Effect of agricultural management regimes on Burkholderia community structure in soil

NARCIS (Netherlands)

Salles, Joanna; van Elsas, J.D.; Van Veen, J.A.

2006-01-01

The main objective of this study was to determine the Burkholderia community structure associated with areas under different agricultural management and to evaluate to which extent this community structure is affected by changes in agricultural management. Two fields with distinct soil history

Effect of agricultural management regime on Burkholderia community structure in soil

NARCIS (Netherlands)

Salles, J.F.; Elsas, van J.D.; Veen, van J.A.

2006-01-01

The main objective of this study was to determine the Burkholderia community structure associated with areas under different agricultural management and to evaluate to which extent this community structure is affected by changes in agricultural management. Two fields with distinct soil history

Effect of agricultural management regime on Burkholderia community structure in soil

NARCIS (Netherlands)

Salles, J. F.; van Elsas, J. D.; van Veen, J. A.

The main objective of this study was to determine the Burkholderia community structure associated with areas under different agricultural management and to evaluate to which extent this community structure is affected by changes in agricultural management. Two fields with distinct soil history

Apple orchard pest control strategies affect bird communities in southeastern France.

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Bouvier, Jean-Charles; Ricci, Benoît; Agerberg, Julia; Lavigne, Claire

2011-01-01

Birds are regarded as appropriate biological indicators of how changes in agricultural practices affect the environment. They are also involved in the biocontrol of pests. In the present study, we provide an assessment of the impact of pest control strategies on bird communities in apple orchards in southeastern France. We compared the structure (abundance, species richness, and diversity) of breeding bird communities in 15 orchards under conventional or organic pest control over a three-year period (2003-2005). Pest control strategies and their evolution over time were characterized by analyzing farmers' treatment schedules. The landscape surrounding the orchards was characterized using a Geographic Information System. We observed 30 bird species overall. Bird abundance, species richness, and diversity were all affected by pest control strategies, and were highest in organic orchards and lowest in conventional orchards during the three study years. The pest control strategy affected insectivores more than granivores. We further observed a tendency for bird communities in integrated pest management orchards to change over time and become increasingly different from communities in organic orchards, which also corresponded to changes in treatment schedules. These findings indicate that within-orchard bird communities may respond quickly to changes in pesticide use and may, in turn, influence biocontrol of pests by birds. © 2010 SETAC.

Optimal community structure for social contagions

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Su, Zhen; Wang, Wei; Li, Lixiang; Stanley, H. Eugene; Braunstein, Lidia A.

2018-05-01

Community structure is an important factor in the behavior of real-world networks because it strongly affects the stability and thus the phase transition order of the spreading dynamics. We here propose a reversible social contagion model of community networks that includes the factor of social reinforcement. In our model an individual adopts a social contagion when the number of received units of information exceeds its adoption threshold. We use mean-field approximation to describe our proposed model, and the results agree with numerical simulations. The numerical simulations and theoretical analyses both indicate that there is a first-order phase transition in the spreading dynamics, and that a hysteresis loop emerges in the system when there is a variety of initially adopted seeds. We find an optimal community structure that maximizes spreading dynamics. We also find a rich phase diagram with a triple point that separates the no-diffusion phase from the two diffusion phases.

Leveraging disjoint communities for detecting overlapping community structure

International Nuclear Information System (INIS)

Chakraborty, Tanmoy

2015-01-01

Network communities represent mesoscopic structure for understanding the organization of real-world networks, where nodes often belong to multiple communities and form overlapping community structure in the network. Due to non-triviality in finding the exact boundary of such overlapping communities, this problem has become challenging, and therefore huge effort has been devoted to detect overlapping communities from the network.In this paper, we present PVOC (Permanence based Vertex-replication algorithm for Overlapping Community detection), a two-stage framework to detect overlapping community structure. We build on a novel observation that non-overlapping community structure detected by a standard disjoint community detection algorithm from a network has high resemblance with its actual overlapping community structure, except the overlapping part. Based on this observation, we posit that there is perhaps no need of building yet another overlapping community finding algorithm; but one can efficiently manipulate the output of any existing disjoint community finding algorithm to obtain the required overlapping structure. We propose a new post-processing technique that by combining with any existing disjoint community detection algorithm, can suitably process each vertex using a new vertex-based metric, called permanence, and thereby finds out overlapping candidates with their community memberships. Experimental results on both synthetic and large real-world networks show that PVOC significantly outperforms six state-of-the-art overlapping community detection algorithms in terms of high similarity of the output with the ground-truth structure. Thus our framework not only finds meaningful overlapping communities from the network, but also allows us to put an end to the constant effort of building yet another overlapping community detection algorithm. (paper)

Temperature affects the size-structure of phytoplankton communities in the ocean

KAUST Repository

López-Urrutia, Ángel

2015-03-05

The strong inverse correlation between resource availability and temperature in the ocean poses a challenge to determine the relative effect of these two variables on the size-structure of natural phytoplankton communities. Maranon et al (2012) compiled a dataset of concurrent temperature and resource level proxies that they claim disentangled the effect of temperature from that of resource supply. They concluded that the hypothesis that temperature per se plays a direct role in controlling phytoplankton size structure should be rejected. But our reanalysis of their data reaches a very different conclusion and suggests that they failed to separate the effects of temperature from the effects of resources. Although we obviously concur with Maranon et al (2012) in the long-known predominance of small phytoplankton cells under oligotrophic conditions, from our point of view this should not deter us from considering temperature as an important explanatory variable at a global scale since we show that, for the vast oligotrophic areas of the world\\'s oceans where chlorophyll concentrations are below <1 g L-1 temperature explains a high proportion of the variability in the size distribution of phytoplankton communities, a variability that can not be explained on the basis of the resource level proxies advocated by Maranon et al. (2012).

Climatic and Environmental Changes Affecting Communities in Atlantic Canada

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Liette Vasseur

2017-07-01

Full Text Available Small rural coastal communities located in Atlantic Canada are vulnerable to the effects of climate and environmental changes. Major storms have impounded the coastline, causing much physical damage and affecting the socioeconomics of these communities that are composed of an aging population. The current study relays findings based on interviews completed in 2011–2012, following the 2010 winter storms in Atlantic Canada. It portrays the physical and social–ecological impacts affecting 10 coastal communities located in the provinces of Québec, New Brunswick, and Prince Edward Island. Semi-structured interviews held in these provinces are the basis for the contributions of this research. The findings reveal physical changes related to coastal erosion from high-wave impacts and storm surge causing flooding of the coastal zone. Also considered are strategies preferred and actually implemented by residents, such as building of protection walls, although undesirable. Due to funding constraints, however, many of these large-scale flood protection projects are not possible without governmental support. Instead, it is suggested that development be controlled and some respondents in this study upheld that relocation be used to alleviate the situation. Finally, more work is required to improve emergency planning. Better concerted short- and long-term responses need to be coordinated by local authorities and higher up in the government in order to ensure the sustainability of these coastal communities.

Landscape structure affects specialists but not generalists in naturally fragmented grasslands

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Miller, Jesse E.D.; Damschen, Ellen Ingman; Harrison, Susan P.; Grace, James B.

2015-01-01

Understanding how biotic communities respond to landscape spatial structure is critically important for conservation management as natural landscapes become increasingly fragmented. However, empirical studies of the effects of spatial structure on plant species richness have found inconsistent results, suggesting that more comprehensive approaches are needed. In this study, we asked how landscape structure affects total plant species richness and the richness of a guild of specialized plants in a multivariate context. We sampled herbaceous plant communities at 56 dolomite glades (insular, fire-adapted grasslands) across the Missouri Ozarks, and used structural equation modeling (SEM) to analyze the relative importance of landscape structure, soil resource availability, and fire history for plant communities. We found that landscape spatial structure-defined as the area-weighted proximity of glade habitat surrounding study sites (proximity index)-had a significant effect on total plant species richness, but only after we controlled for environmental covariates. Richness of specialist species, but not generalists, was positively related to landscape spatial structure. Our results highlight that local environmental filters must be considered to understand the influence of landscape structure on communities, and that unique species guilds may respond differently to landscape structure than the community as a whole. These findings suggest that both local environment and landscape context should be considered when developing management strategies for species of conservation concern in fragmented habitats.

Epidemic spreading on complex networks with overlapping and non-overlapping community structure

Science.gov (United States)

Shang, Jiaxing; Liu, Lianchen; Li, Xin; Xie, Feng; Wu, Cheng

2015-02-01

Many real-world networks exhibit community structure where vertices belong to one or more communities. Recent studies show that community structure plays an import role in epidemic spreading. In this paper, we investigate how the extent of overlap among communities affects epidemics. In order to experiment on the characteristic of overlapping communities, we propose a rewiring algorithm that can change the community structure from overlapping to non-overlapping while maintaining the degree distribution of the network. We simulate the Susceptible-Infected-Susceptible (SIS) epidemic process on synthetic scale-free networks and real-world networks by applying our rewiring algorithm. Experiments show that epidemics spread faster on networks with higher level of overlapping communities. Furthermore, overlapping communities' effect interacts with the average degree's effect. Our work further illustrates the important role of overlapping communities in the process of epidemic spreading.

Mesoherbivores affect grasshopper communities in a megaherbivore-dominated South African savannah.

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van der Plas, Fons; Olff, Han

2014-06-01

African savannahs are among the few places on earth where diverse communities of mega- and meso-sized ungulate grazers dominate ecosystem functioning. Less conspicuous, but even more diverse, are the communities of herbivorous insects such as grasshoppers, which share the same food. Various studies investigated the community assembly of these groups separately, but it is poorly known how ungulate communities shape grasshopper communities. Here, we investigated how ungulate species of different body size alter grasshopper communities in a South African savannah. White rhino is the most abundant vertebrate herbivore in our study site. Other common mesoherbivores include buffalo, zebra and impala. We hypothesized that white rhinos would have greater impact than mesoherbivores on grasshopper communities. Using 10-year-old exclosures, at eight sites we compared the effects of ungulates on grasshopper communities in three nested treatments: (i) unfenced plots ('control plots') with all vertebrate herbivores present, (ii) plots with a low cable fence, excluding white rhino ('megaherbivore exclosures'), and (iii) plots with tall fences, excluding all herbivores larger than rodents ('complete ungulate exclosures'). In each plot, we collected data of vegetation structure, grass and grasshopper community composition. Complete ungulate exclosures contained 30% taller vegetation than megaherbivore exclosures and they were dominated by different grass and grasshopper species. Grasshoppers in complete ungulate exclosures were on average 3.5 mm longer than grasshoppers in megaherbivore exclosures, possibly due to changes in plant communities or vegetation structure. We conclude that surprisingly, in this megaherbivore hotspot, mesoherbivores, instead of megaherbivores, most strongly affect grasshopper communities.

The effect of salinity levels on the structure of zooplankton communities

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Paturej Ewa

2015-01-01

Full Text Available The objective of this study was to determine the qualitative and quantitative structure of zooplankton communities in the Vistula Lagoon and to establish whether zooplankton abundance and biodiversity are affected by salinity levels. Samples for biological analyses were collected in the summer (June-September of 2007-2011 at eleven sampling sites. Statistical analysis revealed a significant correlation between salinity levels and the number of species (r= -0.2020, abundance (r= 0.1967 and biomass (r= 0.3139 of zooplankton. No significant correlations were found between salinity and the biodiversity of zooplankton. The results of the study suggest that salinity affects the abundance and structure, but not the diversity of zooplankton communities in the Vistula Lagoon.

Differential responses of nitrate reducer community size, structure, and activity to tillage systems.

Science.gov (United States)

Chèneby, D; Brauman, A; Rabary, B; Philippot, L

2009-05-01

The main objective of this study was to determine how the size, structure, and activity of the nitrate reducer community were affected by adoption of a conservative tillage system as an alternative to conventional tillage. The experimental field, established in Madagascar in 1991, consists of plots subjected to conventional tillage or direct-seeding mulch-based cropping systems (DM), both amended with three different fertilization regimes. Comparisons of size, structure, and activity of the nitrate reducer community in samples collected from the top layer in 2005 and 2006 revealed that all characteristics of this functional community were affected by the tillage system, with increased nitrate reduction activity and numbers of nitrate reducers under DM. Nitrate reduction activity was also stimulated by combined organic and mineral fertilization but not by organic fertilization alone. In contrast, both negative and positive effects of combined organic and mineral fertilization on the size of the nitrate reducer community were observed. The size of the nitrate reducer community was a significant predictor of the nitrate reduction rates except in one treatment, which highlighted the inherent complexities in understanding the relationships the between size, diversity, and structure of functional microbial communities along environmental gradients.

Grazing exclusion, substrate type, and drought frequency affect plant community structure in rangelands of the arid unpredictable Arabian Deserts

Science.gov (United States)

El-Keblawy, Ali; El-Sheikh, Mohamed

2017-04-01

Grazing and drought can adversely affect the ecology and management of rangeland ecosystems. Several management actions have been applied to restore species diversity and community structure in degraded rangelands of the unpredictable arid environment. Protection from grazing is considered as a proper approach for restoration of degraded rangelands, but this depends on substrate type and sometime is hindered with water deficiency (drought). In this study, the effect of protection from grazing animals on species diversity and plant community structure was assessed after a dry and wet periods in both sandy and gravelly substrates in the Dubai Desert Conservation reserve (DDCR), United Arab Emirates. Two sites were selected during November 2012 on the two substrate types (fixed sandy flat and gravel plain) in the arid DDCR. An enclosure was established in each site. Plant community attributes (plant cover, density, frequency, species composition, and diversity indices) were assessed in a number of permanent plots laid inside and outside each enclosure during November 2012, April 2014 and April 2016. The results showed that protection improved clay content, but decreased the organic matters. Interestingly, the protection reduced the concentrations of most estimated nutrients, which could be attributed to the high turnover rate of nutrients associated grazing and low decomposition of accumulated dry plants of non-protected sites. Protection significantly increased all plant community attributes, but the only significant effect was for plant density. Plant density was almost twice greater inside than outside the enclosures. During the dry period, protection resulted in significantly greater deterioration in cover, density and all diversity indices in gravel, compared to sandy sites. Most of the grasses and shrubby plants had died in the gravel plains. However, plant community of the gravel plains was significantly restored after receiving considerable rainfalls. The

Dominant Tree Species and Soil Type Affect the Fungal Community Structure in a Boreal Peatland Forest.

Science.gov (United States)

Sun, Hui; Terhonen, Eeva; Kovalchuk, Andriy; Tuovila, Hanna; Chen, Hongxin; Oghenekaro, Abbot O; Heinonsalo, Jussi; Kohler, Annegret; Kasanen, Risto; Vasander, Harri; Asiegbu, Fred O

2016-05-01

Boreal peatlands play a crucial role in global carbon cycling, acting as an important carbon reservoir. However, little information is available on how peatland microbial communities are influenced by natural variability or human-induced disturbances. In this study, we have investigated the fungal diversity and community structure of both the organic soil layer and buried wood in boreal forest soils using high-throughput sequencing of the internal transcribed spacer (ITS) region. We have also compared the fungal communities during the primary colonization of wood with those of the surrounding soils. A permutational multivariate analysis of variance (PERMANOVA) confirmed that the community composition significantly differed between soil types (P< 0.001) and tree species (P< 0.001). The distance-based linear models analysis showed that environmental variables were significantly correlated with community structure (P< 0.04). The availability of soil nutrients (Ca [P= 0.002], Fe [P= 0.003], and P [P= 0.003]) within the site was an important factor in the fungal community composition. The species richness in wood was significantly lower than in the corresponding soil (P< 0.004). The results of the molecular identification were supplemented by fruiting body surveys. Seven of the genera of Agaricomycotina identified in our surveys were among the top 20 genera observed in pyrosequencing data. Our study is the first, to our knowledge, fungal high-throughput next-generation sequencing study performed on peatlands; it further provides a baseline for the investigation of the dynamics of the fungal community in the boreal peatlands. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Dominant Tree Species and Soil Type Affect the Fungal Community Structure in a Boreal Peatland Forest

Science.gov (United States)

Terhonen, Eeva; Kovalchuk, Andriy; Tuovila, Hanna; Chen, Hongxin; Oghenekaro, Abbot O.; Heinonsalo, Jussi; Kohler, Annegret; Kasanen, Risto; Vasander, Harri; Asiegbu, Fred O.

2016-01-01

Boreal peatlands play a crucial role in global carbon cycling, acting as an important carbon reservoir. However, little information is available on how peatland microbial communities are influenced by natural variability or human-induced disturbances. In this study, we have investigated the fungal diversity and community structure of both the organic soil layer and buried wood in boreal forest soils using high-throughput sequencing of the internal transcribed spacer (ITS) region. We have also compared the fungal communities during the primary colonization of wood with those of the surrounding soils. A permutational multivariate analysis of variance (PERMANOVA) confirmed that the community composition significantly differed between soil types (P peatlands; it further provides a baseline for the investigation of the dynamics of the fungal community in the boreal peatlands. PMID:26896139

Convergent evolution of modularity in metabolic networks through different community structures

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Zhou Wanding

2012-09-01

Full Text Available Abstract Background It has been reported that the modularity of metabolic networks of bacteria is closely related to the variability of their living habitats. However, given the dependency of the modularity score on the community structure, it remains unknown whether organisms achieve certain modularity via similar or different community structures. Results In this work, we studied the relationship between similarities in modularity scores and similarities in community structures of the metabolic networks of 1021 species. Both similarities are then compared against the genetic distances. We revisited the association between modularity and variability of the microbial living environments and extended the analysis to other aspects of their life style such as temperature and oxygen requirements. We also tested both topological and biological intuition of the community structures identified and investigated the extent of their conservation with respect to the taxomony. Conclusions We find that similar modularities are realized by different community structures. We find that such convergent evolution of modularity is closely associated with the number of (distinct enzymes in the organism’s metabolome, a consequence of different life styles of the species. We find that the order of modularity is the same as the order of the number of the enzymes under the classification based on the temperature preference but not on the oxygen requirement. Besides, inspection of modularity-based communities reveals that these communities are graph-theoretically meaningful yet not reflective of specific biological functions. From an evolutionary perspective, we find that the community structures are conserved only at the level of kingdoms. Our results call for more investigation into the interplay between evolution and modularity: how evolution shapes modularity, and how modularity affects evolution (mainly in terms of fitness and evolvability. Further, our results

Convergent evolution of modularity in metabolic networks through different community structures.

Science.gov (United States)

Zhou, Wanding; Nakhleh, Luay

2012-09-14

It has been reported that the modularity of metabolic networks of bacteria is closely related to the variability of their living habitats. However, given the dependency of the modularity score on the community structure, it remains unknown whether organisms achieve certain modularity via similar or different community structures. In this work, we studied the relationship between similarities in modularity scores and similarities in community structures of the metabolic networks of 1021 species. Both similarities are then compared against the genetic distances. We revisited the association between modularity and variability of the microbial living environments and extended the analysis to other aspects of their life style such as temperature and oxygen requirements. We also tested both topological and biological intuition of the community structures identified and investigated the extent of their conservation with respect to the taxonomy. We find that similar modularities are realized by different community structures. We find that such convergent evolution of modularity is closely associated with the number of (distinct) enzymes in the organism's metabolome, a consequence of different life styles of the species. We find that the order of modularity is the same as the order of the number of the enzymes under the classification based on the temperature preference but not on the oxygen requirement. Besides, inspection of modularity-based communities reveals that these communities are graph-theoretically meaningful yet not reflective of specific biological functions. From an evolutionary perspective, we find that the community structures are conserved only at the level of kingdoms. Our results call for more investigation into the interplay between evolution and modularity: how evolution shapes modularity, and how modularity affects evolution (mainly in terms of fitness and evolvability). Further, our results call for exploring new measures of modularity and network

The role of macrobiota in structuring microbial communities along rocky shores

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Catherine A. Pfister

2014-10-01

Full Text Available Rocky shore microbial diversity presents an excellent system to test for microbial habitat specificity or generality, enabling us to decipher how common macrobiota shape microbial community structure. At two coastal locations in the northeast Pacific Ocean, we show that microbial composition was significantly different between inert surfaces, the biogenic surfaces that included rocky shore animals and an alga, and the water column plankton. While all sampled entities had a core of common OTUs, rare OTUs drove differences among biotic and abiotic substrates. For the mussel Mytilus californianus, the shell surface harbored greater alpha diversity compared to internal tissues of the gill and siphon. Strikingly, a 7-year experimental removal of this mussel from tidepools did not significantly alter the microbial community structure of microbes associated with inert surfaces when compared with unmanipulated tidepools. However, bacterial taxa associated with nitrate reduction had greater relative abundance with mussels present, suggesting an impact of increased animal-derived nitrogen on a subset of microbial metabolism. Because the presence of mussels did not affect the structure and diversity of the microbial community on adjacent inert substrates, microbes in this rocky shore environment may be predominantly affected through direct physical association with macrobiota.

Lead pollution in a large, prairie-pothole lake (Rush Lake, WI, USA): Effects on abundance and community structure of indigenous sediment bacteria

International Nuclear Information System (INIS)

Grandlic, Christopher J.; Geib, Ian; Pilon, Renee; Sandrin, Todd R.

2006-01-01

Rush Lake (WI, USA), the largest prairie-pothole lake east of the Mississippi River, has been contaminated with lead pollution as a result of over 140 years of waterfowl hunting. We examined: (1) the extent of lead pollution in Rush Lake sediments and (2) whether lead pollution in Rush Lake is affecting the abundance and community structure of indigenous sediment bacteria. Sediment lead concentrations did not exceed 59 mg Pb kg -1 dry sediment. No relationship was observed between sediment lead concentration and the abundance of aerobic (P = 0.498) or anaerobic (P = 0.416) heterotrophic bacteria. Similarly, lead did not appear to affect bacterial community structure when considering both culturable and nonculturable community members. In contrast, the culturable fraction of sediment bacteria in samples containing 59 mg Pb kg -1 exhibited a unique community structure. While factors other than lead content likely play roles in determining bacterial community structure in the sediments of Rush Lake, these data suggest that the culturable fraction of sediment bacterial communities is affected by elevated lead levels. - Low levels of lead pollution in Rush Lake are not impinging upon the abundance of indigenous sediment bacteria, but may be affecting the community structure of the culturable fraction of these bacteria

Fertilization Shapes Bacterial Community Structure by Alteration of Soil pH

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Yuting Zhang

2017-07-01

Full Text Available Application of chemical fertilizer or manure can affect soil microorganisms directly by supplying nutrients and indirectly by altering soil pH. However, it remains uncertain which effect mostly shapes microbial community structure. We determined soil bacterial diversity and community structure by 454 pyrosequencing the V1-V3 regions of 16S rRNA genes after 7-years (2007–2014 of applying chemical nitrogen, phosphorus and potassium (NPK fertilizers, composted manure or their combination to acidic (pH 5.8, near-neutral (pH 6.8 or alkaline (pH 8.4 Eutric Regosol soil in a maize-vegetable rotation in southwest China. In alkaline soil, nutrient sources did not affect bacterial Operational Taxonomic Unit (OTU richness or Shannon diversity index, despite higher available N, P, K, and soil organic carbon in fertilized than in unfertilized soil. In contrast, bacterial OTU richness and Shannon diversity index were significantly lower in acidic and near-neutral soils under NPK than under manure or their combination, which corresponded with changes in soil pH. Permutational multivariate analysis of variance showed that bacterial community structure was significantly affected across these three soils, but the PCoA ordination patterns indicated the effect was less distinct among nutrient sources in alkaline than in acidic and near-neural soils. Distance-based redundancy analysis showed that bacterial community structures were significantly altered by soil pH in acidic and near-neutral soils, but not by any soil chemical properties in alkaline soil. The relative abundance (% of most bacterial phyla was higher in near-neutral than in acidic or alkaline soils. The most dominant phyla were Proteobacteria (24.6%, Actinobacteria (19.7%, Chloroflexi (15.3% and Acidobacteria (12.6%; the medium dominant phyla were Bacterioidetes (5.3%, Planctomycetes (4.8%, Gemmatimonadetes (4.5%, Firmicutes (3.4%, Cyanobacteria (2.1%, Nitrospirae (1.8%, and candidate division TM7 (1

Fertilization Shapes Bacterial Community Structure by Alteration of Soil pH.

Science.gov (United States)

Zhang, Yuting; Shen, Hong; He, Xinhua; Thomas, Ben W; Lupwayi, Newton Z; Hao, Xiying; Thomas, Matthew C; Shi, Xiaojun

2017-01-01

Application of chemical fertilizer or manure can affect soil microorganisms directly by supplying nutrients and indirectly by altering soil pH. However, it remains uncertain which effect mostly shapes microbial community structure. We determined soil bacterial diversity and community structure by 454 pyrosequencing the V1-V3 regions of 16S rRNA genes after 7-years (2007-2014) of applying chemical nitrogen, phosphorus and potassium (NPK) fertilizers, composted manure or their combination to acidic (pH 5.8), near-neutral (pH 6.8) or alkaline (pH 8.4) Eutric Regosol soil in a maize-vegetable rotation in southwest China. In alkaline soil, nutrient sources did not affect bacterial Operational Taxonomic Unit (OTU) richness or Shannon diversity index, despite higher available N, P, K, and soil organic carbon in fertilized than in unfertilized soil. In contrast, bacterial OTU richness and Shannon diversity index were significantly lower in acidic and near-neutral soils under NPK than under manure or their combination, which corresponded with changes in soil pH. Permutational multivariate analysis of variance showed that bacterial community structure was significantly affected across these three soils, but the PCoA ordination patterns indicated the effect was less distinct among nutrient sources in alkaline than in acidic and near-neural soils. Distance-based redundancy analysis showed that bacterial community structures were significantly altered by soil pH in acidic and near-neutral soils, but not by any soil chemical properties in alkaline soil. The relative abundance (%) of most bacterial phyla was higher in near-neutral than in acidic or alkaline soils. The most dominant phyla were Proteobacteria (24.6%), Actinobacteria (19.7%), Chloroflexi (15.3%) and Acidobacteria (12.6%); the medium dominant phyla were Bacterioidetes (5.3%), Planctomycetes (4.8%), Gemmatimonadetes (4.5%), Firmicutes (3.4%), Cyanobacteria (2.1%), Nitrospirae (1.8%), and candidate division TM7 (1

Impact of organic and inorganic nanomaterials in the soil microbial community structure

Energy Technology Data Exchange (ETDEWEB)

Nogueira, Veronica; Lopes, Isabel [Department of Biology, University of Aveiro, Campus Universitario de Santiago, P-3810-193 Aveiro (Portugal); CESAM (Centre for Environmental and Marine Studies), University of Aveiro, Campus de Santiago 3810-193 Aveiro (Portugal); Rocha-Santos, Teresa [ISEIT/Viseu, Instituto Piaget, Estrada do Alto do Gaio, Galifonge, 3515-776 Lordosa, Viseu (Portugal); Santos, Ana L. [Department of Biology, University of Aveiro, Campus Universitario de Santiago, P-3810-193 Aveiro (Portugal); CESAM (Centre for Environmental and Marine Studies), University of Aveiro, Campus de Santiago 3810-193 Aveiro (Portugal); Rasteiro, Graca M.; Antunes, Filipe [CIEPQPF, Department of Chemical Engineering, Faculty of Science and Technology, Polo II, University of Coimbra, 3030-290 Coimbra (Portugal); Goncalves, Fernando; Soares, Amadeu M.V.M.; Cunha, Angela; Almeida, Adelaide [Department of Biology, University of Aveiro, Campus Universitario de Santiago, P-3810-193 Aveiro (Portugal); CESAM (Centre for Environmental and Marine Studies), University of Aveiro, Campus de Santiago 3810-193 Aveiro (Portugal); Gomes, Newton N.C.M., E-mail: gomesncm@ua.pt [Department of Biology, University of Aveiro, Campus Universitario de Santiago, P-3810-193 Aveiro (Portugal); CESAM (Centre for Environmental and Marine Studies), University of Aveiro, Campus de Santiago 3810-193 Aveiro (Portugal); Pereira, Ruth [Department of Biology, Faculty of Science, University of Porto, Rua do Campo Alegre 4169-007 Porto (Portugal); CESAM (Centre for Environmental and Marine Studies), University of Aveiro, Campus de Santiago 3810-193 Aveiro (Portugal)

2012-05-01

In this study the effect of organic and inorganic nanomaterials (NMs) on the structural diversity of the soil microbial community was investigated by Denaturing Gradient Gel Electrophoresis, after amplification with universal primers for the bacterial region V6-V8 of 16S rDNA. The polymers of carboxylmethyl-cellulose (CMC), of hydrophobically modified CMC (HM-CMC), and hydrophobically modified polyethylglycol (HM-PEG); the vesicles of sodium dodecyl sulphate/didodecyl dimethylammonium bromide (SDS/DDAB) and of monoolein/sodium oleate (Mo/NaO); titanium oxide (TiO{sub 2}), titanium silicon oxide (TiSiO{sub 4}), CdSe/ZnS quantum dots, gold nanorods, and Fe/Co magnetic fluid were the NMs tested. Soil samples were incubated, for a period of 30 days, after being spiked with NM suspensions previously characterized by Dynamic Light Scattering (DLS) or by an ultrahigh-resolution scanning electron microscope (SEM). The analysis of similarities (ANOSIM) of DGGE profiles showed that gold nanorods, TiO{sub 2}, CMC, HM-CMC, HM-PEG, and SDS/DDAB have significantly affected the structural diversity of the soil bacterial community. - Highlights: Black-Right-Pointing-Pointer Organic and inorganic nanomaterials on soil microbial community. Black-Right-Pointing-Pointer Structural diversity was investigated by Denaturing Gradient Gel Electrophoresis. Black-Right-Pointing-Pointer All the organic nanomaterials, TiO{sub 2} and gold nanorods significantly affected the structural diversity.

Impact of organic and inorganic nanomaterials in the soil microbial community structure

International Nuclear Information System (INIS)

Nogueira, Verónica; Lopes, Isabel; Rocha-Santos, Teresa; Santos, Ana L.; Rasteiro, Graça M.; Antunes, Filipe; Gonçalves, Fernando; Soares, Amadeu M.V.M.; Cunha, Angela; Almeida, Adelaide; Gomes, Newton N.C.M.; Pereira, Ruth

2012-01-01

In this study the effect of organic and inorganic nanomaterials (NMs) on the structural diversity of the soil microbial community was investigated by Denaturing Gradient Gel Electrophoresis, after amplification with universal primers for the bacterial region V6–V8 of 16S rDNA. The polymers of carboxylmethyl-cellulose (CMC), of hydrophobically modified CMC (HM-CMC), and hydrophobically modified polyethylglycol (HM-PEG); the vesicles of sodium dodecyl sulphate/didodecyl dimethylammonium bromide (SDS/DDAB) and of monoolein/sodium oleate (Mo/NaO); titanium oxide (TiO 2 ), titanium silicon oxide (TiSiO 4 ), CdSe/ZnS quantum dots, gold nanorods, and Fe/Co magnetic fluid were the NMs tested. Soil samples were incubated, for a period of 30 days, after being spiked with NM suspensions previously characterized by Dynamic Light Scattering (DLS) or by an ultrahigh-resolution scanning electron microscope (SEM). The analysis of similarities (ANOSIM) of DGGE profiles showed that gold nanorods, TiO 2 , CMC, HM-CMC, HM-PEG, and SDS/DDAB have significantly affected the structural diversity of the soil bacterial community. - Highlights: ► Organic and inorganic nanomaterials on soil microbial community. ► Structural diversity was investigated by Denaturing Gradient Gel Electrophoresis. ► All the organic nanomaterials, TiO 2 and gold nanorods significantly affected the structural diversity.

Do Amplitudes of Water Level Fluctuations Affect the Growth and Community Structure of Submerged Macrophytes?

Science.gov (United States)

Wang, Mo-Zhu; Liu, Zheng-Yuan; Luo, Fang-Li; Lei, Guang-Chun; Li, Hong-Li

2016-01-01

Submerged macrophytes are subjected to potential mechanical stresses associated with fluctuating water levels in natural conditions. However, few experimental studies have been conducted to further understand the effects of water level fluctuating amplitude on submerged macrophyte species and their assemblages or communities. We designed a controlled experiment to investigate the responses of three submerged macrophyte species (Hydrilla verticillata, Ceratophyllum demersum and Elodea nuttallii) and their combinations in communities to three amplitudes (static, ± 30 cm, ± 60 cm) of water level fluctuations. Results showed that water level fluctuating amplitude had little effects on the community performance and the three tested species responded differently. H. verticillata exhibited more growth in static water and it was negatively affected by either of the water level fluctuations amplitude, however, growth parameters of H. verticillata in two fluctuating water level treatments (i.e., ± 30 cm, ± 60 cm) were not significantly different. On the other hand, the growth of C. demersum was not significantly correlated with different amplitude treatments. However, it became more abundant when water levels fluctuated. E. nuttallii was inhibited by the two fluctuating water level treatments, and was less in growth parameters compared to the other species especially in water level fluctuating conditions. The inherent differences in the adaptive capabilities of the tested species indicate that C. demersum or other species with similar responses may be dominant species to restore submerged macrophyte communities with great fluctuating water levels. Otherwise, H. verticillata, E. nuttallii or other species with similar responses could be considered for constructing the community in static water conditions. PMID:26735689

Do Amplitudes of Water Level Fluctuations Affect the Growth and Community Structure of Submerged Macrophytes?

Science.gov (United States)

Wang, Mo-Zhu; Liu, Zheng-Yuan; Luo, Fang-Li; Lei, Guang-Chun; Li, Hong-Li

2016-01-01

Submerged macrophytes are subjected to potential mechanical stresses associated with fluctuating water levels in natural conditions. However, few experimental studies have been conducted to further understand the effects of water level fluctuating amplitude on submerged macrophyte species and their assemblages or communities. We designed a controlled experiment to investigate the responses of three submerged macrophyte species (Hydrilla verticillata, Ceratophyllum demersum and Elodea nuttallii) and their combinations in communities to three amplitudes (static, ± 30 cm, ± 60 cm) of water level fluctuations. Results showed that water level fluctuating amplitude had little effects on the community performance and the three tested species responded differently. H. verticillata exhibited more growth in static water and it was negatively affected by either of the water level fluctuations amplitude, however, growth parameters of H. verticillata in two fluctuating water level treatments (i.e., ± 30 cm, ± 60 cm) were not significantly different. On the other hand, the growth of C. demersum was not significantly correlated with different amplitude treatments. However, it became more abundant when water levels fluctuated. E. nuttallii was inhibited by the two fluctuating water level treatments, and was less in growth parameters compared to the other species especially in water level fluctuating conditions. The inherent differences in the adaptive capabilities of the tested species indicate that C. demersum or other species with similar responses may be dominant species to restore submerged macrophyte communities with great fluctuating water levels. Otherwise, H. verticillata, E. nuttallii or other species with similar responses could be considered for constructing the community in static water conditions.

Do Amplitudes of Water Level Fluctuations Affect the Growth and Community Structure of Submerged Macrophytes?

Directory of Open Access Journals (Sweden)

Mo-Zhu Wang

Full Text Available Submerged macrophytes are subjected to potential mechanical stresses associated with fluctuating water levels in natural conditions. However, few experimental studies have been conducted to further understand the effects of water level fluctuating amplitude on submerged macrophyte species and their assemblages or communities. We designed a controlled experiment to investigate the responses of three submerged macrophyte species (Hydrilla verticillata, Ceratophyllum demersum and Elodea nuttallii and their combinations in communities to three amplitudes (static, ± 30 cm, ± 60 cm of water level fluctuations. Results showed that water level fluctuating amplitude had little effects on the community performance and the three tested species responded differently. H. verticillata exhibited more growth in static water and it was negatively affected by either of the water level fluctuations amplitude, however, growth parameters of H. verticillata in two fluctuating water level treatments (i.e., ± 30 cm, ± 60 cm were not significantly different. On the other hand, the growth of C. demersum was not significantly correlated with different amplitude treatments. However, it became more abundant when water levels fluctuated. E. nuttallii was inhibited by the two fluctuating water level treatments, and was less in growth parameters compared to the other species especially in water level fluctuating conditions. The inherent differences in the adaptive capabilities of the tested species indicate that C. demersum or other species with similar responses may be dominant species to restore submerged macrophyte communities with great fluctuating water levels. Otherwise, H. verticillata, E. nuttallii or other species with similar responses could be considered for constructing the community in static water conditions.

Structure and composition of oligohaline marsh plant communities exposed to salinity pulses

Science.gov (United States)

Howard, R.J.; Mendelssohn, I.A.

2000-01-01

The response of two oligohaline marsh macrophyte communities to pulses of increased salinity was studied over a single growing season in a greenhouse experiment. The plant communities were allowed a recovery period in freshwater following the pulse events. The experimental treatments included: (1) salinity influx rate (rate of salinity increase from 0 to 12 gl-1); (2) duration of exposure to elevated salinity; and (3) water depth. The communities both included Sagittaria lancifolia L.; the codominant species were Eleocharis palustris (L.) Roemer and J.A. Schultes in community 1 and Schoenoplectus americanus (Pers.) Volk. ex Schinz and R. Keller in community 2. Effects of the treatments on sediment chemical characteristics (salinity, pH, redox potential, and sulfide and ammonium concentrations) and plant community attributes (aboveground and belowground biomass, stem density, leaf tissue nutrients, and species richness) were examined. The treatment effects often interacted to influence sediment and plant communities characteristics following recovery in fresh water. Salinity influx rate per se, however, had little effect on the abiotic or biotic response variables; significant influx effects were found when the 0 gl-1 (zero influx) treatment was compared to the 12 gl-1 treatments, regardless of the rate salinity was raised. A salinity level of 12 gl-1 had negative effects on plant community structure and composition; these effects were usually associated with 3 months of salinity exposure. Water depth often interacted with exposure duration, but increased water depth did independently decrease the values of some community response measures. Community 1 was affected more than community 2 in the most extreme salinity treatment (3 months exposure/15-cm water depth). Although species richness in both communities was reduced, structural changes were more dramatic in community 1. Biomass and stem density were reduced in community 1 overall and in both dominant species

Herbivory of an invasive slug is affected by earthworms and the composition of plant communities.

Science.gov (United States)

Zaller, Johann G; Parth, Myriam; Szunyogh, Ilona; Semmelrock, Ines; Sochurek, Susanne; Pinheiro, Marcia; Frank, Thomas; Drapela, Thomas

2013-05-13

species but little influenced by earthworms. Overall shoot biomass was decreased, root biomass increased in plant communities with more plant species. Earthworms decreased total shoot biomass in mesocosms with more plant species but did not affect biomass production of individual functional groups. Plant nitrogen concentrations across three focus species were 18% higher when earthworms were present; composition of plant communities did not affect plant quality. Given the important role that both herbivores and earthworms play in structuring plant communities the implications of belowground-aboveground linkages should more broadly be considered when investigating global change effects on ecosystems.

Extinction order and altered community structure rapidly disrupt ecosystem functioning.

Science.gov (United States)

Larsen, Trond H; Williams, Neal M; Kremen, Claire

2005-05-01

By causing extinctions and altering community structure, anthropogenic disturbances can disrupt processes that maintain ecosystem integrity. However, the relationship between community structure and ecosystem functioning in natural systems is poorly understood. Here we show that habitat loss appeared to disrupt ecosystem functioning by affecting extinction order, species richness and abundance. We studied pollination by bees in a mosaic of agricultural and natural habitats in California and dung burial by dung beetles on recently created islands in Venezuela. We found that large-bodied bee and beetle species tended to be both most extinction-prone and most functionally efficient, contributing to rapid functional loss. Simulations confirmed that extinction order led to greater disruption of function than predicted by random species loss. Total abundance declined with richness and also appeared to contribute to loss of function. We demonstrate conceptually and empirically how the non-random response of communities to disturbance can have unexpectedly large functional consequences.

Structure of Fungal Communities in Sub-Irrigated Agricultural Soil from Cerrado Floodplains

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Elainy Cristina A. M. Oliveira

2016-05-01

Full Text Available This study aimed to evaluate the influence of soybean cultivation on the fungal community structure in a tropical floodplain area. Soil samples were collected from two different soybean cropland sites and a control area under native vegetation. The soil samples were collected at a depth of 0–10 cm soil during the off-season in July 2013. The genetic structure of the soil fungal microbial community was analyzed using the automated ribosomal intergenic spacer analysis (ARISA technique. Among the 26 phylotypes with abundance levels higher than 1% detected in the control area, five were also detected in the area cultivated for five years, and none of them was shared between the control area and the area cultivated for eight years. Analysis of similarity (ANOSIM revealed differences in fungal community structure between the control area and the soybean cropland sites, and also between the soybean cropland sites. ANOSIM results were confirmed by multivariate statistics, which additionally revealed a nutrient-dependent relation for the fungal community structure in agricultural soil managed for eight consecutive years. The results indicated that land use affects soil chemical properties and richness and structure of the soil fungal microbial community in a tropical floodplain agricultural area, and the effects became more evident to the extent that soil was cultivated for soybean for more time.

Vegetative Propagule Pressure and Water Depth Affect Biomass and Evenness of Submerged Macrophyte Communities.

Science.gov (United States)

Li, Hong-Li; Wang, Yong-Yang; Zhang, Qian; Wang, Pu; Zhang, Ming-Xiang; Yu, Fei-Hai

2015-01-01

Vegetative propagule pressure may affect the establishment and structure of aquatic plant communities that are commonly dominated by plants capable of clonal growth. We experimentally constructed aquatic communities consisting of four submerged macrophytes (Hydrilla verticillata, Ceratophyllum demersum, Elodea nuttallii and Myriophyllum spicatum) with three levels of vegetative propagule pressure (4, 8 and 16 shoot fragments for communities in each pot) and two levels of water depth (30 cm and 70 cm). Increasing vegetative propagule pressure and decreasing water level significantly increased the growth of the submerged macrophyte communities, suggesting that propagule pressure and water depth should be considered when utilizing vegetative propagules to re-establish submerged macrophyte communities in degraded aquatic ecosystems. However, increasing vegetative propagule pressure and decreasing water level significantly decreased evenness of the submerged macrophyte communities because they markedly increased the dominance of H. verticillata and E. nuttallii, but had little impact on that of C. demersum and M. spicatum. Thus, effects of vegetative propagule pressure and water depth are species-specific and increasing vegetative propagule pressure under lower water level can facilitate the establishment success of submerged macrophyte communities.

Alginate overproduction affects Pseudomonas aeruginosa biofilm structure and function

DEFF Research Database (Denmark)

Hentzer, Morten; Teitzel, G.M.; Balzer, G.J.

2001-01-01

-resistant communities of microorganisms organized in biofilms. Although biofilm formation and the conversion to mucoidy are both important aspects of CF pathogenesis, the relationship between them is at the present unclear. In this study, we report that the overproduction of alginate affects biofilm development...... on an abiotic surface. Biofilms formed by an alginate- overproducing strain exhibit a highly structured architecture and are significantly more resistant to the antibiotic tobramycin than a biofilm formed by an isogenic nonmucoid strain. These results suggest that an important consequence of the conversion...

An evolving network model with community structure

International Nuclear Information System (INIS)

Li Chunguang; Maini, Philip K

2005-01-01

Many social and biological networks consist of communities-groups of nodes within which connections are dense, but between which connections are sparser. Recently, there has been considerable interest in designing algorithms for detecting community structures in real-world complex networks. In this paper, we propose an evolving network model which exhibits community structure. The network model is based on the inner-community preferential attachment and inter-community preferential attachment mechanisms. The degree distributions of this network model are analysed based on a mean-field method. Theoretical results and numerical simulations indicate that this network model has community structure and scale-free properties

The overlapping community structure of structural brain network in young healthy individuals.

Directory of Open Access Journals (Sweden)

Kai Wu

2011-05-01

Full Text Available Community structure is a universal and significant feature of many complex networks in biology, society, and economics. Community structure has also been revealed in human brain structural and functional networks in previous studies. However, communities overlap and share many edges and nodes. Uncovering the overlapping community structure of complex networks remains largely unknown in human brain networks. Here, using regional gray matter volume, we investigated the structural brain network among 90 brain regions (according to a predefined anatomical atlas in 462 young, healthy individuals. Overlapped nodes between communities were defined by assuming that nodes (brain regions can belong to more than one community. We demonstrated that 90 brain regions were organized into 5 overlapping communities associated with several well-known brain systems, such as the auditory/language, visuospatial, emotion, decision-making, social, control of action, memory/learning, and visual systems. The overlapped nodes were mostly involved in an inferior-posterior pattern and were primarily related to auditory and visual perception. The overlapped nodes were mainly attributed to brain regions with higher node degrees and nodal efficiency and played a pivotal role in the flow of information through the structural brain network. Our results revealed fuzzy boundaries between communities by identifying overlapped nodes and provided new insights into the understanding of the relationship between the structure and function of the human brain. This study provides the first report of the overlapping community structure of the structural network of the human brain.

Afforestation alters community structure of soil fungi.

Science.gov (United States)

Carson, Jennifer K; Gleeson, Deirdre B; Clipson, Nicholas; Murphy, Daniel V

2010-07-01

Relatively little is known about the effect of afforestation on soil fungal communities. This study demonstrated that afforestation altered fungal community structure and that changes were correlated to pools of soil C. Pasture at three locations on the same soil type was afforested with Eucalyptus globulus or Pinus pinaster. The structure of fungal communities under the three land uses was measured after 13y using automated ribosomal intergenic spacer analysis (ARISA). Afforestation significantly altered the structure of fungal communities. The effect of location on the structure of fungal communities was limited to pasture soils; although these contained the same plant species, the relative composition of each species varied between locations. Differences in the structure of fungal communities between pasture, E. globulus and P. pinaster were significantly correlated with changes in the amount of total organic C and microbial biomass-C in soil. Afforestation of patches of agricultural land may contribute to conserving soil fungi in agricultural landscapes by supporting fungal communities with different composition to agricultural soils. Copyright © 2010 The British Mycological Society. Published by Elsevier Ltd. All rights reserved.

Structure of bacterial communities in soil following cover crop and organic fertilizer incorporation.

Science.gov (United States)

Fernandez, Adria L; Sheaffer, Craig C; Wyse, Donald L; Staley, Christopher; Gould, Trevor J; Sadowsky, Michael J

2016-11-01

Incorporation of organic material into soils is an important element of organic farming practices that can affect the composition of the soil bacterial communities that carry out nutrient cycling and other functions crucial to crop health and growth. We conducted a field experiment to determine the effects of cover crops and fertilizers on bacterial community structure in agricultural soils under long-term organic management. Illumina sequencing of 16S rDNA revealed diverse communities comprising 45 bacterial phyla in corn rhizosphere and bulk field soil. Community structure was most affected by location and by the rhizosphere effect, followed by sampling time and amendment treatment. These effects were associated with soil physicochemical properties, including pH, moisture, organic matter, and nutrient levels. Treatment differences were apparent in bulk and rhizosphere soils at the time of peak corn growth in the season following cover crop and fertilizer application. Cover crop and fertilizer treatments tended to lower alpha diversity in early season samples. However, winter rye, oilseed radish, and buckwheat cover crop treatments increased alpha diversity in some later season samples compared to a no-amendment control. Fertilizer treatments and some cover crops decreased relative abundance of members of the ammonia-oxidizing family Nitrosomonadaceae. Pelleted poultry manure and Sustane® (a commercial fertilizer) decreased the relative abundance of Rhizobiales. Our data point to a need for future research exploring how (1) cover crops influence bacterial community structure and functions, (2) these effects differ with biomass composition and quantity, and (3) existing soil conditions and microbial community composition influence how soil microbial populations respond to agricultural management practices.

Epidemic spreading on complex networks with community structures

NARCIS (Netherlands)

Stegehuis, C.; van der Hofstad, R.W.; van Leeuwaarden, J.S.H.

2016-01-01

Many real-world networks display a community structure. We study two random graph models that create a network with similar community structure as a given network. One model preserves the exact community structure of the original network, while the other model only preserves the set of communities

Micro-Food Web Structure Shapes Rhizosphere Microbial Communities and Growth in Oak

Directory of Open Access Journals (Sweden)

Hazel R. Maboreke

2018-03-01

Full Text Available The multitrophic interactions in the rhizosphere impose significant impacts on microbial community structure and function, affecting nutrient mineralisation and consequently plant performance. However, particularly for long-lived plants such as forest trees, the mechanisms by which trophic structure of the micro-food web governs rhizosphere microorganisms are still poorly understood. This study addresses the role of nematodes, as a major component of the soil micro-food web, in influencing the microbial abundance and community structure as well as tree growth. In a greenhouse experiment with Pedunculate Oak seedlings were grown in soil, where the nematode trophic structure was manipulated by altering the proportion of functional groups (i.e., bacterial, fungal, and plant feeders in a full factorial design. The influence on the rhizosphere microbial community, the ectomycorrhizal symbiont Piloderma croceum, and oak growth, was assessed. Soil phospholipid fatty acids were employed to determine changes in the microbial communities. Increased density of singular nematode functional groups showed minor impact by increasing the biomass of single microbial groups (e.g., plant feeders that of Gram-negative bacteria, except fungal feeders, which resulted in a decline of all microorganisms in the soil. In contrast, inoculation of two or three nematode groups promoted microbial biomass and altered the community structure in favour of bacteria, thereby counteracting negative impact of single groups. These findings highlight that the collective action of trophic groups in the soil micro-food web can result in microbial community changes promoting the fitness of the tree, thereby alleviating the negative effects of individual functional groups.

Changes in the Bacterial Community Structure of Remediated Anthracene-Contaminated Soils

Science.gov (United States)

Delgado-Balbuena, Laura; Bello-López, Juan M.; Navarro-Noya, Yendi E.; Rodríguez-Valentín, Analine; Luna-Guido, Marco L.; Dendooven, Luc

2016-01-01

Mixing soil or adding earthworms (Eisenia fetida (Savigny, 1826)) accelerated the removal of anthracene, a polycyclic aromatic hydrocarbon, from a pasture and an arable soil, while a non-ionic surfactant (Surfynol® 485) inhibited the removal of the contaminant compared to the untreated soil. It was unclear if the treatments affected the soil bacterial community and consequently the removal of anthracene. Therefore, the bacterial community structure was monitored by means of 454 pyrosequencing of the 16S rRNA gene in the pasture and arable soil mixed weekly, amended with Surfynol® 485, E. fetida or organic material that served as food for the earthworms for 56 days. In both soils, the removal of anthracene was in the order: mixing soil weekly (100%) > earthworms applied (92%) > organic material applied (77%) > untreated soil (57%) > surfactant applied (34%) after 56 days. There was no clear link between removal of anthracene from soil and changes in the bacterial community structure. On the one hand, application of earthworms removed most of the contaminant from the arable soil and had a strong effect on the bacterial community structure, i.e. a decrease in the relative abundance of the Acidobacteria, Chloroflexi and Gemmatimonadetes, and an increase in that of the Proteobacteria compared to the unamended soil. Mixing the soil weekly removed all anthracene from the arable soil, but had little or no effect on the bacterial community structure. On the other hand, application of the surfactant inhibited the removal of anthracene from the arable soil compared to the untreated soil, but had a strong effect on the bacterial community structure, i.e. a decrease in the relative abundance of Cytophagia (Bacteroidetes), Chloroflexi, Gemmatimonadetes and Planctomycetes and an increase in that of the Flavobacteria (Bacteroidetes) and Proteobacteria. Additionally, the removal of anthracene was similar in the different treatments of both the arable and pasture soil, but the

Changes in the Bacterial Community Structure of Remediated Anthracene-Contaminated Soils.

Directory of Open Access Journals (Sweden)

Laura Delgado-Balbuena

Full Text Available Mixing soil or adding earthworms (Eisenia fetida (Savigny, 1826 accelerated the removal of anthracene, a polycyclic aromatic hydrocarbon, from a pasture and an arable soil, while a non-ionic surfactant (Surfynol® 485 inhibited the removal of the contaminant compared to the untreated soil. It was unclear if the treatments affected the soil bacterial community and consequently the removal of anthracene. Therefore, the bacterial community structure was monitored by means of 454 pyrosequencing of the 16S rRNA gene in the pasture and arable soil mixed weekly, amended with Surfynol® 485, E. fetida or organic material that served as food for the earthworms for 56 days. In both soils, the removal of anthracene was in the order: mixing soil weekly (100% > earthworms applied (92% > organic material applied (77% > untreated soil (57% > surfactant applied (34% after 56 days. There was no clear link between removal of anthracene from soil and changes in the bacterial community structure. On the one hand, application of earthworms removed most of the contaminant from the arable soil and had a strong effect on the bacterial community structure, i.e. a decrease in the relative abundance of the Acidobacteria, Chloroflexi and Gemmatimonadetes, and an increase in that of the Proteobacteria compared to the unamended soil. Mixing the soil weekly removed all anthracene from the arable soil, but had little or no effect on the bacterial community structure. On the other hand, application of the surfactant inhibited the removal of anthracene from the arable soil compared to the untreated soil, but had a strong effect on the bacterial community structure, i.e. a decrease in the relative abundance of Cytophagia (Bacteroidetes, Chloroflexi, Gemmatimonadetes and Planctomycetes and an increase in that of the Flavobacteria (Bacteroidetes and Proteobacteria. Additionally, the removal of anthracene was similar in the different treatments of both the arable and pasture soil

Structural and functional diversity of microbial communities from a lake sediment contaminated with trenbolone, an endocrine-disrupting chemical

International Nuclear Information System (INIS)

Radl, Viviane; Pritsch, Karin; Munch, Jean Charles; Schloter, Michael

2005-01-01

Effects of trenbolone (TBOH), a hormone used in cattle production, on the structure and function of microbial communities in a fresh water sediment from a lake in Southern Germany were studied in a microcosm experiment. The microbial community structure and the total gene pool of the sediment, assessed by 16S rRNA/rDNA and RAPD fingerprint analysis, respectively, were not significantly affected by TBOH. In contrast, the N-acetyl-glucosaminidase activity was almost 50% lower in TBOH treated samples (P<0.05). Also, the substrate utilization potential, measured using the BIOLOG[reg] system, was reduced after TBOH treatment. Interestingly, this potential did not recover at the end of the experiment, i.e. 19 days after the addition of the chemical. Repeated application of TBOH did not lead to an additional reduction in the substrate utilization potential. Overall results indicate that microbial community function was more sensitive to TBOH treatment than the community structure and the total gene pool. - The steroid hormone trenbolone affects microbial community function in a lake sediment

Structural and functional diversity of microbial communities from a lake sediment contaminated with trenbolone, an endocrine-disrupting chemical

Energy Technology Data Exchange (ETDEWEB)

Radl, Viviane [GSF National Research Center for Environment and Health, Institute of Soil Ecology, PO Box 1129, D-85764, Neuherberg (Germany)]. E-mail: barbosa@gsf.de; Pritsch, Karin [GSF National Research Center for Environment and Health, Institute of Soil Ecology, PO Box 1129, D-85764, Neuherberg (Germany); Munch, Jean Charles [GSF National Research Center for Environment and Health, Institute of Soil Ecology, PO Box 1129, D-85764, Neuherberg (Germany); Schloter, Michael [GSF National Research Center for Environment and Health, Institute of Soil Ecology, PO Box 1129, D-85764, Neuherberg (Germany)

2005-09-15

Effects of trenbolone (TBOH), a hormone used in cattle production, on the structure and function of microbial communities in a fresh water sediment from a lake in Southern Germany were studied in a microcosm experiment. The microbial community structure and the total gene pool of the sediment, assessed by 16S rRNA/rDNA and RAPD fingerprint analysis, respectively, were not significantly affected by TBOH. In contrast, the N-acetyl-glucosaminidase activity was almost 50% lower in TBOH treated samples (P<0.05). Also, the substrate utilization potential, measured using the BIOLOG[reg] system, was reduced after TBOH treatment. Interestingly, this potential did not recover at the end of the experiment, i.e. 19 days after the addition of the chemical. Repeated application of TBOH did not lead to an additional reduction in the substrate utilization potential. Overall results indicate that microbial community function was more sensitive to TBOH treatment than the community structure and the total gene pool. - The steroid hormone trenbolone affects microbial community function in a lake sediment.

