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Sample records for macrophyte community structure

  1. Invertebrate grazing during the regenerative phase affects the ultimate structure of macrophyte communities

    NARCIS (Netherlands)

    Elger, A.F.; Willby, N.; Cabello-Martinez, M.

    2009-01-01

    1. Although the biomass of freshwater macrophytes consumed by invertebrate herbivores (excluding crayfish) is usually low, there is growing evidence that invertebrates do exert a structuring effect on macrophyte communities. To explain this, we postulated that the effect of invertebrates may be conc

  2. Responses of bacterial community structure and denitrifying bacteria in biofilm to submerged macrophytes and nitrate

    Science.gov (United States)

    Zhang, Songhe; Pang, Si; Wang, Peifang; Wang, Chao; Guo, Chuan; Addo, Felix Gyawu; Li, Yi

    2016-10-01

    Submerged macrophytes play important roles in constructed wetlands and natural water bodies, as these organisms remove nutrients and provide large surfaces for biofilms, which are beneficial for nitrogen removal, particularly from submerged macrophyte-dominated water columns. However, information on the responses of biofilms to submerged macrophytes and nitrogen molecules is limited. In the present study, bacterial community structure and denitrifiers were investigated in biofilms on the leaves of four submerged macrophytes and artificial plants exposed to two nitrate concentrations. The biofilm cells were evenly distributed on artificial plants but appeared in microcolonies on the surfaces of submerged macrophytes. Proteobacteria was the most abundant phylum in all samples, accounting for 27.3-64.8% of the high-quality bacterial reads, followed by Chloroflexi (3.7-25.4%), Firmicutes (3.0-20.1%), Acidobacteria (2.7-15.7%), Actinobacteria (2.2-8.7%), Bacteroidetes (0.5-9.7%), and Verrucomicrobia (2.4-5.2%). Cluster analysis showed that bacterial community structure can be significantly different on macrophytes versus from those on artificial plants. Redundancy analysis showed that electrical conductivity and nitrate concentration were positively correlated with Shannon index and operational taxonomic unit (OTU) richness (log10 transformed) but somewhat negatively correlated with microbial density. The relative abundances of five denitrifying genes were positively correlated with nitrate concentration and electrical conductivity but negatively correlated with dissolved oxygen.

  3. Production in aquatic macrophyte communities

    DEFF Research Database (Denmark)

    Binzer, Thomas; Sand-Jensen, Kaj

    2002-01-01

    -dimensional structure because of the strong drag and shear forces of moving water. This difference in canopy structure has been suggested to account for the three- to fivefold higher gross production rates in terrestrial than aquatic communities. To evaluate the effect of community structure in aquatic habitats, we...... to distribute photons evenly between the photosynthetic tissues. As scattering and attenuation in the water column increase, the effect of thallus structure on production declines and thin transparent macrophytes are more efficient at utilizing light than thick opaque macrophytes. The results confirm...... combined a simple mechanistic model and empirical measurements on artificially structured macroalgal communities (Ulva lactuca) with varying thallus absorptance and community density. Predicted and measured values corresponded closely and revealed that gross production in high-light environments...

  4. Production in aquatic macrophyte communities

    DEFF Research Database (Denmark)

    Binzer, Thomas; Sand-Jensen, Kaj

    2002-01-01

    Many terrestrial plant canopies regulate spatial patterns in leaf density and leaf inclination to distribute light evenly between the photosynthetic tissue and to optimize light utilization efficiency. Sessile aquatic macrophytes, however, cannot maintain the same well-defined three......-dimensional structure because of the strong drag and shear forces of moving water. This difference in canopy structure has been suggested to account for the three- to fivefold higher gross production rates in terrestrial than aquatic communities. To evaluate the effect of community structure in aquatic habitats, we...... was markedly enhanced by a vertical orientation of thalli when absorptance and community density were both high. This result implies that aquatic macrophytes of high thallus absorptance and community density exposed to high light are limited in attaining high gross production rates because of their inability...

  5. Macrophyte presence and growth form influence macroinvertebrate community structure

    NARCIS (Netherlands)

    Walker, P.D.; Wijnhoven, S.; van der Velde, G.

    2013-01-01

    Multivariate analysis demonstrated that macroinvertebrate assemblages of macrophyte-dominated sub-habitats within a small eutrophic pond differed markedly from those of Bottom substrate and Open water habitats. Certain habitats (e.g. Nymphaea and Phragmites) appeared to be quite similar in their

  6. Community photosynthesis of aquatic macrophytes

    DEFF Research Database (Denmark)

    Binzer, T.; Sand-Jensen, K.; Middelboe, A. L.

    2006-01-01

    We compared 190 photosynthesis-irradiance (P-E) experiments with single- and multispecies communities of macroalgae and vascular plants from freshwater and marine habitats. We found a typical hyperbolic P-E relation in all communities and no sign of photosaturation or photoinhibition of photosynt......We compared 190 photosynthesis-irradiance (P-E) experiments with single- and multispecies communities of macroalgae and vascular plants from freshwater and marine habitats. We found a typical hyperbolic P-E relation in all communities and no sign of photosaturation or photoinhibition...... of photosynthesis at the highest irradiances of about 2,000 mmol m22 s21. Macrophyte communities displayed much higher maximum gross production (GPmax), respiration, and light compensation point than separate phytoelements because of the multilayered structure and extensive self-shading in the communities, whereas...

  7. Community photosynthesis of aquatic macrophytes

    DEFF Research Database (Denmark)

    Binzer, T.; Sand-Jensen, K.; Middelboe, A. L.

    2006-01-01

    We compared 190 photosynthesis-irradiance (P-E) experiments with single- and multispecies communities of macroalgae and vascular plants from freshwater and marine habitats. We found a typical hyperbolic P-E relation in all communities and no sign of photosaturation or photoinhibition of photosynt......We compared 190 photosynthesis-irradiance (P-E) experiments with single- and multispecies communities of macroalgae and vascular plants from freshwater and marine habitats. We found a typical hyperbolic P-E relation in all communities and no sign of photosaturation or photoinhibition...... of photosynthesis at the highest irradiances of about 2,000 mmol m22 s21. Macrophyte communities displayed much higher maximum gross production (GPmax), respiration, and light compensation point than separate phytoelements because of the multilayered structure and extensive self-shading in the communities, whereas...

