Although the proclamation of “water as an economic good” has been generally accepted among water resources managers, there are still some debates on the explanation of this topic. In this paper it is argued that different water forms or uses have different kinds of economic value. Even for the same form or use, water economic value can be transferred from one kind to another by interventions.<br/> If water is an economic good, water pricing should be recognized as one of the important incentive measures for water demand management. Although the increased block tariffs (IBTs) have become the tariff structure of choice in many developing countries, it still deserves more careful examination. The traditional IBT-con cannot achieve the initial objectives of IBTs for its incorrect designed structure.<br/> This paper is intent to critically examine the use of IBT-con and to strongly promote a new tariff structure, IRT-cap. The case study of Weinan City shows that IRT-cap is an effective tariff to achieve the objectives of equity, simplicity, transparency and implement as well. Also IRT-cap seems easier to achieve cost recovery than the traditional IBT-con taking the ability to pay of water consumers into account. Pilot projects are necessary to be formulated for verification of this new tariff.

The identification of unknown compounds is essential in a wide variety of research areas and especially so in environmental analysis. Combining liquid chromatography with tandem mass spectrometry today allows the identification of substances that were not amenable to classical techniques.Environmental toxicologists and chemists increasingly focus on chemicals that can potentially cause adverse effects in organisms and humans. Since effect concentrations are often very low, but also because the matrix can affect the sensitivity, selective enrichment has become a popular tool for sample clean-up and lowering the limit of detection. Advances in environmental analysis, including techniques based on molecular recognition for selective enrichment or effect-oriented research were presented in this session.

Adaptive radiations (ARs) frequently show remarkable repeatability where single lineages undergo multiple independent episodes of AR in distant places and long-separate time points. Genetic variation generated through hybridization between distantly related lineages can promote AR. This mechanism, however, requires rare coincidence in space and time between a hybridization event and opening of ecological opportunity, because hybridization generates large genetic variation only locally and it will persist only for a short period. Hence, hybridization seems unlikely to explain recurrent AR in the same lineage. Contrary to these expectations, our evolutionary computer simulations demonstrate that admixture variation can geographically spread and persist for long periods if the hybrid population becomes separated into isolated sub-lineages. Subsequent secondary hybridization of some of these can reestablish genetic polymorphisms from the ancestral hybridization in places far from the birthplace of the hybrid clade and long after the ancestral hybridization event. Consequently, simulations revealed conditions where exceptional genetic variation, once generated through a rare hybridization event, can facilitate multiple ARs exploiting ecological opportunities available at distant points in time and space.

Temporal genetic variation was studied within the cyclic parthenogenetic <i>Daphnia galeata-cucullata</i> species complex in Lake Tjeukemeer (The Netherlands). During three successive years, three allozyme loci were studied in order to compare the level of genetic variation in <i>D. galeata</i> (G), <i>D. cucullata</i> (C) and their interspecific hybrid (C × G). This data set was used to investigate: whether C × G hybrids are regularly produced by the parental species and to what extent backcrossing takes place in this species complex. G and C × G were the most abundant taxa, whereas C was only abundant in late summer and autumn. Genetic diversity was highest in C, lowest in G, and intermediate in C × G. <i>pgm</i> and <i>pgi</i> allele frequencies of C × G were not intermediate to those of the parental species but were more similar to G than to C. In addition, almost no significant deviations from Hardy-Weinberg were observed. An UPGMA analysis of Nei's genetic distances showed that C × G hybrids are more closely related to G (difference <0.04), than to C (difference 0.30). My data suggest, in accordance with other studies, that C × G hybrids are probably still formed by the parental species, though not necessarily every year. Furthermore, my data suggest that backcrossing occurred frequently, and led to introgression of C alleles into G.

