Oxidation of gas mixtures containing dimethyl sulfide, hydrogen sulfide, and methanethiol using a two-stage biotrickling filter

A biofiltration technique was developed for removing a mixture of hydrogen sulfide (H2S), methanethiol (MeSH), and dimethyl sulfide (Me2S) from waste gases. Since H2S, especially at high concentrations, disturbs the removal of Me2S, two biotrickling filters with different microbes and operating pH levels were connected in series to create a two-stage system. Different loads of these gases were studied in order to determine their impact on the removal capacity of the system. The microbial consortia for these filters were enriched from the sludge of a Finnish refinery with bubbling H2S or Me2S. Acclimation for Me2S took 2 weeks, though no acclimation time was needed for the other gases. The first filter, at a pH of 2, removed most of the H2S and some of the MeSH and Me2S. The second filter, at a pH of approximately 6.5, removed the rest of the MeSH and most of the Me2S. The total maximum loads of the whole two-stage biotrickling filter were 1150 g/m3/day for H2S-S (suffix S indicates the results are counted as sulfur amounts), 879 g/m3/day for Me2S-S, and 66 g/m3/day for MeSH-S treated in a gas mixture. The average removal efficiencies for all gases tested were 99% or higher.     

Factors affecting mass transfer limited biodegradation in saturated porous media

Microbial degradation rates in the subsurface are not only limited by the physiological capacity of the organisms, but also by inefficient supply of nutrients to the microbes. Although mass transfer limitation of biodegradation in the subsurface has been postulated for years, experimental evidence is still scarce. In the column experiments described here, diffusive transport of 4-nitroanisole from the bulk solution to cells of Rhodococcus opacus strain AS2 immobilized on glass beads or sand appeared to be responsible for the slow transformation rates observed. Assuming steady state, we applied a coupled transformation/transport equation to these data (Best equation) and apparent bead-related mass transfer coefficients were found to increase in proportion to the surface area covered with bacteria. This implies that mass transfer coefficients for individual cells remained constant. In an idealized oligotrophic environment where cells are only loosely clustered and do not shield each other, we would therefore expect biodegradation rates to be independent from the longitudinal distribution of the total biomass along a given flow path. Moreover, apparent mass transfer coefficients increased with the grain size of the column fillings, but did not change upon varying the flow rate. With a limiting external transport step, overall transformation fluxes do not become saturated at concentrations as low as predicted for Michaelis-Menten-type kinetics. Mass transfer limitation thus offers a justification for the common assumption that biodegradation rates in the subsurface follow first order kinetics in a wide concentration range.     

Century Perspective of Heavy Metal Use in Urban Areas. A Case Study in Stockholm

The inflow and stock (amount in use) of heavy metals (cadmium(Cd), chromium (Cr), copper (Cu), lead (Pb), mercury (Hg), nickel (Ni) and zinc (Zn)) in goods in 1995 have been quantifiedin the anthroposphere of Stockholm, Sweden. Statistics on national, regional and local level were used. Contacts were established with representatives from production and constructionin the industrial sector and with authorities. The results show that the stock of Cd is 0,2 kg per capita. For the other heavymetals the corresponding result per capita is: Cr 8, Cu 170, Hg 0,01, Ni 4, Pb 73 and Zn 40 kg. The inflow varies between2–8%of the stock indicating the importance of the stock. The lowestlevels are for Cu and Pb. Heavy metal levels in solid waste are high, between 15–45% of the amount in the inflow (Hg excluded), the lowest values were for Cu and Pb. Thus, recyclingis incomplete. Long life expectancy goods form the majority of the stock but there is a tendency that short life expectancy goods increase their importance in the inflow. Concealedgoods are also more frequent in inflow than in the stock.     

