray microtomography slice images as well as 3D images and animations obtained from digital visualization of those slides were used to study the morphology of embryos and egg arrangement in the cocoons. Any disorders in embryogenesis or malformation of embryos in relation to site of origin have not been found, but inside an egg cocoon of X. nemoralis from the polluted site embryos differing form each other by one developmental stage were identified. Egg calculation revealed a K- reproductive strategy of X. nemoralis from polluted sites. Finally, future prospects and benefits, and weaknessess of this method for the study of spider cocoons have presented.

Predicting As, Cd, Cu, Pb and Zn levels in grasses (Agrostis sp. and Poa sp.) and stinging nettle (Urtica dioica) applying soil-plant transfer models

The aim of this study was to derive regression-based soil-plant models to predict and compare metal(loid) (i.e. As, Cd, Cu, Pb and Zn) concentrations in plants (grass Agrostis sp./Poa sp. and nettle Urtica dioica L.) among sites with a wide range of metal pollution and a wide variation in soil properties. Regression models were based on the pseudo total (aqua-regia) and exchangeable (0.01 M CaCl2) soil metal concentrations. Plant metal concentrations were best explained by the pseudo total soil metal concentrations in combination with soil properties. The most important soil property that influenced U. dioica metal concentrations was the clay content, while for grass organic matter (OM) and pH affected the As (OM) and Cu and Zn (pH). In this study multiple linear regression models proved functional in predicting metal accumulation in plants on a regional scale. With the proposed models based on the pseudo total metal concentration, the percentage of variation explained for the metals As, Cd, Cu, Pb and Zn were 0.56%, 0.47%, 0.59%, 0.61%, 0.30% in nettle and 0.46%, 0.38%, 0.27%, 0.50%, 0.28% in grass.

Use of the land snail Helix aspersa for monitoring heavy metal soil contamination in Northeast Algeria

The objective of this study was to investigate the impact of anthropogenic activities on soil quality using the land snail Helix aspersa as a bioindicator. Soil samples and snails were collected from several sites in Northeast Algeria during the summer and winter of 2010. All of the sites were chosen due to their proximity to industrial factories-a potential source of soil pollution via heavy metal contamination. The concentration of heavy metals (Pb, Cd, Mn, and Fe) in soil samples was analyzed using atomic absorption spectrophotometry. Activity levels of glutathione S-transferase (GST) and acetylcholinesterase (AChE), indicators of oxidative stress and neurotoxicity, respectively, were measured in snails collected from each site. GST and AChE activity were found to vary between sites and by season. The highest levels of GST activity were registered during the summer at sites closest to potential sources of pollution. AChE activity levels also peaked during the summer with the highest values recorded at the site in El Hadjar. These increased levels of bioindicative stress response correlated with increasing metal concentration in soil samples collected at each site.

Effects of subtle pollution at different levels of biological organisation on species-rich assemblages

We investigated effects of subtle nutrient enrichment and metal pollution on different levels of biological organization (i.e. whole assemblage, population and individual) of species-rich assemblages. We used rockpools as model system, applying a multi-factorial sampling design to test hypotheses on differences between disturbed and reference locations. Results indicated that disturbed and reference locations supported similar assemblages, as well as individual fitness-related life-traits were ineffective to discriminate between the two conditions. In contrast, assemblages responded to pollution through a reduction of the abundance of sensitive species and a proliferation of tolerant species, although these alterations were detectable only once the influence of dominant taxa was down-weighed by data transformation. Present findings suggest that, contrarily to individual level variables, assemblage structure after data transformation and patterns of distribution and abundance of differently sensitive taxa would be a powerful tool to detect effects of subtle pollution on species-rich assemblages.