Marine protected areas increase temporal stability of community structure, but not density or diversity, of tropical seagrass fish communities.

Directory of Open Access Journals (Sweden)

Elisa Alonso Aller

Full Text Available Marine protected areas (MPAs have been shown to increase long-term temporal stability of fish communities and enhance ecosystem resilience to anthropogenic disturbance. Yet, the potential ability of MPAs to buffer effects of environmental variability at shorter time scales remains widely unknown. In the tropics, the yearly monsoon cycle is a major natural force affecting marine organisms in tropical regions, and its timing and severity are predicted to change over the coming century, with potentially severe effects on marine organisms, ecosystems and ecosystem services. Here, we assessed the ability of MPAs to buffer effects of monsoon seasonality on seagrass-associated fish communities, using a field survey in two MPAs (no-take zones and two unprotected (open-access sites around Zanzibar (Tanzania. We assessed the temporal stability of fish density and community structure within and outside MPAs during three monsoon seasons in 2014-2015, and investigated several possible mechanisms that could regulate temporal stability. Our results show that MPAs did not affect fish density and diversity, but that juvenile fish densities were temporally more stable within MPAs. Second, fish community structure was more stable within MPAs for juvenile and adult fish, but not for subadult fish or the total fish community. Third, the observed effects may be due to a combination of direct and indirect (seagrass-mediated effects of seasonality and, potentially, fluctuating fishing pressure outside MPAs. In summary, these MPAs may not have the ability to enhance fish density and diversity and to buffer effects of monsoon seasonality on the whole fish community. However, they may increase the temporal stability of certain groups, such as juvenile fish. Consequently, our results question whether MPAs play a general role in the maintenance of biodiversity and ecosystem functioning under changing environmental conditions in tropical seagrass fish communities.

Structural stability, microbial biomass and community composition of sediments affected by the hydric dynamics of an urban stormwater infiltration basin. Dynamics of physical and microbial characteristics of stormwater sediment.

Science.gov (United States)

Badin, Anne Laure; Monier, Armelle; Volatier, Laurence; Geremia, Roberto A; Delolme, Cécile; Bedell, Jean-Philippe

2011-05-01

The sedimentary layer deposited at the surface of stormwater infiltration basins is highly organic and multicontaminated. It undergoes considerable moisture content fluctuations due to the drying and inundation cycles (called hydric dynamics) of these basins. Little is known about the microflora of the sediments and its dynamics; hence, the purpose of this study is to describe the physicochemical and biological characteristics of the sediments at different hydric statuses of the infiltration basin. Sediments were sampled at five time points following rain events and dry periods. They were characterized by physical (aggregation), chemical (nutrients and heavy metals), and biological (total, bacterial and fungal biomasses, and genotypic fingerprints of total bacterial and fungal communities) parameters. Data were processed using statistical analyses which indicated that heavy metal (1,841 μg/g dry weight (DW)) and organic matter (11%) remained stable through time. By contrast, aggregation, nutrient content (NH₄⁺, 53-717 μg/g DW), pH (6.9-7.4), and biological parameters were shown to vary with sediment water content and sediment biomass, and were higher consecutive to stormwater flows into the basin (up to 7 mg C/g DW) than during dry periods (0.6 mg C/g DW). Coinertia analysis revealed that the structure of the bacterial communities is driven by the hydric dynamics of the infiltration basin, although no such trend was found for fungal communities. Hydric dynamics more than rain events appear to be more relevant for explaining variations of aggregation, microbial biomass, and shift in the microbial community composition. We concluded that the hydric dynamics of stormwater infiltration basins greatly affects the structural stability of the sedimentary layer, the biomass of the microbial community living in it and its dynamics. The decrease in aggregation consecutive to rewetting probably enhances access to organic matter (OM), explaining the consecutive release

Imidacloprid seed treatments affect individual ant behavior and community structure but not egg predation, pest abundance or soybean yield.

Science.gov (United States)

Penn, Hannah J; Dale, Andrew M

2017-08-01

Neonicotinoid seed treatments are under scrutiny because of their variable efficacy against crop pests and for their potential negative impacts on non-target organisms. Ants provide important biocontrol services in agroecosystems and can be indicators of ecosystem health. This study tested for effects of exposure to imidacloprid plus fungicide or fungicide-treated seeds on individual ant survival, locomotion and foraging capabilities and on field ant community structure, pest abundance, ant predation and yield. Cohorts of ants exposed to either type of treated seed had impaired locomotion and a higher incidence of morbidity and mortality but no loss of foraging capacity. In the field, we saw no difference in ant species richness, regardless of seed treatment. Blocks with imidacloprid did have higher species evenness and diversity, probably owing to variable effects of the insecticide on different ant species, particularly Tetramorium caespitum. Ant predation on sentinel eggs, pest abundance and soybean growth and yield were similar in the two treatments. Both seed treatments had lethal and sublethal effects on ant individuals, and the influence of imidacloprid seed coating in the field was manifested in altered ant community composition. Those effects, however, were not strong enough to affect egg predation, pest abundance or soybean yield in field blocks. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Changes in Microbial Community Structure and Soil Biological Properties in Mined Dune Areas During Re-vegetation.

Science.gov (United States)

Escobar, Indra Elena C; Santos, Vilma M; da Silva, Danielle Karla A; Fernandes, Marcelo F; Cavalcante, Uided Maaze T; Maia, Leonor C

2015-06-01

The aim of this study was to describe the impact of re-vegetation on the restoration of microbial community structure and soil microbiological properties in sand dunes that had been affected by mining activity. Soil samples were collected during the dry and rainy seasons from a chronosequence (1, 9, 21 years) of re-vegetated dunes using a single preserved dune as a reference. The composition of the fatty acid methyl esters and soil microbial properties were evaluated. The results showed that the changes in microbial community structure were related to seasonal variations: biomarkers of Gram-positive bacteria were higher than Gram-negative bacteria during the dry season, showing that this group of organisms is more tolerant to these stressful conditions. The microbial community structure in the natural dune was less affected by seasonal variation compared to the re-vegetated areas, whereas the opposite was observed for microbiological properties. Thus, in general, the proportion of saprobic fungi was higher in the natural dune, whereas Gram-negative bacteria were proportionally more common in the younger areas. Although over time the re-vegetation allows the recovery of the microbial community and the soil functions, these communities and functions are different from those found in the undisturbed areas.

Intraspecific phytochemical variation shapes community and population structure for specialist caterpillars.

Science.gov (United States)

Glassmire, Andrea E; Jeffrey, Christopher S; Forister, Matthew L; Parchman, Thomas L; Nice, Chris C; Jahner, Joshua P; Wilson, Joseph S; Walla, Thomas R; Richards, Lora A; Smilanich, Angela M; Leonard, Michael D; Morrison, Colin R; Simbaña, Wilmer; Salagaje, Luis A; Dodson, Craig D; Miller, Jim S; Tepe, Eric J; Villamarin-Cortez, Santiago; Dyer, Lee A

2016-10-01

Chemically mediated plant-herbivore interactions contribute to the diversity of terrestrial communities and the diversification of plants and insects. While our understanding of the processes affecting community structure and evolutionary diversification has grown, few studies have investigated how trait variation shapes genetic and species diversity simultaneously in a tropical ecosystem. We investigated secondary metabolite variation among subpopulations of a single plant species, Piper kelleyi (Piperaceae), using high-performance liquid chromatography (HPLC), to understand associations between plant phytochemistry and host-specialized caterpillars in the genus Eois (Geometridae: Larentiinae) and associated parasitoid wasps and flies. In addition, we used a genotyping-by-sequencing approach to examine the genetic structure of one abundant caterpillar species, Eois encina, in relation to host phytochemical variation. We found substantive concentration differences among three major secondary metabolites, and these differences in chemistry predicted caterpillar and parasitoid community structure among host plant populations. Furthermore, E. encina populations located at high elevations were genetically different from other populations. They fed on plants containing high concentrations of prenylated benzoic acid. Thus, phytochemistry potentially shapes caterpillar and wasp community composition and geographic variation in species interactions, both of which can contribute to diversification of plants and insects. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Vegetative Propagule Pressure and Water Depth Affect Biomass and Evenness of Submerged Macrophyte Communities.

Directory of Open Access Journals (Sweden)

Hong-Li Li

Full Text Available Vegetative propagule pressure may affect the establishment and structure of aquatic plant communities that are commonly dominated by plants capable of clonal growth. We experimentally constructed aquatic communities consisting of four submerged macrophytes (Hydrilla verticillata, Ceratophyllum demersum, Elodea nuttallii and Myriophyllum spicatum with three levels of vegetative propagule pressure (4, 8 and 16 shoot fragments for communities in each pot and two levels of water depth (30 cm and 70 cm. Increasing vegetative propagule pressure and decreasing water level significantly increased the growth of the submerged macrophyte communities, suggesting that propagule pressure and water depth should be considered when utilizing vegetative propagules to re-establish submerged macrophyte communities in degraded aquatic ecosystems. However, increasing vegetative propagule pressure and decreasing water level significantly decreased evenness of the submerged macrophyte communities because they markedly increased the dominance of H. verticillata and E. nuttallii, but had little impact on that of C. demersum and M. spicatum. Thus, effects of vegetative propagule pressure and water depth are species-specific and increasing vegetative propagule pressure under lower water level can facilitate the establishment success of submerged macrophyte communities.

Does a decade of elevated [CO2] affect a desert perennial plant community?

Science.gov (United States)

Newingham, Beth A; Vanier, Cheryl H; Kelly, Lauren J; Charlet, Therese N; Smith, Stanley D

2014-01-01

Understanding the effects of elevated [CO2 ] on plant community structure is crucial to predicting ecosystem responses to global change. Early predictions suggested that productivity in deserts would increase via enhanced water-use efficiency under elevated [CO2], but the response of intact arid plant communities to elevated [CO2 ] is largely unknown. We measured changes in perennial plant community characteristics (cover, species richness and diversity) after 10 yr of elevated [CO2] exposure in an intact Mojave Desert community at the Nevada Desert Free-Air CO2 Enrichment (FACE) Facility. Contrary to expectations, total cover, species richness, and diversity were not affected by elevated [CO2]. Over the course of the experiment, elevated [CO2] had no effect on changes in cover of the evergreen C3 shrub, Larrea tridentata; alleviated decreases in cover of the C4 bunchgrass, Pleuraphis rigida; and slightly reduced the cover of C3 drought-deciduous shrubs. Thus, we generally found no effect of elevated [CO2] on plant communities in this arid ecosystem. Extended drought, slow plant growth rates, and highly episodic germination and recruitment of new individuals explain the lack of strong perennial plant community shifts after a decade of elevated [CO2]. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Forest Management Intensity Affects Aquatic Communities in Artificial Tree Holes.

Science.gov (United States)

Petermann, Jana S; Rohland, Anja; Sichardt, Nora; Lade, Peggy; Guidetti, Brenda; Weisser, Wolfgang W; Gossner, Martin M

2016-01-01

Forest management could potentially affect organisms in all forest habitats. However, aquatic communities in water-filled tree-holes may be especially sensitive because of small population sizes, the risk of drought and potential dispersal limitation. We set up artificial tree holes in forest stands subject to different management intensities in two regions in Germany and assessed the influence of local environmental properties (tree-hole opening type, tree diameter, water volume and water temperature) as well as regional drivers (forest management intensity, tree-hole density) on tree-hole insect communities (not considering other organisms such as nematodes or rotifers), detritus content, oxygen and nutrient concentrations. In addition, we compared data from artificial tree holes with data from natural tree holes in the same area to evaluate the methodological approach of using tree-hole analogues. We found that forest management had strong effects on communities in artificial tree holes in both regions and across the season. Abundance and species richness declined, community composition shifted and detritus content declined with increasing forest management intensity. Environmental variables, such as tree-hole density and tree diameter partly explained these changes. However, dispersal limitation, indicated by effects of tree-hole density, generally showed rather weak impacts on communities. Artificial tree holes had higher water temperatures (on average 2°C higher) and oxygen concentrations (on average 25% higher) than natural tree holes. The abundance of organisms was higher but species richness was lower in artificial tree holes. Community composition differed between artificial and natural tree holes. Negative management effects were detectable in both tree-hole systems, despite their abiotic and biotic differences. Our results indicate that forest management has substantial and pervasive effects on tree-hole communities and may alter their structure and

Host tree phenology affects vascular epiphytes at the physiological, demographic and community level

Science.gov (United States)

Einzmann, Helena J. R.; Beyschlag, Joachim; Hofhansl, Florian; Wanek, Wolfgang; Zotz, Gerhard

2015-01-01

The processes that govern diverse tropical plant communities have rarely been studied in life forms other than trees. Structurally dependent vascular epiphytes, a major part of tropical biodiversity, grow in a three-dimensional matrix defined by their hosts, but trees differ in their architecture, bark structure/chemistry and leaf phenology. We hypothesized that the resulting seasonal differences in microclimatic conditions in evergreen vs. deciduous trees would affect epiphytes at different levels, from organ physiology to community structure. We studied the influence of tree leaf phenology on vascular epiphytes on the Island of Barro Colorado, Panama. Five tree species were selected, which were deciduous, semi-deciduous or evergreen. The crowns of drought-deciduous trees, characterized by sunnier and drier microclimates, hosted fewer individuals and less diverse epiphyte assemblages. Differences were also observed at a functional level, e.g. epiphyte assemblages in deciduous trees had larger proportions of Crassulacean acid metabolism species and individuals. At the population level a drier microclimate was associated with lower individual growth and survival in a xerophytic fern. Some species also showed, as expected, lower specific leaf area and higher δ13C values when growing in deciduous trees compared with evergreen trees. As hypothesized, host tree leaf phenology influences vascular epiphytes at different levels. Our results suggest a cascading effect of tree composition and associated differences in tree phenology on the diversity and functioning of epiphyte communities in tropical lowland forests. PMID:25392188

Soil aggregation and bacterial community structure as affected by tillage and cover cropping in the Brazilian Cerrados

NARCIS (Netherlands)

Peixoto, R. S.; Coutinho, H. L. C.; Madari, B.; Machado, P. L. O. A.; Rumjanek, N. G.; Van Elsas, J. D.; Seldin, L.; Rosado, A. S.

2006-01-01

Microbial-based indicators of soil quality are believed to be more dynamic than those based on physical and chemical properties. Recent developments in molecular biology based techniques have led to rapid and reliable tools to characterize microbial community structures. We determined the effects of

Responses of redwood soil microbial community structure and N transformations to climate change

Science.gov (United States)

Damon C. Bradbury; Mary K. Firestone

2012-01-01

Soil microorganisms perform critical ecosystem functions, including decomposition, nitrogen (N) mineralization and nitrification. Soil temperature and water availability can be critical determinants of the rates of these processes as well as microbial community composition and structure. This research examined how changes in climate affect bacterial and fungal...

Research on Community Structure in Bus Transport Networks

International Nuclear Information System (INIS)

Yang Xuhua; Wang Bo; Sun Youxian

2009-01-01

We abstract the bus transport networks (BTNs) to two kinds of complex networks with space L and space P methods respectively. Using improved community detecting algorithm (PKM agglomerative algorithm), we analyze the community property of two kinds of BTNs graphs. The results show that the BTNs graph described with space L method have obvious community property, but the other kind of BTNs graph described with space P method have not. The reason is that the BTNs graph described with space P method have the intense overlapping community property and general community division algorithms can not identify this kind of community structure. To overcome this problem, we propose a novel community structure called N-depth community and present a corresponding community detecting algorithm, which can detect overlapping community. Applying the novel community structure and detecting algorithm to a BTN evolution model described with space P, whose network property agrees well with real BTNs', we get obvious community property. (general)

Characterizing changes in soil bacterial community structure in response to short-term warming

Energy Technology Data Exchange (ETDEWEB)

Xiong, Jinbo [State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing China; School of Marine Sciences, Ningbo University, Ningbo China; Sun, Huaibo [State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing China; Peng, Fei [Key Laboratory of Desert and Desertification, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou China; Zhang, Huayong [State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing China; Xue, Xian [Key Laboratory of Desert and Desertification, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou China; Gibbons, Sean M. [Argonne National Laboratory Biosciences Division, Argonne IL USA; Graduate Program in Biophysical Sciences, University of Chicago, Chicago IL USA; Gilbert, Jack A. [Argonne National Laboratory Biosciences Division, Argonne IL USA; Department of Ecology and Evolution, University of Chicago, Chicago IL USA; Chu, Haiyan [State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing China

2014-02-18

High altitude alpine meadows are experiencing considerably greater than average increases in soil surface temperature, potentially as a result of ongoing climate change. The effects of warming on plant productivity and soil edaphic variables have been established previously, but the influence of warming on soil microbial community structure has not been well characterized. Here, the impact of 15 months of soil warming (both + 1 and + 2 degrees C) on bacterial community structure was examined in a field experiment on a Tibetan plateau alpine meadow using bar-coded pyrosequencing. Warming significantly changed (P < 0.05) the structure of the soil bacterial community, but the alpha diversity was not dramatically affected. Changes in the abundance of the Actinobacteria and Alphaproteobacteria were found to contribute the most to differences between ambient (AT) and artificially warmed conditions. A variance partitioning analysis (VPA) showed that warming directly explained 7.15% variation in bacterial community structure, while warming-induced changes in soil edaphic and plant phenotypic properties indirectly accounted for 28.3% and 20.6% of the community variance, respectively. Interestingly, certain taxa showed an inconsistent response to the two warming treatments, for example Deltaproteobacteria showed a decreased relative abundance at + 1 degrees C, but a return to AT control relative abundance at + 2 degrees C. This suggests complex microbial dynamics that could result from conditional dependencies between bacterial taxa.

Epidemics in adaptive networks with community structure

Science.gov (United States)

Shaw, Leah; Tunc, Ilker

2010-03-01

Models for epidemic spread on static social networks do not account for changes in individuals' social interactions. Recent studies of adaptive networks have modeled avoidance behavior, as non-infected individuals try to avoid contact with infectives. Such models have not generally included realistic social structure. Here we study epidemic spread on an adaptive network with community structure. We model the effect of heterogeneous communities on infection levels and epidemic extinction. We also show how an epidemic can alter the community structure.

Bacterial community structure in experimental methanogenic bioreactors and search for pathogenic clostridia as community members.

Science.gov (United States)

Dohrmann, Anja B; Baumert, Susann; Klingebiel, Lars; Weiland, Peter; Tebbe, Christoph C

2011-03-01

Microbial conversion of organic waste or harvested plant material into biogas has become an attractive technology for energy production. Biogas is produced in reactors under anaerobic conditions by a consortium of microorganisms which commonly include bacteria of the genus Clostridium. Since the genus Clostridium also harbors some highly pathogenic members in its phylogenetic cluster I, there has been some concern that an unintended growth of such pathogens might occur during the fermentation process. Therefore this study aimed to follow how process parameters affect the diversity of Bacteria in general, and the diversity of Clostridium cluster I members in particular. The development of both communities was followed in model biogas reactors from start-up during stable methanogenic conditions. The biogas reactors were run with either cattle or pig manures as substrates, and both were operated at mesophilic and thermophilic conditions. The structural diversity was analyzed independent of cultivation using a PCR-based detection of 16S rRNA genes and genetic profiling by single-strand conformation polymorphism (SSCP). Genetic profiles indicated that both bacterial and clostridial communities evolved in parallel, and the community structures were highly influenced by both substrate and temperature. Sequence analysis of 16S rRNA genes recovered from prominent bands from SSCP profiles representing Clostridia detected no pathogenic species. Thus, this study gave no indication that pathogenic clostridia would be enriched as dominant community members in biogas reactors fed with manure.

Spatial Patterns of Species Diversity and Phylogenetic Structure of Plant Communities in the Tianshan Mountains, Arid Central Asia

Directory of Open Access Journals (Sweden)

Hong-Xiang Zhang

2017-12-01

Full Text Available The Tianshan Mountains, located in arid Central Asia, have a humid climate and are biodiversity hotspots. Here, we aimed to clarify whether the pattern of species diversity and the phylogenetic structure of plant communities is affected by environmental variables and glacial refugia. In this study, plant community assemblies of 17 research sites with a total of 35 sample plots were investigated at the grassland/woodland boundaries on the Tianshan Mountains. Community phylogeny of these plant communities was constructed based on two plant DNA barcode regions. The indices of phylogenetic diversity and phylogenetic community structure were calculated for these sample plots. We first estimated the correlation coefficients between species richness (SR and environmental variables as well as the presence of glacial refugia. We then mapped the significant values of indices of community phylogeny (PD, RPD, NRI, and NTI to investigate the correlation between community phylogeny and environmental structure or macrozones in the study area. The results showed that a significantly higher value of SR was obtained for the refugial groups than for the colonizing groups (P < 0.05; presence of refugia and environmental variables were highly correlated to the pattern of variation in SR. Indices of community phylogeny were not significantly different between refugial and colonizing regions. Comparison with the humid western part showed that plant communities in the arid eastern part of the Tianshan Mountains tended to display more significant phylogenetic overdispersion. The variation tendency of the PhyloSor index showed that the increase in macro-geographical and environmental distance did not influence obvious phylogenetic dissimilarities between different sample plots. In conclusion, glacial refugia and environmental factors profoundly influenced the pattern of SR, but community phylogenetic structure was not affected by glacial refugia among different plant

Impact of Oil on Bacterial Community Structure in Bioturbated Sediments

Science.gov (United States)

Stauffert, Magalie; Cravo-Laureau, Cristiana; Jézéquel, Ronan; Barantal, Sandra; Cuny, Philippe; Gilbert, Franck; Cagnon, Christine; Militon, Cécile; Amouroux, David; Mahdaoui, Fatima; Bouyssiere, Brice; Stora, Georges; Merlin, François-Xavier; Duran, Robert

2013-01-01

Oil spills threaten coastlines where biological processes supply essential ecosystem services. Therefore, it is crucial to understand how oil influences the microbial communities in sediments that play key roles in ecosystem functioning. Ecosystems such as sediments are characterized by intensive bioturbation due to burrowing macrofauna that may modify the microbial metabolisms. It is thus essential to consider the bioturbation when determining the impact of oil on microbial communities. In this study, an experimental laboratory device maintaining pristine collected mudflat sediments in microcosms closer to true environmental conditions – with tidal cycles and natural seawater – was used to simulate an oil spill under bioturbation conditions. Different conditions were applied to the microcosms including an addition of: standardized oil (Blend Arabian Light crude oil, 25.6 mg.g−1 wet sediment), the common burrowing organism Hediste (Nereis) diversicolor and both the oil and H. diversicolor. The addition of H. diversicolor and its associated bioturbation did not affect the removal of petroleum hydrocarbons. After 270 days, 60% of hydrocarbons had been removed in all microcosms irrespective of the H. diversicolor addition. However, 16S-rRNA gene and 16S-cDNA T-RFLP and RT-PCR-amplicon libraries analysis showed an effect of the condition on the bacterial community structure, composition, and dynamics, supported by PerMANOVA analysis. The 16S-cDNA libraries from microcosms where H. diversicolor was added (oiled and un-oiled) showed a marked dominance of sequences related to Gammaproteobacteria. However, in the oiled-library sequences associated to Deltaproteobacteria and Bacteroidetes were also highly represented. The 16S-cDNA libraries from oiled-microcosms (with and without H. diversicolor addition) revealed two distinct microbial communities characterized by different phylotypes associated to known hydrocarbonoclastic bacteria and dominated by

Impact of oil on bacterial community structure in bioturbated sediments.

Directory of Open Access Journals (Sweden)

Magalie Stauffert

Full Text Available Oil spills threaten coastlines where biological processes supply essential ecosystem services. Therefore, it is crucial to understand how oil influences the microbial communities in sediments that play key roles in ecosystem functioning. Ecosystems such as sediments are characterized by intensive bioturbation due to burrowing macrofauna that may modify the microbial metabolisms. It is thus essential to consider the bioturbation when determining the impact of oil on microbial communities. In this study, an experimental laboratory device maintaining pristine collected mudflat sediments in microcosms closer to true environmental conditions--with tidal cycles and natural seawater--was used to simulate an oil spill under bioturbation conditions. Different conditions were applied to the microcosms including an addition of: standardized oil (Blend Arabian Light crude oil, 25.6 mg.g⁻¹ wet sediment, the common burrowing organism Hediste (Nereis diversicolor and both the oil and H. diversicolor. The addition of H. diversicolor and its associated bioturbation did not affect the removal of petroleum hydrocarbons. After 270 days, 60% of hydrocarbons had been removed in all microcosms irrespective of the H. diversicolor addition. However, 16S-rRNA gene and 16S-cDNA T-RFLP and RT-PCR-amplicon libraries analysis showed an effect of the condition on the bacterial community structure, composition, and dynamics, supported by PerMANOVA analysis. The 16S-cDNA libraries from microcosms where H. diversicolor was added (oiled and un-oiled showed a marked dominance of sequences related to Gammaproteobacteria. However, in the oiled-library sequences associated to Deltaproteobacteria and Bacteroidetes were also highly represented. The 16S-cDNA libraries from oiled-microcosms (with and without H. diversicolor addition revealed two distinct microbial communities characterized by different phylotypes associated to known hydrocarbonoclastic bacteria and dominated by

Finding Community Structures In Social Activity Data

KAUST Repository

Peng, Chengbin

2015-01-01

Social activity data sets are increasing in number and volume. Finding community structure in such data is valuable in many applications. For example, understand- ing the community structure of social networks may reduce the spread of epidemics

Degradation of oxytetracycline and its impacts on biogas-producing microbial community structure.

Science.gov (United States)

Coban, Halil; Ertekin, Emine; Ince, Orhan; Turker, Gokhan; Akyol, Çağrı; Ince, Bahar

2016-07-01

The effect of veterinary antibiotics in anaerobic digesters is a concern where methane production efficiency is highly dependent on microbial community structure. In this study, both anaerobic degradation of a common veterinary antibiotic, oxytetracycline (OTC), and its effects on an anaerobic digester microbial community were investigated. Qualitative and quantitative molecular tools were used to monitor changes in microbial community structure during a 60-day batch incubation period of cow manure with the addition of different concentrations of the antibiotic. Molecular data were interpreted by a further redundancy analysis as a multivariate statistics approach. At the end of the experiment, approximately 48, 33, and 17 % of the initially added 50, 100, and 200 mg l(-1) of OTC was still present in the serum bottles which reduced the biogas production via accumulation of some of the volatile fatty acids (VFAs). Biogas production was highly correlated with Methanobacteriales and Methanosarcinales gene copy numbers, and those parameters were negatively affected with oxytetracycline and VFA concentrations.

In situ effects of titanium dioxide nanoparticles on community structure of freshwater benthic macroinvertebrates.

Science.gov (United States)

Jovanović, Boris; Milošević, Djuradj; Piperac, Milica Stojković; Savić, Ana

2016-06-01

For the first time in the current literature, the effect of titanium dioxide (TiO2) nanoparticles on the community structure of macroinvertebrates has been investigated in situ. Macroinvertebrates were exposed for 100 days to an environmentally relevant concentration of TiO2 nanoparticles, 25 mg kg(-1) in sediment. Czekanowski's index was 0.61, meaning 39% of the macroinvertebrate community structure was affected by the TiO2 treatment. Non-metric multidimensional scaling (NMDS) visualized the qualitative and quantitative variability of macroinvertebrates at the community level among all samples. A distance-based permutational multivariate analysis of variance (PERMANOVA) revealed the significant effect of TiO2 on the macroinvertebrate community structure. The indicator value analysis showed that the relative frequency and abundance of Planorbarius corneus and Radix labiata were significantly lower in the TiO2 treatment than in the control. Meanwhile, Ceratopogonidae, showed a significantly higher relative frequency and abundance in the TiO2 treatment than in the control. Copyright © 2016 Elsevier Ltd. All rights reserved.

Different continuous cropping spans significantly affect microbial community membership and structure in a vanilla-grown soil as revealed by deep pyrosequencing.

Science.gov (United States)

Xiong, Wu; Zhao, Qingyun; Zhao, Jun; Xun, Weibing; Li, Rong; Zhang, Ruifu; Wu, Huasong; Shen, Qirong

2015-07-01

In the present study, soil bacterial and fungal communities across vanilla continuous cropping time-series fields were assessed through deep pyrosequencing of 16S ribosomal RNA (rRNA) genes and internal transcribed spacer (ITS) regions. The results demonstrated that the long-term monoculture of vanilla significantly altered soil microbial communities. Soil fungal diversity index increased with consecutive cropping years, whereas soil bacterial diversity was relatively stable. Bray-Curtis dissimilarity cluster and UniFrac-weighted principal coordinate analysis (PCoA) revealed that monoculture time was the major determinant for fungal community structure, but not for bacterial community structure. The relative abundances (RAs) of the Firmicutes, Actinobacteria, Bacteroidetes, and Basidiomycota phyla were depleted along the years of vanilla monoculture. Pearson correlations at the phyla level demonstrated that Actinobacteria, Armatimonadetes, Bacteroidetes, Verrucomicrobia, and Firmicutes had significant negative correlations with vanilla disease index (DI), while no significant correlation for fungal phyla was observed. In addition, the amount of the pathogen Fusarium oxysporum accumulated with increasing years and was significantly positively correlated with vanilla DI. By contrast, the abundance of beneficial bacteria, including Bradyrhizobium and Bacillus, significantly decreased over time. In sum, soil weakness and vanilla stem wilt disease after long-term continuous cropping can be attributed to the alteration of the soil microbial community membership and structure, i.e., the reduction of the beneficial microbes and the accumulation of the fungal pathogen.

Similarity between community structures of different online social networks and its impact on underlying community detection

Science.gov (United States)

Fan, W.; Yeung, K. H.

2015-03-01

As social networking services are popular, many people may register in more than one online social network. In this paper we study a set of users who have accounts of three online social networks: namely Foursquare, Facebook and Twitter. Community structure of this set of users may be reflected in these three online social networks. Therefore, high correlation between these reflections and the underlying community structure may be observed. In this work, community structures are detected in all three online social networks. Also, we investigate the similarity level of community structures across different networks. It is found that they show strong correlation with each other. The similarity between different networks may be helpful to find a community structure close to the underlying one. To verify this, we propose a method to increase the weights of some connections in networks. With this method, new networks are generated to assist community detection. By doing this, value of modularity can be improved and the new community structure match network's natural structure better. In this paper we also show that the detected community structures of online social networks are correlated with users' locations which are identified on Foursquare. This information may also be useful for underlying community detection.

Community Structure of Ammonia-Oxidizing Archaea and Ammonia-Oxidizing Bacteria in Soil Treated with the Insecticide Imidacloprid

Directory of Open Access Journals (Sweden)

Mariusz Cycoń

2015-01-01

Full Text Available The purpose of this experiment was to assess the effect of imidacloprid on the community structure of ammonia-oxidizing archaea (AOA and ammonia-oxidizing bacteria (AOB in soil using the denaturing gradient gel electrophoresis (DGGE approach. Analysis showed that AOA and AOB community members were affected by the insecticide treatment. However, the calculation of the richness (S and the Shannon-Wiener index (H values for soil treated with the field rate (FR dosage of imidacloprid (1 mg/kg soil showed no changes in measured indices for the AOA and AOB community members. In turn, the 10*FR dosage of insecticide (10 mg/kg soil negatively affected the AOA community, which was confirmed by the decrease of the S and H values in comparison with the values obtained for the control soil. In the case of AOB community, an initial decline followed by the increase of the S and H values was obtained. Imidacloprid decreased the nitrification rate while the ammonification process was stimulated by the addition of imidacloprid. Changes in the community structure of AOA and AOB could be due to an increase in the concentration of N-NH4+, known as the most important factor which determines the contribution of these microorganisms to soil nitrification.

Enhancing community detection by using local structural information

International Nuclear Information System (INIS)

Xiang, Ju; Bao, Mei-Hua; Tang, Liang; Li, Jian-Ming; Hu, Ke; Chen, Benyan; Hu, Jing-Bo; Zhang, Yan; Tang, Yan-Ni; Gao, Yuan-Yuan

2016-01-01

Many real-world networks, such as gene networks, protein–protein interaction networks and metabolic networks, exhibit community structures, meaning the existence of groups of densely connected vertices in the networks. Many local similarity measures in the networks are closely related to the concept of the community structures, and may have a positive effect on community detection in the networks. Here, various local similarity measures are used to extract local structural information, which is then applied to community detection in the networks by using the edge-reweighting strategy. The effect of the local similarity measures on community detection is carefully investigated and compared in various networks. The experimental results show that the local similarity measures are crucial for the improvement of community detection methods, while the positive effect of the local similarity measures is closely related to the networks under study and applied community detection methods. (paper: interdisciplinary statistical mechanics)

Temporal and spatial influences incur reconfiguration of Arctic heathland soil bacterial community structure.

Science.gov (United States)

Hill, Richard; Saetnan, Eli R; Scullion, John; Gwynn-Jones, Dylan; Ostle, Nick; Edwards, Arwyn

2016-06-01

Microbial responses to Arctic climate change could radically alter the stability of major stores of soil carbon. However, the sensitivity of plot-scale experiments simulating climate change effects on Arctic heathland soils to potential confounding effects of spatial and temporal changes in soil microbial communities is unknown. Here, the variation in heathland soil bacterial communities at two survey sites in Sweden between spring and summer 2013 and at scales between 0-1 m and, 1-100 m and between sites (> 100 m) were investigated in parallel using 16S rRNA gene T-RFLP and amplicon sequencing. T-RFLP did not reveal spatial structuring of communities at scales structuring effects may not confound comparison between plot-scale treatments, temporal change is a significant influence. Moreover, the prominence of two temporally exclusive keystone taxa suggests that the stability of Arctic heathland soil bacterial communities could be disproportionally influenced by seasonal perturbations affecting individual taxa. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

Membrane biofouling characterization: effects of sample preparation procedures on biofilm structure and the microbial community

KAUST Repository

Xue, Zheng

2014-07-15

Ensuring the quality and reproducibility of results from biofilm structure and microbial community analysis is essential to membrane biofouling studies. This study evaluated the impacts of three sample preparation factors (ie number of buffer rinses, storage time at 4°C, and DNA extraction method) on the downstream analysis of nitrifying biofilms grown on ultrafiltration membranes. Both rinse and storage affected biofilm structure, as suggested by their strong correlation with total biovolume, biofilm thickness, roughness and the spatial distribution of EPS. Significant variations in DNA yields and microbial community diversity were also observed among samples treated by different rinses, storage and DNA extraction methods. For the tested biofilms, two rinses, no storage and DNA extraction with both mechanical and chemical cell lysis from attached biofilm were the optimal sample preparation procedures for obtaining accurate information about biofilm structure, EPS distribution and the microbial community. © 2014 © 2014 Taylor & Francis.

Factors Affecting Community Participation in O and OD Planning ...

African Journals Online (AJOL)

Factors Affecting Community Participation in O and OD Planning and ... great success at start but later dropped in number of cattle taken for dipping. ... and to establish the measures taken by the district leadership in addressing the problems.

Genetics-based interactions among plants, pathogens, and herbivores define arthropod community structure.

Science.gov (United States)

Busby, Posy E; Lamit, Louis J; Keith, Arthur R; Newcombe, George; Gehring, Catherine A; Whitham, Thomas G; Dirzo, Rodolfo

2015-07-01

Plant resistance to pathogens or insect herbivores is common, but its potential for indirectly influencing plant-associated communities is poorly known. Here, we test whether pathogens' indirect effects on arthropod communities and herbivory depend on plant resistance to pathogens and/or herbivores, and address the overarching interacting foundation species hypothesis that genetics-based interactions among a few highly interactive species can structure a much larger community. In a manipulative field experiment using replicated genotypes of two Populus species and their interspecific hybrids, we found that genetic variation in plant resistance to both pathogens and insect herbivores modulated the strength of pathogens' indirect effects on arthropod communities and insect herbivory. First, due in part to the pathogens' differential impacts on leaf biomass among the two Populus species and the hybrids, the pathogen most strongly impacted arthropod community composition, richness, and abundance on the pathogen-susceptible tree species. Second, we found similar patterns comparing pathogen-susceptible and pathogen-resistant genotypes within species. Third, within a plant species, pathogens caused a fivefold greater reduction in herbivory on insect-herbivore-susceptible plant genotypes than on herbivore-resistant genotypes, demonstrating that the pathogen-herbivore interaction is genotype dependent. We conclude that interactions among plants, pathogens, and herbivores can structure multitrophic communities, supporting the interacting foundation species hypothesis. Because these interactions are genetically based, evolutionary changes in genetic resistance could result in ecological changes in associated communities, which may in turn feed back to affect plant fitness.

Potato cultivar type affects the structure of ammonia oxidizer communities in field soil under potato beyond the rhizosphere

NARCIS (Netherlands)

Cavalcante Franco Dias, A.; Hoogwout, E.F.; de Cassia Pereira e Silva, M.; Falcão Salles, J.; van Overbeek, L.S.; van Elsas, J.D.

The effects of plants on the microbiota involved in the oxidation of ammonia in soils have been controversial. Here, we investigated the dynamics in the abundances and community structures of the bacterial and archaeal ammonia oxidizers (AOB and AOA, respectively) in two fields that were cropped

Effects of Didymosphenia geminata massive growth on stream communities: Smaller organisms and simplified food web structure.

Science.gov (United States)

Ladrera, Rubén; Gomà, Joan; Prat, Narcís

2018-01-01

This study aims to contribute to the understanding of the impact of Didymosphenia geminata massive growths upon river ecosystem communities' composition and functioning. This is the first study to jointly consider the taxonomic composition and functional structure of diatom and macroinvertebrate assemblages in order to determine changes in community structure, and the food web alterations associated with this invasive alga. This study was carried out in the Lumbreras River (Ebro Basin, La Rioja, Northern Spain), which has been affected by a considerable massive growth of D. geminata since 2011. The study shows a profound alteration in both the river community composition and in the food web structure at the sites affected by the massive growth, which is primarily due to the alteration of the environmental conditions, thus demonstrating that D. geminata has an important role as an ecosystem engineer in the river. Thick filamentous mats impede the movement of large invertebrates-especially those that move and feed up on it-and favor small, opportunistic, herbivorous organisms, mainly chironomids, that are capable of moving between filaments and are aided by the absence of large trophic competitors and predators -prey release effect-. Only small predators, such as hydra, are capable of surviving in the new environment, as they are favored by the increase in chironomids, a source of food, and by the reduction in both their own predators and other midge predators -mesopredator release-. This change in the top-down control affects the diatom community, since chironomids may feed on large diatoms, increasing the proportion of small diatoms in the substrate. The survival of small and fast-growing pioneer diatoms is also favored by the mesh of filaments, which offers them a new habitat for colonization. Simultaneously, D. geminata causes a significant reduction in the number of diatoms with similar ecological requirements (those attached to the substrate). Overall, D

Mass media influence spreading in social networks with community structure

Science.gov (United States)

Candia, Julián; Mazzitello, Karina I.

2008-07-01

We study an extension of Axelrod's model for social influence, in which cultural drift is represented as random perturbations, while mass media are introduced by means of an external field. In this scenario, we investigate how the modular structure of social networks affects the propagation of mass media messages across a society. The community structure of social networks is represented by coupled random networks, in which two random graphs are connected by intercommunity links. Considering inhomogeneous mass media fields, we study the conditions for successful message spreading and find a novel phase diagram in the multidimensional parameter space. These findings show that social modularity effects are of paramount importance for designing successful, cost-effective advertising campaigns.

Habitat and landscape characteristics underlying anuran community structure along an urban-rural gradient.

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Pillsbury, Finn C; Miller, James R

2008-07-01

Urbanization has been cited as an important factor in worldwide amphibian declines, and although recent work has illustrated the important influence of broad-scale ecological patterns and processes on amphibian populations, little is known about the factors structuring amphibian communities in urban landscapes. We therefore examined amphibian community responses to wetland habitat availability and landscape characteristics along an urban-rural gradient in central Iowa, USA, a region experiencing rapid suburban growth. We conducted call surveys at 61 wetlands to estimate anuran calling activity, and quantified wetland habitat structure and landscape context. We used canonical correspondence analysis (CCA) to examine patterns in anuran community structure and identify the most important variables associated with those patterns. Urban density at the landscape scale had a significant negative influence on overall anuran abundance and diversity. While every species exhibited a decrease in abundance with increasing urban density, this pattern was especially pronounced for species requiring post-breeding upland habitats. Anurans most affected by urbanization were those associated with short hydroperiods, early breeding activity, and substantial upland habitat use. We suggest that broad-scale landscape fragmentation is an important factor underlying anuran community structure in this region, possibly due to limitations on the accessibility of otherwise suitable habitat in fragmented urban landscapes. This study underscores the importance of a regional approach to amphibian conservation in urban and urbanizing areas; in fragmented landscapes, a network of interconnected wetland and upland habitats may be more likely to support a successful, diverse anuran community than will isolated sites.

Emergence of structured communities through evolutionary dynamics.

Science.gov (United States)

Shtilerman, Elad; Kessler, David A; Shnerb, Nadav M

2015-10-21

Species-rich communities, in which many competing species coexist in a single trophic level, are quite frequent in nature, but pose a formidable theoretical challenge. In particular, it is known that complex competitive systems become unstable and unfeasible when the number of species is large. Recently, many studies have attributed the stability of natural communities to the structure of the interspecific interaction network, yet the nature of such structures and the underlying mechanisms responsible for them remain open questions. Here we introduce an evolutionary model, based on the generic Lotka-Volterra competitive framework, from which a stable, structured, diverse community emerges spontaneously. The modular structure of the competition matrix reflects the phylogeny of the community, in agreement with the hierarchial taxonomic classification. Closely related species tend to have stronger niche overlap and weaker fitness differences, as opposed to pairs of species from different modules. The competitive-relatedness hypothesis and the idea of emergent neutrality are discussed in the context of this evolutionary model. Copyright © 2015 Elsevier Ltd. All rights reserved.

[Species, functional, structural diversity of typical plant communities and their responses to environmental factors in Miao Archipelago, China.

Science.gov (United States)

Zheng, Li Ting; Su, Tian; Liu, Xiang Yu; Yin, Fang; Guo, Chao; Tuo, Bin; Yan, En Rong

2018-02-01

Island vegetation plays an important role in biodiversity research across the world. The study of plant diversity in island is helpful for understanding the mechanism of plant diversity maintenance under land-sea interaction. Here, four typical plant communities (Quercus acutissima community, Robinia pseudoacacia community, Pinus thunbergii community and Vitex negundo community) in Miao Archipelago were selected to examine the species, functional and structural diversities and their responses to environmental factors at the community scale by using species diversity indices, functional diversity indices, as well as structural diversity indices. The results showed that the species richness and Rao index of P. thunbergii community was higher than that of Q. acutissima community and R. pseudoacacia community, but the structural diversity was lower. The species diversity and structural diversity of V. Negundo shrub were lower than that of forest community, but the functional diversity was higher than some forest communities. The relationship between the diversity of typical plant communities in island area illustrated a significant positive correlation between species richness with Rao index and tree height diversity, however the correlation with functional evenness was significantly negative. The structural diversity and functional evenness were determined by slope with negative and positive relationships, respectively. Functional heterogeneity, functional divergence and species diversity were affected largely by soil physical and chemical properties, displaying the positive relationship with soil bulk density and soil total carbon content, and a negative relationship with soil water content. In conclusion, diversity pattern of plant community in Miao Archipelago reflected not only the characteristics in mainland vegetation but also the special nature of the sea island.

Phase synchronization on small-world networks with community structure

International Nuclear Information System (INIS)

Xiao-Hua, Wang; Li-Cheng, Jiao; Jian-She, Wu

2010-01-01

In this paper, we propose a simple model that can generate small-world network with community structure. The network is introduced as a tunable community organization with parameter r, which is directly measured by the ratio of inter- to intra-community connectivity, and a smaller r corresponds to a stronger community structure. The structure properties, including the degree distribution, clustering, the communication efficiency and modularity are also analysed for the network. In addition, by using the Kuramoto model, we investigated the phase synchronization on this network, and found that increasing the fuzziness of community structure will markedly enhance the network synchronizability; however, in an abnormal region (r ≤ 0.001), the network has even worse synchronizability than the case of isolated communities (r = 0). Furthermore, this network exhibits a remarkable synchronization behaviour in topological scales: the oscillators of high densely interconnected communities synchronize more easily, and more rapidly than the whole network. (general)

Does mechanical disturbance affect the performance and species composition of submerged macrophyte communities?

Science.gov (United States)

Zhang, Qian; Xu, Ying-Shou; Huang, Lin; Xue, Wei; Sun, Gong-Qi; Zhang, Ming-Xiang; Yu, Fei-Hai

2014-05-01

Submerged macrophyte communities are frequently subjected to disturbance of various frequency and strength. However, there is still little experimental evidence on how mechanical disturbance affects the performance and species composition of such plant communities. In a greenhouse experiment, we constructed wetland communities consisting of five co-occurring clonal submerged macrophyte species (Hydrilla verticillata, Elodea canadensis, Ceratophyllum demersum, Chara fragilis, and Myriophyllum spicatum) and subjected these communities to three mechanical disturbance regimes (no, moderate and strong disturbance). Strong mechanical disturbance greatly decreased overall biomass, number of shoot nodes and total shoot length, and increased species diversity (evenness) of the total community. It also substantially decreased the growth of the most abundant species (H. verticillata), but did not affect growth of the other four species. Our data reveal that strong disturbance can have different effects on different submerged macrophyte species and thus alters the performance and species composition of submerged macrophyte communities.

Seasonal dynamics of ant community structure in the Moroccan Argan Forest.

Science.gov (United States)

El Keroumi, Abderrahim; Naamani, Khalid; Soummane, Hassna; Dahbi, Abdallah

2012-01-01

In this study we describe the structure and composition of ant communities in the endemic Moroccan Argan forest, using pitfall traps sampling technique throughout the four seasons between May 2006 and February 2007. The study focused on two distinct climatic habitats within the Essaouira Argan forest, a semi-continental site at Lahssinate, and a coastal site at Boutazarte. Thirteen different ant species were identified, belonging to seven genera. Monomorium subopacum Smith and Tapinoma simrothi Krausse-Heldrungen (Hymenoptera: Formicidae) were the most abundant and behaviorally dominant ant species in the arganeraie. In addition, more specimens were captured in the semi-continental site than in the coastal area. However, no significant difference was observed in species richness, evenness, or diversity between both sites. Composition and community structure showed clear seasonal dynamics. The number of species, their abundance, their diversity, and their evenness per Argan tree were significantly dissimilar among seasons. The richness (except between summer and autumn), and the abundance and the evenness of ant species among communities, showed a significant difference between the dry period (summer and spring) and the rainy period (winter and autumn). Higher abundance and richness values occurred in the dry period of the year. Ant species dominance and seasonal climatic variations in the arganeraie might be among the main factors affecting the composition, structure, and foraging activity of ant communities. This study, together with recent findings on ant predation behavior below Argan trees, highlights the promising use of dominant ant species as potential agents of Mediterranean fruit fly bio-control in the Argan forest and surrounding ecosystems.

Elevated Atmospheric CO2 and Drought Affect Soil Microbial Community and Functional Diversity Associated with Glycine max

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Junfeng Wang

2017-12-01

Full Text Available Abstract Under the background of climate change, the increase of atmospheric CO2 and drought frequency have been considered as significant influencers on the soil microbial communities and the yield and quality of crop. In this study, impacts of increased ambient CO2 and drought on soil microbial structure and functional diversity of a Stagnic Anthrosol were investigated in phytotron growth chambers, by testing two representative CO2 levels, three soil moisture levels, and two soil cover types (with or without Glycine max. The 16S rDNA and 18S rDNA fragments were amplified to analyze the functional diversity of fungi and bacteria. Results showed that rhizosphere microbial biomass and community structure were significantly affected by drought, but effects differed between fungi and bacteria. Drought adaptation of fungi was found to be easier than that of bacteria. The diversity of fungi was less affected by drought than that of bacteria, evidenced by their higher diversity. Severe drought reduced soil microbial functional diversity and restrained the metabolic activity. Elevated CO2 alone, in the absence of crops (bare soil, did not enhance the metabolic activity of soil microorganisms. Generally, due to the co-functioning of plant and soil microorganisms in water and nutrient use, plants have major impacts on the soil microbial community, leading to atmospheric CO2 enrichment, but cannot significantly reduce the impacts of drought on soil microorganisms.

Factors affecting pharmacy engagement and pharmacy customer devotion in community pharmacy: A structural equation modeling approach.

Science.gov (United States)

Nitadpakorn, Sujin; Farris, Karen B; Kittisopee, Tanattha

2017-01-01

The concept of customer engagement and devotion has been applied in various service businesses to keep the customers with business However, a limited number of studies were performed to examine the context of customer engagement and devotion in pharmacy business which focus on the impact of customer perceptions about pharmacists, perceived quality of pharmacy structure, medication price strategy on pharmacy engagement and pharmacy customer devotion in a pharmacy providing pharmaceutical care to the customers. This study aimed to assess a conceptual model depicting the relationships among customer perceptions about pharmacists, pharmacy quality structure, medication price, customer engagement, and customer devotion. And also aimed to assess and measure if there is a direct or indirect relationship between these factors. A quantitative study was conducted by using self-administered questionnaires. Two hundred and fifty three customers who regularly visited the pharmacy were randomly recruited from a purposively selected 30 community pharmacies in Bangkok. The survey was completed during February to April 2016. A structural equation model (SEM) was used to assess the direct and indirect relationships between constructs. A total of 253/300 questionnaires were returned for analysis, and the response rate was 84%. Only perceptions about pharmacist in customers receiving professional pharmacy services was statically significant regarding relationship with pharmacy engagement (beta=0.45). Concurrently, the model from empirical data fit with the hypothetical model (p-value = 0.06, adjusted chi-square (CMIN/DF)=1.16, Goodness of Fit Index (GFI)=0.93, Comparatively Fit Index (CFI)=0.99, and Root Mean Square Error Approximation (RMSEA)=0.03). The study confirmed the indirect positive influence of customer perceptions about pharmacist on pharmacy customer devotion in providing pharmacy services via pharmacy engagement It was customer perceptions about pharmacist that influenced

Factors affecting pharmacy engagement and pharmacy customer devotion in community pharmacy: A structural equation modeling approach

Directory of Open Access Journals (Sweden)

Nitadpakorn S

2017-09-01

Full Text Available Background: The concept of customer engagement and devotion has been applied in various service businesses to keep the customers with business However, a limited number of studies were performed to examine the context of customer engagement and devotion in pharmacy business which focus on the impact of customer perceptions about pharmacists, perceived quality of pharmacy structure, medication price strategy on pharmacy engagement and pharmacy customer devotion in a pharmacy providing pharmaceutical care to the customers. Objective: This study aimed to assess a conceptual model depicting the relationships among customer perceptions about pharmacists, pharmacy quality structure, medication price, customer engagement, and customer devotion. And also aimed to assess and measure if there is a direct or indirect relationship between these factors. Methods: A quantitative study was conducted by using self-administered questionnaires. Two hundred and fifty three customers who regularly visited the pharmacy were randomly recruited from a purposively selected 30 community pharmacies in Bangkok. The survey was completed during February to April 2016. A structural equation model (SEM was used to assess the direct and indirect relationships between constructs. Results: A total of 253/300 questionnaires were returned for analysis, and the response rate was 84%. Only perceptions about pharmacist in customers receiving professional pharmacy services was statically significant regarding relationship with pharmacy engagement (beta=0.45. Concurrently, the model from empirical data fit with the hypothetical model (p-value = 0.06, adjusted chi-square (CMIN/DF=1.16, Goodness of Fit Index (GFI=0.93, Comparatively Fit Index (CFI=0.99, and Root Mean Square Error Approximation (RMSEA=0.03. Conclusion: The study confirmed the indirect positive influence of customer perceptions about pharmacist on pharmacy customer devotion in providing pharmacy services via pharmacy

Response of soil microbial activities and microbial community structure to vanadium stress.

Science.gov (United States)

Xiao, Xi-Yuan; Wang, Ming-Wei; Zhu, Hui-Wen; Guo, Zhao-Hui; Han, Xiao-Qing; Zeng, Peng

2017-08-01

High levels of vanadium (V) have long-term, hazardous impacts on soil ecosystems and biological processes. In the present study, the effects of V on soil enzymatic activities, basal respiration (BR), microbial biomass carbon (MBC), and the microbial community structure were investigated through 12-week greenhouse incubation experiments. The results showed that V content affected soil dehydrogenase activity (DHA), BR, and MBC, while urease activity (UA) was less sensitive to V stress. The average median effective concentration (EC 50 ) thresholds of V were predicted using a log-logistic dose-response model, and they were 362mgV/kg soil for BR and 417mgV/kg soil for DHA. BR and DHA were more sensitive to V addition and could be used as biological indicators for soil V pollution. According to a polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis, the structural diversity of the microbial community decreased for soil V contents ranged between 254 and 1104mg/kg after 1 week of incubation. As the incubation time increased, the diversity of the soil microbial community structure increased for V contents ranged between 354 and 1104mg/kg, indicating that some new V-tolerant bacterial species might have replicated under these conditions. Copyright © 2017 Elsevier Inc. All rights reserved.

[Community structure and diversity of soil arthropods in naturally restored sandy grasslands after grazing].

Science.gov (United States)

Liu, Ren-tao; Zhao, Ha-lin; Zhao, Xue-yong

2010-11-01

Taking the Naiman Desertification Research Station under Chinese Academy of Sciences as a base, an investigation was conducted on the community structure of soil arthropods in the naturally restored sandy grasslands after different intensity grazing disturbance, with the effects of vegetation and soil on this community structure approached. In the non-grazing grassland, soil arthropods were rich in species and more in individuals, and had the highest diversity. In the restored grassland after light grazing, soil arthropods had the lowest evenness and diversity. In the restored grassland after moderate grazing, the individuals of soil arthropods were lesser but the major groups were more, and the evenness and diversity were higher. In the restored grassland after heavy grazing, the individuals of soil arthropods were more but the major groups were lesser, and the diversity was higher. Plant individuals' number, vegetation height and coverage, and soil alkalinity were the main factors affecting the soil arthropod community in naturally restored grasslands after different intensity grazing disturbance. It was implied that after 12-year exclosure of grassland, soil arthropod community could be recovered to some degree, while grazing disturbance had long-term negative effects on the arthropod community.

Does the edge effect influence plant community structure in a tropical dry forest?

Directory of Open Access Journals (Sweden)

Diogo Gallo Oliveira

2013-04-01

Full Text Available Edge effects are considered a key factor in regulating the structure of plant communities in different ecosystems. However, regardless to few studies, edge influence does not seem to be decisive in semiarid regions such as the Brazilian tropical dry forest known as Caatinga but this issue remains inconclusive. The present study tests the null hypothesis that the plant community of shrubs and trees does not change in its structure due to edge effects. Twenty-four plots (20 x 20 m were set up in a fragment of Caatinga, in which 12 plots were in the forest edges and 12 plots were inside the fragment. Tree richness, abundance and species composition did not differ between edge and interior plots. The results of this study are in agreement with the pattern previously found for semiarid environments and contrasts with previous results obtained in different environments such as Rainforests, Savanna and Forest of Araucaria, which indicate abrupt differences between the border and interior of the plant communities in these ecosystems, and suggest that the community of woody plants of the Caatinga is not ecologically affected by the presence of edges.

