A. D. Pokarzhevskii

Metal concentrations in soil and invertebrates in the vicinity of a metallurgical factory near Tula (Russia).

Summary To investigate the effects of emissions from a large metal works near Tula in the Russian Federation, we measured concentrations of iron, manganese, zinc, copper, nickel, lead and cadmium in soil, litter and invertebrates at four sampling sites at different distances from the factory. The sites were located in woodlands in the bed of the Voronka river, near the town of Kosaya Gora in the district of Tula. Additional soil properties (organic matter content, clay content, water holding capacity, Ca, Mg, N, P, and pH) were measured that could explain differences in the bioavailability of the metal burdens. It appeared that the factory is a source of Fe, Mn, Zn, Cu, Ni and Pb. One of the sampling sites had a high nitrogen content in the litter due to emissions from a fertilizer plant in the area. Most of the metal contamination was limited to the immediate surroundings and did not extend beyond a distance of 5 km. Only the site close to the factory can be considered as polluted, however, background concentrations of metals in the Tula area seem to be significantly lower than in present Western European soils and a reference system still has to be developed. Exchangeable metal concentrations (0.01 M CaCl 2 extracts from soil) were very low and were not correlated with the total concentrations, indicating low bioavailability of the pollution. At the most polluted site, concentrations of all metals were positively correlated with each other; correlations decreased with increasing distance. Metal concentrations in soil were often negatively correlated with organic matter content, especially so for nickel. Metal concentrations in invertebrates showed considerable variation between individual species, however, some general patterns were obvious. Concentrations were high in earthworms, oribatid mites and carabid beetles, and low in springtails, centipedes and spiders. There was no relationship between the trophic position of a species and its metal accumulating ability. Iron concentrations in invertebrates at the polluted site were a factor of 2 to 4 higher than at the most remote (reference) site; for zinc and copper the internal concentrations were also elevated, but to a lesser extent than the soil concentrations. The data illustrate the extremely complicated relationship between metal residues in invertebrates and metal concentrations in soil. For most of the saprophageous and predatory arthropods studied total concentrations nor exchangeable concentrations in soil are good predictors; species-specific feeding mechanisms and metal physiologies seem to be the main determinants.

Amino acids in earthworms: are earthworms ecosystemivorous?

Abstract Amino acid contents were studied in eight earthworm species ( Lumbricus rubellus, L. terrestris, Nicodrilus roseus, N. caliginosus, Dendrobaena octaedra, Eisenia nordenskioldi, Octolasium lacteum, Drawida ghilarovi ), plant litter and soil. There are considerable differences in the content of essential amino acids between earthworms and their food (for most amino acids, one order of magnitude; for methionine, up to two orders of magnitude). Methionine stores in litter are lower than in earthworm biomass. Flows of essential amino acids through earthworm populations with consumed plant residues and soil are only three times higher than their content in the biomass, except methionine. The flow of methionine is only half its content in the biomass. There are no additional amino acid sources for earthworms but other soil animals and microorganisms. It is difficult to imagine that earthworms are carnivorous in temperate zone soils but with litter and soil they do consume microorganisms and small animals. Bacteria and protozoa, fungi and mesofauna dwell in other ecosystems than earthworms. Bacteria, Protozoa, Rotatoria, Tardigrada, and nematodes form ecosystems connected with water films in soil. Fungi, microarthropods and other small animals form ecosystems of soil and litter pores and gaps. Earthworms dwell in soil as a whole ecosystem. When they consume soil and litter they consume small ecosystems. Consumed bacterial populations also develop in their gut and are among the main sources of essential amino acids for earthworms. These bacteria form the gut ecosystem too. Hence earthworms are ecosystemivorous not saprovorous animals.

Microbial links and element flows in nested detrital food-webs

Summary Microbial links are obligate in any food chain in soil, because detritivorous animals derive essential amino acids and other resources from microorganisms. To degrade recalcitrant substrates such as cellulose, soil animals do not produce their own cellulase, but they use cellulases derived from gut microorganisms. We argue that in detrital food-webs, carbon (energy) is usually not a limiting factor. Other elements, for example nitrogen and phosphorus, are present in ratios (relative to carbon) which are lower in the food than in the animal itself, and are more likely to be limiting. This implies that we need to consider the dynamic stoichiometry of N, P and C in the food-web and we cannot assume a fixed ratio between the three elements. In addition, detrital food-webs consist of communities at three different scales. The bacteria-algae-Protozoa compartment is nested inside the fungi-microarthropod compartment and this is in turn is contained within the earthworm-rhizosphere compartment. Animals of the higher levels consume communities of the lower levels as a whole. Present approaches for the structure of detrital food-webs do not take this nested structure into account. Our hierarchical concept of food-web structure may explain why soil pollutants that are not directly toxic to animals, may still affect the functioning of soil animals, either through deterioration of their food resources or through effects on internal food-chains.