Role of plants in metal cycling in a tidal wetland: implications for phytoremidiation

Accumulation of 8 metals and the semimetal As in 29 plant species was quantified in a restored tidal wetland on a contaminated site. Transfer coefficients between sediment and aboveground plant tissues were lower than in many other systems; from 0.013 (Pb) to 0.189 (Mn). A minor fraction of the sediment metal pool cycled through the aboveground vegetation (≤0.02%). However, during the four years of this study, species composition changed, and plant biomass as well as the metal pool in the vegetation increased (≤0.12%). Succession to either a willow dominated brushwood or a monospecific reed stand can further enlarge this pool (2.5%). Since the amount of trace metals in the wetland soil or in suspended solids deposited during tidal flooding is some orders of magnitude larger than the vegetation pool, phytoextraction is not applicable. The growth of plant species with low accumulation in aboveground tissues, e.g. Scirpus maritimus or Typha latifolia, may be preferred since this might result in lower toxic metal distribution to the wider environment.

The reproductive potential of the spiders Agelena labyrinthica and Xerolycosa nemoralis from areas contaminated with metals

Spiders successfully colonize industrially contaminated environments and maintain relatively stable populations. The aim of this study was to explain the reproductive strategies of two spider species, Xerolycosa nemoralis (an actively hunting, sit-and-pursue predator) and Agelena labyrinthica (a web-building, sit-and-wait predator), between contaminated and uncontaminated sites. Spiders were collected from a reference site (Pilica) and two contaminated sites (Olkusz and Welnowiec). The amount of energy allocated to the eggs and the number of eggs and hatchlings as well as the hatching success were compared. Wolf spiders from the contaminated sites produced fewer but relatively energy-rich eggs, whereas web-building spiders invested their energy in the production of a higher number of less energy-rich eggs. The comparisons of the hatching percentages suggested that in the contaminated habitats, X. nemoralis achieve a hatching success similar to or higher than that of the reference population at Pilica. A. labyrinthica in the contaminated sites invested a larger amount of energy in eggs than at the reference site, but the hatching success found for this species in the contaminated areas was lower than that found at the reference site.

Investigations of responses to metal pollution in land snail populations (Cantareus aspersus and Cepaea nemoralis) from a smelter-impacted area

A cross-transplantation field experiment was performed to investigate about possible adaptation/acclimatization to metal pollution in common garden snail Cantareus aspersus (ex-Helix aspersa) and brown-lipped grove snail Cepaea nemoralis populations. Adults were collected from an area surrounding a former smelter (ME), highly polluted by trace metals (TMs) for decades, and from an unpolluted site (BE). Subadults of first generation (F1) were exposed in microcosms in a 28-day kinetic study. Four exposure sites were chosen around the smelter along a soil pollution gradient (vegetation and soil otherwise comparable). Bioaccumulation in snail soft tissues globally increased with soil contamination, with Cd, Pb and Zn concentrations reaching 271, 187, 5527 μg g(-1), respectively. Accumulation kinetic patterns were similar between snail species but C. nemoralis showed greater TM levels than C. aspersus. Some inter-population differences were revealed in TM accumulation (bioaccumulation factors, accumulation kinetics) but did not suggest consistent adaptive responses. We did not detect negative effects of TM exposure on snail condition (body weight, shell size, shell weight). ME C. aspersus snails produced heavier shells than BE snails under exposure to TMs at the highest level, suggesting an adaptive response. The protocol used in this study, however, did not allow unambiguously distinguishing whether this response was due to genetic adaptation or to maternal effects. Abnormal but reversible shell development of adult ME C. nemoralis suggested physiological acclimatization. Differences in responses to TMs between populations are observed for conchological parameters, not for bioaccumulation, with different strategies according to the species (acclimatization or adaptation/maternal effects).