Community structure informs species geographic distributions

KAUST Repository

Montesinos-Navarro, Alicia

2018-05-23

Understanding what determines species\\' geographic distributions is crucial for assessing global change threats to biodiversity. Measuring limits on distributions is usually, and necessarily, done with data at large geographic extents and coarse spatial resolution. However, survival of individuals is determined by processes that happen at small spatial scales. The relative abundance of coexisting species (i.e. \\'community structure\\') reflects assembly processes occurring at small scales, and are often available for relatively extensive areas, so could be useful for explaining species distributions. We demonstrate that Bayesian Network Inference (BNI) can overcome several challenges to including community structure into studies of species distributions, despite having been little used to date. We hypothesized that the relative abundance of coexisting species can improve predictions of species distributions. In 1570 assemblages of 68 Mediterranean woody plant species we used BNI to incorporate community structure into Species Distribution Models (SDMs), alongside environmental information. Information on species associations improved SDM predictions of community structure and species distributions moderately, though for some habitat specialists the deviance explained increased by up to 15%. We demonstrate that most species associations (95%) were positive and occurred between species with ecologically similar traits. This suggests that SDM improvement could be because species co-occurrences are a proxy for local ecological processes. Our study shows that Bayesian Networks, when interpreted carefully, can be used to include local conditions into measurements of species\\' large-scale distributions, and this information can improve the predictions of species distributions.

Land-use and land-management change: relationships with earthworm and fungi communities and soil structural properties.

Science.gov (United States)

Spurgeon, David J; Keith, Aidan M; Schmidt, Olaf; Lammertsma, Dennis R; Faber, Jack H

2013-12-01

Change in land use and management can impact massively on soil ecosystems. Ecosystem engineers and other functional biodiversity in soils can be influenced directly by such change and this in turn can affect key soil functions. Here, we employ meta-analysis to provide a quantitative assessment of the effects of changes in land use and land management across a range of successional/extensification transitions (conventional arable → no or reduced tillage → grassland → wooded land) on community metrics for two functionally important soil taxa, earthworms and fungi. An analysis of the relationships between community change and soil structural properties was also included. Meta-analysis highlighted a consistent trend of increased earthworm and fungal community abundances and complexity following transitions to lower intensity and later successional land uses. The greatest changes were seen for early stage transitions, such as introduction of reduced tillage regimes and conversion to grassland from arable land. Not all changes, however, result in positive effects on the assessed community metrics. For example, whether woodland conversion positively or negatively affects community size and complexity depends on woodland type and, potentially, the changes in soil properties, such as pH, that may occur during conversion. Alterations in soil communities tended to facilitate subsequent changes in soil structure and hydrology. For example, increasing earthworm abundances and functional group composition were shown to be positively correlated with water infiltration rate (dependent on tillage regime and habitat characteristics); while positive changes in fungal biomass measures were positively associated with soil microaggregate stability. These findings raise the potential to manage landscapes to increase ecosystem service provision from soil biota in relation to regulation of soil structure and water flow.

Coal mining activities change plant community structure due to air pollution and soil degradation.

Science.gov (United States)

Pandey, Bhanu; Agrawal, Madhoolika; Singh, Siddharth

2014-10-01

The aim of this study was to investigate the effects of coal mining activities on the community structures of woody and herbaceous plants. The response of individual plants of community to defilement caused by coal mining was also assessed. Air monitoring, soil physico-chemical and phytosociological analyses were carried around Jharia coalfield (JCF) and Raniganj coalfield. The importance value index of sensitive species minified and those of tolerant species enhanced with increasing pollution load and altered soil quality around coal mining areas. Although the species richness of woody and herbaceous plants decreased with higher pollution load, a large number of species acclimatized to the stress caused by the coal mining activities. Woody plant community at JCF was more affected by coal mining than herbaceous community. Canonical correspondence analysis revealed that structure of herbaceous community was mainly driven by soil total organic carbon, soil nitrogen, whereas woody layer community was influenced by sulphur dioxide in ambient air, soil sulphate and soil phosphorus. The changes in species diversity observed at mining areas indicated an increase in the proportion of resistant herbs and grasses showing a tendency towards a definite selection strategy of ecosystem in response to air pollution and altered soil characteristics.

Leaf-litter amount as a factor in the structure of a ponerine ants community (Hymenoptera, Formicidae, Ponerinae in an eastern Amazonian rainforest, Brazil

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Alexandro Herbert dos Santos Bastos

2011-12-01

Full Text Available Leaf-litter amount as a factor in the structure of a ponerine ants community (Hymenoptera, Formicidae, Ponerinae in an eastern Amazonian rainforest, Brazil. Leaf-litter may be an important factor in structuring ponerine ant communities (Hymenoptera, Formicidae, Ponerinae in tropical rainforests. We specifically examined how leaf-litter affects the structure of a ponerine ant community in primary Amazonian rainforest sites at the Ferreira Penna Scientific Station, Pará, Brazil. A total of 53 species belonging to eight genera of three ponerine tribes were collected with mini-Winkler extractors. The amount of leaf-litter positively affected the abundance and richness of the ponerine ant community, and also influenced species composition. Nearby samples often had low species similarity, especially when adjacent samples differed in the amount of leaf-litter. Leaf-litter availability in Amazonian primary forests is a key factor for distribution of ground-dwelling ponerine species, even at small scales.

Community structure of grassland ground-dwelling arthropods along increasing soil salinities.

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Pan, Chengchen; Feng, Qi; Liu, Jiliang; Li, Yulin; Li, Yuqiang; Yu, Xiaoya

2018-03-01

Ground-dwelling arthropod communities are influenced by numerous biotic and abiotic factors. Little is known, however, about the relative importance of vegetation structure and abiotic environmental factors on the patterns of ground-dwelling arthropod community across a wide range of soil salinities. Here, a field survey was conducted to assess the driving forces controlling ground-dwelling arthropod community in the salinized grasslands in the Hexi Corridor, Gansu Province, China. The data were analyzed by variance partitioning with canonical correspondence analysis (CCA). We found that vegetation structure and edaphic factors were at least of similar importance to the pattern of the whole ground-dwelling arthropod community. However, when all collected ground-dwelling arthropods were categorized into three trophic guilds (predators, herbivores, and decomposers), as these groups use different food sources, their populations were controlled by different driving forces. Predators and decomposers were mainly determined by biotic factors such as vegetation cover and aboveground plant biomass and herbivores by plant density and vegetation cover. Abiotic factors were also major determinants for the variation occurring in these guilds, with predators strongly affected by soil electrical conductivity (EC) and the content of fine particles (silt + clay, CS), herbivores by soil N:P, EC, and CS, and decomposers by soil EC and organic matter content (SOM). Since plant cover, density, and aboveground biomass can indicate resource availability, which are mainly constrained by soil N:P, EC, CS, and SOM, we consider that the ground-dwelling arthropod community in the salinized grasslands was mainly influenced by resource availability.

Psychometric properties of Positive and Negative Affect Schedule (PANAS) original and short forms in an African American community sample.

Science.gov (United States)

Merz, Erin L; Malcarne, Vanessa L; Roesch, Scott C; Ko, Celine M; Emerson, Marc; Roma, Vincenzo G; Sadler, Georgia Robins

2013-12-01

The Positive and Negative Affect Schedule (PANAS) has been widely used as a self-report measure of affect in community and clinical contexts. However, evaluations of the psychometric properties of PANAS scores have been limited in diverse ethnic groups. Several short forms of the PANAS have also been proposed, but very little is known about the psychometric properties of these versions. The present study investigated the psychometric properties, including the factor structure of the original PANAS and two short forms in an African American community sample (N=239). Descriptive, internal consistency reliability, factorial validity, and measurement invariance analyses were conducted. All PANAS subscales from the original and short forms had adequate internal consistency. For the original PANAS, the model specifying three correlated factors (Positive Affect, Afraid, Upset) with correlated uniquenesses from redundant items provided the best fit to the data. However, the two-factor model (Positive Affect, Negative Affect) with correlated uniquenesses was also supported. For both short forms, the two-factor model with correlated uniquenesses fit the data best. Factors from all forms were generally invariant across age and gender, although there was some minor invariance at the item level. Participants were from a limited geographic area and one ethnic group. Indicators of anxiety, depression, and cultural characteristics were not measured. The factor structure was replicated, suggesting no immediate concerns regarding the valid interpretation of PANAS scores. The results support the reliability and validity of the PANAS and its short forms for use among African Americans. © 2013 Elsevier B.V. All rights reserved.

Transformative Learning, Affect, and Reciprocal Care in Community Engagement

Science.gov (United States)

Holmes, Ashley J.

2015-01-01

Drawing on interviews with writing teachers, this article highlights some of the affective responses that may arise for students, community partners, and teachers when we situate our pedagogies in public sites beyond the classroom. I analyze a teacher-narrated moment of student distress to demonstrate how theories of transformative learning might…

How spatial variation in areal extent and configuration of labile vegetation states affect the riparian bird community in Arctic tundra.

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John-André Henden

Full Text Available The Arctic tundra is currently experiencing an unprecedented combination of climate change, change in grazing pressure by large herbivores and growing human activity. Thickets of tall shrubs represent a conspicuous vegetation state in northern and temperate ecosystems, where it serves important ecological functions, including habitat for wildlife. Thickets are however labile, as tall shrubs respond rapidly to both abiotic and biotic environmental drivers. Our aim was to assess how large-scale spatial variation in willow thicket areal extent, configuration and habitat structure affected bird abundance, occupancy rates and species richness so as to provide an empirical basis for predicting the outcome of environmental change for riparian tundra bird communities. Based on a 4-year count data series, obtained through a large-scale study design in low arctic tundra in northern Norway, statistical hierarchical community models were deployed to assess relations between habitat configuration and bird species occupancy and community richness. We found that species abundance, occupancy and richness were greatly affected by willow areal extent and configuration, habitat features likely to be affected by intense ungulate browsing as well as climate warming. In sum, total species richness was maximized in large and tall willow patches of small to intermediate degree of fragmentation. These community effects were mainly driven by responses in the occupancy rates of species depending on tall willows for foraging and breeding, while species favouring other vegetation states were not affected. In light of the predicted climate driven willow shrub encroachment in riparian tundra habitats, our study predicts that many bird species would increase in abundance, and that the bird community as a whole could become enriched. Conversely, in tundra regions where overabundance of large herbivores leads to decreased areal extent, reduced height and increased fragmentation

Effects of oxytetracycline on the abundance and community structure of nitrogen-fixing bacteria during cattle manure composting.

Science.gov (United States)

Sun, Jiajun; Qian, Xun; Gu, Jie; Wang, Xiaojuan; Gao, Hua

2016-09-01

The effects of oxytetracycline (OTC) on nitrogen-fixing bacterial communities were investigated during cattle manure composting. The abundance and community structure of nitrogen-fixing bacteria were determined by qPCR and denaturing gradient gel electrophoresis (DGGE), respectively. The matrix was spiked with OTC at four levels: no OTC, 10mg/kg dry weight (DW) OTC (L), 60mg/kg DW OTC (M), and 200mg/kg DW OTC (H). The high temperature period of composting was shorter with M and H, and the decline in temperature during the cooling stage was accelerated by OTC. OTC had a concentration-dependent inhibitory effect on the nitrogenase activity during early composting, and the nifH gene abundance declined significantly during the later composting stage. The DGGE profile and statistical analysis showed that OTC changed the nitrogen-fixing bacterial community succession and reduced the community richness and dominance. The nitrogen-fixing bacterial community structure was affected greatly by the high level of OTC. Copyright © 2016. Published by Elsevier Ltd.

Short-term responses and resistance of soil microbial community structure to elevated CO2 and N addition in grassland mesocosms.

Science.gov (United States)

Simonin, Marie; Nunan, Naoise; Bloor, Juliette M G; Pouteau, Valérie; Niboyet, Audrey

2017-05-01

Nitrogen (N) addition is known to affect soil microbial communities, but the interactive effects of N addition with other drivers of global change remain unclear. The impacts of multiple global changes on the structure of microbial communities may be mediated by specific microbial groups with different life-history strategies. Here, we investigated the combined effects of elevated CO2 and N addition on soil microbial communities using PLFA profiling in a short-term grassland mesocosm experiment. We also examined the linkages between the relative abundance of r- and K-strategist microorganisms and resistance of the microbial community structure to experimental treatments. N addition had a significant effect on microbial community structure, likely driven by concurrent increases in plant biomass and in soil labile C and N. In contrast, microbial community structure did not change under elevated CO2 or show significant CO2 × N interactions. Resistance of soil microbial community structure decreased with increasing fungal/bacterial ratio, but showed a positive relationship with the Gram-positive/Gram-negative bacterial ratio. Our findings suggest that the Gram-positive/Gram-negative bacteria ratio may be a useful indicator of microbial community resistance and that K-strategist abundance may play a role in the short-term stability of microbial communities under global change. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Information transfer in community structured multiplex networks

Science.gov (United States)

Solé Ribalta, Albert; Granell, Clara; Gómez, Sergio; Arenas, Alex

2015-08-01

The study of complex networks that account for different types of interactions has become a subject of interest in the last few years, specially because its representational power in the description of users interactions in diverse online social platforms (Facebook, Twitter, Instagram, etc.). The mathematical description of these interacting networks has been coined under the name of multilayer networks, where each layer accounts for a type of interaction. It has been shown that diffusive processes on top of these networks present a phenomenology that cannot be explained by the naive superposition of single layer diffusive phenomena but require the whole structure of interconnected layers. Nevertheless, the description of diffusive phenomena on multilayer networks has obviated the fact that social networks have strong mesoscopic structure represented by different communities of individuals driven by common interests, or any other social aspect. In this work, we study the transfer of information in multilayer networks with community structure. The final goal is to understand and quantify, if the existence of well-defined community structure at the level of individual layers, together with the multilayer structure of the whole network, enhances or deteriorates the diffusion of packets of information.

Information transfer in community structured multiplex networks

Directory of Open Access Journals (Sweden)

Albert eSolé Ribalta

2015-08-01

Full Text Available The study of complex networks that account for different types of interactions has become a subject of interest in the last few years, specially because its representational power in the description of users interactions in diverse online social platforms (Facebook, Twitter, Instagram, etc.. The mathematical description of these interacting networks has been coined under the name of multilayer networks, where each layer accounts for a type of interaction. It has been shown that diffusive processes on top of these networks present a phenomenology that cannot be explained by the naive superposition of single layer diffusive phenomena but require the whole structure of interconnected layers. Nevertheless, the description of diffusive phenomena on multilayer networks has obviated the fact that social networks have strong mesoscopic structure represented by different communities of individuals driven by common interests, or any other social aspect. In this work, we study the transfer of information in multilayer networks with community structure. The final goal is to understand and quantify, if the existence of well-defined community structure at the level of individual layers, together with the multilayer structure of the whole network, enhances or deteriorates the diffusion of packets of information.

Evidence for the functional significance of diazotroph community structure in soil.

Science.gov (United States)

Hsu, Shi-Fang; Buckley, Daniel H

2009-01-01

Microbial ecologists continue to seek a greater understanding of the factors that govern the ecological significance of microbial community structure. Changes in community structure have been shown to have functional significance for processes that are mediated by a narrow spectrum of organisms, such as nitrification and denitrification, but in some cases, functional redundancy in the community seems to buffer microbial ecosystem processes. The functional significance of microbial community structure is frequently obscured by environmental variation and is hard to detect in short-term experiments. We examine the functional significance of free-living diazotrophs in a replicated long-term tillage experiment in which extraneous variation is minimized and N-fixation rates can be related to soil characteristics and diazotroph community structure. Soil characteristics were found to be primarily impacted by tillage management, whereas N-fixation rates and diazotroph community structure were impacted by both biomass management practices and interactions between tillage and biomass management. The data suggest that the variation in diazotroph community structure has a greater impact on N-fixation rates than do soil characteristics at the site. N-fixation rates displayed a saturating response to increases in diazotroph community diversity. These results show that the changes in the community structure of free-living diazotrophs in soils can have ecological significance and suggest that this response is related to a change in community diversity.

Information needs of the Chinese community affected by cancer: A systematic review.

Science.gov (United States)

Lim, Bee Teng; Butow, Phyllis; Mills, Jill; Miller, Annie; Goldstein, David

2017-10-01

The information needs of patients and carers from culturally and linguistically diverse backgrounds, including from the Chinese community, are not well understood, and there has been no previous synthesis of the literature. We conducted a systematic review of the information needs of the Chinese community affected by cancer. Database, reference list, and author searches were conducted to identify studies reporting information needs of the Chinese community affected by cancer. Data synthesis was undertaken to define categories of information needs. Initial searches yielded 2558 articles. Out of the 40 full-text articles reviewed, 26 met all the eligibility criteria. Cancer-specific, treatment, and prognosis information were the most frequently reported information needs across the cancer care continuum. Similarly, this information was the most commonly reported information needs across different health systems, migration statuses, and Chinese cultural values. Though less frequent, information needs related to interpersonal/social, financial/legal, and body image/sexuality were also raised. Thirteen studies quantified the prevalence of unmet needs, and the most frequently reported unmet needs were related to health system and information, followed by psychological, patient care and support, physical daily living, and sexuality needs. Language and cultural factors were identified in all studies involving Chinese migrants living in English-speaking countries. Failing to meet the information needs of the Chinese community members affected by cancer increases the risk for poor cancer outcomes. Potential interventions such as translated resources, bilingual advocates, an online information portal, and communication aids can be helpful in addressing the unmet needs for this community. Copyright © 2016 John Wiley & Sons, Ltd.

Small but powerful: top predator local extinction affects ecosystem structure and function in an intermittent stream.

Science.gov (United States)

Rodríguez-Lozano, Pablo; Verkaik, Iraima; Rieradevall, Maria; Prat, Narcís

2015-01-01

Top predator loss is a major global problem, with a current trend in biodiversity loss towards high trophic levels that modifies most ecosystems worldwide. Most research in this area is focused on large-bodied predators, despite the high extinction risk of small-bodied freshwater fish that often act as apex consumers. Consequently, it remains unknown if intermittent streams are affected by the consequences of top-predators' extirpations. The aim of our research was to determine how this global problem affects intermittent streams and, in particular, if the loss of a small-bodied top predator (1) leads to a 'mesopredator release', affects primary consumers and changes whole community structures, and (2) triggers a cascade effect modifying the ecosystem function. To address these questions, we studied the top-down effects of a small endangered fish species, Barbus meridionalis (the Mediterranean barbel), conducting an enclosure/exclosure mesocosm experiment in an intermittent stream where B. meridionalis became locally extinct following a wildfire. We found that top predator absence led to 'mesopredator release', and also to 'prey release' despite intraguild predation, which contrasts with traditional food web theory. In addition, B. meridionalis extirpation changed whole macroinvertebrate community composition and increased total macroinvertebrate density. Regarding ecosystem function, periphyton primary production decreased in apex consumer absence. In this study, the apex consumer was functionally irreplaceable; its local extinction led to the loss of an important functional role that resulted in major changes to the ecosystem's structure and function. This study evidences that intermittent streams can be affected by the consequences of apex consumers' extinctions, and that the loss of small-bodied top predators can lead to large ecosystem changes. We recommend the reintroduction of small-bodied apex consumers to systems where they have been extirpated, to restore

Small but powerful: top predator local extinction affects ecosystem structure and function in an intermittent stream.

Directory of Open Access Journals (Sweden)

Pablo Rodríguez-Lozano

Full Text Available Top predator loss is a major global problem, with a current trend in biodiversity loss towards high trophic levels that modifies most ecosystems worldwide. Most research in this area is focused on large-bodied predators, despite the high extinction risk of small-bodied freshwater fish that often act as apex consumers. Consequently, it remains unknown if intermittent streams are affected by the consequences of top-predators' extirpations. The aim of our research was to determine how this global problem affects intermittent streams and, in particular, if the loss of a small-bodied top predator (1 leads to a 'mesopredator release', affects primary consumers and changes whole community structures, and (2 triggers a cascade effect modifying the ecosystem function. To address these questions, we studied the top-down effects of a small endangered fish species, Barbus meridionalis (the Mediterranean barbel, conducting an enclosure/exclosure mesocosm experiment in an intermittent stream where B. meridionalis became locally extinct following a wildfire. We found that top predator absence led to 'mesopredator release', and also to 'prey release' despite intraguild predation, which contrasts with traditional food web theory. In addition, B. meridionalis extirpation changed whole macroinvertebrate community composition and increased total macroinvertebrate density. Regarding ecosystem function, periphyton primary production decreased in apex consumer absence. In this study, the apex consumer was functionally irreplaceable; its local extinction led to the loss of an important functional role that resulted in major changes to the ecosystem's structure and function. This study evidences that intermittent streams can be affected by the consequences of apex consumers' extinctions, and that the loss of small-bodied top predators can lead to large ecosystem changes. We recommend the reintroduction of small-bodied apex consumers to systems where they have been

Coastal ecosystems on a tipping point: global warming and parasitism combine to alter community structure and function.

Science.gov (United States)

Mouritsen, Kim N; Sørensen, Mikkel M; Poulin, Robert; Fredensborg, Brian L

2018-05-16

Mounting evidence suggests that the transmission of certain parasites is facilitated by increasing temperatures, causing their host population to decline. However, no study has yet addressed how temperature and parasitism may combine to shape the functional structure of a whole host community in the face of global warming. Here, we apply an outdoor mesocosm approach supported by field surveys to elucidate this question in a diverse intertidal community of amphipods infected by the pathogenic microphallid trematode, Maritrema novaezealandensis. Under present temperature (17°C) and level of parasitism, the parasite had little impact on the host community. However, elevating the temperature to 21°C in presence of parasites induced massive structural changes: amphipod abundances decreased species-specifically, affecting epibenthic species but leaving infaunal species largely untouched. In effect, species diversity dropped significantly. In contrast, 4-degree higher temperatures in absence of parasitism had limited influence on the amphipod community. Further elevating temperatures (19-26°C) and parasitism, simulating a prolonged heat-wave scenario, resulted in an almost complete parasite-induced extermination of the amphipod community at 26°C. In addition, at 19°C, just two degrees above the present average, a similar temperature-parasite synergistic impact on community structure emerged as seen at 21°C under lower parasite pressure. The heat-wave temperature of 26°C per se affected the amphipod community in a comparable way: species diversity declined and the infaunal species were favoured at the expense of epibenthic species. Our experimental findings are corroborated by field data demonstrating a strong negative relationship between current amphipod species richness and the level of Maritrema parasitism across 12 sites. Hence, owing to the synergistic impact of temperature and parasitism, our study predicts that coastal amphipod communities will deteriorate

Relating microbial community structure to functioning in forest soil organic carbon transformation and turnover.

Science.gov (United States)

You, Yeming; Wang, Juan; Huang, Xueman; Tang, Zuoxin; Liu, Shirong; Sun, Osbert J

2014-03-01

Forest soils store vast amounts of terrestrial carbon, but we are still limited in mechanistic understanding on how soil organic carbon (SOC) stabilization or turnover is controlled by biotic and abiotic factors in forest ecosystems. We used phospholipid fatty acids (PLFAs) as biomarker to study soil microbial community structure and measured activities of five extracellular enzymes involved in the degradation of cellulose (i.e., β-1,4-glucosidase and cellobiohydrolase), chitin (i.e., β-1,4-N-acetylglucosaminidase), and lignin (i.e., phenol oxidase and peroxidase) as indicators of soil microbial functioning in carbon transformation or turnover across varying biotic and abiotic conditions in a typical temperate forest ecosystem in central China. Redundancy analysis (RDA) was performed to determine the interrelationship between individual PFLAs and biotic and abiotic site factors as well as the linkage between soil microbial structure and function. Path analysis was further conducted to examine the controls of site factors on soil microbial community structure and the regulatory pathway of changes in SOC relating to microbial community structure and function. We found that soil microbial community structure is strongly influenced by water, temperature, SOC, fine root mass, clay content, and C/N ratio in soils and that the relative abundance of Gram-negative bacteria, saprophytic fungi, and actinomycetes explained most of the variations in the specific activities of soil enzymes involved in SOC transformation or turnover. The abundance of soil bacterial communities is strongly linked with the extracellular enzymes involved in carbon transformation, whereas the abundance of saprophytic fungi is associated with activities of extracellular enzymes driving carbon oxidation. Findings in this study demonstrate the complex interactions and linkage among plant traits, microenvironment, and soil physiochemical properties in affecting SOC via microbial regulations.

Finding Community Structures In Social Activity Data

KAUST Repository

Peng, Chengbin

2015-05-19

Social activity data sets are increasing in number and volume. Finding community structure in such data is valuable in many applications. For example, understand- ing the community structure of social networks may reduce the spread of epidemics or boost advertising revenue; discovering partitions in tra c networks can help to optimize routing and to reduce congestion; finding a group of users with common interests can allow a system to recommend useful items. Among many aspects, qual- ity of inference and e ciency in finding community structures in such data sets are of paramount concern. In this thesis, we propose several approaches to improve com- munity detection in these aspects. The first approach utilizes the concept of K-cores to reduce the size of the problem. The K-core of a graph is the largest subgraph within which each node has at least K connections. We propose a framework that accelerates community detection. It first applies a traditional algorithm that is relatively slow to the K-core, and then uses a fast heuristic to infer community labels for the remaining nodes. The second approach is to scale the algorithm to multi-processor systems. We de- vise a scalable community detection algorithm for large networks based on stochastic block models. It is an alternating iterative algorithm using a maximum likelihood ap- proach. Compared with traditional inference algorithms for stochastic block models, our algorithm can scale to large networks and run on multi-processor systems. The time complexity is linear in the number of edges of the input network. The third approach is to improve the quality. We propose a framework for non- negative matrix factorization that allows the imposition of linear or approximately linear constraints on each factor. An example of the applications is to find community structures in bipartite networks, which is useful in recommender systems. Our algorithms are compared with the results in recent papers and their quality and e

Controls on bacterial and archaeal community structure and greenhouse gas production in natural, mined, and restored Canadian peatlands

Directory of Open Access Journals (Sweden)

Nathan eBasiliko

2013-07-01

Full Text Available Northern peatlands are important global C reservoirs, largely because of their slow rates of microbial C mineralization. Particularly in sites that are heavily influenced by anthropogenic disturbances, there is scant information about microbial ecology and whether or not microbial community structure influences greenhouse gas production. This work characterized communities of bacteria and archaea using terminal restriction fragment length polymorphism and sequence analysis of 16S rRNA and functional genes across eight natural, mined, or restored peatlands in two locations in eastern Canada. Correlations were explored among chemical properties of peat, bacterial and archaeal community structure, and carbon dioxide and methane production rates under oxic and anoxic conditions. Bacteria and archaea similar to those found in other peat soil environments were detected. In contrast to other reports, methanogen diversity was low in our study, with only 2 groups of known or suspected methanogens. Although mining and restoration affected substrate availability and microbial activity, these land-uses did not consistently affect bacterial or archaeal community composition. In fact, larger differences were observed between the two locations and between oxic and anoxic peat samples than between mined and restored sites, with anoxic samples characterized by less detectable bacterial diversity and stronger dominance by members of the phylum Acidobacteria. There were also no apparent strong linkages between prokaryote community structure and methane or carbon dioxide production, suggesting that different organisms exhibit functional redundancy and/or that the same taxa function at very different rates when exposed to different peat substrates. In contrast to other earlier work focusing on fungal communities across similar mined and restored peatlands, bacterial and archaeal communities appeared to be more resistant or resilient to peat substrate changes brought

Detecting the overlapping and hierarchical community structure in complex networks

International Nuclear Information System (INIS)

Lancichinetti, Andrea; Fortunato, Santo; Kertesz, Janos

2009-01-01

Many networks in nature, society and technology are characterized by a mesoscopic level of organization, with groups of nodes forming tightly connected units, called communities or modules, that are only weakly linked to each other. Uncovering this community structure is one of the most important problems in the field of complex networks. Networks often show a hierarchical organization, with communities embedded within other communities; moreover, nodes can be shared between different communities. Here, we present the first algorithm that finds both overlapping communities and the hierarchical structure. The method is based on the local optimization of a fitness function. Community structure is revealed by peaks in the fitness histogram. The resolution can be tuned by a parameter enabling different hierarchical levels of organization to be investigated. Tests on real and artificial networks give excellent results.

Community structure affects annual grass weed invasion during restoration of a shrub-steppe ecosystem

Science.gov (United States)

Phil S. Allen; Susan E. Meyer

2014-01-01

Ecological restoration of shrub-steppe communities in the western United States is often hampered by invasion of exotic annual grasses during the process. An important question is how to create restored communities that can better resist reinvasion by these weeds. One hypothesis is that communities comprised of species that are functionally similar to the invader will...

Dynamical community structure of populations evolving on genotype networks

International Nuclear Information System (INIS)

Capitán, José A.; Aguirre, Jacobo; Manrubia, Susanna

2015-01-01

Neutral evolutionary dynamics of replicators occurs on large and heterogeneous networks of genotypes. These networks, formed by all genotypes that yield the same phenotype, have a complex architecture that conditions the molecular composition of populations and their movements on genome spaces. Here we consider as an example the case of populations evolving on RNA secondary structure neutral networks and study the community structure of the network revealed through dynamical properties of the population at equilibrium and during adaptive transients. We unveil a rich hierarchical community structure that, eventually, can be traced back to the non-trivial relationship between RNA secondary structure and sequence composition. We demonstrate that usual measures of modularity that only take into account the static, topological structure of networks, cannot identify the community structure disclosed by population dynamics

Cooperative Agreements to Support Communities Affected by the BP Oil Spill

Science.gov (United States)

The environmental justice cooperative agreements are designed to support communities in Alabama, Florida, Louisiana, Mississippi, and Texas that are directly affected by the Deepwater Horizon oil spill in the Gulf of Mexico.

Psychological Challenges Affecting Primary School Going Orphans In Wanganui Community Zimbabwe.

Directory of Open Access Journals (Sweden)

Mbwirire John

2017-04-01

Full Text Available This study sought to identify psychological challenges affecting primary school orphans in Wanganui Community in Zimbabwe. The study employed a mixed method approach combining questionnaires with teachers and care givers interview sessions with orphans and in-depth interviews with community socialdevelopment worker. The study finds that lack of love lack of attention and withdrawal were the main signs and symptoms of psychological challenge in the community. The study revealed that the term and symptoms of psychological challenges were understood differently between African context and Western context. The study recommended that action must be taken as soon as possible once the signs and symptoms which include lack of love lack of attention to rectify the psychological challenges faced by the community.

Shifts of community composition and population density substantially affect ecosystem function despite invariant richness

NARCIS (Netherlands)

Spaak, Jurg W.; Baert, Jan M.; Baird, Donald J.; Eisenhauer, Nico; Maltby, Lorraine; Pomati, Francesco; Radchuk, Viktoriia; Rohr, Jason R.; Brink, van den Paul J.; Laender, De Frederik

2017-01-01

There has been considerable focus on the impacts of environmental change on ecosystem function arising from changes in species richness. However, environmental change may affect ecosystem function without affecting richness, most notably by affecting population densities and community

Phylogenetic structure in tropical hummingbird communities

DEFF Research Database (Denmark)

Graham, Catherine H; Parra, Juan L; Rahbek, Carsten

2009-01-01

How biotic interactions, current and historical environment, and biogeographic barriers determine community structure is a fundamental question in ecology and evolution, especially in diverse tropical regions. To evaluate patterns of local and regional diversity, we quantified the phylogenetic...... composition of 189 hummingbird communities in Ecuador. We assessed how species and phylogenetic composition changed along environmental gradients and across biogeographic barriers. We show that humid, low-elevation communities are phylogenetically overdispersed (coexistence of distant relatives), a pattern...... that is consistent with the idea that competition influences the local composition of hummingbirds. At higher elevations communities are phylogenetically clustered (coexistence of close relatives), consistent with the expectation of environmental filtering, which may result from the challenge of sustaining...

A new hierarchical method to find community structure in networks

Science.gov (United States)

Saoud, Bilal; Moussaoui, Abdelouahab

2018-04-01

Community structure is very important to understand a network which represents a context. Many community detection methods have been proposed like hierarchical methods. In our study, we propose a new hierarchical method for community detection in networks based on genetic algorithm. In this method we use genetic algorithm to split a network into two networks which maximize the modularity. Each new network represents a cluster (community). Then we repeat the splitting process until we get one node at each cluster. We use the modularity function to measure the strength of the community structure found by our method, which gives us an objective metric for choosing the number of communities into which a network should be divided. We demonstrate that our method are highly effective at discovering community structure in both computer-generated and real-world network data.

Uncovering the community structure associated with the diffusion dynamics on networks

International Nuclear Information System (INIS)

Cheng, Xue-Qi; Shen, Hua-Wei

2010-01-01

As two main focuses of the study of complex networks, the community structure and the dynamics on networks have both attracted much attention in various scientific fields. However, it is still an open question how the community structure is associated with the dynamics on complex networks. In this paper, through investigating the diffusion process taking place on networks, we demonstrate that the intrinsic community structure of networks can be revealed by the stable local equilibrium states of the diffusion process. Furthermore, we show that such community structure can be directly identified through the optimization of the conductance of the network, which measures how easily the diffusion among different communities occurs. Tests on benchmark networks indicate that the conductance optimization method significantly outperforms the modularity optimization methods in identifying the community structure of networks. Applications to real world networks also demonstrate the effectiveness of the conductance optimization method. This work provides insights into the multiple topological scales of complex networks, and the community structure obtained can naturally reflect the diffusion capability of the underlying network

Influence of phosphorus availability on the community structure and physiology of cultured biofilms.

Science.gov (United States)

Li, Shuangshuang; Wang, Chun; Qin, Hongjie; Li, Yinxia; Zheng, Jiaoli; Peng, Chengrong; Li, Dunhai

2016-04-01

Biofilms have important effects on nutrient cycling in aquatic ecosystems. However, publications about the community structure and functions under laboratory conditions are rare. This study focused on the developmental and physiological properties of cultured biofilms under various phosphorus concentrations performed in a closely controlled continuous flow incubator. The results showed that the biomass (Chl a) and photosynthesis of algae were inhibited under P-limitation conditions, while the phosphatase activity and P assimilation rate were promoted. The algal community structure of biofilms was more likely related to the colonization stage than with the phosphorus availability. Cyanobacteria were more competitive than other algae in biofilms, particularly when cultured under low P levels. A dominance shift occurred from non-filamentous algae in the early stage to filamentous algae in the mid and late stages under P concentrations of 0.01, 0.1 and 0.6 mg/L. However, the total N content, dry weight biomass and bacterial community structure of biofilms were unaffected by phosphorus availability. This may be attributed to the low respiration rate, high accumulation of extracellular polymeric substances and high alkaline phosphatase activity in biofilms when phosphorus availability was low. The bacterial community structure differed over time, while there was little difference between the four treatments, which indicated that it was mainly affected by the colonization stage of the biofilms rather than the phosphorus availability. Altogether, these results suggested that the development of biofilms was influenced by the phosphorus availability and/or the colonization stage and hence determined the role that biofilms play in the overlying water. Copyright © 2015. Published by Elsevier B.V.

Influence of plankton community structure on the sinking velocity of marine aggregates

Science.gov (United States)

Bach, L. T.; Boxhammer, T.; Larsen, A.; Hildebrandt, N.; Schulz, K. G.; Riebesell, U.

2016-08-01

About 50 Gt of carbon is fixed photosynthetically by surface ocean phytoplankton communities every year. Part of this organic matter is reprocessed within the plankton community to form aggregates which eventually sink and export carbon into the deep ocean. The fraction of organic matter leaving the surface ocean is partly dependent on aggregate sinking velocity which accelerates with increasing aggregate size and density, where the latter is controlled by ballast load and aggregate porosity. In May 2011, we moored nine 25 m deep mesocosms in a Norwegian fjord to assess on a daily basis how plankton community structure affects material properties and sinking velocities of aggregates (Ø 80-400 µm) collected in the mesocosms' sediment traps. We noted that sinking velocity was not necessarily accelerated by opal ballast during diatom blooms, which could be due to relatively high porosity of these rather fresh aggregates. Furthermore, estimated aggregate porosity (Pestimated) decreased as the picoautotroph (0.2-2 µm) fraction of the phytoplankton biomass increased. Thus, picoautotroph-dominated communities may be indicative for food webs promoting a high degree of aggregate repackaging with potential for accelerated sinking. Blooms of the coccolithophore Emiliania huxleyi revealed that cell concentrations of 1500 cells/mL accelerate sinking by about 35-40%, which we estimate (by one-dimensional modeling) to elevate organic matter transfer efficiency through the mesopelagic from 14 to 24%. Our results indicate that sinking velocities are influenced by the complex interplay between the availability of ballast minerals and aggregate packaging; both of which are controlled by plankton community structure.

[Community structure of soil fauna in Eucalyptus grandis plantations at different slope locations].

Science.gov (United States)

Zhao, Yu; Zhong, Yu; Zhang, Jian; Yang, Wan-qin

2010-09-01

To understand the effects of slope location on the community structure of soil fauna in Eucalyptus grandis plantation, an investigation was made on the soil fauna in 3 E. grandis plantations at different slope locations in the hilly area of Sichuan Province from January to October 2009. A total of 39,2762 individuals were observed, belonging to 146 groups, 7 phyla, 16 classes, and 31 orders. The community composition, trophic group, diversity, and seasonal dynamics of soil fauna in the plantations all varied with slope. The abundance of macro-fauna, xeric meso- and micro-fauna, saprophagous macro-fauna, and omnivorous xeric meso- and micro-fauna increased with the decrease of slope, indicating that soil fauna had sensitive responses to the soil environmental factors affected by slope. Significant differences in the diversity of soil saprophagous macro-fauna and hygrophilous meso- and micro-fauna were observed at different slope locations, suggesting that these two faunal groups could be used as the indicators of the habitat heterogeneity of E. grandis plantations at different slope. Overall, slope location had definite effects on the community structure and distribution of soil fauna in the E. grandis plantations, but the effects were not statistically significant.

Soil shapes community structure through fire.

Science.gov (United States)

Ojeda, Fernando; Pausas, Juli G; Verdú, Miguel

2010-07-01

Recurrent wildfires constitute a major selecting force in shaping the structure of plant communities. At the regional scale, fire favours phenotypic and phylogenetic clustering in Mediterranean woody plant communities. Nevertheless, the incidence of fire within a fire-prone region may present strong variations at the local, landscape scale. This study tests the prediction that woody communities on acid, nutrient-poor soils should exhibit more pronounced phenotypic and phylogenetic clustering patterns than woody communities on fertile soils, as a consequence of their higher flammability and, hence, presumably higher propensity to recurrent fire. Results confirm the predictions and show that habitat filtering driven by fire may be detected even in local communities from an already fire-filtered regional flora. They also provide a new perspective from which to consider a preponderant role of fire as a key evolutionary force in acid, infertile Mediterranean heathlands.

Dynamic Effects of Biochar on the Bacterial Community Structure in Soil Contaminated with Polycyclic Aromatic Hydrocarbons.

Science.gov (United States)

Song, Yang; Bian, Yongrong; Wang, Fang; Xu, Min; Ni, Ni; Yang, Xinglun; Gu, Chenggang; Jiang, Xin

2017-08-16

Amending soil with biochar is an effective soil remediation strategy for organic contaminants. This study investigated the dynamic effects of wheat straw biochar on the bacterial community structure during remediation by high-throughput sequencing. The wheat straw biochar amended into the soil significantly reduced the bioavailability and toxicity of polycyclic aromatic hydrocarbons (PAHs). Biochar amendment helped to maintain the bacterial diversity in the PAH-contaminated soil. The relationship between the immobilization of PAHs and the soil bacterial diversity fit a quadratic model. Before week 12 of the incubation, the incubation time was the main factor contributing to the changes in the soil bacterial community structure. However, biochar greatly affected the bacterial community structure after 12 weeks of amendment, and the effects were dependent upon the biochar type. Amendment with biochar mainly facilitated the growth of rare bacterial genera (relative abundance of 0.01-1%) in the studied soil. Therefore, the application of wheat straw biochar into PAH-contaminated soil can reduce the environmental risks of PAHs and benefit the soil microbial ecology.

Change in fish community structure in the Barents Sea.

Directory of Open Access Journals (Sweden)

Michaela Aschan

Full Text Available Change in oceanographic conditions causes structural alterations in marine fish communities, but this effect may go undetected as most monitoring programs until recently mainly have focused on oceanography and commercial species rather than on whole ecosystems. In this paper, the objective is to describe the spatial and temporal changes in the Barents Sea fish community in the period 1992-2004 while taking into consideration the observed abundance and biodiversity patterns for all 82 observed fish species. We found that the spatial structure of the Barents Sea fish community was determined by abiotic factors such as temperature and depth. The observed species clustered into a deep assemblage, a warm water southern assemblage, both associated with Atlantic water, and a cold water north-eastern assemblage associated with mixed water. The latitude of the cold water NE and warm water S assemblages varied from year to year, but no obvious northward migration was observed over time. In the period 1996-1999 we observed a significant reduction in total fish biomass, abundance, mean fish weight, and a change in community structure including an increase in the pelagic/demersal ratio. This change in community structure is probably due to extremely cold conditions in 1996 impacting on a fish community exposed to historically high fishing rates. After 1999 the fish community variables such as biomass, abundance, mean weight, P/D ratio as well as community composition did not return to levels of the early 90s, although fishing pressure and climatic conditions returned to earlier levels.

Support for Communities affected by Mining in Canada and around ...

International Development Research Centre (IDRC) Digital Library (Canada)

Support for Communities affected by Mining in Canada and around the Globe. Founded in 1999, Mining Watch Canada (MWC) is a coalition of 18 Canadian environmental, social justice, church, first nations and labour organizations. MWC addresses the need for a coordinated public interest response to the risks posed by ...

How has the economic downturn affected communities and implementation of science-based prevention in the randomized trial of communities that care?

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Kuklinski, Margaret R; Hawkins, J David; Plotnick, Robert D; Abbott, Robert D; Reid, Carolina K

2013-06-01

This study examined implications of the economic downturn that began in December 2007 for the Community Youth Development Study (CYDS), a longitudinal randomized controlled trial of the Communities That Care (CTC) prevention system. The downturn had the potential to affect the internal validity of the CYDS research design and implementation of science-based prevention in study communities. We used archival economic indicators and community key leader reports of economic conditions to assess the extent of the economic downturn in CYDS communities and potential internal validity threats. We also examined whether stronger economic downturn effects were associated with a decline in science-based prevention implementation. Economic indicators suggested the downturn affected CYDS communities to different degrees. We found no evidence of systematic differences in downturn effects in CTC compared to control communities that would threaten internal validity of the randomized trial. The Community Economic Problems scale was a reliable measure of community economic conditions, and it showed criterion validity in relation to several objective economic indicators. CTC coalitions continued to implement science-based prevention to a significantly greater degree than control coalitions 2 years after the downturn began. However, CTC implementation levels declined to some extent as unemployment, the percentage of students qualifying for free lunch, and community economic problems worsened. Control coalition implementation levels were not related to economic conditions before or after the downturn, but mean implementation levels of science-based prevention were also relatively low in both periods.

[Phytoplankton's community structure and its relationships with environmental factors in the rivers of Tongling City, Anhui Province of East China in winter].

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Wang, Li; Wei, Wei; Zhou, Ping; Li, Yang; Sun, Qing-Ye

2013-01-01

Tongling is one of the main non-ferrous metal mining areas in China, and the biodiversity in the river ecosystem of this area is seriously affected by heavy metals as a result of mining activities. In the winter in 2010, an investigation was conducted on the community structure of phytoplankton and its relationships with environmental factors in the main sections of the rivers in Tongling. A total of 203 phytoplankton species were identified, belonging to 96 genera and 8 phyla. The community structure of the phytoplankton differed obviously in different river sections, but the communities were all dominated by Bacillariophyta, Chlorophyta and Cyanophyta. The phytoplankton abundance ranged from 9.1 x 10(3) to 6.5 x 10(7) cells x L(-1), and the quantity of the phytoplankton in the river sections directly carried with mining waste water was significantly low. The Shannon index of the phytoplankton community at different sampling sites ranged from 0 to 3.45, with a significant discrepancy in different river sections. There existed significant correlations between the density and group number of phytoplankton and the COD(Cr) and cadmium, copper and zinc concentrations in the rivers, and the concentrations of river total nitrogen, NH4(+)-N, NO3(-)-N, and copper, COD(Cr) and pH were the main environmental variables affecting the phytoplankton' s community structure and its spatial distribution. Although the nutritional status of the river waters had greater effects on the community structure of phytoplankton, the effects of the heavy metals there from mining enterprises could not be neglected.

Functional and phylogenetic structure of island bird communities.

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Si, Xingfeng; Cadotte, Marc W; Zeng, Di; Baselga, Andrés; Zhao, Yuhao; Li, Jiaqi; Wu, Yiru; Wang, Siyu; Ding, Ping

2017-05-01

Biodiversity change in anthropogenically transformed habitats is often nonrandom, yet the nature and importance of the different mechanisms shaping community structure are unclear. Here, we extend the classic Theory of Island Biogeography (TIB) to account for nonrandom processes by incorporating species traits and phylogenetic relationships into a study of faunal relaxation following habitat loss and fragmentation. Two possible mechanisms can create nonrandom community patterns on fragment islands. First, small and isolated islands might consist of similar or closely related species because they are environmentally homogeneous or select for certain shared traits, such as dispersal ability. Alternatively, communities on small islands might contain more dissimilar or distantly related species than on large islands because limited space and resource availability result in greater competitive exclusion among species with high niche overlap. Breeding birds were surveyed on 36 islands and two mainland sites annually from 2010 to 2014 in the Thousand Island Lake region, China. We assessed community structure of breeding birds on these subtropical land-bridge islands by integrating species' trait and evolutionary distances. We additionally analysed habitat heterogeneity and variance in size ratios to distinguish biotic and abiotic processes of community assembly. Results showed that functional-phylogenetic diversity increased with island area, and decreased with isolation. Bird communities on the mainland were more diverse and generally less clustered than island bird communities and not different than randomly assembled communities. Bird communities on islands tend to be functionally similar and phylogenetically clustered, especially on small and isolated islands. The nonrandom decline in species diversity and change in bird community structure with island area and isolation, along with the relatively homogeneous habitats on small islands, support the environmental

Flooding greatly affects the diversity of arbuscular mycorrhizal fungi communities in the roots of wetland plants.

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Yutao Wang

Full Text Available The communities of arbuscular mycorrhizal fungi (AMF colonizing the roots of three mangrove species were characterized along a tidal gradient in a mangrove swamp. A fragment, designated SSU-ITS-LSU, including part of the small subunit (SSU, the entire internal transcribed spacer (ITS and part of the large subunit (LSU of rDNA from samples of AMF-colonized roots was amplified, cloned and sequenced using AMF-specific primers. Similar levels of AMF diversity to those observed in terrestrial ecosystems were detected in the roots, indicating that the communities of AMF in wetland ecosystems are not necessarily low in diversity. In total, 761 Glomeromycota sequences were obtained, which grouped, according to phylogenetic analysis using the SSU-ITS-LSU fragment, into 23 phylotypes, 22 of which belonged to Glomeraceae and one to Acaulosporaceae. The results indicate that flooding plays an important role in AMF diversity, and its effects appear to depend on the degree (duration of flooding. Both host species and tide level affected community structure of AMF, indicating the presence of habitat and host species preferences.

Covariance, correlation matrix, and the multiscale community structure of networks.

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Shen, Hua-Wei; Cheng, Xue-Qi; Fang, Bin-Xing

2010-07-01

Empirical studies show that real world networks often exhibit multiple scales of topological descriptions. However, it is still an open problem how to identify the intrinsic multiple scales of networks. In this paper, we consider detecting the multiscale community structure of network from the perspective of dimension reduction. According to this perspective, a covariance matrix of network is defined to uncover the multiscale community structure through the translation and rotation transformations. It is proved that the covariance matrix is the unbiased version of the well-known modularity matrix. We then point out that the translation and rotation transformations fail to deal with the heterogeneous network, which is very common in nature and society. To address this problem, a correlation matrix is proposed through introducing the rescaling transformation into the covariance matrix. Extensive tests on real world and artificial networks demonstrate that the correlation matrix significantly outperforms the covariance matrix, identically the modularity matrix, as regards identifying the multiscale community structure of network. This work provides a novel perspective to the identification of community structure and thus various dimension reduction methods might be used for the identification of community structure. Through introducing the correlation matrix, we further conclude that the rescaling transformation is crucial to identify the multiscale community structure of network, as well as the translation and rotation transformations.

Community structures and role detection in music networks

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Teitelbaum, T.; Balenzuela, P.; Cano, P.; Buldú, Javier M.

2008-12-01

We analyze the existence of community structures in two different social networks using data obtained from similarity and collaborative features between musical artists. Our analysis reveals some characteristic organizational patterns and provides information about the driving forces behind the growth of the networks. In the similarity network, we find a strong correlation between clusters of artists and musical genres. On the other hand, the collaboration network shows two different kinds of communities: rather small structures related to music bands and geographic zones, and much bigger communities built upon collaborative clusters with a high number of participants related through the period the artists were active. Finally, we detect the leading artists inside their corresponding communities and analyze their roles in the network by looking at a few topological properties of the nodes.

Investigation of microbial community structure in constructed mangrove microcosms receiving wastewater-borne polycyclic aromatic hydrocarbons (PAHs) and polybrominated diphenyl ethers (PBDEs)

International Nuclear Information System (INIS)

Wang, Ya-fen; Wu, Yan; Pi, Na; Tam, Nora Fung-yee

2014-01-01

The study aims to examine relationships between microbial community structure and mixed pollutants of polycyclic aromatic hydrocarbons (PAHs) and polybrominated diphenyl ethers (PBDEs) in constructed wetland microcosms, planted with Excoecaria agallocha or Kandelia obovata, two common mangrove plant species, and under two tidal regimes, everyday tidal (Te) and no tidal flooding (Tn). Results showed both microbial community structure and the retained amounts of pollutants were significantly determined by tidal regime, while the effect of plant species was small. Higher amounts of PAHs but lower amounts of PBDEs were always retained in sediments under Te than Tn regimes. Accordingly, temporal and vertical distributions of microbial community structure differed greatly between the two tidal regimes. Redundancy analysis further revealed significant correlation between a subgroup of the mixed PAHs and PBDEs with variation in microbial community structure. The findings will help to propose specific strategies to improve the bioremediation efficiency of constructed wetland. - Highlights: • We found synchronous degradation of PAHs and PBDEs in constructed mangrove microcosms. • Retained amounts of PAHs and PBDEs were determined mainly by tidal regime. • Tidal regime in turn significantly determined microbial community structure. • Variations of microbial EL-FAME profiles were more affected by PBDEs than PAHs. • Bap and BDE-154 were two most influential pollutants on microbial community structure. - Sedimentary microbial community structure was significantly determined by tidal regime, which in turn determined retained amounts of PAHs and PBDEs in constructed mangrove microcosms

Investigating Effects of Invasive Species on Plant Community Structure

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Franklin, Wilfred

2008-01-01

In this article, the author presents a field study project that explores factors influencing forest community structure and lifts the veil off of "plant blindness." This ecological study consists of three laboratories: (1) preliminary field trip to the study site; (2) plant survey; and (3) analyzing plant community structure with descriptive…

Community Structural Instability, Anomie, Imitation and Adolescent Suicidal Behavior

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Thorlindsson, Thorolfur; Bernburg, Jon Gunnar

2009-01-01

The current study examines the contextual effects of community structural characteristics, as well as the mediating role of key social mechanisms, on youth suicidal behavior in Iceland. We argue that the contextual influence of community structural instability on youth suicidal behavior should be mediated by weak attachment to social norms and…

Disentangling the influences of habitat structure and limnological predictors on stream fish communities of a coastal basin, southeastern Brazil

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Fabio Cop Ferreira

Full Text Available In stream environments habitat structure and limnological factors interact regulating patterns of energy and material transfer and affecting fish communities. In the coastal basins of Southeastern Brazil, limnological and structural characteristics differ between clear and blackwaters streams. The former have a diversity of substrate types, higher water velocities, and lower water conductivity, while the latter have sandy substrate, tea-colored and acidic waters, and low water velocities. In this study, we verified the relative importance of habitat structure and limnological variables in predicting patterns of variation in stream fish communities. Eight first to third order streams were sampled in the coastal plain of Itanhaém River basin. We captured 34 fish species and verified that community structure was influenced by physical habitat and limnology, being the former more important. A fraction of the variation could not be totally decomposed, and it was assigned to the joint influence of limnology and habitat structure. Some species that were restricted to blackwater streams, may have physiological and behavioral adaptations to deal with the lower pH levels. When we examined only the clearwater streams, all the explained variation in fish community composition was assigned to structural factors, which express specific preferences for different types of habitats.

Epidemic spreading in weighted scale-free networks with community structure

International Nuclear Information System (INIS)

Chu, Xiangwei; Guan, Jihong; Zhang, Zhongzhi; Zhou, Shuigeng

2009-01-01

Many empirical studies reveal that the weights and community structure are ubiquitous in various natural and artificial networks. In this paper, based on the SI disease model, we investigate the epidemic spreading in weighted scale-free networks with community structure. Two exponents, α and β, are introduced to weight the internal edges and external edges, respectively; and a tunable probability parameter q is also introduced to adjust the strength of community structure. We find the external weighting exponent β plays a much more important role in slackening the epidemic spreading and reducing the danger brought by the epidemic than the internal weighting exponent α. Moreover, a novel result we find is that the strong community structure is no longer helpful for slackening the danger brought by the epidemic in the weighted cases. In addition, we show the hierarchical dynamics of the epidemic spreading in the weighted scale-free networks with communities which is also displayed in the famous BA scale-free networks

Detecting highly overlapping community structure by greedy clique expansion

OpenAIRE

Lee, Conrad; Reid, Fergal; McDaid, Aaron; Hurley, Neil

2010-01-01

In complex networks it is common for each node to belong to several communities, implying a highly overlapping community structure. Recent advances in benchmarking indicate that existing community assignment algorithms that are capable of detecting overlapping communities perform well only when the extent of community overlap is kept to modest levels. To overcome this limitation, we introduce a new community assignment algorithm called Greedy Clique Expansion (GCE). The algorithm identifies d...

Factors Affecting Re-usage Intentions of Virtual Communities Supporting Cosmetic Products

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Jhong-Min Yang

2017-01-01

Full Text Available Aim/Purpose: This study uses a cosmetic virtual community (VC as the research context and the UTAUT model as the theoretical structure aim to explore factors affecting the re-usage intentions of VC members. Background: The Internet use rate of VC was up to 50%, thereby implying that VC gained the attention of Internet users. Therefore, operating a VC will be an effective way to communicate with customers. However, to maintain an existing member is more efficient than creating a new one. As such, understanding determinants of VC members’ re-use intentions becomes important for firms. Methodology: Through an online survey, 276 valid responses were gathered. The collected data were examined by performing confirmatory factor analysis, structural equation modelling procedures, as well as the moderator analysis. Contribution: This study shows the importance in the context of online cosmetics-related VC, which was rarely explored before. We provide issues for future research, despite the accumulated academic literature related to UTAUT and VC. Findings: Results show that only performance expectancy and social influence significantly affecting re-usage intentions and only gender has moderating effects on the path from performance expectancy to VC re-use intention and from trust to VC re-use intention. Recommendations for Practitioners\t: This study found that users emphasized performance expectancy most of all. A cosmetic product-related VC should introduce products abundantly, offer useful information, and help people accomplish tasks quickly and productively. Recommendation for Researchers: Future researchers may use our findings to conduct further positivist research in the area of social influence using different subjects and research contexts.

