Indicators to support healthy urban gardening in urban management.

Urban gardening is part of a trend towards more parks and green areas in cities, consumption of organic, locally grown products, and a closer relationship with one's own living environment. Our literature review shows that urban gardens provide opportunities for physical activity and allow people to consume homegrown fruit and vegetables. Urban gardens may also reduce stress levels of gardeners and improve social cohesion. In this way, they can help to prevent health problems. Good quality of urban soil and the functioning of soil ecosystems are indispensable prerequisites for these. We developed a framework that shows how ecosystem health and human health are interconnected in urban gardening, by placing it in the context of urban green space management and valuation. This study yields a set of indicators, which can be used to assess soil ecosystem services and health impacts. They may provide a basis for the evolving dialogue in decision-making processes and partnership activities in urban management. Recognizing the potential effects and discussing what is important to whom, might be enough to find synergies. Importantly, the initiators of urban gardens are often citizens, who seek support from other stakeholders. The social network established by gardens may contribute to health-enabling, cohesive communities involved with their living environment. To maximize health benefits, it is useful to make the urban gardens accessible to many people. This study suggests that urban gardens deserve a position in urban green space management as they may help to address societal challenges like urbanization, health and well-being in aging populations and climate adaptation.

Resource niche overlap promotes stability of bacterial community metabolism in experimental microcosms.

Decomposition of organic matter is an important ecosystem process governed in part by bacteria. The process of decomposition is expected to benefit from interspecific bacterial interactions such as resource partitioning and facilitation. However, the relative importance of resource niche breadth (metabolic diversity) and resource niche overlap (functional redundancy) on decomposition and the temporal stability of ecosystem processes received little scientific attention. Therefore, this study aims to evaluate the effect of an increase in bacterial community resemblance on both decomposition and the stability of bacterial metabolism in aquatic sediments. To this end, we performed laboratory microcosm experiments in which we examined the influence of bacterial consortia differing in number and composition of species on bacterial activity (Electron Transport System Activity, ETSA), dissolved organic carbon production and wavelet transformed measurements of redox potential (Eh). Single substrate affinities of the individual bacterial species were determined in order to calculate the metabolic diversity of the microbial community. Results presented here indicate that bacterial activity and organic matter decomposition increase with widening of the resource niche breadth, and that metabolic stability increases with increasing overlap in bacterial resource niches, hinting that resource niche overlap can promote the stability of bacterial community metabolism.

Ranking ecological risks of multiple chemical stressors on amphibians.

Populations of amphibians have been declining worldwide since the late 1960s. Despite global concern, no studies have quantitatively assessed the major causes of this decline. In the present study, species sensitivity distributions (SSDs) were developed to analyze the sensitivity of anurans for ammonium, nitrate, heavy metals (cadmium, copper), pesticides (18 compounds), and acidification (pH) based on laboratory toxicity data. Ecological risk (ER) was calculated as the probability that a measured environmental concentration of a particular stressor in habitats where anurans were observed would exceed the toxic effect concentrations derived from the species sensitivity distributions. The assessment of ER was used to rank the stressors according to their potential risk to anurans based on a case study of Dutch freshwater bodies. The derived ERs revealed that threats to populations of anurans decreased in the sequence of pH, copper, diazinon, ammonium, and endosulfan. Other stressors studied were of minor importance. The method of deriving ER by combining field observation data and laboratory data provides insight into potential threats to species in their habitats and can be used to prioritize stressors, which is necessary to achieve effective management in amphibian conservation.

Ecotoxicogenomics: bridging the gap between genes and populations.

Ecotoxicogenomics might help solving open questions that cannot be answered by standard ecotoxicity tests currently used in environmental risk assessment. Changes in gene expression are claimed to serve potentially as early warning indicators for environmental effects and as sensitive and specific ecotoxicological end points. Ecotoxicogenomics focus on the lowest rather than the highest levels of biological organization. Our aim was to explore the links between gene expression responses and population level responses, both mechanistically (conceptual framework) and correlatively (Species Sensitivity Distribution). The effects of cadmium on aquatic species were compared for gene level responses (Lowest Observed Effect Concentrations) and individual level responses (median Lethal Concentrations, LC(50), and No Observed Effect Concentrations, NOEC). Responses in gene expression were on average four times above the NOEC and eleven times below the LC(50) values. Currently, use of gene expression changes as early warning indicators of environmental effects is not underpinned due to a lack of data. To confirm the sensitivity claimed by ecotoxicogenomics more testing at low concentrations is needed. From the conceptual framework, we conclude that for a mechanistic gene population link in risk management, research is required that includes at least one meaningful end point at each level of organization.

System-oriented ecotoxicological research: which way to go?

