Effects of metal pollution on earthworm communities in a contaminated floodplain area: Linking biomarker, community and functional responses.

Effects on earthworms in the contaminated floodplain area the Biesbosch, the Netherlands, were determined at different levels of organization using a combination of field and laboratory tests. The species Lumbricus rubellus, collected from different polluted sites in the Biesbosch, showed reduced values for the biomarker neutral red retention time (NRRT), mainly explained by high metal concentrations in the soil and the resulting high internal copper concentrations in the earthworms. Organic pollutant levels in earthworms were low and did not explain reduced NRRTs. Earthworm abundance and biomass were not correlated with pollutant levels in the soil. Litterbag decomposition and bait-lamina feeding activity, measures of the functional role of earthworms, were not affected by metal pollution and did not show any correlation with metal concentrations in soil or earthworms nor with NRRT. Effects at the biochemical level therefore did not result in a reduced functioning of earthworm communities.

Metal accumulation in the earthworm Lumbricus rubellus. Model predictions compared to field data.

The mechanistic bioaccumulation model OMEGA (Optimal Modeling for Ecotoxicological Applications) is used to estimate accumulation of zinc (Zn), copper (Cu), cadmium (Cd) and lead (Pb) in the earthworm Lumbricus rubellus. Our validation to field accumulation data shows that the model accurately predicts internal cadmium concentrations. In addition, our results show that internal metal concentrations in the earthworm are less than linearly (slope<1) related to the total concentration in soil, while risk assessment procedures often assume the biota-soil accumulation factor (BSAF) to be constant. Although predicted internal concentrations of all metals are generally within a factor 5 compared to field data, incorporation of regulation in the model is necessary to improve predictability of the essential metals such as zinc and copper.

Water-extractability, free ion activity, and pH explain cadmium sorption and toxicity to Folsomia candida (Collembola) in seven soil-pH combinations.

Toxicity of cadmium to Folsomia candida was determined in soils at different pHs (3.5, 5.0, and 6.5). The Langmuir sorption constant (K(L)), based on pore-water or water-extractable concentrations, showed a pH-related increase of cadmium sorption that was most pronounced when using free Cd2+ ion activities ([Cd2+]s). Two-species Langmuir isotherms that used total cadmium concentration ([Cd]) or [Cd2+] and pH in the water-extractable fractions gave the best description of cadmium sorption on all soils together. Cadmium concentrations causing 50% reduction of growth and reproduction (median effective concentrations [EC50s]) differed by a factor of 4.5 to 20 when based on total soil concentrations and increased with increasing pH. However, when based on water-extractable or pore-water [Cd] or [Cd2+], EC50s decreased with increasing pH, but differences between soils were still a factor of 4.5 to 32. The EC50s differed by less than a factor of 2.2 when based on body [Cd] in the surviving animals. Two-species Langmuir isotherms were used to relate body [Cd] in survivors to [Cd2+], corrected for pH in water-extractable or pore-water fractions. An excellent description of effects on growth and reproduction was found when related to the body concentrations predicted in this way; the difference in EC50s between soils was reduced to a factor <2. This demonstrates that F. candida is mainly exposed to cadmium through the soil solution, and suggests that principles of a biotic ligand model approach may be applicable for this soil organism.

Ring-testing and field-validation of a terrestrial model ecosystem (TME)--an instrument for testing potentially harmful substances: effects of carbendazim on nematodes.

The effects of the fungicide carbendazim (applied in the formulation Derosal) on nematodes was determined in Terrestrial Model Ecosystem (TME) tests and field-validation studies. TMEs consisted of intact soil columns (diameter 17.5 cm; length 40 cm) taken from a grassland or, in one case, from an arable site. The TMEs were taken from the same site where the respective field study was performed. The tests were performed in Amsterdam (The Netherlands), Bangor (Wales, England), Coimbra (Portugal) and Flörsheim (Germany). Differences concerning nematode overall abundance, the number of nematode families, the trophical structure of the nematode cenosis and the maturity index (MI) were not found between the controls of TME tests and the respective field-validation studies. Effects caused by the chemical treatment, however, were observed on the number of nematode families, on the trophical structure of the nematode cenosis and on the maturity index (MI). Effects on the relative abundance of the omnivorous nematodes were most pronounced, whereas the overall nematode abundance was not affected. The observed effects appear not to differ between the TME tests and the respective field-validation studies. All measurement endpoints in both TMEs and field, showed rather large variations. Therefore, NOEC-values were often equal or higher than the highest treatment level and EC50-values were calculated only for the omnivorous nematodes. NOEC- and EC50-values derived from the TME ring-test and the field-validation study indicate that the reproducibility (i.e. the variation between the partners) was reasonable, although different soils from different sites were used. The EC50-values determined for the effect of carbendazim on the relative abundance of the omnivorous nematodes ranged between 0.93 and 7.24 kg a.i./ha (1.24-9.63 mg/kg). Due to the higher sensitivity of the relative abundance of the omnivorous nematodes compared to the other measurement endpoints it is recommended to use this parameter as the main endpoint.