Sulfamethoxazole and COD increase abundance of sulfonamide resistance genes and change bacterial community structures within sequencing batch reactors.

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Guo, Xueping; Pang, Weihai; Dou, Chunling; Yin, Daqiang

2017-05-01

The abundant microbial community in biological treatment processes in wastewater treatment plants (WWTPs) may potentially enhance the horizontal gene transfer of antibiotic resistance genes with the presence of antibiotics. A lab-scale sequencing batch reactor was designed to investigate response of sulfonamide resistance genes (sulI, sulII) and bacterial communities to various concentrations of sulfamethoxazole (SMX) and chemical oxygen demand (COD) of wastewater. The SMX concentrations (0.001 mg/L, 0.1 mg/L and 10 mg/L) decreased with treatment time and higher SMX level was more difficult to remove. The presence of SMX also significantly reduced the removal efficiency of ammonia nitrogen, affecting the normal function of WWTPs. All three concentrations of SMX raised both sulI and sulII genes with higher concentrations exhibiting greater increases. The abundance of sul genes was positive correlated with treatment time and followed the second-order reaction kinetic model. Interestingly, these two genes have rather similar activity. SulI and sulII gene abundance also performed similar response to COD. Simpson index and Shannon-Weiner index did not show changes in the microbial community diversity. However, the 16S rRNA gene cloning and sequencing results showed the bacterial community structures varied during different stages. The results demonstrated that influent antibiotics into WWTPs may facilitate selection of ARGs and affect the wastewater conventional treatment as well as the bacteria community structures. Copyright © 2017 Elsevier Ltd. All rights reserved.

Facility and market factors affecting transitions from nursing home to community.

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Arling, Greg; Abrahamson, Kathleen A; Cooke, Valerie; Kane, Robert L; Lewis, Teresa

2011-09-01

Research into nursing home transitions has given limited attention to the facility or community contexts. To identify facility and market factors affecting transitions of nursing home residents back to the community. Multilevel models were used to estimate effects of facility and market factors on facility-level community discharge rates after controlling for resident demographic, health, and functional conditions. Facility discharge rates were adjusted using Empirical Bayes estimation. Annual cohort of first-time admissions (N=24,648) to 378 Minnesota nursing facilities in 75 nursing home markets from July 2005 to June 2006. Community discharge within 90 days of admission; facility occupancy, payer mix, ownership, case-mix acuity, size, admissions from hospitals, nurse staffing level, and proportion of admissions preferring or having support to return to the community; and nursing market population size, average occupancy, market concentration, and availability of home and community-based services. Rates of community discharge (Empirical Bayes residual) were highest in facilities with more residents preferring community discharge, more Medicare days, higher nurse staffing levels, and higher occupancy. In addition, facilities had higher community discharge rates if they were located in markets with a greater ratio of home and community-based services recipients to nursing home residents and with larger populations. State Medicaid programs should undertake system-level interventions that encourage nursing facilities to reduce unused bed capacity, balance the mix of payers, invest in nurse staffing, and take other steps to promote community discharges. In addition, states should increase home and community-based services, particularly in markets with low community discharge rates.

Historical changes in the structure and functioning of the benthic community in the lagoon of Venice

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Pranovi, Fabio; Da Ponte, Filippo; Torricelli, Patrizia

2008-03-01

One of the main challenges in environmental management is how to manage the dynamics of natural environments. In this context, having information about historical changes of the structure of the biological communities could represent a useful tool to improve management strategies, contributing to refine the policy objectives, since it gives reference states with which to compare the present. The Venice lagoon represents an interesting case study, since it is a highly dynamic, but sensitive, environment which requires the adoption of prudent management. In its recent history the lagoon ecosystem has been exposed to different kinds of disturbance, from the discharge of pollutants and nutrients, to the invasion of alien species and the exploitation of its biological resources by using highly impacting fishing gears. The analysis of available data about the macro-benthic community, from 1935 to 2004, allows the description of changes of the community structure over almost 70 years, showing a sharp decrease in its diversity. In order to obtain information about its functioning, it is necessary to know how these changes have affected processes at the community and system level. In shallow water ecosystems, as the control is mainly due to the benthic compartment, variations in the structure of the benthic community can induce modifications in processes at different hierarchical levels. The trophic structure analysis has revealed major changes during the period; from a well-assorted structure in 1935, to an herbivore-detritivore dominated one in the 1990s, and finally to a filter feeder dominated structure during the last decade. This has produced variations in the secondary production and it has induced modifications in the type of the ecosystem control. These changes are discussed in the light of the dynamics of the main driving forces.

Benthic infaunal community structuring in an acidified tropical estuarine system.

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Hossain, M Belal; Marshall, David J

2014-01-01

Recent studies suggest that increasing ocean acidification (OA) should have strong direct and indirect influences on marine invertebrates. While most theory and application for OA is based on relatively physically-stable oceanic ecological systems, less is known about the effects of acidification on nearshore and estuarine systems. Here, we investigated the structuring of a benthic infaunal community in a tropical estuarine system, along a steep salinity and pH gradient, arising largely from acid-sulphate groundwater inflows (Sungai Brunei Estuary, Borneo, July 2011- June 2012). Preliminary data indicate that sediment pore-water salinity (range: 8.07 - 29.6 psu) declined towards the mainland in correspondence with the above-sediment estuarine water salinity (range: 3.58 - 31.2 psu), whereas the pore-water pH (range: 6.47- 7.72) was generally lower and less variable than the estuarine water pH (range: 5.78- 8.3), along the estuary. Of the thirty six species (taxa) recorded, the polychaetes Neanthes sp., Onuphis conchylega, Nereididae sp. and the amphipod Corophiidae sp., were numerically dominant. Calcified microcrustaceans (e.g., Cyclopoida sp. and Corophiidae sp.) were abundant at all stations and there was no clear distinction in distribution pattern along the estuarine between calcified and non-calcified groups. Species richness increased seawards, though abundance (density) showed no distinct directional trend. Diversity indices were generally positively correlated (Spearman's rank correlation) with salinity and pH (p 0.05). Three faunistic assemblages were distinguished: (1) nereid-cyclopoid-sabellid, (2) corophiid-capitellid and (3) onuphid- nereid-capitellid. These respectively associated with lower salinity/pH and a muddy bottom, low salinity/pH and a sandy bottom, and high salinity/pH and a sandy bottom. However, CCA suggested that species distribution and community structuring is more strongly influenced by sediment particle characteristics than by the

Spatial variation of phytoplankton community structure in Daya Bay, China.

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Jiang, Zhao-Yu; Wang, You-Shao; Cheng, Hao; Zhang, Jian-Dong; Fei, Jiao

2015-10-01

Daya Bay is one of the largest and most important gulfs in the southern coast of China, in the northern part of the South China Sea. The phylogenetic diversity and spatial distribution of phytoplankton from the Daya Bay surface water and the relationship with the in situ water environment were investigated by the clone library of the large subunit of ribulose-1, 5-bisphosphate carboxylase (rbcL) gene. The dominant species of phytoplankton were diatoms and eustigmatophytes, which accounted for 81.9 % of all the clones of the rbcL genes. Prymnesiophytes were widely spread and wide varieties lived in Daya Bay, whereas the quantity was limited. The community structure of phytoplankton was shaped by pH and salinity and the concentration of silicate, phosphorus and nitrite. The phytoplankton biomass was significantly positively affected by phosphorus and nitrite but negatively by salinity and pH. Therefore, the phytoplankton distribution and biomass from Daya Bay were doubly affected by anthropic activities and natural factors.

Community structure informs species geographic distributions

KAUST Repository

Montesinos-Navarro, Alicia; Estrada, Alba; Font, Xavier; Matias, Miguel G.; Meireles, Catarina; Mendoza, Manuel; Honrado, Joao P.; Prasad, Hari D.; Vicente, Joana R.; Early, Regan

2018-01-01

spatial resolution. However, survival of individuals is determined by processes that happen at small spatial scales. The relative abundance of coexisting species (i.e. 'community structure') reflects assembly processes occurring at small scales

Error and attack tolerance of synchronization in Hindmarsh–Rose neural networks with community structure

International Nuclear Information System (INIS)

Li, Chun-Hsien; Yang, Suh-Yuh

2014-01-01

Synchronization is one of the most important features observed in large-scale complex networks of interacting dynamical systems. As is well known, there is a close relation between the network topology and the network synchronizability. Using the coupled Hindmarsh–Rose neurons with community structure as a model network, in this paper we explore how failures of the nodes due to random errors or intentional attacks affect the synchronizability of community networks. The intentional attacks are realized by removing a fraction of the nodes with high values in some centrality measure such as the centralities of degree, eigenvector, betweenness and closeness. According to the master stability function method, we employ the algebraic connectivity of the considered community network as an indicator to examine the network synchronizability. Numerical evidences show that the node failure strategy based on the betweenness centrality has the most influence on the synchronizability of community networks. With this node failure strategy for a given network with a fixed number of communities, we find that the larger the degree of communities, the worse the network synchronizability; however, for a given network with a fixed degree of communities, we observe that the more the number of communities, the better the network synchronizability.

Artificial Light at Night Affects Organism Flux across Ecosystem Boundaries and Drives Community Structure in the Recipient Ecosystem

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Alessandro Manfrin

2017-10-01

Full Text Available Artificial light at night (ALAN is a widespread alteration of the natural environment that can affect the functioning of ecosystems. ALAN can change the movement patterns of freshwater animals that move into the adjacent riparian and terrestrial ecosystems, but the implications for local riparian consumers that rely on these subsidies are still unexplored. We conducted a 2-year field experiment to quantify changes of freshwater-terrestrial linkages by installing streetlights in a previously light-naïve riparian area adjacent to an agricultural drainage ditch. We compared the abundance and community composition of emerging aquatic insects, flying insects, and ground-dwelling arthropods with an unlit control site. Comparisons were made within and between years using two-way generalized least squares (GLS model and a BACI design (Before-After Control-Impact. Aquatic insect emergence, the proportion of flying insects that were aquatic in origin, and the total abundance of flying insects all increased in the ALAN-illuminated area. The abundance of several night-active ground-dwelling predators (Pachygnatha clercki, Trochosa sp., Opiliones increased under ALAN and their activity was extended into the day. Conversely, the abundance of nocturnal ground beetles (Carabidae decreased under ALAN. The changes in composition of riparian predator and scavenger communities suggest that the increase in aquatic-to-terrestrial subsidy flux may cascade through the riparian food web. The work is among the first studies to experimentally manipulate ALAN using a large-scale field experiment, and provides evidence that ALAN can affect processes that link adjacent ecosystems. Given the large number of streetlights that are installed along shorelines of freshwater bodies throughout the globe, the effects could be widespread and represent an underestimated source of impairment for both aquatic and riparian systems.

Agricultural factors affecting Fusarium communities in wheat kernels.

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Karlsson, Ida; Friberg, Hanna; Kolseth, Anna-Karin; Steinberg, Christian; Persson, Paula

2017-07-03

Fusarium head blight (FHB) is a devastating disease of cereals caused by Fusarium fungi. The disease is of great economic importance especially owing to reduced grain quality due to contamination by a range of mycotoxins produced by Fusarium. Disease control and prediction is difficult because of the many Fusarium species associated with FHB. Different species may respond differently to control methods and can have both competitive and synergistic interactions. Therefore, it is important to understand how agricultural practices affect Fusarium at the community level. Lower levels of Fusarium mycotoxin contamination of organically produced cereals compared with conventionally produced have been reported, but the causes of these differences are not well understood. The aim of our study was to investigate the effect of agricultural factors on Fusarium abundance and community composition in different cropping systems. Winter wheat kernels were collected from 18 organically and conventionally cultivated fields in Sweden, paired based on their geographical distance and the wheat cultivar grown. We characterised the Fusarium community in harvested wheat kernels using 454 sequencing of translation elongation factor 1-α amplicons. In addition, we quantified Fusarium spp. using real-time PCR to reveal differences in biomass between fields. We identified 12 Fusarium operational taxonomic units (OTUs) with a median of 4.5 OTUs per field. Fusarium graminearum was the most abundant species, while F. avenaceum had the highest occurrence. The abundance of Fusarium spp. ranged two orders of magnitude between fields. Two pairs of Fusarium species co-occurred between fields: F. poae with F. tricinctum and F. culmorum with F. sporotrichoides. We could not detect any difference in Fusarium communities between the organic and conventional systems. However, agricultural intensity, measured as the number of pesticide applications and the amount of nitrogen fertiliser applied, had an

Type and amount of organic amendments affect enhanced biogenic methane production from coal and microbial community structure

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Davis, Katherine J.; Lu, Shipeng; Barnhart, Elliott P.; Parker, Albert E.; Fields, Matthew W.; Gerlach, Robin

2018-01-01

Slow rates of coal-to-methane conversion limit biogenic methane production from coalbeds. This study demonstrates that rates of coal-to-methane conversion can be increased by the addition of small amounts of organic amendments. Algae, cyanobacteria, yeast cells, and granulated yeast extract were tested at two concentrations (0.1 and 0.5 g/L), and similar increases in total methane produced and methane production rates were observed for all amendments at a given concentration. In 0.1 g/L amended systems, the amount of carbon converted to methane minus the amount produced in coal only systems exceeded the amount of carbon added in the form of amendment, suggesting enhanced coal-to-methane conversion through amendment addition. The amount of methane produced in the 0.5 g/L amended systems did not exceed the amount of carbon added. While the archaeal communities did not vary significantly, the bacterial populations appeared to be strongly influenced by the presence of coal when 0.1 g/L of amendment was added; at an amendment concentration of 0.5 g/L the bacterial community composition appeared to be affected most strongly by the amendment type. Overall, the results suggest that small amounts of amendment are not only sufficient but possibly advantageous if faster in situcoal-to-methane production is to be promoted.

The relative importance of seed competition, resource competition and perturbations on community structure

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K. Bohn

2011-05-01

Full Text Available While the regional climate is the primary selection pressure for whether a plant strategy can survive, however, competitive interactions strongly affect the relative abundances of plant strategies within communities. Here, we investigate the relative importance of competition and perturbations on the development of vegetation community structure. To do so, we develop DIVE (Dynamics and Interactions of VEgetation, a simple general model that links plant strategies to their competitive dynamics, using growth and reproduction characteristics that emerge from climatic constraints. The model calculates population dynamics based on establishment, mortality, invasion and exclusion in the presence of different strengths of perturbations, seed and resource competition. The highest levels of diversity were found in simulations without competition as long as mortality is not too high. However, reasonable successional dynamics were only achieved when resource competition is considered. Under high levels of competition, intermediate levels of perturbations were required to obtain coexistence. Since succession and coexistence are observed in plant communities, we conclude that the DIVE model with competition and intermediate levels of perturbation represents an adequate way to model population dynamics. Because of the simplicity and generality of DIVE, it could be used to understand vegetation structure and functioning at the global scale and the response of vegetation to global change.

Light structures phototroph, bacterial and fungal communities at the soil surface.

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Lawrence O Davies

Full Text Available The upper few millimeters of soil harbour photosynthetic microbial communities that are structurally distinct from those of underlying bulk soil due to the presence of light. Previous studies in arid zones have demonstrated functional importance of these communities in reducing soil erosion, and enhancing carbon and nitrogen fixation. Despite being widely distributed, comparative understanding of the biodiversity of the soil surface and underlying soil is lacking, particularly in temperate zones. We investigated the establishment of soil surface communities on pasture soil in microcosms exposed to light or dark conditions, focusing on changes in phototroph, bacterial and fungal communities at the soil surface (0-3 mm and bulk soil (3-12 mm using ribosomal marker gene analyses. Microbial community structure changed with time and structurally similar phototrophic communities were found at the soil surface and in bulk soil in the light exposed microcosms suggesting that light can influence phototroph community structure even in the underlying bulk soil. 454 pyrosequencing showed a significant selection for diazotrophic cyanobacteria such as Nostoc punctiforme and Anabaena spp., in addition to the green alga Scenedesmus obliquus. The soil surface also harboured distinct heterotrophic bacterial and fungal communities in the presence of light, in particular, the selection for the phylum Firmicutes. However, these light driven changes in bacterial community structure did not extend to the underlying soil suggesting a discrete zone of influence, analogous to the rhizosphere.

A spectral method to detect community structure based on distance modularity matrix

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Yang, Jin-Xuan; Zhang, Xiao-Dong

2017-08-01

There are many community organizations in social and biological networks. How to identify these community structure in complex networks has become a hot issue. In this paper, an algorithm to detect community structure of networks is proposed by using spectra of distance modularity matrix. The proposed algorithm focuses on the distance of vertices within communities, rather than the most weakly connected vertex pairs or number of edges between communities. The experimental results show that our method achieves better effectiveness to identify community structure for a variety of real-world networks and computer generated networks with a little more time-consumption.

Loving transgressions: Queer of color bodies, affective ties, transformative community.

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Carrillo Rowe, Aimee; Royster, Francesca T

2017-07-03

This introductory article considers the importance of queer woman of color theorizations of affect in thinking more fully the recent interdisciplinary turn to affect. The affective turn has vitally invited culture and feminist critics to interrogate emotion beyond the individual to examine the political and cultural production of emotion. Even as women of color are often associated with excessive affect, the theoretical contributions women of color make to the field of affect studies are often overlooked. Our introduction and this special issue more broadly examine how this solipsism shapes projects invested in critical knowledge production, as well as the stakes of centering a queer woman of color genealogy. For instance, we argue for the importance of retaining U.S. third-world feminist concepts-like interpellation, oppositional consciousness, and the generative force of negative affects-even as they fall out of favor within affect studies. Centering theory that emerges from the vexed spaces of queer women of color lived experiences generates a vital interdisciplinary conversation that contributes to the ongoing political task of mobilizing affect for social action as a critical praxis. In the articles that follow we see this critical praxis at work in the form of community organizing, music, poetry, and performance art.

How mammalian predation contributes to tropical tree community structure.

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Paine, C E Timothy; Beck, Harald; Terborgh, John

2016-12-01

The recruitment of seedlings from seeds is the key demographic transition for rain forest trees. Though tropical forest mammals are known to consume many seeds, their effects on tree community structure remain little known. To evaluate their effects, we monitored 8,000 seeds of 24 tree species using exclosure cages that were selectively permeable to three size classes of mammals for up to 4.4 years. Small and medium-bodied mammals removed many more seeds than did large mammals, and they alone generated beta diversity and negative density dependence, whereas all mammals reduced diversity and shaped local species composition. Thus, small and medium-bodied mammals more strongly contributed to community structure and promoted species coexistence than did large mammals. Given that seedling recruitment is seed limited for most species, alterations to the composition of the community of mammalian seed predators is expected to have long-term consequences for tree community structure in tropical forests. © 2016 by the Ecological Society of America.

Invasive lionfish had no measurable effect on prey fish community structure across the Belizean Barrier Reef.

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Hackerott, Serena; Valdivia, Abel; Cox, Courtney E; Silbiger, Nyssa J; Bruno, John F

2017-01-01

Invasive lionfish are assumed to significantly affect Caribbean reef fish communities. However, evidence of lionfish effects on native reef fishes is based on uncontrolled observational studies or small-scale, unrepresentative experiments, with findings ranging from no effect to large effects on prey density and richness. Moreover, whether lionfish affect populations and communities of native reef fishes at larger, management-relevant scales is unknown. The purpose of this study was to assess the effects of lionfish on coral reef prey fish communities in a natural complex reef system. We quantified lionfish and the density, richness, and composition of native prey fishes (0-10 cm total length) at sixteen reefs along ∼250 km of the Belize Barrier Reef from 2009 to 2013. Lionfish invaded our study sites during this four-year longitudinal study, thus our sampling included fish community structure before and after our sites were invaded, i.e., we employed a modified BACI design. We found no evidence that lionfish measurably affected the density, richness, or composition of prey fishes. It is possible that higher lionfish densities are necessary to detect an effect of lionfish on prey populations at this relatively large spatial scale. Alternatively, negative effects of lionfish on prey could be small, essentially undetectable, and ecologically insignificant at our study sites. Other factors that influence the dynamics of reef fish populations including reef complexity, resource availability, recruitment, predation, and fishing could swamp any effects of lionfish on prey populations.

Invasive lionfish had no measurable effect on prey fish community structure across the Belizean Barrier Reef

Directory of Open Access Journals (Sweden)

Serena Hackerott

2017-05-01

Full Text Available Invasive lionfish are assumed to significantly affect Caribbean reef fish communities. However, evidence of lionfish effects on native reef fishes is based on uncontrolled observational studies or small-scale, unrepresentative experiments, with findings ranging from no effect to large effects on prey density and richness. Moreover, whether lionfish affect populations and communities of native reef fishes at larger, management-relevant scales is unknown. The purpose of this study was to assess the effects of lionfish on coral reef prey fish communities in a natural complex reef system. We quantified lionfish and the density, richness, and composition of native prey fishes (0–10 cm total length at sixteen reefs along ∼250 km of the Belize Barrier Reef from 2009 to 2013. Lionfish invaded our study sites during this four-year longitudinal study, thus our sampling included fish community structure before and after our sites were invaded, i.e., we employed a modified BACI design. We found no evidence that lionfish measurably affected the density, richness, or composition of prey fishes. It is possible that higher lionfish densities are necessary to detect an effect of lionfish on prey populations at this relatively large spatial scale. Alternatively, negative effects of lionfish on prey could be small, essentially undetectable, and ecologically insignificant at our study sites. Other factors that influence the dynamics of reef fish populations including reef complexity, resource availability, recruitment, predation, and fishing could swamp any effects of lionfish on prey populations.

Effects of bromeliad flowering event on the community structuring of aquatic insect larvae associated with phytotelmata of Aechmea distichantha Lem. (Bromeliaceae

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Felipe Emiliano Amadeo

2017-12-01

Full Text Available Abstract Aim: We aimed to understand how aquatic insect larvae communities associated with bromeliad phytotelmata are affected by plant architecture, predators and resources (local factors, and by geographical distance (regional factors in two different plant phenological phases. Bromeliad flowering results in plant structural changes, which favours insect dispersal. Considering that local and regional factors may affect the community of aquatic insect larvae, we expected that composition, beta diversity and the importance of those factors would differ in the vegetative growth and flowering phases. Methods We performed six samplings of the bromeliad associated fauna in 2010, three during the first semester - vegetative growth phase - and three during the second semester - flowering phase. In each sampling, we collected 12 plants along the rocky walls with similar location distribution, with a total of 72 bromeliads studied. Results Although beta diversity (PERMDISP did not differ between vegetative growth and flowering, NMDS followed by ANOSIM showed that composition was significantly different in the distinct phenological phases. IndVal results showed that three Diptera morphospecies were discriminant of the vegetative growth phase. In addition, pRDA revealed differences in the relative contribution of local and regional factors to explain insect larvae community structure. During the flowering phase, local factors predominated, while during vegetative growth, regional factors were more important. Conclusion Differences in dispersal rates between the two phenological phases, likely due to adult insect pollination and further oviposition, influenced community structuring. Therefore, flowering events account for differences not only in the composition, but also in community structuring of aquatic insect larvae inhabiting the phytotelmata of Aechmea distichantha Lem. (Bromeliaceae.

Influence of fertilizer draw solution properties on the process performance and microbial community structure in a side-stream anaerobic fertilizer-drawn forward osmosis - ultrafiltration bioreactor.

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Kim, Youngjin; Li, Sheng; Chekli, Laura; Phuntsho, Sherub; Ghaffour, Noreddine; Leiknes, TorOve; Shon, Ho Kyong

2017-09-01

In this study, a side-stream anaerobic fertilizer-drawn forward osmosis (FDFO) and ultrafiltration (UF) membrane bioreactor (MBR) hybrid system was proposed and operated for 55days. The FDFO performance was first investigated in terms of flux decline with various fertilizers draw solution. Flux decline was very severe with all fertilizers due to the absence of aeration and the sticky property of sludge. Flux recovery by physical cleaning varied significantly amongst tested fertilizers which seriously affected biofouling in FDFO via reverse salt flux (RSF). Besides, RSF had a significant impact on nutrient accumulation in the bioreactor. These results indicated that nutrient accumulation negatively influenced the anaerobic activity. To elucidate these phenomena, bacterial and archaeal community structures were analyzed by pyrosequencing. Results showed that bacterial community structure was affected by fertilizer properties with less impact on archaeal community structure, which resulted in a reduction in biogas production and an increase in nitrogen content. Copyright © 2017 Elsevier Ltd. All rights reserved.

Functional gene array-based analysis of microbial community structure in groundwaters with a gradient of contaminant levels

Energy Technology Data Exchange (ETDEWEB)

Waldron, P.J.; Wu, L.; Van Nostrand, J.D.; Schadt, C.W.; Watson, D.B.; Jardine, P.M.; Palumbo, A.V.; Hazen, T.C.; Zhou, J.

2009-06-15

To understand how contaminants affect microbial community diversity, heterogeneity, and functional structure, six groundwater monitoring wells from the Field Research Center of the U.S. Department of Energy Environmental Remediation Science Program (ERSP; Oak Ridge, TN), with a wide range of pH, nitrate, and heavy metal contamination were investigated. DNA from the groundwater community was analyzed with a functional gene array containing 2006 probes to detect genes involved in metal resistance, sulfate reduction, organic contaminant degradation, and carbon and nitrogen cycling. Microbial diversity decreased in relation to the contamination levels of the wells. Highly contaminated wells had lower gene diversity but greater signal intensity than the pristine well. The microbial composition was heterogeneous, with 17-70% overlap between different wells. Metal-resistant and metal-reducing microorganisms were detected in both contaminated and pristine wells, suggesting the potential for successful bioremediation of metal-contaminated groundwaters. In addition, results of Mantel tests and canonical correspondence analysis indicate that nitrate, sulfate, pH, uranium, and technetium have a significant (p < 0.05) effect on microbial community structure. This study provides an overall picture of microbial community structure in contaminated environments with functional gene arrays by showing that diversity and heterogeneity can vary greatly in relation to contamination.

Pyridine-type alkaloid composition affects bacterial community composition of floral nectar.

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Aizenberg-Gershtein, Yana; Izhaki, Ido; Santhanam, Rakesh; Kumar, Pavan; Baldwin, Ian T; Halpern, Malka

2015-06-30

Pyridine-type alkaloids are most common in Nicotiana species. To study the effect of alkaloid composition on bacterial community composition in floral nectar, we compared the nicotine-rich wild type (WT) N. attenuata, the nicotine biosynthesis-silenced N. attenuata that was rich in anatabine and the anabasine-rich WT N. glauca plants. We found that the composition of these secondary metabolites in the floral nectar drastically affected the bacterial community richness, diversity and composition. Significant differences were found between the bacterial community compositions in the nectar of the three plants with a much greater species richness and diversity in the nectar from the transgenic plant. The highest community composition similarity index was detected between the two wild type plants. The different microbiome composition and diversity, caused by the different pyridine-type alkaloid composition, could modify the nutritional content of the nectar and consequently, may contribute to the change in the nectar consumption and visitation. These may indirectly have an effect on plant fitness.

Bacterial community structure in the Cerasus sachalinensis Kom ...

African Journals Online (AJOL)

Jane

2011-07-21

Jul 21, 2011 ... The bacterial community structures of the Cerasus sachalinensis Kom. rhizosphere in wild and cultivated soil were studied and the community changes in different growth stages were analyzed by the PCR-denaturing gradient gel electrophoresis (PCR-DGGE) method. The results showed that the bacterial ...

Canopy structural alterations to nitrogen functions of the soil microbial community in a Quercus virginiana forest

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Moore, L. D.; Van Stan, J. T., II; Rosier, C. L.; Gay, T. E.; Wu, T.

2014-12-01

Forest canopy structure controls the timing, amount and chemical character of precipitation supply to soils through interception and drainage along crown surfaces. Yet, few studies have examined forest canopy structural connections to soil microbial communities (SMCs), and none have measured how this affects SMC N functions. The maritime Quercus virginiana Mill. (southern live oak) forests of St Catherine's Island, GA, USA provide an ideal opportunity to examine canopy structural alterations to SMCs and their functioning, as their throughfall varies substantially across space due to dense Tillandsia usneoides L. (spanish moss) mats bestrewn throughout. To examine the impact of throughfall variability on SMC N functions, we examined points along the canopy coverage continuum: large canopy gaps (0%), bare canopy (50-60%), and canopy of heavy T. usneoides coverage (>=85%). Five sites beneath each of the canopy cover types were monitored for throughfall water/ions and soil leachates chemistry for one storm each month over the growing period (7 months, Mar-2014 to Sep-2014) to compare with soil chemistry and SMC communities sampled every two months throughout that same period (Mar, May, Jul, Sep). DGGE and QPCR analysis of the N functioning genes (NFGs) to characterize the ammonia oxidizing bacterial (AOB-amoA), archaea (AOA-amoA), and ammonification (chiA) communities were used to determine the nitrification and decomposition potential of these microbial communities. PRS™-probes (Western Ag Innovations Inc., Saskatoon, Canada) were then used to determine the availability of NO3-N and NH4+N in the soils over a 6-week period to evaluate whether the differing NFG abundance and community structures resulted in altered N cycling.

Aphid-parasitoid community structure on genetically modified wheat.

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von Burg, Simone; van Veen, Frank J F; Álvarez-Alfageme, Fernando; Romeis, Jörg

2011-06-23

Since the introduction of genetically modified (GM) plants, one of the main concerns has been their potential effect on non-target insects. Many studies have looked at GM plant effects on single non-target herbivore species or on simple herbivore-natural enemy food chains. Agro-ecosystems, however, are characterized by numerous insect species which are involved in complex interactions, forming food webs. In this study, we looked at transgenic disease-resistant wheat (Triticum aestivum) and its effect on aphid-parasitoid food webs. We hypothesized that the GM of the wheat lines directly or indirectly affect aphids and that these effects cascade up to change the structure of the associated food webs. Over 2 years, we studied different experimental wheat lines under semi-field conditions. We constructed quantitative food webs to compare their properties on GM lines with the properties on corresponding non-transgenic controls. We found significant effects of the different wheat lines on insect community structure up to the fourth trophic level. However, the observed effects were inconsistent between study years and the variation between wheat varieties was as big as between GM plants and their controls. This suggests that the impact of our powdery mildew-resistant GM wheat plants on food web structure may be negligible and potential ecological effects on non-target insects limited.

Opposing resonses to ecological gradients structure amphibian and reptile communities across a temperate grassland-savanna-forest landscape

Science.gov (United States)

Grundel, Ralph; Beamer, David; Glowacki, Gary A.; Frohnapple, Krystal; Pavlovic, Noel B.

2014-01-01

Temperate savannas are threatened across the globe. If we prioritize savanna restoration, we should ask how savanna animal communities differ from communities in related open habitats and forests. We documented distribution of amphibian and reptile species across an open-savanna–forest gradient in the Midwest U.S. to determine how fire history and habitat structure affected herpetofaunal community composition. The transition from open habitats to forests was a transition from higher reptile abundance to higher amphibian abundance and the intermediate savanna landscape supported the most species overall. These differences warn against assuming that amphibian and reptile communities will have similar ecological responses to habitat structure. Richness and abundance also often responded in opposite directions to some habitat characteristics, such as cover of bare ground or litter. Herpetofaunal community species composition changed along a fire gradient from infrequent and recent fires to frequent but less recent fires. Nearby (200-m) wetland cover was relatively unimportant in predicting overall herpetofaunal community composition while fire history and fire-related canopy and ground cover were more important predictors of composition, diversity, and abundance. Increased developed cover was negatively related to richness and abundance. This indicates the importance of fire history and fire related landscape characteristics, and the negative effects of development, in shaping the upland herpetofaunal community along the native grassland–forest continuum.

Strong influence of regional species pools on continent-wide structuring of local communities.

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Lessard, Jean-Philippe; Borregaard, Michael K; Fordyce, James A; Rahbek, Carsten; Weiser, Michael D; Dunn, Robert R; Sanders, Nathan J

2012-01-22

There is a long tradition in ecology of evaluating the relative contribution of the regional species pool and local interactions on the structure of local communities. Similarly, a growing number of studies assess the phylogenetic structure of communities, relative to that in the regional species pool, to examine the interplay between broad-scale evolutionary and fine-scale ecological processes. Finally, a renewed interest in the influence of species source pools on communities has shown that the definition of the source pool influences interpretations of patterns of community structure. We use a continent-wide dataset of local ant communities and implement ecologically explicit source pool definitions to examine the relative importance of regional species pools and local interactions for shaping community structure. Then we assess which factors underlie systematic variation in the structure of communities along climatic gradients. We find that the average phylogenetic relatedness of species in ant communities decreases from tropical to temperate regions, but the strength of this relationship depends on the level of ecological realism in the definition of source pools. We conclude that the evolution of climatic niches influences the phylogenetic structure of regional source pools and that the influence of regional source pools on local community structure is strong.

Bacterial Community Structure in a Mollisol Under Long-Term Natural Restoration, Cropping, and Bare Fallow History Estimated by PCR-DGGE

Institute of Scientific and Technical Information of China (English)

WANG Guang-Hua; JIN Jian; LIU Jun-Jie; CHEN Xue-Li; LIU Ju-Dong; LIU Xiao-Bing

2009-01-01

Soil microbial biomass and community structures are commonly used as indicators for soil quality and fertility.A investigation was performed to study the effects of long-term natural restoration,cropping,and bare fallow managements on the soil microbial biomass and bacterial community structures in depths of 0-10,20-30,and 40-50 cm in a black soil (Mollisol).Microbial biomass was estimated from chloroform fumigation-extraction,and bacterial community structures were determined by analysis of 16S rDNA using polymerase chain reaction-denaturing gradient gel electrophoresis (PCRDGGE).Experimental results showed that microbial biomass significantly declined with soil depth in the managements of restoration and cropping,but not in the bare fallow.DGGE profiles indicated that the band number in top 0-10 cm soils was less than that in depth of 20-30 or 40-50 cm.These suggested that the microbial population was high but the bacterial community structure was simple in the topsoil.Cluster and principle component analysis based on DGGE banding patterns showed that the bacterial community structure was affected by soil depth more primarily than by managements,and the succession of bacterial community as increase of soil depth has a similar tendency in the three managements.Fourteen predominating DGGE bands were excised and sequenced,in which 6 bands were identified as the taxa of Verrucomicrobia,2 bands as Actinobacteria,2 bands as α-Proteobacteria,and the other 4 bands as δ-Proteobacteria,Acidobacteria,Nitrospira,and unclassified bacteria.In addition,the sequences of 11 DGGE bands were closely related to uncultured bacteria.Thus,the bacterial community structure in black soil was stable,and the predominating bacterial groups were uncultured.

Impact of Hurricane Sandy on community pharmacies in severely affected areas of New York City: A qualitative assessment.

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Arya, Vibhuti; Medina, Eric; Scaccia, Allison; Mathew, Cathleen; Starr, David

2016-01-01

Hurricane Sandy was one of the most severe natural disasters to hit the Mid-Atlantic States in recent history. Community pharmacies were among the businesses affected, with flooding and power outages significantly reducing services offered by many pharmacies. The objectives of our study were to assess the impact of Hurricane Sandy on community pharmacies, both independently owned and chain, in the severely affected areas of New York City (NYC), including Coney Island, Staten Island, and the Rockaways, using qualitative methods, and propose strategies to mitigate the impact of future storms and disasters. Of the total 52 solicited pharmacies, 35 (67 percent) responded and were included in our analysis. Only 10 (29 percent) of the pharmacies surveyed reported having a generator during Hurricane Sandy; 37 percent reported being equipped with a generator at the time of the survey approximately 1 year later. Our findings suggest that issues other than power outages contributed more toward a pharmacy remaining operational after the storm. Of those surveyed, 26 (74 percent) suffered from structural damage (most commonly in Coney Island). Most pharmacies (71 percent) were able to reopen within 1 month. Despite staffing challenges, most pharmacies (88 percent) had enough pharmacists/staff to resume normal operations. Overall, 91 percent were aware of law changes for emergency medication access, and 81 percent found the information easy to obtain. This survey helped inform our work toward improved community resiliency. Our findings have helped us recognize community pharmacists as important stakeholders and refocus our energy toward developing sustained partnerships with them in NYC as part of our ongoing preparedness strategy.

Changes in community structure of active protistan assemblages from the lower Pearl River to coastal Waters of the South China Sea.

Science.gov (United States)

Li, Ran; Jiao, Nianzhi; Warren, Alan; Xu, Dapeng

2018-04-01

Protists make up an important component of aquatic ecosystems, playing crucial roles in biogeochemical processes on local and global scales. To reveal the changes of diversity and community structure of protists along the salinity gradients, community compositions of active protistan assemblages were characterized along a transect from the lower Pearl River estuary to the open waters of the South China Sea (SCS), using high-throughput sequencing of the hyper-variable V9 regions of 18S rRNA. This study showed that the alpha diversity of protists, both in the freshwater and in the coastal SCS stations was higher than that in the estuary. The protist community structure also changed along the salinity gradient. The relative sequence abundance of Stramenopiles was highest at stations with lower salinity and decreased with the increasing of salinity. By contrast, the contributions of Alveolata, Hacrobia and Rhizaria to the protistan communities generally increased with the increasing of salinity. The composition of the active protistan community was strongly correlated with salinity, indicating that salinity was the dominant factor among measured environmental parameters affecting protistan community composition and structure. Copyright © 2018 Elsevier GmbH. All rights reserved.

Governance Factors Affecting Community Participation In Public Development Projects In Meru District In Arusha In Tanzania

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Jackson Estomih Muro

2015-06-01

Full Text Available ABSTRACT The purpose of this study was to have a fresh look at the local governance status through exploring governance factors affecting community participation in public development projects. The study also has investigated the actors and factors shaping participation as well as causes for non-participation. For the purpose of the study six wards within two divisions of Poli and Mbuguni and Meru district headquarters were selected. In the wards a total of 80 respondents from among the community members were interviewed through a structured questionnaire. Others were Village chairman Village Executive Officers Ward Executive Officers and Councilors were also interviewed and involved in the FGD. Data were analyzed using SPSS. Simple descriptive statistics and cross tabulation and figures were used in the analysis. The analysis showed that the communities were participated in the public development projects and people were participating through financial material and labor contribution to the public development projects. The analysis also showed that the government supported the ongoing public development projects including through provision of fund and expertise. The study showed the benefit of community participation in the development projects or programs like ownership of the projects and enjoying the benefits accrued from the projects. The study also indicated that there is significant change in terms of governance as influencers of community participation in public development projects. Despite the fortunes study showed some challenges found in wards and villages being the incidence of corruptions and misuse of public resources which were mentioned to slow community participation in public development projects. It was therefore concluded that adhering to the good governance principles contribute positively towards community participation in public development projects.

Effects of application of corn straw on soil microbial community structure during the maize growing season.

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Lu, Ping; Lin, Yin-Hua; Yang, Zhong-Qi; Xu, Yan-Peng; Tan, Fei; Jia, Xu-Dong; Wang, Miao; Xu, De-Rong; Wang, Xi-Zhuo

2015-01-01

This study investigated the influence of corn straw application on soil microbial communities and the relationship between such communities and soil properties in black soil. The crop used in this study was maize (Zea mays L.). The five treatments consisted of applying a gradient (50, 100, 150, and 200%) of shattered corn straw residue to the soil. Soil samples were taken from May through September during the 2012 maize growing season. The microbial community structure was determined using phospholipid fatty acid (PLFA) analysis. Our results revealed that the application of corn straw influenced the soil properties and increased the soil organic carbon and total nitrogen. Applying corn straw to fields also influenced the variation in soil microbial biomass and community composition, which is consistent with the variations found in soil total nitrogen (TN) and soil respiration (SR). However, the soil carbon-to-nitrogen ratio had no effect on soil microbial communities. The abundance of PLFAs, TN, and SR was higher in C1.5 than those in other treatments, suggesting that the soil properties and soil microbial community composition were affected positively by the application of corn straw to black soil. A Principal Component Analysis indicated that soil microbial communities were different in the straw decomposition processes. Moreover, the soil microbial communities from C1.5 were significantly different from those of CK (p soil and significant variations in the ratio of monounsaturated-to-branched fatty acids with different straw treatments that correlated with SR (p soil properties and soil microbial communities and that these properties affect these communities. The individual PLFA signatures were sensitive indicators that reflected the changes in the soil environment condition. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Neighboring trees affect ectomycorrhizal fungal community composition in a woodland-forest ecotone.

Science.gov (United States)

Hubert, Nathaniel A; Gehring, Catherine A

2008-09-01

Ectomycorrhizal fungi (EMF) are frequently species rich and functionally diverse; yet, our knowledge of the environmental factors that influence local EMF diversity and species composition remains poor. In particular, little is known about the influence of neighboring plants on EMF community structure. We tested the hypothesis that the EMF of plants with heterospecific neighbors would differ in species richness and community composition from the EMF of plants with conspecific neighbors. We conducted our study at the ecotone between pinyon (Pinus edulis)-juniper (Juniperus monosperma) woodland and ponderosa pine (Pinus ponderosa) forest in northern Arizona, USA where the dominant trees formed associations with either EMF (P. edulis and P. ponderosa) or arbuscular mycorrhizal fungi (AMF; J. monosperma). We also compared the EMF communities of pinyon and ponderosa pines where their rhizospheres overlapped. The EMF community composition, but not species richness of pinyon pines was significantly influenced by neighboring AM juniper, but not by neighboring EM ponderosa pine. Ponderosa pine EMF communities were different in species composition when growing in association with pinyon pine than when growing in association with a conspecific. The EMF communities of pinyon and ponderosa pines were similar where their rhizospheres overlapped consisting of primarily the same species in similar relative abundance. Our findings suggest that neighboring tree species identity shaped EMF community structure, but that these effects were specific to host-neighbor combinations. The overlap in community composition between pinyon pine and ponderosa pine suggests that these tree species may serve as reservoirs of EMF inoculum for one another.

The Influence of Community Context on How Coalitions Achieve HIV-Preventive Structural Change

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Reed, Sarah J.; Miller, Robin Lin; Francisco, Vincent T.

2014-01-01

Community coalition action theory (CCAT) depicts the processes and factors that affect coalition formation, maintenance, institutionalization, actions, and outcomes. CCAT proposes that community context affects coalitions at every phase of development and operation. We analyzed data from 12 "Connect to Protect" coalitions using inductive…

Centralized Drinking Water Treatment Operations Shape Bacterial and Fungal Community Structure.

Science.gov (United States)

Ma, Xiao; Vikram, Amit; Casson, Leonard; Bibby, Kyle

2017-07-05

Drinking water microbial communities impact opportunistic pathogen colonization and corrosion of water distribution systems, and centralized drinking water treatment represents a potential control for microbial community structure in finished drinking water. In this article, we examine bacterial and fungal abundance and diversity, as well as the microbial community taxonomic structure following each unit operation in a conventional surface water treatment plant. Treatment operations drove the microbial composition more strongly than sampling time. Both bacterial and fungal abundance and diversity decreased following sedimentation and filtration; however, only bacterial abundance and diversity was significantly impacted by free chlorine disinfection. Similarly, each treatment step was found to shift bacterial and fungal community beta-diversity, with the exception of disinfection on the fungal community structure. We observed the enrichment of bacterial and fungal taxa commonly found in drinking water distribution systems through the treatment process, for example, Sphingomonas following filtration and Leptospirillium and Penicillium following disinfection. Study results suggest that centralized drinking water treatment processes shape the final drinking water microbial community via selection of community members and that the bacterial community is primarily driven by disinfection while the eukaryotic community is primarily controlled by physical treatment processes.

Seasonality and structure of the arthropod community in a forested ...

African Journals Online (AJOL)

The structure of an arthropod community in the forest floor vegetation was studied in a low altitude (about 700 m a.s.l.) forest valley in the Uluguru Mountains near Morogoro, Tanzania, by monthly sweep net sampling during one year (December 1996-November 1997). The community structure of arthropods changed ...

Structure and phylogenetic diversity of post-fire ectomycorrhizal communities of maritime pine.

Science.gov (United States)

Rincón, A; Santamaría, B P; Ocaña, L; Verdú, M

2014-02-01

Environmental disturbances define the diversity and assemblage of species, affecting the functioning of ecosystems. Fire is a major disturbance of Mediterranean pine forests. Pines are highly dependent on the ectomycorrhizal (EM) fungal symbiosis, which is critical for tree recruitment under primary succession. To determine the effects of time since fire on the structure and recovery of EM fungal communities, we surveyed the young Pinus pinaster regenerate in three sites differing in the elapsed time after the last fire event. Pine roots were collected, and EM fungi characterized by sequencing the internal transcribed spacer (ITS) and the large subunit (LSU) regions of the nuclear ribosomal (nr)-DNA. The effects of the elapsed time after fire on the EM community structure (richness, presence/absence of fungi, phylogenetic diversity) and on soil properties were analysed.Fungal richness decreased with the elapsed time since the fire; although, the phylogenetic diversity of the EM community increased. Soil properties were different depending on the elapsed time after fire and particularly, the organic matter, carbon-to-nitrogen (C/N) ratio, nitrogen and iron significantly correlated with the assemblage of fungal species. Ascomycetes, particularly Tuberaceae and Pezizales, were significantly over-represented on saplings in the burned site. On seedlings, a significant over-representation of Rhizopogonaceae and Atheliaceae was observed in the most recently burned site, while other fungi (i.e. Cortinariaceae) were significantly under-represented. Our results are consistent with the hypothesis that fire can act as a selective agent by printing a phylogenetic signal on the EM fungal communities associated with naturally regenerated pines, pointing out to some groups as potential fire-adapted fungi.

Community Structure and Productivity in Western Mongolian Steppe

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Kiyokazu Kawada

2014-12-01

Full Text Available The people of the Mongolian steppe have maintained a sustainable, nomadic lifestyle. However, several ecological processes are threatening their way of life. Ecological changan be detected through the analysis of quantitative and qualitative data. It is therefore, imperative to develop a sustainable rangeland management system aimed at combating desertifi cation. In this study we quantitatively and qualitatively describe several western Mongolian steppe plant communities by examining species composition, plant volume and community structure. Study sites were located in the Uvs and Khovd provinces and had all been affected by livestock grazing. A total of 48 species were found. Stipa krylovii , S . gobica , Cleistogenes songorica , Koeleria cristata and Ajania achilleoides were dominant. There was a signifi cant relationship between biomass and plant volume at all sites. Study sites were classifi ed into four groups using cluster analysis, based on the presence or absence of several species. More than 90% of plant volumes at all groups were perennial grasses and perennial forbs. The ratio of C 3 to C 4 plants at site 3 was reversed in comparison to the other sites. Species highly palatable to livestock were dominant at all sites. To ensure the sustainable use of biological resources in these arid areas, these fi ndings should be taken into account in designing land-use plans.

Influence of fertilizer draw solution properties on the process performance and microbial community structure in a side-stream anaerobic fertilizer-drawn forward osmosis – ultrafiltration bioreactor

KAUST Repository

Kim, Youngjin

2017-02-27

In this study, a side-stream anaerobic fertilizer-drawn forward osmosis (FDFO) and ultrafiltration (UF) membrane bioreactor (MBR) hybrid system was proposed and operated for 55 days. The FDFO performance was first investigated in terms of flux decline with various fertilizers draw solution. Flux decline was very severe with all fertilizers due to the absence of aeration and the sticky property of sludge. Flux recovery by physical cleaning varied significantly amongst tested fertilizers which seriously affected biofouling in FDFO via reverse salt flux (RSF). Besides, RSF had a significant impact on nutrient accumulation in the bioreactor. These results indicated that nutrient accumulation negatively influenced the anaerobic activity. To elucidate these phenomena, bacterial and archaeal community structures were analyzed by pyrosequencing. Results showed that bacterial community structure was affected by fertilizer properties with less impact on archaeal community structure, which resulted in a reduction in biogas production and an increase in nitrogen content.

Floral colour versus phylogeny in structuring subalpine flowering communities.

Science.gov (United States)

McEwen, Jamie R; Vamosi, Jana C

2010-10-07

The relative number of seeds produced by competing species can influence the community structure; yet, traits that influence seed production, such as pollinator attraction and floral colour, have received little attention in community ecology. Here, we analyse floral colour using reflectance spectra that include near-UV and examined the phylogenetic signal of floral colour. We found that coflowering species within communities tended to be more divergent in floral colour than expected by chance. However, coflowering species were not phylogenetically dispersed, in part due to our finding that floral colour is a labile trait with a weak phylogenetic signal. Furthermore, while we found that locally rare and common species exhibited equivalent floral colour distances from their coflowering neighbours, frequent species (those found in more communities) exhibited higher colour distances from their coflowering neighbours. Our findings support recent studies, which have found that (i) plant lineages exhibit frequent floral colour transitions; and (ii) traits that influence local population dynamics contribute to community structure.

Seasonal induced changes in spinach rhizosphere microbial community structure with varying salinity and drought.

Science.gov (United States)

Mark Ibekwe, A; Ors, Selda; Ferreira, Jorge F S; Liu, Xuan; Suarez, Donald L

2017-02-01

Salinity is a common problem under irrigated agriculture, especially in low rainfall and high evaporative demand areas of southwestern United States and other semi-arid regions around the world. However, studies on salinity effects on soil microbial communities are relatively few while the effects of irrigation-induced salinity on soil chemical and physical properties and plant growth are well documented. In this study, we examined the effects of salinity, temperature, and temporal variability on soil and rhizosphere microbial communities in sand tanks irrigated with prepared solutions designed to simulate saline wastewater. Three sets of experiments with spinach (Spinacia oleracea L., cv. Racoon) were conducted under saline water during different time periods (early winter, late spring, and early summer). Bacterial 16S V4 rDNA region was amplified utilizing fusion primers designed against the surrounding conserved regions using MiSeq® Illumina sequencing platform. Across the two sample types, bacteria were relatively dominant among three phyla-the Proteobacteria, Cyanobacteria, and Bacteroidetes-accounted for 77.1% of taxa detected in the rhizosphere, while Proteobacteria, Bacteroidetes, and Actinobacteria accounted for 55.1% of taxa detected in soil. The results were analyzed using UniFrac coupled with principal coordinate analysis (PCoA) to compare diversity, abundance, community structure, and specific bacterial groups in soil and rhizosphere samples. Permutational analysis of variance (PERMANOVA) analysis showed that soil temperature (P=0.001), rhizosphere temperature (P=0.001), rhizosphere salinity (P=0.032), and evapotranspiration (P=0.002) significantly affected beta diversity of soil and rhizosphere microbial communities. Furthermore, salinity had marginal effects (P=0.078) on soil beta diversity. However, temporal variability differentially affected rhizosphere microbial communities irrigated with saline wastewater. Therefore, microbial communities in

Community-oriented support and research structures

Energy Technology Data Exchange (ETDEWEB)

Attig, Norbert; Eickermann, Thomas; Gibbon, Paul; Lippert, Thomas, E-mail: th.lippert@fz-juelich.d [Institute for Advanced Simulation, Juelich Supercomputing Centre, Forschungszentrum Juelich, 52425 Juelich (Germany)

2009-07-01

Coordinated by the Partnership for Advanced Computing in Europe (PRACE) Europe is restructuring and strengthening its high-performance computing infrastructure with the aim to create a model HPC ecosystem. At the tip of the pyramid, up to six centres are envisaged that will operate systems of the highest performance class. The HPC Research Infrastructure (HPC-RI) will comprise European, national and regional centres. Science communities are integral partners, strong links will include Grid and Cloud users. The HPC-RI strives at providing scientists all over Europe, on the one hand, with unlimited and independent access to state-of-the-art computer resources in all performance classes and, on the other hand, with a world-class pan-European competence and support network. While the hardware-oriented buildup of the infrastructure is making progress, high-quality user support and software development in the upcoming era of unprecedented parallelism and exascale on the horizon have become the imminent challenges. This has been clearly recognized by the European Commission, who will issue calls for proposals to fund petascale software development in summer 2009. Although traditional support structures are well established in Europe's major supercomputing centres, it is questionable if these structures are able to meet the challenges of the future: in general, support structures are based on cross-disciplinary computer science and mathematics teams; disciplinary computational science support usually is given in an ad-hoc, project-oriented manner. In this paper, we describe our approach to establish a suitable support structure-Simulation Laboratories (SL). SLs are currently being established at the Juelich Supercomputing Centre of the Forschungszentrum Juelich (FZJ) and at the Steinbuch Centre for Computing (SCC) of the Karlsruhe Institute for Technology (KIT) in Germany. While SLs are community-oriented, i.e. each SL focusses on a specific community, they are

Community-oriented support and research structures

International Nuclear Information System (INIS)

Attig, Norbert; Eickermann, Thomas; Gibbon, Paul; Lippert, Thomas

2009-01-01

Coordinated by the Partnership for Advanced Computing in Europe (PRACE) Europe is restructuring and strengthening its high-performance computing infrastructure with the aim to create a model HPC ecosystem. At the tip of the pyramid, up to six centres are envisaged that will operate systems of the highest performance class. The HPC Research Infrastructure (HPC-RI) will comprise European, national and regional centres. Science communities are integral partners, strong links will include Grid and Cloud users. The HPC-RI strives at providing scientists all over Europe, on the one hand, with unlimited and independent access to state-of-the-art computer resources in all performance classes and, on the other hand, with a world-class pan-European competence and support network. While the hardware-oriented buildup of the infrastructure is making progress, high-quality user support and software development in the upcoming era of unprecedented parallelism and exascale on the horizon have become the imminent challenges. This has been clearly recognized by the European Commission, who will issue calls for proposals to fund petascale software development in summer 2009. Although traditional support structures are well established in Europe's major supercomputing centres, it is questionable if these structures are able to meet the challenges of the future: in general, support structures are based on cross-disciplinary computer science and mathematics teams; disciplinary computational science support usually is given in an ad-hoc, project-oriented manner. In this paper, we describe our approach to establish a suitable support structure-Simulation Laboratories (SL). SLs are currently being established at the Juelich Supercomputing Centre of the Forschungszentrum Juelich (FZJ) and at the Steinbuch Centre for Computing (SCC) of the Karlsruhe Institute for Technology (KIT) in Germany. While SLs are community-oriented, i.e. each SL focusses on a specific community, they are structured

Teachers' Challenges, Strategies, and Support Needs in Schools Affected by Community Violence: A Qualitative Study

Science.gov (United States)

Maring, Elisabeth F.; Koblinsky, Sally A.

2013-01-01

Background: Exposure to community violence compromises teacher effectiveness, student learning, and socioemotional well-being. This study examined the challenges, strategies, and support needs of teachers in urban schools affected by high levels of community violence. Methods: Twenty teachers from 3 urban middle schools with predominantly…

Clustering coefficient and community structure of bipartite networks

Science.gov (United States)

Zhang, Peng; Wang, Jinliang; Li, Xiaojia; Li, Menghui; Di, Zengru; Fan, Ying

2008-12-01

Many real-world networks display natural bipartite structure, where the basic cycle is a square. In this paper, with the similar consideration of standard clustering coefficient in binary networks, a definition of the clustering coefficient for bipartite networks based on the fraction of squares is proposed. In order to detect community structures in bipartite networks, two different edge clustering coefficients LC4 and LC3 of bipartite networks are defined, which are based on squares and triples respectively. With the algorithm of cutting the edge with the least clustering coefficient, communities in artificial and real world networks are identified. The results reveal that investigating bipartite networks based on the original structure can show the detailed properties that is helpful to get deep understanding about the networks.

Interactive effects of warming and increased precipitation on community structure and composition in an annual forb dominated desert steppe.