The Activated Sludge Model No. 2d (ASM2d) presents a model for biological phosphorus removal with simultaneous nitrification-denitrification in activated sludge systems. ASM2d is based on ASM2 and is expanded to include the denitrifying activity of the phosphorus accumulating organisms (PAOs). This extension of ASM2 allows for improved modeling of the processes, especially with respect to the dynamics of nitrate and phosphate.

We studied population extinction of the locally abundant fen plant <I>Swertia perennis</I> in Switzerland and used up to 127-year old herbarium records to relocate 63 sites that had once hosted this species. We recorded current site characteristics and related them to the absence or abundance of populations. Fifty-four sites (86%) were still traditionally used (extensively mown or grazed). Fifteen populations (24%) had gone extinct. Extinction was more likely at lower altitude, in the peripheral distribution range of <I>S. perennis</I> (58% peripheral, 9% central populations extinct). on the smallest fens (75% extinct on fens < 400 m²) and on fens with intensified land use. However, even on traditionally managed wetlands 18.5% of the populations had gone extinct. Moreover, 40% of all remaining populations were smaller than 250 flowering plants. We conclude that both intensified agricultural practice and habitat fragmentation contributed to local extinction of <I>S. perennis</I>. Small populations, especially, may not be able to persist in the long term.

We assessed the effects of habitat fragmentation on the demography of the locally abundant, long-lived fen plant <I>Swertia perennis</I> L., by examining population structure, components of fitness and herbivory of 17 populations in Switzerland. We distinguished between large MAIN, small, barely isolated NEAR and small, geographically isolated DISTANT habitat islands. Large isolation distance of small sites significantly affected the transition from sub-adult to adult age states: the mean population density was reduced by 30%, the density of vegetative adults by 60% and the density of reproductive adults by 78% on DISTANT compared with NEAR islands. Seedling survivorship decreased significantly from MAIN to NEAR to DISTANT islands. Moreover, several vegetative components of fitness were significantly reduced on DISTANT islands, i.e. the length and number of leaves and the stern height. Finally, leaf herbivory was highest on small NEAR islands. Our results indicate that population viability of <I>S. perennis</I> is reduced on small, isolated fens, possibly because of arrested individual adult growth due to inbreeding. In contrast, environmental influences such as higher productivity through increased nutrient influx on small sites may be responsible for changed plant-herbivore interactions.

Animals have evolved a number of ways to protect themselves from the harmful effects of ultraviolet-B (UV-B) radiation, but little is known about the relative importance of different mechanisms protecting amphibian embryos from UV-B radiation. Using enzymatic removal of gelatinous coats (jelly envelope) surrounding the eggs of <I>Rana temporaria</I>, we tested the hypothesis that the jelly envelope acts as a sunscreen that protects embryos from harmful effects of UV-B radiation. We conducted two independent factorial laboratory experiments employing three different UV-B (no UV-B, normal, and enhanced) levels and jelly removal (control, modified, and completely removed) treatments. We found no UV-B X jelly removal treatment interactions in survival rates or in frequency of abnormal individuals, suggesting that jelly removal did not increase susceptibility of embryos to UV-B radiation. These results support the contention that the jelly envelope is not the most important means of protecting <i>R. temporaria</I> embryos from UV-B radiation. Other factors (e.g., melanin pigments, other sunscreen compounds, effective DNA-repair mechanisms) must be responsible for the high UV-B radiation tolerance of embryos.

Domestic water use is generally the most important component of urban water consumption. In this paper, the relatively new technique of artificial neural network (ANN) is proposed to model and forecast the water demand in urban areas. Results indicate that the WDF-ANN (water demand forecast using artificial neural network) model offers an effective way to formulate domestic water demand in Weinan City in China. The model evaluation shows that the correlation coefficients are more than 90% both for the training data and the testing data.

