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The aim of this study was to determine the bioavailability of metals in field soils contaminated with chromated copper arsenate (CCA) mixtures. The uptake and elimination kinetics of chromium, copper, and arsenic were assessed in the earthworm Eisenia andrei exposed to soils from a gradient of CCA wood preservative contamination near Hartola, Finland. In soils contaminated with 1480–1590 mg Cr/kg dry soil, 642–791 mg Cu/kg dry soil, and 850–2810 mg Ag/kg dry soil, uptake and elimination kinetics patterns were similar for Cr and Cu. Both metals were rapidly taken up and rapidly excreted by Eisenia andrei with equilibrium reached within 1 day. The metalloid As, however, showed very slow uptake and elimination in the earthworms and body concentrations did not reach equilibrium within 21 days. Bioaccumulation factors (BAF) were low for Cu and Cr (

Chromated copper arsenate (CCA) mixtures were used in the past for wood preservation, leading to large scale soil contamination. This study aimed at contributing to the risk assessment of CCA-contaminated soils by assessing the toxicity of binary mixtures of copper, chromium and arsenic to the earthworm Eisenia andrei in OECD artificial soil. Mixture effects were related to reference models of Concentration Addition (CA) and Independent Action (IA) using the MIXTOX model, with effects being related to total and available (H2O and 0.01 M CaCl2 extractable) concentrations in the soil. Since only in mixtures with arsenic dose-related mortality occurred (LC50 92.5 mg/kg dry soil), it was not possible to analyze the mixture effects on earthworm survival with the MIXTOX model. EC50s for effects of Cu, Cr and As on earthworm reproduction, based on total soil concentrations, were 154, 449 and 9.1 mg/kg dry soil, respectively. Effects of mixtures were mainly antagonistic when related to the CA model but additive related to the IA model. This was the case when mixture effects were based on total and H2O-extractable concentrations; when based on CaCl2-extractable concentrations effects mainly were additive related to the CA model except for the Cr–As mixture which acted antagonistically. These results suggest that the CCA components do interact leading to a reduced toxicity when present in a mixture.

International audience; Although soil characteristics modulate metal mobility and bioavailability to organisms, they are often ignored in the risk assessment of metal transfer. This paper aims to determine the ability of chemical methods to assess and predict cadmium (Cd), lead (Pb) and zinc (Zn) environmental bioavailability to the land snail Cantareus aspersus. Snails were exposed in the laboratory for 28 days to 17 soils from around a former smelter. The soils were selected for their range of pH, organic matter, clay content, and Cd, Pb and Zn concentrations. The influence of soil properties on environmental availability (estimated using HF-HClO(4), EDTA, CaCl(2), NH(4)NO(3), NaNO(3), free ion activity and total dissolved metal concentration in soil solution) and on environmental bioavailability (modelled using accumulation kinetics) was identified. Among the seven chemical methods, only the EDTA and the total soil concentration can be used to assess Cd and Pb environmental bioavailability to snails (r²(adj)=0.67 and 0.77, respectively). For Zn, none of the chemical methods were suitable. Taking into account the influence of the soil characteristics (pH and CEC) allows a better prediction of Cd and Pb environmental bioavailability (r²(adj)=0.82 and 0.83, respectively). Even though alone none of the chemical methods tested could assess Zn environmental bioavailability to snails, the addition of pH, iron and aluminium oxides allowed the variation of assimilation fluxes to be predicted. A conceptual and practical method to use soil characteristics for risk assessment is proposed based on these results. We conclude that as yet there is no universal chemical method to predict metal environmental bioavailability to snails, and that the soil factors having the greatest impact depend on the metal considered.

