PB uptake by ecologically dissimilar earthworm (Lumbricidae) species near a lead smelter in south Finland

Impacts of metallic trace elements on an earthworm community in an urban wasteland: Emphasis on the bioaccumulation and genetic characteristics in Lumbricus castaneus

Metallic trace elements (MTEs) soil pollution has become a worldwide concern, particularly regarding its impact on earthworms. Earthworms, which constitute the dominant taxon of soil macrofauna in temperate regions and are crucial ecosystem engineers, are in direct contact with MTEs. The impacts of MTE exposure on earthworms, however, vary by species, with some able to cope with high levels of contamination. We combined different approaches to study the effects of MTEs at different levels of biological organisation of an earthworm community, in a contaminated urban wasteland. Our work is based on field collection of soil and earthworm samples, with a total of 891 adult earthworms from 8 species collected, over 87 quadrats across the study plot. We found that MTE concentrations are highly structured at the plot scale and that some elements, such as Pb, Zn, and Cu, are highly correlated. Comparing species assemblage to MTE concentrations, we found that the juvenile and adult abundances, and community composition, were significantly affected by pollution. Along the pollution gradient, as species richness decreased, Lumbricus castaneus became more dominant. We thus investigated the physiological response of this species to a set of specific elements (Pb, Zn, Cu, and Cd) and studied the impacts of MTE concentrations at the plot scale on its population genetic. These analyses revealed that L. castaneus is able to bioaccumulate high quantities of Cd and Zn, but not of Cu and Pb. The population genetic analysis, based on the genotyping of 175 individuals using 8 microsatellite markers, provided no evidence of the role of the heterogeneity in MTE concentrations as a barrier to gene flow. The multidisciplinary approach we used enabled us to reveal the comparatively high tolerance of L. castaneus to MTE concentrations, suggesting that this is a promising model to study the molecular bases of MTE tolerance.

Lead and PAHs contamination of an old shooting range: A case study with a holistic approach

Soil pollution at firing ranges is an issue of growing importance, due to the accumulation in soils of contaminants derived from ammunition and clay targets. The concentration of Pb and PAHs was determined in five soils of an abandoned shooting range in Galicia (northwest Spain), and an ecotoxicological characterization was performed in order to obtain an assessment of risks. Therefore, the retention capacity of soils was assessed using test organisms of different trophic levels, and the role of soils as habitat for soil invertebrates was assessed by reproduction tests and bioaccumulation assays with earthworms. The sum of 15 PAHs ranged between 38 and 360mgkg^-1, which exceed, together with Pb (160-720mgkg^-1), the Galician generic reference value for urban and sporting field soils. Bioaccumulation in E. andrei showed contents up to 104,000μgPbkg^-1_dw, and up to 645μgPAHskg^-1_fw. High contents of Pb and PAHs in soil samples and in Eisenia andrei whole body, caused a reduction in the number of juveniles produced, whereas, Vibrio fischeri, Raphidocelis subcapitata and Daphnia magna displayed a slight toxic response to the soil elutriates tested. Therefore, the function of these soils to retain contaminants seemed not compromised, probably due to the high organic matter content and pH values, which are weakly acidic. The habitat function was affected, indicating that soil solution is not the only route of exposure to contaminants to E. andrei. The integration of chemical and ecotoxicological lines of evidence give rise to high risks values, restricting the use of these areas, and pointing for risks to surrounding ecosystems due to possible trophic transferences. The calculation of risks using the chemical and ecotoxicological data, required by Spanish legislation, could be a good approach to communicate with those responsible and/or involved in the management of contaminated sites.

Determining the bioavailability and toxicity of lead contamination to earthworms requires using a combination of physicochemical and biological methods

This study aimed at assessing the bioavailability and toxicity of lead to Eisenia andrei in shooting range soils representing different land uses (forest, grassland, bullet plot). Soils contained 47-2398 mg Pb/kg dry weight (dw), but also had different pH-CaCl2 (3.2-6.8) and organic matter contents (3.8-13%). Therefore artificial soils with different pH and organic matter contents and two natural soils were included as control soils. Earthworms were exposed for 28 days and toxicity and uptake of Pb were related to total, water and 0.01 M CaCl2 extractable and porewater Pb concentrations as well as to soil characteristics. Pb uptake in the earthworms linearly increased with increasing soil concentrations. At >2000 mg Pb/kg dw and pH 3.3-3.5, high earthworm mortality with significant weight loss and complete inhibition of reproduction were recorded. At <1000 mg/kg dw, earthworm reproduction was more related to differences in pH and other soil characteristics than to Pb.

