Diversity of Paenibacillus durus strains isolated from soil and different plant rhizospheres evaluated by ARDRA and gyrB-RFLP analysis

Strains belonging to Paenibacillus durus isolated from the rhizosphere of various grasses and from bulk soil were previously divided into five phenotypic groups (A1–A5) based on the fermentation pattern of six carbohydrates (A1: sorbitol (+), A2: dulcitol and tagatose (+), A3: starch and glycogen (+), A4: starch, glycogen and d-arabitol (+) and A5: negative for these carbohydrates). This study aimed to assess whether plant types select for specific P. durus phenotypic groups. For that purpose, polymerase chain reaction-restriction fragment length polymorphism analysis of part of genes encoding 16S rRNA (ARDRA) and DNA gyrase subunit B (gyrB-RFLP) were used to produce genetic fingerprints. ARDRA and gyrB-RFLP data were clustered together to generate a dendrogram and two main clusters were observed. Cluster I showed a predominance of strains isolated from wheat, maize and sugarcane rhizospheres. Strains isolated from maize were distributed among the five patterns of carbohydrate metabolism, while strains isolated from sugarcane showed to be predominantly able to metabolize starch and glycogen. Neither sorbitol- nor arabitol-metabolizing strains were found in cluster II, which consisted of strains isolated from soil and from all plant species used. Our results suggest that the plants influenced the diversity of P. durus in their rhizospheres.     

Biological effects of native and exotic plant residues on plant growth, microbial biomass and N availability under controlled conditions

The leaf litter of six tropical tree species (Acacia holosericea, Acacia tortilis, Azadirachta indica, Casuarina equisetifolia, Cordyla pinnata and Faidherbia albida) frequently used in agroforestry plantations in Sahelian and Soudano-Sahelian areas were tested for their influence on soil nitrogen content, microbial biomass and plant growth under controlled greenhouse conditions. Half of the soil was planted with onion (Allium cepa L.) seedlings and the other half was not. Two herbaceous species, Andropogon gayanus and Eragrostis tremula, were also studied. Co-inertia analysis (CIA) and one-way analysis of variance (ANOVA) analysis showed that C. pinnata and F. albida leaf powder amendment induced the highest plant growth, whereas leaf powder of E. tremula is associated to higher microbial biomass and NH₄⁺ content. Higher onion seedlings growth is associated with higher concentration of nitrogen and lignin in leaf powders. Conversely, lower plant growth is associated to higher rates of cellulose, hemicellulose and phenols in leaves. Higher rates of cellulose and hemicellulose are associated with higher microbial biomass and NH₄⁺, whereas phenols are associated to lower microbial biomass. The results showed that amendment of A. holosericea leaf powder (high concentrations of phenol) to the soil resulted in a lower microbial biomass and lower onion seedlings growth. Data showed that the plant residue quality index (PRQI) could be a useful tool to predict the effects of litter materials on root growth in glasshouse conditions. The highest values on soil and plant parameters were recorded with C. pinnata litter. While powdered leaf material increased the accessibility of substrates to microbes, more research with C. pinnata leaf litter (under a wider range of ecological conditions) is needed. It could add deeper on its agronomic impact in the tropics.     

Occurrence of Platyarthrus schoblii (Isopoda, Oniscidea) and its ant hosts in Hungary

The myrmecophilous Platyarthrus schoblii Budde-Lund, 1885 is widely distributed and native in the Mediterranean region. In Hungary it was first found at Budapest, in 2001, in a colony of Lasius neglectus van Loon, Boomsma and Andrásfalvy, 1990 (Hymenoptera: Formicidae). This invasive and polygynous ant species is dispersing in an antropochorous way throughout Europe. There are 16 known colonies of L. neglectus in Hungary. Fourteen of them have been surveyed for the isopod, which was detected in eight cases (57%). In addition to L. neglectus, the isopod has been recently found with other native ant species [Lasius niger (Linnaeus, 1758), Lasius emarginatus (Olivier, 1791) and Tetramorium caespitum (Linnaeus, 1758)] in the country. We have also found the joint occurrence of P. hoffmannseggii Brandt, 1833 and P. schoblii. The co-occurrence and joint expansion of the ranges of L. neglectus and P. schoblii indicates their co-habitation and antropochorous dispersal while the appearance with L. emarginatus, L. niger and T. caespitum supports our hypothesis about possible adoption by different ant species.     