For cultivated soils, the important function of earthworms as ecosystem engineers and their major contribution to the composition and functioning of soil ecosystems with a varying species diversity has been extensively addressed. However, the role of earthworms as colonizers of virgin, uncultivated soil in the process of soil formation has been little researched and long underrated. To better understand this role, the following questions need to be considered: (1) what makes an early colonizer successful, what are its characteristics, and which species are the most successful and under what circumstances are they successful?; (2) what are the limiting factors in these colonization processes with respect to environmental conditions and also to interspecific interactions?; (3) what do earthworms contribute to the further colonization by other soil animals?; and (4) how do they impact the soil itself and what could therefore be the consequences for soil management and restoration? These questions have recently been addressed from the perspective of new (or 'alien') earthworm species invading ecosystems, suggesting a massive influx of species, competitive to the originally present fauna. This idea is, however, contrary to colonization, which suggests a gradual exploration of a previously uninhabited area. Unlike recent research, this review approaches colonization primarily as a spatial dispersal process and part of natural succession processes, and is mainly illustrated with examples of Palearctic species, either in Europe or introduced elsewhere. To begin, the various stages of colonization: dispersal, establishment, population growth and interspecies relations are analysed. Next, the colonization processes, the possible limiting environmental factors and the sequence of the appearance and establishment of species are described. Dispersal rates and sequences of colonization by different earthworm species are given for different soil ecosystems. For colonization, limiting environmental factors such as pH, soil type and heavy metal contents as well as the presence of organic matter seem to play a more important role than inherent ecological characteristics like r/. K selection. Finally, the role of earthworms in the early colonization of soils that are earthworm-free because of non-cosmopolitan distribution, drained former sea bottom, permanently water-logged soils or anaerobic, acid peaty soils are reviewed. If we understand the role of earthworms in succession, we will be able to improve their role in soil restoration and soil management. © 2011 Elsevier B.V.

The relevance of laboratory tests on toxicants for field situations is often disputed given that laboratory tests are conducted under, next to the toxicant stress, optimal conditions which are not expected in field situations. In this paper we confront the results of laboratory tests on growth, reproduction and survival of earthworms, in a polluted and a reference field soil with a field inventory of earthworms. The field inventory includes population density, biomass and demographic composition in life stages measured monthly over a period of one year. The field inventory showed that density and biomass was higher at the polluted field site, a result in conflict with the extrapolation of the laboratory tests that showed a decrease in population growth rate by 23% at this site compared to the reference. The field inventory and laboratory derived results agreed in the demographic composition of the population with more individuals in the younger age class at the polluted site compared to the reference. Abiotic and biotic conditions that differ between sites and could possibly explain the lower earthworm biomass and density at the reference site are discussed. We suggest that predation by the two to five times higher densities of meadow birds in spring may have caused the lower density and biomass of earthworms at the reference site.

In freshly deposited dredged sediment contaminated with PAHs, we followed the colonization of earthworm species by monthly monitoring over two years. Already five months after deposition the first species, Lumbricus castaneus, appeared, although only temporarily. The first permanent colonizing species was L. rubellus, soon followed by Aporrectodea caliginosa and L. castaneus, and a few months later Eiseniella tetraeda. At the end of the two-year observation period some first few specimen of Allolobophora rosea were present. These earthworm species colonized the deposited sediment apparently in succession. The colonization of each individual species did not show a gradual influx from the bordering dikes at both sides of the deposit, but a fast colonization over the whole width, presumably by surface dispersal, although at low and variable numbers, followed by a gradual increase of population numbers. Modeling the dispersal showed that diffusion was the primary driving factor. Also juvenile earthworms were observed locally in high numbers, so reproduction did occur. Total earthworm numbers in the deposit reached a maximum of 80% of the numbers in the bordering dikes consisting of loamy and clayey soils. Numbers were highest in periods with warm and rainy weather. The appearance of earthworms improved the soil development, stimulated a faster desiccation and aeration of the sediment and may have contributed to the increased degradation of PAHs, especially three- and four-ring PAHs. © 2009 Elsevier B.V. All rights reserved.

Laboratory tests are typically conducted under optimal conditions testing the single effect of a toxicant. In the field, due to suboptimal conditions, density dependence can both diminish and enhance effects of toxicants on populations. A review of the literature indicated that general insight on interaction of density and toxicants is lacking, and therefore no predictions on their combined action can be made. In this paper the influence of zinc was tested at different population densities on the demographic rates: growth, reproduction, and survival in the earthworm Lumbricus rubellus. Changes in these rates were extrapolated with a combined Dynamic energy budget (DEB) and a population model to assess consequences at the population level. Inference from the DEB model indicated that density decreased the assimilation of food whereas zinc increased the maintenance costs. The combined effects of density and zinc resulted in a decrease in the intrinsic rate of population increase which suddenly dropped to zero at combinations of zinc and density where development is so strongly retarded that individuals do not mature. This already happened at zinc levels where zinc induced mortality is low and therefore density enhances zinc effects and density dependent compensation is not expected.