Pollution and its impact on wild animals: a meta-analysis on oxidative stress

Oxidative stress is the unifying feature underlying the toxicity of anthropogenic pollution (e.g., heavy metals, polycyclic aromatic hydrocarbons, and nitrogen-oxides) and the ultimate culprit in the development of many diseases. Yet, there has been no attempt to summarize the published data on wild terrestrial animals to reveal general trends regarding the effects of pollution on oxidative stress. The main findings of this meta-analysis reveal that, as predicted, there is an overall increase in oxidative stress when exposed to pollution. This is mainly due to a weak overall increase of oxidative damages, although there is some variation across taxa. The reduced form of glutathione (GSH) and its associated enzymes are the most reliable biomarkers. This result is important when choosing biomarkers and when using less-invasive sampling of endangered species, or for longitudinal approaches. To be able to predict future population outcomes, possible treatments, but also evolutionary responses to a changing environment, a greater integration of biotic factors such as temperature, bioavailability of toxic elements, and species-specific responses are needed.

Uptake kinetics of metals by the earthworm Eisenia fetida exposed to field-contaminated soils

It is well known that earthworms can accumulate metals. However, most accumulation studies focus on Cd-, Cu-, Pb- or Zn-amended soils, additionally few studies consider accumulation kinetics. Here we model the accumulation kinetics of 18 elements by Eisenia fetida, exposed to 8 metal-contaminated and 2 uncontaminated soils. Tissue metal concentration was determined after 3, 7, 14, 21, 28 and 42 days. Metal elimination rate was important in determining time to reach steady-state tissue metal concentration. Uptake flux to elimination rate ratios showed less variation and lower values for essential than for non-essential metals. In theory kinetic rate constants are dependent only on species and metal. Therefore it should be possible to predict steady-state tissue metal concentrations on the basis of very few measurements using the rate constants. However, our experiments show that it is difficult to extrapolate the accumulation kinetic constants derived using one soil to another.

Effect of heavy metal supplementation on local (Allolobophora parva) and exotic (Eisenia fetida) earthworm species: a comparative study

This study compares the effects of different metal concentration on survival, reproduction and total metal accumulation by two different earthworm species, Allolobophora parva and Eisenia fetida. The substrate was spiked with different heavy metals (Cu, Cr, Pb, Zn & Cd) with concentrations varying from 500-2500 mg/kg. Cu resulted in complete mortality at all doses for both species. The accumulation of heavy metals for Eisenia fetida in 45 days was in order of Cr>Cd>Pb>Zn where as for Allolobophora parva was Cd>Cr>Pb>Zn. Allolobophora parva accumulated significantly higher concentrations of heavy metals was found in Allolobophora parva as compared to Eisenia fetida. The percentage uptake for Cr and Pb ranged from 65-26% and 39-16% for Eisenia fetida while it was 83-30% and 70-24% for Allolobophora parva at 500-2500 mg/kg. Zn uptake was similar for both species. In case of Cd, uptake percentage for Eisenia fetida at 500 and 1000 mg/kg for local species it was 73% and 52%. Zn produced at 100% mortality at both 1500 and 2500 mg/kg, Cd produced was 43% and 44%, whereas 100% mortality at the highest concentration studied (2500 mg/kg). A mortality of 56-64% was observed at a concentration of 500-2500 mg/kg concentration of Cr while 57-68% mortality was found at 500-2500 mg/kg concentration of Pb. Cd had the greatest detrimental effect on cocoon production by Eisenia fetida and Allolobophora parva. Overall, it is concluded that local earthworm species especially the native species Allolobophora parva have tremendous potential to take up heavy metals from contaminated media/soils.