  8. The role of pH in structuring communities of Maine wetland macrophytes and chironomid larvae (Diptera)

    Science.gov (United States)

    Woodcock, T.S.; Longcore, J.R.; McAuley, D.G.; Mingo, T.M.; Bennatti, C.R.; Stromborg, K.L.

    2005-01-01

    Aquatic vascular plants, or macrophytes, are an important habitat component for many wetland organisms, and larvae of chironomid midges are ubiquitous components of wetland fauna. Many chironomids are primary consumers of algae and detritus and form an essential energetic link between allochthonous and autochthonous primary production and higher trophic levels, while others are predators and feed on smaller invertebrates. Live macrophytes serve mostly as habitat, whereas plant detritus serves as both habitat and as a food source. Assemblages of macrophytes and chironomid larvae were surveyed in ten Maine wetlands, five with low pH (5.5), and explained in terms of physical and chemical habitat variables. Macrophyte richness was significantly greater, and richness of chironomid larvae was lower, in low pH wetlands. There was no difference in chironomid abundance related to pH. However, community structure was related to pH, suggesting that competitive dominance of a few taxa was responsible for lower richness in low pH wetlands, whereas competition was weaker in high pH wetlands, making coexistence of more chironomid taxa possible. An examination of individual chironomid taxa by stepwise multiple regression showed that distribution of most taxa was controlled by water chemistry variables and macrophyte habit (i.e., floating, submergent).

  9. Predicting Changes in Macrophyte Community Structure from Functional Traits in a Freshwater Lake: A Test of Maximum Entropy Model.

    Science.gov (United States)

    Fu, Hui; Zhong, Jiayou; Yuan, Guixiang; Guo, Chunjing; Lou, Qian; Zhang, Wei; Xu, Jun; Ni, Leyi; Xie, Ping; Cao, Te

    2015-01-01

    Trait-based approaches have been widely applied to investigate how community dynamics respond to environmental gradients. In this study, we applied a series of maximum entropy (maxent) models incorporating functional traits to unravel the processes governing macrophyte community structure along water depth gradient in a freshwater lake. We sampled 42 plots and 1513 individual plants, and measured 16 functional traits and abundance of 17 macrophyte species. Study results showed that maxent model can be highly robust (99.8%) in predicting the species relative abundance of macrophytes with observed community-weighted mean (CWM) traits as the constraints, while relative low (about 30%) with CWM traits fitted from water depth gradient as the constraints. The measured traits showed notably distinct importance in predicting species abundances, with lowest for perennial growth form and highest for leaf dry mass content. For tuber and leaf nitrogen content, there were significant shifts in their effects on species relative abundance from positive in shallow water to negative in deep water. This result suggests that macrophyte species with tuber organ and greater leaf nitrogen content would become more abundant in shallow water, but would become less abundant in deep water. Our study highlights how functional traits distributed across gradients provide a robust path towards predictive community ecology.

  10. 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.

  11. Comparison of the community structures of ammonia-oxidizing bacteria and archaea in rhizoplanes of floating aquatic macrophytes.

    Science.gov (United States)

    Wei, Bo; Yu, Xin; Zhang, Shuting; Gu, Li

    2011-09-20

    Some common floating aquatic macrophytes could remove nutrients, such as nitrogen, from eutrophic water. However, the relationship between these macrophytes and the ammonia-oxidizing microorganisms on their rhizoplanes is still unknown. In this study, we examined communities of ammonia-oxidizing archaea (AOA) and bacteria (AOB) on the rhizoplanes of common floating aquatic macrophytes (Eichhornia crassipes, Pistia stratiotes and Ipomoea aquatic) in a eutrophic reservoir.The results show that AOB were the predominant ammonia-oxidizer on the three rhizoplanes. The principal AOB were Nitrosomonas europaea and Nitrosomonas ureae clades. The principal group of AOA was most similar to the clone from activated sludge. The ratio of AOB amoA gene copies to AOA varied from 1.36 (on E. crassipes) to 41.90 (on P. stratiotes). Diversity of AOA was much lower than that of AOB in most samples, with the exception of P. stratiotes.

  12. Do freshwater macrophytes influence the community structure of ammonia-oxidizing and denitrifying bacteria in the rhizospere?

    DEFF Research Database (Denmark)

    Herrmann, Martina; Schramm, Andreas

    2006-01-01

    dortmanna have been shown to release oxygen from their roots and to stimulate nitrification and coupled nitrification-denitrification in the rhizosphere. Together with the excretion of root exudates, this effect leads to strongly modified microenvironments at the root surface and in the rhizosphere compared......, activity and composition of these microbial communities between root surface (rhizoplane), rhizosphere and unvegetated sediment. Comparative investigations are carried out focussing on the macrophyte species Littorella uniflora, Juncus bulbosus and Myriophyllum spicatum. Microsensor measurements confirmed...... the photosynthesis-dependant, species-specific release of oxygen into the rhizosphere; batch incubations indicated a higher nitrification potential in the rhizosphere of Littorella uniflora compared to unvegetated sediment, and will be complemented with the determination of rates of coupled nitrification-denitrification...

  13. 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.

  14. Retrospective assessment of macrophytic communities in southern Lake Garda (Italy from in situ and MIVIS (Multispectral Infrared and Visible Imaging Spectrometer data

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    Claudia Giardino

    2012-01-01

    Full Text Available In situ and hyperspectral MIVIS (Multispectral Infrared and Visible Imaging Spectrometer images acquired over a period of 13 years are used to assess changes in macrophyte colonization patterns in the coastal zones of the Sirmione Peninsula in the southern part of Lake Garda (Italy. In situ data (abundance, cover density and diversity of macrophyte communities and MIVIS-derived maps of colonized substrates are analyzed by considering the variability of the main hydrological and physicochemical variables in order to indicate the main factors that explain the spatiotemporal variability of macrophyte communities. The results show a considerable modification in terms of macrophyte structural complexity and colonized areas. Almost 98% of macrophyte meadows (in particular communities with a density of over 70% are lost and subsequently replaced by moderate to extremely rare communities with density from 10% to 40%. Well-established submerged macrophytes are replaced by de-structured communities characterized by moderate to scarce density: on average lower than 30%. The study indicates that macrophyte distribution along the littoral zone of the Sirmione Peninsula is certainly linked to water transparency and water level fluctuation. The results also indicate that the worsening of eutrophication may be associated with the gradual disappearance of macrophyte meadows, but may also be accelerated by herbivorous aquatic birds grazing there. Lastly, the increasing frequency and number of catamaran tours could be considered a threat for the stability of these valuable communities.