Summary Knowledge of the effects of species diversity within taxonomic groups on nutrient cycling is important for understanding the role of soil biota in sustainable agriculture. We hypothesized that earthworm species specifically affect nitrogen mineralization, characteristically for their ecological group classifications, and that earthworm species interactions would affect mineralization through competition and facilitation effects. A mesocosm experiment was conducted to investigate the effect of three earthworm species, representative of different ecological groups (epigeic: Lumbricus rubellus; endogeic: Aporrectodea caliginosa tuberculata; and anecic: Lumbricus terrestris), and their interactions on the bacterial community, and on nitrogen mineralization from 15N-labelled crop residue and from soil organic matter. Our results indicate that L. rubellus and L. terrestris enhanced mineralization of the applied crop residue whereas A. caliginosa had no effect. On the other hand, L. rubellus and A. caliginosa enhanced mineralization of the soil organic matter, whereas L. terrestris had no effect. The interactions between different earthworm species affected the bacterial community and the net mineralization of soil organic matter. The two-species interactions between L. rubellus and A. caliginosa, and L. rubellus and L. terrestris, resulted in reduced mineral N concentrations derived from soil organic matter, probably through increased immobilization in the bacterial biomass. In contrast, the interaction between A. caliginosa and L. terrestris resulted in increased bacterial growth rate and reduced total soil C. When all three species were combined, the interaction between A. caliginosa and L. terrestris was dominant. We conclude that the effects of earthworms on nitrogen mineralization depend on the ecological traits of the earthworm species present, and can be modified by species interactions. Knowledge of these effects can be made useful in the prevention of nutrient losses and increased soil fertility in agricultural systems, that typically have a low earthworm diversity.

Earthworms dominate the animal biomass in moist floodplain soils. They are known to survive long periods in aerated water, but little is known about earthworm population dynamics in floodplain systems with changing inundation frequencies. This study determined earthworm population dynamics in a floodplain system, in relation to frequency and duration of flooding events. From October 2000 to May 2003 earthworms were hand sorted in the 'Afferdensche en Deestsche Waarden', a floodplain on the south bank of the river Rhine, near Druten, The Netherlands. Earthworm numbers and biomasses per age class (adult, subadult, juvenile) were recorded. Numbers and biomasses tend to decrease during flooding. Lumbricus terrestris was found in high numbers (>10/m2) only at the end of a flooding period. Allolobophora chlorotica was hardly affected by flooding; their biomass remained stable during the year. Aporrectodea caliginosa showed fluctuating numbers and biomasses during the sampling period that did not correlate with flooding frequency. Numbers and biomasses of Lumbricus rubellus were strongly reduced at the end of each flooding event, but their population densities fully recovered until next flooding event. Earthworm populations in floodplains fluctuate in time, depending on the season and on the time, duration and frequency of flooding. Different earthworm species react differently towards these flooding dynamics. © 2004 Elsevier GmbH. All rights reserved.

The term ‘critical body residue’ (CBR) was defined as the lowest observed total body concentration of a contaminant in an organism, which is associated with the occurrence of adverse toxic effects in either individuals or populations of a defined age or stage of development. In this study, internal toxicity thresholds were determined for copper in the clitellated adult stage of earthworms ( Lumbricus rubellus and Aporrectodea caliginosa ). The objective was to assess the applicability of CBRs as a practical tool in soil quality assessment of contaminated sites and as a means of a sustainable protection of earthworm fauna. Laboratory studies showed that body concentrations of Cu were generally in agreement with the chemically available CaCl 2 -extractable fraction in soil, but that there was also some evidence of internal pH-related homeostatic regulation. Toxicological correlates of body Cu concentrations with adverse effects on cocoon production (fecundity) suggested an approximate sublethal internal threshold of about 40 mg kg −1 , with mortality occurring at about 60 mg kg −1 . Adult L. rubellus sampled from areas with a wide range of metal pollution showed body Cu concentrations with a minimum of 8 mg kg −1 and a maximum of 60 mg kg −1 . Beyond this apparent physiological tolerance range, environmental management directed at optimal earthworm population survival may not be sustainable in contaminated fields. Studies of L. rubellus colonizing a metal-contaminated experimental sludge-treated field showed that a reduced rate of colonization can already be associated with an average body Cu concentration of 25 mg kg −1 . However, in this particular field situation mixture effects of other metals that were also present in the soil and the occurrence of avoidance behaviour during colonization may have contributed to this low internal toxicity threshold. It is concluded that the CBR approach seems to be a feasible option for use as a tool in a bioavailability-based soil quality assessment, even for essential trace metals like copper, but that further insight may be needed to establish the uncertainty and reliability of the application in environmental quality assessment and decision making.