Effects of free-air carbon dioxide enrichment (FACE, 60 Pa pCO₂) on plant growth as compared with ambient pCO₂ (36 Pa) were studied in swards of <em>Lolium perenne</em> L. (perennial ryegrass) at two levels of N fertilization (14 and 56 g m⁻² a⁻¹) from 1993 to 2002. The objectives were to determine how plant growth responded to the availability of C and N in the long term and how the supply of N to the plant from the two sources of N in the soil, soil organic matter (SOM) and mineral fertilizer, varied over time. In three field experiments, ¹⁵N-labelled fertilizer was used to distinguish the sources of available N.<br/> In 1993, harvestable biomass under elevated pCO₂ was 7% higher than under ambient pCO₂. This relative pCO₂ response increased to 32% in 2002 at high N, but remained low at low N. Between 1993 and 2002, the proportions and amounts of N in harvestable biomass derived from SOM (excluding remobilized fertilizer) were, at high N, increasingly higher at elevated pCO₂ than at ambient pCO₂. Two factorial experiments confirmed that at high N, but not at low N, a higher proportion of N in harvestable biomass was derived from soil (including remobilized fertilizer) following 7 and 9 years of elevated pCO₂, when compared with ambient pCO₂.<br/> It is suggested that N availability in the soil initially limited the pCO₂ response of harvestable biomass. At high N, the limitation of plant growth decreased over time as a result of the stimulated mobilization of N from soil, especially from SOM. Consequently, harvestable biomass increasingly responded to elevated pCO₂. The underlying mechanisms which contributed to the increased mobilization of N from SOM under elevated pCO₂ are discussed. This study demonstrated that there are feedback mechanisms in the soil which are only revealed during long-term field experiments. Such investigations are thus, a prerequisite for understanding the responses of ecosystems to elevated pCO₂ and N supply.

Whether interspecific hybridization is important as a mechanism that generates biological diversity is a matter of controversy. Whereas some authors focus on the potential of hybridization as a source of genetic variation, functional novelty and new species, others argue against any important role, because reduced fitness would typically render hybrids an evolutionary dead end. By drawing on recent developments in the genetics and ecology of hybridization and on principles of ecological speciation theory, I develop a concept that reconciles these views and adds a new twist to this debate. Because hybridization is common when populations invade new environments and potentially elevates rates of response to selection, it predisposes colonizing populations to rapid adaptive diversification under disruptive or divergent selection. I discuss predictions and suggest tests of this hybrid swarm theory of adaptive radiation and review published molecular phylogenies of adaptive radiations in light of the theory.

The research on commons dilemmas is characterized by innumerable published findings, each standing relatively isolated from the other. To date there is little integration of the findings under a unified concept. The present contribution aims to integrate already existing findings in a general dynamic model of cooperative behavior in resource crises by means of computer simulation. The model postulates that people base their decisions regarding resource use on both ecological and social information. Whether or not ecological or social information will dominate, however depends on people's social values, attributions, and their perceptions of the state of the resource. The advantage of the simulation method used is that successful integration of the findings can be shown explicitly, as the simulation then replicates the experimental data. With the model presented here, it is also possible to let variables work together whose interaction has not yet been investigated in real experiments. For instance, the simulation model allows us to hypothesize that people, in dependence upon their resource uncertainty and in dependency upon their attributions, utilize a resource completely differently if the resource is in an optimal or sub-optimal condition.

The evaluation of toxicological effects at the cellular and molecular levels in organisms are often used to determine sites subjected to contamination problems that pose a threat to the long-term survival of organisms. However, the integration of multiple measurements on the health status of organisms into a model for site discrimination is challenging. This study compares two discrimination methods which are based on rule inference: rough sets (RS) analysis and classification trees (CT) with classical multivariate discriminant analysis (DA). Site classification was attempted with six biomarkers of effects: metallothionein levels, lipid peroxidation, DNA damage, levels of lipophosphoproteins (i.e., vitellins), phagocytosis activity and haemocyte cell viability on clam (<I>Mya arenaria</I>) populations from the Saguenay River fjord (Quebec, Canada). Rule based methods have the advantage of complete independence from data distribution constraints in contrast to the classification methods from multivariate analysis that are more commonly used in ecotoxicology. Results show that RS and CT gave better classifications than DA because they do not require strong distributional assumptions. Moreover, RS provided classification rules that could identify the most important biomarker(s) for site discrimination. RS and CT were shown to be simple and efficient methods for classifying multivariable ecotoxicological data. This methodology would be especially useful when freedom from distributional assumptions is required.

