Comparative Analysis of Ecophysiological Characteristics of Stephanodiscus hantzschii Grun. in the Periods of Its Bloom in Recreational Water Bodies

In the periods of summer and autumn bloom of the Stephanodiscus hantzschii Crun. in recreational water bodies, studies on the vertical distribution of chlorophyll a, its contents per unit biomass, efficiency in using photosynthetically active radiation (E_PhAR), and assimilative activity of microalgae were performed. The results confirmed the existence of two ecophysiological forms of St. hantzschii and provided evidence that both forms are typically autotrophic and can efficiently use low-intensity PhAR for photosynthesis.     

Anatomical Structure of Ectomycorrhiza in Abies sibirica Ledeb. and Picea obovata Ledeb. under Conditions of Forest Ecosystems Polluted with Emissions from Copper-Smelting Works

Changes in the anatomical characters of ectomycorrhiza in Siberian fir and Siberian spruce were studied in natural forests polluted with heavy metals (Cu, Zn, Cd, Pb, As, and Fe) and sulfur dioxide. As technogenic load increased, the total radius of mycorhiza terminals and plant roots included in them increased in the organic horizon and decreased in the mineral part of the soil. The absolute thickness of fungal mycorhiza caps and their relative contribution to the total volume of consuming organs increased under pollution. The observed responses were regarded as adaptive, aimed at compensating the adverse effects caused by technogenic pollution.     

The Phenomenon of Pseudoviviparity in Alpine and Arctomontane Grasses (DeschampsiaBeauv., FestucaL., and PoaL.)

It is known that pseudoviviparous plant taxa are most numerous in the Arctic and high mountain regions, where they sometimes account for a noticeable part of the local flora and play an important phytocenotic role. The complex of pseudoviviparous taxa is an interesting model for investigating the processes of hybridogenic speciation, as various mechanisms stabilizing the hybrid genetic systems proved to be effective in them. In particular, this concerns vast and taxonomically complex groups such as the genera Deschampsia, Festuca, and Poa.In this paper, published data on the taxonomy, chromosome numbers, and distribution of pseudoviviparous grasses in the Arctic regions and subarctic mountain systems are reviewed.     

Ecophysiological Responses of Larix sibiricaLedeb. and Pinus sibiricaDu Tour Undergrowth to Climate Change

The effects of probable climate change—an increase in atmospheric CO₂(by two times), air temperature, precipitation—on CO₂exchange and temperature dependence of net photosynthesis in the larch and Siberian stone pine undergrowth formed in the light larch forests of West Siberia were studied in chambers with an artificial climate. The change of the aforementioned ecological factors caused an increase in the temperature optima of photosynthesis and the range of optimum temperatures (in the case of Siberian stone pine, to a slightly greater degree). Therefore, the ranges of both species may broaden, and the Siberian stone pine can expand to the north, displacing larch tree stands.     

Development of a Test System for Assessing the Toxicity of Multicomponent Wastes Stored in the Natural Environment

A biological test system is proposed for assessing the toxicity of multicomponent wastes stored in the natural environment, with sewage sludge being used as an example. The principles of creating a test system and ranking the samples of multicomponent masses with respect to environmental hazard are discussed.     

On adaptations of trees and shrubs in the north of the Russian Far East

Specific ecological features of trees (Chosenia arbutifolia and Betula lanata) and shrubs (Pinus pumila and Duschekia fruticosa) at the northern limit of their distribution are compared. New biomorphological adaptations of these species under extreme conditions are described.     

Lipid peroxidation rates in <Emphasis Type="Italic">Taraxacum officinale</Emphasis> Wigg. and <Emphasis Type="Italic">Vicia cracca</Emphasis> L. from biotopes with different levels of soil pollution with heavy metals

The rates of lipid peroxidation (LPO) have been studied in Taraxacum officinale Wigg. (Asteraceae) and Vicia cracca L. (Fabaceae) from urban ecosystems with different levels of soil pollution with heavy metals (HMs), including Pb, Zn, Cu, and Cr. The former species responds to the increased HM contents by intensification of LPO processes, with their parameters correlating with the concentrations of Pb, Zn, and Cu in the soil. In the latter species from the same biotopes, conversely, LPO homeostasis remains actually undisturbed.     