  15. Aquatic macrophyte community varies in urban reservoirs with different degrees of eutrophication

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    Suelen Cristina Alves da Silva

    2014-06-01

    Full Text Available AIM: Investigate spatial and temporal variation in the aquatic macrophyte community in four urban reservoirs located in Curitiba metropolitan region, Brazil. We tested the hypothesis that aquatic macrophyte community differ among reservoirs with different degrees of eutrophication. METHODS: The reservoirs selected ranged from oligotrophic/mesotrophic to eutrophic. Sampling occurred in October 2011, January 2012 and June 2012. Twelve aquatic macrophytes stands were sampled at each reservoir. Species were identified and the relative abundance of aquatic macrophytes was estimated. Differences among reservoirs and over sampling periods were analyzed: i through two‑way ANOVAs considering the stand extent (m and the stand biodiversity - species richness, evenness, Shannon-Wiener index and beta diversity (species variation along the aquatic macrophyte stand; and ii through PERMANOVA considering species composition. Indicator species that were characteristic for each reservoir were also identified. RESULTS: The aquatic macrophyte stand extent varied among reservoirs and over sampling periods. Species richness showed only temporal variation. On the other hand, evenness and Shannon-Wiener index varied only among reservoirs. The beta diversity of macrophyte stands did not vary among reservoirs or over time, meaning that species variability among aquatic macrophyte stands was independent of the stand extent and reservoir eutrophication. Community composition depended on the reservoir and sampling period. CONCLUSIONS: Our results support our initial expectation that reservoirs of different degrees of eutrophication have different aquatic macrophyte communities. As a consequence, each reservoir had particular indicator species. Therefore, monitoring and management efforts must be offered for each reservoir individually.

  16. Functional diversity of macrophyte communities within and between Pyrenean lakes

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    Enric BALLESTEROS

    2009-02-01

    Full Text Available Submersed vegetation is a common feature in about 70% Pyrenean high mountain (>1500 m a.s.l. lakes. Isoetids and soft-water elodeids are common elements of this underwater flora and can form distinct vegetation units (i.e. patches of vegetation dominated by different species within complex mosaics of vegetation in shallow waters (<7 m. Since isoetids exert a strong influence on sediment biogeochemistry due to high radial oxygen loss, we examined the small scale characteristics of the lake environment (water and sediment associated to vegetation patches in order to ascertain potential functional differences among them. To do so, we characterised the species composition and biomass of the main vegetation units from 11 lakes, defined plant communities based on biomass data, and then related each community with sediment properties (redox and dissolved nutrient concentration in the pore water and water nutrient concentration within plant canopy. We also characterised lake water and sediment in areas without vegetation as a reference. A total of twenty-one vegetation units were identified, ranging from one to five per lake. A cluster analysis on biomass species composition suggested seven different macrophyte communities that were named after the most dominant species: Nitella sp., Potamogeton praelongus, Myriophyllum alterniflorum, Sparganium angustifolium, Isoetes echinospora, Isoetes lacustris and Carex rostrata. Coupling between macrophyte communities and their immediate environment (overlying water and sediment was manifested mainly as variation in sediment redox conditions and the dominant form of inorganic nitrogen in pore-water. These effects depended on the specific composition of the community, and on the allocation between above- and belowground biomass, and could be predicted with a model relating the average and standard deviation of sediment redox potential from 0 down to -20 cm, across macrophyte communities. Differences in pore

  17. 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

    2014-01-01

    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. PMID:24811826

  18. Submerged macrophytes mitigate direct and indirect insecticide effects in freshwater communities.

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    William R Brogan

    Full Text Available Understanding how ecological interactions mitigate the impacts of perturbations such as pesticides in biological communities is an important basic and applied question for ecologists. In aquatic ecosystems, new evidence from microcosm experiments suggests that submerged macrophytes can buffer cladocerans from pulse exposures to the widely used insecticide malathion, and that mitigation increases with macrophyte density. However, whether these results scale up to more complex aquatic communities where ecological interactions such as competition can alter toxicity is unknown. Further, macrophyte abilities to mitigate different insecticide exposure scenarios (i.e. single versus repeated pulses have never been tested. To address these gaps, we performed a factorial mesocosm experiment examining the influence of four macrophyte treatments (0, 10, 50, or 100 Elodea Canadensis shoots planted per mesocosm crossed with three malathion exposure scenarios (no insecticide, single pulse, repeated pulses on aquatic communities containing zooplankton, phytoplankton, periphyton, two snail species, and larval amphibians. In the absence of macrophytes, single malathion pulses caused short-term declines in cladoceran abundance followed by their rapid recovery, which precluded any indirect effects (i.e. trophic cascades. However, repeated malathion pulses caused cladoceran extinctions, resulting in persistent phytoplankton blooms and reduced abundance of one snail species. In contrast, with macrophytes present, even at low density, malathion had no effect on any taxa. We also discovered novel effects of macrophytes on the benthic food web. In the two highest macrophyte treatments, we observed trends of reduced periphyton biomass, decreased abundance of one snail species, and decreased amphibian time to and mass at metamorphosis. To our knowledge, this is the first evidence of negative submerged macrophyte effects on amphibians, a taxa of global conservation concern

  19. Monitoring the dynamics of an invasive emergent macrophyte community using operational remote sensing data

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    Albright, T.P.; Ode, D.J.