Mercury, cadmium and lead concentrations in different ecophysiological groups of earthworms in forest soils

Bioaccumulation of Hg, Cd and Pb by eight ecophysiologically distinct earthworm species was studied in 27 polluted and uncontaminated forest soils. Lowest tissue concentrations of Hg and Cd occurred in epigeic Lumbricus rubellus and highest in endogeic Octolasion cyaneum. Soils dominated by Dendrodrilus rubidus possess a high potential of risk of Pb biomagnification for secondary predators. Bioconcentration factors (soil-earthworm) followed the sequence ranked Cd>Hg>Pb. Ordination plots of redundancy analysis were used to compare HM concentrations in earthworm tissues with soil, leaf litter and root concentrations and with soil pH and CEC. Different ecological categories of earthworms are exposed to Hg, Cd and Pb in the topsoil by atmospheric deposition and accumulate them in their bodies. Species differences in HM concentrations largely reflect differences in food selectivity and niche separation.

Lead bioaccessibility in food web intermediates and the influence on ecological risk characterization

Models simulating gastric conditions of mammalian (eastern cottontail, Sylvilagus floridanus; short-tailed shrew, Blarina brevicauda) and avian (American robin, Turdus migratorius) receptors were used to investigate the proportion of lead (Pb) mobilized into the digestive juices (the bioaccessible fraction) from soil, earthworms, and vegetation collected at a rifle and pistol (RP) range in eastern Ontario, Canada. Pb concentrations averaged 5044 mg kg(-1) in RP range surface soils, 727 mg kg(-1) in earthworm tissue, and 2945 mg kg(-1) in unwashed vegetation. For mammalian gastric models, the bioaccessible fraction of Pb in soils was 66 +/- 22%, in earthworm tissue was 77 +/- 14%, and in unwashed vegetation was 50 +/- 37%. For the avian gastric model, the bioaccessible fraction of Pb in soil was 53 +/- 43% and in earthworm tissue was 73 +/- 13%. The incorporation of soil and food web intermediate bioaccessibility data into standard risk calculations resulted in predicted risk being reduced for all receptors. The inclusion of bioaccessibility during ecological risk assessment affords a more realistic estimate of contaminant exposure, and is a valuable tool for use in contaminated sites management.

A review of studies performed to assess metal uptake by earthworms

Earthworms perform a number of essential functions in soil; the impacts of metals on earthworms are often investigated. In this review we consider the range of earthworm species, types of soil and forms of metal for which metal uptake and accumulation have been studied, the design of these experiments and the quantitative relationships that have been derived to predict earthworm metal body burden. We conclude that there is a need for more studies on earthworm species other than Eisenia fetida in order to apply the large existing database on this earthworm to other, soil dwelling species. To aid comparisons between studies agreement is needed on standard protocols that define exposure and depuration periods and the parameters, such as soil solution composition, soil chemical and physical properties to be measured. It is recommended that more field or terrestrial model ecosystem studies using real contaminated soil rather than metal-amended artificial soils are performed.

Lead bioaccumulation in earthworms, Lumbricus terrestris, from exposure to lead compounds of differing solubility

This study examined the relative effects of soluble and less soluble Pb compounds on Pb accumulation by Lumbricus terrestris. The earthworms were exposed to composted cattle manure contaminated with a range of concentrations of either soluble lead acetate trihydrate (PbAc) (14.5, 72.2, 137, 257, and 603 microg/g) or less soluble lead carbonate (Pb(CO(3))(2)) (5.09, 171, 575, and 710 microg/g). Relative Pb bioaccumulation rates in earthworms from the PbAc and Pb(CO(3))(2) lead carbonate trials were compared over time (0, 20, 40, and 60 days). The two molecular forms of Pb were heavily adsorbed onto the organic matter. Relative soluble Pb concentrations in the manure pore water were very low, at 0.049% and 0.022% of total Pb for PbAc and Pb(CO(3))(2), respectively. There was a significant uptake of lead by earthworms from both the readily soluble and less soluble forms of Pb. Regression surfaces relating organic matter total Pb concentration to exposure time and Pb body burden were compared. For the PbAc trial, the following equation was fitted: Body burden=2.3429+0.0014 x--0.0632 y+0.0008 xy (R(2)=0.8494, p<0.0001). For the Pb(CO(3))(2) trial, the equation was: Body burden=-2.0760--0.0067 x-0.2297 y-0.0038 y(2)+0.0003 xy (R(2)=0.5686, p<0.0001) (for x=organic matter Pb concentration in microg/g and y=time in days). The Pb bioaccumulation resulting from the PbAc exposure was significantly higher than that from Pb(CO(3))(2). Body burdens of earthworms exposed to PbAc were linearly related to exposure time and total Pb concentration. Worms exposed to Pb(CO(3))(2) had non-linear Pb accumulation over time that suggested a decrease in Pb bioavailability with increasing exposure time. The results indicate that L. terrestris feeding on detritus in the upper soil levels can mobilize and accumulate Pb from the principal transformation products of metallic Pb, as at shooting ranges and lead smelter sites.