Survival of faecal coliforms in four different types of sludge-amended soils in Botswana

This study aimed at identifying the factors that affected the survival of faecal coliforms as measured by E. coli in four types of soils in Botswana which were amended with sewage sludge. Physico-chemical and biochemical properties and coliform population in the different soils, sludge, and soil/sludge mixtures were determined after sampling, on composing the soil/sludge mixtures, and 90 days after composing. Coliform population in the different soil/sludge mixtures decreased by about 90% after 90 days. The age of the sludge used and the rate at which it was applied to the soils initially determined the population of E. coli in each soil/sludge mixture, but after 90 days, differences inherent in the different soil types were the main determinants of the E. coli population. Percentage reduction of coliforms in Type 1 sludge mixtures were lower (38%) than in Type 2 sludge mixtures (57%). Up to 79.8% of the reduction observed in E. coli population in the Barolong luvisol-sludge mixtures after 90 days was caused by reduction in pH and moisture content, while 72.6%, 84.5% and 55.1% of the reduction in E. coli population in Tuli luvisol-, arenosol- and vertisol-sludge mixtures, respectively, was accounted for by the reduction in moisture content and Olsen P concentration. Coliform survival rates varied with soil types being 12%, 6.4%, 5.3% and 5.8% for the vertisol, arenosol, Barolong luvisol and Tuli luvisol, respectively. A minimum period of 90 days should be allowed between when sludge is applied to similar soils and when seeds are sown. The exact period should, however, be determined by the properties of the soil with fine-textured soils requiring a longer period than coarse-textured soils.     

Duration of the standard earthworm avoidance test: Are 48 h necessary?

Ecotoxicological tests are often recommended for the environmental risk assessment (ERA) of contaminated soils. In comparison to chemical residue analysis that focuses on individual contaminants, ecotoxicological tests are able to integrate the effects of the overall contamination, including interactions between individual contaminants, as well as between the contaminants and the various soil properties. However, their use is limited by the fact that the most sensitive tests are chronic tests such as the earthworm reproduction test which lasts 56 days. In order to promote the use of ecotoxicological tests for the routine assessment of contaminated test soils, the usage of short-term earthworm avoidance tests were investigated in the German project ERNTE. According to the International Organization for Standardization (ISO) guideline no. 17512-1, such a test has a duration of just 48 h which, although less than chronic tests, is still quite long in comparison to modern methods of chemical analysis whereby results are often available within 24 h (“on-site analysis”). Therefore, we assessed the effects of shortening the duration of the earthworm avoidance test from 48 to 24 h on the resulting ecotoxicological data. Eight uncontaminated natural soils and 22 contaminated natural soils containing a wide range of chemicals were tested concurrently for 24 and 48 h. Additionally, seven of the uncontaminated natural soils (one was excluded due to its low pH) plus Organization for Economic Co-operation and Development (OECD) artificial soil or LUFA (Landwirtschaftliche Untersuchungs- und Forschungsanstalt, Speyer, Germany) St. 2.2 soil were spiked with two model chemicals (zinc nitrate-tetrahydrate and tributyltin-oxide (TBT-O)) and tested accordingly. It was also investigated whether the results would differ when using either standard LUFA St. 2.2 or OECD artificial soil as a control when contaminated natural soils were tested. Statistical analysis of the data indicates that a decrease in test duration in general did not result in a different assessment of the test soils. In view of the fact that an ERA of contaminated soils is increasingly starting with an on-site analysis (i.e. data are available within 24 h) it is recommended to change the existing ISO guideline, i.e. to decrease the test duration from 48 to 24 h. In doing so, the use of a multi-concentration design increases the robustness of the test results. Both OECD and LUFA St. 2.2 soils are equally suitable as controls.     