    2011-01-01

    Potamogeton crispus L. (curly pondweed) is a cosmopolitan aquatic macrophyte considered invasive in North America and elsewhere. Its range is expanding and, on individual water bodies, its coverage can be dynamic both within and among years. In this study, we evaluate the use of free and low-cost satellite remote sensing data to monitor a problematic emergent macrophyte community dominated by P. crispus. Between 2000 and 2006, we acquired eight satellite images of 24,000-ha Lake Sharpe, South Dakota (USA). During one of the dates for which satellite imagery was acquired, we sampled the lake for P. crispus and other emergent macrophytes using GPS and photography for documentation. We used cluster analysis to assist in classification of the satellite imagery and independently validated results using the field data. Resulting estimates of emergent macrophyte coverage ranged from less than 20 ha in 2002 to 245 ha in 2004. Accuracy assessment indicated 82% of image pixels were correctly classified, with errors being primarily due to failure to identify emergent macrophytes. These results emphasize the dynamic nature of P. crispus-dominated macrophyte communities and show how they can be effectively monitored over large areas using low-cost remote sensing imagery. While results may vary in other systems depending on water quality and local flora, such an approach could be applied elsewhere and for a variety of macrophyte communities. ?? Springer Science+Business Media B.V. 2010.

  20. Biodiversity patterns of macrophyte and macroinvertebrate communities in two lagoons of Western Greece.

    Science.gov (United States)

    Fyttis, G.; Reizopoulou, S.; Papastergiadou, E.

    2012-04-01

    also showed that environmental variables such as depth, transparency/depth ratio, total P, chl-a, and TSM differed significantly between the two lagoons. In order to assess the ecological quality of the study sites, the functional ISD index has been applied. From the preliminary results it seems that ISD index, based on the biomass size structure of the macroinvertebrate communities, is more appropriate for the assessment of the ecological status for these particular ecosystems. The development of a monitoring team is essential for the protection and management of these ecologically important ecosystems. Further investigation is necessary to examine the relationships between benthic macroinvertebrates and aquatic macrophytes, the use of biotic indices to the evaluation for lagoonal ecosystems' ecological status and the relation between the hydrological processes and the biodiversity patterns of the biotic elements.

  1. Phyllosphere bacterial community of floating macrophytes in paddy soil environments as revealed by illumina high-throughput sequencing.

    Science.gov (United States)

    Xie, Wan-Ying; Su, Jian-Qiang; Zhu, Yong-Guan

    2015-01-01

    The phyllosphere of floating macrophytes in paddy soil ecosystems, a unique habitat, may support large microbial communities but remains largely unknown. We took Wolffia australiana as a representative floating plant and investigated its phyllosphere bacterial community and the underlying driving forces of community modulation in paddy soil ecosystems using Illumina HiSeq 2000 platform-based 16S rRNA gene sequence analysis. The results showed that the phyllosphere of W. australiana harbored considerably rich communities of bacteria, with Proteobacteria and Bacteroidetes as the predominant phyla. The core microbiome in the phyllosphere contained genera such as Acidovorax, Asticcacaulis, Methylibium, and Methylophilus. Complexity of the phyllosphere bacterial communities in terms of class number and α-diversity was reduced compared to those in corresponding water and soil. Furthermore, the bacterial communities exhibited structures significantly different from those in water and soil. These findings and the following redundancy analysis (RDA) suggest that species sorting played an important role in the recruitment of bacterial species in the phyllosphere. The compositional structures of the phyllosphere bacterial communities were modulated predominantly by water physicochemical properties, while the initial soil bacterial communities had limited impact. Taken together, the findings from this study reveal the diversity and uniqueness of the phyllosphere bacterial communities associated with the floating macrophytes in paddy soil environments.

  2. Effect of Hydrologic Alteration on the Community Succession of Macrophytes at Xiangyang Site, Hanjiang River, China

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    Na Yang

    2017-01-01

    Full Text Available With the intensification of human activities over the past three decades in China, adverse effects on river ecosystem become more serious especially in the Hanjiang River. Xiangyang site is an important spawn ground for four domestic fishes in the downstream region of Hanjiang River. Based on the field survey results of macrophytes during 1997–2000 and 2013-2014, community succession of aquatic macrophytes at Xiangyang site was evaluated and discussed. Two-key ecologic-related hydrologic characteristics, flow regime and water level, were identified as the main influence factors. The EFC (environmental flow components parameters were adopted to evaluate the alteration of flow regimes at Xiangyang site during 1941–2013. Evaluation results demonstrate a highly altered flow process after being regulated by reservoir. The flow patterns tend to be an attenuation process with no large floods occurring but a higher monthly low flow. Furthermore, the water level decreased and fluctuation reduced after the dam was built, which caused the decrease of biomass but favored the submerged macrophytes during 1995–2009. However, with the water level increasing after 2010 and gently fluctuating, due to uplift by the hydraulic projects downstream as well as the flow attenuation, the dominant position of submerged macrophytes will be weakened.

  3. Effect of Hydrologic Alteration on the Community Succession of Macrophytes at Xiangyang Site, Hanjiang River, China

    Science.gov (United States)

    Duan, Kai

    2017-01-01

    With the intensification of human activities over the past three decades in China, adverse effects on river ecosystem become more serious especially in the Hanjiang River. Xiangyang site is an important spawn ground for four domestic fishes in the downstream region of Hanjiang River. Based on the field survey results of macrophytes during 1997–2000 and 2013-2014, community succession of aquatic macrophytes at Xiangyang site was evaluated and discussed. Two-key ecologic-related hydrologic characteristics, flow regime and water level, were identified as the main influence factors. The EFC (environmental flow components) parameters were adopted to evaluate the alteration of flow regimes at Xiangyang site during 1941–2013. Evaluation results demonstrate a highly altered flow process after being regulated by reservoir. The flow patterns tend to be an attenuation process with no large floods occurring but a higher monthly low flow. Furthermore, the water level decreased and fluctuation reduced after the dam was built, which caused the decrease of biomass but favored the submerged macrophytes during 1995–2009. However, with the water level increasing after 2010 and gently fluctuating, due to uplift by the hydraulic projects downstream as well as the flow attenuation, the dominant position of submerged macrophytes will be weakened. PMID:28127493

  4. Microbial communities in marine sediments modify success of an invasive macrophyte.

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    Gribben, Paul E; Nielsen, Shaun; Seymour, Justin R; Bradley, Daniel J; West, Matthew N; Thomas, Torsten