The important role of earthworms in the biomagnification of heavy metals in terrestrial ecosystems is widely recognised. Differences in earthworm biomass between sites is mostly not accounted for in ecological risk assessment. These differences may be large depending on soil properties and pollution status. A survey of earthworm biomass and colonisation rate was carried out on dredged sediment-derived soils (DSDS). Results were compared with observations for the surrounding alluvial plains. Mainly grain size distribution and time since disposal determined earthworm biomass on DSDS, while soil pollution status of the DSDS was of lesser importance. Highest earthworm biomass was observed on sandy loam DSDS disposed at least 40 years ago.

Phytochelatins are small cysteine-rich non-ribosomal peptides that chelate soft metal and metalloid ions, such as cadmium and arsenic. They are widely produced by plants and microbes; phytochelatin synthase genes are also present in animal species from several different phyla, but there is still little known about whether these genes are functional in animals, and if so, whether they are metal-responsive. We analysed phytochelatin production by direct chemical analysis in Lumbricus rubellus earthworms exposed to arsenic for a 28 day period, and found that arsenic clearly induced phytochelatin production in a dose-dependent manner. It was necessary to measure the phytochelatin metabolite concentrations directly, as there was no upregulation of phytochelatin synthase gene expression after 28 days: phytochelatin synthesis appears not to be transcriptionally regulated in animals. A further untargetted metabolomic analysis also found changes in metabolites associated with the transsulfuration pathway, which channels sulfur flux from methionine for phytochelatin synthesis. There was no evidence of biological transformation of arsenic (e.g. into methylated species) as a result of laboratory arsenic exposure. Finally, we compared wild populations of earthworms sampled from the field, and found that both arsenic-contaminated and cadmium-contaminated mine site worms had elevated phytochelatin concentrations.

International audience; This study investigates the relevance of several soil chemical extractions (calcium chloride, acetic acid, citric acid and a four-step sequential procedure) and predicted free metal ion activities in the soil solution to characterise the transfer of trace metals (Cd, Pb, and Zn) from soil to snail soft tissues over a large smelter-impacted area (Metaleurop Nord, Nord-Pas-de-Calais, France). The study was first performed on six snail species together and then specifically on Cepaea sp. and Oxychilus draparnaudi. When the six species were considered together, the accumulation of metals depended mostly on the species. When significant, total or extractable metal concentrations, or the predicted free ion activities, accounted for less than 7% of the variation of the metal concentrations in the snail tissues. Species-specific analyses showed that extractable concentrations explained approximately 25% of the variation of the metal concentrations in O. draparnaudi, and up to 8% in Cepaea snails. When using total soil concentrations and soil properties as explanatory variables, the models were generally slightly better, explaining up to 42% of the variance. The soil extraction procedures and predicted free ion activities used in this study did not accurately estimate the metal transfer from soil to snails and could not be used in risk assessment.