Mass effects mediate coexistence in competing shrews

Recent developments in metacommunity theory have raised awareness that processes occurring at regional scales might interfere with local dynamics and affect conditions for the local coexistence of competing species. Four main paradigms are recognized in this context (namely, neutral, patch-dynamics, species-sorting, and mass-effect), which differ according to the role assigned to ecological or life-history differences among competing species, as well as to the relative time scale of regional vs. local dynamics. We investigated the patterns of regional and local coexistence of two species of shrews (Crocidura russula and Sorex coronatus) sharing a similar diet (generalist insectivores) over four generations, in a spatially structured habitat at the altitudinal limit of their distributions. Local populations were small, and regional dynamics were strong, with high rates of extinction and recolonization. Niche analysis revealed significant habitat differentiation on a few important variables, including temperature and availability of winter resting sites. In sites suitable for both species, we found instances of local coexistence with no evidence of competitive exclusion. Patterns of temporal succession did not differ from random, with no suggestion of a colonization-competition trade-off. Altogether, our data provide support for the mass-effect paradigm, where regional coexistence is mediated by specialization on different habitat types, and local coexistence by rescue effects from source sites. The strong regional dynamics and demographic stochasticity, together with high dispersal rates, presumably contributed to mass effects by overriding local differences in specific competitive abilities.     

Testing the evolution of increased competitive ability (EICA) hypothesis in a novel framework

The "evolution of increased competitive ability" (EICA) hypothesis proposes that escape from natural enemies, e.g., after transcontinental introductions, alters the selection regime because costly defenses no longer enhance fitness. Such an evolutionary loss of defenses enables resources to be directed toward growth or other traits improving performance. We tested the EICA hypothesis in a novel framework in which the natural enemy is the traveler that follows its widespread host by accidental or deliberate (biocontrol) introductions. In a greenhouse experiment we used populations of Senecio vulgaris from North America, Europe, and Australia that differ in the history of exposure to the rust fungus Puccinia lagenophorae. Contrary to what is predicted by EICA, we found no evidence for increased levels of resistance to the rust fungus in plant populations with a longer history of rust exposure (Australia). Similarly, there was no evidence for reduced fecundity in these populations, although vegetative vigor, measured as secondary branching and growth rate, was lower. The maintenance of high rust resistance in populations with no (North America) or only a short history (Europe) of rust exposure is surprising given that resistance seems to incur considerable fitness costs, as indicated by the negative association between family mean resistance and fitness in the absence of disease observed for all three continents. The comparison of population differentiation in quantitative traits with estimates of differentiation in amplified fragment length polymorphic (AFLP) markers suggests that a number of fitness-related traits are under divergent selection among the studied populations. The proposed framework to test changes in the evolutionary trajectory underlying EICA can be employed in an expanded range of systems. These may include investigations on a cosmopolitan weed or crop when an antagonist is expanding its geographic range (such as our study), studies along a chronosequence of introduction time with expected increasing accumulation of natural enemies over time, or comparisons between introduced plant populations that differ in exposure time to biocontrol organisms.     

Transient dynamics of pelagic producer-grazer systems in a gradient of nutrients and mixing depths

Phytoplankton-grazer dynamics are often characterized by long transients relative to the length of the growing season. Using a phytoplankton-grazer model parameterized for Daphnia pulex with either flexible or fixed algal carbon:nutrient stoichiometry, we explored how nutrient and light supply (the latter by varying depth of the mixed water column) affect the transient dynamics of the system starting from low densities. The system goes through an initial oscillation across nearly the entire light-nutrient supply space. With flexible (but not with fixed) algal stoichiometry, duration of the initial algal peak, timing and duration of the subsequent grazer peak, and timing of the algal minimum are consistently accelerated by nutrient enrichment but decelerated by light enrichment (decreasing mixing depth) over the range of intermediate to shallow mixing depths. These contrasting effects of nutrient vs. light enrichment are consequences of their opposing influences on food quality (algal nutrient content): algal productivity and food quality are positively related along a nutrient gradient but inversely related along a light gradient. Light enrichment therefore slows down grazer growth relative to algal growth, decelerating oscillatory dynamics; nutrient enrichment has opposite effects. We manipulated nutrient supply and mixing depth in a field enclosure experiment. The experimental results were qualitatively much more consistent with the flexible than with the fixed stoichiometry model. Nutrient enrichment increased Daphnia peak biomass, decreased algal minimum biomass, decreased the seston C:P ratio, and accelerated transient oscillatory dynamics. Light enrichment (decreasing mixing depth) produced the opposite patterns, except that Daphnia peak biomass increased monotonously with light enrichment, too. Thus, while the model predicts the possibility of the "paradox of energy enrichment" (a decrease in grazer biomass with light enrichment) at high light and low nutrient supply, this phenomenon did not occur in our experiment.     