Comprehensive biological effects of a complex field poly-metallic pollution gradient on the New Zealand mudsnail Potamopyrgus antipodarum (Gray)

The Lot River is known to be contaminated by metals, mainly cadmium and zinc, due to a former Zn ore treatment plant in the watershed of the Riou-Mort, a tributary of the Lot River. Many studies have been performed to characterize contamination, but few have assessed its consequences on the biological responses of organisms along the gradient. We exposed adult and juvenile New Zealand freshwater mudsnails Potamopyrgus antipodarum at several sites along the gradient of metal contamination for 28 days. Biological responses were monitored at different levels: individual (survival, growth and fecundity), tissue and biochemical (energy status and vertebrate-like sex steroid levels) to better understand the toxicity mechanisms involved. Accumulation of Cd and Zn was high during exposure. Most of the biological effects observed could be linked to this contamination and were concentration-dependent. Histological lesions of the digestive gland were observed, with hypertrophy of calcium cells and vacuolization of digestive cells. Such effects are likely to explain the decrease of energy status (triglycerides and proteins), juvenile growth and adult fecundity observed at the most polluted site. However the magnitude of the fall in fecundity cannot be attributed only to these tissular effects, indicating another mode of action of Cd or possible confounding factors. Steroid accumulation in snails indicated only organic pollution. Histopathological effects proved the most sensitive endpoint to metal (Cd and Zn) contamination.

Responses of abalone Haliotis diversicolor to sublethal exposure of waterborne and dietary silver and cadmium

In this study, we examined the chronic waterborne and dietary exposure of silver (Ag) and cadmium (Cd) to the abalone Haliotis diversicolor using various endpoints such as growth and feeding rates, metal body burden, subcellular distribution, and metallothionein (MT) concentration over a period of 7 weeks of exposure. The growth and feeding rates of abalones were inhibited during the early stage of exposure to different extents, but then recovered to nearly the control levels. A large portion of Ag was redistributed to organelles and metal-rich granules from the cellular debris fraction, whereas cellular debris and metallothionein-like protein were the dominant pools for the storage of Cd, which remained comparable during the exposure period. The MT concentrations were significantly elevated (in a dose-dependent manner) within the first 2 weeks of exposure, after which the MT concentrations started to decrease. All these results implied that abalones respond rapidly to metal exposure, but apparently developed subsequent acclimation.

Individual, population and community level effects of subtle anthropogenic contamination in estuarine meiobenthos

The study presented here searched for the level of taxonomic resolution required to detect the effects of low-level chronic pollution on estuarine meiobenthic communities. Meiofauna from two sites, with special attention to harpacticoid copepods, was analysed at different taxonomic levels of aggregation using uni- and multivariate methods. Adaptation processes that could buffer biodiversity disruptions were also considered through the analysis of fitness-related and tolerance traits in the harpacticoid copepod Paronychocamptus nanus. Results showed that uni- and multivariate analyses could be inadequate when assessing subtle anthropogenic contamination. Instead, the assessment of inter-population differences in tolerance to the main source of stress rises as a required procedure if potential effects of this type of contamination are being investigated. Specifically, a 96 h acute toxicity test performed with populations from the affected site appears as a faster and reliable general tool to assess impacts of low-level chronic pollution in estuaries.

Deposition and solubility of airborne metals to four plant species grown at varying distances from two heavily trafficked roads in London

In urban areas, a highly variable mixture of pollutants is deposited as particulate matter. The concentration and bioavailability of individual pollutants within particles need to be characterised to ascertain the risks to ecological receptors. This study, carried out at two urban parks, measured the deposition and water-solubility of metals to four species common to UK urban areas. Foliar Cd, Cr, Cu, Fe, Ni, Pb and Zn concentrations were elevated in at least one species compared with those from a rural control site. Concentrations were, however, only affected by distance to road in nettle and, to a lesser extent, birch leaves. Greater concentrations of metal were observed in these species compared to cypress and maple possibly due to differences in plant morphology and leaf surfaces. Solubility appeared to be linked to the size fraction and, therefore, origin of the metal with those present predominantly in the coarse fraction exhibiting low solubility.