Directory of Open Access Journals (Sweden)

Yanhui Hou

Full Text Available To better understand how warming, increased precipitation and their interactions influence community structure and composition, a field experiment simulating hydrothermal interactions was conducted at an annual forb dominated desert steppe in northern China over 2 years. Increased precipitation increased species richness while warming significantly decreased species richness, and their effects were additive rather than interactive. Although interannual variations in weather conditions may have a major affect on plant community composition on short term experiments, warming and precipitation treatments affected individual species and functional group composition. Warming caused C4 grasses such as Cleistogenes squarrosa to increase while increased precipitation caused the proportions of non-perennial C3 plants like Artemisia capillaris to decrease and perennial C4 plants to increase.

Phylogenetic structure of arbuscular mycorrhizal fungal communities along an elevation gradient.

Science.gov (United States)

Egan, Cameron P; Callaway, Ragan M; Hart, Miranda M; Pither, Jason; Klironomos, John

2017-04-01

Despite the importance of arbuscular mycorrhizal (AM) fungi within terrestrial ecosystems, we know little about how natural AM fungal communities are structured. To date, the majority of studies examining AM fungal community diversity have focused on single habitats with similar environmental conditions, with relatively few studies having assessed the diversity of AM fungi over large-scale environmental gradients. In this study, we characterized AM fungal communities in the soil along a high-elevation gradient in the North American Rocky Mountains. We focused on phylogenetic patterns of AM fungal communities to gain insight into how AM fungal communities are naturally assembled. We found that alpine AM fungal communities had lower phylogenetic diversity relative to lower elevation communities, as well as being more heterogeneous in composition than either treeline or subalpine communities. AM fungal communities were phylogenetically clustered at all elevations sampled, suggesting that environmental filtering, either selection by host plants or fungal niches, is the primary ecological process structuring communities along the gradient.

Impact of performance interdependencies on structural vulnerability: A systems perspective of storm surge risk to coastal residential communities

International Nuclear Information System (INIS)

Hatzikyriakou, Adam; Lin, Ning

2017-01-01

Interaction between residential structures during natural hazards can lead to interdependencies in their performance. During storm surge, for example, structures can affect the performance of inland buildings by generating damaging waterborne debris or by beneficially dampening surge loads. Quantifying the impact of this interaction on structural vulnerability is critical for risk assessment and informed decision-making. In this study we present and implement two general modeling approaches for investigating such interdependencies. The first method is to condition the vulnerability of a structure on the performance of neighboring buildings using a Markov model. The second uses a marginal model to account for correlation between damage observations when estimating a structure's vulnerability to the hazard. Both approaches are implemented using a case study of an impacted coastal community during Hurricane Sandy (2012). Findings indicate that a structure's performance during storm surge is strongly dependent on the damage state of the structure immediately seaward. Furthermore, considering the correlated damage states of buildings increases statistical uncertainty when relating structural performance to hazard intensity. Motivated by these findings, we propose a more coordinated approach to coastal risk mitigation which considers the effects of interdependencies on insurance pricing, structural design, mitigation strategies and community resilience. - Highlights: • Interaction between residential structures leads to performance interdependencies. • Interdependencies during storm surge are due to debris and structural shielding. • Markov model treats interdependencies as an additional demand parameter. • Marginal model incorporates damage correlation into regression estimation. • System behavior should be considered in community risk and resilience.

Influence of tropical leaf litter on nitrogen mineralization and community structure of ammonia-oxidizing bacteria

Directory of Open Access Journals (Sweden)

Diallo, MD.

2015-01-01

Full Text Available Description of the subject. The present study concerns the relationships among leaf litter decomposition, substrate quality, ammonia-oxidizing bacteria (AOB community composition and nitrogen (N availability. Decomposition of organic matter affects the biogeochemical cycling of carbon (C and N. Since the composition of the soil microbial community can alter the physiological capacity of the community, it is timely to study the litter quality effect on N dynamic in ecosystems. Objectives. The aim of this study was to determine the influence of leaf litter decomposition on N mineralization. The specific objectives of this study were to evaluate the influence of the litter biochemistry of five plants species (Faidherbia albida A.Chev., Azadirachta indica A.Juss., Casuarina equisetifolia L., Andropogon gayanus Kunth and Eragrostis tremula Hochst. ex Steud. on N mineralization in a tropical ferrous soil (Lixisol, nitrification, and genetic diversity of ammonia-oxidizing bacteria. Denaturing gradient gel electrophoresis (DGGE of amplified fragments of genes coding for 16S rRNA was used to study the development of bacterial communities during decomposition of leaf litter in soils. Method. Community structure of AOB was determined at two time periods: day 0 and day 140. Ten strains were tested and each of these strains produced a single band. Thus, DGGE DNA band patterns were used to estimate bacterial diversity. Plant secondary compounds such as polyphenols are purported to influence nutrient cycling by affecting organic matter degradation, mineralization rates, N availability and humus formation. In a laboratory study, we investigated the influence of six phenolic acids (ferulic, gallic, vanillic, syringic, p-coumaric and p-HBA acids commonly found in the plant residues on N mineralization and NH4+ and NO3- production in soils. Results. The results showed that litter type did affect soil nitrification. Faidherbia albida litter was associated with

Ocean acidification affects competition for space: projections of community structure using cellular automata.

Science.gov (United States)

McCoy, Sophie J; Allesina, Stefano; Pfister, Catherine A

2016-03-16

Historical ecological datasets from a coastal marine community of crustose coralline algae (CCA) enabled the documentation of ecological changes in this community over 30 years in the Northeast Pacific. Data on competitive interactions obtained from field surveys showed concordance between the 1980s and 2013, yet also revealed a reduction in how strongly species interact. Here, we extend these empirical findings with a cellular automaton model to forecast ecological dynamics. Our model suggests the emergence of a new dominant competitor in a global change scenario, with a reduced role of herbivory pressure, or trophic control, in regulating competition among CCA. Ocean acidification, due to its energetic demands, may now instead play this role in mediating competitive interactions and thereby promote species diversity within this guild. © 2016 The Author(s).

Improving community mental health services for people affected by political violence in Ayacucho, Perú.

Science.gov (United States)

Rivera-Holguin, Miryam; Velazquez, Tesania; Custodio, Elba; Corveleyn, Jozef

2018-01-01

This study describes a model to intervene in communities affected by the political violence impacting the Ayacucho region of Peru since 1980s. Many community members still experience psychosocial consequences to this day due primarily to grief. Thirty-eight professionals from different sectors in the area received specialized training and implemented five community projects that were accompanied and monitored in the field by a team of community psychologists. This article is grounded on the principles of participation, building community capacity, and community strengthening. We present the analysis of five community action plans implemented over a period of 14 months. The results show a process of internal strengthening of community services and the identification of new social and community resources among the people involved in the action plans. The implications of capacity building for improving community mental health are discussed.

Function assessment of coastal ecosystem based on phytoplankton community structure

DEFF Research Database (Denmark)

Haraguchi, Lumi

2018-01-01

on phytoplankton community structure; and 3) investigating the role of planktonic communities on the cycling of dissolved organic matter. Those objectives were addressed focusing the temperate mesohaline estuary of Roskilde Fjord (Denmark). Paper I, explores the use of Pulse-shape recording flow cytometry (PFCM...... as an energy reservoir, buffering changes in the nutrient supply. Finally, the results embedded in this thesis demonstrate the importance of integrating different time scales to understand functioning of phytoplankton communities. Phytoplankton dynamics should not be regarded just in light of inorganic......This Ph.D. project aimed to improve the knowledge on phytoplankton community structure and its influence in the carbon transfer and nutrient cycling in coastal waters, by: 1) assessing the importance of phytoplankton

Fragmentation alters stream fish community structure in dendritic ecological networks.

Science.gov (United States)

Perkin, Joshuah S; Gido, Keith B

2012-12-01

Effects of fragmentation on the ecology of organisms occupying dendritic ecological networks (DENs) have recently been described through both conceptual and mathematical models, but few hypotheses have been tested in complex, real-world ecosystems. Stream fishes provide a model system for assessing effects of fragmentation on the structure of communities occurring within DENs, including how fragmentation alters metacommunity dynamics and biodiversity. A recently developed habitat-availability measure, the "dendritic connectivity index" (DCI), allows for assigning quantitative measures of connectivity in DENs regardless of network extent or complexity, and might be used to predict fish community response to fragmentation. We characterized stream fish community structure in 12 DENs in the Great Plains, USA, during periods of dynamic (summer) and muted (fall) discharge regimes to test the DCI as a predictive model of fish community response to fragmentation imposed by road crossings. Results indicated that fish communities in stream segments isolated by road crossings had reduced species richness (alpha diversity) relative to communities that maintained connectivity with the surrounding DEN during summer and fall. Furthermore, isolated communities had greater dissimilarity (beta diversity) to downstream sites notisolated by road crossings during summer and fall. Finally, dissimilarity among communities within DENs decreased as a function of increased habitat connectivity (measured using the DCI) for summer and fall, suggesting that communities within highly connected DENs tend to be more homogeneous. Our results indicate that the DCI is sensitive to community effects of fragmentation in riverscapes and might be used by managers to predict ecological responses to changes in habitat connectivity. Moreover, our findings illustrate that relating structural connectivity of riverscapes to functional connectivity among communities might aid in maintaining metacommunity

Structure of Mesozooplankton Communities in the Coastal Waters of Morocco

Science.gov (United States)

Lidvanov, V. V.; Grabko, O. G.; Kukuev, E. I.; Korolkova, T. G.

2018-03-01

Mero- and holoplanktonic organisms from 23 large taxa have been detected in the coastal waters of Morocco. Seven Cladocera species and 164 Copepoda species were identified. Copepod fauna mostly consisted of oceanic epipelagic widely tropical species, but the constant species group (frequency of occurrence over 50%) included neritic and neritic-oceanic widely tropical species. The neritic community that formed a biotopic association with coastal upwelling waters and the distant-neritic community associated with Canary Current waters were the two major communities detected. The former community was characterized by a high abundance and biomass (5700 ind./m3 and 260 mg/m3) and predominance of neritic species. The trophic structure was dominated by thin filter feeders, mixed-food consumers, and small grabbers; the species structure was dominated by Paracalanus indicus, Acartia clausi, and Oncaea curta; the indices of species diversity (3.07 bit/ind.) and evenness (0.63) were relatively low. The latter community was characterized by low abundance and biomass (1150 ind./m3 and 90 mg/m3); variable biotopic, trophic, and species structure; and higher Shannon indices (3.99 bit/ind.) and Pielou (0.75). Seasonal variation of the abundance of organisms was not detected in the communities. Anomalous mesozooplankton states were observed in summer 1998 and winter 1998-1999.

The importance of building construction materials relative to other factors affecting structure survival during wildfire

Science.gov (United States)

Syphard, Alexandra D.; Brennan, Teresa J.; Keeley, Jon E.

2017-01-01

Structure loss to wildfire is a serious problem in wildland-urban interface areas across the world. Laboratory experiments suggest that fire-resistant building construction and design could be important for reducing structure destruction, but these need to be evaluated under real wildfire conditions, especially relative to other factors. Using empirical data from destroyed and surviving structures from large wildfires in southern California, we evaluated the relative importance of building construction and structure age compared to other local and landscape-scale variables associated with structure survival. The local-scale analysis showed that window preparation was especially important but, in general, creating defensible space adjacent to the home was as important as building construction. At the landscape scale, structure density and structure age were the two most important factors affecting structure survival, but there was a significant interaction between them. That is, young structure age was most important in higher-density areas where structure survival overall was more likely. On the other hand, newer-construction structures were less likely to survive wildfires at lower density. Here, appropriate defensible space near the structure and accessibility to major roads were important factors. In conclusion, community safety is a multivariate problem that will require a comprehensive solution involving land use planning, fire-safe construction, and property maintenance.

Molecular analysis of microbial community structures in pristine and contaminated aquifers--Field and laboratory microcosm experiments

Science.gov (United States)

Shi, Y.; Zwolinski, M.D.; Schreiber, M.E.; Bahr, J.M.; Sewell, G.W.; Hickey, W.J.

1999-01-01

Molecular Analysis of Microbial Community Structures in Pristine and Contaminated Aquifers: Field and Laboratory Microcosm Experimentsvar callbackToken='531E8ACDB6C8511'; var subCode='asmjournal_sub'; var OAS_sitepage = 'aem.asm.org'; This study used phylogenetic probes in hybridization analysis to (i) determine in situ microbial community structures in regions of a shallow sand aquifer that were oxygen depleted and fuel contaminated (FC) or aerobic and noncontaminated (NC) and (ii) examine alterations in microbial community structures resulting from exposure to toluene and/or electron acceptor supplementation (nitrate). The latter objective was addressed by using the NC and FC aquifer materials for anaerobic microcosm studies in which phylogenetic probe analysis was complemented by microbial activity assays. Domain probe analysis of the aquifer samples showed that the communities were predominantlyBacteria; Eucarya and Archaea were not detectable. At the phylum and subclass levels, the FC and NC aquifer material had similar relative abundance distributions of 43 to 65% β- and γ-Proteobacteria (B+G), 31 to 35% α-Proteobacteria (ALF), 15 to 18% sulfate-reducing bacteria, and 5 to 10% high G+C gram positive bacteria. Compared to that of the NC region, the community structure of the FC material differed mainly in an increased abundance of B+G relative to that of ALF. The microcosm communities were like those of the field samples in that they were predominantly Bacteria (83 to 101%) and lacked detectable Archaea but differed in that a small fraction (2 to 8%) of Eucarya was detected regardless of the treatment applied. The latter result was hypothesized to reflect enrichment of anaerobic protozoa. Addition of nitrate and/or toluene stimulated microbial activity in the microcosms, but only supplementation of toluene alone significantly altered community structures. For the NC material, the dominant subclass shifted from B+G to ALF, while in the FC microcosms 55 to 65

Hunting or habitat? Drivers of waterbird abundance and community structure in agricultural wetlands of southern India.

Science.gov (United States)

Ramachandran, Ramesh; Kumar, Ajith; Gopi Sundar, Kolla S; Bhalla, Ravinder Singh

2017-09-01

The relative impacts of hunting and habitat on waterbird community were studied in agricultural wetlands of southern India. We surveyed wetlands to document waterbird community, and interviewed hunters to document hunting intensity, targeted species, and the motivations for hunting. Our results show that hunting leads to drastic declines in waterbird diversity and numbers, and skew the community towards smaller species. Hunting intensity, water spread, and vegetation cover were the three most important determinants of waterbird abundance and community structure. Species richness, density of piscivorous species, and medium-sized species (31-65 cm) were most affected by hunting. Out of 53 species recorded, 47 were hunted, with a preference for larger birds. Although illegal, hunting has increased in recent years and is driven by market demand. This challenges the widely held belief that waterbird hunting in India is a low intensity, subsistence activity, and undermines the importance of agricultural wetlands in waterbird conservation.

Microbial Fingerprints of Community Structure Correlate with Changes in Ecosystem Function Induced by Perturbing the Redox Environment

Science.gov (United States)

Mills, A. L.; Ford, R. M.; Vallino, J. J.; Herman, J. S.; Hornberger, G. M.

2001-12-01

Restoration of high-quality groundwater has been an elusive engineering goal. Consequently, natural microbially-mediated reactions are increasingly relied upon to degrade organic contaminants, including hydrocarbons and many synthetic compounds. Of concern is how the introduction of an organic chemical contaminant affects the indigenous microbial communities, the geochemistry of the aquifer, and the function of the ecosystem. The presence of functional redundancy in microbial communities suggests that recovery of the community after a disturbance such as a contamination event could easily result in a community that is similar in function to that which existed prior to the contamination, but which is compositionally quite different. To investigate the relationship between community structure and function we observed the response of a diverse microbial community obtained from raw sewage to a dynamic redox environment using an aerobic/anaerobic/aerobic cycle. To evaluate changes in community function CO2, pH, ammonium and nitrate levels were monitored. A phylogenetically-based DNA technique (tRFLP) was used to assess changes in microbial community structure. Principal component analysis of the tRFLP data revealed significant changes in the composition of the microbial community that correlated well with changes in community function. Results from our experiments will be discussed in the context of a metabolic model based the biogeochemistry of the system. The governing philosophy of this thermodynamically constrained metabolic model is that living systems synthesize and allocate cellular machinery in such a way as to "optimally" utilize available resources in the environment. The robustness of this optimization-based approach provides a powerful tool for studying relationships between microbial diversity and ecosystem function.

Organic matter quantity and source affects microbial community structure and function following volcanic eruption on Kasatochi Island, Alaska

Science.gov (United States)

Zeglin, Lydia H.; Wang, Bronwen; Waythomas, Christopher F.; Rainey, Frederick; Talbot, Sandra L.

2016-01-01

In August 2008, Kasatochi volcano erupted and buried a small island in pyroclastic deposits and fine ash; since then, microbes, plants and birds have begun to re-colonize the initially sterile surface. Five years post-eruption, bacterial 16S rRNA gene and fungal internal transcribed spacer (ITS) copy numbers and extracellular enzyme activity (EEA) potentials were one to two orders of magnitude greater in pyroclastic materials with organic matter (OM) inputs relative to those without, despite minimal accumulation of OM (eruptive surfaces with OM inputs had the highest β-glucosidase, phosphatase, NAGase and cellobiohydrolase activities, and had microbial population sizes approaching those in reference soils. In contrast, the strongest factor determining bacterial community composition was the dominance of plants versus birds as OM input vectors. Although soil pH ranged from 3.9 to 7.0, and %C ranged 100×, differentiation between plant- and bird-associated microbial communities suggested that cell dispersal or nutrient availability are more likely drivers of assembly than pH or OM content. This study exemplifies the complex relationship between microbial cell dispersal, soil geochemistry, and microbial structure and function; and illustrates the potential for soil microbiota to be resilient to disturbance.

Human exploitation and benthic community structure on a tropical intertidal mudflat

NARCIS (Netherlands)

Boer, de W.F.; Prins, H.H.T.

2002-01-01

Human exploitation of intertidal marine invertebrates is known to alter benthic community structure. This study describes the impact that harvesting by women and children has on the intertidal community structure of the mudflats of the Saco on Inhaca Island, Mozambique, by comparing the benthic

Stable pelagic vertebrate community structure through extreme Paleogene greenhouse conditions

Science.gov (United States)

Sibert, E. C.; Friedman, M.; Hull, P. M.; Hunt, G.; Norris, R. D.

2016-02-01

The species composition (structure) and energy transfer (function) of an ecosystem is reflected by the presence and type of consumers that it supports. Here we use ichthyoliths, microfossil fish teeth and shark denticles, to assess the ecological variability of the pelagic fish community structure and composition from the Late Cretaceous to the middle Eocene from a drill core in the South Pacific gyre (DSDP Site 596). We find that the overall vertebrate community structure, as measured by the relative abundance of sharks to ray-finned fishes, has a punctuated change at the Cretaceous/Paleogene mass extinction. The vertebrate community structure remained stable throughout the Paleogene despite a five-fold increase in overall abundance of ichthyoliths during the extreme greenhouse of the Early Eocene. Further, we use a novel system to quantify the morphological variation in fish teeth. We find that the morphospace occupied by the tooth assemblage is conserved throughout the interval, with a slight expansion following the Cretaceous-Paleogene mass extinction, and the evolution of a distinct morphotype-group around the Paleocene-Eocene boundary. While there are elevated rates of morphotype origination and extinction following the Cretaceous-Paleogene mass extinction, the extreme greenhouse warming of the Early Eocene and associated increase in fish production produce near-zero origination and extinction rates. The relative stability in composition of the pelagic vertebrate community during intervals of extreme climate change and across large ranges of total fish accumulation, suggests that pelagic ecosystem structure is robust to climate events, and that the overall structure of the pelagic fish community may be decoupled from both climate and ecosystem function.

Factors likely to affect community acceptance of a malaria vaccine in two districts of Ghana: a qualitative study.

Directory of Open Access Journals (Sweden)

Arantza Meñaca

Full Text Available Malaria is a leading cause of morbidity and mortality among children in Ghana. As part of the effort to inform local and national decision-making in preparation for possible malaria vaccine introduction, this qualitative study explored community-level factors that could affect vaccine acceptance in Ghana and provides recommendations for a health communications strategy. The study was conducted in two purposively selected districts: the Ashanti and Upper East Regions. A total of 25 focus group discussions, 107 in-depth interviews, and 21 semi-structured observations at Child Welfare Clinics were conducted. Malaria was acknowledged to be one of the most common health problems among children. While mosquitoes were linked to the cause and bed nets were considered to be the main preventive method, participants acknowledged that no single measure prevented malaria. The communities highly valued vaccines and cited vaccination as the main motivation for taking children to Child Welfare Clinics. Nevertheless, knowledge of specific vaccines and what they do was limited. While communities accepted the idea of minor vaccine side effects, other side effects perceived to be more serious could deter families from taking children for vaccination, especially during vaccination campaigns. Attendance at Child Welfare Clinics after age nine months was limited. Observations at clinics revealed that while two different opportunities for counseling were offered, little attention was given to addressing mothers' specific concerns and to answering questions related to child immunization. Positive community attitudes toward vaccines and the understanding that malaria prevention requires a comprehensive approach would support the introduction of a malaria vaccine. These attitudes are bolstered by a well-established child welfare program and the availability in Ghana of active, flexible structures for conveying health information to communities. At the same time, it would

Nested PCR Biases in Interpreting Microbial Community Structure in 16S rRNA Gene Sequence Datasets.

Science.gov (United States)

Yu, Guoqin; Fadrosh, Doug; Goedert, James J; Ravel, Jacques; Goldstein, Alisa M

2015-01-01

Sequencing of the PCR-amplified 16S rRNA gene has become a common approach to microbial community investigations in the fields of human health and environmental sciences. This approach, however, is difficult when the amount of DNA is too low to be amplified by standard PCR. Nested PCR can be employed as it can amplify samples with DNA concentration several-fold lower than standard PCR. However, potential biases with nested PCRs that could affect measurement of community structure have received little attention. In this study, we used 17 DNAs extracted from vaginal swabs and 12 DNAs extracted from stool samples to study the influence of nested PCR amplification of the 16S rRNA gene on the estimation of microbial community structure using Illumina MiSeq sequencing. Nested and standard PCR methods were compared on alpha- and beta-diversity metrics and relative abundances of bacterial genera. The effects of number of cycles in the first round of PCR (10 vs. 20) and microbial diversity (relatively low in vagina vs. high in stool) were also investigated. Vaginal swab samples showed no significant difference in alpha diversity or community structure between nested PCR and standard PCR (one round of 40 cycles). Stool samples showed significant differences in alpha diversity (except Shannon's index) and relative abundance of 13 genera between nested PCR with 20 cycles in the first round and standard PCR (Pnested PCR with 10 cycles in the first round and standard PCR. Operational taxonomic units (OTUs) that had low relative abundance (sum of relative abundance 27% of total OTUs in stool). Nested PCR introduced bias in estimated diversity and community structure. The bias was more significant for communities with relatively higher diversity and when more cycles were applied in the first round of PCR. We conclude that nested PCR could be used when standard PCR does not work. However, rare taxa detected by nested PCR should be validated by other technologies.

Macrobenthic community structure in the northern Saudi waters of the Gulf, 14years after the 1991 oil spill

KAUST Repository

Joydas, Thadickal Viswanathan

2012-02-01

The 1991 Gulf oil spill heavily impacted the coastal areas of the Saudi waters of the Arabian Gulf and recent studies have indicated that even 15. years after the incident, macrobenthos had not completely recovered in the sheltered bays in the affected region such as, Manifa Bay. This study investigates the community conditions of macrobenthos in the open waters in one of the impacted areas, Al-Khafji waters, about 14. years after the spill. Diversity measures and community structure analyses indicate a healthy status of polychaete communities. The BOPA index reveals that oil sensitive amphipods were recolonized in the study area. This confirms that the benthic communities of the oil spill impacted area had taken only <14 years to recover in the open waters of the impacted areas. The study also reveals the existence of three distinct polychaete communities along the depth and sediment gradients. © 2011 Elsevier Ltd.

Macrobenthic community structure in the northern Saudi waters of the Gulf, 14years after the 1991 oil spill

KAUST Repository

Joydas, Thadickal Viswanathan; Qurban, Mohammad Ali; Al-Suwailem, Abdulaziz M.; Krishnakumar, P. K.; Nazeer, Zahid B.; Cali, N. A.

2012-01-01

The 1991 Gulf oil spill heavily impacted the coastal areas of the Saudi waters of the Arabian Gulf and recent studies have indicated that even 15. years after the incident, macrobenthos had not completely recovered in the sheltered bays in the affected region such as, Manifa Bay. This study investigates the community conditions of macrobenthos in the open waters in one of the impacted areas, Al-Khafji waters, about 14. years after the spill. Diversity measures and community structure analyses indicate a healthy status of polychaete communities. The BOPA index reveals that oil sensitive amphipods were recolonized in the study area. This confirms that the benthic communities of the oil spill impacted area had taken only <14 years to recover in the open waters of the impacted areas. The study also reveals the existence of three distinct polychaete communities along the depth and sediment gradients. © 2011 Elsevier Ltd.

Antibiotic degradation and microbial community structures during acidification and methanogenesis of swine manure containing chlortetracycline or oxytetracycline.

Science.gov (United States)

Yin, Fubin; Dong, Hongmin; Zhang, Wanqin; Zhu, Zhiping; Shang, Bin

2018-02-01

Anaerobic digestion (AD) has been applied to animal manure stabilization, and antibiotics is frequently found in animal manure. However, antibiotic degradation and microbial community structures during two-stage AD (acidification and methanogenesis) remain poorly understood. This experiments on two-stage anaerobic swine manure digesters were performed to investigate the degradation mechanisms and effects of chlortetracycline (CTC) and oxytetracycline (OTC) on microbial community structures. Results showed that acidification and methanogenesis showed good degradation performance for manure containing CTC and OTC at 60 and 40 mg/kg·TS, respectively. CTC and OTC were degraded by 59.8% and 41.3% in the acidogenic stage and by 76.3% and 78.3% in the methanogenic stage, respectively. CTC and OTC negatively affected bacterial community in methanogenic and acidogenic stages, respectively. They also adversely influenced the archaeal species in the methanogenic stage. Two-stage AD was proposed to treat manure containing antibiotics and to reduce the negative effects of antibiotics on AD. Copyright © 2017 Elsevier Ltd. All rights reserved.

Microbial community structure characteristics associated membrane fouling in A/O-MBR system.

Science.gov (United States)

Gao, Da-Wen; Wen, Zhi-Dan; Li, Bao; Liang, Hong

2014-02-01

The study demonstrated the potential relationship between microbial community structure and membrane fouling in an anoxic-oxic membrane bioreactor (A/O-MBR). The results showed that the microbial community structure in biocake was different with aerobic mixture, and the dominant populations were out of sync during the fouling process. Based on microbial community structure and metabolites analysis, the results showed that the succession of microbial community might be the leading factor to the variation of metabolites, and it might be the primary cause of membrane fouling. The rise of Shannon diversity index (H) of the microbial community in A/O-MBR went with the gradually serious membrane fouling. Pareto-Lorenz curve was used to describe the evenness of microbial distribution in A/O-MBR, and the result indicated when community evenness was low, the membrane fouling took place smoothly or slightly, otherwise, high evenness of microbial community would lead to more seriously membrane fouling. Copyright © 2013 Elsevier Ltd. All rights reserved.

A new dynamic null model for phylogenetic community structure

NARCIS (Netherlands)

Pigot, Alex L; Etienne, Rampal S

Phylogenies are increasingly applied to identify the mechanisms structuring ecological communities but progress has been hindered by a reliance on statistical null models that ignore the historical process of community assembly. Here, we address this, and develop a dynamic null model of assembly by

How disturbances and management practices affect bird communities in a Carpathian river ecosystem?

Science.gov (United States)

Lacko, Jozef; Topercer, Ján; Súľovský, Marek

2018-04-01

We studied how interactions between disturbances, succession, human alterations and other habitat and landscape attributes affect bird community patterns in a lower reach of a large West Carpathian river Váh with complex disturbance and alteration histories. Breeding-bird communities, their habitats (54 variables) and surrounding landscapes (11 metrics) were sampled using standardized point counts with limited distances at 40 riparian sites divided among two transects along a 12.9 km river stretch. The most frequent and abundant birds were generalists typically associated with forest edge habitats, such as Parus major, Sylvia atricapilla, Fringilla coelebs, Oriolus oriolus, Phylloscopus collybita, Sturnus vulgaris, Turdus merula and Luscinia megarhynchos. Abundances show significant increase at the lower transect responding apparently to greater size and heterogeneity of riparian habitats and more abundant food supply linked to more diverse and intense human influences in a suburban zone. Both indirect (NMDS) and direct ordination (CCA) revealed remarkably large number of evenly important factors underlying riparian bird-habitat interactions. It suggests considerable environmental heterogeneity and complexity of these interactions as a likely outcome of long and complex disturbance and alteration histories of the area. Yet structure and relative importance of first two gradients (longitudinal and lateral linkages) remains simple and stable, complying well with predictions of river continuum concept and stream ecosystem theory. Of the nine statistically significant variables most strongly correlated with first two CCA axes, percentages of Helianthus tuberosus, footpaths, fields, Calystegia sepium and steep banks uphold our hypotheses predicting significant effects of invasive species, visitor disturbances, agricultural land use and unaltered river banks/bed on bird community composition and structure. A small but significant contribution of patch size standard

Vegetation structure of plantain-based agrosystems determines numerical dominance in community of ground-dwelling ants.

Science.gov (United States)

Dassou, Anicet Gbéblonoudo; Tixier, Philippe; Dépigny, Sylvain; Carval, Dominique

2017-01-01

In tropics, ants can represent an important part of animal biomass and are known to be involved in ecosystem services, such as pest regulation. Understanding the mechanisms underlying the structuring of local ant communities is therefore important in agroecology. In the humid tropics of Africa, plantains are cropped in association with many other annual and perennial crops. Such agrosystems differ greatly in vegetation diversity and structure and are well-suited for studying how habitat-related factors affect the ant community. We analysed abundance data for the six numerically dominant ant taxa in 500 subplots located in 20 diversified, plantain-based fields. We found that the density of crops with foliage at intermediate and high canopy strata determined the numerical dominance of species. We found no relationship between the numerical dominance of each ant taxon with the crop diversity. Our results indicate that the manipulation of the densities of crops with leaves in the intermediate and high strata may help maintain the coexistence of ant species by providing different habitat patches. Further research in such agrosystems should be performed to assess if the effect of vegetation structure on ant abundance could result in efficient pest regulation.

Context matters: community characteristics and mental health among war-affected youth in Sierra Leone.

Science.gov (United States)

Betancourt, Theresa S; McBain, Ryan; Newnham, Elizabeth A; Brennan, Robert T

2014-03-01

Worldwide, over one billion children and adolescents live in war-affected settings. At present, only limited research has investigated linkages between disrupted social ecology and adverse mental health outcomes among war-affected youth. In this study, we examine three community-level characteristics - social disorder and collective efficacy within the community, as reported by caregivers, and perceived stigma as reported by youth - in relation to externalizing behaviors and internalizing symptoms among male and female former child soldiers in postconflict Sierra Leone. A total of 243 former child soldiers (30% female, mean age at baseline: 16.6 years) and their primary caregivers participated in interviews in 2004 and 2008, as part of a larger prospective cohort study of war-affected youth in Sierra Leone. Two-point growth models were estimated to examine the relationship between community-level characteristics and externalizing and internalizing outcomes across the time points. Both social disorder within the community, reported by caregivers, and perceived stigma, reported by youth, positively covaried with youths' externalizing and internalizing scores - indicating that higher levels of each at baseline and follow-up were associated with higher levels of mental health problems at both time points (p mental health outcomes was nonsignificant (p > .05). This study offers a rare glimpse into the role that the postconflict social context plays in shaping the mental health among former child soldiers. Results indicate that both social disorder and perceived stigma within the community demonstrate an important relationship to externalizing and internalizing problems among adolescent ex-combatants. Moreover, these relationships persisted over a 4-year period of follow-up. These results underscore the importance of the postconflict social environment and the need to develop postconflict interventions that address community-level processes in addition to the needs

Warming-induced changes in denitrifier community structure modulate the ability of phototrophic river biofilms to denitrify

Energy Technology Data Exchange (ETDEWEB)

Boulêtreau, Stéphanie, E-mail: stephanie.bouletreau@univ-tlse3.fr [Université de Toulouse, UPS, INP, EcoLab (Laboratoire Ecologie Fonctionnelle et Environnement), 118 route de Narbonne, F-31062 Toulouse (France); CNRS, EcoLab, F-31062 Toulouse (France); Lyautey, Emilie [Université de Toulouse, UPS, INP, EcoLab (Laboratoire Ecologie Fonctionnelle et Environnement), 118 route de Narbonne, F-31062 Toulouse (France); CNRS, EcoLab, F-31062 Toulouse (France); Dubois, Sophie [Université de Bordeaux, EPOC - OASU, UMR 5805, Station Marine d' Arcachon, 2 rue du Professeur Jolyet, 33120 Arcachon (France); Compin, Arthur [Université de Toulouse, UPS, INP, EcoLab (Laboratoire Ecologie Fonctionnelle et Environnement), 118 route de Narbonne, F-31062 Toulouse (France); CNRS, EcoLab, F-31062 Toulouse (France); Delattre, Cécile; Touron-Bodilis, Aurélie [EDF Recherche et Développement, LNHE (Laboratoire National d' Hydraulique et Environnement), 6 quai Watier, F-78401 Chatou (France); Mastrorillo, Sylvain [Université de Toulouse, UPS, INP, EcoLab (Laboratoire Ecologie Fonctionnelle et Environnement), 118 route de Narbonne, F-31062 Toulouse (France); CNRS, EcoLab, F-31062 Toulouse (France); Garabetian, Frédéric [Université de Bordeaux, EPOC - OASU, UMR 5805, Station Marine d' Arcachon, 2 rue du Professeur Jolyet, 33120 Arcachon (France)

2014-01-01

Microbial denitrification is the main nitrogen removing process in freshwater ecosystems. The aim of this study was to show whether and how water warming (+ 2.5 °C) drives bacterial diversity and structuring and how bacterial diversity affects denitrification enzymatic activity in phototrophic river biofilms (PRB). We used water warming associated to the immediate thermal release of a nuclear power plant cooling circuit to produce natural PRB assemblages on glass slides while testing 2 temperatures (mean temperature of 17 °C versus 19.5 °C). PRB were sampled at 2 sampling times during PRB accretion (6 and 21 days) in both temperatures. Bacterial community composition was assessed using ARISA. Denitrifier community abundance and denitrification gene mRNA levels were estimated by q-PCR and qRT-PCR, respectively, of 5 genes encoding catalytic subunits of the denitrification key enzymes. Denitrification enzyme activity (DEA) was measured by the acetylene-block assay at 20 °C. A mean water warming of 2.5 °C was sufficient to produce contrasted total bacterial and denitrifier communities and, therefore, to affect DEA. Indirect temperature effect on DEA may have varied between sampling time, increasing by up to 10 the denitrification rate of 6-day-old PRB and decreasing by up to 5 the denitrification rate of 21-day-old PRB. The present results suggest that indirect effects of warming through changes in bacterial community composition, coupled to the strong direct effect of temperature on DEA already demonstrated in PRB, could modulate dissolved nitrogen removal by denitrification in rivers and streams. - Highlights: •We produced river biofilms in 2 mean temperature conditions: 17 vs 19.5 °C. •We compared their denitrifiers' structuring and functioning in 6d- and 21d-old biofilms. •A difference of 2.5 °C produced contrasted denitrifier communities. •The indirect temperature effect on denitrification activity shifted between biofilm age. �

Effects of chemical and biological pesticides on plant growth parameters and rhizospheric bacterial community structure in Vigna radiata

Energy Technology Data Exchange (ETDEWEB)

Singh, Sunil; Gupta, Rashi; Sharma, Shilpi, E-mail: shilpi@dbeb.iitd.ac.in

2015-06-30

Highlights: • Non-target effects of pesticides employing qualitative and quantitative approaches. • Qualitative shifts in resident and active bacterial community structure. • Abundance of 16S rRNA gene and transcripts were reduced significantly. • Effects of biological pesticide similar to chemical pesticides on rhizospheric bacteria. - Abstract: With increasing application of pesticides in agriculture, their non-target effects on soil microbial communities are critical to soil health maintenance. The present study aimed to evaluate the effects of chemical pesticides (chlorpyrifos and cypermethrin) and a biological pesticide (azadirachtin) on growth parameters and the rhizospheric bacterial community of Vigna radiata. Qualitative and quantitative analysis by PCR-denaturing gradient gel electrophoresis (DGGE) and q-PCR, respectively, of the 16S rRNA gene and transcript were performed to study the impact of these pesticides on the resident and active rhizospheric bacterial community. While plant parameters were not affected significantly by the pesticides, a shift in the bacterial community structure was observed with an adverse effect on the abundance of 16S rRNA gene and transcripts. Chlorpyrifos showed almost complete degradation toward the end of the experiment. These non-target impacts on soil ecosystems and the fact that the effects of the biopesticide mimic those of chemical pesticides raise serious concerns regarding their application in agriculture.

Effects of chemical and biological pesticides on plant growth parameters and rhizospheric bacterial community structure in Vigna radiata

International Nuclear Information System (INIS)

Singh, Sunil; Gupta, Rashi; Sharma, Shilpi

2015-01-01

Highlights: • Non-target effects of pesticides employing qualitative and quantitative approaches. • Qualitative shifts in resident and active bacterial community structure. • Abundance of 16S rRNA gene and transcripts were reduced significantly. • Effects of biological pesticide similar to chemical pesticides on rhizospheric bacteria. - Abstract: With increasing application of pesticides in agriculture, their non-target effects on soil microbial communities are critical to soil health maintenance. The present study aimed to evaluate the effects of chemical pesticides (chlorpyrifos and cypermethrin) and a biological pesticide (azadirachtin) on growth parameters and the rhizospheric bacterial community of Vigna radiata. Qualitative and quantitative analysis by PCR-denaturing gradient gel electrophoresis (DGGE) and q-PCR, respectively, of the 16S rRNA gene and transcript were performed to study the impact of these pesticides on the resident and active rhizospheric bacterial community. While plant parameters were not affected significantly by the pesticides, a shift in the bacterial community structure was observed with an adverse effect on the abundance of 16S rRNA gene and transcripts. Chlorpyrifos showed almost complete degradation toward the end of the experiment. These non-target impacts on soil ecosystems and the fact that the effects of the biopesticide mimic those of chemical pesticides raise serious concerns regarding their application in agriculture

Molecular Analysis of Microbial Community Structures in Pristine and Contaminated Aquifers: Field and Laboratory Microcosm Experiments

Science.gov (United States)

Shi, Y.; Zwolinski, M. D.; Schreiber, M. E.; Bahr, J. M.; Sewell, G. W.; Hickey, W. J.

1999-01-01

This study used phylogenetic probes in hybridization analysis to (i) determine in situ microbial community structures in regions of a shallow sand aquifer that were oxygen depleted and fuel contaminated (FC) or aerobic and noncontaminated (NC) and (ii) examine alterations in microbial community structures resulting from exposure to toluene and/or electron acceptor supplementation (nitrate). The latter objective was addressed by using the NC and FC aquifer materials for anaerobic microcosm studies in which phylogenetic probe analysis was complemented by microbial activity assays. Domain probe analysis of the aquifer samples showed that the communities were predominantly Bacteria; Eucarya and Archaea were not detectable. At the phylum and subclass levels, the FC and NC aquifer material had similar relative abundance distributions of 43 to 65% β- and γ-Proteobacteria (B+G), 31 to 35% α-Proteobacteria (ALF), 15 to 18% sulfate-reducing bacteria, and 5 to 10% high G+C gram positive bacteria. Compared to that of the NC region, the community structure of the FC material differed mainly in an increased abundance of B+G relative to that of ALF. The microcosm communities were like those of the field samples in that they were predominantly Bacteria (83 to 101%) and lacked detectable Archaea but differed in that a small fraction (2 to 8%) of Eucarya was detected regardless of the treatment applied. The latter result was hypothesized to reflect enrichment of anaerobic protozoa. Addition of nitrate and/or toluene stimulated microbial activity in the microcosms, but only supplementation of toluene alone significantly altered community structures. For the NC material, the dominant subclass shifted from B+G to ALF, while in the FC microcosms 55 to 65% of the Bacteria community was no longer identifiable by the phylum or subclass probes used. The latter result suggested that toluene exposure fostered the proliferation of phylotype(s) that were otherwise minor constituents of the

Associations between soil bacterial community structure and nutrient cycling functions in long-term organic farm soils following cover crop and organic fertilizer amendment.

Science.gov (United States)

Fernandez, Adria L; Sheaffer, Craig C; Wyse, Donald L; Staley, Christopher; Gould, Trevor J; Sadowsky, Michael J

2016-10-01

Agricultural management practices can produce changes in soil microbial populations whose functions are crucial to crop production and may be detectable using high-throughput sequencing of bacterial 16S rRNA. To apply sequencing-derived bacterial community structure data to on-farm decision-making will require a better understanding of the complex associations between soil microbial community structure and soil function. Here 16S rRNA sequencing was used to profile soil bacterial communities following application of cover crops and organic fertilizer treatments in certified organic field cropping systems. Amendment treatments were hairy vetch (Vicia villosa), winter rye (Secale cereale), oilseed radish (Raphanus sativus), buckwheat (Fagopyrum esculentum), beef manure, pelleted poultry manure, Sustane(®) 8-2-4, and a no-amendment control. Enzyme activities, net N mineralization, soil respiration, and soil physicochemical properties including nutrient levels, organic matter (OM) and pH were measured. Relationships between these functional and physicochemical parameters and soil bacterial community structure were assessed using multivariate methods including redundancy analysis, discriminant analysis, and Bayesian inference. Several cover crops and fertilizers affected soil functions including N-acetyl-β-d-glucosaminidase and β-glucosidase activity. Effects, however, were not consistent across locations and sampling timepoints. Correlations were observed among functional parameters and relative abundances of individual bacterial families and phyla. Bayesian analysis inferred no directional relationships between functional activities, bacterial families, and physicochemical parameters. Soil functional profiles were more strongly predicted by location than by treatment, and differences were largely explained by soil physicochemical parameters. Composition of soil bacterial communities was predictive of soil functional profiles. Differences in soil function were

Floral colour versus phylogeny in structuring subalpine flowering communities

OpenAIRE

McEwen, Jamie R.; Vamosi, Jana C.

2010-01-01

The relative number of seeds produced by competing species can influence the community structure; yet, traits that influence seed production, such as pollinator attraction and floral colour, have received little attention in community ecology. Here, we analyse floral colour using reflectance spectra that include near-UV and examined the phylogenetic signal of floral colour. We found that coflowering species within communities tended to be more divergent in floral colour than expected by chanc...

HOW ECOLOGICAL COMMUNITIES ARE STRUCTURED: A REVIEW ON ECOLOGICAL ASSEMBLY RULES

Directory of Open Access Journals (Sweden)

Gabriel Jaime Colorado Zuluaga

Full Text Available Whether biological communities are deterministic or stochastic assemblages of species has long been a central topic of ecology. The widely demonstrated presence of structural patterns in nature may imply the existence of rules that regulate the organization of ecological communities. In this review, I present a compilation of major assembly rules that fundament, in a great proportion, the community assembly theory. Initially, I present a general overview of key concepts associated to the assembly of communities, in particular the origin of assembly rules, definition, the problem of scale and underlying mechanisms in the structure of ecological communities. Subsequently, two major approaches or paradigms (i.e. species-based and trait-based for the assembly of communities are discussed. Finally, major tested assembly rules are explored and discussed under the light of available published literature.

[Fungal community structure in phase II composting of Volvariella volvacea].

Science.gov (United States)

Chen, Changqing; Li, Tong; Jiang, Yun; Li, Yu

2014-12-04

To understand the fungal community succession during the phase II of Volvariella volvacea compost and clarify the predominant fungi in different fermentation stages, to monitor the dynamic compost at the molecular level accurately and quickly, and reveal the mechanism. The 18S rDNA-denaturing gradient gel electrophoresis (DGGE) and sequencing methods were used to analyze the fungal community structure during the course of compost. The DGGE profile shows that there were differences in the diversity of fungal community with the fermentation progress. The diversity was higher in the stages of high temperature. And the dynamic changes of predominant community and relative intensity was observed. Among the 20 predominant clone strains, 9 were unknown eukaryote and fungi, the others were Eurotiales, Aspergillus sp., Melanocarpus albomyces, Colletotrichum sp., Rhizomucor sp., Verticillium sp., Penicillium commune, Microascus trigonosporus and Trichosporon lactis. The 14 clone strains were detected in the stages of high and durative temperature. The fungal community structure and predominant community have taken dynamic succession during the phase II of Volvariella volvacea compost.

How differentiated do children experience affect? An investigation of the within- and between-person structure of children's affect.

Science.gov (United States)

Leonhardt, Anja; Könen, Tanja; Dirk, Judith; Schmiedek, Florian

2016-05-01

Research on the structure of children's affect is limited. It is possible that children's perception of their own affect might be less differentiated than that of adults. Support for the 2-factor model of positive and negative affect and the pleasure-arousal model suggests that children in middle childhood can distinguish positive and negative affect as well as valence and arousal. Whether children are able to differentiate further aspects of affect, as proposed by the 3-dimensional model of affect (good-bad mood, alertness-tiredness, calmness-tension), is an unresolved issue. The aim of our study was the comparison of these 3 affect models to establish how differentiated children experience their affect and which model best describes affect in children. We examined affect structures on the between- and within-person level, acknowledging that affect varies across time and that no valid interpretation of either level is feasible if both are confounded. For this purpose, 214 children (age 8-11 years) answered affect items once a day for 5 consecutive days on smartphones. We tested all affect models by means of 2-level confirmatory factor analysis. Although all affect models had an acceptable fit, the 3-dimensional model best described affect in children on both the within- and between-person level. Thus, children in middle childhood can already describe affect in a differentiated way. Also, affect structures were similar on the within- and between-person level. We conclude that in order to acquire a thorough picture of children's affect, measures for children should include items of all 3 affect dimensions. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Structure and composition of bacterial and fungal community in soil under soybean monoculture in the Brazilian Cerrado

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J.D Bresolin

2010-06-01

Full Text Available Soybean is the most important oilseed cultivated in the world and Brazil is the second major producer. Expansion of soybean cultivation has direct and indirect impacts on natural habitats of high conservation value, such as the Brazilian savannas (Cerrado. In addition to deforestation, land conversion includes the use of fertilizers and pesticides and can lead to changes in the soil microbial communities. This study evaluated the soil bacterial and fungal communities and the microbial biomass C in a native Cerrado and in a similar no-tillage soybean monoculture area using PCR-DGGE and sequencing of bands. Compared to the native area, microbial biomass C was lower in the soybean area and cluster analysis indicated that the structure of soil microbial communities differed. 16S and 18S rDNA dendrograms analysis did not show differences between row and inter-row samples, but microbial biomass C values were higher in inter-rows during soybean fructification and harvest. The study pointed to different responses and alterations in bacterial and fungal communities due to soil cover changes (fallow x growth period and crop development. These changes might be related to differences in the pattern of root exudates affecting the soil microbial community. Among the bands chosen for sequencing there was a predominance of actinobacteria, y-proteobacteria and ascomycetous divisions. Even under no-tillage management methods, the soil microbial community was affected due to changes in the soil cover and crop development, hence warning of the impacts caused by changes in land use.

Colonisation and community structure of benthic diatoms on artificial ...

African Journals Online (AJOL)

This was undertaken using tiles as artificial substrates so that we could study how the communities developed after the flood disturbance. The diatom community structure was assessed over a 28-day period following a flood event in October 2012. The Mann Whitney test indicated that there was a statistically significant ...

Sampling from complex networks with high community structures.

Science.gov (United States)

Salehi, Mostafa; Rabiee, Hamid R; Rajabi, Arezo

2012-06-01

In this paper, we propose a novel link-tracing sampling algorithm, based on the concepts from PageRank vectors, to sample from networks with high community structures. Our method has two phases; (1) Sampling the closest nodes to the initial nodes by approximating personalized PageRank vectors and (2) Jumping to a new community by using PageRank vectors and unknown neighbors. Empirical studies on several synthetic and real-world networks show that the proposed method improves the performance of network sampling compared to the popular link-based sampling methods in terms of accuracy and visited communities.

Community structure and diversity of macrobenthic invertebrates in ...

African Journals Online (AJOL)

Macrobenthic invertebrates' community structure and diversity in relation to ... Analysis of variance (ANOVA) revealed that there were significant difference ... invertebrates' species distribution and some measured environmental variables.

An exploration of a fire-affected community undergoing change in New Zealand

Science.gov (United States)

Pamela J. Jakes; Laura Kelly; Lisa Langer

2010-01-01

In the first case study of a fire-affected community in New Zealand's rural-urban interface, researchers found evidence to support findings raised in other countries regarding evacuation, blaming behaviour and perceptions of risk. Differences were evident based on ownership tenure, including less awareness of wildfire risk and preparedness among those with shorter...

Minimum Wage and Community College Attendance: How Economic Circumstances Affect Educational Choices

Science.gov (United States)

Williams, Betsy

2013-01-01

How do changes in minimum wages affect community college enrollment and employment? In particular, among adults without associate's or bachelor's degrees who may earn near the minimum wage, do endowment effects of a higher minimum wage encourage school attendance? Among adults without associate's or bachelor's degrees who may earn near the minimum…

Set anode potentials affect the electron fluxes and microbial community structure in propionate-fed microbial electrolysis cells

KAUST Repository

Rao, Hari Ananda

2016-12-09

Anode potential has been shown to be a critical factor in the rate of acetate removal in microbial electrolysis cells (MECs), but studies with fermentable substrates and set potentials are lacking. Here, we examined the impact of three different set anode potentials (SAPs; −0.25, 0, and 0.25 V vs. standard hydrogen electrode) on the electrochemical performance, electron flux to various sinks, and anodic microbial community structure in two-chambered MECs fed with propionate. Electrical current (49–71%) and CH4 (22.9–41%) were the largest electron sinks regardless of the potentials tested. Among the three SAPs tested, 0 V showed the highest electron flux to electrical current (71 ± 5%) and the lowest flux to CH4 (22.9 ± 1.2%). In contrast, the SAP of −0.25 V had the lowest electron flux to current (49 ± 6%) and the highest flux to CH4 (41.1 ± 2%). The most dominant genera detected on the anode of all three SAPs based on 16S rRNA gene sequencing were Geobacter, Smithella and Syntrophobacter, but their relative abundance varied among the tested SAPs. Microbial community analysis implies that complete degradation of propionate in all the tested SAPs was facilitated by syntrophic interactions between fermenters and Geobacter at the anode and ferementers and hydrogenotrophic methanogens in suspension.

[Microbial Community Structure on the Root Surface of Patients with Periodontitis.

Science.gov (United States)

Zhang, Ju-Mei; Zhou, Jian-Ye; Bo, Lei; Hu, Xiao-Pan; Jiao, Kang-Li; Li, Zhi-Jie; Li, Yue-Hong; Li, Zhi-Qiang

2016-11-01

To study the microbial community structure on the root surface of patients with periodontitis. Bacterial plaque and tissues from the root neck (RN group),root middle (RM group) and root tine (RT group) of six teeth with mobility 3 in one patient with periodontitis were sampled.The V3V4 region of 16S rRNA was sequenced on the Illumina MiSeq platform.The microbial community structure was analyzed by Mothur,Qiime and SPSS software. The principal component analysis (PCoA) results indicated that the RM samples had a similar microbial community structure as that of the RT samples,which was significant different from that of the RN samples.Thirteen phyla were detected in the three groups of samples,which included 7 dominant phyla.29 dominant genera were detected in 184 genera.The abundance of Bacteroidetes _[G-6] and Peptostre ptococcaceae _[XI][G-4] had a positive correlation with the depth of the collection site of samples ( P microbial community structure on the root surface of patients with periodontitis.

Shifts in the abundance and community structure of soil ammonia oxidizers in a wet sclerophyll forest under long-term prescribed burning.

Science.gov (United States)

Long, Xi-En; Chen, Chengrong; Xu, Zhihong; He, Ji-Zheng

2014-02-01

Fire shapes global biome distribution and promotes the terrestrial biogeochemical cycles. Ammonia-oxidizing bacteria (AOB) and archaea (AOA) play a vital role in the biogeochemical cycling of nitrogen (N). However, behaviors of AOB and AOA under long-term prescribed burning remain unclear. This study was to examine how fire affected the abundances and communities of soil AOB and AOA. A long-term repeated forest fire experiment with three burning treatments (never burnt, B0; biennially burnt, B2; and quadrennially burnt, B4) was used in this study. The abundances and community structure of soil AOB and AOA were determined using quantitative PCR, restriction fragment length polymorphism and clone library. More frequent fires (B2) increased the abundance of bacterium amoA gene, but tended to decrease archaeal amoA genes. Fire also modified the composition of AOA and AOB communities. Canonical correspondence analysis showed soil pH and dissolved organic C (DOC) strongly affected AOB genotypes, while nitrate-N and DOC shaped the AOA distribution. The increased abundance of bacterium amoA gene by fires may imply an important role of AOB in nitrification in fire-affected soils. The fire-induced shift in the community composition of AOB and AOA demonstrates that fire can disturb nutrient cycles. © 2013.

Reduction and return of infectious trachoma in severely affected communities in Ethiopia.

Directory of Open Access Journals (Sweden)

Takele Lakew

Full Text Available Antibiotics are a major tool in the WHO's trachoma control program. Even a single mass distribution reduces the prevalence of the ocular chlamydia that causes trachoma. Unfortunately, infection returns after a single treatment, at least in severely affected areas. Here, we test whether additional scheduled treatments further reduce infection, and whether infection returns after distributions are discontinued.Sixteen communities in Ethiopia were randomly selected. Ocular chlamydial infection in 1- to 5-year-old children was monitored over four biannual azithromycin distributions and for 24 months after the last treatment.The average prevalence of infection in 1- to 5-year-old children was reduced from 63.5% pre-treatment to 11.5% six months after the first distribution (P<0.0001. It further decreased to 2.6% six months after the fourth and final treatment (P = 0.0004. In the next 18 months, infection returned to 25.2%, a significant increase from six months after the last treatment (P = 0.008, but still far lower than baseline (P<0.0001. Although the prevalence of infection in any particular village fluctuated, the mean prevalence of the 16 villages steadily decreased with each treatment and steadily returned after treatments were discontinued.In some of the most severely affected communities ever studied, we demonstrate that repeated mass oral azithromycin distributions progressively reduce ocular chlamydial infection in a community, as long as these distributions are given frequently enough and at a high enough coverage. However, infection returns into the communities after the last treatment. Sustainable changes or complete local elimination of infection will be necessary.ClinicalTrials.gov NCT00221364.

Strong influence of regional species pools on continent-wide structuring of local communities

DEFF Research Database (Denmark)

Lessard, Jean-Philippe; Borregaard, Michael Krabbe; Fordyce, James A.

2012-01-01

pool, to examine the interplay between broad-scale evolutionary and fine-scale ecological processes. Finally, a renewed interest in the influence of species source pools on communities has shown that the definition of the source pool influences interpretations of patterns of community structure. We use...... of communities along climatic gradients. We find that the average phylogenetic relatedness of species in ant communities decreases from tropical to temperate regions, but the strength of this relationship depends on the level of ecological realism in the definition of source pools. We conclude that the evolution...... of climatic niches influences the phylogenetic structure of regional source pools and that the influence of regional source pools on local community structure is strong....