The influence of soil characteristics on the toxicity of four chemicals to the earthworm Eisenia fetida andrei (Oligochaeta)

Summary The acute toxicity of Cd (chloride), chloroacetamide, 3,4-dichloroaniline and pentachlorophenol to the earthworm Eisenia fetida andrei was determined using the OECD (1984) artificial soil and contact testing procedures. To investigate the influence of two soil characteristics (pH and organic-matter content), the toxicity of the chemicals was also determined in two natural sandy soils. It is concluded that the filter-paper contact test cannot be recommended to predict earthworm toxicity of these chemicals in soil. Toxicity in soil was influenced by both pH and organic-matter content. Differences between LC₅₀ values in the high-organic-matter artificial soil and in an acid, low-organic-matter sandy soil were, however, not greater than a factor of 3–4. The results of this study therefore support the use of a well-defined artificial soil substrate for standardized earthworm toxicity tests.     

The utility of process-based models for simulating N2O emissions from soils: A case study based on Costa Rican coffee plantations

Soil moisture and gaseous N-flux (N₂O, N₂) dynamics in Costa Rican coffee plantations were successively simulated using a mechanistic model (PASTIS) and two process-based models (NGAS and NOE). Two fertilized (250 kg N ha⁻¹ y⁻¹) coffee plantations were considered, namely a monoculture and a system shaded by the N₂ fixing legume species Inga densiflora. In situ N₂O fluxes were previously measured in these plantations. NGAS and NOE used specific microbial activities for the soils. To parameterize NGAS, we estimated N mineralization via in situ incubations and the contribution of heterotrophic soil respiration to total soil respiration. Potential denitrification rates and the proportion of denitrified N emitted as N₂O were measured in the laboratory to define the values of NOE parameters, as well as nitrification rates and related N₂O production rates for parameterizing both models. Soil moisture and both NGAS and NOE N₂O fluxes were best modelled on an hourly time step. Soil moisture dynamics were satisfactorily simulated by PASTIS. Simulated N₂O fluxes by both NGAS and NOE (3.2 and 2.1 kg N ha⁻¹ y⁻¹ for NGAS; 7.1 and 3.7 kg N ha⁻¹ y⁻¹ for NOE, for the monoculture and shaded plantations respectively) were within a factor of about 2 of the observed annual fluxes (4.3 and 5.8 kg N ha⁻¹ y⁻¹, for the monoculture and shaded plantations respectively). Statistical indicators of association and coincidence between simulated and measured values were satisfactory for both models. Nevertheless, the two models differed greatly in describing the nitrification and denitrification processes. Some of the algorithms in the model NGAS were apparently not applicable to these tropical acidic Andosols. Therefore, more detailed information about microbial processes in different agroecosystems would be needed, notably if process-oriented models were to be used for testing strategies for mitigating N₂O emissions.     

Development of an alternative artificial soil for earthworm toxicity testing in tropical countries

The standard soil invertebrate toxicity tests developed by OECD and ISO use an artificial soil as the test substrate, which contains sphagnum peat as a component. This type of peat is not widely available. Investigation of possible alternative substrates using locally available materials therefore is vital for performing such ecotoxicity tests, particularly in the tropics. We studied the suitability of paddy husk (PH), saw-dust (SD), non-composted (NCCP) and composted coco peat (CCP) as a replacement for sphagnum peat. Artificial soil (AS) was prepared by mixing 70% sand and 20% kaolin clay with 10% PH, SD, NCCP or CCP. First, the reproduction potential of the earthworm Eisenia andrei was investigated in modified artificial soil (MAS) using the original OECD AS as the control. The number of juveniles produced in OECD AS, MAS_PH and MAS_CCP was not significantly different but it was significantly reduced (p < 0.05) in MAS_SD and MAS_NCCP. The toxicity of chlorpyrifos, carbendazim and carbofuran for E. andrei was determined to validate the substrates. The 28-day LC₅₀s for the three pesticides in original AS, MAS_CCP and MAS_PH were not significantly different, but the EC₅₀ for effects on reproduction in the MAS_PH was significantly lower (p < 0.05) compared to OECD AS and MAS_CCP. We conclude that composted coco peat might be a suitable replacement for sphagnum peat in AS for soil ecotoxicity studies.     