Among various groups of fishes, a shift in peak wavelength sensitivity has been correlated with changes in their photic environments. The genus <I>Sebastes</I> is a radiation of marine fish species that inhabit a wide range of depths from intertidal to over 600 m. We examined 32 species of <I>Sebastes</I> for evidence of adaptive amino acid substitution at the rhodopsin gene. Fourteen amino acid positions were variable among these species. Maximum likelihood analyses identify several of these to be targets of positive selection. None of these correspond to previously identified critical amino acid sites, yet they may in fact be functionally important. The occurrence of independent parallel changes at certain amino acid positions reinforces this idea. Reconstruction of habitat depths of ancestral nodes in the phylogeny suggests that shallow habitats have been colonized independently in different lineages. The evolution of rhodopsin appears to be associated with changes in depth, with accelerated evolution in lineages that have had large changes in depth.

Repression of competition (RC) within social groups has been suggested as a key mechanism driving the evolution of cooperation, because it aligns the individual’s proximate interest with the interest of the group. Despite its enormous potential for explaining cooperation across all levels of biological organization, ranging from fair meiosis, to policing in insect societies, to sanctions in mutualistic interactions between species, there has been no direct experimental test of whether RC favours the spread of cooperators in a well-mixed population with cheats. To address this, we carried out an experimental evolution study to test the effect of RC upon a cooperative trait – the production of iron-scavenging siderophore molecules – in the bacterium <I>Pseudomonas aeruginosa</I>. We found that cooperation was favoured when competition between siderophore producers and nonsiderophore-producing cheats was repressed, but not in a treatment where competition between the two strains was permitted. We further show that RC altered the cost of cooperation, but did not affect the relatedness among interacting individuals. This confirms that RC <I>per se</I>, as opposed to increased relatedness, has driven the observed increase in bacterial cooperation.

Ecotoxicological effect studies often expose test organisms under optimal environmental conditions. However, organisms in their natural settings rarely experience optimal conditions. On the contrary, during most of their lifetime they are forced to cope with sub-optimal conditions and occasionally with severe environmental stress. Interactions between the effects of a natural stressor and a toxicant can sometimes result in greater effects than expected from either of the stress types alone. The aim of the present review is to provide a synthesis of existing knowledge on the interactions between effects of "natural" and chemical (anthropogenic) stressors. More than 150 studies were evaluated covering stressors including heat, cold, desiccation, oxygen depletion, pathogens and immunomodulatory factors combined with a variety of environmental pollutants. This evaluation revealed that synergistic interactions between the effects of various natural stressors and toxicants are not uncommon phenomena. Thus, synergistic interactions were reported in more than 50% of the available studies on these interactions. Antagonistic interactions were also detected, but in fewer cases. Interestingly, about 70% of the tested chemicals were found to compromise the immune system of humans as judged from studies on human cell lines. The challenge for future studies will therefore be to include aspects of combined stressors in effect and risk assessment of chemicals in the environment.