    2017-08-29

    Invasive plants have extensive impacts on ecosystem function and biodiversity globally. Our inability to manage invasive species stems in part from a lack of understanding of the processes that control their successful establishment and spread. To date, studies have largely considered how above-ground processes control native/invasive plant interactions. Emerging research from terrestrial and wetland ecosystems demonstrates that below-ground processes under microbial control can determine the outcome of interactions between native and invasive plants. Whether sediment microbes modify the success of invasive macrophytes in marine ecosystems is untested, despite marine sediment microbes controlling many ecological processes (e.g. nutrient cycling) comparable to those in terrestrial ecosystems. We first show that sediment bacterial communities differ between the native seagrass Zostera capricorni and the invasive alga Caulerpa taxifolia and that those differences relate to functional changes in sulfur cycling between the macrophytes. Second, by experimentally manipulating the microbial communities we show that intact microbial communities in Z. capricorni sediments provide biotic resistance by reducing C. taxifolia fragment growth 119% compared to when they are inactive, and intact microbial communities in C. taxifolia sediments have positive feedbacks by increasing fragment growth 200%. Thus, similar to terrestrial ecosystems, microorganisms appear to indirectly control the success of invasive macrophytes in marine ecosystems.

  5. Epiphytic bacterial communities on two common submerged macrophytes in Taihu Lake: diversity and host-specificity

    Institute of Scientific and Technical Information of China (English)

    HE Dan; REN Lijuan; WU Qinglong

    2012-01-01

    Leaves of terrestrial and aquatic plants are home to a wide diversity of bacterial species.However,the diversity and variability of epiphytic bacteria on their submerged plant hosts remains poorly understood.We investigated the diversity and composition of epiphytic bacteria from two common submerged macrophytes:Vallisneria natans and Hydrilla verticillata in Taihu Lake,Jiangsu,China,using methods of terminal restriction fragment length polymorphisms (T-RFLP) and clone library analyses targeted at bacterial 16S rRNA genes.The results show that:(1) the libraries of the two waterweeds contain wide phylogenetic distribution of bacteria,and that the sequences of the two libraries can be separated into 93 OTUs (at 97% similar value); (2) Betaproteobacteria,including Burkholderiales,was the most abundant bacterial group on both plants.Cyanobacteria and Gammaproteobacteria were the second largest groups on V.natans and H.verticillata,respectively.Both clone libraries included some sequences related to those of methanotrophs and nitrogen-fixing bacteria; (3) Cluster analysis of the T-RFLP profiles showed two distinct clusters corresponding to the two plant populations.Both ANOSIM of the T-RFLPdata and Libshuff analysis of the two clone libraries indicated a significant difference in epiphytic bacterial communities between the two plants.Therefore,the epiphytic bacterial communities on submerged macrophytes appear to be diverse and host-specific,which may aid in understanding the ecological functions of submerged macrophytes in general.

  6. Investigation of Darwin’s naturalization hypothesis in invaded macrophyte communities

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    Although native macrophytes are beneficial in aquatic ecosystems, invasive macrophytes can cause significant ecological and economic harm. Numerous studies have attributed invasiveness to species’ characteristics, whereas others attribute invasion to biotic and abiotic characteristics of the invaded...

  7. Water quality and communities associated with macrophytes in a shallow water-supply reservoir on an aquaculture farm.

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    Sipaúba-Tavares, L H; Dias, S G

    2014-05-01

    Plankton communities and macrofauna associated to aquatic macrophyte stands in a shallow water-supply reservoir (21°14'09″S; 48°18'38″W) on an aquaculture farm were compared to evaluate the relationship between organism densities and some abiotic features of the reservoir. Water and communities associated were sampled at two sites, one in an area with the predominance of Eichhornia azurea (Sw.) Kunth and the other with the predominance of Salvinia auriculata Aublet. Communities associated with macrophytes were sampled with floating quadrants (0.5 m2); the macrophytes were washed and plankton and macrofauna were fixated with 4% formalin and 1% lugol iodine; the specimens were then identified and counted. Plankton and macrofauna communities associated with S. auriculata and E. azurea had a similar diversity of species but different (pmacrophytes presence in the shallow reservoir is a strong predictor of favourable conditions to maintain great diversity plankton community and macrofauna associated with plants. The role of macrophytes is important for not only stabilising the clear-water state and maintaining high diversity of organisms associated, but also it seems to be a good alternative to maintaining desirable water-supply quality for aquaculture farms.

  8. Water quality and communities associated with macrophytes in a shallow water-supply reservoir on an aquaculture farm

    Directory of Open Access Journals (Sweden)

    LH. Sipaúba-Tavares

    Full Text Available Plankton communities and macrofauna associated to aquatic macrophyte stands in a shallow water-supply reservoir (21°14′09″S; 48°18′38″W on an aquaculture farm were compared to evaluate the relationship between organism densities and some abiotic features of the reservoir. Water and communities associated were sampled at two sites, one in an area with the predominance of Eichhornia azurea (Sw. Kunth and the other with the predominance of Salvinia auriculata Aublet. Communities associated with macrophytes were sampled with floating quadrants (0.5 m2; the macrophytes were washed and plankton and macrofauna were fixated with 4% formalin and 1% lugol iodine; the specimens were then identified and counted. Plankton and macrofauna communities associated with S. auriculata and E. azurea had a similar diversity of species but different (p<0.05 in the abundance of associated organisms. Eichhornia azurea had the highest contents in dry and wet weight, total phosphorus, total nitrogen and organic matter. Planktonic algae were directly correlated with biomass of E. azurea. The taxa with highest densities were Rotifera and Zygnematophyceae. Results showed that the environmental variables associated with macrophytes presence in the shallow reservoir is a strong predictor of favourable conditions to maintain great diversity plankton community and macrofauna associated with plants. The role of macrophytes is important for not only stabilising the clear-water state and maintaining high diversity of organisms associated, but also it seems to be a good alternative to maintaining desirable water-supply quality for aquaculture farms.