Agar as a medium for removing soil from earthworm guts

Abstract Earthworms were kept on a water–agar gel for 96 h at 20°C, after that time all soil had been voided from their guts. Earthworms treated in this way may be used for soil-free chemical analysis, as required in biomonitoring programmes for soil contamination.

Trophic Structure of Ecosystems and Ecotoxicology of Soil Organisms

Studies on the ecotoxicology of soil organisms have led to the revision of views on the trophic structure of ecosystems. It was found that the microbial link is obligatory and controls the migration of toxicants and their effects in the food chain. Differences in effects are accounted for by both the physiological stability of organisms and their affliation with relatively independent and biogeochemically closed ecosystems differing in their spatiotemporal scales. The latter form a hierarchical three-level structure: ecosystems of unicellular organisms—ecosystems of small multicellular organisms—the ecosystem of large multicellular organisms, or of biogeocenosis. Trophic networks within the structure are united by ecosystemophagy as the type of feeding of large multicellular organisms, and this accounts for the importance of the latter as indicators of long-term changes in a biogeocenosis.

Differences in responses of herpetobionts and geobionts to impact from the Kosogorsky Metallurgical Plant (Tula region, Russia)

The influence of the Kosogorsky Metallurgical Plant (KMP; Tula region, Russia) on the abundance and biodiversity of carabid beetles and soil macrofauna and on the trophic activity of soil biota was studied. Metal concentrations in the impact plot were many times higher than those in the control plot located on the same transect. As the transect approached KMP, both the abundance of soil invertebrates (geobionts) and trophic activity of the soil biota remained unchanged, whereas the abundance and diversity of carabids (herpetobionts) decreased drastically. It is suggested that the impact of the KMP on herpetobionts is accounted for by modification of the structure of ecosystems and that herpetobiontic and geobiontic groups of the macrofauna respond differently to this impact because of differences in the ecological mechanisms of population response.

Spatial Distribution of Animals and Variation in Their Trophic Activity Measured Using the Bait-Lamina Test in Sod-Podzolic Soil under a Spruce Forest

The mode of spatial distribution of soil animals and their trophic activity was studied in the sod-podzolic soil under a spruce forest. At the “test point” level, no apparent relationship between the distribution of soil animals and physicochemical characteristics of the soil was observed. The patterns of distribution of detritophages and the trophic activity (measured using the bait-lamina test) were similar. The perforation of laminae in the bait-lamina test resulted from the trophic activity of both micro- and mesofauna.

Global Radioactive Contamination Background in Terrestrial Ecosystems 13 Years after the Chernobyl Accident

The contents of 137Cs in the soil, plant, and animal samples collected in the ecosystems of protected areas from the White Sea to the Black Sea in 1999 slightly differ from those in the period between 1980 and 1984. As a result of global fallout after the Chernobyl accident, the content of radioactive cesium in the soil has increased only on the territory of the Biological Station of Moscow State University at the White Sea, whereas that in the litter and plants has increased in virtually all areas studied. The isotope content in animals is actually equal to that recorded between 1980 and 1984. The mobility of 137Cs in the soil–plant link has increased, which may be due to fallout after the accident. The duration of a complete radionuclide cycle in ecosystems decreases from 10 half-life periods in northern regions to 2.5 half-life periods in the southern regions. The Chernobyl disaster has caused no significant changes in the global radioactive background in the European part of the Russian Federation.

Evaluation of Winter Activity of Soil Invertebrates

Winter in boreal and moderate climate is regarded as a critical period for soil organisms because of the detrimental effects of low temperature [1, 2]. However, microarthropods were found to move to soil surface covered with snow and to snow surface during periods of thawing and even at negative temperatures [3–7]. In some cases, this activity is accompanied by food consumption. Under the conditions of environmental pollution and low temperature, the trophic activity of the animals may cause catastrophic reduction of their populations. This may be regarded as a possible ecological mechanism of the toxicant effect on the soil biota [8]. These effects are usually disregarded in bioindicator and ecotoxicological studies [9]. However, the extent of these effects depends on the dynamics and duration of behavioral activity of animal populations in winter, which has not been quantitatively monitored so far. The bait-lamina test suggested in [10] allows the trophic activity of soil invertebrates to be monitored [11] and population size of soil invertebrates to be evaluated under field condition even in winter. Therefore, this method provides the opportunity to determine the possible effect of this activity on the state of soil invertebrate populations.

Life-cycle length determines the differences in sensitivity to toxicants between enchytraeid species.

Differences in sensitivity to toxicants between species of soil organisms depend on their exposure to pollutants. Therefore, unstable organic compounds are not considered hazardous to those soil organisms whose life cycles are considerably longer than the half-lives of the toxicants. On the other hand, short-cycle animals are often resistant to stable pollutants, such as radionuclides, because the doses received by them during the period “from egg to egg” are too small to cause serious disturbances in populations [1, 4]. Thus, the ratio between the time of toxicant degradation in soil and the length of the life cycle of the animal should affect not only physiological and biochemical mechanisms of resistance [5–8], but also the expression of pollution effects.