This paper presents an overview of the possibilities for further development of tools and. approaches for the ecological assessment and management of diffusively contaminated ecosystems. It is based on the results of the "Netherlands Stimulation Programme on Ecosystem-oriented Ecotoxicological Research", the SSEO programme, which ran from 1998 to 2006, and on opinions of international experts on ecological and ecotoxicological risk-assessment methods and their legal applications. The paper also discusses the pros and cons of the set-up of the SSEO programme. Proper management of diffusively polluted areas has to be based on an integral risk-based and system approach. The approach has to be founded on the relationships between pollution, natural stresses, management measures and the presence and activities of specific species. Furthermore, the relationships between biodiversity in ecosystems and its stability and functioning have to be known. The assessment of aquatic ecosystem quality is now based on the comparisons of the composition of actual species with that of reference species. This type of system does not yet exist for the assessment of soil quality, but it is being developed. It is shown that ecological quality criteria based on a Species Sensitivity Distributions approach are sufficiently conservative to avoid or prevent major ecological impacts of diffuse pollution at concentrations below legal standards. However, a proper quality relationship of biodiversity and ecosystem functioning is lacking in the ecological assessment methods. Future research should focus on the relationship of ecosystem structure (species composition) and ecosystem functioning and on the impact of disturbing the environment and appropriate management measures.

Upgrading system-oriented ecotoxicological research.

In the 1990s the Dutch government expressed the need to investigate the impacts of diffuse pollution at (sub)-ecosystem levels. The resulting Netherlands Stimulation Programme on System-oriented Ecotoxicological Research (SSEO programme) ran from 1998 to 2006. Its primary objective was to assess the impacts of low- to medium-level, diffuse, multiple contaminations on ecosystems. The research results were intended as underpinning for policies on environmental, conservation and nature issues. Research was carried out at three sites that were selected because of their importance for nature management and the presence of diffuse contamination. These sites were: a river meadow/floodplain area (Afferdensche en Deestsche Waarden), an estuarine reed-land area (Biesbosch) and an area of lowland peat soils that had been contaminated with urban waste in past centuries (De Ronde Venen). This introductory paper describes the set-up of the programme, the types of diffuse contamination, the interactions between pollutants and other stress factors, the various methodologies used to integrate the effects on (sub)ecosystem level, and the consequences for formulating policies for and the management of these types of locations. The results of the programme are diverse and complicated and show how difficult it is to draw firm, unambiguous, generic conclusions about the effects at the 'total' ecosystem level. It is however, possible to draw conclusions about effects on major components of ecosystems: 1) The distribution of contaminants, both from a spatial, chemical and ecotoxicological point of view, plays a decisive role in actual effect levels. Even when total contaminant loads are high, such as in estuarine and floodplain areas, bioavailability may be so low that the actual effects are limited. The irregular, heterogeneous, spatial distribution of contaminants in the soil further complicates effect studies, impact assessments and monitoring. 2) Various stress factors, other than contaminants, both natural and anthropogenic, also play a role. The negative effect of the repeated inundation of floodplain areas, for instance, greatly interferes with the impact of contaminants in the lower soil layers. 3) A major problem is to find a method to extrapolate the observations from individual and population levels to the ecosystem level. In addition to traditional food-chain models and similar approaches, the potential of other, not yet extensively explored, ecosystem interaction mechanisms is discussed. 4) Finally, the results have to be interpreted from a policy point of view, both for national soil policies and for implementing the EU Soil Strategy regulations.

Functional recovery of biofilm bacterial communities after copper exposure.

Potential of bacterial communities in biofilms to recover after copper exposure was investigated. Biofilms grown outdoor in shallow water on glass dishes were exposed in the laboratory to 0.6, 2.1, 6.8 micromol/l copper amended surface water and a reference and subsequently to un-amended surface water. Transitions of bacterial communities were characterised with denaturing gradient gel electrophoresis (DGGE) and community-level physiological profiles (CLPP). Exposure to 6.8 micromol/l copper provoked distinct changes in DGGE profiles of bacterial consortia, which did not reverse upon copper depuration. Exposure to 2.1 and 6.8 micromol/l copper was found to induce marked changes in CLPP of bacterial communities that proved to be reversible during copper depuration. Furthermore, copper exposure induced the development of copper-tolerance, which was partially lost during depuration. It is concluded that bacterial communities exposed to copper contaminated water for a period of 26 days are capable to restore their metabolic attributes after introduction of unpolluted water in aquaria for 28 days.

Legislation and ecological quality assessment of soil: implementation of ecological indication systems in Europe.

Nationally and internationally there are an increasing number of legal initiatives to protect the ecological processes in soil. This article describes the legal situation concerning the protection of natural functions of soil in Europe (mainly The Netherlands (since 1987) and Germany (since 1998)). Examples of processes to be protected comprise the element cycles, the degradation of pollutants, and the conversion of organic matter. These processes are performed by organisms, and therefore, there is a growing consensus that protection of soil biodiversity is necessary for the survival of humans and the above-ground ecosystems. It is discussed that protection of soil ecosystems needs requires definitions and aims for the ecological quality of soil (as already provided for aquatic ecosystems). Taking into account that most soils are privately owned, legal initiatives are necessary to clarify responsibilities and to direct research toward the implementation of reproducible and standardized methods to determine the ecological quality of soil.

Ecological classification and assessment concepts in soil protection.

