Anthropogenic activities increase pesticide contamination and biological invasions in freshwater ecosystems. Understanding their combined effects on community structure and on ecosystem functioning presents challenges for an improved ecological risk assessment. This study focuses on an artificial stream mesocosms experiment testing for direct and indirect effects of insecticide (chlorantraniliprole - CAP) exposure on the structure of a benthic macroinvertebrate freshwater community and on ecosystem functioning (leaf decomposition, primary production). To understand how predator identity and resource quality alter the community responses to chemical stress, the mediating effects of an invasive predator species (crayfish Procambarus clarkii) and detritus quality (tested by using leaves of the invasive Eucalyptus globulus) on insecticide toxicity were also investigated. Low concentrations of CAP reduced the abundance of shredders and grazers, decreasing leaf decomposition and increasing primary production. Replacement of autochthonous predators and leaf litter by invasive species decreased macroinvertebrate survival, reduced leaf decomposition, and enhanced primary production. Structural equation modeling (SEM) highlighted that CAP toxicity to macroinvertebrates was mediated by the presence of crayfish or eucalypt leaf litter which are now common in many Mediterranean freshwaters. In summary, our results demonstrate that the presence of these two invasive species alters the effects of insecticide exposure on benthic freshwater communities. The approach used here also allowed for a mechanistic evaluation of indirect effects of these stressors and of their interaction on ecosystem functional endpoint, emphasizing the value of incorporating biotic stressors in ecotoxicological experiments.
- MeSH
- Ecosystem * MeSH
- Insecticides * MeSH
- Plant Leaves MeSH
- Rivers MeSH
- Fresh Water MeSH
- Introduced Species MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
BACKGROUND: Alternative organism designs (i.e. the existence of distinct combinations of traits leading to the same function or performance) are a widespread phenomenon in nature and are considered an important mechanism driving the evolution and maintenance of species trait diversity. However, alternative designs are rarely considered when investigating assembly rules and species effects on ecosystem functioning, assuming that single trait trade-offs linearly affect species fitness and niche differentiation. SCOPE: Here, we first review the concept of alternative designs, and the empirical evidence in plants indicating the importance of the complex effects of multiple traits on fitness. We then discuss how the potential decoupling of single traits from performance and function of species can compromise our ability to detect the mechanisms responsible for species coexistence and the effects of species on ecosystems. Placing traits in the continuum of organism integration level (i.e. traits hierarchically structured ranging from organ-level traits to whole-organism traits) can help in choosing traits more directly related to performance and function. CONCLUSIONS: We conclude that alternative designs have important implications for the resulting trait patterning expected from different assembly processes. For instance, when only single trade-offs are considered, environmental filtering is expected to result in decreased functional diversity. Alternatively, it may result in increased functional diversity as an outcome of alternative strategies providing different solutions to local conditions and thus supporting coexistence. Additionally, alternative designs can result in higher stability of ecosystem functioning as species filtering due to environmental changes would not result in directional changes in (effect) trait values. Assessing the combined effects of multiple plant traits and their implications for plant functioning and functions will improve our mechanistic inferences about the functional significance of community trait patterning.
Under global change, how biological diversity and ecosystem services are maintained in time is a fundamental question. Ecologists have long argued about multiple mechanisms by which local biodiversity might control the temporal stability of ecosystem properties. Accumulating theories and empirical evidence suggest that, together with different population and community parameters, these mechanisms largely operate through differences in functional traits among organisms. We review potential trait-stability mechanisms together with underlying tests and associated metrics. We identify various trait-based components, each accounting for different stability mechanisms, that contribute to buffering, or propagating, the effect of environmental fluctuations on ecosystem functioning. This comprehensive picture, obtained by combining different puzzle pieces of trait-stability effects, will guide future empirical and modeling investigations.
- MeSH
- Biodiversity * MeSH
- Ecosystem * MeSH
- Phenotype MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Review MeSH
Biodiversity-ecosystem functioning experiments (BEF) typically manipulate sown species richness and composition of experimental communities to study ecosystem functioning as a response to changes in diversity. If sown species richness is taken as a measure of diversity and aboveground biomass production as a measure of community functioning, then this relationship is usually found to be positive. The sown species richness can be considered the equivalent of a local species pool in natural communities. However, in addition to species richness, realized diversity is also an important community diversity component. Realized diversity is affected by environmental filtering and biotic interactions operating within a community. As both sown species richness and the realized diversity in BEF studies (as well as local species pool vs observed realized richness in natural communities) can differ markedly, so can their effects on the community functioning. We tested this assumption using two data sets: data from a short-term pot experiment and data from the long-term Jena biodiversity plot experiment. We considered three possible predictors of community functioning (aboveground biomass production): sown species richness, realized diversity (defined as inverse of Simpson dominance index), and survivor species richness. Sown species richness affected biomass production positively in all cases. Realized diversity as well as survivor species richness had positive effects on biomass in approximately half of cases. When realized diversity or survivor species richness was tested together with sown species richness, their partial effects were none or negative. Our results suggest that we can expect positive diversity-productivity relationship when the local species pool size is the decisive factor determining realized observed diversity; in other cases, the shape of the diversity-functioning relationship may be quite opposite.