Microbial Community Structure of Casing Soil During Mushroom Growth

Institute of Scientific and Technical Information of China (English)

CAI Wei-Ming; YAO Huai-Ying; FENG Wei-Lin; JIN Qun-Li; LIU Yue-Yan; LI Nan-Yi; ZHENG Zhong

2009-01-01

The culturable bacterial population and phospholipid fatty acid (PLFA)profile of casing soil were investigated at different mushroom (Agaricus bisporusI cropping stages.The change in soil bacterial PLFAs was always accompanied by a change in the soil culturable bacterial population in the first flush.Comparatively higher culturable bacterial population and bacterial PLFAs were found in the casing soil at the primordia formation stage of the first flush.There was a significant increase in the ratio of fungal to bacterial PLFAs during mushroom growth.Multivariate analysis of PLFA data demonstrated that the mushroom cropping stage could considerably affect the microbial community structure of the casing soil.The bacterial population increased significantly from casing soil application to the primordia formation stage of the first flush.Casing soil application resulted in an increase in the ratio of gram-negative bacterial PLFAs to gram-positive bacterial PLFAs,suggesting that some gram-negative bacteria might play an important role in mushroom sporophore initiation.

Sexual selection affects local extinction and turnover in bird communities

Science.gov (United States)

Doherty, P.F.; Sorci, G.; Royle, J. Andrew; Hines, J.E.; Nichols, J.D.; Boulinier, T.

2003-01-01

Predicting extinction risks has become a central goal for conservation and evolutionary biologists interested in population and community dynamics. Several factors have been put forward to explain risks of extinction, including ecological and life history characteristics of individuals. For instance, factors that affect the balance between natality and mortality can have profound effects on population persistence. Sexual selection has been identified as one such factor. Populations under strong sexual selection experience a number of costs ranging from increased predation and parasitism to enhanced sensitivity to environmental and demographic stochasticity. These findings have led to the prediction that local extinction rates should be higher for species/populations with intense sexual selection. We tested this prediction by analyzing the dynamics of natural bird communities at a continental scale over a period of 21 years (1975-1996), using relevant statistical tools. In agreement with the theoretical prediction, we found that sexual selection increased risks of local extinction (dichromatic birds had on average a 23% higher local extinction rate than monochromatic species). However, despite higher local extinction probabilities, the number of dichromatic species did not decrease over the period considered in this study. This pattern was caused by higher local turnover rates of dichromatic species, resulting in relatively stable communities for both groups of species. Our results suggest that these communities function as metacommunities, with frequent local extinctions followed by colonization. Anthropogenic factors impeding dispersal might therefore have a significant impact on the global persistence of sexually selected species.

Fishing degrades size structure of coral reef fish communities.

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Robinson, James P W; Williams, Ivor D; Edwards, Andrew M; McPherson, Jana; Yeager, Lauren; Vigliola, Laurent; Brainard, Russell E; Baum, Julia K

2017-03-01

Fishing pressure on coral reef ecosystems has been frequently linked to reductions of large fishes and reef fish biomass. Associated impacts on overall community structure are, however, less clear. In size-structured aquatic ecosystems, fishing impacts are commonly quantified using size spectra, which describe the distribution of individual body sizes within a community. We examined the size spectra and biomass of coral reef fish communities at 38 US-affiliated Pacific islands that ranged in human presence from near pristine to human population centers. Size spectra 'steepened' steadily with increasing human population and proximity to market due to a reduction in the relative biomass of large fishes and an increase in the dominance of small fishes. Reef fish biomass was substantially lower on inhabited islands than uninhabited ones, even at inhabited islands with the lowest levels of human presence. We found that on populated islands size spectra exponents decreased (analogous to size spectra steepening) linearly with declining biomass, whereas on uninhabited islands there was no relationship. Size spectra were steeper in regions of low sea surface temperature but were insensitive to variation in other environmental and geomorphic covariates. In contrast, reef fish biomass was highly sensitive to oceanographic conditions, being influenced by both oceanic productivity and sea surface temperature. Our results suggest that community size structure may be a more robust indicator than fish biomass to increasing human presence and that size spectra are reliable indicators of exploitation impacts across regions of different fish community compositions, environmental drivers, and fisheries types. Size-based approaches that link directly to functional properties of fish communities, and are relatively insensitive to abiotic variation across biogeographic regions, offer great potential for developing our understanding of fishing impacts in coral reef ecosystems. © 2016

Multi-scale structural community organisation of the human genome.

Science.gov (United States)

Boulos, Rasha E; Tremblay, Nicolas; Arneodo, Alain; Borgnat, Pierre; Audit, Benjamin

2017-04-11

Structural interaction frequency matrices between all genome loci are now experimentally achievable thanks to high-throughput chromosome conformation capture technologies. This ensues a new methodological challenge for computational biology which consists in objectively extracting from these data the structural motifs characteristic of genome organisation. We deployed the fast multi-scale community mining algorithm based on spectral graph wavelets to characterise the networks of intra-chromosomal interactions in human cell lines. We observed that there exist structural domains of all sizes up to chromosome length and demonstrated that the set of structural communities forms a hierarchy of chromosome segments. Hence, at all scales, chromosome folding predominantly involves interactions between neighbouring sites rather than the formation of links between distant loci. Multi-scale structural decomposition of human chromosomes provides an original framework to question structural organisation and its relationship to functional regulation across the scales. By construction the proposed methodology is independent of the precise assembly of the reference genome and is thus directly applicable to genomes whose assembly is not fully determined.

Bacterial density and community structure associated with aggregate size fractions of soil-feeding termite mounds.

Science.gov (United States)

Fall, S; Nazaret, S; Chotte, J L; Brauman, A

2004-08-01

The building and foraging activities of termites are known to modify soil characteristics such as the heterogeneity. In tropical savannas the impact of the activity of soil-feeding termites ( Cubitermes niokoloensis) has been shown to affect the properties of the soil at the aggregate level by creating new soil microenvironments (aggregate size fractions) [13]. These changes were investigated in greater depth by looking at the microbial density (AODC) and the genetic structure (automated rRNA intergenic spacer analysis: ARISA) of the communities in the different aggregate size fractions (i.e., coarse sand, fine sand, coarse silt, fine silt, and dispersible clays) separated from compartments (internal and external wall) of three Cubitermes niokoloensis mounds. The bacterial density of the mounds was significantly higher (1.5 to 3 times) than that of the surrounding soil. Within the aggregate size fractions, the termite building activity resulted in a significant increase in bacterial density within the coarser fractions (>20 mum). Multivariate analysis of the ARISA profiles revealed that the bacterial genetic structures of unfractionated soil and soil aggregate size fractions of the three mounds was noticeably different from the savanna soil used as a reference. Moreover, the microbial community associated with the different microenvironments in the three termite mounds revealed three distinct clusters formed by the aggregate size fractions of each mound. Except for the 2-20 mum fraction, these results suggest that the mound microbial genetic structure is more dependent upon microbial pool affiliation (the termite mound) than on the soil location (aggregate size fraction). The causes of the specificity of the microbial community structure of termite mound aggregate size fractions are discussed.

High taxonomic variability despite stable functional structure across microbial communities.

Science.gov (United States)

Louca, Stilianos; Jacques, Saulo M S; Pires, Aliny P F; Leal, Juliana S; Srivastava, Diane S; Parfrey, Laura Wegener; Farjalla, Vinicius F; Doebeli, Michael

2016-12-05

Understanding the processes that are driving variation of natural microbial communities across space or time is a major challenge for ecologists. Environmental conditions strongly shape the metabolic function of microbial communities; however, other processes such as biotic interactions, random demographic drift or dispersal limitation may also influence community dynamics. The relative importance of these processes and their effects on community function remain largely unknown. To address this uncertainty, here we examined bacterial and archaeal communities in replicate 'miniature' aquatic ecosystems contained within the foliage of wild bromeliads. We used marker gene sequencing to infer the taxonomic composition within nine metabolic functional groups, and shotgun environmental DNA sequencing to estimate the relative abundances of these groups. We found that all of the bromeliads exhibited remarkably similar functional community structures, but that the taxonomic composition within individual functional groups was highly variable. Furthermore, using statistical analyses, we found that non-neutral processes, including environmental filtering and potentially biotic interactions, at least partly shaped the composition within functional groups and were more important than spatial dispersal limitation and demographic drift. Hence both the functional structure and taxonomic composition within functional groups of natural microbial communities may be shaped by non-neutral and roughly separate processes.

Matrix composition and community structure analysis of a novel bacterial pyrite leaching community.

Science.gov (United States)

Ziegler, Sibylle; Ackermann, Sonia; Majzlan, Juraj; Gescher, Johannes

2009-09-01

Here we describe a novel bacterial community that is embedded in a matrix of carbohydrates and bio/geochemical products of pyrite (FeS(2)) oxidation. This community grows in stalactite-like structures--snottites--on the ceiling of an abandoned pyrite mine at pH values of 2.2-2.6. The aqueous phase in the matrix contains 200 mM of sulfate and total iron concentrations of 60 mM. Micro-X-ray diffraction analysis showed that jarosite [(K,Na,H(3)O)Fe(3)(SO(4))(2)(OH)(6)] is the major mineral embedded in the snottites. X-ray absorption near-edge structure experiments revealed three different sulfur species. The major signal can be ascribed to sulfate, and the other two features may correspond to thiols and sulfoxides. Arabinose was detected as the major sugar component in the extracellular polymeric substance. Via restriction fragment length polymorphism analysis, a community was found that mainly consists of iron oxidizing Leptospirillum and Ferrovum species but also of bacteria that could be involved in dissimilatory sulfate and dissimilatory iron reduction. Each snottite can be regarded as a complex, self-contained consortium of bacterial species fuelled by the decomposition of pyrite.

Factors that affect the quality of life of community-dwelling elderly women with musculoskeletal disorders.

Science.gov (United States)

Takemasa, Seiichi; Nakagoshi, Ryoma; Uesugi, Masayuki; Inoue, Yuri; Gotou, Makoto; Koeda, Hideki; Naruse, Susumu

2015-11-01

[Purpose] This study aimed to examine the quality of life (QOL) of community-dwelling elderly women with musculoskeletal disorders and factors that affect it. [Subjects] The subjects were 27 community-dwelling elderly women with musculoskeletal disorders (mean age: 76.3 ± 7.4 years). Their physical and psychological conditions, QOL, and other characteristics were researched. [Methods] The Japanese version of Life-Space Assessment was used to assess the subjects' daily life activities; the Japanese version of Fall Efficacy Scale (FES), to assess their fear of falling; the Geriatric Depression Scale (GDS 15), to assess their depression status; and the Life Satisfaction Index K (LSIK), to assess their QOL. [Results] The results indicated that the number of family members living together, degree of pain, fear of falling, and depression affect the LSIK scores of the community-dwelling elderly women with musculoskeletal disorders. [Conclusion] The study results suggest that the LSIK scores of community-dwelling elderly women with musculoskeletal disorders can be improved by easing their pain, improving their physical abilities to prevent falls, and improving their mobility. The results also suggest that continuing rehabilitation treatment is required.

The Relationship Between Low-Frequency Motions and Community Structure of Residue Network in Protein Molecules.

Science.gov (United States)

Sun, Weitao

2018-01-01

The global shape of a protein molecule is believed to be dominant in determining low-frequency deformational motions. However, how structure dynamics relies on residue interactions remains largely unknown. The global residue community structure and the local residue interactions are two important coexisting factors imposing significant effects on low-frequency normal modes. In this work, an algorithm for community structure partition is proposed by integrating Miyazawa-Jernigan empirical potential energy as edge weight. A sensitivity parameter is defined to measure the effect of local residue interaction on low-frequency movement. We show that community structure is a more fundamental feature of residue contact networks. Moreover, we surprisingly find that low-frequency normal mode eigenvectors are sensitive to some local critical residue interaction pairs (CRIPs). A fair amount of CRIPs act as bridges and hold distributed structure components into a unified tertiary structure by bonding nearby communities. Community structure analysis and CRIP detection of 116 catalytic proteins reveal that breaking up of a CRIP can cause low-frequency allosteric movement of a residue at the far side of protein structure. The results imply that community structure and CRIP may be the structural basis for low-frequency motions.

Multistage A-O Activated Sludge Process for Paraformaldehyde Wastewater Treatment and Microbial Community Structure Analysis

Directory of Open Access Journals (Sweden)

Danyang Zheng

2016-01-01

Full Text Available In recent years, the effect of formaldehyde on microorganisms and body had become a global public health issue. The multistage combination of anaerobic and aerobic process was adopted to treat paraformaldehyde wastewater. Microbial community structure in different reaction stages was analyzed through high-throughput sequencing. Results showed that multistage A-O activated sludge process positively influenced polyformaldehyde wastewater. The removal rates of formaldehyde were basically stable at more than 99% and those of COD were about 89%. Analysis of the microbial diversity index indicated that the microbial diversity of the reactor was high, and the treatment effect was good. Moreover, microbial community had certain similarity in the same system. Microbial communities in different units also showed typical representative characteristics affected by working conditions and influent concentrations. Proteobacteria, Firmicutes, and Bacteroidetes were the dominant fungal genera in the phylum level of community composition. As to family and genus levels, Peptostreptococcaceae was distributed at various stages and the dominant in this system. This bacterium also played an important role in organic matter removal, particularly decomposition of the acidified middle metabolites. In addition, Rhodobacteraceae and Rhodocyclaceae were the formaldehyde-degrading bacteria found in the reactor.

Changes in diversity, abundance, and structure of soil bacterial communities in Brazilian Savanna under different land use systems.

Science.gov (United States)

Rampelotto, Pabulo Henrique; de Siqueira Ferreira, Adão; Barboza, Anthony Diego Muller; Roesch, Luiz Fernando Wurdig

2013-10-01

The Brazilian Savanna, also known as "Cerrado", is the richest and most diverse savanna in the world and has been ranked as one of the main hotspots of biodiversity. The Cerrado is a representative biome in Central Brazil and the second largest biome in species diversity of South America. Nevertheless, large areas of native vegetation have been converted to agricultural land including grain production, livestock, and forestry. In this view, understanding how land use affects microbial communities is fundamental for the sustainable management of agricultural ecosystems. The aim of this work was to analyze and compare the soil bacterial communities from the Brazilian Cerrado associated with different land use systems using high throughput pyrosequencing of 16S rRNA genes. Relevant differences were observed in the abundance and structure of bacterial communities in soils under different land use systems. On the other hand, the diversity of bacterial communities was not relevantly changed among the sites studied. Land use systems had also an important impact on specific bacterial groups in soil, which might change the soil function and the ecological processes. Acidobacteria, Proteobacteria, and Actinobacteria were the most abundant groups in the Brazilian Cerrado. These findings suggest that more important than analyzing the general diversity is to analyze the composition of the communities. Since soil type was the same among the sites, we might assume that land use was the main factor defining the abundance and structure of bacterial communities.

The impact of coastal urbanization on the structure of phytobenthic communities in southern Brazil.

Science.gov (United States)

Martins, Cintia D L; Arantes, Noele; Faveri, Caroline; Batista, Manuela B; Oliveira, Eurico C; Pagliosa, Paulo R; Fonseca, Alessandra L; Nunes, José Marcos C; Chow, Fungyi; Pereira, Sonia B; Horta, Paulo A

2012-04-01

The anthropogenic pressures on coastal areas represent important factors affecting local, regional, and even global patterns of distribution and abundance of benthic organisms. This report undertakes a comparative analysis of the community structure of rocky shore intertidal phytobenthos in both pristine like environments (PLE) and urbanized environments (UBE) in southern Brazil, characterizing variations on different spatial scales. Multivariate analysis of variance indicated that the PLE is characterized by a larger number of taxa and an increased occurrence of Rhodophyta species in relation to UBE. In contrast, UBE were dominated by opportunistic algae, such as Cladophora and Ulva spp. Significance tests further indicated higher species richness and Shannon-Wiener diversity on the PLE in relation to UBE. Here we provide data showing the magnitude of seaweed biodiversity loss and discuss direct and indirect consequences of unplanned urbanization on these communities. Copyright © 2012 Elsevier Ltd. All rights reserved.

Plant assemblage composition and soil P concentration differentially affect communities of AM and total fungi in a semi-arid grassland.

Science.gov (United States)

Klabi, Rim; Bell, Terrence H; Hamel, Chantal; Iwaasa, Alan; Schellenberg, Mike; Raies, Aly; St-Arnaud, Marc

2015-01-01

Adding inorganic P- and N-fixing legumes to semi-arid grasslands can increase forage yield, but soil nutrient concentrations and plant cover may also interact to modify soil fungal populations, impacting short- and long-term forage production. We tested the effect of plant assemblage (seven native grasses, seven native grasses + the domesticated N-fixing legume Medicago sativa, seven native grasses + the native N-fixing legume Dalea purpurea or the introduced grass Bromus biebersteinii + M. sativa) and soil P concentration (addition of 0 or 200 P2O5 kg ha(-1) at sowing) on the diversity and community structure of arbuscular mycorrhizal (AM) fungi and total fungi over two consecutive years, using 454-pyrosequencing of 18S rDNA and ITS amplicons. Treatment effects were stronger in the wet year (2008) than the dry year (2009). The presence of an N-fixing legume with native grasses generally increased AM fungal diversity, while the interaction between soil P concentration and plant assemblage modified total fungal community structure in 2008. Excluding interannual variations, which are likely driven by moisture and plant productivity, AM fungal communities in semi-arid grasslands appear to be primarily affected by plant assemblage composition, while the composition of other fungi is more closely linked to soil P. © FEMS 2014. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Burning fire-prone Mediterranean shrublands: immediate changes in soil microbial community structure and ecosystem functions.

Science.gov (United States)

Goberna, M; García, C; Insam, H; Hernández, M T; Verdú, M

2012-07-01

Wildfires subject soil microbes to extreme temperatures and modify their physical and chemical habitat. This might immediately alter their community structure and ecosystem functions. We burned a fire-prone shrubland under controlled conditions to investigate (1) the fire-induced changes in the community structure of soil archaea, bacteria and fungi by analysing 16S or 18S rRNA gene amplicons separated through denaturing gradient gel electrophoresis; (2) the physical and chemical variables determining the immediate shifts in the microbial community structure; and (3) the microbial drivers of the change in ecosystem functions related to biogeochemical cycling. Prokaryotes and eukaryotes were structured by the local environment in pre-fire soils. Fire caused a significant shift in the microbial community structure, biomass C, respiration and soil hydrolases. One-day changes in bacterial and fungal community structure correlated to the rise in total organic C and NO(3)(-)-N caused by the combustion of plant residues. In the following week, bacterial communities shifted further forced by desiccation and increasing concentrations of macronutrients. Shifts in archaeal community structure were unrelated to any of the 18 environmental variables measured. Fire-induced changes in the community structure of bacteria, rather than archaea or fungi, were correlated to the enhanced microbial biomass, CO(2) production and hydrolysis of C and P organics. This is the first report on the combined effects of fire on the three biological domains in soils. We concluded that immediately after fire the biogeochemical cycling in Mediterranean shrublands becomes less conservative through the increased microbial biomass, activity and changes in the bacterial community structure.

Are gay communities dying or just in transition? Results from an international consultation examining possible structural change in gay communities.

Science.gov (United States)

Simon Rosser, B R; West, William; Weinmeyer, Richard

2008-05-01

This study sought to identify how urban gay communities are undergoing structural change, reasons for that change, and implications for HIV prevention planning. Key informants (N=29) at the AIDS Impact Conference from 17 cities in 14 countries completed surveys and participated in a facilitated structured dialog about if gay communities are changing, and if so, how they are changing. In all cities, the virtual gay community was identified as currently larger than the offline physical community. Most cities identified that while the gay population in their cities appeared stable or growing, the gay community appeared in decline. Measures included greater integration of heterosexuals into historically gay-identified neighborhoods and movement of gay persons into suburbs, decreased number of gay bars/clubs, less attendance at gay events, less volunteerism in gay or HIV/AIDS organizations, and the overall declining visibility of gay communities. Participants attributed structural change to multiple factors including gay neighborhood gentrification, achievement of civil rights, less discrimination, a vibrant virtual community, and changes in drug use. Consistent with social assimilation, gay infrastructure, visibility, and community identification appears to be decreasing across cities. HIV prevention planning, interventions, treatment services, and policies need to be re-conceptualized for MSM in the future. Four recommendations for future HIV prevention and research are detailed.

Spectral methods for the detection of network community structure: a comparative analysis

International Nuclear Information System (INIS)

Shen, Hua-Wei; Cheng, Xue-Qi

2010-01-01

Spectral analysis has been successfully applied to the detection of community structure of networks, respectively being based on the adjacency matrix, the standard Laplacian matrix, the normalized Laplacian matrix, the modularity matrix, the correlation matrix and several other variants of these matrices. However, the comparison between these spectral methods is less reported. More importantly, it is still unclear which matrix is more appropriate for the detection of community structure. This paper answers the question by evaluating the effectiveness of these five matrices against benchmark networks with heterogeneous distributions of node degree and community size. Test results demonstrate that the normalized Laplacian matrix and the correlation matrix significantly outperform the other three matrices at identifying the community structure of networks. This indicates that it is crucial to take into account the heterogeneous distribution of node degree when using spectral analysis for the detection of community structure. In addition, to our surprise, the modularity matrix exhibits very similar performance to the adjacency matrix, which indicates that the modularity matrix does not gain benefits from using the configuration model as a reference network with the consideration of the node degree heterogeneity

Spatial variation in the parasite communities and genomic structure of urban rats in New York City.

Science.gov (United States)

Angley, L P; Combs, M; Firth, C; Frye, M J; Lipkin, I; Richardson, J L; Munshi-South, J

2018-02-01

Brown rats (Rattus norvegicus) are a globally distributed pest. Urban habitats can support large infestations of rats, posing a potential risk to public health from the parasites and pathogens they carry. Despite the potential influence of rodent-borne zoonotic diseases on human health, it is unclear how urban habitats affect the structure and transmission dynamics of ectoparasite and microbial communities (all referred to as "parasites" hereafter) among rat colonies. In this study, we use ecological data on parasites and genomic sequencing of their rat hosts to examine associations between spatial proximity, genetic relatedness and the parasite communities associated with 133 rats at five sites in sections of New York City with persistent rat infestations. We build on previous work showing that rats in New York carry a wide variety of parasites and report that these communities differ significantly among sites, even across small geographical distances. Ectoparasite community similarity was positively associated with geographical proximity; however, there was no general association between distance and microbial communities of rats. Sites with greater overall parasite diversity also had rats with greater infection levels and parasite species richness. Parasite community similarity among sites was not linked to genetic relatedness of rats, suggesting that these communities are not associated with genetic similarity among host individuals or host dispersal among sites. Discriminant analysis identified site-specific associations of several parasite species, suggesting that the presence of some species within parasite communities may allow researchers to determine the sites of origin for newly sampled rats. The results of our study help clarify the roles that colony structure and geographical proximity play in determining the ecology of R. norvegicus as a significant urban reservoir of zoonotic diseases. Our study also highlights the spatial variation present in urban

Exponential random graph models for networks with community structure.

Science.gov (United States)

Fronczak, Piotr; Fronczak, Agata; Bujok, Maksymilian

2013-09-01

Although the community structure organization is an important characteristic of real-world networks, most of the traditional network models fail to reproduce the feature. Therefore, the models are useless as benchmark graphs for testing community detection algorithms. They are also inadequate to predict various properties of real networks. With this paper we intend to fill the gap. We develop an exponential random graph approach to networks with community structure. To this end we mainly built upon the idea of blockmodels. We consider both the classical blockmodel and its degree-corrected counterpart and study many of their properties analytically. We show that in the degree-corrected blockmodel, node degrees display an interesting scaling property, which is reminiscent of what is observed in real-world fractal networks. A short description of Monte Carlo simulations of the models is also given in the hope of being useful to others working in the field.

Variation of phytoplankton community structure from the Pearl River estuary to South China Sea.

Science.gov (United States)

Jiang, Zhao-Yu; Wang, You-Shao; Cheng, Hao; Sun, Cui-Ci; Wu, Mei-Lin

2015-10-01

The Pearl River is located in the northern part of South China Sea. The environment of the Pearl River estuary (PRE) is significantly impacted by nutrients from anthropogenic activities. Along the anthropogenic pollution gradient from the PRE to South China Sea, the phylogenetic diversity and biomass of phytoplankton was examined in relation to physic-chemical variables. The richness of rbcL gene was higher in the open sea than the estuary, while the concentration of chlorophyll a (Chl a) was higher in the estuary than in the open sea. The cluster analysis of the sequences data resulted in seven phytoplankton community types and the dominant species of phytoplankton changed from Cryptophytes and Diatoms to Prymnesiophytes and Diatoms along the gradient. The community structure of phytoplankton was shaped by nutrients and salinity. The phytoplankton biomass was significantly positively affected by phosphorus, nitrite and ammonium (P < 0.01) but negatively by salinity (P < 0.05); the phytoplankton diversity was highly positively affected by salinity (P < 0.05) but negatively by silicate and nitrate (P < 0.01; P < 0.05, respectively). Anthropogenic activities played a critical role in the phytoplankton distribution and biomass of the study area. Further research is necessary to reveal the influence mechanism of environmental factors on the phytoplankton.

Regional factors rather than forest type drive the community structure of soil living oribatid mites (Acari, Oribatida).

Science.gov (United States)

Erdmann, Georgia; Scheu, Stefan; Maraun, Mark

2012-06-01

Most European forests are managed by humans. However, the manner and intensity of management vary. While the effect of forest management on above-ground communities has been investigated in detail, effects on the below-ground fauna remain poorly understood. Oribatid mites are abundant microarthropods in forest soil and important decomposers in terrestrial ecosystems. Here, we investigated the effect of four forest types (i.e., managed coniferous forests; 30 and 70 years old managed beech forests; natural beech forests) on the density, diversity and community structure of oribatid mites (Acari). The study was replicated at three regions in Germany: the Swabian Alb, the Hainich and the Schorfheide. To relate changes in oribatid mite community structure to environmental factors, litter mass, pH, C and N content of litter, fine roots and C content of soil were measured. Density of oribatid mites was highest in the coniferous forests and decreased in the order 30 years old, 70 years old, and natural beech forests. Mass of the litter layer and density of oribatid mites were strongly correlated indicating that the litter layer is an important factor regulating oribatid mite densities. Diversity of oribatid mites was little affected by forest type indicating that they harbor similar numbers of niches. Species composition differed between the forest types, suggesting different types of niches. The community structure of oribatid mites differed more strongly between the three regions than between the forest types indicating that regional factors are more important than effects associated with forest type.

Effects of acute {gamma}-irradiation on community structure of the aquatic microbial microcosm

Energy Technology Data Exchange (ETDEWEB)

Fuma, Shoichi, E-mail: fuma@nirs.go.j [Environmental Radiation Effects Research Group, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Ishii, Nobuyoshi; Takeda, Hiroshi [Environmental Radiation Effects Research Group, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Doi, Kazutaka; Kawaguchi, Isao [Regulatory Sciences Research Group, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Shikano, Shuichi [Center for Northeast Asian Studies, Tohoku University, 41 Kawauchi, Aoba-ku, Sendai, Miyagi 980-8576 (Japan); Tanaka, Nobuyuki [Marine Environment Section, Water and Soil Environment Division, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506 (Japan); Inamori, Yuhei [Faculty of Symbiotic Systems Science, Fukushima University, 1 Kanayagawa, Fukushima 960-1296 (Japan)

2010-11-15

To characterise indirect effects of ionising radiation on aquatic microbial communities, effects of acute {gamma}-irradiation were investigated in a microcosm consisting of populations of green algae (Chlorella sp. and Scenedesmus sp.) and a blue-green alga (Tolypothrix sp.) as producer; a ciliate protozoan (Cyclidium glaucoma), rotifers (Lecane sp. and Philodina sp.) and an oligochaete (Aeolosoma hemprichi) as consumer; and more than four species of bacteria as decomposers. Population changes in the constituent organisms were observed over 160 days after irradiation. Prokaryotic community structure was also examined by denaturing gradient gel electrophoresis (DGGE) of 16S rDNA. Principle response curve analysis revealed that the populations of the microcosm as a whole were not significantly affected at 100 Gy while they were adversely affected at 500-5000 Gy in a dose-dependent manner. However, some effects on each population, including each bacterial population detected by DGGE, did not depend on radiation doses, and some populations in the irradiated microcosm were larger than those of the control. These unexpected results are regarded as indirect effects through interspecies interactions, and possible mechanisms are proposed originating from population changes in other organisms co-existing in the microcosm. For example, some indirect effects on consumers and decomposers likely arose from interspecies competition within each trophic level. It is also likely that prey-predator relationships between producers and consumers caused some indirect effects on producers.

Factors structuring the phytoplankton community in the upwelling site off El Loa River in northern Chile

Science.gov (United States)

Herrera, Liliana; Escribano, Ruben

2006-06-01

Understanding processes affecting the structure of the autotrophic community in marine ecosystems is relevant because species-dependent characters may affect productivity and carbon fluxes of the ocean. In this work, we studied the influence of oceanographic variability on phytoplankton species composition at a coastal upwelling site off northern Chile. Four seasonal cruises carried out during 2003 off El Loa River (21°S) showed that upwelling occurs year-round supporting a large number of diatoms, dinoflagellates, naked nanoflagellates, and silicoflagellates. The analysis of species composition showed that changes in the structure of the autotrophic community are expressed both in abundance and in differences in species assemblages. These changes occurred not only over the seasonal scale but also over the spatial pattern of distribution, and they correlated well to temporal variability of upwelling and spatial variation of upwelling conditions over the cross-shelf axis. A K-means clustering and principal component analyses showed that species assemblages can be represented by few dominant species strongly coupled to alternate upwelling vs. non-upwelling conditions. Both conditions are well defined, and mostly explained by changes in depth of the upper boundary of the oxygen minimum zone (OMZ) (a prominent feature in northern Chile), surface temperature and water column stratification. Abundance of dominant phytoplankton species were strongly correlated to both OMZ depth and water column stratification. Processes through which OMZ depth might influence species abundance and composition are unknown, although they may relate to changes in redox conditions which affect the nutrient field. Another explanation may relate to changes in grazing pressure derived from the effect of low oxygen water on zooplankton vertical distribution.

Microbial Community-Level Physiological Profiles (CLPP) and herbicide mineralization potential in groundwater affected by agricultural land use

DEFF Research Database (Denmark)

Janniche, Gry Sander; Spliid, Henrik; Albrechtsen, Hans-Jørgen

2012-01-01

Diffuse groundwater pollution from agricultural land use may impact the microbial groundwater community, which was investigated as Community-Level Physiological Profiles (CLPP) using EcoPlate™. Water was sampled from seven piezometers and a spring in a small agricultural catchment with diffuse......-galacturonic acid, tween 40, and 4-hydroxy benzoic acid as substrates, whereas none preferred 2-hydroxy benzoic acid, α-d-lactose, d,l-α-glycerol phosphate, α-ketobutyric acid, l-threonine and glycyl-l-glutamic acid. Principal Component Analysis of the CLPP's clustered the most agriculturally affected groundwater...... samples, indicating that the agricultural land use affects the groundwater microbial communities. Furthermore, the ability to mineralize atrazine and isoproturon, which have been used in the catchment, was also associated with this cluster....

The effect of biochar and its interaction with the earthworm Pontoscolex corethrurus on soil microbial community structure in tropical soils.

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Jorge Paz-Ferreiro

Full Text Available Biochar effects on soil microbial abundance and community structure are keys for understanding the biogeochemical cycling of nutrients and organic matter turnover, but are poorly understood, in particular in tropical areas. We conducted a greenhouse experiment in which we added biochars produced from four different feedstocks [sewage sludge (B1, deinking sewage sludge (B2, Miscanthus (B3 and pine wood (B4] at a rate of 3% (w/w to two tropical soils (an Acrisol and a Ferralsol planted with proso millet (Panicum milliaceum L.. The interactive effect of the addition of earthworms was also addressed. For this purpose we utilized soil samples from pots with or without the earthworm Pontoscolex corethrurus, which is a ubiquitous earthworm in tropical soils. Phospholipid fatty acid (PLFA measurements showed that biochar type, soil type and the presence of earthworms significantly affected soil microbial community size and structure. In general, biochar addition affected fungal but not bacterial populations. Overall, biochars rich in ash (B1 and B2 resulted in a marked increase in the fungi to bacteria ratio, while this ratio was unaltered after addition of biochars with a high fixed carbon content (B3 and B4. Our study remarked the contrasting effect that both, biochar prepared from different materials and macrofauna, can have on soil microbial community. Such changes might end up with ecosystem-level effects.

The Impact of Green Open Space on Community Attachment—A Case Study of Three Communities in Beijing

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Yuemei Zhu

2017-04-01

Full Text Available With the development of urbanization in China, the quality of urban life and community attachment have attracted increasing attention of the governments and society. Existing research on community attachment has mainly examined how individual characteristics affect community attachment, such as their length of residence and socioeconomic status. However, some scholars have become interested in exploring the effects of green open space on community attachment. This research examined whether the distribution of green open space in communities had significant effects on community attachment, and both the impact and path were also investigated. Through a questionnaire survey, relevant data in three communities of Beijing were collected. The impact of green open space layout on community attachment was evaluated by using hierarchical regression, and the impact path was examined by using a structural equation model. The results showed that green open space in a community had significant effects on the community attachment, with centralized green open space layout having a greater effect than that of dispersed green open space. Moreover, the more complex the shape of green open space is, the greater the impact is. The degree of satisfaction with the green open space had direct effects on the community attachment. The accessibility and perceived area of green open space could indirectly have an impact on the community attachment by affecting the degree of satisfaction with the green open space. Nevertheless, residents’ perceived importance of green open space could affect the community attachment directly and indirectly, as it affects the degree of satisfaction.

[Effect of ground mulch managements on soil bacterial community structure and diversity in the non-irrigated apple orchard in Weibei Loess Plateau].

Science.gov (United States)

Chen, Yuexing; Wen, Xiaoxia; Sun, Yulin; Zhang, Junli; Lin, Xiaoli; Liao, Yuncheng

2015-07-04

We studied the changes in soil bacterial communities induced by ground mulch managements at different apple growth periods. We adopted the denaturing gradient gel electrophoresis (DGGE) with PCR-amplified 16S rRNA fragments to determine soil bacterial community structure and diversity. Soil bacterial community structure with different ground mulch managements were significantly different. Both the mulch management strategies and apple growth periods affected the predominant groups and their abundance in soil bacterial communities. Grass mulch and cornstalk mulch treatments had higher bacterial diversity and richness than the control at young fruit period and fruit expanding period, whereas film mulch treatment had no significant difference compared with the control. During mature period, bacterial diversity in the control reached its maximum, which may be ascribed to the rapid growth and reproduction of the r-selection bacteria. The clustering and detrended correspondence analysis revealed that differences in soil bacterial communities were closely correlated to apple growth periods and ground mulch managements. Soil samples from the grass mulch and cornstalk mulch treatments clustered together while those mulched with plastic film treatment were similar to the control. The most abundant phylum in soil bacterial community was Proteobacteria followed by Bacteroidetes. Some other phyla were also detected, such as Acidobacteria, Firmicutes, Actinobacteria and Chloroflexi. Mulching with plant (Grass/Cornstalk) had great effects on soil bacterial community structure and enhanced the diversity while film mulch management had no significant effects.

Soil microbial community structure and nitrogen cycling responses to agroecosystem management and carbon substrate addition

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Berthrong, S. T.; Buckley, D. H.; Drinkwater, L. E.

2011-12-01

Fertilizer application in conventional agriculture leads to N saturation and decoupled soil C and N cycling, whereas organic practices, e.g. complex rotations and legume incorporation, often results in increased SOM and tightly coupled cycles of C and N. These legacy effects of management on soils likely affect microbial community composition and microbial process rates. This project tested if agricultural management practices led to distinct microbial communities and if those communities differed in ability to utilize labile plant carbon substrates and to produce more plant available N. We addressed several specific questions in this project. 1) Do organic and conventional management legacies on similar soils produce distinct soil bacterial and fungal community structures and abundances? 2) How do these microbial community structures change in response to carbon substrate addition? 3) How do the responses of the microbial communities influence N cycling? To address these questions we conducted a laboratory incubation of organically and conventionally managed soils. We added C-13 labelled glucose either in one large dose or several smaller pulses. We extracted genomic DNA from soils before and after incubation for TRFLP community fingerprinting. We measured C in soil pools and respiration and N in soil extracts and leachates. Management led to different compositions of bacteria and fungi driven by distinct components in organic soils. Biomass did not differ across treatments indicating that differences in cycling were due to composition rather than abundance. C substrate addition led to convergence in bacterial communities; however management still strongly influenced the difference in communities. Fungal communities were very distinct between managements and plots with substrate addition not altering this pattern. Organic soils respired 3 times more of the glucose in the first week than conventional soils (1.1% vs 0.4%). Organic soils produced twice as much

Microbial community functional structure in response to antibiotics in pharmaceutical wastewater treatment systems.

Science.gov (United States)

Zhang, Yu; Xie, Jianping; Liu, Miaomiao; Tian, Zhe; He, Zhili; van Nostrand, Joy D; Ren, Liren; Zhou, Jizhong; Yang, Min

2013-10-15

It is widely demonstrated that antibiotics in the environment affect microbial community structure. However, direct evidence regarding the impacts of antibiotics on microbial functional structures in wastewater treatment systems is limited. Herein, a high-throughput functional gene array (GeoChip 3.0) in combination with quantitative PCR and clone libraries were used to evaluate the microbial functional structures in two biological wastewater treatment systems, which treat antibiotic production wastewater mainly containing oxytetracycline. Despite the bacteriostatic effects of antibiotics, the GeoChip detected almost all key functional gene categories, including carbon cycling, nitrogen cycling, etc., suggesting that these microbial communities were functionally diverse. Totally 749 carbon-degrading genes belonging to 40 groups (24 from bacteria and 16 from fungi) were detected. The abundance of several fungal carbon-degrading genes (e.g., glyoxal oxidase (glx), lignin peroxidase or ligninase (lip), manganese peroxidase (mnp), endochitinase, exoglucanase_genes) was significantly correlated with antibiotic concentrations (Mantel test; P functional genes have been enhanced by the presence of antibiotics. However, from the fact that the majority of carbon-degrading genes were derived from bacteria and diverse antibiotic resistance genes were detected in bacteria, it was assumed that many bacteria could survive in the environment by acquiring antibiotic resistance and may have maintained the position as a main player in nutrient removal. Variance partitioning analysis showed that antibiotics could explain 24.4% of variations in microbial functional structure of the treatment systems. This study provides insights into the impacts of antibiotics on microbial functional structure of a unique system receiving antibiotic production wastewater, and reveals the potential importance of the cooperation between fungi and bacteria with antibiotic resistance in maintaining the

Land use intensity controls actinobacterial community structure

Czech Academy of Sciences Publication Activity Database

Hill, P.; Krištůfek, Václav; Dijkhuizen, L.; Boddy, Ch.; Kroetsch, D.; van Elsas, J.D.

2011-01-01

Roč. 61, č. 2 (2011), s. 286-302 ISSN 0095-3628 R&D Projects: GA MŠk LC06066; GA MŠk 2B06154 Institutional research plan: CEZ:AV0Z60660521 Keywords : actinobacterial community structure * DNA * soils Subject RIV: EH - Ecology, Behaviour Impact factor: 2.912, year: 2011

Social structure affects mating competition in a damselfish

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Wacker, Sebastian; Ness, Miriam Horstad; Östlund-Nilsson, Sara; Amundsen, Trond

2017-12-01

The strength of mating competition and sexual selection varies over space and time in many animals. Such variation is typically driven by ecological and demographic factors, including adult sex ratio and consequent availability of mates. The spatial scale at which demographic factors affect mating competition and sexual selection may vary but is not often investigated. Here, we analyse variation in size and sex ratio of social groups, and how group structure affects mating competition, in the site-attached damselfish Chrysiptera cyanea. Site-attached reef fishes are known to show extensive intraspecific variation in social structure. Previous work has focused on species for which the size and dynamics of social groups are constrained by habitat, whereas species with group structure unconstrained by habitat have received little attention. Chrysiptera cyanea is such a species, with individuals occurring in spatial clusters that varied widely in size and sex ratio. Typically, only one male defended a nest in multi-male groups. Nest-holding males were frequently visited by mate-searching females, with more visits in groups with more females, suggesting that courtship and mating mostly occur within groups and that male mating success depends on the number of females in the group. Male-male aggression was frequent in multi-male groups but absent in single-male groups. These findings demonstrate that groups are distinct social units. In consequence, the dynamics of mating and reproduction are mainly a result of group structure, largely unaffected short term by overall population demography which would be important in open social systems. Future studies of the C. cyanea model system should analyse longer-term dynamics, including how groups are formed, how they vary in relation to density and time of season and how social structure affects sexual selection.

Microbial Community Structure of a Leachfield Soil: Response to Intermittent Aeration and Tetracycline Addition

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David A. Potts

2013-04-01

Full Text Available Soil-based wastewater treatment systems, or leachfields, rely on microbial processes for improving the quality of wastewater before it reaches the groundwater. These processes are affected by physicochemical system properties, such as O2 availability, and disturbances, such as the presence of antimicrobial compounds in wastewater. We examined the microbial community structure of leachfield mesocosms containing native soil and receiving domestic wastewater under intermittently-aerated (AIR and unaerated (LEACH conditions before and after dosing with tetracycline (TET. Community structure was assessed using phospholipid fatty acid analysis (PLFA, analysis of dominant phylotypes using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR–DGGE, and cloning and sequencing of 16S rRNA genes. Prior to dosing, the same PLFA biomarkers were found in soil from AIR and LEACH treatments, although AIR soil had a larger active microbial population and higher concentrations for nine of 32 PLFA markers found. AIR soil also had a larger number of dominant phylotypes, most of them unique to this treatment. Dosing of mesocosms with TET had a more marked effect on AIR than LEACH soil, reducing the size of the microbial population and the number and concentration of PLFA markers. Dominant phylotypes decreased by ~15% in response to TET in both treatments, although the AIR treatment retained a higher number of phylotypes than the LEACH treatment. Fewer than 10% of clones were common to both OPEN ACCESS Water 2013, 5 506 AIR and LEACH soil, and fewer than 25% of the clones from either treatment were homologous with isolates of known genus and species. These included human pathogens, as well as bacteria involved in biogeochemical transformations of C, N, S and metals, and biodegradation of various organic contaminants. Our results show that intermittent aeration has a marked effect on the size and structure of the microbial community that develops in

Soil Microbial Community Structure Evolution along Halophyte Succession in Bohai Bay Wetland

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Mingyang Cong

2014-01-01

Full Text Available It is urgent to recover Bohai Bay costal wetland ecosystem because of covering a large area of severe saline-alkali soil. To explore the relationship between halophyte herbaceous succession and microbial community structure, we chose four local communities which played an important role in improving soil microenvironment. We performed phospholipid fatty acid analysis, measured soil parameters, and evaluated shifts of microbial community structure. Results showed that microbial community structure changed significantly along succession and bacteria community was dominant. Total phospholipid fatty acid content increased in different successional stages but decreased with depth, with similar variations in bacterial and fungal biomass. Soil organic carbon and especially total nitrogen were positively correlated with microbial biomass. Colonization of pioneering salt-tolerant plants Suaeda glauca in saline-alkali bare land changed total soil microorganism content and composition. These results showed that belowground processes were strongly related with aboveground halophyte succession. Fungal/bacterial ratio, Gram-negative/Gram-positive bacteria ratio, total microbial biomass, and fungi and bacteria content could indicate the degree of succession stages in Bohai Bay wetland ecosystem. And also these findings demonstrated that microbial community biomass and composition evolved along with vegetation succession environmental variables.

Impact of Seasonal Hypoxia on Activity and Community Structure of Chemolithoautotrophic Bacteria in a Coastal Sediment.

Science.gov (United States)

Lipsewers, Yvonne A; Vasquez-Cardenas, Diana; Seitaj, Dorina; Schauer, Regina; Hidalgo-Martinez, Silvia; Sinninghe Damsté, Jaap S; Meysman, Filip J R; Villanueva, Laura; Boschker, Henricus T S

2017-05-15

multidisciplinary investigation of the sediments in a seasonally hypoxic coastal basin confirms this hypothesis. Our data show that bacterial community structure and chemolithoautotrophic activity varied with the seasonal depletion of oxygen. Unexpectedly, the dark carbon fixation was also dependent on the dominant microbial pathway of sulfur oxidation occurring in the sediment (i.e., canonical sulfur oxidation, electrogenic sulfur oxidation by cable bacteria, and sulfide oxidation coupled to nitrate reduction by Beggiatoaceae ). These results suggest that a complex niche partitioning within the sulfur-oxidizing bacterial community additionally affects the chemolithoautotrophic community of seasonally hypoxic sediments. Copyright © 2017 American Society for Microbiology.

Changes in microbial community structure in the wake of Hurricanes Katrina and Rita.

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Amaral-Zettler, Linda A; Rocca, Jennifer D; Lamontagne, Michael G; Dennett, Mark R; Gast, Rebecca J

2008-12-15

Hurricanes have the potential to alter the structures of coastal ecosystems and generate pathogen-laden floodwaters thatthreaten public health. To examine the impact of hurricanes on urban systems, we compared microbial community structures in samples collected after Hurricane Katrina and before and after Hurricane Rita. We extracted environmental DNA and sequenced small-subunit rRNA (SSU rRNA) gene clone libraries to survey microbial communities in floodwater, water, and sediment samples collected from Lake Charles, Lake Pontchartrain, the 17th Street and Industrial Canals in New Orleans, and raw sewage. Correspondence analysis showed that microbial communities associated with sediments formed one cluster while communities associated with lake and Industrial Canal water formed a second. Communities associated with water from the 17th Street Canal and floodwaters collected in New Orleans showed similarity to communities in raw sewage and contained a number of sequences associated with possible pathogenic microbes. This suggests that a distinct microbial community developed in floodwaters following Hurricane Katrina and that microbial community structures as a whole might be sensitive indicators of ecosystem health and serve as "sentinels" of water quality in the environment.

Among-Population Variation in Microbial Community Structure in the Floral Nectar of the Bee-Pollinated Forest Herb Pulmonaria officinalis L

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Jacquemyn, Hans; Lenaerts, Marijke; Brys, Rein; Willems, Kris; Honnay, Olivier; Lievens, Bart

2013-01-01

Background Microbial communities in floral nectar have been shown to be characterized by low levels of species diversity, yet little is known about among-plant population variation in microbial community composition. Methodology/Principal Findings We investigated the microbial community structure (yeasts and bacteria) in floral nectar of ten fragmented populations of the bee-pollinated forest herb Pulmonaria officinalis. We also explored possible relationships between plant population size and microbial diversity in nectar, and related microbial community composition to the distance separating plant populations. Culturable bacteria and yeasts occurring in the floral nectar of a total of 100 plant individuals were isolated and identified by partially sequencing the 16S rRNA gene and D1/D2 domains of the 26S rRNA gene, respectively. A total of 9 and 11 yeast and 28 and 39 bacterial OTUs was found, taking into account a 3% (OTU0.03) and 1% sequence dissimilarity cut-off (OTU0.01). OTU richness at the plant population level (i.e. the number of OTUs per population) was low for yeasts (mean: 1.7, range: 0–4 OTUs0.01/0.03 per population), whereas on average 6.9 (range: 2–13) OTUs0.03 and 7.9 (range 2–16) OTUs0.01 per population were found for bacteria. Both for yeasts and bacteria, OTU richness was not significantly related to plant population size. Similarity in community composition among populations was low (average Jaccard index: 0.14), and did not decline with increasing distance between populations. Conclusions/Significance We found low similarity in microbial community structure among populations, suggesting that the assembly of nectar microbiota is to a large extent context-dependent. Although the precise factors that affect variation in microbial community structure in floral nectar require further study, our results indicate that both local and regional processes may contribute to among-population variation in microbial community structure in nectar. PMID

Macrobenthic community structure of coastal Arabian Sea during the fall intermonsoon

Digital Repository Service at National Institute of Oceanography (India)

Ingole, B.S.; Gaonkar, U.V.; Deshmukh, A.; Mukherjee, I.; Sivadas, S.K.; Gophane, A.

that the FIM period is critical in structuring the coastal benthic community Results indicated Coscinodiscus sp and Thalassiosira sp were dominant in the phytoplankton and the microphytobenthos community Zooplankton was dominated by small sized calanoid...

Impacts of multiwalled carbon nanotubes on nutrient removal from wastewater and bacterial community structure in activated sludge.

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Reti Hai

Full Text Available BACKGROUND: The increasing use of multiwalled carbon nanotubes (MWCNTs will inevitably lead to the exposure of wastewater treatment facilities. However, knowledge of the impacts of MWCNTs on wastewater nutrient removal and bacterial community structure in the activated sludge process is sparse. AIMS: To investigate the effects of MWCNTs on wastewater nutrient removal, and bacterial community structure in activated sludge. METHODS: Three triplicate sequencing batch reactors (SBR were exposed to wastewater which contained 0, 1, and 20 mg/L MWCNTs. MiSeq sequencing was used to investigate the bacterial community structures in activated sludge samples which were exposed to different concentrations of MWCNTs. RESULTS: Exposure to 1 and 20 mg/L MWCNTs had no acute (1 day impact on nutrient removal from wastewater. After long-term (180 days exposure to 1 mg/L MWCNTs, the average total nitrogen (TN removal efficiency was not significantly affected. TN removal efficiency decreased from 84.0% to 71.9% after long-term effects of 20 mg/L MWCNTs. After long-term exposure to 1 and 20 mg/L MWCNTs, the total phosphorus removal efficiencies decreased from 96.8% to 52.3% and from 98.2% to 34.0% respectively. Further study revealed that long-term exposure to 20 mg/L MWCNTs inhibited activities of ammonia monooxygenase and nitrite oxidoreductase. Long-term exposure to 1 and 20 mg/L MWCNTs both inhibited activities of exopolyphosphatase and polyphosphate kinase. MiSeq sequencing data indicated that 20 mg/L MWCNTs significantly decreased the diversity of bacterial community in activated sludge. Long-term exposure to 1 and 20 mg/L MWCNTs differentially decreased the abundance of nitrifying bacteria, especially ammonia-oxidizing bacteria. The abundance of PAOs was decreased after long-term exposure to 20 mg/L MWCNTs. The abundance of glycogen accumulating organisms (GAOs was increased after long-term exposure to 1 mg/L MWCNTs. CONCLUSION: MWCNTs have adverse effects on

Bacterial diversity and community structure in lettuce soil are shifted by cultivation time

Science.gov (United States)

Liu, Yiqian; Chang, Qing; Guo, Xu; Yi, Xinxin

2017-08-01

Compared with cereal production, vegetable production usually requires a greater degree of management and larger input of nutrients and irrigation, but these systems are not sustainable in the long term. This study aimed to what extent lettuce determine the bacterial community composition in the soil, during lettuce cultivation, pesticides and fertilizers were not apply to soil. Soil samples were collected from depths of 0-20cm and 20-40cm. A highthroughput sequencing approach was employed to investigate bacterial communities in lettuce-cultivated soil samples in a time-dependent manner. The dominant bacteria in the lettuce soil samples were mainly Proteobacteria, Actinobacteria, Chloroflexi, Nitrospirae, Firmicutes, Acidobacteria, Bacteroidetes, Verrucomicrobia, Planctomycetes, Gemmatimo nadetes, Cyanobacteria. Proteobacteria was the most abundant phylum in the 6 soil samples. The relative abundance of Acidobacteria, Firmicutes, Bacteroidetes, Verrucomicrobia and Cyanobacteria decreased through time of lettuce cultivation, but the relative abundance of Proteobacteria, Actinobacteria, Gemmatimonadetes, Chloroflexi, Planctomycetes and Nitrospirae increased over time. In the 0-20cm depth group and the 20-40cm depth soil, a similar pattern was observed that the percentage number of only shared OTUs between the early and late stage was lower than that between the early and middle stage soil, the result showed that lettuce growth can affect structure of soil bacterial communities.

Host Ecology Rather Than Host Phylogeny Drives Amphibian Skin Microbial Community Structure in the Biodiversity Hotspot of Madagascar

Science.gov (United States)

Bletz, Molly C.; Archer, Holly; Harris, Reid N.; McKenzie, Valerie J.; Rabemananjara, Falitiana C. E.; Rakotoarison, Andolalao; Vences, Miguel

2017-01-01

Host-associated microbiotas of vertebrates are diverse and complex communities that contribute to host health. In particular, for amphibians, cutaneous microbial communities likely play a significant role in pathogen defense; however, our ecological understanding of these communities is still in its infancy. Here, we take advantage of the fully endemic and locally species-rich amphibian fauna of Madagascar to investigate the factors structuring amphibian skin microbiota on a large scale. Using amplicon-based sequencing, we evaluate how multiple host species traits and site factors affect host bacterial diversity and community structure. Madagascar is home to over 400 native frog species, all of which are endemic to the island; more than 100 different species are known to occur in sympatry within multiple rainforest sites. We intensively sampled frog skin bacterial communities, from over 800 amphibians from 89 species across 30 sites in Madagascar during three field visits, and found that skin bacterial communities differed strongly from those of the surrounding environment. Richness of bacterial operational taxonomic units (OTUs) and phylogenetic diversity differed among host ecomorphs, with arboreal frogs exhibiting lower richness and diversity than terrestrial and aquatic frogs. Host ecomorphology was the strongest factor influencing microbial community structure, with host phylogeny and site parameters (latitude and elevation) explaining less but significant portions of the observed variation. Correlation analysis and topological congruency analyses revealed little to no phylosymbiosis for amphibian skin microbiota. Despite the observed geographic variation and low phylosymbiosis, we found particular OTUs that were differentially abundant between particular ecomorphs. For example, the genus Pigmentiphaga (Alcaligenaceae) was significantly enriched on arboreal frogs, Methylotenera (Methylophilaceae) was enriched on aquatic frogs, and Agrobacterium (Rhizobiaceae

Host Ecology Rather Than Host Phylogeny Drives Amphibian Skin Microbial Community Structure in the Biodiversity Hotspot of Madagascar

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Molly C. Bletz

2017-08-01

Full Text Available Host-associated microbiotas of vertebrates are diverse and complex communities that contribute to host health. In particular, for amphibians, cutaneous microbial communities likely play a significant role in pathogen defense; however, our ecological understanding of these communities is still in its infancy. Here, we take advantage of the fully endemic and locally species-rich amphibian fauna of Madagascar to investigate the factors structuring amphibian skin microbiota on a large scale. Using amplicon-based sequencing, we evaluate how multiple host species traits and site factors affect host bacterial diversity and community structure. Madagascar is home to over 400 native frog species, all of which are endemic to the island; more than 100 different species are known to occur in sympatry within multiple rainforest sites. We intensively sampled frog skin bacterial communities, from over 800 amphibians from 89 species across 30 sites in Madagascar during three field visits, and found that skin bacterial communities differed strongly from those of the surrounding environment. Richness of bacterial operational taxonomic units (OTUs and phylogenetic diversity differed among host ecomorphs, with arboreal frogs exhibiting lower richness and diversity than terrestrial and aquatic frogs. Host ecomorphology was the strongest factor influencing microbial community structure, with host phylogeny and site parameters (latitude and elevation explaining less but significant portions of the observed variation. Correlation analysis and topological congruency analyses revealed little to no phylosymbiosis for amphibian skin microbiota. Despite the observed geographic variation and low phylosymbiosis, we found particular OTUs that were differentially abundant between particular ecomorphs. For example, the genus Pigmentiphaga (Alcaligenaceae was significantly enriched on arboreal frogs, Methylotenera (Methylophilaceae was enriched on aquatic frogs, and Agrobacterium

Host Ecology Rather Than Host Phylogeny Drives Amphibian Skin Microbial Community Structure in the Biodiversity Hotspot of Madagascar.

