The structure of Ciliated Protozoa communities in biological sewage-treatment plants

Samples of mixed-liquor from 39 activated-sludge plants and of biological film from 49 rotating discs were examined microscopically for the presence of Ciliated Protozoa. 45 and 47 species of Ciliates were identified in activated-sludge plants and rotating discs, respectively.Most of the ciliate species, which are frequent inhabitants of activated-sludge, were found also in rotating discs. Statistical analysis based on affinity index and on recurrent groups, made it possible to reconstruct the structure in species of ciliate communities both in activated-sludge plants and in rotating discs.     

Non-native ecosystem engineer alters estuarine communities

Many ecosystems are created by the presence of ecosystem engineers that play an important role in determining species' abundance and species composition. Additionally, a mosaic environment of engineered and non-engineered habitats has been shown to increase biodiversity. Non-native ecosystem engineers can be introduced into environments that do not contain or have lost species that form biogenic habitat, resulting in dramatic impacts upon native communities. Yet, little is known about how non-native ecosystem engineers interact with natives and other non-natives already present in the environment, specifically whether non-native ecosystem engineers facilitate other non-natives, and whether they increase habitat heterogeneity and alter the diversity, abundance, and distribution of benthic species. Through sampling and experimental removal of reefs, we examine the effects of a non-native reef-building tubeworm, Ficopomatus enigmaticus, on community composition in the central Californian estuary, Elkhorn Slough. Tubeworm reefs host significantly greater abundances of many non-native polychaetes and amphipods, particularly the amphipods Monocorophium insidiosum and Melita nitida, compared to nearby mudflats. Infaunal assemblages under F. enigmaticus reefs and around reef's edges show very low abundance and taxonomic diversity. Once reefs are removed, the newly exposed mudflat is colonized by opportunistic non-native species, such as M. insidiosum and the polychaete Streblospio benedicti, making removal of reefs a questionable strategy for control. These results show that provision of habitat by a non-native ecosystem engineer may be a mechanism for invasional meltdown in Elkhorn Slough, and that reefs increase spatial heterogeneity in the abundance and composition of benthic communities.     

Nitrogen-fixing communities in an intertidal ecosystem.

Nitrogen gixation (acetylene reduction) associated with various communities in the intertidal sand and mud flat was measured in situ. Areas which were colonized by algae, plants, and animals generally had significantly higher activities than areas which were visibly uncolonized. The highest activities were measured at sites colonized by a mixed bloom of Oscillatoria-Euglena-photosynthetic bacteria. These areas occupied only about 1% of the surface of the sediments, yet contributed nearly 50% of the biologically fixed nitrogen. Enteromorpha communities also exhibited relatively high activities. Sites were grouped according to the statistical significance of the mean of their activities: group I: uncolonized sand, mud and gravel flats, Eelgrass (Zostera) communities, and snail (amphibola) beds, with an estimated contribution of 1 g N ha-1 day-1; group II: Cockel (Chione) beds, 3 g N ha-1 day-1; group III: Salicornia, Ulva, Juncus, and Enteromorpha, 10 g N ha-1 day-1; and group IV: Oscillatoria-Euglena-photosynthetic bacteria association, 200 g N ha-1 day-1. Enteromorpha and Oscillatoria-Euglena-photosynthetic bacteria communities showed significantly lower rates of nitrogen fixation in the dark than in the light.     

Salinity as a determinant of the structure of biological communities in salt lakes

The paper considers the extent to which salinity determines the structure of biological communities (composition and species richness and diversity) in saline lakes, i.e. inland bodies of water with salinities in excess of 3 g l-1. It also considers the extent to which oxygen, ionic composition, pH, hydrological patterns (degree of permanence and impermanence of water), geographical position, palaeoclimatic events, chance, human intervention, and biological interactions especially predation determine biological communities in salt lakes. It suggests that salinity is less significant as a determinant of community structure in salt lakes than has been assumed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ciliated Protozoan communities in a fluvial ecosystem

The ciliated protozoan communities in the Llobregat River (Barcelona, Spain) were studied for one year. Samples were taken from 11 different stations. The physical-chemical factors of the water as well as the qualitative and quantitative nature of the ciliate populations were considered. 105 species of ciliates, grouped in 13 orders, were found.The species which constantly appeared at all 11 stations (although not every month) were Litonotus fasciola, Trithigmostoma cucullulus, Cyclidium glaucoma, Glaucoma scintillans, Vorticella microstoma, Oxytricha sp., Stylonychia mytilus, Aspidisca costata and Aspidisca lynceus. The index of diversity at the different stations, and the affinity between the most abundant species, were also determined.     