  9. Submerged macrophyte communities in the Forsmark area. Building of a GIS application as a tool for biomass estimations

    Energy Technology Data Exchange (ETDEWEB)

    Fredriksson, Ronny [Univ. of Kalmar (Sweden)

    2005-12-15

    The aim of this study was to compile the information from previous studies to produce a GIS application that both illustrates the distribution of different vegetation communities and also makes it possible to estimate the total biomass of the different vegetation communities and its associated fauna. The GIS application was created by means of the software Arc View 3.3 by Environmental Systems Research Institute, Inc. Distribution readings and quantitative data of submerged macrophyte communities and its associated fauna was obtained from studies by Kautsky et al. and by Borgiel. Information about the macrophyte distribution in Laangoersviken, located in the northern parts of Kallrigafjaerden, was obtained from a report by Upplandsstiftelsen. Information about water depth and bottom substrate was available as USGS DEM file, produced by Geological Survey of Sweden. Complementary data of the covering degree of submerged vegetation was obtained from a study using an under water video camera by Tobiasson. Quantitative data on macrophyte and faunal biomass were either obtained from the primary SKB data base SICADA or directly from reports. Samples were compiled and analysed according to dominating vegetation. The work was carried out as follows: Where information about the bottom substrate was available polygons were created by means of the substrate shape file and depth grid from Geological Survey of Sweden. The vegetation community and the covering degree on a certain depth and substrate combination were determined by compiled information from studies by Kautsky and by Borgiel. All observations from a certain bottom substrate were analysed to find the dominating vegetation within different depth ranges. After determining the dominating vegetation, the covering degrees of different macrophyte classes within each depth range were calculated as a mean of all readings. Areas without information about the bottom substrate, but still adjacent to areas included in the

  10. Assessment of periphyton, aquatic macrophytes, benthic communities, and physical habitat in midwestern United States streams coinciding with varying historical concentrations of atrazine.

    Science.gov (United States)

    Hall, Lenwood W; Anderson, Ronald D; Killen, William D; Hosmer, Alan J; Brain, Richard A

    2014-01-01

    The objectives of this pilot study were to: (1) characterize periphyton and benthic communities using standard collection methods in six Midwest watersheds with varying historical levels of atrazine (low range, medium range and upper range); (2) qualitatively assess presence of aquatic vascular plants at each site; (3) assess and compare physical habitat at each study site in order to evaluate how physical habitat structure may influence the biological communities and (4) analyze the periphyton and benthic macroinvertebrate community data (i.e., series of metrics) among sites to evaluate possible differences or similarities among sites with different historical atrazine exposures. Five of the eight physical habitat metrics (including total physical habitat score) were different among the six study sites. There appeared to be no substantial difference in the structure of periphtyon communities at the six Midwest sites based on 9 of 12 metrics. For the three metrics that showed differences among sites-percentage of sensitive diatoms, percent Achnanches minutissima and percent motile diatoms - there was no consistent pattern with previous degrees of atrazine exposure and the scoring of these metrics. There were also no statistical differences in aquatic macrophyte spatial coverage among the six study areas. Thus, based on the spatially and temporally limited periphyton and aquatic macrophyte data, varying historical atrazine exposure was not associated with impact on resident plant communities (the target receptor group for atrazine). All 10 benthic community metrics showed significant differences among the six Midwest sites. Although no consistent pattern existed with varying historic levels of atrazine, benthic communities at one site with lower historical levels of atrazine were of higher quality than the other five sites. However, this one site also had a higher quality habitat compared to the other sites which was most likely the reason for this benthic condition.

  11. Submersed macrophyte communities before and after an episodic ice jam in the St. Clair and Detroit rivers

    Science.gov (United States)

    Nichols, S. Jerrine; Schloesser, Donald W.; Hudson, Patrick L.

    1989-01-01

    We conducted surveys in 1983 and 1984 of submersed macrophyte communities off six islands in the St. Clair and Detroit rivers using low altitude aerial photography and ground-truth collections. Sample collections in 1984 followed one of the coldest winters on record, during which ice up to 4 m thick developed in areas that were normally ice-free. Growth of many of the 20 taxa collected was delayed in the spring of 1984, as compared with the spring of 1983. By September 1984, however, total abundance of all taxa was equal to or greater than that in 1983. The location, size, and shape of plant beds in September 1984 were similar to those in 1983. We concluded that the unusual ice jam in early spring of 1984 had little, if any, permanent effect on submersed macrophytes in the St. Clair and Detroit rivers.

  12. Structure of the littoral fish assemblage in an impounded tributary: the effects of macrophytes presence (subtropical region, Brazil).

    Science.gov (United States)

    Hermes-Silva, S; Zaniboni-Filho, E

    2012-08-01

    To evaluate the effects of macrophytes presence in the structure of littoral fish assemblages in the littoral zone, monthly samples were collected from September, 2006 to August, 2007 in an impounded tributary of the Itá Reservoir, the Fragosos River, located in the Upper Uruguay River Basin. Fish were collected using a beach seine and sampling was conducted in the littoral zone inside a macrophyte stand and in an area with no macrophytes. A total of 5,191 fish were captured during the study period. Fish assemblage attributes (fish abundance, species richness, and diversity) varied significantly between sampling months and areas. The abundance of Astyanax cf. bimaculatus, Astyanax fasciatus, Geophagus brasiliensis, and Gymnotus carapo also varied significantly between sampling months and areas. Detrended Correspondence Analysis showed a clear spatial segregation at the first axis and a slight temporal segregation at the second axis. These results were confirmed by Multiple Response Permutation Procedure analysis. Apparently, the presence of the aquatic macrophytes is not the only factor influencing the distribution of littoral fish assemblages in the Fragosos River. Littoral fish seem to be taking advantage of low- to medium-sized macrophyte stands, but few species used maximum-sized stands.

  13. Impact of submerged macrophytes including charophytes on phyto- and zooplankton communities: allelopathy versus other mechanisms

    NARCIS (Netherlands)

    Van Donk, E.; Van de Bund, W.J.

    2002-01-01

    Submerged macrophytes are crucial for the stabilization of the clear water state in shallow, mesotrophic and eutrophic lakes. Especially, charophytes often play an important role because they are typically rapid colonizers and because charophyte meadows are believed to have a particularly strong pos

  14. Archaea Dominate the Ammonia-Oxidizing Community in the Rhizosphere of the Freshwater Macrophyte Littorella uniflora

    DEFF Research Database (Denmark)

    Herrmann, Martina; Saunders, Aaron M.; Schramm, Andreas

    2008-01-01

    Archaeal and bacterial ammonia monooxygenase genes (amoA) had similar low relative abundances in freshwater sediment. In the rhizosphere of the submersed macrophyte Littorella uniflora, archaeal amoA was 500- to >8,000-fold enriched compared to bacterial amoA, suggesting that the enhanced nitrifi...... nitrification activity observed in the rhizosphere was due to ammonia-oxidizing Archaea....