Science.gov (United States)

Bletz, Molly C; Archer, Holly; Harris, Reid N; McKenzie, Valerie J; Rabemananjara, Falitiana C E; Rakotoarison, Andolalao; Vences, Miguel

2017-01-01

Host-associated microbiotas of vertebrates are diverse and complex communities that contribute to host health. In particular, for amphibians, cutaneous microbial communities likely play a significant role in pathogen defense; however, our ecological understanding of these communities is still in its infancy. Here, we take advantage of the fully endemic and locally species-rich amphibian fauna of Madagascar to investigate the factors structuring amphibian skin microbiota on a large scale. Using amplicon-based sequencing, we evaluate how multiple host species traits and site factors affect host bacterial diversity and community structure. Madagascar is home to over 400 native frog species, all of which are endemic to the island; more than 100 different species are known to occur in sympatry within multiple rainforest sites. We intensively sampled frog skin bacterial communities, from over 800 amphibians from 89 species across 30 sites in Madagascar during three field visits, and found that skin bacterial communities differed strongly from those of the surrounding environment. Richness of bacterial operational taxonomic units (OTUs) and phylogenetic diversity differed among host ecomorphs, with arboreal frogs exhibiting lower richness and diversity than terrestrial and aquatic frogs. Host ecomorphology was the strongest factor influencing microbial community structure, with host phylogeny and site parameters (latitude and elevation) explaining less but significant portions of the observed variation. Correlation analysis and topological congruency analyses revealed little to no phylosymbiosis for amphibian skin microbiota. Despite the observed geographic variation and low phylosymbiosis, we found particular OTUs that were differentially abundant between particular ecomorphs. For example, the genus Pigmentiphaga (Alcaligenaceae) was significantly enriched on arboreal frogs, Methylotenera (Methylophilaceae) was enriched on aquatic frogs, and Agrobacterium (Rhizobiaceae

Internal tides affect benthic community structure in an energetic submarine canyon off SW Taiwan

Science.gov (United States)

Liao, Jian-Xiang; Chen, Guan-Ming; Chiou, Ming-Da; Jan, Sen; Wei, Chih-Lin

2017-07-01

Submarine canyons are major conduits of terrestrial and shelf organic matter, potentially benefiting the seafloor communities in the food-deprived deep sea; however, strong bottom currents driven by internal tides and the potentially frequent turbidity currents triggered by storm surges, river flooding, and earthquakes may negatively impact the benthos. In this study, we investigated the upper Gaoping Submarine Canyon (GPSC), a high-sediment-yield canyon connected to a small mountain river (SMR) off southwest (SW) Taiwan. By contrasting the benthic meiofaunal and macrofaunal communities within and outside the GPSC, we examined how food supplies and disturbance influenced the benthic community assemblages. The benthic communities in the upper GPSC were mainly a nested subset of the adjacent slope assemblages. Several meiofaunal (e.g. ostracods) and macrofaunal taxa (e.g. peracarid crustaceans and mollusks) that typically occurred on the slope were lost from the canyon. The polychaete families switched from diverse feeding guilds on the slope to motile subsurface deposit feeders dominant in the canyon. The diminishing of epibenthic peracarids and proliferation of deep burrowing polychaetes in the GPSC resulted in macrofauna occurring largely within deeper sediment horizons in the canyon than on the slope. The densities and numbers of taxa were depressed with distinct and more variable composition in the canyon than on the adjacent slope. Both the densities and numbers of taxa were negatively influenced by internal tide flushing and positively influenced by food availability; however, the internal tides also negatively influenced the food supplies. While the meiofauna and macrofauna densities were both depressed by the extreme physical conditions in the GPSC, only the macrofaunal densities increased with depth in the canyon, presumably related to increased frequency and intensity of disturbance toward the canyon head. The population densities of meiofauna, on the

A game theoretic algorithm to detect overlapping community structure in networks

Science.gov (United States)

Zhou, Xu; Zhao, Xiaohui; Liu, Yanheng; Sun, Geng

2018-04-01

Community detection can be used as an important technique for product and personalized service recommendation. A game theory based approach to detect overlapping community structure is introduced in this paper. The process of the community formation is converted into a game, when all agents (nodes) cannot improve their own utility, the game process will be terminated. The utility function is composed of a gain and a loss function and we present a new gain function in this paper. In addition, different from choosing action randomly among join, quit and switch for each agent to get new label, two new strategies for each agent to update its label are designed during the game, and the strategies are also evaluated and compared for each agent in order to find its best result. The overlapping community structure is naturally presented when the stop criterion is satisfied. The experimental results demonstrate that the proposed algorithm outperforms other similar algorithms for detecting overlapping communities in networks.

Interlinking backscatter, grain size and benthic community structure

Science.gov (United States)

McGonigle, Chris; Collier, Jenny S.

2014-06-01

The relationship between acoustic backscatter, sediment grain size and benthic community structure is examined using three different quantitative methods, covering image- and angular response-based approaches. Multibeam time-series backscatter (300 kHz) data acquired in 2008 off the coast of East Anglia (UK) are compared with grain size properties, macrofaunal abundance and biomass from 130 Hamon and 16 Clamshell grab samples. Three predictive methods are used: 1) image-based (mean backscatter intensity); 2) angular response-based (predicted mean grain size), and 3) image-based (1st principal component and classification) from Quester Tangent Corporation Multiview software. Relationships between grain size and backscatter are explored using linear regression. Differences in grain size and benthic community structure between acoustically defined groups are examined using ANOVA and PERMANOVA+. Results for the Hamon grab stations indicate significant correlations between measured mean grain size and mean backscatter intensity, angular response predicted mean grain size, and 1st principal component of QTC analysis (all p PERMANOVA for the Hamon abundance shows benthic community structure was significantly different between acoustic groups for all methods (p ≤ 0.001). Overall these results show considerable promise in that more than 60% of the variance in the mean grain size of the Clamshell grab samples can be explained by mean backscatter or acoustically-predicted grain size. These results show that there is significant predictive capacity for sediment characteristics from multibeam backscatter and that these acoustic classifications can have ecological validity.

Structural Variation in the Bacterial Community Associated with Airborne Particulate Matter in Beijing, China, during Hazy and Nonhazy Days.

Science.gov (United States)

Yan, Dong; Zhang, Tao; Su, Jing; Zhao, Li-Li; Wang, Hao; Fang, Xiao-Mei; Zhang, Yu-Qin; Liu, Hong-Yu; Yu, Li-Yan

2018-05-01

The structural variation of the bacterial community associated with particulate matter (PM) was assessed in an urban area of Beijing during hazy and nonhazy days. Sampling for different PM fractions (PM 2.5 [airborne bacterial community in these samples was analyzed using the Illumina MiSeq platform with bacterium-specific primers targeting the 16S rRNA gene. A total of 1,707,072 reads belonging to 6,009 operational taxonomic units were observed. The airborne bacterial community composition was significantly affected by PM fractions ( R = 0.157, P airborne bacterial community composition. Only six genera increased across PM 10 samples ( Dokdonella , Caenimonas , Geminicoccus , and Sphingopyxis ) and PM 2.5 samples ( Cellulomonas and Rhizobacter ), while a large number of taxa significantly increased in total suspended particulate samples, such as Paracoccus , Kocuria , and Sphingomonas Network analysis indicated that Paracoccus , Rubellimicrobium , Kocuria , and Arthrobacter were the key genera in the airborne PM samples. Overall, the findings presented here suggest that diverse airborne bacterial communities are associated with PM and provide further understanding of bacterial community structure in the atmosphere during hazy and nonhazy days. IMPORTANCE The results presented here represent an analysis of the airborne bacterial community associated with particulate matter (PM) and advance our understanding of the structural variation of these communities. We observed a shift in bacterial community composition with PM fractions but no significant difference with haze levels. This may be because the bacterial differences are obscured by high bacterial diversity in the atmosphere. However, we also observed that a few genera (such as Methylobacillus , Tumebacillus , and Desulfurispora ) increased significantly on heavy-haze days. In addition, Paracoccus , Rubellimicrobium , Kocuria , and Arthrobacter were the key genera in the airborne PM samples. Accurate and real

Comparison and validation of community structures in complex networks

Science.gov (United States)

Gustafsson, Mika; Hörnquist, Michael; Lombardi, Anna

2006-07-01

The issue of partitioning a network into communities has attracted a great deal of attention recently. Most authors seem to equate this issue with the one of finding the maximum value of the modularity, as defined by Newman. Since the problem formulated this way is believed to be NP-hard, most effort has gone into the construction of search algorithms, and less to the question of other measures of community structures, similarities between various partitionings and the validation with respect to external information. Here we concentrate on a class of computer generated networks and on three well-studied real networks which constitute a bench-mark for network studies; the karate club, the US college football teams and a gene network of yeast. We utilize some standard ways of clustering data (originally not designed for finding community structures in networks) and show that these classical methods sometimes outperform the newer ones. We discuss various measures of the strength of the modular structure, and show by examples features and drawbacks. Further, we compare different partitions by applying some graph-theoretic concepts of distance, which indicate that one of the quality measures of the degree of modularity corresponds quite well with the distance from the true partition. Finally, we introduce a way to validate the partitionings with respect to external data when the nodes are classified but the network structure is unknown. This is here possible since we know everything of the computer generated networks, as well as the historical answer to how the karate club and the football teams are partitioned in reality. The partitioning of the gene network is validated by use of the Gene Ontology database, where we show that a community in general corresponds to a biological process.

Multilabel user classification using the community structure of online networks.

Science.gov (United States)

Rizos, Georgios; Papadopoulos, Symeon; Kompatsiaris, Yiannis

2017-01-01

We study the problem of semi-supervised, multi-label user classification of networked data in the online social platform setting. We propose a framework that combines unsupervised community extraction and supervised, community-based feature weighting before training a classifier. We introduce Approximate Regularized Commute-Time Embedding (ARCTE), an algorithm that projects the users of a social graph onto a latent space, but instead of packing the global structure into a matrix of predefined rank, as many spectral and neural representation learning methods do, it extracts local communities for all users in the graph in order to learn a sparse embedding. To this end, we employ an improvement of personalized PageRank algorithms for searching locally in each user's graph structure. Then, we perform supervised community feature weighting in order to boost the importance of highly predictive communities. We assess our method performance on the problem of user classification by performing an extensive comparative study among various recent methods based on graph embeddings. The comparison shows that ARCTE significantly outperforms the competition in almost all cases, achieving up to 35% relative improvement compared to the second best competing method in terms of F1-score.

Multilabel user classification using the community structure of online networks.

Directory of Open Access Journals (Sweden)

Georgios Rizos

Full Text Available We study the problem of semi-supervised, multi-label user classification of networked data in the online social platform setting. We propose a framework that combines unsupervised community extraction and supervised, community-based feature weighting before training a classifier. We introduce Approximate Regularized Commute-Time Embedding (ARCTE, an algorithm that projects the users of a social graph onto a latent space, but instead of packing the global structure into a matrix of predefined rank, as many spectral and neural representation learning methods do, it extracts local communities for all users in the graph in order to learn a sparse embedding. To this end, we employ an improvement of personalized PageRank algorithms for searching locally in each user's graph structure. Then, we perform supervised community feature weighting in order to boost the importance of highly predictive communities. We assess our method performance on the problem of user classification by performing an extensive comparative study among various recent methods based on graph embeddings. The comparison shows that ARCTE significantly outperforms the competition in almost all cases, achieving up to 35% relative improvement compared to the second best competing method in terms of F1-score.

Do alterations in mesofauna community affect earthworms?

Science.gov (United States)

Uvarov, Alexei V; Karaban, Kamil

2015-11-01

Interactions between the saprotrophic animal groups that strongly control soil microbial activities and the functioning of detrital food webs, such as earthworms and mesofauna, are not well understood. Earthworm trophic and engineering activities strongly affect mesofauna abundance and diversity through various direct and indirect pathways. In contrast, mesofauna effects on earthworm populations are less evident; however, their importance may be high, considering the keystone significance of earthworms for the functioning of the soil system. We studied effects of a diverse mesofauna community of a deciduous forest on two earthworm species representing epigeic (Lumbricus rubellus) and endogeic (Aporrectodea caliginosa) ecological groups. In microcosms, the density of total mesofauna or its separate groups (enchytraeids, collembolans, gamasid mites) was manipulated (increased) and responses of earthworms and soil systems were recorded. A rise in mesofauna density resulted in a decrease of biomass and an increased mortality in L. rubellus, presumably due to competition with mesofauna for litter resources. In contrast, similar mesofauna manipulations promoted reproduction of A. caliginosa, suggesting a facilitated exploitation of litter resources due to increased mesofauna activities. Changes of microcosm respiration rates, litter organic matter content and microbial activities across the manipulation treatments indicate that mesofauna modify responses of soil systems in the presence of earthworms. However, similar mesofauna manipulations could induce different responses in soil systems with either epigeic or endogeic lumbricids, which suggests that earthworm/mesofauna interactions are species-specific. Thus, mesofauna impacts should be treated as a factor affecting the engineering activities of epigeic and endogeic earthworms in the soil.

Developing Structured-Learning Exercises for a Community Advanced Pharmacy Practice Experience

OpenAIRE

Thomas, Renee Ahrens

2006-01-01

The recent growth in the number of pharmacy schools across the nation has resulted in the need for high-quality community advanced pharmacy practice experience (APPE) sites. A vital part of a student's education, these APPEs should be structured and formalized to provide an environment conducive to student learning. This paper discusses how to use a calendar, structured-learning activities, and scheduled evaluations to develop students' knowledge, skills, and abilities in a community pharmacy...

Developing structured-learning exercises for a community advanced pharmacy practice experience.

Science.gov (United States)

Thomas, Renee Ahrens

2006-02-15

The recent growth in the number of pharmacy schools across the nation has resulted in the need for high-quality community advanced pharmacy practice experience (APPE) sites. A vital part of a student's education, these APPEs should be structured and formalized to provide an environment conducive to student learning. This paper discusses how to use a calendar, structured-learning activities, and scheduled evaluations to develop students' knowledge, skills, and abilities in a community pharmacy setting.

Can anthropic fires affect epigaeic and hypogaeic Cerrado ant (Hymenoptera: Formicidae) communities in the same way?

Science.gov (United States)

Canedo-Júnior, Ernesto de Oliveira; Cuissi, Rafael Gonçalves; Nelson Henrique de Almeida, Curi; Demetrio, Guilherme Ramos; Lasmar, Chaim José; Malves, Kira

2016-03-01

Fire occurrences are a common perturbation in Cerrado ecosystems, and may differently impact the local biodiversity. Arthropods are one of the taxa affected by fires, and among them, ants are known as good bioindicators. We aimed to evaluate the effect of anthropic fires on epigaeic and hypogaeic ant communities (species richness and composition) in Cerrado areas with different post-fire event recovery periods. We conducted the study in four Cerrado areas during two weeks of 2012 dry season: one unburned and three at different post-fire times (one month, one and two years). We sampled ants with pitfall traps in epigaeic and hypogaeic microhabitats. We collected 71 ant morpho-species from 25 genera. In the epigaeic microhabitat we sampled 56 morpho-species and 42 in the hypogaeic microhabitat. The area with the shortest recovery time presented lower epigaeic ant species richness (4.3 ± 2.00) in comparison to the other areas (8.1 ± 2.68 species on one year area; 10.3 ± 2.66 species on two years area; 10.4 ± 2.31 species on control area), but recovery time did not affect hypogaeic ant species richness. Regarding ant species composition, fire did not directly affect hypogaeic ant species, which remained the same even one month after fire event. However, two years were not enough to reestablish ant species composition in both microhabitats in relation to our control group samples. Our study is the first to assess anthropic fire effects upon epigaeic and hypogaeic ants communities; highlighting the importance of evaluating different microhabitats, to more accurately detect the effects of anthropic disturbances in biological communities. We concluded that ant communities are just partially affected by fire occurrences, and epigaeic assemblages are the most affected ones in comparison to hypogaeic ants. Furthermore the study provides knowledge to aid in the creation of vegetation management programs that allow Cerrado conservation.

Phylogenetic and Functional Structure of Wintering Waterbird Communities Associated with Ecological Differences.

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Che, Xianli; Zhang, Min; Zhao, Yanyan; Zhang, Qiang; Quan, Qing; Møller, Anders; Zou, Fasheng

2018-01-19

Ecological differences may be related to community component divisions between Oriental (west) and Sino-Japanese (east) realms, and such differences may result in weak geographical breaks in migratory species that are highly mobile. Here, we conducted comparative phylogenetic and functional structure analyses of wintering waterbird communities in southern China across two realms and subsequently examined possible climate drivers of the observed patterns. An analysis based on such highly migratory species is particularly telling because migration is bound to reduce or completely eliminate any divergence between communities. Phylogenetic and functional structure of eastern communities showed over-dispersion while western communities were clustered. Basal phylogenetic and functional turnover of western communities was significant lower than that of eastern communities. The break between eastern and western communities was masked by these two realms. Geographic patterns were related to mean temperature changes and temperature fluctuations, suggesting that temperature may filter waterbird lineages and traits, thus underlying geographical community divisions. These results suggest phylogenetic and functional divisions in southern China, coinciding with biogeography. This study shows that temperature fluctuations constitute an essential mechanism shaping geographical divisions that have largely gone undetected previously, even under climate change.

Relationships between soil properties and community structure of soil macroinvertebrates in oak-history forests along an acidic deposition gradient

Energy Technology Data Exchange (ETDEWEB)

Kuperman, R.G. [Argonne National Lab., IL (United States). Environmental Assessment Div.

1996-02-01

Soil macroinvertebrate communities were studied in ecologically analogous oak-hickory forests across a three-state atmospheric pollution gradient in Illinois, Indiana, and Ohio. The goal was to investigate changes in the community structure of soil fauna in study sites receiving different amounts of acidic deposition for several decades and the possible relationships between these changes and physico-chemical properties of soil. The study revealed significant differences in the numbers of soil animals among the three study sites. The sharply differentiated pattern of soil macroinvertebrate fauna seems closely linked to soil chemistry. Significant correlations of the abundance of soil macroinvertebrates with soil parameters suggest that their populations could have been affected by acidic deposition in the region. Abundance of total soil macroinvertebrates decreased with the increased cumulative loading of acidic deposition. Among the groups most sensitive to deposition were: earthworms gastropods, dipteran larvae, termites, and predatory beetles. The results of the study support the hypothesis that chronic long-term acidic deposition could aversely affect the soil decomposer community which could cause lower organic matter turnover rates leading to an increase in soil organic matter content in high deposition sites.

Detection of stable community structures within gut microbiota co-occurrence networks from different human populations.

Science.gov (United States)

Jackson, Matthew A; Bonder, Marc Jan; Kuncheva, Zhana; Zierer, Jonas; Fu, Jingyuan; Kurilshikov, Alexander; Wijmenga, Cisca; Zhernakova, Alexandra; Bell, Jordana T; Spector, Tim D; Steves, Claire J

2018-01-01

Microbes in the gut microbiome form sub-communities based on shared niche specialisations and specific interactions between individual taxa. The inter-microbial relationships that define these communities can be inferred from the co-occurrence of taxa across multiple samples. Here, we present an approach to identify comparable communities within different gut microbiota co-occurrence networks, and demonstrate its use by comparing the gut microbiota community structures of three geographically diverse populations. We combine gut microbiota profiles from 2,764 British, 1,023 Dutch, and 639 Israeli individuals, derive co-occurrence networks between their operational taxonomic units, and detect comparable communities within them. Comparing populations we find that community structure is significantly more similar between datasets than expected by chance. Mapping communities across the datasets, we also show that communities can have similar associations to host phenotypes in different populations. This study shows that the community structure within the gut microbiota is stable across populations, and describes a novel approach that facilitates comparative community-centric microbiome analyses.

The impacts of triclosan on anaerobic community structures, function, and antimicrobial resistance.

Science.gov (United States)

McNamara, Patrick J; LaPara, Timothy M; Novak, Paige J

2014-07-01

Triclosan is a widespread antimicrobial agent that accumulates in anaerobic digesters used to treat the residual solids generated at municipal wastewater treatment plants; there is very little information, however, about how triclosan impacts microbial communities in anaerobic digesters. We investigated how triclosan impacts the community structure, function and antimicrobial resistance genes in lab-scale anaerobic digesters. Previously exposed (to triclosan) communities were amended with 5, 50, and 500 mg/kg of triclosan, corresponding to the median, 95th percentile, and 4-fold higher than maximum triclosan concentration that has been detected in U.S. biosolids. Triclosan amendment caused all of the Bacteria and Archaea communities to structurally diverge from that of the control cultures (based on ARISA). At the end of the experiment, all triclosan-amended Archaea communities had diverged from the control communities, regardless of the triclosan concentration added. In contrast, over time the Bacteria communities that were amended with lower concentrations of triclosan (5 mg/kg and 50 mg/kg) initially diverged and then reconverged with the control community structure. Methane production at 500 mg/kg was nearly half the methane production in control cultures. At 50 mg/kg, a large variability in methane production was observed, suggesting that 50 mg/kg may be a tipping point where function begins to fail in some communities. When previously unexposed communities were exposed to 500 mg triclosan/kg, function was maintained, but the abundance of a gene encoding for triclosan resistance (mexB) increased. This research suggests that triclosan could inhibit methane production in anaerobic digesters if concentrations were to increase and may also select for resistant Bacteria. In both cases, microbial community composition and exposure history alter the influence of triclosan.

Nematode diversity, abundance and community structure 50 years after the formation of the volcanic island of Surtsey

Science.gov (United States)

Ilieva-Makulec, K.; Bjarnadottir, B.; Sigurdsson, B. D.

2014-10-01

The soil nematode fauna can give important insights into soil development and other habitat changes that occur during primary succession. We investigated the generic composition, density, distribution and community structure of nematodes 50 years after the formation of a pristine volcanic island, Surtsey, Iceland. Part of the island has received additional nutrient inputs from seagulls breeding there since 1985, while the reminder has been much less affected and is at present found at a different successional sere. In total, 25 genera of nematodes were identified, of which 14 were reported on Surtsey for the first time. Nematode communities were more diverse in the more infertile area outside the gull colony, where 24 genera were found, compared to 18 inside. The trophic structure of the nematode communities showed relatively higher abundance of fungal feeders in the infertile areas, but relatively more bacterial- and plant-feeders inside the colony. Nematode abundance in surface soil was, however, significantly higher within the gull colony, with 16.7 ind. cm-2 compared to 3.6 ind. cm-2 outside. A multivariate analysis indicated that the nematode abundance and distribution on Surtsey were most strongly related to the soil C : N ratio, soil acidity, plant cover and biomass, soil temperature and soil depth.

Trophic structure of the fouling community in Odessa Bay (Black Sea

Directory of Open Access Journals (Sweden)

A. Y. Varigin

2016-06-01

Full Text Available The trophic structure of the coastal fouling community of Odessa Bay (Black Sea, which was composed of 10 species of macrophytes, 57 invertebrate species and 4 species of fish, was determined. The basic trophic relationship between organisms composing the community is shown. A minimization of interspecific trophic competition within the community is noted. The main sources of food material entering the fouling community were determined. We show that a significant proportion of food in the form of detritus, dissolved organic matter and small planktonic organisms enters the community from the water column. Filtration and pumping activity of sestonophage-organisms, particularly mussels, helps to attract food material to the community. Primary producers of the community are macrophytes and microphytes, which develop on account of their photosynthetic activity and ensure the provision of food to herbivores. The trophic group of detritophages consumes different fractions of the detritus which accumulates in the byssus threads of bivalve molluscs. In this context, mussel druses act as sediment traps, collecting detritus. Numerous polyphages, which are essentially omnivores and do not usually lack food material, were noted in the community. A small group of carnivorous invertebrates, whose representatives actively attack small animals, was identified. The abundance of these species in the community was about 1%, and their biomass less than 0.6%. Fish living in macrophyte weeds are the consumers in the community. We determined that the highest relative abundance (over 36% in the fouling community was reached by sestonophages and polyphages. We found that the undisputed leader in the relative biomass (over 97% in the fouling community ofOdessaBaywas the sestonophages (mainly composed of mussels. We determined that the trophic structure index of the community was 0.94, which confirms the significant dominance in biomass of bivalves over other species in

Structure of hydrocarbonoclastic nitrate-reducing bacterial communities in bioturbated coastal marine sediments.

Science.gov (United States)

Stauffert, Magalie; Cravo-Laureau, Cristiana; Duran, Robert

2014-09-01

The organisation of denitrifying microorganisms in oil-polluted bioturbated sediments was investigated in mesocosms under conditions as closer as possible to that observed in the environment. Molecular and culture-dependent approaches revealed that denitrifying Gammaproteobacteria were abundant in oil-polluted and bioturbated sediments suggesting that they may play a key role in hydrocarbon degradation in the environment. T-RFLP and gene libraries analyses targeting nirS gene showed that denitrifying microbial communities structure was slightly affected by either the addition of Hediste diversicolor or crude oil revealing the metabolic versatility of denitrifying microorganisms. From oil-polluted sediments, distinct denitrifying hydrocarbonoclastic bacterial consortia were obtained by enrichment cultures on high molecular weight polyaromatic hydrocarbons (PAHs) (dibenzothiophene, fluoranthene, pyrene and chrysene) under nitrate-reducing conditions. Interestingly, molecular characterisation of the consortia showed that the denitrifying communities obtained from oiled microcosms with addition of H. diversicolor were different to that observed without H. diversicolor addition, especially with fluoranthene and chrysene revealing the bacterial diversity involved in the degradation of these PAHs. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

Successional and seasonal variations in soil and litter microbial community structure and function during tropical postagricultural forest regeneration: a multiyear study.

Science.gov (United States)

Smith, A Peyton; Marín-Spiotta, Erika; Balser, Teri

2015-09-01

Soil microorganisms regulate fundamental biochemical processes in plant litter decomposition and soil organic matter (SOM) transformations. Understanding how microbial communities respond to changes in vegetation is critical for improving predictions of how land-cover change affects belowground carbon storage and nutrient availability. We measured intra- and interannual variability in soil and forest litter microbial community composition and activity via phospholipid fatty acid analysis (PLFA) and extracellular enzyme activity across a well-replicated, long-term chronosequence of secondary forests growing on abandoned pastures in the wet subtropical forest life zone of Puerto Rico. Microbial community PLFA structure differed between young secondary forests and older secondary and primary forests, following successional shifts in tree species composition. These successional patterns held across seasons, but the microbial groups driving these patterns differed over time. Microbial community composition from the forest litter differed greatly from those in the soil, but did not show the same successional trends. Extracellular enzyme activity did not differ with forest succession, but varied by season with greater rates of potential activity in the dry seasons. We found few robust significant relationships among microbial community parameters and soil pH, moisture, carbon, and nitrogen concentrations. Observed inter- and intrannual variability in microbial community structure and activity reveal the importance of a multiple, temporal sampling strategy when investigating microbial community dynamics with land-use change. Successional control over microbial composition with forest recovery suggests strong links between above and belowground communities. © 2015 John Wiley & Sons Ltd.

Community Structure Analysis of Gene Interaction Networks in Duchenne Muscular Dystrophy.

Directory of Open Access Journals (Sweden)

Tejaswini Narayanan

Full Text Available Duchenne Muscular Dystrophy (DMD is an important pathology associated with the human skeletal muscle and has been studied extensively. Gene expression measurements on skeletal muscle of patients afflicted with DMD provides the opportunity to understand the underlying mechanisms that lead to the pathology. Community structure analysis is a useful computational technique for understanding and modeling genetic interaction networks. In this paper, we leverage this technique in combination with gene expression measurements from normal and DMD patient skeletal muscle tissue to study the structure of genetic interactions in the context of DMD. We define a novel framework for transforming a raw dataset of gene expression measurements into an interaction network, and subsequently apply algorithms for community structure analysis for the extraction of topological communities. The emergent communities are analyzed from a biological standpoint in terms of their constituent biological pathways, and an interpretation that draws correlations between functional and structural organization of the genetic interactions is presented. We also compare these communities and associated functions in pathology against those in normal human skeletal muscle. In particular, differential enhancements are observed in the following pathways between pathological and normal cases: Metabolic, Focal adhesion, Regulation of actin cytoskeleton and Cell adhesion, and implication of these mechanisms are supported by prior work. Furthermore, our study also includes a gene-level analysis to identify genes that are involved in the coupling between the pathways of interest. We believe that our results serve to highlight important distinguishing features in the structural/functional organization of constituent biological pathways, as it relates to normal and DMD cases, and provide the mechanistic basis for further biological investigations into specific pathways differently regulated

Relative diversity and community structure analysis of rumen protozoa according to T-RFLP and microscopic methods.

Science.gov (United States)

Tymensen, Lisa; Barkley, Cindy; McAllister, Tim A

2012-01-01

Protozoa are common inhabitants of the rumen where they play roles in host nutrition and methanogenesis. Knowledge of how changes in the composition of protozoa communities affect these processes is limited in part due to a lack of efficient methods for protozoa community analysis. In this study, a terminal-restriction fragment length polymorphism (T-RFLP) assay targeting the 18S rRNA gene was developed for comparative analysis of rumen protozoa communities. Comparison of diversity and structure of protozoa communities from hay-fed versus silage/grain-fed cattle via T-RFLP analysis yielded similar overall results to microscopy analysis. According to both methods, Entodinium spp. were more abundant in the silage/grain-fed cattle and protozoa diversity (as calculated using the Shannon index) was higher for the hay-fed cattle due to greater species evenness. Type B protozoa were more prevalent in the hay-fed cattle, whereas Type A protozoa were more prevalent in the silage/grain-fed cattle. Analysis of similarity (ANOSIM) indicated that the protozoa communities from hay-fed and silage/grain-fed cattle were different, and multivariate analysis indicated that pen mates (i.e., cattle fed the same diet and housed together) tended to have similar protozoa communities types. In summary, we present a T-RFLP method for analyzing rumen protozoa communities which complements traditional microscopy approaches but has the advantage of being amenable to high-throughput. Copyright © 2011. Published by Elsevier B.V.

Microbial Community and Functional Structure Significantly Varied among Distinct Types of Paddy Soils But Responded Differently along Gradients of Soil Depth Layers

Directory of Open Access Journals (Sweden)

Ren Bai

2017-05-01

identified as the key driver in shaping both bacterial and archaeal community structure, but did not directly affect microbial functional structure. The distinctive pattern of microbial taxonomic and functional composition along soil profiles implied functional redundancy within these paddy soils.

Microbial Community and Functional Structure Significantly Varied among Distinct Types of Paddy Soils But Responded Differently along Gradients of Soil Depth Layers.

Science.gov (United States)

Bai, Ren; Wang, Jun-Tao; Deng, Ye; He, Ji-Zheng; Feng, Kai; Zhang, Li-Mei

2017-01-01

identified as the key driver in shaping both bacterial and archaeal community structure, but did not directly affect microbial functional structure. The distinctive pattern of microbial taxonomic and functional composition along soil profiles implied functional redundancy within these paddy soils.

Strong influence of regional species pools on continent-wide structuring of local communities

OpenAIRE

Lessard, Jean-Philippe; Borregaard, Michael K.; Fordyce, James A.; Rahbek, Carsten; Weiser, Michael D.; Dunn, Robert R.; Sanders, Nathan J.

2011-01-01

There is a long tradition in ecology of evaluating the relative contribution of the regional species pool and local interactions on the structure of local communities. Similarly, a growing number of studies assess the phylogenetic structure of communities, relative to that in the regional species pool, to examine the interplay between broad-scale evolutionary and fine-scale ecological processes. Finally, a renewed interest in the influence of species source pools on communities has shown that...

Cyanobacterial Community Structure In Lithifying Mats of A Yellowstone Hotspring-Implications for Precambrian Stromatolite Biocomplexity

Science.gov (United States)

Lau, Evan; Nash, C. Z.; Vogler, D. R.; Cullings, K.; DeVincenzi, Donald (Technical Monitor)

2002-01-01

Denaturing Gradient Gel Electrophoresis (DGGE) of partial 16S rRNA gene sequences was used to investigate the molecular biodiversity of cyanobacterial communities inhabiting various lithified morpho-structures in two hotsprings of Yellowstone National Park. These morpho-structures - flat-topped columns, columnar cones, and ridged cones - resemble ancient stromatolites, which are possibly biogenic in origin. The top, middle and bottom sections of these lithified morpho-structures, as well as surrounding non-lithified mats were analyzed to determine the vertical and spatial distribution of cyanobacterial communities. Results from DGGE indicate that the cyanobacterial community composition of lithified morpho-structures (flat-topped columns, columnar cones, and ridged cones) were largely similar in vertical distribution as well as among the morpho-structures being studied. Preliminary results indicate that the cyanobacterial communities in these lithified morpho-structures were significantly different from communities in surrounding non-lithified mats. These results provide additional support to the theory that certain Phormidium/Leptolyngbya species are involved in the morphogenesis of lithifying morpho-structures in hotsprings and may have played a role in the formation of ancient stromatolites.

Plant traits determine the phylogenetic structure of arbuscular mycorrhizal fungal communities.

Science.gov (United States)

López-García, Álvaro; Varela-Cervero, Sara; Vasar, Martti; Öpik, Maarja; Barea, José M; Azcón-Aguilar, Concepción

2017-12-01

Functional diversity in ecosystems has traditionally been studied using aboveground plant traits. Despite the known effect of plant traits on the microbial community composition, their effects on the microbial functional diversity are only starting to be assessed. In this study, the phylogenetic structure of arbuscular mycorrhizal (AM) fungal communities associated with plant species differing in life cycle and growth form, that is, plant life forms, was determined to unravel the effect of plant traits on the functional diversity of this fungal group. The results of the 454 pyrosequencing showed that the AM fungal community composition differed across plant life forms and this effect was dependent on the soil collection date. Plants with ruderal characteristics tended to associate with phylogenetically clustered AM fungal communities. By contrast, plants with resource-conservative traits associated with phylogenetically overdispersed AM fungal communities. Additionally, the soil collected in different seasons yielded AM fungal communities with different phylogenetic dispersion. In summary, we found that the phylogenetic structure, and hence the functional diversity, of AM fungal communities is dependent on plant traits. This finding adds value to the use of plant traits for the evaluation of belowground ecosystem diversity, functions and processes. © 2017 John Wiley & Sons Ltd.

Nash Stability in Additively Separable Hedonic Games and Community Structures

DEFF Research Database (Denmark)

Olsen, Martin

2009-01-01

  We prove that the problem of deciding whether a Nash stable   partition exists in an Additively Separable Hedonic Game is   NP-complete. We also show that the problem of deciding whether a   non trivial Nash stable partition exists in an   Additively Separable Hedonic Game with   non......-negative and symmetric   preferences is NP-complete. We motivate our study of the   computational complexity by linking Nash stable partitions in   Additively Separable Hedonic Games to community structures in   networks. Our results formally justify that computing community   structures in general is hard....

Relations between water physico-chemistry and benthic algal communities in a northern Canadian watershed: defining reference conditions using multiple descriptors of community structure.

Science.gov (United States)

Thomas, Kathryn E; Hall, Roland I; Scrimgeour, Garry J

2015-09-01

Defining reference conditions is central to identifying environmental effects of anthropogenic activities. Using a watershed approach, we quantified reference conditions for benthic algal communities and their relations to physico-chemical conditions in rivers in the South Nahanni River watershed, NWT, Canada, in 2008 and 2009. We also compared the ability of three descriptors that vary in terms of analytical costs to define algal community structure based on relative abundances of (i) all algal taxa, (ii) only diatom taxa, and (iii) photosynthetic pigments. Ordination analyses showed that variance in algal community structure was strongly related to gradients in environmental variables describing water physico-chemistry, stream habitats, and sub-watershed structure. Water physico-chemistry and local watershed-scale descriptors differed significantly between algal communities from sites in the Selwyn Mountain ecoregion compared to sites in the Nahanni-Hyland ecoregions. Distinct differences in algal community types between ecoregions were apparent irrespective of whether algal community structure was defined using all algal taxa, diatom taxa, or photosynthetic pigments. Two algal community types were highly predictable using environmental variables, a core consideration in the development of Reference Condition Approach (RCA) models. These results suggest that assessments of environmental impacts could be completed using RCA models for each ecoregion. We suggest that use of algal pigments, a high through-put analysis, is a promising alternative compared to more labor-intensive and costly taxonomic approaches for defining algal community structure.

Permafrost soil characteristics and microbial community structure across a boreal forest watershed vary over short spatial scales and dictate community responses to thaw.

Science.gov (United States)

Stegen, J.; Bottos, E. M.; Kennedy, D.; Romero, E. B.; Fansler, S.; Chu, R. K.; Tfaily, M.; Jansson, J.; Bernstein, H. C.; Brown, J. M.; Markillie, L. M.

2017-12-01

Understanding drivers of permafrost microbial community structure and function is critical for understanding permafrost microbiology and predicting ecosystem responses to thaw; however, studies describing ecological controls on these communities are lacking. We hypothesize that permafrost communities are uniquely shaped by constraints imposed by prolonged freezing, and decoupled from the selective factors that influence non-permafrost soil communities, but that pre-thaw environmental and community characteristics will be strong determinants of community structure and function post-thaw. We characterized patterns of environmental variation and microbial community composition in sixty permafrost samples spanning landscape gradients in a boreal forest watershed, and monitored community responses to thaw. Consistent with our hypothesis, we found that, proportionally, the strongest process influencing permafrost community composition was dispersal limitation (0.36), exceeding the influence of homogenous selection (0.21) and variable selection (0.16), and that deterministic selection arose primarily from energetic constraints of the permafrost environment. Our data supported a structural equation model in which organic carbon thermodynamics and organic acid content, influenced redox conditions and total selection. Post-thaw community composition was found to be driven primarily by pre-thaw community composition, indicating a strong influence of historical conditions. Together, these results suggest that community responses to thaw may be highly varied over short distances and that changes in community structure and function are likely to be drastic, as changes to system hydrology mobilize organisms and nutrients, thereby relieving the primary constraints on the system. These findings are being integrated with metabolomic and metatranscriptomic analyses to improve understanding of how pre-thaw conditions can be used to predict microbial activity post-thaw.

Resilience and recovery: The effect of triclosan exposure timing during development, on the structure and function of river biofilm communities

Energy Technology Data Exchange (ETDEWEB)

Lawrence, J.R., E-mail: john.lawrence@ec.gc.ca [Environment Canada, 11 Innovation Blvd., Saskatoon, SK S7N 3H5 (Canada); Topp, E. [Agriculture and Agri-Food Canada, London, ON (Canada); Waiser, M.J.; Tumber, V.; Roy, J.; Swerhone, G.D.W. [Environment Canada, 11 Innovation Blvd., Saskatoon, SK S7N 3H5 (Canada); Leavitt, P. [University of Regina, Regina, SK (Canada); Paule, A. [Global Institute for Water Security, University of Saskatchewan, Saskatoon, SK (Canada); Korber, D.R. [Food and Bioproduct Sciences, University of Saskatchewan, Saskatoon, SK (Canada)

2015-04-15

Highlights: • Triclosan negatively affected structure and metabolism of biofilms under all exposure conditions. • Biofilm age, timing and exposure regime alter the effects of triclosan. • Regardless of exposure regime algae and cyanobacteria were the most affected. • Although recovery was evident no community regained the reference condition. • Initial recruitment may be significant in determining community recovery. - Abstract: Triclosan (TCS) is a ubiquitous antibacterial agent found in soaps, scrubs, and consumer products. There is limited information on hazardous effects of TCS in the environment. Here, rotating annular reactors were used to cultivate river biofilm communities exposed to 1.8 μg l{sup −1} TCS with the timing and duration of exposure and recovery during development varied. Two major treatment regimens were employed: (i) biofilm development for 2, 4 or 6 weeks prior to TCS exposure and (ii) exposure of biofilms to TCS for 2, 4 or 6 weeks followed by recovery. Biofilms not exposed to TCS were used as a reference condition. Communities cultivated without and then exposed to TCS all exhibited reductions in algal biomass and significant (p < 0.05) reductions in cyanobacterial biomass. No significant effects were observed on bacterial biomass. CLSM imaging of biofilms at 8 weeks revealed unique endpoints in terms of community architecture. Community composition was altered by any exposure to TCS, as indicated by significant shifts in denaturing gradient gel electrophoresis fingerprints and exopolymer composition relative to the reference. Bacterial, algal and cyanobacterial components initially exposed to TCS were significantly different from those TCS-free at time zero. Pigment analyses suggested that significant changes in composition of algal and cyanobacterial populations occurred with TCS exposure. Bacterial thymidine incorporation rates were reduced by TCS exposure and carbon utilization spectra shifted in terms substrate metabolism

Resilience and recovery: The effect of triclosan exposure timing during development, on the structure and function of river biofilm communities

International Nuclear Information System (INIS)

Lawrence, J.R.; Topp, E.; Waiser, M.J.; Tumber, V.; Roy, J.; Swerhone, G.D.W.; Leavitt, P.; Paule, A.; Korber, D.R.

2015-01-01

Highlights: • Triclosan negatively affected structure and metabolism of biofilms under all exposure conditions. • Biofilm age, timing and exposure regime alter the effects of triclosan. • Regardless of exposure regime algae and cyanobacteria were the most affected. • Although recovery was evident no community regained the reference condition. • Initial recruitment may be significant in determining community recovery. - Abstract: Triclosan (TCS) is a ubiquitous antibacterial agent found in soaps, scrubs, and consumer products. There is limited information on hazardous effects of TCS in the environment. Here, rotating annular reactors were used to cultivate river biofilm communities exposed to 1.8 μg l −1 TCS with the timing and duration of exposure and recovery during development varied. Two major treatment regimens were employed: (i) biofilm development for 2, 4 or 6 weeks prior to TCS exposure and (ii) exposure of biofilms to TCS for 2, 4 or 6 weeks followed by recovery. Biofilms not exposed to TCS were used as a reference condition. Communities cultivated without and then exposed to TCS all exhibited reductions in algal biomass and significant (p < 0.05) reductions in cyanobacterial biomass. No significant effects were observed on bacterial biomass. CLSM imaging of biofilms at 8 weeks revealed unique endpoints in terms of community architecture. Community composition was altered by any exposure to TCS, as indicated by significant shifts in denaturing gradient gel electrophoresis fingerprints and exopolymer composition relative to the reference. Bacterial, algal and cyanobacterial components initially exposed to TCS were significantly different from those TCS-free at time zero. Pigment analyses suggested that significant changes in composition of algal and cyanobacterial populations occurred with TCS exposure. Bacterial thymidine incorporation rates were reduced by TCS exposure and carbon utilization spectra shifted in terms substrate metabolism

Simulation modeling to understand how selective foraging by beaver can drive the structure and function of a willow community

Science.gov (United States)

Peinetti, H.R.; Baker, B.W.; Coughenour, M.B.

2009-01-01

Beaver-willow (Castor-Salix) communities are a unique and vital component of healthy wetlands throughout the Holarctic region. Beaver selectively forage willow to provide fresh food, stored winter food, and construction material. The effects of this complex foraging behavior on the structure and function of willow communities is poorly understood. Simulation modeling may help ecologists understand these complex interactions. In this study, a modified version of the SAVANNA ecosystem model was developed to better understand how beaver foraging affects the structure and function of a willow community in a simulated riparian ecosystem in Rocky Mountain National Park, Colorado (RMNP). The model represents willow in terms of plant and stem dynamics and beaver foraging in terms of the quantity and quality of stems cut to meet the energetic and life history requirements of beaver. Given a site where all stems were equally available, the model suggested a simulated beaver family of 2 adults, 2 yearlings, and 2 kits required a minimum of 4 ha of willow (containing about10 stems m-2) to persist in a steady-state condition. Beaver created a willow community where the annual net primary productivity (ANPP) was 2 times higher and plant architecture was more diverse than the willow community without beaver. Beaver foraging created a plant architecture dominated by medium size willow plants, which likely explains how beaver can increase ANPP. Long-term simulations suggested that woody biomass stabilized at similar values even though availability differed greatly at initial condition. Simulations also suggested that willow ANPP increased across a range of beaver densities until beaver became food limited. Thus, selective foraging by beaver increased productivity, decreased biomass, and increased structural heterogeneity in a simulated willow community.

Effect of sugarcane burning or green harvest methods on the Brazilian Cerrado soil bacterial community structure.

Science.gov (United States)

Rachid, Caio T C C; Santos, Adriana L; Piccolo, Marisa C; Balieiro, Fabiano C; Coutinho, Heitor L C; Peixoto, Raquel S; Tiedje, James M; Rosado, Alexandre S

2013-01-01

The Brazilian Cerrado is one of the most important biodiversity reservoirs in the world. The sugarcane cultivation is expanding in this biome and necessitates the study of how it may impact the soil properties of the Cerrado. There is a lack of information especially about the impacts of different sugarcane management on the native bacterial communities of Cerrado soil. Therefore, our objective was to evaluate and compare the soil bacterial community structure of the Cerrado vegetation with two sugarcane systems. We evaluated samples under native vegetation and the impact of the two most commonly used management strategies for sugarcane cultivation (burnt cane and green cane) on this diversity using pyrosequencing and quantitative PCR of the rrs gene (16S rRNA). Nineteen different phyla were identified, with Acidobacteria (≈35%), Proteobacteria (≈24%) and Actinobacteria (≈21%) being the most abundant. Many of the sequences were represented by few operational taxonomic units (OTUs, 3% of dissimilarity), which were found in all treatments. In contrast, there were very strong patterns of local selection, with many OTUs occurring only in one sample. Our results reveal a complex bacterial diversity, with a large fraction of microorganisms not yet described, reinforcing the importance of this biome. As possible sign of threat, the qPCR detected a reduction of the bacterial population in agricultural soils compared with native Cerrado soil communities. We conclude that sugarcane cultivation promoted significant structural changes in the soil bacterial community, with Firmicutes phylum and Acidobacteria classes being the groups most affected.

Microbial community functional structures in wastewater treatment plants as characterized by GeoChip.

Science.gov (United States)

Wang, Xiaohui; Xia, Yu; Wen, Xianghua; Yang, Yunfeng; Zhou, Jizhong

2014-01-01

Biological WWTPs must be functionally stable to continuously and steadily remove contaminants which rely upon the activity of complex microbial communities. However, knowledge is still lacking in regard to microbial community functional structures and their linkages to environmental variables. To investigate microbial community functional structures of activated sludge in wastewater treatment plants (WWTPs) and to understand the effects of environmental factors on their structure. 12 activated sludge samples were collected from four WWTPs in Beijing. A comprehensive functional gene array named GeoChip 4.2 was used to determine the microbial functional genes involved in a variety of biogeochemical processes such as carbon, nitrogen, phosphorous and sulfur cycles, metal resistance, antibiotic resistance and organic contaminant degradation. High similarities of the microbial community functional structures were found among activated sludge samples from the four WWTPs, as shown by both diversity indices and the overlapped genes. For individual gene category, such as egl, amyA, lip, nirS, nirK, nosZ, ureC, ppx, ppk, aprA, dsrA, sox and benAB, there were a number of microorganisms shared by all 12 samples. Canonical correspondence analysis (CCA) showed that the microbial functional patterns were highly correlated with water temperature, dissolved oxygen (DO), ammonia concentrations and loading rate of chemical oxygen demand (COD). Based on the variance partitioning analyses (VPA), a total of 53% of microbial community variation from GeoChip data can be explained by wastewater characteristics (25%) and operational parameters (23%), respectively. This study provided an overall picture of microbial community functional structures of activated sludge in WWTPs and discerned the linkages between microbial communities and environmental variables in WWTPs.

Microbial community functional structures in wastewater treatment plants as characterized by GeoChip.

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Xiaohui Wang

Full Text Available BACKGROUND: Biological WWTPs must be functionally stable to continuously and steadily remove contaminants which rely upon the activity of complex microbial communities. However, knowledge is still lacking in regard to microbial community functional structures and their linkages to environmental variables. AIMS: To investigate microbial community functional structures of activated sludge in wastewater treatment plants (WWTPs and to understand the effects of environmental factors on their structure. METHODS: 12 activated sludge samples were collected from four WWTPs in Beijing. A comprehensive functional gene array named GeoChip 4.2 was used to determine the microbial functional genes involved in a variety of biogeochemical processes such as carbon, nitrogen, phosphorous and sulfur cycles, metal resistance, antibiotic resistance and organic contaminant degradation. RESULTS: High similarities of the microbial community functional structures were found among activated sludge samples from the four WWTPs, as shown by both diversity indices and the overlapped genes. For individual gene category, such as egl, amyA, lip, nirS, nirK, nosZ, ureC, ppx, ppk, aprA, dsrA, sox and benAB, there were a number of microorganisms shared by all 12 samples. Canonical correspondence analysis (CCA showed that the microbial functional patterns were highly correlated with water temperature, dissolved oxygen (DO, ammonia concentrations and loading rate of chemical oxygen demand (COD. Based on the variance partitioning analyses (VPA, a total of 53% of microbial community variation from GeoChip data can be explained by wastewater characteristics (25% and operational parameters (23%, respectively. CONCLUSIONS: This study provided an overall picture of microbial community functional structures of activated sludge in WWTPs and discerned the linkages between microbial communities and environmental variables in WWTPs.

PARAMETERS AFFECTING THE STRUCTURAL ANALYSIS OF A TUNNEL STRUCTURE EXPOSED TO FIRE

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Omid Pouran

2016-12-01

Full Text Available Behaviour of cut-and-cover tunnels exposed to fire should be analysed by using a realistic structural model that takes account of mechanical and thermal effects on the structure. This has been performed with the aid of Finite Element (FE software package called SOFiSTiK in parallel, for two types of elements as a scope of research project financed by the German Bundesanstalt für Straßenwesen BAST. Since the stiffness of the structure at elevated temperatures is highly affected, a realistic model of structural behaviour of the tunnel could be only achieved by considering the nonlinear analysis of the structure. This has been performed for a 2–cell cut and cover tunnel by taking account of simultaneous reduction of stiffness and strength and the time-dependent increasing indirect effects due to axial constraints and temperature gradients induced by elevated temperatures. The thermal analyses have been performed and the effects were implemented into the structural model by the multi-layered strain model. The stress–strain model proposed by EN 1992-1-2 is implemented for the elevated temperature. Since there was sufficient amount of Polypropylene fibres in the concrete mixtures, modelling of spalling was excluded from the analysis. The critical corresponding stresses and material behaviour are compared and interpreted at different time stages. The main parameters affecting the accuracy and convergence of the results of structural analysis for the used model are identified: defining a realistic fire action, using concrete material model fulfilling the requirements of fire situation in tunnels, defining appropriate time intervals for load implementations. These parameters along with other parameters, which influence the results to a lesser degree, are identified and investigated in this paper.

Antecedents of citizenship behaviour in online customer communities: An empirical investigation

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Mercy Mpinganjira

2016-08-01

Full Text Available Background: Use of online communities for knowledge generation has become a common phenomenon. In order for online communities to serve as affective spaces for knowledge generation and exchange, members need to behave in ways that are in line with good citizenship. However, because of the limited research, not much is known about citizenship behaviour in such communities and the factors that foster such conduct. Objectives: This article aims to examine the performance of citizenship behaviours by members of online customer communities, and the factors that influence this. Methodology: Data were collected from 303 contributing members of online customer communities using a structured questionnaire. Structural equation modelling was used to analyse the data collected. Results: The findings show moderate levels of engagement in citizenship behaviours among the respondents. Engagement in citizenship behaviours was in general found to be influenced more by the level of affective commitment towards the community than by the perceived levels of social support. Both affective commitment and perceived social support were found to have less influence on compliant citizenship behaviour when compared with altruism and personal initiative. Affective commitment was found to influence personal initiative most strongly, while social support had its strongest influence on altruism. Conclusion: The results provide insights for managers of online customer communities into factors to which they should give attention in order to enhance the performance of citizenship behaviours.

Zooplankton community structure and dynamics during the transition ...

African Journals Online (AJOL)

This study investigates the zooplankton community structure and dynamics of Kufena Rock Pool during the transition from dry season (March to April) to rainy season (May to June) in Zaria, Nigeria. Physicochemical parameters such as temperature, hydrogen ion concentration, electrical conductivity and total dissolved ...

Friendship Concept and Community Network Structure among Elementary School and University Students.

Science.gov (United States)

Hernández-Hernández, Ana María; Viga-de Alva, Dolores; Huerta-Quintanilla, Rodrigo; Canto-Lugo, Efrain; Laviada-Molina, Hugo; Molina-Segui, Fernanda

2016-01-01

We use complex network theory to study the differences between the friendship concepts in elementary school and university students. Four friendship networks were identified from surveys. Three of these networks are from elementary schools; two are located in the rural area of Yucatán and the other is in the urban area of Mérida, Yucatán. We analyzed the structure and the communities of these friendship networks and found significant differences among those at the elementary schools compared with those at the university. In elementary schools, the students make friends mainly in the same classroom, but there are also links among different classrooms because of the presence of siblings and relatives in the schools. These kinds of links (sibling-friend or relative-friend) are called, in this work, "mixed links". The classification of the communities is based on their similarity with the classroom composition. If the community is composed principally of students in different classrooms, the community is classified as heterogeneous. These kinds of communities appear in the elementary school friendship networks mainly because of the presence of relatives and siblings. Once the links between siblings and relatives are removed, the communities resembled the classroom composition. On the other hand, the university students are more selective in choosing friends and therefore, even when they have friends in the same classroom, those communities are quite different to the classroom composition. Also, in the university network, we found heterogeneous communities even when the presence of sibling and relatives is negligible. These differences made up a topological structure quite different at different academic levels. We also found differences in the network characteristics. Once these differences are understood, the topological structure of the friendship network and the communities shaped in an elementary school could be predicted if we know the total number of students

Bacterial community structure at the microscale in two different soils

Czech Academy of Sciences Publication Activity Database

Michelland, R.; Thioulouse, J.; Kyselková, Martina; Grundmann, G.L.

2016-01-01

Roč. 72, č. 3 (2016), s. 717-724 ISSN 0095-3628 Institutional support: RVO:60077344 Keywords : abundancy-occupancy relationship * bacteria community structure * frequency-occupancy relationship * microscale in soil * soil microbial diversity * soil structure Subject RIV: EH - Ecology, Behaviour Impact factor: 3.630, year: 2016

Factors affecting the bacterial community composition and heterotrophic production of Columbia River estuarine turbidity maxima.