- MeSH
- Biodiversity * MeSH
- Biomass MeSH
- Ecosystem * MeSH
- Population Dynamics MeSH
- Plants * MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
In the last decades, the use of organic ultraviolet-filters (UV-filters) has increased worldwide, and these compounds are now considered emerging contaminants of many freshwater ecosystems. The present study aimed to assess the effects of 3-(4-methylbenzylidene) camphor (4-MBC) on a freshwater invertebrate community and on associated ecological functions. For that, artificial streams were used, and a natural invertebrate benthic community was exposed to sediments contaminated with two concentrations of 4-MBC. Effects were evaluated regarding macroinvertebrate abundance and community structure, as well as leaf decomposition and primary production. Results showed that the macroinvertebrate community parameters and leaf decomposition rates were not affected by 4-MBC exposure. On the other hand, primary production was strongly reduced. This study highlights the importance of higher tier ecotoxicity experiments for the assessment of the effects of low concentrations of organic UV-filters on freshwater invertebrate community structure and ecosystem functioning.
- MeSH
- Invertebrates drug effects physiology MeSH
- Water Pollutants, Chemical toxicity MeSH
- Ecosystem MeSH
- Camphor analogs & derivatives toxicity MeSH
- Rivers * MeSH
- Fresh Water chemistry MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
Biodiversity is known to increase ecosystem functioning. However, species vary in their contributions to ecosystem processes. Here, we investigated seven ecosystem functions based on the consumption of different resources in tropical ant communities. We analysed how different species influence site-level resource consumption, and determined how each species influenced performance and stability of these functions. Based on simulated extinctions, we identified 'key species' with significant functional contributions. We then investigated which traits, such as biomass, abundance, and specialisation, characterized them, and compared trait distributions across four sites to analyse differences in functional redundancy. Only few species significantly influenced ecosystem functions. Common generalist species tended to be the most important drivers of many ecosystem functions, though several specialist species also proved to be important in this study. Moreover, species-specific ecological impacts varied across sites. In addition, we found that functional redundancy varied across sites, and was highest in sites where the most common species did not simultaneously have the greatest functional impacts. Furthermore, redundancy was enhanced in sites where species were less specialised and had more even incidence distributions. Our study demonstrates that the ecological importance of a species depends on its functional traits, but also on the community context. It cannot be assessed without investigating its species-specific performance across multiple functions. Hence, to assess functional redundancy in a habitat and the potential for compensation of species loss, researchers need to study species-specific traits that concern functional performance as well as population dynamics and tolerance to environmental conditions.
- MeSH
- Biodiversity * MeSH
- Biomass MeSH
- Species Specificity MeSH
- Ecology MeSH
- Ecosystem * MeSH
- Ants * MeSH
- Population Dynamics MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
Previously published multidisciplinary studies in the Miramichi and Bouctouche rivers (New Brunswick, Canada) noted significant changes in fish health parameters, including elevated tissue levels of organic contaminants and a wide range of physiological disturbances, in mummichog Fundulus heteroclitus (L.) from a site on the Miramichi River that received bleached kraft pulpmill and municipal effluent. The present study reports differences in the abundance of individual parasite species, as well as parasite infracommunity and component community composition, in mummichog from both rivers. These differences were evaluated in relation to host (size, condition, immune function, tissue organochlorine contaminant levels) and environmental (faecal coliform counts, salinity, temperature) data derived from the previously published studies. Overall, 18 parasite species were identified, the most common of which were Ascocotyle sp. larv., Ornithodiplostomum sp. larv., Posthodiplostomum sp. larv., and Proteocephalus filicollis (Rudolphi, 1802). There were broad differences in parasite community structure and composition between rivers and within rivers, the most prominent pattern being a pronounced difference between sites in the upper and lower estuary of each river that was likely driven by salinity. Mean infracommunity richness was also positively related to faecal coliforms (considered here as a surrogate measure of eutrophication via municipal sewage), and both were highest at the most polluted site. We noted no other significant relationships. Thus our data suggest that the parasite communities in these two estuaries were primarily structured by large upstream/downstream ecological gradients in salinity, and secondarily by eutrophication due to pollution by municipal and industrial effluents. Overall, our results highlight the value of coordinated multidisciplinary studies for understanding the factors that shape parasite abundance and community structure.