  15. Impact of submerged macrophytes including charophytes on phyto- and zooplankton communities: allelopathy versus other mechanisms

    NARCIS (Netherlands)

    Van Donk, E.; Van de Bund, W.J.

    2002-01-01

    Submerged macrophytes are crucial for the stabilization of the clear water state in shallow, mesotrophic and eutrophic lakes. Especially, charophytes often play an important role because they are typically rapid colonizers and because charophyte meadows are believed to have a particularly strong

  16. Advances in ecological research on epiphytic community of submerged macrophytes%沉水植物附植生物群落生态学研究进展

    Institute of Scientific and Technical Information of China (English)

    纪海婷; 谢冬; 周恒杰; 冷欣; 郭璇; 安树青

    2013-01-01

    在高等水生植物表面经常附着生长着藻类、真菌和细菌等,这些有机群体组成附植生物群落,在大中型浅水湖泊中普遍存在.附植生物群落具有特定的物种组成和空间结构,并随季节推移和沉水植物生长表现出一定的动态变化特征.附植生物群落与宿主植物及周围水体环境联系密切,不仅能够表征水体营养盐、光照、温度等环境因子特征,与沉水植物、食草动物、浮游植物等水生生物类群也存在不同的相互作用.水生生态系统中,附植生物群落参与水体营养物质转化,在草-藻型湖泊生态系统的相互转化过程中起重要作用;其较高的初级生产力作为水生动物重要的食物来源,增加了食物网的多样性;同时,附植生物群落因其独特的生理生态特征正逐渐被应用于水质净化和水环境质量监测.本文在综述近年来附植生物群落研究进展的基础上,分析了附植生物群落的组成结构和动态变化特征,阐述了附植生物群落在水生生态系统中的功能,可为湖泊富营养化治理,尤其是沉水植被的生态修复和管理提供科学依据.%Epiphytic community is a complex structure consisting of organisms such as algae, bacteria and fungi, and covers the surface of aquatic macrophytes in most shallow lakes. It has a unique composition and spatial structure, exhibiting significant dynamic characteristics in accordance with different seasons and the growth of submerged plants. Epiphytic community is closely related to the host plants and surrounding water environment, reflecting various habitat factors such as nutrient, light and temperature. It also has different interactions with submerged macrophytes, grazers, phytoplankton and other aquatic organisms. Epiphytic community participates in the material transformation of water ecological system, and plays a vital role in the shift between macrophyte-dominated and algal-dominated lake ecosystems

  17. Macroinvertebrate communities associated with macrophyte habitats in a tropical man-made lake (Lake Taabo, Côte d’Ivoire

    Directory of Open Access Journals (Sweden)

    Kouamé M. K.

    2011-02-01

    Full Text Available An ecological study was done on Lake Taabo with the main objective of characterising macroinvertebrate communities associated with the microhabitats created mainly by Eichhornia crassipes and other littoral native macrophytes. We sampled organisms in patches of those aquatic macrophytes. Also, some abiotic variables (temperature, transparency, turbidity, pH, TDS, conductivity, dissolved oxygen, NH$_{4}^{+}$+4, NO$_{3}^{-}$−3, NO$_{2}^{-}$−2, PO$_{4}^{3-}$3−4 and SiO$_{2}^{-}$−2 were measured. Overall, forty-three taxa of macroinvertebrates were identified. Ten of them were exclusively associated with water hyacinth while five were only associated with littoral macrophytes. Macroinvertebrate taxa with some of the highest family richness were Gastropoda, Coleoptera, Heteroptera, Odonata and Diptera. The taxon with highest density in both microhabitats was Chironomidae. Although higher values of taxonomic richness (Rs, the Shannon index (H′ and evenness (J were obtained with the water hyacinth habitat, significant differences between the two microhabitats were not observed. Canonical Correspondence Analysis revealed that samples of E. crassipes collected in the dry season were characterised by Gastropoda and Odonata, as well as higher values of transparency and ammonia-nitrogen. Baetidae, Hydrophilidae, Chironomidae, Ceratopogonidae, Coenagrionidae, Naucoridae and Ostracoda were most abundant in both E. crassipes and littoral macrophyte habitats during the rainy season. This season was characterised by higher levels of nitrates and conductivity.

  18. Emergent Macrophytes Support Zooplankton in a Shallow Tropical Lake: A Basis for Wetland Conservation.

    Science.gov (United States)

    Gebrehiwot, Mesfin; Kifle, Demeke; Triest, Ludwig

    2017-09-08

    Understanding the biodiversity value of littoral zones of lakes is a priority for aquatic biodiversity conservation. However, less emphasis has been given to the littoral part of tropical African lakes, with many of the previous researches focusing only on the open water side. The aim of the present study was, therefore, to investigate the impact of the littoral zone of a shallow freshwater tropical lake (Ziway, Ethiopia), dominated by two emergent macrophytes, on zooplankton community structure. We hypothesized that the wetland vegetation serves as a preferred microhabitat for zooplankton communities. A lake with substantial coverage of emergent macrophytes was monitored monthly from January to August, 2016. The monitoring included the measurements of physical, chemical, and biological parameters. Sampling sites were selected to represent areas of the macrophyte vegetation (Typha latifolia and Phragmites australis) and the open water part of the lake. Sites with macrophyte vegetation were found to be the home of more dense and diverse zooplankton community. However, during the period of high vegetation loss, the density of crustacean zooplankton showed significant reduction within the patches of macrophytes. From biodiversity conservation perspective, it was concluded that the preservation of such small areas of macrophytes covering the littoral zone of lakes could be as important as protecting the whole lake. However, the rapid degradation of wetland vegetation by human activities is a real threat to the lake ecosystem. In the not-too-far future, it could displace and evict riparian vegetation and the biota it supports.