Science.gov (United States)

Herfort, Lydie; Crump, Byron C; Fortunato, Caroline S; McCue, Lee Ann; Campbell, Victoria; Simon, Holly M; Baptista, António M; Zuber, Peter

2017-12-01

Estuarine turbidity maxima (ETM) function as hotspots of microbial activity and diversity in estuaries, yet, little is known about the temporal and spatial variability in ETM bacterial community composition. To determine which environmental factors affect ETM bacterial populations in the Columbia River estuary, we analyzed ETM bacterial community composition (Sanger sequencing and amplicon pyrosequencing of 16S rRNA gene) and bulk heterotrophic production ( 3 H-leucine incorporation rates). We collected water 20 times to cover five ETM events and obtained 42 samples characterized by different salinities, turbidities, seasons, coastal regimes (upwelling vs. downwelling), locations, and particle size. Spring and summer populations were distinct. All May samples had similar bacterial community composition despite having different salinities (1-24 PSU), but summer non-ETM bacteria separated into marine, freshwater, and brackish assemblages. Summer ETM bacterial communities varied depending on coastal upwelling or downwelling conditions and on the sampling site location with respect to tidal intrusion during the previous neap tide. In contrast to ETM, whole (>0.2 μm) and free-living (0.2-3 μm) assemblages of non-ETM waters were similar to each other, indicating that particle-attached (>3 μm) non-ETM bacteria do not develop a distinct community. Brackish water type (ETM or non-ETM) is thus a major factor affecting particle-attached bacterial communities. Heterotrophic production was higher in particle-attached than free-living fractions in all brackish waters collected throughout the water column during the rise to decline of turbidity through an ETM event (i.e., ETM-impacted waters). However, free-living communities showed higher productivity prior to or after an ETM event (i.e., non-ETM-impacted waters). This study has thus found that Columbia River ETM bacterial communities vary based on seasons, salinity, sampling location, and particle size, with the

Community Structure, Biodiversity, and Ecosystem Services in Treeline Whitebark Pine Communities: Potential Impacts from a Non-Native Pathogen

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Diana F. Tomback

2016-01-01

Full Text Available Whitebark pine (Pinus albicaulis has the largest and most northerly distribution of any white pine (Subgenus Strobus in North America, encompassing 18° latitude and 21° longitude in western mountains. Within this broad range, however, whitebark pine occurs within a narrow elevational zone, including upper subalpine and treeline forests, and functions generally as an important keystone and foundation species. In the Rocky Mountains, whitebark pine facilitates the development of krummholz conifer communities in the alpine-treeline ecotone (ATE, and thus potentially provides capacity for critical ecosystem services such as snow retention and soil stabilization. The invasive, exotic pathogen Cronartium ribicola, which causes white pine blister rust, now occurs nearly rangewide in whitebark pine communities, to their northern limits. Here, we synthesize data from 10 studies to document geographic variation in structure, conifer species, and understory plants in whitebark pine treeline communities, and examine the potential role of these communities in snow retention and regulating downstream flows. Whitebark pine mortality is predicted to alter treeline community composition, structure, and function. Whitebark pine losses in the ATE may also alter response to climate warming. Efforts to restore whitebark pine have thus far been limited to subalpine communities, particularly through planting seedlings with potential blister rust resistance. We discuss whether restoration strategies might be appropriate for treeline communities.

A meta-proteomics approach to study the interspecies interactions affecting microbial biofilm development in a model community

DEFF Research Database (Denmark)

Herschend, Jakob; Damholt, Zacharias Brimnes Visby; Marquard, Andrea Marion

2017-01-01

Microbial biofilms are omnipresent in nature and relevant to a broad spectrum of industries ranging from bioremediation and food production to biomedical applications. To date little is understood about how multi-species biofilm communities develop and function on a molecular level, due...... of fermentation and nitrogen pathways in Paenibacillus amylolyticus and Xanthomonas retroflexus may, however, indicate that competition for limited resources also affects community development. Overall our results demonstrate the multitude of pathways involved in biofilm formation in mixed communities....

Functional changes in littoral macroinvertebrate communities in response to watershed-level anthropogenic stress.

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Katya E Kovalenko

Full Text Available Watershed-scale anthropogenic stressors have profound effects on aquatic communities. Although several functional traits of stream macroinvertebrates change predictably in response to land development and urbanization, little is known about macroinvertebrate functional responses in lakes. We assessed functional community structure, functional diversity (Rao's quadratic entropy and voltinism in macroinvertebrate communities sampled across the full gradient of anthropogenic stress in Laurentian Great Lakes coastal wetlands. Functional diversity and voltinism significantly decreased with increasing development, whereas agriculture had smaller or non-significant effects. Functional community structure was affected by watershed-scale development, as demonstrated by an ordination analysis followed by regression. Because functional community structure affects energy flow and ecosystem function, and functional diversity is known to have important implications for ecosystem resilience to further environmental change, these results highlight the necessity of finding ways to remediate or at least ameliorate these effects.

Effects of chemical and biological pesticides on plant growth parameters and rhizospheric bacterial community structure in Vigna radiata.

Science.gov (United States)

Singh, Sunil; Gupta, Rashi; Sharma, Shilpi

2015-06-30

With increasing application of pesticides in agriculture, their non-target effects on soil microbial communities are critical to soil health maintenance. The present study aimed to evaluate the effects of chemical pesticides (chlorpyrifos and cypermethrin) and a biological pesticide (azadirachtin) on growth parameters and the rhizospheric bacterial community of Vigna radiata. Qualitative and quantitative analysis by PCR-denaturing gradient gel electrophoresis (DGGE) and q-PCR, respectively, of the 16S rRNA gene and transcript were performed to study the impact of these pesticides on the resident and active rhizospheric bacterial community. While plant parameters were not affected significantly by the pesticides, a shift in the bacterial community structure was observed with an adverse effect on the abundance of 16S rRNA gene and transcripts. Chlorpyrifos showed almost complete degradation toward the end of the experiment. These non-target impacts on soil ecosystems and the fact that the effects of the biopesticide mimic those of chemical pesticides raise serious concerns regarding their application in agriculture. Copyright © 2015 Elsevier B.V. All rights reserved.

Paradoxes of Social Networking in a Structured Web 2.0 Language Learning Community

Science.gov (United States)

Loiseau, Mathieu; Zourou, Katerina

2012-01-01

This paper critically inquires into social networking as a set of mechanisms and associated practices developed in a structured Web 2.0 language learning community. This type of community can be roughly described as learning spaces featuring (more or less) structured language learning resources displaying at least some notions of language learning…

Community investment in wind farms: funding structure effects in wind energy infrastructure development.

Science.gov (United States)

Beery, Joshua A; Day, Jennifer E

2015-03-03

Wind energy development is an increasingly popular form of renewable energy infrastructure in rural areas. Communities generally perceive socioeconomic benefits accrue and that community funding structures are preferable to corporate structures, yet lack supporting quantitative data to inform energy policy. This study uses the Everpower wind development, to be located in Midwestern Ohio, as a hypothetical modeling environment to identify and examine socioeconomic impact trends arising from corporate, community and diversified funding structures. Analysis of five National Renewable Energy Laboratory Jobs and Economic Development Impact models incorporating local economic data and review of relevant literature were conducted. The findings suggest that community and diversified funding structures exhibit 40-100% higher socioeconomic impact levels than corporate structures. Prioritization of funding sources and retention of federal tax incentives were identified as key elements. The incorporation of local shares was found to mitigate the negative effects of foreign private equity, local debt financing increased economic output and opportunities for private equity investment were identified. The results provide the groundwork for energy policies focused to maximize socioeconomic impacts while creating opportunities for inclusive economic participation and improved social acceptance levels fundamental to the deployment of renewable energy technology.

How does conversion of natural tropical rainforest ecosystems affect soil bacterial and fungal communities in the Nile river watershed of Uganda?

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Peter O Alele

Full Text Available Uganda's forests are globally important for their conservation values but are under pressure from increasing human population and consumption. In this study, we examine how conversion of natural forest affects soil bacterial and fungal communities. Comparisons in paired natural forest and human-converted sites among four locations indicated that natural forest soils consistently had higher pH, organic carbon, nitrogen, and calcium, although variation among sites was large. Despite these differences, no effect on the diversity of dominant taxa for either bacterial or fungal communities was detected, using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE. Composition of fungal communities did generally appear different in converted sites, but surprisingly, we did not observe a consistent pattern among sites. The spatial distribution of some taxa and community composition was associated with soil pH, organic carbon, phosphorus and sodium, suggesting that changes in soil communities were nuanced and require more robust metagenomic methods to understand the various components of the community. Given the close geographic proximity of the paired sampling sites, the similarity between natural and converted sites might be due to continued dispersal between treatments. Fungal communities showed greater environmental differentiation than bacterial communities, particularly according to soil pH. We detected biotic homogenization in converted ecosystems and substantial contribution of β-diversity to total diversity, indicating considerable geographic structure in soil biota in these forest communities. Overall, our results suggest that soil microbial communities are relatively resilient to forest conversion and despite a substantial and consistent change in the soil environment, the effects of conversion differed widely among sites. The substantial difference in soil chemistry, with generally lower nutrient quantity in converted

Seasonality and vertical structure of microbial communities in an ocean gyre

DEFF Research Database (Denmark)

Treusch, Alexander H; Vergin, Kevin L; Finlay, Liam A

2009-01-01

Vertical, seasonal and geographical patterns in ocean microbial communities have been observed in many studies, but the resolution of community dynamics has been limited by the scope of data sets, which are seldom up to the task of illuminating the highly structured and rhythmic patterns of change...

Comparing Metabolic Functionalities, Community Structures, and Dynamics of Herbicide-Degrading Communities Cultivated with Different Substrate Concentrations

DEFF Research Database (Denmark)

Gözdereliler, Erkin; Boon, Nico; Aamand, Jens

2013-01-01

Two 4-chloro-2-methylphenoxyacetic acid (MCPA)-degrading enrichment cultures selected from an aquifer on low (0.1 mg liter−1) or high (25 mg liter−1) MCPA concentrations were compared in terms of metabolic activity, community composition, population growth, and single cell physiology. Different...... community compositions and major shifts in community structure following exposure to different MCPA concentrations were observed using both 16S rRNA gene denaturing gradient gel electrophoresis fingerprinting and pyrosequencing. The communities also differed in their MCPA-mineralizing activities...... activity in cultures selected on low herbicide concentrations. This suggests that LNA bacteria may play a role in degradation of low herbicide concentrations in aquifers impacted by agriculture. This study shows that subpopulations of herbicide-degrading bacteria that are adapted to different pesticide...

Hexabromocyclododecane affects benthic-pelagic coupling in an experimental ecosystem

International Nuclear Information System (INIS)

Bradshaw, Clare; Näslund, Johan; Hansen, Joakim; Kozlowsky-Suzuki, Betina; Sundström, Bo; Gustafsson, Kerstin

2015-01-01

Hexabromocyclododecane (HBCDD) is an additive brominated flame retardant and a recognized PBT chemical. However, little is known about its effects on coastal species, and even less on ecosystem effects. We investigated the dose–response effects of HBCDD over 8 months in 1000 L experimental mesocosms assembled from coastal Baltic Sea ecosystem components. HBCDD was added via spiked plankton material and a range of structural and functional endpoints were measured during the experiment. Increasing HBCDD concentration decreased the biomass of large Macoma balthica, resulting in a decreased recirculation of nutrients to the water. Changes in plankton communities were also observed, either due to direct toxic HBCDD effects or indirect via changes in benthic-pelagic coupling of nutrients. Such complex ecosystem responses can only be quantified and understood by using realistic experimental set-ups, and including knowledge of system-specific ecological interactions. This is the first study of HBCDD effects on ecosystem level. - Graphical abstract: HBCDD caused direct effects on the population structure of sediment-dwelling Macoma balthica and on the plankton community. Indirect HBCDD effects via reduced nutrient remineralization by M. balthica affected nutrient levels in the water, likely leading to additional changes in plankton community structure. Seasonal effects were large and affected the whole system including nutrient dynamics as well as plankton community structure. Display Omitted - Highlights: • HBCDD caused effects on benthic population structure and ecosystem function. • Large seasonal effects highlight the importance of using relevant experimental conditions. • A realistic exposure pathway was applied by using HBCDD enriched plankton material. • This is the first study of HBCDD effects on ecosystem level, coupling benthic and pelagic communities. - HBCDD has a dose-dependent effect on benthic-pelagic coupling.

Fungal Community Structure as an Indicator of Soil Agricultural Management Effects in the Cerrado

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Alana de Almeida Valadares-Pereira

2017-11-01

Full Text Available ABSTRACT Forest-to-agriculture conversion and soil management practices for soybean cropping are frequently performed in the Cerrado (Brazilian tropical savanna. However, the effects of these practices on the soil microbial communities are still unknown. We evaluated and compared the fungal community structure in soil from soybean cropland with soil under native Cerrado vegetation at different times of the year in the Tocantins State. Soil samples were collected in two periods after planting (December and in two periods during the soybean reproductive growth stage (February. Concomitantly, soil samples were collected from an area under native Cerrado vegetation surrounding the agricultural area. The soil DNA was analyzed using a fingerprinting method termed Automated Ribosomal Intergenic Space Analysis (ARISA to assess the fungal community structure in the soil. Differences in the fungal community structure in the soil were found when comparing soybean cropland with the native vegetation (R = 0.932 for sampling 1 and R = 0.641 for sampling 2. Changes in the fungal community structure after management practices for soybean planting in Cerrado areas were related to changes in soil properties, mainly in copper, calcium, and iron contents, cation exchange capacity, base saturation, and calcium to magnesium ratio. These results show the changes in the fungal community structure in the soil as an effect of agricultural soil management in Cerrado vegetation in the state of Tocantins.

Physical Factors Correlate to Microbial Community Structure and Nitrogen Cycling Gene Abundance in a Nitrate Fed Eutrophic Lagoon.

Science.gov (United States)

Highton, Matthew P; Roosa, Stéphanie; Crawshaw, Josie; Schallenberg, Marc; Morales, Sergio E

2016-01-01

Nitrogenous run-off from farmed pastures contributes to the eutrophication of Lake Ellesmere, a large shallow lagoon/lake on the east coast of New Zealand. Tributaries periodically deliver high loads of nitrate to the lake which likely affect microbial communities therein. We hypothesized that a nutrient gradient would form from the potential sources (tributaries) creating a disturbance resulting in changes in microbial community structure. To test this we first determined the existence of such a gradient but found only a weak nitrogen (TN) and phosphorous gradient (DRP). Changes in microbial communities were determined by measuring functional potential (quantification of nitrogen cycling genes via nifH , nirS , nosZI , and nosZII using qPCR), potential activity (via denitrification enzyme activity), as well as using changes in total community (via 16S rRNA gene amplicon sequencing). Our results demonstrated that changes in microbial communities at a phylogenetic (relative abundance) and functional level (proportion of the microbial community carrying nifH and nosZI genes) were most strongly associated with physical gradients (e.g., lake depth, sediment grain size, sediment porosity) and not nutrient concentrations. Low nitrate influx at the time of sampling is proposed as a factor contributing to the observed patterns.

Physical factors correlate to microbial community structure and nitrogen cycling gene abundance in a nitrate fed eutrophic lagoon

Directory of Open Access Journals (Sweden)

Matthew Paul Highton

2016-10-01

Full Text Available Nitrogenous run-off from farmed pastures contributes to the eutrophication of Lake Ellesmere, a large shallow lagoon/lake on the east coast of New Zealand. Tributaries periodically deliver high loads of nitrate to the lake which likely affect microbial communities therein. We hypothesized that a nutrient gradient would form from the potential sources (tributaries creating a disturbance resulting in changes in microbial community structure. To test this we first determined the existence of such a gradient but found only a weak nitrogen (TN and phosphorous gradient (DRP. Changes in microbial communities were determined by measuring functional potential (quantification of nitrogen cycling genes via nifH, nirS, nosZI and nosZII using qPCR, potential activity (via denitrification enzyme activity, as well as using changes in total community (via 16S rRNA gene amplicon sequencing. Our results demonstrated that changes in microbial communities at a phylogenetic (relative abundance and functional level (proportion of the microbial community carrying nifH and nosZI genes were most strongly associated with physical gradients (e.g. lake depth, sediment grain size, sediment porosity and not nutrient concentrations. Low nitrate influx at the time of sampling is proposed as a factor contributing to the observed patterns.

The structure of microbial community in aggregates of a typical chernozem aggregates under contrasting variants of its agricultural use

Science.gov (United States)

Ivanova, E. A.; Kutovaya, O. V.; Tkhakakhova, A. K.; Chernov, T. I.; Pershina, E. V.; Markina, L. G.; Andronov, E. E.; Kogut, B. M.

2015-11-01

The taxonomic structure of microbiomes in aggregates of different sizes from typical chernozems was investigated using sequencing of the 16S rRNA gene. The aggregate fractions of 7 mm obtained by sieving of the soil samples at natural moisture were used for analysis. The highest prokaryote biomass (bacteria, archaea) was determined in the fractions permanent black fallow > permanent winter wheat. The greatest number of fungi was recorded in the fraction wheat. The system of agricultural use affected more significantly the structure of the prokaryote community in the chernozem than the size of aggregate fractions did. The most diverse microbial community was recorded in the soil samples of the fallow; the statistically significant maximums of the Shannon diversity indices and indices of phylogenetic diversity (PD) were recorded in the fractions <0.25 and 2-5 mm from the fallow soil. On the whole, the fine soil fractions (<0.25 mm) were characterized by higher diversity indices in comparison with those of the coarser aggregate fractions.

Dynamic structure of stock communities: a comparative study between stock returns and turnover rates

Science.gov (United States)

Su, Li-Ling; Jiang, Xiong-Fei; Li, Sai-Ping; Zhong, Li-Xin; Ren, Fei

2017-07-01

The detection of community structure in stock market is of theoretical and practical significance for the study of financial dynamics and portfolio risk estimation. We here study the community structures in Chinese stock markets from the aspects of both price returns and turnover rates, by using a combination of the PMFG and infomap methods based on a distance matrix. An empirical study using the overall data set shows that for both returns and turnover rates the largest communities are composed of specific industrial or conceptional sectors and the correlation inside a sector is generally larger than the correlation between different sectors. However, the community structure for turnover rates is more complex than that for returns, which indicates that the interactions between stocks revealed by turnover rates may contain more information. This conclusion is further confirmed by the analysis of the changes in the dynamics of community structures over five sub-periods. Sectors like banks, real estate, health care and New Shanghai take turns to comprise a few of the largest communities in different sub-periods, and more interestingly several specific sectors appear in the communities with different rank orders for returns and turnover rates even in the same sub-period. To better understand their differences, a comparison between the evolution of the returns and turnover rates of the stocks from these sectors is conducted. We find that stock prices only had large changes around important events while turnover rates surged after each of these events relevant to specific sectors, which shows strong evidence that the turnover rates are more susceptible to exogenous shocks than returns and its measurement for community detection may contain more useful information about market structure.

Plant community structure regulates responses of prairie soil respiration to decadal experimental warming.

Science.gov (United States)

Xu, Xia; Shi, Zheng; Li, Dejun; Zhou, Xuhui; Sherry, Rebecca A; Luo, Yiqi

2015-10-01

Soil respiration is recognized to be influenced by temperature, moisture, and ecosystem production. However, little is known about how plant community structure regulates responses of soil respiration to climate change. Here, we used a 13-year field warming experiment to explore the mechanisms underlying plant community regulation on feedbacks of soil respiration to climate change in a tallgrass prairie in Oklahoma, USA. Infrared heaters were used to elevate temperature about 2 °C since November 1999. Annual clipping was used to mimic hay harvest. Our results showed that experimental warming significantly increased soil respiration approximately from 10% in the first 7 years (2000-2006) to 30% in the next 6 years (2007-2012). The two-stage warming stimulation of soil respiration was closely related to warming-induced increases in ecosystem production over the years. Moreover, we found that across the 13 years, warming-induced increases in soil respiration were positively affected by the proportion of aboveground net primary production (ANPP) contributed by C3 forbs. Functional composition of the plant community regulated warming-induced increases in soil respiration through the quantity and quality of organic matter inputs to soil and the amount of photosynthetic carbon (C) allocated belowground. Clipping, the interaction of clipping with warming, and warming-induced changes in soil temperature and moisture all had little effect on soil respiration over the years (all P > 0.05). Our results suggest that climate warming may drive an increase in soil respiration through altering composition of plant communities in grassland ecosystems. © 2015 John Wiley & Sons Ltd.

Structure of a microbial community in soil after prolonged addition of low levels of simulated acid rain

Science.gov (United States)

Pennanen; Fritze; Vanhala; Kiikkila; Neuvonen; Baath

1998-06-01

Humus samples were collected 12 growing seasons after the start of a simulated acid rain experiment situated in the subarctic environment. The acid rain was simulated with H2SO4, a combination of H2SO4 and HNO3, and HNO3 at two levels of moderate acidic loads close to the natural anthropogenic pollution levels of southern Scandinavia. The higher levels of acid applications resulted in acidification, as defined by humus chemistry. The concentrations of base cations decreased, while the concentrations of exchangeable H+, Al, and Fe increased. Humus pH decreased from 3.83 to 3.65. Basal respiration decreased with decreasing humus pH, and total microbial biomass, measured by substrate-induced respiration and total amount of phospholipid fatty acids (PLFA), decreased slightly. An altered PLFA pattern indicated a change in the microbial community structure at the higher levels of acid applications. In general, branched fatty acids, typical of gram-positive bacteria, increased in the acid plots. PLFA analysis performed on the bacterial community growing on agar plates also showed that the relative amount of PLFA specific for gram-positive bacteria increased due to the acidification. The changed bacterial community was adapted to the more acidic environment in the acid-treated plots, even though bacterial growth rates, estimated by thymidine and leucine incorporation, decreased with pH. Fungal activity (measured as acetate incorporation into ergosterol) was not affected. This result indicates that bacteria were more affected than fungi by the acidification. The capacity of the bacterial community to utilize 95 different carbon sources was variable and only showed weak correlations to pH. Differences in the toxicities of H2SO4 and HNO3 for the microbial community were not found.

Spatial and temporal repeatability in parasite community structure of tropical fish hosts.

Science.gov (United States)

Vidal-Martínez, V M; Poulin, R

2003-10-01

An assessment is made of the repeatability of parasite community structure in space for a marine fish, and in space and time for a freshwater fish from south-eastern Mexico. The marine fish species was the red grouper, Epinephelus morio (collected from 9 localities), and the freshwater species was the cichlid, Cichlasoma urophthalmus (collected from 6 localities: including monthly at 2 localities for 1 year, and bimonthly at 1 locality in 1990 and 1999). Pairwise interspecific associations and analyses of nested patterns in the distributions of parasite species among hosts were used in both fish species, with comparisons over time made only with the cichlid. Positive interspecific associations, and nested patterns were noted in some localities for both fish species, and/or at some sampling times for the cichlid fish. However, non-random patterns in the structure of parasite communities in these 2 host species only were observed sporadically. When present, nestedness in both fish species was apparently linked with a positive association between total infection intensities and fish size. Additionally, adjacent localities were more likely to display similar parasite community structure than distant ones. This preliminary result suggests that distance between localities is an important determinant of predictability in parasite community structure.

Change in atmospheric deposition during last half century and its impact on lichen community structure in Eastern Himalaya.

Science.gov (United States)

Bajpai, Rajesh; Mishra, Seema; Dwivedi, Sanjay; Upreti, Dalip Kumar

2016-08-09

Climatic fluctuations largely affects species turnover and cause major shifts of terrestrial ecosystem. In the present study the five decade old herbarium specimens of lichens were compared with recent collection from Darjeeling district with respect to elements, PAHs accumulation and carbon isotope composition (δ(13)C) to explore the changes in climatic conditions and its impact on lichen flora. The δ(13)C has increased in recent specimens which is in contrast to the assumption that anthropogenic emission leads to δ(13)C depletion in air and increased carbon discrimination in flora. Study clearly demonstrated an increase in anthropogenic pollution and drastic decrease in precipitation while temperature showed abrupt changes during the past five decades resulting in significant change in lichen community structure. The Usneoid and Pertusorioid communities increased, while Physcioid and Cyanophycean decreased, drastically. Lobarian abolished from the study area, however, Calcicoid has been introduced in the recent past. Probably, post-industrial revolution, the abrupt changes in the environment has influenced CO2 diffusion and/C fixation of (lower) plants either as an adaptation strategy or due to toxicity of pollutants. Thus, the short term studies (≤5 decades) might reflect recent micro-environmental condition and lichen community structure can be used as model to study the global climate change.

Change in atmospheric deposition during last half century and its impact on lichen community structure in Eastern Himalaya

Science.gov (United States)

Bajpai, Rajesh; Mishra, Seema; Dwivedi, Sanjay; Upreti, Dalip Kumar

2016-08-01

Climatic fluctuations largely affects species turnover and cause major shifts of terrestrial ecosystem. In the present study the five decade old herbarium specimens of lichens were compared with recent collection from Darjeeling district with respect to elements, PAHs accumulation and carbon isotope composition (δ13C) to explore the changes in climatic conditions and its impact on lichen flora. The δ13C has increased in recent specimens which is in contrast to the assumption that anthropogenic emission leads to δ13C depletion in air and increased carbon discrimination in flora. Study clearly demonstrated an increase in anthropogenic pollution and drastic decrease in precipitation while temperature showed abrupt changes during the past five decades resulting in significant change in lichen community structure. The Usneoid and Pertusorioid communities increased, while Physcioid and Cyanophycean decreased, drastically. Lobarian abolished from the study area, however, Calcicoid has been introduced in the recent past. Probably, post-industrial revolution, the abrupt changes in the environment has influenced CO2 diffusion and/C fixation of (lower) plants either as an adaptation strategy or due to toxicity of pollutants. Thus, the short term studies (≤5 decades) might reflect recent micro-environmental condition and lichen community structure can be used as model to study the global climate change.

Immunization of networks with community structure

International Nuclear Information System (INIS)

Masuda, Naoki

2009-01-01

In this study, an efficient method to immunize modular networks (i.e. networks with community structure) is proposed. The immunization of networks aims at fragmenting networks into small parts with a small number of removed nodes. Its applications include prevention of epidemic spreading, protection against intentional attacks on networks, and conservation of ecosystems. Although preferential immunization of hubs is efficient, good immunization strategies for modular networks have not been established. On the basis of an immunization strategy based on eigenvector centrality, we develop an analytical framework for immunizing modular networks. To this end, we quantify the contribution of each node to the connectivity in a coarse-grained network among modules. We verify the effectiveness of the proposed method by applying it to model and real networks with modular structure.

Physicochemical conditions in affecting the distribution of spring phytoplankton community

Science.gov (United States)

Wei, Yuqiu; Liu, Haijiao; Zhang, Xiaodong; Xue, Bing; Munir, Sonia; Sun, Jun

2017-11-01

To better understand the physicochemical conditions in affecting regional distribution of phytoplankton community, one research cruise was carried out in the Bohai Sea and Yellow Sea during 3rd and 23th May, 2010. The phytoplankton community, including Bacillariophyta (105 taxa), Pyrrophyta (54 taxa), Chrysophyta (1 taxon) and Chlorophyta (2 taxa), had been identified and clearly described from six ecological provinces. And, the six ecological provinces were partitioned based on the top twenty dominant species related with notable physicochemical parameters. In general, the regional distributions of phytoplankton ecological provinces were predominantly influenced by the physicochemical properties induced by the variable water masses and circulations. The predominant diatoms in most of water samples showed well adaptability in turbulent and eutrophic conditions. However, several species of dinoflagellates e.g., Protoperidinium conicum, Protoperidinium triestinum, Protoperidinium sp. and Gymnodinium lohmanni preferred warmer, saltier and nutrient-poor environment. Moreover, the dinoflagellates with high frequency in the Yellow Sea might be transported from the Yellow Sea Warm Current. The horizontal distribution of phytoplankton was depicted by diatoms and controlled by phosphate concentration, while the vertical distribution was mainly supported by light and nutrients availability in the subsurface and bottom layers, respectively.

Improvement of the SEP protocol based on community structure of node degree

Science.gov (United States)

Li, Donglin; Wei, Suyuan

2017-05-01

Analyzing the Stable election protocol (SEP) in wireless sensor networks and aiming at the problem of inhomogeneous cluster-heads distribution and unreasonable cluster-heads selectivity and single hop transmission in the SEP, a SEP Protocol based on community structure of node degree (SEP-CSND) is proposed. In this algorithm, network node deployed by using grid deployment model, and the connection between nodes established by setting up the communication threshold. The community structure constructed by node degree, then cluster head is elected in the community structure. On the basis of SEP, the node's residual energy and node degree is added in cluster-heads election. The information is transmitted with mode of multiple hops between network nodes. The simulation experiments showed that compared to the classical LEACH and SEP, this algorithm balances the energy consumption of the entire network and significantly prolongs network lifetime.

Implementing a structured triage system at a community health ...

African Journals Online (AJOL)

Implementing a structured triage system at a community health centre using Kaizen. ... and a resultant increased workload for doctors; management is concerned ... Aim: We set out to standardise the triage process and to manage unbooked ...

Global and local targeted immunization in networks with community structure

International Nuclear Information System (INIS)

Yan, Shu; Tang, Shaoting; Pei, Sen; Zheng, Zhiming; Fang, Wenyi

2015-01-01

Immunization plays an important role in the field of epidemic spreading in complex networks. In previous studies, targeted immunization has been proved to be an effective strategy. However, when extended to networks with community structure, it is unknown whether the superior strategy is to vaccinate the nodes who have the most connections in the entire network (global strategy), or those in the original community where epidemic starts to spread (local strategy). In this work, by using both analytic approaches and simulations, we observe that the answer depends on the closeness between communities. If communities are tied closely, the global strategy is superior to the local strategy. Otherwise, the local targeted immunization is advantageous. The existence of a transitional value of closeness implies that we should adopt different strategies. Furthermore, we extend our investigation from two-community networks to multi-community networks. We consider the mode of community connection and the location of community where epidemic starts to spread. Both simulation results and theoretical predictions show that local strategy is a better option for immunization in most cases. But if the epidemic begins from a core community, global strategy is superior in some cases. (paper)

Long-term survey of heavy-metal pollution, biofilm contamination and diatom community structure in the Riou Mort watershed, South-West France

International Nuclear Information System (INIS)

Morin, S.; Duong, T.T.; Dabrin, A.; Coynel, A.; Herlory, O.; Baudrimont, M.; Delmas, F.; Durrieu, G.; Schaefer, J.; Winterton, P.; Blanc, G.; Coste, M.

2008-01-01

In a metal-polluted stream in the Riou Mort watershed in SW France, periphytic biofilm was analyzed for diatom cell densities and taxonomic composition, dry weight and metal bio-accumulation (cadmium and zinc). Periphytic diatom communities were affected by the metal but displayed induced tolerance, seen through structural impact (dominance of small, adnate species) as well as morphological abnormalities particularly in the genera Ulnaria and Fragilaria. Species assemblages were characterized by taxa known to occur in metal-polluted environments, and shifts in the community structure expressed seasonal patterns: high numbers of Eolimna minima, Nitzschia palea and Pinnularia parvulissima were recorded in Summer and Autumn, whereas the species Surirella brebissonii, Achnanthidium minutissimum, Navicula lanceolata and Surirella angusta were dominant in Winter and Spring. Commonly used indices such as the Shannon diversity index and Specific Pollution Sensitivity Index reflected the level of pollution and suggest seasonal periodicity, the lowest diversities being observed in Summer. - Periphytic biofilm diatom communities are suitable indicators for the bioassay of elevated levels of metals in contaminated river water

Introducing SONS, a tool for operational taxonomic unit-based comparisons of microbial community memberships and structures.

Science.gov (United States)

Schloss, Patrick D; Handelsman, Jo

2006-10-01

The recent advent of tools enabling statistical inferences to be drawn from comparisons of microbial communities has enabled the focus of microbial ecology to move from characterizing biodiversity to describing the distribution of that biodiversity. Although statistical tools have been developed to compare community structures across a phylogenetic tree, we lack tools to compare the memberships and structures of two communities at a particular operational taxonomic unit (OTU) definition. Furthermore, current tests of community structure do not indicate the similarity of the communities but only report the probability of a statistical hypothesis. Here we present a computer program, SONS, which implements nonparametric estimators for the fraction and richness of OTUs shared between two communities.

A structured patient identification model for medication therapy management services in a community pharmacy.

Science.gov (United States)

Pagano, Gina M; Groves, Brigid K; Kuhn, Catherine H; Porter, Kyle; Mehta, Bella H

To describe the development and implementation of a structured patient identification model for medication therapy management (MTM) services within traditional dispensing activities of a community pharmacy to facilitate pharmacist-provided completion of MTM services. A daily clinical opportunity report was developed as a structured model to identify MTM opportunities daily for all MTM-eligible patients expecting to pick up a prescription. Pharmacy staff was trained and the standardized model was implemented at study sites. One hundred nineteen grocery store-based community pharmacies throughout Ohio, West Virginia, and Michigan. A structured patient identification model in a community pharmacy consists of reviewing a clinical opportunity report, identifying interventions for MTM-eligible patients, and possibly collaborating with an interdisciplinary team. This model allows pharmacists to increase MTM cases performed by providing a structured process for identifying MTM-eligible patients and completing MTM services. The development and implementation of a structured patient identification model in the community pharmacy was completed and consists of pharmacists reviewing a clinical opportunity report to identify MTM opportunities and perform clinical interventions for patients. In a 3-month pre- and post-implementation comparison, there was a 49% increase in the number of MTM services provided by pharmacists (P < 0.001). A structured patient identification model in the community pharmacy was associated with an increase in the amount of MTM services provided by pharmacists. This method could be a useful tool at a variety of community pharmacies to solve challenges associated with MTM completion. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Zooplankton composition and community structure in Lake Tiga ...

African Journals Online (AJOL)

Zooplankton in Lake Tiga was identified and its community structure assessed between March 2009 and March 2011. A total of 54 species of zooplankton was recorded, comprising two species of Protozoa, 26 species of Rotifera, eight species of Copepoda, 11 species of Cladocera, four species of Ostracoda and three ...

Metabolic and demographic feedbacks shape the emergent spatial structure and function of microbial communities.

Directory of Open Access Journals (Sweden)

Sylvie Estrela

Full Text Available Microbes are predominantly found in surface-attached and spatially structured polymicrobial communities. Within these communities, microbial cells excrete a wide range of metabolites, setting the stage for interspecific metabolic interactions. The links, however, between metabolic and ecological interactions (functional relationships, and species spatial organization (structural relationships are still poorly understood. Here, we use an individual-based modelling framework to simulate the growth of a two-species surface-attached community where food (resource is traded for detoxification (service and investigate how metabolic constraints of individual species shape the emergent structural and functional relationships of the community. We show that strong metabolic interdependence drives the emergence of mutualism, robust interspecific mixing, and increased community productivity. Specifically, we observed a striking and highly stable emergent lineage branching pattern, generating a persistent lineage mixing that was absent when the metabolic exchange was removed. These emergent community properties are driven by demographic feedbacks, such that aid from neighbouring cells directly enhances focal cell growth, which in turn feeds back to neighbour fecundity. In contrast, weak metabolic interdependence drives conflict (exploitation or competition, and in turn greater interspecific segregation. Together, these results support the idea that species structural and functional relationships represent the net balance of metabolic interdependencies.

Comparing factors of vulnerability and resilience of mountain communities affected by landslides in Eastern Nepal

Science.gov (United States)

Sudmeier-Rieux, Karen; Dubois, Jerome; Jaboyedoff, Michel

2010-05-01

This paper describes a methodology for assessing and quantifying vulnerability and resilience of mountain communities in Eastern Nepal increasingly affected by landslides and flooding. We are interested in improving our understanding of the complex interactions between land use, landslides and multiple dimensions of risk, vulnerability and resilience to better target risk management strategies. Our approach is based on assessing underlying social, ecological and physical factors that cause vulnerability and on the other hand, those resources and capacities that increase resilience. Increasing resilience to disasters is frequently used by NGOs, governments and donors as the main goal of disaster risk reduction policies and practices. If we are to increase resilience to disasters, we need better guidance and tools for defining, assessing and monitoring its parameters. To do so, we are establishing a methodology for quantifying and mapping an index of resilience to compare resilience factors between households and communities based on interdisciplinary research methods: remote sensing, GIS, qualitative and quantitative risk assessments, participatory risk mapping, household questionnaires and focus groups discussions. Our study applied this methodology to several communities in Eastern Nepal where small, frequent landslides are greatly affecting rural lives and livelihoods. These landslides are not captured by headlines or official statistics but are examples of cumulative, hidden disasters, which are impacting everyday life and rural poverty in the Himalayas. Based on experience, marginalized populations are often aware of the physical risks and the limitations of their land. However, they continue to live in dangerous places out of necessity and for the economic or infrastructure opportunities offered. We compare two communities in Nepal, both affected by landslides but with different land use, migration patterns, education levels, social networks, risk reduction

Community structure of elasmobranchs in estuaries along the northwest Gulf of Mexico

Science.gov (United States)

Plumlee, Jeffrey D.; Dance, Kaylan M.; Matich, Philip; Mohan, John A.; Richards, Travis M.; TinHan, Thomas C.; Fisher, Mark R.; Wells, R. J. David

2018-05-01

Estuaries promote high levels of productivity and biodiversity by providing habitat for many biological communities due to their wide range of environmental conditions. Estuarine systems serve as nurseries, areas for parturition, and feeding grounds for elasmobranchs. However, estuaries face an array of anthropogenic pressures, including overfishing, altered flow regimes, pollution, and habitat destruction. Given the vulnerability of estuarine ecosystems, observing long-term changes in community structure is essential to understanding the effects of anthropogenic stressors. Elasmobranch community structure was analyzed among eight estuaries in the northwest Gulf of Mexico to evaluate spatial and temporal variability in species abundance and diversity using bi-annual fisheries independent gillnet survey data over three decades (1985-2014). Ten species comprised 99.4% of elasmobranchs caught which included 35.3% bull sharks (Carcharhinus leucas), 18.1% bonnetheads (Sphyrna tiburo), 17.0% cownose rays (Rhinoptera bonasus), 13.4% blacktip sharks (Carcharhinus limbatus), 5.9% Atlantic stingrays (Dasyatis sabina), 3.1% Atlantic sharpnose sharks (Rhizoprionodon terraenovae), 2.7% spinner sharks (Carcharhinus brevipinna), 2.1% scalloped hammerheads (Sphyrna lewini), 1.7% finetooth sharks (Carcharhinus isodon), and 0.7% lemon sharks (Negaprion brevirostris). During the study period, elasmobranch community structure changed among estuaries and among decades. Bull sharks, bonnetheads, cownose rays, blacktip sharks, and spinner sharks all increased in abundance during the study period, whereas finetooth sharks and lemon sharks decreased over time. Higher latitude estuaries were dominated by bull sharks while lower latitude estuaries were dominated by cownose rays. Salinity was the most important environmental variable in predicting individual elasmobranch species abundance (deviance explained: 14.4 ± 6.5 SD), while temperature and depth also played a role in shaping community

FACTORS AFFECTING ENGLISH AS A FOREIGN LANGUAGE TEACHERS’ PARTICIPATION IN ONLINE COMMUNITIES OF PRACTICE: THE CASE OF WEBHEADS IN ACTION

Directory of Open Access Journals (Sweden)

Ali BOSTANCIOĞLU

2016-12-01

Full Text Available An online community of practice (OCoP is a group of people, who are brought together by a shared interest and with the aim of deepening their understanding of an area of knowledge through regular interactions facilitated by computer mediated communication (CMC tools. An OCoP potentially provides teachers with those elements of effective professional development (PD, cited in the literature, such as; collaboration, opportunities for mentoring, and sustainability over time. In this sense, OCoPs can be considered as a viable alternative for teacher PD. If OCoPs are to become an alternative approach to teacher PD then it is important to understand what factors affect teachers’ participation in such communities. Therefore, through the case of Webheads in Action (WiA OCoP, this study aimed to identify what factors contribute towards creating successful OCoPs. Members’ interactions in WiA’s public group page were collated over a period of nine months and interviews with 24 members of the community (4 core, 9 active, 11 peripheral were used to gather the data. Two major themes emerged in relation to factors affecting members’ participation in this OCoP. The first one was identified as the creation of a sense of belonging to the community which was achieved through various means such as having an initiation process and fostering trust and an inclusive community environment through community norms. The second was dynamism inherent in the community which manifested itself as new topics that kept members interested and participating, and a flow of continuous member recruitment to the community. In conclusion, this study highlighted the importance of the socio-affective dimension for designing and sustaining OCoPs.

Microbial community structure of leaf-cutter ant fungus gardens and refuse dumps.

Science.gov (United States)

Scott, Jarrod J; Budsberg, Kevin J; Suen, Garret; Wixon, Devin L; Balser, Teri C; Currie, Cameron R

2010-03-29

Leaf-cutter ants use fresh plant material to grow a mutualistic fungus that serves as the ants' primary food source. Within fungus gardens, various plant compounds are metabolized and transformed into nutrients suitable for ant consumption. This symbiotic association produces a large amount of refuse consisting primarily of partly degraded plant material. A leaf-cutter ant colony is thus divided into two spatially and chemically distinct environments that together represent a plant biomass degradation gradient. Little is known about the microbial community structure in gardens and dumps or variation between lab and field colonies. Using microbial membrane lipid analysis and a variety of community metrics, we assessed and compared the microbiota of fungus gardens and refuse dumps from both laboratory-maintained and field-collected colonies. We found that gardens contained a diverse and consistent community of microbes, dominated by Gram-negative bacteria, particularly gamma-Proteobacteria and Bacteroidetes. These findings were consistent across lab and field gardens, as well as host ant taxa. In contrast, dumps were enriched for Gram-positive and anaerobic bacteria. Broad-scale clustering analyses revealed that community relatedness between samples reflected system component (gardens/dumps) rather than colony source (lab/field). At finer scales samples clustered according to colony source. Here we report the first comparative analysis of the microbiota from leaf-cutter ant colonies. Our work reveals the presence of two distinct communities: one in the fungus garden and the other in the refuse dump. Though we find some effect of colony source on community structure, our data indicate the presence of consistently associated microbes within gardens and dumps. Substrate composition and system component appear to be the most important factor in structuring the microbial communities. These results thus suggest that resident communities are shaped by the plant degradation

Solidago canadensis invasion affects soil N-fixing bacterial communities in heterogeneous landscapes in urban ecosystems in East China.

Science.gov (United States)

Wang, Congyan; Jiang, Kun; Zhou, Jiawei; Wu, Bingde

2018-03-12

Soil nitrogen-fixing bacterial communities (SNB) can increase the level of available soil N via biological N-fixation to facilitate successful invasion of several invasive plant species (IPS). Meanwhile, landscape heterogeneity can greatly enhance regional invasibility and increase the chances of successful invasion of IPS. Thus, it is important to understand the soil micro-ecological mechanisms driving the successful invasion of IPS in heterogeneous landscapes. This study performed cross-site comparisons, via metagenomics, to comprehensively analyze the effects of Solidago canadensis invasion on SNB in heterogeneous landscapes in urban ecosystems. Rhizospheric soil samples of S. canadensis were obtained from nine urban ecosystems [Three replicate quadrats (including uninvaded sites and invaded sites) for each type of urban ecosystem]. S. canadensis invasion did not significantly affect soil physicochemical properties, the taxonomic diversity of plant communities, or the diversity and richness of SNB. However, some SNB taxa (i.e., f_Micromonosporaceae, f_Oscillatoriaceae, and f_Bacillaceae) changed significantly with S. canadensis invasion. Thus, S. canadensis invasion may alter the community structure, rather than the diversity and richness of SNB, to facilitate its invasion process. Of the nine urban ecosystems, the diversity and richness of SNB was highest in farmland wasteland. Accordingly, the community invasibility of farmland wasteland may be higher than that of the other types of urban ecosystem. In brief, landscape heterogeneity, rather than S. canadensis invasion, was the strongest controlling factor for the diversity and richness of SNB. One possible reason may be the differences in soil electrical conductivity and the taxonomic diversity of plant communities in the nine urban ecosystems, which can cause notable shifts in the diversity and richness of SNB. Copyright © 2018 Elsevier B.V. All rights reserved.

Impacts of chemical gradients on microbial community structure

DEFF Research Database (Denmark)

Chen, Jianwei; Hanke, Anna; Tegetmeyer, Halina E

2017-01-01

Succession of redox processes is sometimes assumed to define a basic microbial community structure for ecosystems with oxygen gradients. In this paradigm, aerobic respiration, denitrification, fermentation and sulfate reduction proceed in a thermodynamically determined order, known as the 'redox ...... Journal advance online publication, 17 January 2017; doi:10.1038/ismej.2016.175....

Effect of size heterogeneity on community identification in complex networks

Energy Technology Data Exchange (ETDEWEB)

Danon, L.; Diaz-Guilera, A.; Arenas, A.

2008-01-01

Identifying community structure can be a potent tool in the analysis and understanding of the structure of complex networks. Up to now, methods for evaluating the performance of identification algorithms use ad-hoc networks with communities of equal size. We show that inhomogeneities in community sizes can and do affect the performance of algorithms considerably, and propose an alternative method which takes these factors into account. Furthermore, we propose a simple modification of the algorithm proposed by Newman for community detection (Phys. Rev. E 69 066133) which treats communities of different sizes on an equal footing, and show that it outperforms the original algorithm while retaining its speed.

Analysis of bacterial and fungal community structure in replant ...

African Journals Online (AJOL)

user

2012-06-19

Jun 19, 2012 ... roots and few functional root hairs. Normally, RDS is ... community structure of microbes, including microbes as yet unable to be cultured. ..... Due to the fact that. Method 3 in this paper has the advantages in combining.

Quality of Irrigation Water Affects Soil Functionality and Bacterial Community Stability in Response to Heat Disturbance.

Science.gov (United States)

Frenk, Sammy; Hadar, Yitzhak; Minz, Dror

2018-02-15

Anthropogenic activities alter the structure and function of a bacterial community. Furthermore, bacterial communities structured by the conditions the anthropogenic activities present may consequently reduce their stability in response to an unpredicted acute disturbance. The present mesocosm-scale study exposed soil bacterial communities to different irrigation water types, including freshwater, fertilized freshwater, treated wastewater, and artificial wastewater, and evaluated their response to a disturbance caused by heat. These effectors may be considered deterministic and stochastic forces common in agricultural operations of arid and semiarid regions. Bacterial communities under conditions of high mineral and organic carbon availability (artificial wastewater) differed from the native bacterial community and showed a proteobacterial dominance. These bacterial communities had a lower resistance to the heat treatment disturbance than soils under conditions of low resource availability (high-quality treated wastewater or freshwater). The latter soil bacterial communities showed a higher abundance of operational taxonomic units (OTUs) classified as Bacilli These results were elucidated by soil under conditions of high resource availability, which lost higher degrees of functional potential and had a greater bacterial community composition change. However, the functional resilience, after the disturbance ended, was higher under a condition of high resource availability despite the bacterial community composition shift and the decrease in species richness. The functional resilience was directly connected to the high growth rates of certain Bacteroidetes and proteobacterial groups. A high stability was found in samples that supported the coexistence of both resistant OTUs and fast-growing OTUs. IMPORTANCE This report presents the results of a study employing a hypothesis-based experimental approach to reveal the forces involved in determining the stability of a

Earthworms modify microbial community structure and accelerate maize stover decomposition during vermicomposting.

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Chen, Yuxiang; Zhang, Yufen; Zhang, Quanguo; Xu, Lixin; Li, Ran; Luo, Xiaopei; Zhang, Xin; Tong, Jin

2015-11-01

In the present study, maize stover was vermicomposted with the epigeic earthworm Eisenia fetida. The results showed that, during vermicomposting process, the earthworms promoted decomposition of maize stover. Analysis of microbial communities of the vermicompost by high-throughput pyrosequencing showed more complex bacterial community structure in the substrate treated by the earthworms than that in the control group. The dominant microbial genera in the treatment with the earthworms were Pseudoxanthomonas, Pseudomonas, Arthrobacter, Streptomyces, Cryptococcus, Guehomyces, and Mucor. Compared to the control group, the relative abundance of lignocellulose degradation microorganisms increased. The results indicated that the earthworms modified the structure of microbial communities during vermicomposting process, activated the growth of lignocellulose degradation microorganisms, and triggered the lignocellulose decomposition.

Size Matters: Assessing Optimum Soil Sample Size for Fungal and Bacterial Community Structure Analyses Using High Throughput Sequencing of rRNA Gene Amplicons

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Christopher Ryan Penton

2016-06-01

Full Text Available We examined the effect of different soil sample sizes obtained from an agricultural field, under a single cropping system uniform in soil properties and aboveground crop responses, on bacterial and fungal community structure and microbial diversity indices. DNA extracted from soil sample sizes of 0.25, 1, 5 and 10 g using MoBIO kits and from 10 and 100 g sizes using a bead-beating method (SARDI were used as templates for high-throughput sequencing of 16S and 28S rRNA gene amplicons for bacteria and fungi, respectively, on the Illumina MiSeq and Roche 454 platforms. Sample size significantly affected overall bacterial and fungal community structure, replicate dispersion and the number of operational taxonomic units (OTUs retrieved. Richness, evenness and diversity were also significantly affected. The largest diversity estimates were always associated with the 10 g MoBIO extractions with a corresponding reduction in replicate dispersion. For the fungal data, smaller MoBIO extractions identified more unclassified Eukaryota incertae sedis and unclassified glomeromycota while the SARDI method retrieved more abundant OTUs containing unclassified Pleosporales and the fungal genera Alternaria and Cercophora. Overall, these findings indicate that a 10 g soil DNA extraction is most suitable for both soil bacterial and fungal communities for retrieving optimal diversity while still capturing rarer taxa in concert with decreasing replicate variation.

Microbes as engines of ecosystem function: when does community structure enhance predictions of ecosystem processes?

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Emily B. Graham

2016-02-01

Full Text Available Microorganisms are vital in mediating the earth’s biogeochemical cycles; yet, despite our rapidly increasing ability to explore complex environmental microbial communities, the relationship between microbial community structure and ecosystem processes remains poorly understood. Here, we address a fundamental and unanswered question in microbial ecology: ‘When do we need to understand microbial community structure to accurately predict function?’ We present a statistical analysis investigating the value of environmental data and microbial community structure independently and in combination for explaining rates of carbon and nitrogen cycling processes within 82 global datasets. Environmental variables were the strongest predictors of process rates but left 44% of variation unexplained on average, suggesting the potential for microbial data to increase model accuracy. Although only 29% of our datasets were significantly improved by adding information on microbial community structure, we observed improvement in models of processes mediated by narrow phylogenetic guilds via functional gene data, and conversely, improvement in models of facultative microbial processes via community diversity metrics. Our results also suggest that microbial diversity can strengthen predictions of respiration rates beyond microbial biomass parameters, as 53% of models were improved by incorporating both sets of predictors compared to 35% by microbial biomass alone. Our analysis represents the first comprehensive analysis of research examining links between microbial community structure and ecosystem function. Taken together, our results indicate that a greater understanding of microbial communities informed by ecological principles may enhance our ability to predict ecosystem process rates relative to assessments based on environmental variables and microbial physiology.

Patterns of natural fungal community assembly during initial decay of coniferous and broadleaf tree logs

NARCIS (Netherlands)

van der Wal, A.; Klein Gunnewiek, P.J.A.; Cornelissen, J.H.C.; Crowther, T.W.; de Boer, W..

2016-01-01

Community assembly processes do not only influence community structure, but can also affect ecosystem processes. To understand the effect of initial community development on ecosystem processes, we studied natural fungal community dynamics during initial wood decay. We hypothesize that fungal

Patterns of natural fungal community assembly during initial decay of coniferous and broadleaf tree logs

NARCIS (Netherlands)

Wal, van der Annemieke; Klein Gunnewiek, P.J.A.; Cornelissen, J.H.C.; Crowther, Thomas W.; Boer, de Wietse

2016-01-01

Community assembly processes do not only influence community structure, but can also affect ecosystem processes. To understand the effect of initial community development on ecosystem processes, we studied natural fungal community dynamics during initial wood decay. We hypothesize that fungal

Microbial biomass, community structure and metal tolerance of a naturally Pb-enriched forest soil.

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Bååth, E; Díaz-Raviña, M; Bakken, L R

2005-11-01

The effect of long-term elevated soil Pb levels on soil microbiota was studied at a forest site in Norway, where the soil has been severely contaminated with Pb since the last period of glaciation (several thousand years). Up to 10% Pb (total amount, w/w) has been found in the top layer. The microbial community was drastically affected, as judged from changes in the phospholipid fatty acid (PLFA) pattern. Specific PLFAs that were high in Pb-enriched soil were branched (especially br17:0 and br18:0), whereas PLFAs common in eukaryotic organisms such as fungi (18:2omega6,9 and 20:4) were low compared with levels at adjacent, uncontaminated sites. Congruent changes in the PLFA pattern were found upon analyzing the culturable part of the bacterial community. The high Pb concentrations in the soil resulted in increased tolerance to Pb of the bacterial community, measured using both thymidine incorporation and plate counts. Furthermore, changes in tolerance were correlated to changes in the community structure. The bacterial community of the most contaminated soils showed higher specific activity (thymidine and leucine incorporation rates) and higher culturability than that of control soils. Fungal colony forming units (CFUs) were 10 times lower in the most Pb-enriched soils, the species composition was widely different from that in control soils, and the isolated fungi had high Pb tolerance. The most commonly isolated fungus in Pb-enriched soils was Tolypocladium inflatum. Comparison of isolates from Pb-enriched soil and isolates from unpolluted soils showed that T. inflatum was intrinsically Pb-tolerant, and that the prolonged conditions with high Pb had not selected for any increased tolerance.

Investigating the link between fish community structure and environmental state in deep-time

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Sibert, E. C.

2017-12-01

In the modern ocean, a bottom-up ecological viewpoint posits that the composition of plankton communities is often a function of ambient oceanographic conditions, including nutrient concentrations and water temperature. Thus, certain plankton species or communities can be associated with specific oceanographic conditions, giving them potential as carriers of paleoceanographic information. Furthermore, consumer groups, such as fish, depend on the structure and composition of these plankton, and therefore different plankton communities will support different types of fish. In addition, fish have their own physiological constraints for surviving in particular environments, such as oxygen demand, and metabolic rate, causing certain clades to be selectively associated with different water mass characteristics. Thus, the relative or absolute abundances of different fish species or groups could shed light on shifting oxygen concentrations, temperature, or primary productivity in the past. To assess whether fish communities have sufficient environmental control to provide paleoceanographic insights, I use a variety of morphological, phylogenetic, and ecological statistical approaches, to correlate modern fish communities from around the world with environmental variables. I then apply these principles to a series of ichthyolith assemblages from the Cretaceous and Cenozoic, across both space and time, to assess whether fish community composition, abundance, or other characteristics can be predictive of ocean temperature or export productivity. I find that while the abundance of fish fossils in deep-sea cores is often, though not always, correlated with certain export production and temperature proxies, community composition appears to vary independently of these variables on long timescales, driven more by evolutionary processes. However, there are distinct differences in contemporary communities in different locations, suggesting that there is potential in using fish

Individual and community level risk-factors for alcohol use disorder among conflict-affected persons in Georgia.

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Roberts, Bayard; Murphy, Adrianna; Chikovani, Ivdity; Makhashvili, Nino; Patel, Vikram; McKee, Martin

2014-01-01

The evidence on alcohol use disorder among conflict-affected civilian populations remains extremely weak, despite a number of potential risk-factors. The aim of this study is to examine patterns of alcohol use disorder among conflict-affected persons in the Republic of Georgia. A cross-sectional survey of 3600 randomly selected internally displaced persons (IDPs) and former IDPs. Two alcohol use disorder outcomes were measured: (i) having at least hazardous alcohol use (AUDIT score ≥ 8); (ii) episodic heavy drinking (consuming >60 grams of pure alcohol per drinking session at least once a week). Individual level demographic and socio-economic characteristics were also recorded, including mental disorders. Community level alcohol environment characteristics relating to alcohol availability, marketing and pricing were recorded in the respondents' communities and a factor analysis conducted to produce a summary alcohol environment factor score. Logistic regression analyses examined associations between individual and community level factors with the alcohol use disorder outcomes (among men only). Of the total sample, 71% of men and 16% of women were current drinkers. Of the current drinkers (N = 1386), 28% of men and 1% of women were classified as having at least hazardous alcohol use; and 12% of men and 2% of women as episodic heavy drinkers. Individual characteristics significantly associated with both outcomes were age and experiencing a serious injury, while cumulative trauma events and depression were also associated with having at least hazardous alcohol use. For the community level analysis, a one unit increase in the alcohol environment factor was associated with a 1.27 fold increase in episodic heavy drinking among men (no significant association with hazardous alcohol use). The findings suggest potential synergies for treatment responses for alcohol use disorder and depression among conflict-affected populations in Georgia, as well as the need for stronger