Biodiversity and ecosystem functioning in naturally assembled communities

Approximately 25 years ago, ecologists became increasingly interested in the question of whether ongoing biodiversity loss matters for the functioning of ecosystems. As such, a new ecological subfield on Biodiversity and Ecosystem Functioning (BEF) was born. This subfield was initially dominated by theoretical studies and by experiments in which biodiversity was manipulated, and responses of ecosystem functions such as biomass production, decomposition rates, carbon sequestration, trophic interactions and pollination were assessed. More recently, an increasing number of studies have investigated BEF relationships in non‐manipulated ecosystems, but reviews synthesizing our knowledge on the importance of real‐world biodiversity are still largely missing. I performed a systematic review in order to assess how biodiversity drives ecosystem functioning in both terrestrial and aquatic, naturally assembled communities, and on how important biodiversity is compared to other factors, including other aspects of community composition and abiotic conditions. The outcomes of 258 published studies, which reported 726 BEF relationships, revealed that in many cases, biodiversity promotes average biomass production and its temporal stability, and pollination success. For decomposition rates and ecosystem multifunctionality, positive effects of biodiversity outnumbered negative effects, but neutral relationships were even more common. Similarly, negative effects of prey biodiversity on pathogen and herbivore damage outnumbered positive effects, but were less common than neutral relationships. Finally, there was no evidence that biodiversity is related to soil carbon storage. Most BEF studies focused on the effects of taxonomic diversity, however, metrics of functional diversity were generally stronger predictors of ecosystem functioning. Furthermore, in most studies, abiotic factors and functional composition (e.g. the presence of a certain functional group) were stronger drivers of ecosystem functioning than biodiversity per se. While experiments suggest that positive biodiversity effects become stronger at larger spatial scales, in naturally assembled communities this idea is too poorly studied to draw general conclusions. In summary, a high biodiversity in naturally assembled communities positively drives various ecosystem functions. At the same time, the strength and direction of these effects vary highly among studies, and factors other than biodiversity can be even more important in driving ecosystem functioning. Thus, to promote those ecosystem functions that underpin human well‐being, conservation should not only promote biodiversity per se, but also the abiotic conditions favouring species with suitable trait combinations.     

Biodiversity influences ecosystem functioning in aquatic angiosperm communities

Knowledge of the connection between aquatic plant diversity and ecosystem processes is still limited. To examine how plant species diversity affects primary productivity, plant nutrient use, functional diversity of secondary producers and population/community stability, we manipulated submerged angiosperm species diversity in a field experiment lasting 15 weeks. Plant richness increased the shoot density for three of four species. Polyculture biomass production was enhanced by increasing richness, with positive complementarity and selection effects causing positive biodiversity effects. Species richness enhanced the community stability for biomass production and shoot density. Sediment ammonium availability decreased with plant diversity, suggesting improved nutrient usage with increasing plant richness. Interestingly, positive multitrophic effects of plant species richness on structural and functional diversity of macrobenthic secondary producers were recorded. The results suggest that mixed seagrass meadows play an important role for ecosystem functioning and thus contribute to the provision of goods and services in coastal areas.     

Mycorrhizas and mycorrhizal fungal communities throughout ecosystem development

Background and scope

Plant communities and underlying soils undergo substantial, coordinated shifts throughout ecosystem development. However, shifts in the composition and function of mycorrhizal fungi remain poorly understood, despite their role as a major interface between plants and soil. We synthesise evidence for shifts among mycorrhizal types (i.e., ectomycorrhizas, arbuscular and ericoid mycorrhizas) and in fungal communities within mycorrhizal types along long-term chronosequences that include retrogressive stages. These systems represent strong, predictable patterns of increasing, then declining soil fertility during ecosystem development, and are associated with coordinated changes in plant and fungal functional traits and ecological processes.