Genetic variation in the enzyme esterase, bioaccumulation and life history traits in the earthworm Lumbricus rubellus from a metal contaminated area, Avonmouth, England

Earthworms, Lumbricus rubellus, were collected in three successive years, 1997, 1998 and 1999 from 5, 6 and 4 sites, respectively, along a metal gradient near a smelter at Avonmouth, England. In total 271 worms were collected, 47 in 1997, 97 in 1998, and 127 in 1999. The worms were analysed for the enzyme esterase by means of agarose electrophoresis and for internal metal concentration. At one site collected in three successive years, 64 individuals of 66 were heterozygous for the esterase enzyme. The metal concentrations (Cu and Zn) in worms were significantly correlated with the total concentration and the CaCl2 extractable fraction of the metal in the soil. One of the homozygous esterase genotypes was significantly correlated with distance from the smelter, the extractable fraction of metals from soil, and the metal concentration in the worms. The other homozygous genotype was correlated with the CaCl2 extractable Cu and the Cu concentration in the worms. The internal levels of Cd, Cu, and Zn showed a higher classification potential (Discriminant Analysis) for 50 of 127 individuals, collected in 1999, when based on the original habitat of the earthworms than on the esterase genotype. The remaining 77 specimens, representing three sites, were exposed for 30 days in the laboratory to soils from four sites. For the individuals in this transplantation experiment, parameters measured were the esterase phenotype, internal metal concentration (Cd, Cu, and Zn), mortality, wet weight change, cocoon production, and cocoon hatching success. Cocoon production was highest among the worms from the most contaminated area, while worms from the least contaminated area had the highest hatching success. Neither the metal concentrations, in soil or internal, nor the life-history parameters could fully explain the genotypic distribution of esterase along the gradient. The internal concentrations of Cd, Cu and Zn in the worms used for the transplantation experiment showed the highest classification potential (Discriminant Analysis) when the prediction was based on the original habitat of the earthworms. The classification potential was less strong when based on esterase genotype and least on the transplantation conditions. Including life history traits did not enhance the prediction potential.

Immune response of earthworms (Lumbricus terrestris, Eisenia andrei and Aporrectodea tuberculata) following in situ soil exposure to atmospheric deposition from a cement factory

In order to reduce their energy costs, many cement plants use fuel product substitutes (old tyres and used oil). The combustion of these products generates a metal increase (e.g. Cu, Cd, Pb and Zn) in the atmospheric emissions. After their release, these elements are deposited into the environment and could eventually accumulate up to concentrations of concern. At the Saint-Laurent cement factory (Joliette, QC, Canada), maximum deposition of these elements occurs in the direction of prevailing winds (North-East). We evaluated the potential impact of these depositions upon the immune system of three earthworm species (Lumbricus terrestris, Eisenia andrei and Aporrectodea tuberculata) exposed in a natural environment. The exposure sites were 0.5, 1.0, and 2.0 km downwind from the cement factory, along with an upwind reference site. The immune parameters studied were the cell viability and phagocytic potential of the immune cells (coelomocytes). For both L. terrestris and E. andrei, after 7 d exposure, none of the measured parameters showed significant differences among the sites. On the other hand, for the indigenous worm A. tuberculata, in the most exposed zone (at 0.5 km), we observed an increase in cell viability and phagocytic potential. This increase could possibly be attributed to physicochemical effects such as the alkaline pH of the soil, or alternatively, it could result from beneficial effects induced by an increased calcium supply.

What do sentinels stand for?