Ring-testing and field-validation of a terrestrial model ecosystem (TME)--an instrument for testing potentially harmful substances: effects of carbendazim on soil microarthropod communities.

The effects of the fungicide carbendazim (applied in the formulation Derosal) on soil microarthropod communities was determined in three Terrestrial Model Ecosystem (TME) tests and a field-validation study for a period of 16 weeks after application. TMEs consisted of intact soil columns (diameter 17.5 cm: length 40 cm) taken from a grassland field. The TMEs for the two tests (pre-test and ring-test) in Amsterdam, The Netherlands, were taken from the same site where the field-validation study was performed, the third TME test (pre-test) was performed in Bangor, Wales. Collembola communities showed large variations in numbers and no effects of carbendazim on species diversity were seen. Mites were not determined to species but only to four main taxonomic groups (Astigmata, Cryptostigmata, Mesostigmata, Prostigmata). Mite numbers in both TME and field soils also showed rather large variations and it was difficult to find consistent effects of carbendazim treatment. Principal response curve (PRC) analysis was performed to further evaluate effects of carbendazim on Collembola and mites in the TME and field tests. This multivariate technique demonstrated significant effects of carbendazim on Collembola communities in one TME test and the field-validation study but not in the other two TME tests, while mite communities showed significant effects in two TME tests but not in the third TME test and the field-validation study. NOECs for the effect of carbendazim on Collembola and mite communities derived from these PRC analyses ranged from 0.36 to 87.5 kg a.i./ha.

Ring-testing and field-validation of a terrestrial model ecosystem (TME)--an instrument for testing potentially harmful substances: effects of carbendazim on enchytraeids.

The effects of the fungicide carbendazim (applied in the formulation Derosal) on enchytraeids were determined in Terrestrial Model Ecosystem (TME) tests and field-validation studies. TMEs consisted of intact soil columns (diameter 17.5 cm; length 40 cm) taken from a grassland or, in one case, from an arable site. The TMEs were taken from the same site where the respective field study was performed. The tests were performed in Amsterdam (The Netherlands), Bangor (Wales, England), Coimbra (Portugal) and Flörsheim (Germany). Concerning the enchytraeid overall abundance and the number of species, differences between sampling points and differences between the TME tests and the respective field-validation studies were not found in the controls. Generally, a high variability of data which reduced the probability of determining statistically significant differences was determined. Effects of the model chemical carbendazim were determined for the overall abundance of enchytraeids and the number of enchytraeid species. The clearest dose-response relationship was found for the abundance of the genus Fridericia. The abundance of the genera Achaeta and Enchytraeus was not affected. Effects were most pronounced 8 and 16 weeks after application of the test chemical. The observed effects appeared not to differ between the TME tests and the respective field-validation studies. Due to the high variability of data NOEC-values could often not be determined. The EC50-values derived from the TME pre-test, TME ring-test and field-validation study indicate that the reproducibility (i.e. the variation between the partners) of the EC50-values was reasonable, although different soils were used at the different sites. The EC50-values for effects of carbendazim on enchytraeid abundance ranged between 0.5 and 28.4 kg a.i./ha (corresponding to 0.7-37.8 mg/kg), on the number of species between 7.2 and 87.4 kg a.i./ha (9.5-116.2 mg/kg) and on the abundance of Fridericia between 0.7 and 18.6 kg a.i./ha (0.9-24.7 mg/kg). Since one specific taxon has the potential to be more sensitive for a chemical stressor than other taxa, it is recommended to include investigations on the species level in the assessment of TME or field studies.

Ring-testing and field-validation of a terrestrial model ecosystem (TME)--an instrument for testing potentially harmful substances: effects of carbendazim on earthworms.