Conclusions

Mycorrhizal types do not demonstrate consistent shifts through ecosystem development. Rather, most mycorrhizal types can dominate at any stage of ecosystem development, driven by biogeography (i.e., availability of mycorrhizal host species), plant community assembly, climate and other factors. In contrast to coordinated shifts in soil fertility, plant traits and ecological processes throughout ecosystem development, shifts in fungal communities within and among mycorrhizal types are weak or idiosyncratic. The consequences of these changes in mycorrhizal communities and their function for plant–soil feedbacks or control over long-term nutrient depletion remain poorly understood, but could be resolved through empirical analyses of long-term soil chronosequences.     

Functional diversity of ant-associated bacterial communities

It was found that ants significantly affect the physiological activity and functional diversity of soil microbial communities, and redistribution of biophilic elements (C and N) down through the profile occurs in anthills compared to the control soil, as well as their accumulation in the underground part of the ant nests. A high urease activity was revealed in ant nests and ants. Functional dissimilarities of bacterial communities in all studied objects were determined by the multisubstrate test.     

Phylogenetic relatedness predicts priority effects in nectar yeast communities

Priority effects, in which the outcome of species interactions depends on the order of their arrival, are a key component of many models of community assembly. Yet, much remains unknown about how priority effects vary in strength among species in a community and what factors explain this variation. We experimented with a model natural community in laboratory microcosms that allowed us to quantify the strength of priority effects for most of the yeast species found in the floral nectar of a hummingbird-pollinated shrub at a biological preserve in northern California. We found that priority effects were widespread, with late-arriving species experiencing strong negative effects from early-arriving species. However, the magnitude of priority effects varied across species pairs. This variation was phylogenetically non-random, with priority effects stronger between closer relatives. Analysis of carbon and amino acid consumption profiles indicated that competition between closer relatives was more intense owing to higher ecological similarity, consistent with Darwin's naturalization hypothesis. These results suggest that phylogenetic relatedness between potential colonists may explain the strength of priority effects and, as a consequence, the degree to which community assembly is historically contingent.     

Single-cell protein profiling of wastewater enterobacterial communities predicts disinfection efficiency

The efficiency of enterobacterial disinfection is dependent largely on enterobacterial community physiology. However, the relationship between enterobacterial community physiology and wastewater processing is unclear. The purpose of this study was to investigate this relationship. The influence of wastewater treatment processes on enterobacterial community physiology was examined at the single-cell level by using culture-independent methods. Intracellular concentrations of two conserved proteins, the growth-related protein Fis and the stationary-phase protein Dps, were analyzed by epifluoresence microscopy of uncultivated cells by using enterobacterial group-specific polyclonal fluorochrome-coupled antibodies. Enterobacterial single-cell community protein profiles were distinct for different types of biological treatment. The differences were not apparent when bulk methods of protein analysis were used. Trickling filter wastewater yielded Fis-enriched communities compared to the communities in submerged aeration basin wastewater. Community differences in Fis and Dps contents were used to predict disinfection efficiency. Disinfection of community samples by heat exposure combined with cultivation in selective media confirmed that enterobacterial communities exhibited significant differences in sensitivity to disinfection. These findings provide strategies that can be used to increase treatment plant performance, reduce the enterobacterial content in municipal wastewater, and minimize the release of disinfection by-products into receiving water.     

Functional properties and organization of grazing lands ecosystem

This paper describes the relationships between production, dominance, and species diversity on some semi-arid Indian grazing lands. The results of the data collected by harvest method show that dominance is directly related to production, and species diversity is inversely related to both production and dominance. An attempt is made to find the biological meaning for such interrelationships among these functional properties in terms of the niche and niche-space concept.     