Earthworm activity is known to increase emissions of nitrous oxide (N 2 O) from arable soils. Earthworm gut, casts, and burrows have exhibited higher denitrification activities than the bulk soil, implicating priming of denitrifying organisms as a possible mechanism for this effect. Furthermore, the earthworm feeding strategy may drive N 2 O emissions, as it determines access to fresh organic matter for denitrification. Here, we determined whether interactions between earthworm feeding strategy and the soil denitrifier community can predict N 2 O emissions from the soil. We set up a 90-day mesocosm experiment in which 15 N-labeled maize ( Zea mays L.) was either mixed in or applied on top of the soil in the presence or absence of the epigeic earthworm Lumbricus rubellus and/or the endogeic earthworm Aporrectodea caliginosa . We measured N 2 O fluxes and tested the bulk soil for denitrification enzyme activity and the abundance of 16S rRNA and denitrifier genes nirS and nosZ through real-time quantitative PCR. Compared to the control, L. rubellus increased denitrification enzyme activity and N 2 O emissions on days 21 and 90 (day 21, P = 0.034 and P = 0.002, respectively; day 90, P = 0.001 and P = 0.007, respectively), as well as cumulative N 2 O emissions (76%; P = 0.014). A. caliginosa activity led to a transient increase of N 2 O emissions on days 8 to 18 of the experiment. Abundance of nosZ was significantly increased (100%) on day 90 in the treatment mixture containing L. rubellus alone. We conclude that L. rubellus increased cumulative N 2 O emissions by affecting denitrifier community activity via incorporation of fresh residue into the soil and supplying a steady, labile carbon source.

This paper reviews the role of earthworms in the early colonisation of contaminated soils as well as sediment and waste deposits, which are worm-free because of anthropogenic activities such as open-cast mining, soil sterilisation, consistent pollution or remediation of contaminated soil. Earthworms live in close interaction with their soil environment and are able to change it considerably by their burrowing and litter comminuting behaviour. While earthworms have been studied extensively, several questions still remain unanswered such as: What are the characteristics of successful early colonisers? Do they function well in dispersal, individual establishment or population growth? Do the negative environmental conditions in these kinds of anthropogenic soils hamper colonization or are these colonizers relatively resistant to it? To what extent does colonization change the characteristics of the colonized substrate? In short, do earthworms impact the soil? In this paper, the characteristics that make earthworms successful colonisers are briefly described as well as which species are the most successful and under what circumstances, and what do earthworms contribute to the total process of succession. We propose that it is not so much eco-type or r-K strategy that govern success and succession of earthworm colonisation but rather environmental flexibility not only towards pH, desiccation, and temperature but also towards contaminants such as heavy metals. Moreover, the formation of an organic litter layer, in close connection with re-vegetation of the area, is essential for establishing earthworm populations, which, at first, are mainly superficially and shallow active species. The burrowing and organic matter digesting activity of these earthworms changes the upper soil to a well mixed humus layer suitable for deep burrowing earthworm species.

In many densely populated areas, riverine floodplains have been strongly impacted and degraded by river channelization and flood protection dikes. Floodplains act as buffers for flood water and as filters for nutrients and pollutants carried with river water and sediment from upstream source areas. Based on results of the EU-funded "AquaTerra" project (2004-2009), we analyze changes in the dynamics of European river-floodplain systems over different temporal scales and assess their effects on contaminant behaviour and ecosystem functioning. We find that human-induced changes in the hydrologic regime of rivers have direct and severe consequences on nutrient cycling and contaminant retention in adjacent floodplains. We point out the complex interactions of contaminants with nutrient availability and other physico-chemical characteristics (pH, organic matter) in determining ecotoxicity and habitat quality, and draw conclusions for improved floodplain management.

In traditional environmental risk assessment for soils, interactions between biota, contaminants and soil functioning are seldom taken into account. Also, single species toxicity tests are conducted with a fixed number of test animals. The objective of this study was to investigate effects of zinc (0–620 mg Zn kg −1 dry soil) on soil ecosystem processes at different densities of the earthworm Lumbricus rubellus . Experiments were conducted using 1-liter microcosms equipped with respirometers. The presence of L. rubellus stimulated relevant soil processes and parameters: litter fragmentation, leaf litter mass loss from the soil surface, soil organic matter (SOM) content and soil respiration. Zinc was not lethal to L. rubellus , but negatively impacted soil respiration at the highest concentrations. Litter mass loss from the soil surface was also decreased by zinc and there was a significant interaction with worm density. The results of the study demonstrate that the impact of zinc on soil processes depends on the presence and densities of key soil organisms such as earthworms that influence decomposition and SOM content. The outcome of this research can be used to make existing models for site-specific risk assessment more ecologically relevant, linking effects of contaminants on soil fauna populations with effects on ecosystem functioning.