The factors controlling rates of contaminant reduction by magnetite (Fe<SUB>3</SUB>O<SUB>4</SUB>) are poorly understood. Here, we measured the reduction rates of three ArNO<SUB>2</SUB> compounds by magnetite particles ranging from highly oxidized (<I>x</I> = Fe<SUP>2+</SUP>/Fe<SUP>3+</SUP> = 0.31) to fully stoichiometric (<I>x</I> = 0.50). Rates of ArNO<SUB>2</SUB> reduction became almost 5 orders of magnitude faster as the particle stoichiometry increased from <I>x</I> = 0.31 to 0.50. To evaluate what was controlling the rate of ArNO<SUB>2</SUB> reduction, we measured apparent <SUP>15</SUP>N kinetic isotope effects (<SUP>15</SUP>N-AKIE) values for nitrobenzene and magnetite open-circuit potentials (<I>E</I><SUB>OCP</SUB>). <SUP>15</SUP>N-AKIE values were greater than unity for all magnetite stoichiometries investigated, indicating that mass transfer processes are not controlling the rate of ArNO<SUB>2</SUB> reduction by magnetite. <I>E</I><SUB>OCP</SUB> measurements showed that the <I>E</I><SUB>OCP</SUB> for magnetite was linearly related to the stoichiometry, with more stoichiometric magnetite having a lower potential. Based on these results, we propose that conceptual models that incorporate both redox and Fe<SUP>2+</SUP> diffusion processes, rather than those that rely solely on diffusion of Fe<SUP>2+</SUP>, are more appropriate for understanding contaminant reduction by magnetite. Our work indicates that particle stoichiometry should be considered when evaluating rates of contaminant reduction by magnetite.

Life history variation and genotype composition were studied in two species of the <I>Daphnia longispina</I> group: the relatively large <I>D. galeata</I> (1.4 mm) and the smaller <I>D. cucullata</I> (0.9 mm). Several multi-locus genotypes of these species were compared with genotypes of their interspecific hybrid, <I>D. cucullata</I> × <I>D. galeata</I>. Both species and the hybrid co-occur in the shallow eutrophic Tjeukemeer. For two successive years, laboratory life table experiments were conducted at three temperatures (12.5°, 17.5°, and 22.5°C) and two food levels (carbon concentrations 0.62 and 1.64 mg/mL) to study the mechanisms that permit coexistence of taxa in this <I>Daphnia</I> hybrid species complex. Three-way analyses of variance showed significant main effects (e.g., temperature, food level, taxon) for most reproductive traits (e.g., number of newborns, age at first reproduction, number of juvenile instars, intrinsic rate of increase) among the <I>Daphnia</I> taxa. For size-related traits (e.g., size at maturity and offspring size) only one main effect, taxon, was found. Hybrids were intermediate to the parental species with respect to size and maturity, offspring size, and number of newborns. For developmental traits (number of juvenile instars and age at maturity) the hybrids tended to have the lowest values for all conditions. The intrinsic rate of increase (<I>r</I>) of the hybrid did not differ significantly from that of <I>D. galeata</I>, but was significantly higher than that of <I>D. cucullata</I>. We argue that essentially <I>r</I> will reach higher values for the hybrids than for <I>D. galeata</I>, because of the strong influence of size-selective fish predation. Our results are discussed in reference to different theories about the maintenance of hybrid species complexes in nature.

Cell walls of five Gram-positive bacterial strains, including four coryneforms and a <I>Bacillus brevis</I> strain were isolated and subsequently chemically analysed. The wall contribution to the total cell mass is calculated from a comparison of D-Lactate concentrations in hydrolysates of whole cells and isolated walls. D-Lactate concentrations are measured enzymatically after purification of the samples with active carbon. The optimum condition for the quantitative elimination of D-lactate from the peptidoglycan appears to be at 120°C and 4 M HCl. The wall fraction for the cells of the coryneform bacteria are in the range of 26-32% and is about 75% for the <I>B. brevis</I> cells.<br/> The peptidoglycan fraction in the walls of the coryneform bacteria was found to be rather high and constitutes about 23 to 31% of the cell wall dry weight. The protein content of the cell wall dry weight is somewhat lower and in the range of 7 to 14%. The peptidoglycan in the wall of the <I>B. brevis</I> strain forms a thin layer and contributes only about 5% to the cell wall dry weight. The high amount of proteins in the <I>B. brevis</I> cell wall (> 56%) can be attributed to a so called S(urface)layer.