Species-specific defense strategies of vegetative versus reproductive blades of the Pacific kelps <Emphasis Type="Italic">Lessonia nigrescens</Emphasis> and <Emphasis Type="Italic">Macrocystis integrifolia</Emphasis>

Chemical defense is assumed to be costly and therefore algae should allocate defense investments in a way to reduce costs and optimize their overall fitness. Thus, lifetime expectation of particular tissues and their contribution to the fitness of the alga may affect defense allocation. Two brown algae common to the SE Pacific coasts, Lessonia nigrescens Bory and Macrocystis integrifolia Bory, feature important ontogenetic differences in the development of reproductive structures; in L. nigrescens blade tissues pass from a vegetative stage to a reproductive stage, while in M. integrifolia reproductive and vegetative functions are spatially separated on different blades. We hypothesized that vegetative blades of L. nigrescens with important future functions are more (or equally) defended than reproductive blades, whereas in M. integrifolia defense should be mainly allocated to reproductive blades (sporophylls), which are considered to make a higher contribution to fitness. Herein, within-plant variation in susceptibility of reproductive and vegetative tissues to herbivory and in allocation of phlorotannins (phenolics) and N-compounds was compared. The results show that phlorotannin and N-concentrations were higher in reproductive blade tissues for both investigated algae. However, preferences by amphipod grazers (Parhyalella penai) for either tissue type differed between the two algal species. Fresh reproductive tissue of L. nigrescens was more consumed than vegetative tissue, while the reverse was found in M. integrifolia, thus confirming the original hypothesis. This suggests that future fitness function might indeed be a useful predictor of anti-herbivore defense in large, perennial kelps. Results from feeding assays with artificial pellets that were made with air-dried material and extract-treated Ulva powder indicated that defenses in live algae are probably not based on chemicals that can be extracted or remain intact after air-drying and grinding up algal tissues. Instead, anti-herbivore defense against amphipod mesograzers seems to depend on structural traits of living algae.     

Moosmonitoring als Spiegel der Landnutzung?

Goal, Scope and Background

The study was conducted to test the hypothesis that the regional variability of nitrogen (N) and metal accumulations in terrestrial ecosystems are due to historical and recent ways of land use. To this end, in two regions of Central Europe the metal and N accumulations in both regions should be examined by comparative moss analysis. The regions should be of quantitatively specified representativity for selected ecological characteristics of Europe. Within both regions these characteristics should be covered by the sites where the moss samples were collected. The number of samples should allow for geostatistical estimation of the measured nitrogen and metal loads.

Methods

The two regions of investigation were selected according to an ecological land classification of Europe which was computed by classification trees. Within each of both research areas the sampling points were localized according to the areas occupied by the ecologically defined land classes. The sampling and chemical analysis of mosses was conducted in accordance with an appropriate UNECE guideline by means of ICP-MS (metals) and combustion analysis (N). The quality of measurements was assured using certified reference materials. The differences of deposition loads were tested for statistical significance with regard to time and space. Variogram analysis was used to examine and model the spatial autocorrelation function of the measurements. Ordinary kriging was then applied for surface estimations.