River floodplains are dynamic and fertile ecosystems where soil invertebrates such as earthworms can reach high population densities. Earthworms are an important food source for a wide range of organisms including species under conservation such as badgers. Flooding, however, reduces earthworm numbers. Populations recover from cocoons that survive floods. If the period between two floods is too short such that cocoons cannot develop into reproductive adults, populations cannot sustain themselves. Both climate change and floodplain rehabilitation change the flooding frequency affecting earthworm populations. The present paper estimates the influence of climate change and floodplain rehabilitation on the viability of earthworm populations in a Dutch floodplain; the Afferdensche and Deestsche Waarden along the River Waal. This floodplain will be part of major river rehabilitation plans of the Dutch government. In those plans, the floodplain will experience the construction of a secondary channel and the removal of part of its minor embankment. To estimate the impact of these plans and climate change, we used a dataset of daily discharges for 1900-2003 for the River Rhine at the Dutch-German border. We perturbed this dataset to obtain two new datasets under climate change scenarios for 2050 and 2100. From the original and two projected datasets we derived the frequency distributions for the annual periods without inundations for the studied floodplain. We subsequently compared the duration of these inundation-free (dry) periods with the maturation age distribution for L. rubellus as derived from a Dynamic Energy Budget model. This comparison yielded in which parts of our study area and under which climate conditions the populations would still be viable, be able to adapt or become extinct. The results show that climate change has almost no adverse effect on earthworm viability. This is because climate change reduces the flooding frequency during the earthworms growing season. Floodplain rehabilitation, on the other hand, reduces the part of the floodplain area where populations can sustain themselves. Before rehabilitation, only 12% of the floodplain area cannot sustain a viable earthworm population. After rehabilitation, this increases to 59%, 28% of which is due to more frequent flooding. Enhanced exposure to soil contaminants may further suppress earthworm viability. This could frustrate further nature development and the viability of earthworm-dependent species such as the badger (Meles meles) or little owl (Athene noctua vidalli species), which is an objective of the river rehabilitation plans in the Netherlands.

In industrialized countries river floodplains can be strongly polluted with heavy metals. Published studies on effects of heavy metal pollution on soil invertebrates in floodplains, however, are inconclusive. This is unexpected since studies in other less dynamic environments reported clear effects at even lower levels of pollution. Flooding induces extra variation in invertebrate biomass and abundance which may reduce the probability to detect heavy metal effects. In this paper we combine reported data from studies on river floodplains in The Netherlands and Belgium and statistically analyze the effect of heavy metals on species composition, biomass, density and individual weight of earthworms. Interaction effects of heavy metal stress and flooding are also considered. The results suggest clear effects of zinc and copper on all variables and interaction of heavy metals and flooding for individual weight. (c) 2006 Elsevier Ltd. All rights reserved.

We investigated the accumulation of copper (Cu) by the springtail Folsomia candida Willem, if exposed to Cu-contaminated sandy soil with yeast as a food source. Commonly, the dissolved and the easily desorbed Cu fractions are assumed to be available for uptake, and as both fractions depend on pH, a pH dependency of copper uptake and accumulation is expected. In recent studies with springtails this dependency was not observed. To explain this, we show that both the adsorption of copper by yeast and by soil is indeed pH dependent; however, these dependencies differ. Addition of yeast as a food source to copper-contaminated soil leads to competition for copper by yeast and soil that suppresses the pH dependency of copper adsorption by yeast. This may cause a pH dependency not to be observed in copper accumulation by springtails if they predominantly feed on yeast in bioassays. We conclude that the addition of artificial food sources in bioassays may affect the cause-effect relationships that are investigated. A combination of (soil) chemical experimentation and modeling and ecotoxicological studies may help in identifying such bias and, therefore, with interpreting bioassays.

Matrix models can be used to extrapolate effects of environmental toxicants on life history parameters to the population level. In applications of these models, life history parameters are usually treated as independent factors; however, they are actually strongly linked to each other. To interpret the effect of toxicants on life history parameters considering their interrelatedness the dynamic energy budget (DEB) theory can be applied. This theory is based on closed energy and mass balances and describes in a mechanistic way the acquisition and use of energy by individuals. In the present study we extended an existing combined DEB and matrix population model with an approach to take covariability of the DEB parameters into account. This was accomplished by estimating the joint posterior distribution of the parameters using Bayesian statistics. We used this model to extrapolate effects of copper in the common earthworm Dendrobaena octaedra to the population level.