Short-term effects of an exceptionally hot and dry summer on decomposition of surface peat in a restored temperate bog

The restoration of drained peat bogs in Northwest (NW) Europe is an important task of soil protection, but needs to cope with warmer and drier summers. Our examination took place in the Pietzmoor bog (Schneverdingen, NW Germany) that had been drained for fuel peat extraction until the 1970s and rewetted since then. We determined carbon dioxide (CO₂) efflux in situ and in laboratory incubations. Also, we analyzed pore water for dissolved organic carbon (DOC), total and dissolved organic N (DON), nitrate (NO₃^–) and ammonium (NH₄⁺) concentration. In Schneverdingen, the summer 2003 was record-breaking hot (mean temperature June to August elevated > 3 K compared to long-term average) and dry (precipitation during the same period < 59% of long-term average). In July 2003, the water table in the Pietzmoor subsided to > 42 cm below the surface in July 2003, when in situ soil CO₂ efflux was up to 23.4 g m^–2 d^–1 compared to 15.7 g m^–2 d^–1 in September. Prior to March 2003, DOC concentrations in pore water were < 180 mg l^–1 and NH₄⁺ was the dominant fraction of mineral N. In July 2003, DOC concentration rose to 249 g l^–1, DON concentrations more than doubled, and NO₃^– became the dominant fraction of mineral N. Due to the increased future likelihood of hot and dry summers in NW Germany, peat bog restoration efforts need take care that a water table close to the surface is maintained.     

Ecophysiology of the cave isopod Mesoniscus graniger (Frivaldszky, 1865) (Crustacea: Isopoda)

Feeding biology and thermal adaptations of the terrestrial isopod Mesoniscus graniger were studied. M. graniger is a depigmented isopod mainly inhabiting cave systems, although it has also been reported in endogeic (soil) habitats. Physiological adaptations are expected to reflect the unique environmental characteristics of caves, including restricted food sources, and stable microclimate with temperatures not exceeding about 10 °C and high relative humidity. The M. graniger from Domica and Ardovská caves (Slovakian Karst) were investigated. We identified organic deposits with associated microorganisms as sources exploited by M. graniger and assessed how these might supply essential polyunsaturated fatty acids (PUFA) in its nutrition. Algae, fungi and bat guano were found as the most important potential resources of PUFA for isopods. Digestive enzymes amylase, trehalase, saccharase and maltase were confirmed in the whole body homogenates of isopods; neither cellulolytic activity nor activities against xylan, laminaran and lichenan were observed. Amylase, maltase and cellobiase activities were also observed in bacterial strains isolated and cultured from isopod midgut, and may account for the measured whole-animal activities. In an artificial temperature gradient, M. graniger selected temperature 3.5 ± 5.4 °C with lower and upper extremes of –1.5 and 18.5 °C. Respiration, as measured by VO₂, was almost independent of temperature between 5 and 10 °C, then increased between 10 and 30 °C. These ecophysiological measures are consistent with adaptation to a stenothermal environment.     

N2O and NO fluxes between a Norway spruce forest soil and atmosphere as affected by prolonged summer drought