Results

By use of the ecological regionalisation of Europe the Weser-Ems Region (WER) and the Euro Region Nissa (ERN) were selected for investigation. The sampling sites represent quite well the natural landscapes and the land use categories of both regions. The measurement values corroborate the decline of metal accumulation observed since the beginning of the European Mosses Monitoring Survey in 1990. The metal loads of the mosses in the ERN exceed those in the WER significantly. The opposite holds true for the N concentrations: those in the WER are significantly higher than those in the ERN.

Discussion

The decrease of heavy metal emissions is correlated with lowered deposition and accumulation rates in terrestrial ecosystems. The accumulation of nitrogen in the biosphere is not following this trend.

Conclusions

The technique of moss analysis is adequate for spatially valid biomonitoring of spatial and temporal trends of metals and nitrogen in terrestrial ecosystems. By this, it enables to prove the efficiency of environmental policies.

Recommendations and Perspectives

The accumulation of N in ecosystems is still a serious environmental problem. Related ecological impacts are the eutrophication of aquatic ecosystems like ground waters, lakes, rivers and oceans as well as the biocoenotic changes in terrestrial ecosystems. Thus, a statistically valid exposure analysis must encompass both, accumulation of metals and N bioaccumulation. Further, the bioaccumulation of persistent organic pollutants should be monitored. Finally, environmental biomonitoring should be conducted in much closer contact with human health aspects.     

Pre-dispersal seed predation: the role of fruit abortion and selective oviposition

Oviposition sites of phytophagous insects should correlate with plant traits that maximize survival of the progeny. Plants, on the other hand, should benefit from traits and developmental patterns that complicate oviposition decisions. In the antagonistic interaction between plant and pre-dispersal seed predator the time lag between egg laying and seed development may allow for abortion of fruits in plants, potentially reducing fitness loss through predation. We studied the perennial herb Lathvrus vernus and the beetle pre-dispersal seed predator Bruchus atomarius in Sweden to determine the fitness consequences of nonrandom fruit abortion in the plant and oviposition patterns of the beetle. The beetle had a sophisticated ability to locate fruits with high probability of retention, partly by fruit position and phenology but also by some additional unidentified cue. Mortality of eggs was density dependent, but still the egg-laying pattern was clumped. We found no defensive strategy in the plant; instead the predictable fruit abortion pattern was associated with decreased plant fitness. We discuss how interactions may pose simultaneous selection pressures on plant and insect traits and how life history traits and other selective forces may shape the adaptive outcome of the interaction in plant and insect, respectively.     

Antagonistic interactions between plant competition and insect herbivory

Interspecific competition between plants and herbivory by specialized insects can have synergistic effects on the growth and performance of the attacked host plant. We tested the hypothesis that competition between plants may also negatively affect the performance of herbivores as well as their top-down effect on the host plant. In such a case, the combined effects of competition and herbivory may be less than expected from a simple multiplicative response. In other words, competition and herbivory may interact antagonistically. In a greenhouse experiment, Poa annua was grown in the presence or absence of a competitor (either Plantago lanceolata or Trifolium repens), as well as with or without a Poa-specialist aphid herbivore. Both competition and herbivory negatively affected Poa growth. Competition also reduced aphid density on Poa. This effect could in part be explained by changes in the biomass and the nitrogen content of Poa shoots. In treatments with competitors, reduced aphid densities alleviated the negative effect of herbivory on above- and belowground Poa biomass. Hence, we were able to demonstrate an antagonistic interaction between plant-plant interspecific competition and herbivory. However, response indices suggested that antagonistic interactions between competition and herbivory were contingent on the identity of the competitor. We found the antagonistic effect only in treatments with T. repens as the competitor. We conclude that both competitor identity and the herbivore's ability to respond with changes in its density or activity to plant competition affect the magnitude and direction (synergistic vs. antagonistic) of the interaction between competition and herbivory on plant growth.