Sentinel species are biological monitors that accumulate a pollutant in their tissues without significant adverse effects. Primarily used to measure the amount of a pollutant that is biologically available, they may also increase the sensitivity of an analytical procedure or summarise a complex pollution signal. This paper examines the validation of sentinels, referring particularly to the use of invertebrates in monitoring toxic metal pollution in terrestrial ecosystems. Few studies measure the capacity of a sentinel to quantify changes in ambient levels. Definitions of 'bioavailability' also differ between workers and few note that this may be a highly species-specific measure. Validation requires that the temporal and spatial scales over which a sentinel integrates a pollution signal are known. The sentinel has to be calibrated against source concentrations and this relationship shown to be consistent over the normal range of exposure. This requires some consideration of the environmental and biological determinants of pollutant assimilation. Differences between populations can confound simple comparisons between sites based on native populations. Transplanted individuals, matched for age, sex and physiological state, might be used when the aim is not to assess bioavailability to the resident population. A simple measure of their capacity to detect differences in ambient pollutant levels is proposed to evaluate candidate species, to assess their consistency and capacity to equilibrate with their source. A small survey of earthworms from a well-defined gradient of Pb pollution is used to illustrate problems of interpreting tissue concentrations in sentinels.

Effect of Cd or Pb addition to Cu-contaminated soil on tissue Cu accumulation in the earthworm, Dendrobaena veneta

Generally, soil heavy metal contamination consists of a mixture of heavy metals. Soil chemical properties and interaction with other pollutants in soil affect the external heavy metal bioavailability. Moreover, interaction with other pollutants accumulated in organisms may change the toxicity of each pollutant. Therefore, the hypotheses was tested that addition of Cd or Pb to Cu-contaminated soil would lead to an increase in tissue Cu accumulation in the earthworm, Dendrobaena veneta, caused by (i) induction of metallothionein by Cd, or (ii) an increase in Cu concentration in soil solution due to the exchange of adsorbed Cu for Pb. Tissue heavy metal concentrations were determined after exposure in contaminated soils for 3 or 21 days. Considerable amounts of Cu, Cd, and Pb were accumulated, indicating that these heavy metals were available for uptake by D. veneta. Both Cd and Pb, however, did not significantly affect tissue Cu accumulation.

Cu accumulation in the earthworm Dendrobaena veneta in a heavy metal (Cu, Pb, Zn) contaminated site compared to Cu accumulation in laboratory experiments

Earthworms (Dendrobaena veneta) were exposed to heavy metal contaminated soil from a field site under both laboratory and field conditions. In the laboratory study, D. veneta were analysed for Cu after 2 weeks' exposure. The tissue Cu concentration (Cu(W)) increased proportionally with the total extractable soil Cu content (Cu(T)) in soils that contained less than 150 mg Cu kg(-1). In D. veneta exposed to soils containing more than Cu(T) = 150 mg kg(-1), however, we observed no further increase in Cu(W). In a 64-m(2) field plot at a contaminated site, 81 soil samples were taken and analysed for Cu, Pb, Zn and pH. In June 1994, 1000 D. veneta were homogeneously distributed in the plot and sampled after 1, 2 and 5 weeks to analyse for Cu. Additionally, 2000 D. veneta were introduced in September 1994 and sampled after 1, 2 and 4 weeks. At locations where earthworms were removed, the soil Cu content was estimated by disjunctive kriging. Cu concentration factors (ratio of Cu(W) to Cu(T)) in the field experiment were in excellent agreement with those of the laboratory experiment. This indicates that, with a sufficiently high sampling density, it may be feasible to predict earthworm Cu accumulation in the field using a concentration factor determined in the laboratory.

Experimental accumulation of lead from soil through earthworms to common shrews

Common shrews (Sorex araneus) were fed on earthworms containing high concentrations of lead. Both the earthworms and shrews originated from uncontaminated areas, but earthworms for the "lead" group of shrews were reared in the laboratory for 3 or 4 weeks in highly Pb-polluted soil from near an old lead smelter. The control group of shrews received the same amount of earthworms from the uncontaminated area. The acceptance of the experimental food by shrews was significantly lower in the lead group, indicating that the shrews were able to detect the lead in their food. After 2-31 days of feeding, the shrews in the lead group had significantly higher Pb concentrations in their liver, kidney, bone, and pelt than did the controls. Both the number of deaths during the experiment and the proportion of individuals with changes in kidney histology were significantly higher in the lead group.