Global change scenarios predict an increasing frequency and duration of summer drought periods in Central Europe especially for higher elevation areas. Our current knowledge about the effects of soil drought on nitrogen trace gas fluxes from temperate forest soils is scarce. In this study, the effects of experimentally induced drought on soil N₂O and NO emissions were investigated in a mature Norway spruce forest in the Fichtelgebirge (northeastern Bavaria, Germany) in two consecutive years. Drought was induced by roof constructions over a period of 46 days. The experiment was run in three replicates and three non-manipulated plots served as controls. Additionally to the N₂O and NO flux measurements in weekly to monthly intervals, soil gas samples from six different soil depths were analysed in time series for N₂O concentration as well as isotope abundances to investigate N₂O dynamics within the soil. N₂O fluxes from soil to the atmosphere at the experimental plots decreased gradually during the drought period from 0.2 to −0.0 μmol m⁻² h⁻¹, respectively, and mean cumulative N₂O emissions from the manipulated plots were reduced by 43% during experimental drought compared to the controls in 2007. N₂O concentration as well as isotope abundance analysis along the soil profiles revealed that a major part of the soil acted as a net sink for N₂O, even during drought. This N₂O sink, together with diminished N₂O production in the organic layers, resulted in successively decreased N₂O fluxes during drought, and may even turn this forest soil into a net sink of atmospheric N₂O as observed in the first year of the experiment. Enhanced N₂O fluxes observed after rewetting up to 0.1 μmol m⁻² h⁻¹ were not able to compensate for the preceding drought effect. During the experiment in 2006, with soil matric potentials in 20 cm depth down to −630 hPa, cumulative NO emissions from the throughfall exclusion plots were reduced by 69% compared to the controls, whereas cumulative NO emissions from the experimental plots in 2007, with minimum soil matric potentials of −210 hPa, were 180% of those of the controls. Following wetting, the soil of the throughfall exclusion plots showed significantly larger NO fluxes compared to the controls (up to 9 μmol m⁻² h⁻¹ versus 2 μmol m⁻² h⁻¹). These fluxes were responsible for 44% of the total emission of NO throughout the whole course of the experiment. NO emissions from this forest soil usually exceeded N₂O emissions by one order of magnitude or more except during wintertime.     

Intermediate tidal stress promotes the detritivore-mediated decomposition of Spartina litter

Saltmarshes, functionally important habitats in the marine–terrestrial ecotone that are regularly affected by tidal inundation, are mainly detritus-based in terms of fluxes of nutrients and energy. With respect to the mediating influence of saltmarsh detritivores on microbial colonisation of detritus and on decomposition processes, we tested whether the “intermediate disturbance hypothesis” (IDH) is also applicable to the effects of stress in this stressful environment. Decomposition experiments with litter of the cordgrass, Spartina anglica, and with terrestrial [Porcellio scaber (Isopoda)] and marine/semi-terrestrial [Orchestia gammarellus (Amphipoda)] detritivores as well as animal-free controls were carried out in an artificial saltmarsh system. Different daily flooding regimes served as experimental levels of stress. Both litter mass loss and microbial respiration were mostly higher under aquatic than under terrestrial conditions, no matter whether detritivores were present or not. Considering the intertidal zone, low to intermediate daily inundation rates resulted in increased microbial respiration and an increased influence of detritivores on litter mass loss in early stages of cordgrass decomposition with high rates of detritus mass loss, and intermediate tidal stress led to higher microbial cell counts throughout the entire experiment. Summarised over 3 months, regression analyses suggested that microbial activity and detritus mass loss show a trend towards highest values at low inundation rates and under permanent inundation, although microbial density was higher under longer daily inundation. Access to detritus by detritivores enhanced both litter mass loss and microbial respiration, especially in later decomposition stages, whereas microbial density was reduced by detritivores. In conclusion, we predict that overall the decomposition of cordgrass detritus in saltmarshes is promoted in the intermediate to high area of the intertidal zone with daily inundation of ca. 4–10 hours where both marine and terrestrial detritivores have access to promote decomposition processes through feeding and mediating microbial activity.     

Abundance of the earthworm Lumbricus terrestris in relation to subsurface drainage pattern on a sandy clay field

Subsurface drainage induces systematic spatial variability in soil properties which may be reflected in the abundance and distribution of soil organisms. We compared the population density of the deep burrowing earthworm Lumbricus terrestris L. above and between tile subdrains in 41 sample pairs on an eight hectare grass field. Above the drains the median number of  individuals was twice as high and their total fresh mass five times as high as between the drains (4.5 vs. 2.1 individuals m^-2  and 9.6 vs. 1.9 g m^-2, respectively). The mean difference (above drain – between drains) was 2.5 individuals m^-2  (95% CI = 1.0 to 4.0) and 6.6 grams m^-2 (95% CI = 3.6 to 9.6). The relatively larger difference in fresh mass was due to a high proportion of adult individuals above drains. One likely explanation for the pattern of abundance is that the lowered water table level near the drains provides an environment beneficial for the population growth of L. terrestris. Due to the role of L. terrestris burrows as flow paths of percolating water the observations may have implications on subdrain function.     