The effects of the fungicide carbendazim (applied in the formulation Derosal) on earthworms (Lumbricidae) was determined in Terrestrial Model Ecosystem (TME) tests and field-validation studies. TMEs consisted of intact soil columns (diameter 17.5 cm; length 40 cm) taken from a grassland or, in one case, from an arable site. The TMEs were taken from the same site where the respective field-validation study was performed. The tests were performed in Amsterdam (The Netherlands), Bangor (Wales, UK), Coimbra (Portugal) and Flörsheim (Germany). The sites selected had an earthworm coenosis representative of the different land use types and regions. In addition, the differences between the coenosis found in the TMEs and the respective field sites were in general low. A high variability was found between the replicate samples, which reduces the probability of determining significant differences by the statistical evaluation of the data. Similar effects of the chemical treatment were observed on abundance as well as on biomass. Effects were most pronounced 16 weeks after application of the test chemical. The observed effects on earthworm abundance and biomass did not differ between the TME tests and the respective field-validation studies. Effects on earthworm diversity were difficult to assess since the number of individuals per species was low in general. However, the genus Lumbricus and in particular L. terrestris and L. rubellus seemed to be more affected by the chemical treatment than others. NOEC and EC50-values derived from the TME pre-test, the TME ring-test and the field-validation study indicate that the TMEs of the different partners delivered comparable results although different soils were used. Due to the high variability NOECs could often not be determined. The EC50-values for the effect of carbendazim on earthworm abundance ranged between 2.04 and 48.8 kg a.i./ha (2.71-65.2 mg/kg soil) and on earthworm biomass from 1.02 to 34.6 kg a.i./ha (1.36-46.0 mg/kg soil). These results indicate that the abundance and biomass of earthworms are suitable endpoints in ecotoxicological studies with TMEs.

Ring-testing and field-validation of a terrestrial model ecosystem (TME)--an instrument for testing potentially harmful substances: effects of carbendazim on nutrient cycling.

The effect of the fungicide carbendazim (applied in the formulation Derosal) on nutrient cycling in soil was determined in Terrestrial Model Ecosystem (TME) tests and corresponding field-validation studies, which were performed in four different countries (United Kingdom, Germany, Portugal, and The Netherlands). The tests used different soil types, and lasted for 16 weeks. On three of the four sites, grassland soils were used while the fourth site had an arable soil. TMEs consisted of intact soil columns (diameter 17.5 cm; length 40 cm) and were taken from the site where the field study was performed. In the first series of TME tests, carbendazim applied at dosages unto 77.8 kg a.i./ha did not affect sulfate and phosphate concentrations in the top 15 cm soil layers. These nutrients were therefore no longer included in the second series of TME tests and the field-validation studies. Ammonium concentrations in the top soil layers of TMEs and field plots, and in the leachates of the TME columns did not show any effect of carbendazim treatment. Nitrate concentrations in soils and leachates did show some reduction at the highest treatment levels (77.8 kg a.i./ha in the first TME tests, 87.5 kg a.i/ha in the second TME tests and the field-validation studies). Since nitrate concentrations in both soils and leachates were correlated with soil moisture content, these effects could however, mainly be attributed to variations in soil moisture contents, and in some cases also indirectly to effects on earthworm activity. It is concluded that carbendazim, even at dosages as high as 87.5 kg a.i./ha, does not have a significant impact on soil nutrient cycling processes. Nutrient levels in TME tests and the field-validation studies generally showed similar patterns, thus confirming the predictive value of the TME test system.

Ring-testing and field-validation of a terrestrial model ecosystem (TME)--an instrument for testing potentially harmful substances: effects of carbendazim on organic matter breakdown and soil fauna feeding activity.

Organic matter (OM) decomposition and soil fauna feeding activity were integrated as functional endpoints into ecotoxicological tests with intact-soil-core Terrestrial Model Ecosystems (TMEs). Cellulose filter paper served as standardized OM and was either inserted into the top soil or placed on the soil surface for a period of up to 16 weeks. Faunal feeding activity was assessed by the bait-lamina method. The fungicide carbendazim, applied at six dosages ranging from 0.36 kg/ha to 87.5 kg a.i./ha, served as a model chemical. To validate the results from the TME test, a field study was run in parallel. In TMEs the cellulose paper inserted into the soil was decomposed faster than under field conditions. The carbendazim-induced effects on OM decomposition in TMEs and in the field were comparable and followed a clear dose-response relationship. The calculated EC50 values after 8 weeks of incubation were 9.5, 7.1 and 2.1 kg carbendazim/ha for grassland TMEs, grassland field and arable TMEs, respectively. The feeding activity of the soil fauna showed a large variability. The EC50 values for the effect of carbendazim on bait-lamina consumption ranged between 2.0 and 56 kg a.i./ha. Effects on decomposition were correlated with effects on enchytraeids and earthworms but not with effects on bait-lamina consumption.