From molecules to dynamic biological communities

Microbial ecology is flourishing, and in the process, is making contributions to how the ecology and biology of large organisms is understood. Ongoing advances in sequencing technology and computational methods have enabled the collection and analysis of vast amounts of molecular data from diverse biological communities. While early studies focused on cataloguing microbial biodiversity in environments ranging from simple marine ecosystems to complex soil ecologies, more recent research is concerned with community functions and their dynamics over time. Models and concepts from traditional ecology have been used to generate new insight into microbial communities, and novel system-level models developed to explain and predict microbial interactions. The process of moving from molecular inventories to functional understanding is complex and challenging, and never more so than when many thousands of dynamic interactions are the phenomena of interest. We outline the process of how epistemic transitions are made from producing catalogues of molecules to achieving functional and predictive insight, and show how those insights not only revolutionize what is known about biological systems but also about how to do biology itself. Examples will be drawn primarily from analyses of different human microbiota, which are the microbial consortia found in and on areas of the human body, and their associated microbiomes (the genes of those communities). Molecular knowledge of these microbiomes is transforming microbiological knowledge, as well as broader aspects of human biology, health and disease.     

Exotic plant communities shift water-use timing in a shrub-steppe ecosystem

Semiarid areas in the US have realized extensive and persistent exotic plant invasions. Exotics may succeed in arid regions by extracting soil water at different times or from different depths than native plants, but little data is available to test this hypothesis. Using estimates of root mass, gravimetric soil water, soil-water potential, and stable isotope ratios in soil and plant tissues, we determined water-use patterns of exotic and native plant species in exotic- and native-dominated communities in Washington State, USA. Exotic and native communities both extracted 12 ± 2 cm of water from the top 120 cm of soil during the growing season. Exotic communities, however, shifted the timing of water use by extracting surface (0–15 cm) soil water early in the growing season (i.e., April to May) before native plants were active, and by extracting deep (0–120 cm) soil water late in the growing season (i.e., June to July) after natives had undergone seasonal senescence. We found that δ ¹⁸O values of water in exotic annuals (e.g., −11.8 ± 0.4 ‰ for Bromus tectorum L.) were similar to δ ¹⁸O values of surface soil water (e.g., −13.3 ± 1.4 ‰ at −15 cm) suggesting that transpiration by these species explained early season, surface water use in exotic communities. We also found that δ ¹⁸O values of water in taprooted exotics (e.g., −17.4 ± 0.3 ‰ for Centaurea diffusa Lam.) were similar to δ ¹⁸O values of deep soil water (e.g., −18.4 ± 0.1 ‰ at −120 cm) suggesting that transpiration by these species explained late season, deep water use. The combination of early-season, shallow water-use by exotic winter-actives and late-season, deep water-use by taprooted perennials potentially explains how exotic communities resist establishment of native species that largely extracted soil water only in the middle of the growing season (i.e., May to June). Early season irrigation or the planting of natives with established root systems may allow native plant restoration.     

Short-term dynamics of bacterial communities in a tidally affected coastal ecosystem

Tidal effects on the composition of free-living (FL) and particle-associated (PA) bacterial communities were studied in a tidal flat ecosystem in the southern North Sea. Denaturing gradient gel electrophoresis targeting the 16S rRNA gene and the 16S rRNA of Bacteria, Bacteroidetes, Alphaproteobacteria and the Roseobacter clade was applied. Despite strong tidal variations in the quantity and, depending on the season, also the quality of suspended matter as well as variations in bacterial activity, the bacterial community composition remained rather stable. FISH showed some variations of the community composition, but these were not related to typical tidal situations. Variations were higher during tidal cycles in May and July compared with November. Bacteroidetes, Alpha- and Gammaproteobacteria constituted the majority of the bacterial communities but relative proportions of the different groups varied considerably. On particles, Betaproteobacteria were also detected to substantial proportions. The Roseobacter clade constituted up to 90% of FL but only 30% of PA Alphaproteobacteria. Banding patterns of the Bacteroidetes-specific amplicons, and in particular those targeting the 16S rRNA, revealed tidally induced effects, as several bands appeared or disappeared at distinct events such as slack water or resuspension. Sequencing of prominent bands revealed predominantly phylotypes reported previously from this ecosystem.