Assessing spatial variability of soil enzyme activities in pasture topsoils using geostatistics

The purpose of this study was to assess the spatial variability of the activity of three hydrolytic enzymes, i.e. urease activity (UAc), alkaline phosphatase activity (APAc), and arylsulfatase activity (ASAc), in pasture topsoils using geostatistics. Enzyme activities along a transect in a 1.35-ha pasture were determined using 77 soil samples from the upper 20 cm of soil. UAc varied from 101.0 to 182.7 μg N g⁻¹ soil h⁻¹; APAc varied from 1.56 to 3.62 μg p-nitrophenol g⁻¹ soil h⁻¹; and ASAc varied from 1.50 to 3.26 μg p-nitrophenol g⁻¹ soil h⁻¹. The linear models fit the best semivariogram models for UAc, APAc, and ASAc. Semivariograms for enzyme activities exhibited spatial dependence with ranges of influence of approximately 124.7 m.     

Adaptation of the enchytraeid toxicity test for use with natural soil types

Assessments of chemical toxicity to soil invertebrates have been traditionally performed in formulated Standard Artificial Soil, or in standard LUFA 2.2 natural soil. Physical and chemical properties of these standard soils often do not represent the diversity of properties of natural soils and can be inadequate surrogates of exposure conditions of soil biota in the field. We investigated performance of three species of the genus Enchytraeus (E. albidus, E. crypticus, E. luxuriosus) using soil types covering a wide range of European and North American soil properties. Results showed that adult survival and juvenile production by E. albidus and E. luxuriosus were inhibited in acidic soils with pH ≤ 5, while less acidic soils having properties within following ranges: 2.5–8.0% OM, 6–26% clay, and 4–80% sand, could sustain survival and reproduction at or near validity criteria levels of enchytraeid toxicity test ISO/16387. Performance of E. crypticus in North American soils having properties within following ranges: 1.2–42% OM, 1–29% clay, and 4.4–8.2 pH, met or exceeded all validity criteria. Data established in our studies can be used for amending the validity criteria of current ISO/16387 when used with E. crypticus and OECD soil.     

Spatial distribution of isopods in an oak–beech forest

Soil macroinvertebrates were studied in a Mediterranean-type forest on brown-pebble forest soils in southern Russia. At the site, 144 intact soil cores (76 cm² each) forming a grid of 24 × 6 units were taken in order to determine animal spatial distribution. Abundance of isopods was 166.3 ± 16.0 indiv. m^–2 and they constituted about 12% of the total macrofaunal abundance. Biomass of isopods was 3.5 g m^–2, or about 21% of the total biomass of macrofauna. Three woodlice genera (Armadillidium, Cylisticus, and Trachelipus) were found at the site. The two latter genera formed almost all (93%) of the isopod population. We found that spatial distribution of woodlice was heterogeneous: areas with 4–5 individuals per sample were neighboring those without animals. In order to study soil factors influencing isopod distribution in the brown-pebble forest soil, the size of a sample was artificially increased by combining adjacent sample units. Litter mass (r = 0.41) and loss on ignition (LOI) (r = –0.55) significantly influenced isopod distribution. Soil pH was near neutral (6.79), LOI was 8.39, and the water holding capacity was 70.9%. Pebbles comprised up to 84% of the sample's mass. Ca. 40 samples are recommended for estimation of isopod abundance in brown forest soil.     