Evaluation of ecological soil quality requires the integration of physical, chemical, and biological variables. From a biological point of view, the maintenance of biodiversity and the assurance of life support functions are the main goals of protection to secure sustainable land use. To reach these goals, biological concepts for the classification and assessment of soils were developed in various countries, most of them based on similar concepts in limnology and aquatic ecotoxicology, which are already routinely applied. In this article, an overview of existing concepts, as well as a detailed description of the two most promising ones (BISQ from The Netherlands and BBSK from Germany), is given, followed by a discussion of the properties essential to an ideal biological concept for soil protection. Finally, recommendations for further research and a basic outline of a monitoring program ready for immediate use are provided.

Status and outlook of ecological soil classification and assessment concepts.

This article provides an outlook for the further development of ecological soil classification and assessment systems, based on the insights of an international group of authors working on the development of such systems for their respective governments. It is shown that a lot may be learned from the assessment of the quality of aquatic ecosystems. Parallel to the approach applied there, an approach based on extensive monitoring and ecological insights is proposed for soils. The article also contains recommendations for research to be done to derive optimal terrestrial monitoring networks, derivation of descriptions of reference locations, derivation of ecological quality criteria, the development of indicators, and an optimal exchange of data.

The use of nematodes in ecological soil classification and assessment concepts.

Although there has been extensive applied agricultural research (research on plant-parasitic species has a long tradition), insufficient taxonomical knowledge, especially of free-living nematodes, is a serious problem concerning the use of nematodes in soil classification and assessment. However, due to their essential and various roles in ecosystem functioning and their high diversity and abundance, interest in using these organisms for the assessment of soil quality is increasing. In particular in The Netherlands, but also in other countries (e.g., Germany, United Kingdom), progress in taxonomy is being achieved and evaluation strategies are being elaborated. While examples exist for the successful use of nematodes as part of a community approach comprising several organism groups, much work concerning the establishment of an adequate reference database remains to be done. This article is a general overview of the suitability and application of soil nematodes in soil assessments.

Considerations for the use of soil ecological classification and assessment concepts in soil protection.

In comparison with other environmental compartments, the protection of soil was identified relatively late as an important issue. Even later, policy makers and the general public considered the ecological functions of the soil. However, recently, the central role of these functions, as well as the importance of the soil organism community, has become obvious in several countries in Europe and in the European Union itself. In this contribution, basic considerations referring to use of ecological endpoints for the classification and assessment of soils are discussed. The article begins with two goals of protection: to protect soil so that it can function and to protect soil as a habitat for organisms necessary for these functions. Afterward, the quality of soil from is discussed from a biological point of view. Finally, on the basis of experience from limnology and botany, recommendations are made for monitoring programs. In other articles of this series, details of the entire approach to ecological classification and assessment are outlined.

Effects of copper and temperature on aquatic bacterial communities.

The present study aimed to characterise effects of copper and temperature on bacterial communities in photosynthetic biofilms using a suit of supplementary methods: pollution-induced community tolerance (PICT), DNA profiles with denaturing gradient gel electrophoresis (DGGE) and physiological profiles with community-level physiological profiling (CLPP). Biofilms of algae and bacteria were grown in a ditch of a Dutch polder and exposed in the laboratory to copper (3 microM and a reference) at three different temperatures (10, 14 and 20 degrees C). Bacterial communities sampled from the field showed heterogeneity in their physiological profiles, however the heterogeneity decreased during laboratory incubation. After 3 days laboratory incubation, the copper treated biofilms were different from the reference biofilms, as revealed by DGGE and CLPP analyses. Effects of temperature were not observed in the CLPPs, or in the DGGE profiles. PICT was observed for the bacterial communities at all temperatures. The copper-tolerance at 10 and 14 degrees C increased about 3 times, whereas copper-tolerance at 20 degrees C increased about 6 times. Temperature had an effect on the community tolerance, but not on the structure or on the physiological profile, suggesting that temperature was not a major factor causing successional changes under these laboratory conditions. In contrast, temperature had an effect on tolerance development indicating that the exposure to copper was enhanced at higher temperature.

Copper-induced modifications of the trophic relations in riverine algal-bacterial biofilms.

The effects of copper (Cu) on photosynthetic riverine biofilms were studied in artificial stream channels. Direct effects on the composition and functioning of the biofilms were investigated using plant pigments, community-level physiological profiles (CLPP), and pulse-amplitude-modulated (PAM) fluorescence. Copper caused a significant reduction of microalgal biomass and induced a shift in the population from diatoms to cyanobacteria. However, a decrease in biomass indicated that the replacement of species was not totally effective to counteract the toxic effects of Cu. A direct effect of Cu could also be shown in the bacterial community, and, furthermore, changes in the CLPP could be related to the Cu treatment. Copper-exposed biofilms lost the capacity to use between 11 and 15% of the substrates, but many of the remaining capacities became more robust, indicating an increased Cu tolerance due to the exposure. The change in the biofilm microbial composition points to the indirect effects of Cu on biofilms due to the close interdependence between biofilm autotrophic and heterotrophic compartments. Grazing by snails, which appeared to be an important factor structuring biofilms without any Cu addition, had a very minor effect on Cu-exposed biofilms. Although grazing changed the bacterial composition, its effects were not detected either on the algal community or on the biofilm community tolerance to Cu.