- MeSH
- Demography MeSH
- Ecosystem MeSH
- Fundulidae MeSH
- Human Activities MeSH
- Fish Diseases epidemiology parasitology MeSH
- Parasitic Diseases, Animal epidemiology parasitology MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Geographicals
- New Brunswick MeSH
Artificial water bodies like ditches, fish ponds, weirs, reservoirs, fish ladders, and irrigation channels are usually constructed and managed to optimize their intended purposes. However, human-made aquatic systems also have unintended consequences on ecosystem services and biogeochemical cycles. Knowledge about their functioning and possible additional ecosystem services is poor, especially compared to natural ecosystems. A GIS analysis indicates that currently only ~ 10% of European surface waters are covered by the European Water Framework directive, and that a considerable fraction of the excluded systems are likely human-made aquatic systems. There is a clear mismatch between the high possible significance of human-made water bodies and their low representation in scientific research and policy. We propose a research agenda to build an inventory of human-made aquatic ecosystems, support and advance research to further our understanding of the role of these systems in local and global biogeochemical cycles as well as to identify other benefits for society. We stress the need for studies that aim to optimize management of human-made aquatic systems considering all their functions and to support programs designed to overcome barriers of the adoption of optimized management strategies.
Apex predators play a key role in ecosystem stability across environments but their numbers in general are decreasing. By contrast, European catfish (Silurus glanis), the European freshwater apex predator, is on the increase. However, studies concerning apex predators in freshwaters are scarce in comparison to those in terrestrial and marine ecosystems. The present study combines stomach content and stable isotope analyses with diet preferences of catfish to reveal its impact on the ecosystem since stocking. Catfish niche width is extremely wide in comparison to the typical model predator, Northern pike (Esox lucius). Catfish and pike have different individual dietary specialization that results in different functional roles in coupling or compartmentalizing distinct food webs. The role of both species in the ecosystem is irreplaceable due to multiple predator effects. The impact of catfish is apparent across the entire aquatic ecosystem, but herbivores are the most affected ecological group. The key feature of catfish, and probably a common feature of apex predators in general, is utilization of several dietary strategies by individuals within a population: long-term generalism or specialization and also short-term specialization. Catfish, similar to other large-bodied apex predators, have two typical features: enormous generalism and adaptability to new prey sources.
- MeSH
- Biomass MeSH
- Diet * MeSH
- Ecosystem * MeSH
- Esocidae physiology MeSH
- Adaptation, Physiological * MeSH
- Nitrogen Isotopes MeSH
- Carbon Isotopes MeSH
- Lakes MeSH
- Food Chain MeSH
- Predatory Behavior physiology MeSH
- Food Preferences MeSH
- Seasons MeSH
- Fresh Water * MeSH
- Catfishes physiology MeSH
- Stomach physiology MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Parameters characterizing the structure of the decomposer food web, biomass of the soil microflora (bacteria and fungi) and soil micro-, meso- and macrofauna were studied at 14 non-reclaimed 1- 41-year-old post-mining sites near the town of Sokolov (Czech Republic). These observations on the decomposer food webs were compared with knowledge of vegetation and soil microstructure development from previous studies. The amount of carbon entering the food web increased with succession age in a similar way as the total amount of C in food web biomass and the number of functional groups in the food web. Connectance did not show any significant changes with succession age, however. In early stages of the succession, the bacterial channel dominated the food web. Later on, in shrub-dominated stands, the fungal channel took over. Even later, in the forest stage, the bacterial channel prevailed again. The best predictor of fungal bacterial ratio is thickness of fermentation layer. We argue that these changes correspond with changes in topsoil microstructure driven by a combination of plant organic matter input and engineering effects of earthworms. In early stages, soil is alkaline, and a discontinuous litter layer on the soil surface promotes bacterial biomass growth, so the bacterial food web channel can dominate. Litter accumulation on the soil surface supports the development of the fungal channel. In older stages, earthworms arrive, mix litter into the mineral soil and form an organo-mineral topsoil, which is beneficial for bacteria and enhances the bacterial food web channel.
- MeSH
- Ecosystem MeSH
- Mining * MeSH
- Food Chain * MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Geographicals
- Czech Republic MeSH