Effects of lead pollution against juvenile Achatina achatina fed on contaminated artificial diet

We investigated juvenile Achatina achatina snails by feeding graded levels of inorganic lead metal contaminated artificial diet in plastic snaileries in the laboratory. Snails were tolerant of all levels of lead contamination with no mortalities. Results indicated significant (p < 0.05) transfer of lead from diet to snail with high positive (r(2) = 0.98) relationship. Our data suggests that decreased feed intake and growth were found at elevated lead levels. Tissue lead accumulations were lower than dose in artificial diet.

Effects of lead pollution at industrial contaminated sites on sentinel juvenile Achatina achatina

We investigated juvenile Achatina achatina snails exposed as sentinels in plastic cages for 12 weeks to compare lead pollution at dump sites of abandoned battery factory (Niger Delta, Nigeria). Results indicated 0.56, 20.37, 200.42 and 1200.30 microg/g soil lead at control, storage, dried effluent and waste dump sites, respectively. There were significant (p < 0.05) depression in snail growth with increasing level of lead pollution. Snails were tolerant of all levels of lead pollution with no mortalities. This novel approach provides a basis for use of snail data in environmental pollution assessment of industrial sites.

Field effects of pollutants at the community level--experimental challenges and significance of community shifts for ecosystem functioning

In the Stimulation Program System-oriented Ecotoxicological Research (SSEO) three sites in The Netherlands were investigated for field effects of the grey veil of pollutants. At each site several studies were performed in order to arrive at an adequate weight of evidence and to improve causal inference of pollutant effects. This paper contains a synthesis of results of the studies, performed at one of the sites, the Demmerikse polder. This site is characterized by an anthropogenic layer of soil (in old Dutch: 'toemaakdek') on top of the natural peat. Lead, copper and zinc concentrations were elevated, with lead concentrations above a Netherlands environmental quality criterion (Intervention Value) in 66% of the samples. Issues discussed in the paper are: the sampling strategy, selection of maximum gradient and suitable community end-points, both in space and in time. Specific emphasis was given to causal inference of ecological effects of pollutants, related to direct versus indirect effects, functioning of ecosystems, normal operation range and risk assessment. The plausibility of metal effects could be demonstrated on a number of occasions. In the Demmerikse polder changes in the bacterial and nematode communities could be related significantly to metal concentrations and separated from other environmental variables, such as organic matter content and pH.

Do high levels of diffuse and chronic metal pollution in sediments of Rhine and Meuse floodplains affect structure and functioning of terrestrial ecosystems?

This paper (re)considers the question if chronic and diffuse heavy metal pollution (cadmium, copper, lead and zinc) affects the structure and functioning of terrestrial ecosystems of Biesbosch National Park, the floodplain area of rivers Meuse and Rhine. To reach this aim, we integrated the results of three projects on: 1. the origin, transfer and effects of heavy metals in a soil-plant-snail food chain; 2. the impact of bioavailability on effects of heavy metals on the structure and functioning of detritivorous communities; 3. the risk assessment of heavy metals for an herbivorous and a carnivorous small mammal food chain. Metal pollution levels of the Biesbosch floodplain soils are high. The bioavailability of metals in the soils is low, causing low metal levels in plant leaves. Despite this, metal concentrations in soil dwelling detritivores and in land snails at polluted locations are elevated in comparison to animals from 'non-polluted' reference sites. However, no adverse effects on ecosystem structure (species richness, density, biomass) and functioning (litter decomposition, leaf consumption, reproduction) have been found. Sediment metal pollution may pose a risk to the carnivorous small mammal food chain, in which earthworms with elevated metal concentrations are eaten by the common shrew. Additional measurements near an active metal smelter, however, show reduced leaf consumption rates and reduced reproduction by terrestrial snails, reflecting elevated metal bioavailability at this site. Since future management may also comprise reintroduction of tidal action in the Biesbosch area, changes in metal bioavailability, and as a consequence future ecosystem effects, cannot be excluded.