Comparison of the effects of zinc nitrate-tetrahydrate and tributyltin-oxide on the reproduction and avoidance behavior of the earthworm Eisenia andrei in laboratory tests using nine soils

The aim of this contribution was to evaluate whether the sensitivity of the earthworm avoidance test is comparable to that of the earthworm reproduction test (standard test guidelines for both are available). The objective was to determine if relatively simple short-term tests are useful as an initial screening step for the environmental risk assessment (ERA) of potentially contaminated soils prior to performing long-term, elaborate tests. Therefore, the effects of two model substances, zinc nitrate-tetrahydrate and tributyltin-oxide (TBT-O) on the reproduction and the avoidance behavior of the earthworm Eisenia andrei were compared using Organization for Economic Co-operation and Development (OECD) artificial soil as well as eight natural soils, including LUFA St. 2.2 soil, covering a wide range of pH-values, organic matter content and texture. Almost all tests fulfilled the validity criteria defined in the two standard guidelines published by the International Organization for Standardization (ISO), despite the fact that the properties of natural soils differed clearly from those of OECD artificial soil. The median effective concentration (EC50) values estimated for zinc nitrate-tetrahydrate in 48-h avoidance tests and in 56-day reproduction tests were often similar when using the same soil (seven out of nine soils). However, in the case of TBT-O, the outcome was more complex: in two test soils the avoidance EC50 values were by a factor >3 higher than the reproduction EC50 values. In one of the test soils it was the other way around and the remaining soils showed comparable EC50 values in both tests. Summarizing the results obtained here and according to experiences reported in the available literature, the earthworm avoidance test may be recommended as an initial screening tool in the ERA of potentially contaminated soils. However, further research is needed to understand the factors that contribute to the difference in sensitivity between reproduction and avoidance tests.     

聚丙烯酰胺对蚯蚓的毒性效应

聚丙烯酰胺作为全球应用最广泛,用量最大的水处理剂,而其排放到环境中可能会对生态环境形成潜在的威胁。该研究在人工土壤条件下,通过急性和亚急性暴露试验研究了聚丙烯酰胺和丙烯酰胺对赤子爱胜蚓存活、生长和繁殖的影响,旨在评价聚丙烯酰胺和丙烯酰胺对蚯蚓的毒性效应。结果表明,聚丙烯酰胺和丙烯酰胺对蚯蚓的半致死剂量分别为大于2000和164.01?mg/kg,聚丙烯酰胺比丙烯酰胺毒性低;在急性和亚急性毒性暴露期内,聚丙烯酰胺对蚯蚓的存活和生长无显著影响;而当丙烯酰胺浓度大于100?mg/kg时即对蚯蚓的存活和生长产生显著的影响（P＜0.05）。聚丙烯酰胺和丙烯酰胺均对蚯蚓的繁殖能力有非常显著的影响（P＜0.05）。因此残留于污泥中的聚丙烯酰胺对环境有一定的潜在风险。     

Feeding activity of the earthworm Eisenia andrei in artificial soil

Quantitative information on the feeding activity of earthworms is scarce but this information is valuable in many eco(toxico)logical studies. In this study, the feeding activity of the compost worm Eisenia andrei is examined in artificial soil (OECD medium), with and without a high-quality food source (cow manure), and at two temperatures (10 and 20 °C). Methods are provided to estimate the most important parameters: gut load, selection of organic matter (OM), digestion efficiency, compaction, gut retention time, and fraction of manure in the diet. Lanthanides (Lu and Tm) were successfully used as inert markers in soil and manure, and we applied Bayesian statistics to analyse the data and fully capture the compounded uncertainty in the parameter estimates. Results show that the compost worm does not feed on soil indiscriminately but is able to select an OM-enriched diet from apparently homogeneous OECD medium. When manure is present on the soil surface, approximately three-quarters of the diet still consists of soil particles. The gut load of the worms was approximately 10% (dwt gut/wwt empty worm), varying little with the treatments. Unfortunately, the digestion efficiency could only be reliably estimated at 20 °C, and was approximately 40%. Temperature clearly affected feeding as a 10° temperature decrease nearly doubled the gut retention time (from 2.9 to 5.5 h), which corresponds to a two-fold decrease in feeding rate. The present data may be used to interpret toxicity and accumulation studies with E. andrei in OECD medium. However, care must be taken, as it seems possible that feeding is influenced by the size of the worm and subtle differences in experimental set-up.