Toxicity of copper in sewage sludge

Sewage sludge is a source of organic matter and nutrients, but a major obstacle for its recycling is that the municipal wastewater sludge has low but significant levels of contaminants. This investigation, on the acute toxicity of copper in sewage sludge, was conducted with three organisms, Daphnia magna, Lemna minor and Raphanus sativus (seeds). The toxicity of the leakage water from sewage sludge spiked with CuSO(4) was studied for 64 days. The toxicity increased during the first 8-16 days and then started to decrease. The first increase in toxicity was due to ammonia, but after 32 days, a dose-related effect of copper was found. After 64 days, L. minor had an EC50 of 3800 mg Cu/kg dw for 7 days growth inhibition, a LOEC of 3200 mg Cu/kg dw and a NOEC of 1600 mg Cu/kg dw. D. magna had an EC50 of 18100 mg Cu/kg dw (24-h immobility) and a NOEC of 12800 mg Cu/kg dw. Root elongation of R. sativus was reduced at 25600 mg Cu/kg dw. Both for Daphnia and Lemna, the pH of the leakage water had an effect of the toxicity. This means that chemical speciation and bioavailability is very important for the hazard assessment of copper in sludge and soil.     

Activity of glutathione S-transferase in Spodoptera exigua larvae exposed to cadmium and zinc in two subsequent generations

The aim of our study was to establish changes in activity of important in detoxification enzyme-glutathione S-transferase (GST): in alimentary tract, fat body and Malpighian tubules of Spodoptera exigua larvae being under cadmium and zinc exposure through the first as well as the second generation. There was registered enhancement of the enzyme activity in the fat body and the Malpighian tubules caused by zinc as well as its decrease in the Malpighian tubules under cadmium action. Amounts of metals in the alimentary tract were either several times higher than in the diet ingested by larvae or than in the fat body. Metal concentration in the fat body correlated with the level of the enzyme activity (positive correlation for zinc and negative for cadmium). The effect of metal action differentiated dependently on time exposition.     

The Root System of Larix sukaczewii Dyl. in the Polluted Environment of the Ufa Industrial Center

Russian Journal of Ecology -     

Toxicities and tolerances of Cd, Cu, Pb and Zn in a primary producer (Isochrysis galbana) and in a primary consumer (Perna viridis)

Studies on toxicities and tolerances of cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) in the brown alga Isochrysis galbana and in the green-lipped mussel Perna viridis were conducted by short-term bioassays using endpoints growth production and mortality, respectively. The 5-day EC(50) and 24-h LC(50) of these heavy metals were determined in the brown alga and mussel, respectively. The EC(50) values calculated for the alga were 0.74 mg/l for Cd, 0.91 mg/l for Cu, 1.40 mg/l for Pb and 0.60 mg/l for Zn. The LC(50) values for the mussels were 1.53 mg/l for Cd, 0.25 mg/l for Cu, 4.12 mg/l for Pb and 3.20 mg/l for Zn. These LC(50) values were within the concentration ranges as reported by other authors who used P. viridis as the test organism. Based on these EC(50) and LC(50) values, the alga was most sensitive to Zn, followed by Cd, Cu and Pb while the mussel was most sensitive to Cu, followed by Cd, Zn and Pb. Differences in the trophic levels, metal handling strategies, biology and ecology of the primary producer (brown alga) and the primary consumer (mussel) are believed to be the plausible causes for the different toxicities and tolerances of the metals studied.     