Effects of cadmium on cellular protein and glutathione synthesis and expression of stress proteins in eastern oysters, Crassostrea virginica Gmelin

Cadmium (Cd) is an important toxicant in estuarine and coastal environments that can strongly affect energy balance of aquatic organisms by increasing the organism's basal energy demand and reducing its aerobic capacity. Mechanisms of cadmium-induced increase in basal metabolic costs are not well understood and may involve elevated detoxification costs due to the synthesis of cellular protective proteins and glutathione. We studied the short-term effects of cadmium exposure (4 h) on protein and glutathione (GSH) synthesis and expression of stress proteins (heat shock proteins HSP60, HSP70 and HSP90) and metallothioneins in isolated gill and hepatopancreas cells of the eastern oyster, Crassostrea virginica. Our study showed that exposure to cadmium resulted in a dose-dependent increase in the rate of protein synthesis in oyster cells, which reached 150% of the control at the highest tested Cd level (2000 micromol l(-1)). GSH synthesis was significantly inhibited by the highest Cd concentrations, especially in hepatopancreas, which resulted in a slight but significant decrease in the total GSH concentrations. Elevated protein synthesis was associated with the increased expression of metallothioneins and heat shock proteins. Interestingly, stress protein response differed considerably between gill and hepatopancreas cells. In hepatopancreas, expression of metallothionein mRNA (measured by real-time PCR) increased 2-8-fold in response to Cd exposure, whereas no significant increase in metallothionein expression was found in Cd-exposed gill cells. By contrast, HSP60 and HSP70 protein levels increased significantly in Cd-exposed gill cells (by 1.5-2-fold) but not in hepatopancreas. No change in HSP90 expression was detected in response to Cd exposure in oyster cells. These data indicate that metallothionein expression may provide sufficient protection against Cd-induced damage to intracellular proteins in hepatopancreas, alleviating the need for overexpression of molecular chaperones. By contrast, Cd detoxification mechanisms such as inducible metallothioneins and GSH appear to be insufficient to fully prevent protein damage in gill cells, thus necessitating induction of HSPs as a secondary line of cellular defense. Therefore, gills are likely to be among the most Cd-sensitive tissues in oysters, which may have important implications for impaired oxygen uptake contributing to energy misbalance and reduced aerobic scope in Cd-exposed oysters.

Do metal-rich plants deter herbivores? A field test of the defence hypothesis

Some plant species growing on metalliferous soils are able to accumulate heavy metals in their shoots up to very high concentrations, but the selective advantage of this behaviour is still unknown. The most popular hypothesis, that metals protect plants against herbivores, has been tested several times in laboratory conditions, with contradictory results. We carried out the first large-scale test of the defence hypothesis in eight natural populations of the model Zn hyperaccumulator Thlaspi caerulescens J. and C. Presl (Brassicaceae). In two climatic regions (temperate, Belgium-Luxembourg, and Mediterranean, southern France), we worked in metalliferous and in normal, uncontaminated environments, with plants spanning a wide range of Zn concentrations. We also examined the importance of glucosinolates (main secondary metabolites of Brassicaceae) as antiherbivore defences. When exposed to natural herbivore populations, T. caerulescens suffered lower herbivory pressures in metal-enriched soils than in normal soils, both in Belgium-Luxembourg and in southern France. The trapping of gastropods shows an overall lower population density in metalliferous compared to normal environments, which suggests that herbivory pressure from gastropods is lower on metalliferous soils. In addition, foliar concentration of glucosinolates was constitutively lower in all populations from metal-enriched soils, suggesting that these have evolved towards lower investment in organic defences in response to lower herbivory pressure. The Zn concentration of plants had a protective role only for Belgian metallicolous plants when transplanted in normal soils of Luxembourg. These results do not support the hypothesis that Zn plays a key role in the protection of T. caerulescens against enemies. In contrast, glucosinolates appear to be directly involved in the defence of this hyperaccumulator against herbivores.