Uptake of 203Hg++ and 115 mCd++ by Chlamydomonas reinhardi under various conditions

The uptake of radioactively labeled mercury and cadmium ions by living and dead cells of Chlamydomonas reinhardi WT⁺ was measured at 25 °C under minimal and optimal conditions (dark/nitrogen or light/air, respectively). In each case, incorporation was completely independent of external energy. Living and dead cells incorporated almost the same amount of the added heavy metal ions; after about 4 to 8 hours, saturation was obtained. Furthermore, the distribution of mercury in the system of algea/culture medium/gas phase and the amount of mercury and cadmium adsorbed by cells were studied.     

Study on Agriculture Decision-Makers Behavior on Sustainable Energy Utilization

Phytomass cultivation for energy use is increasingly popular in Europe for high profits guaranteed by subsidy. Although public interest in ecology is on an increasing level, direct combustion is still preferred even though scholars have been warning about formations of hazardous compounds for a long-time. However, the reduction of subsidies would negatively affect an already bad situation in Czech agriculture, since most farmers became fully dependent on subsidies due to quotas, restrictions, and other unequal business conditions in European Union. It was proved in a commercial scale that an alternative phytomass energy utilizing technology consisting of steam explosion and subsequent anaerobic fermentation may be run solely on the waste heat without any further addition of chemicals. Behavior analysis of present and future agriculture decision-makers showed that none of the farmers who visited the facility cared about ecological consequences. On the other hand, ost students from the Faculty of Agriculture and the Faculty of the Economy answered the questionnaire with higher environmental responsibility. We assume this is caused by high average age of farmers in Czech Republic who are more aware of the ongoing economical difficulties and perceive differently the risk of higher acquisition costs.     

Hysteresis in Reversal of Central European Mountain Lakes from Atmospheric Acidification

Extremely high emissions of S and N compounds in Central Europe (both 280 mmol m^-2 yr^-1) declined by 70and 35%, respectively, during the last decade. Decreaseddeposition rates of SO₄ ^-2, NO₃ ^-, and NH₄ ⁺ in the region paralleled emission declines. The reduction in atmospheric inputs of S and N to mountain ecosystemshas resulted in a pronounced reversal of acidification in the Tatra Mountains and Bohemian Forest lakes. Between the 1987–1990and 1997–1999 periods, concentrations of SO₄ ^-2 and NO₃ ^- decreased (average ± standard deviation) by 22±7 and 12±7 mol L^-1, respectively, in theTatra Mountains, and by 19±7 and 15±10 mol L^-1, respectively, in the Bohemian Forest. Their decrease was compensated in part (1) by a decrease in Ca²⁺ + Mg²⁺ (17±7 mol L^-1) and H⁺ (4±6 mol L^-1), and an increase in HCO₃ ^-(10±10 mol L^-1) in the Tatra Mountains lakes, and (2) by a decrease in Al (7±4 mol L^-1), Ca²⁺ + Mg²⁺ (9±6 mol L^-1), and H⁺ (6±5 mol L^-1), in Bohemian Forest lakes. Despite the rapid decline in lake water concentrations of SO₄ ^-2 and NO₃ ^- in response to reduced S and N emissions, their present concentrations in some lakes are higher than predictionsbased on observed concentrations at comparable emission rates during development of acidification. This hysteresis in chemical reversal from acidification has delayed biological recovery of the lakes. The only unequivocal sign of biological recovery hasbeen observed in erné Lake (Bohemian Forest) where a cladoceran species Ceriodaphnia quadrangular has recentlyreached its pre-acidification abundance.     

Significance of spectral and temporal call parameters in the auditory communication of male grass frogs

Summary During the spawning period, male grass frogs (Rana temporaria L.) frequently produce short and long territorial calls in addition to mating calls. The calls differ in mean pulse number, duration, and pattern of amplitude modulation. Experiments in which recorded natural calls are played back reveal that male grass frogs are capable of discriminating the different conspecific calls. A male frog stimulated by mating calls always responds by producing mating calls in greater numbers (Fig. 3). Territorial calls presented at low intensity also cause an increase in the mating-call rate (Fig. 4), but at high intensity they clicit territorial calls and turning toward the loudspeaker. A combination of short and long territorial calls was especially effective in eliciting the phonotaxis response. As play-back experiments with simulated calls show, the carrier frequency and the pulse repetition rate are particularly important cues for recognition of conspecific calls (Fig. 5). A simulated call with a 400-Hz carrier frequency (the dominant frquency of the mating call) is just as effective as the natural call with the complete frequency spectrum (Fig. 3), whereas a 1100-Hz simulated call is ineffective (Fig. 5). The chief factors in discrimination among the conspecific calls are the call repetition rate and probably the amplitude and frequency modulation. Changes in the duration of the calls had little effect (Fig. 6). The available evidence suggests that the mating call has a reciprocally stimulating action on males in a chorus, whereas the territorial calls experess aggressiveness and give warning to other males.     

Biodiversity, distributions and adaptations of Arctic species in the context of environmental change

The individual of a species is the basic unit which responds to climate and UV-B changes, and it responds over a wide range of time scales. The diversity of animal, plant and microbial species appears to be low in the Arctic, and decreases from the boreal forests to the polar deserts of the extreme North but primitive species are particularly abundant. This latitudinal decline is associated with an increase in super-dominant species that occupy a wide range of habitats. Climate warming is expected to reduce the abundance and restrict the ranges of such species and to affect species at their northern range boundaries more than in the South: some Arctic animal and plant specialists could face extinction. Species most likely to expand into tundra are boreal species that currently exist as outlier populations in the Arctic. Many plant species have characteristics that allow them to survive short snow-free growing seasons, low solar angles, permafrost and low soil temperatures, low nutrient availability and physical disturbance. Many of these characteristics are likely to limit species' responses to climate warming, but mainly because of poor competitive ability compared with potential immigrant species. Terrestrial Arctic animals possess many adaptations that enable them to persist under a wide range of temperatures in the Arctic. Many escape unfavorable weather and resource shortage by winter dormancy or by migration. The biotic environment of Arctic animal species is relatively simple with few enemies, competitors, diseases, parasites and available food resources. Terrestrial Arctic animals are likely to be most vulnerable to warmer and drier summers, climatic changes that interfere with migration routes and staging areas, altered snow conditions and freeze-thaw cycles in winter, climate-induced disruption of the seasonal timing of reproduction and development, and influx of new competitors, predators, parasites and diseases. Arctic microorganisms are also well adapted to the Arctic's climate: some can metabolize at temperatures down to -39 degrees C. Cyanobacteria and algae have a wide range of adaptive strategies that allow them to avoid, or at least minimize UV injury. Microorganisms can tolerate most environmental conditions and they have short generation times which can facilitate rapid adaptation to new environments. In contrast, Arctic plant and animal species are very likely to change their distributions rather than evolve significantly in response to warming.