Structure and formation of conifer stands in the upper timberline ecotone on the North Chuya Ridge,Central Altai

The structure of Siberian stone pine (Pinus sibirica Du Tour.) and Siberian larch (Larix sibirica Ledeb.) stands and specific features of their formation have been studies in the forest-tundra ecotone on the North Chuya Ridge (2235–2475 m a.s.l.). Changes in the structure of these stands along the transition from the upper boundary of closed forests to the high-mountain tundra have proved to have an ambiguous pattern. Both tree species form mixed clusters of similar-aged trees in the lower part of the ecotone but grow singly, in scatters, in its upper part. The formation of conifer stands (tree clusters) in the lower part of the ecotone, on the slopes of the Aktru River valley, began during climate warming in the second half of the 19th century. The expansion of confers to its upper part took place markedly later, in the early 20th century (Siberian larch) or even in the 1930s (Siberian stone pine).     

Experience in using ecological phytoindication scales for revealing unfavorable factors at the boundary of species distribution

The ecological phytoindication scales proposed by Tsyganov (1983) were used for characterizing biotopes at the northern limit of the distribution of three nemoral species:Ajuga reptans, Asarum europaeum, andPulmonaria obscura. Regional ecological amplitudes of the model species were determined. The environmental factors approaching the lower limit of species amplitudes in Tsyganov's scales were classified as unfavorable.     

Competition between the Rotifers Brachionus patulusand Euchlanis dilatata:Effect of Algal Food Level and Relative Initial Densities of Competing Species

We tested the effect of different algal (Chlorella vulgaris) levels and inoculation densities on the outcome of competition between the rotifers Euchlanis dilatata and Brachionus patulus. The experiment was performed in 36 transparent jars, each with 20 ml of a test medium. We used three Chlorella levels: 0.75 × 10⁶, 1.5 × 10⁶, and 3.0 × 10⁶ cells/ml. For each algal level, we used five different ratios of initial inoculation density. The population growth experiments were terminated after 19 days. Regardless of inoculation densities, an increase in food level resulted in an increased population abundance of both rotifer species. Regardless of food concentration,E. dilatatawas able to outcompete B. patulus at all inoculation densities when grown together. However, when Chlorella was offered in low concentration and there was a higher ratio of Brachionus to Euchlanis at the onset of the experiment, both rotifer species coexisted in more or less equal densities until the end of the experiments. When the food level was enhanced, E. dilatata totally eliminated B. patulus. The rate of population growth ranged from 0.002 to 0.578 for B. patulus and from 0.006 to 0.447 for E. dilatata. The results are discussed with respect to the factors influencing the outcome of competition between species.     

Proliferative Activity of Corneal Epithelium and Specific Features of Morphogenesis in Postmetamorphic Rana arvalisNilss. in Urbanized Areas

The mitotic activity and sizes of corneal epithelial cells in postmetamorphic Rana arvaliswere studied in the populations exposed to different degrees of anthropogenic impact in the city of Yekaterinburg. The studies were conducted at the initial stages of frogs' terrestrial life in three consecutive years. Mitotic activity exhibited a slight positive correlation with the liver index, which indirectly reflects the general metabolic rate in young frogs. The combined estimation of proliferative activity, epithelial cell size, and relative liver weight had the highest information value. There was a relationship between the mitotic index and liver index in young frogs from habitats with the highest level of anthropogenic transformation. This indicates that morphogenesis is well-balanced and is likely to decrease the probability of morphological abnormalities in frogs developing in the unstable environment. This physiological property allows the populations to exist and reproduce in urbanized areas.     

Effect of Flavonoids on the Ecology of Enterobacteria

The effect of flavonoids, natural plant metabolites, on the growth and viability of enterobacteria was studied using S. typhimurium and E. coli strains defective in some components of the DNA repair system. The minimal inhibitory concentrations of several flavonoids were measured. These agents were shown to have a weak bactericidal and a marked bacteriostatic effect, the latter increasing under anaerobic conditions. It is proposed that the mechanism of the bacteriostatic action of flavonoids is based on topoisomerase II inhibition. On the basis of these results, the ability of flavonoids to differentially suppress bacterial growth and their probable influence on the ecology of microorganisms (the formation, species composition, and ecological balance of natural microbial communities) are discussed.