  19. Biomass allocation to anchoring structures in the aquatic macrophytes from the subcontinental and Atlantic climates in Europe

    Directory of Open Access Journals (Sweden)

    Józef Szmeja

    2011-04-01

    Full Text Available Biomass allocation to anchoring structures in 10 species of aquatic macrophytes in two types of the cool and humid temperate climate in Europe, subcontionental (NW Poland and Atlantic (W France, was examined. The study focused on the weight of anchoring organs in Chara delicatula Ag., Ch. fragilis Desv., Juncus bulbosus L., Littorella uniflora (L. Asch., Luronium natans (L. Raf., Potamogeton pectinatus L., P. perfoliatus L., P. natans L. and Ranunculus fluitans (Lam. Wimm., as well as submerged structures in Hydrocharis morsus-ranae L. The plants were collected from 10 geographically distant lakes and 2 rivers with a current velocity of 0.3-0.5 m s-1. It was assumed that biomass allocation to anchoring structures in rooting macrophytes depends on the time that mechanical forces, which can remove the plants from the occupied area, exert their effect. It was found that, in the Atlantic and subcontinental climates, the ratio between the biomass of underground (or submerged and above-ground structures (U/A index, calculated for the ramets of Chara fragilis, Hydrocharis morsus-ranae and Ranunculus fluitans, has similar values (p>0.05. Nevertheless, among seven species of Cormophyta, which were anchored in the lake or pond littoral, six (Juncus bulbosus, Littorella uniflora, Luronium natans, Potamogeton pectinatus, P. perfoliatus and P. natans had higher values of the U/A index in the Atlantic climate than in the subcontinental type (p < 0.05. This can be explained by the lack of ice cover and, consequently, a longer time of wave action than in the subcontinental climate.

  20. Fungal endophytes of aquatic macrophytes: diverse host-generalists characterized by tissue preferences and geographic structure.

    Science.gov (United States)

    Sandberg, Dustin C; Battista, Lorna J; Arnold, A Elizabeth

    2014-05-01

    Most studies of endophytic symbionts have focused on terrestrial plants, neglecting the ecologically and economically important plants present in aquatic ecosystems. We evaluated the diversity, composition, host and tissue affiliations, and geographic structure of fungal endophytes associated with common aquatic plants in lentic waters in northern Arizona, USA. Endophytes were isolated in culture from roots and photosynthetic tissues during two growing seasons. A total of 226 isolates representing 60 putative species was recovered from 9,600 plant tissue segments. Although isolation frequency was low, endophytes were phylogenetically diverse and species-rich. Comparisons among the most thoroughly sampled species and reservoirs revealed that isolation frequency and diversity did not differ significantly between collection periods, among species, among reservoirs, or as a function of depth. However, community structure differed significantly among reservoirs and tissue types. Phylogenetic analyses of a focal genus (Penicillium) corroborated estimates of species boundaries and informed community analyses, highlighting clade- and genotype-level affiliations of aquatic endophytes with both sediment- and waterborne fungi, and endophytes of proximate terrestrial plants. Together these analyses provide a first quantitative examination of endophytic associations in roots and foliage of aquatic plants and can be used to optimize survey strategies for efficiently capturing fungal biodiversity at local and regional scales.

  1. Checklist of the Aquatic Macrophytes

    African Journals Online (AJOL)

    The emergent macrophytes formed 93.3% of the total macrophyte .... accounted for 2.2% while emergent species with. 93.30% of ... proliferation of floating aquatic macrophytes like ..... Geoelectric Evalution of the Groundwater Potential of Parts.

  2. AMEG: the new SETAC advisory group on aquatic macrophyte ecotoxicology.

    Science.gov (United States)

    Arts, Gertie; Davies, Jo; Dobbs, Michael; Ebke, Peter; Hanson, Mark; Hommen, Udo; Knauer, Katja; Loutseti, Stefania; Maltby, Lorraine; Mohr, Silvia; Poovey, Angela; Poulsen, Véronique

    2010-05-01

    Primary producers play critical structural and functional roles in aquatic ecosystems; therefore, it is imperative that the potential risks of toxicants to aquatic plants are adequately assessed in the risk assessment of chemicals. The standard required macrophyte test species is the floating (non-sediment-rooted) duckweed Lemna spp. This macrophyte species might not be representative of all floating, rooted, emergent, and submerged macrophyte species because of differences in the duration and mode of exposure; sensitivity to the specific toxic mode of action of the chemical; and species-specific traits (e.g., duckweed's very short generation time). These topics were addressed during the workshop entitled "Aquatic Macrophyte Risk Assessment for Pesticides" (AMRAP) where a risk assessment scheme for aquatic macrophytes was proposed. Four working groups evolved from this workshop and were charged with the task of developing Tier 1 and higher-tier aquatic macrophyte risk assessment procedures. Subsequently, a SETAC Advisory Group, the Macrophyte Ecotoxicology Group (AMEG) was formed as an umbrella organization for various macrophyte working groups. The purpose of AMEG is to provide scientifically based guidance in all aspects of aquatic macrophyte testing in the laboratory and field, including prospective as well as retrospective risk assessments for chemicals. As AMEG expands, it will begin to address new topics including bioremediation and sustainable management of aquatic macrophytes in the context of ecosystem services.

  3. Effect of removal of free-floating macrophytes on zooplankton habitat in shallow wetland

    OpenAIRE

    Choi Jong-Yun; Jeong Kwang-Seuk; La Geung-Hwan; Joo Gea-Jae

    2014-01-01

    Submerged macrophytes improve the structural heterogeneity of microhabitats in aquatic ecosystems, often providing an important habitat for zooplankton. However, excessive development of free-floating macrophytes on the water surface can reduce the biomass of submerged macrophytes and result in a relatively simple habitat structure. We hypothesized that controlling the development of free-floating macrophytes would result in a more complex habitat structure by promoting the development of sub...

  4. Richness, biomass, and nutrient content of a wetland macrophyte community affect soil nitrogen cycling in a diversity-ecosystem functioning experiment

    Science.gov (United States)

    Korol, Alicia R.; Ahn, Changwoo; Noe, Gregory

    2016-01-01

    The development of soil nitrogen (N) cycling in created wetlands promotes the maturation of multiple biogeochemical cycles necessary for ecosystem functioning. This development proceeds from gradual changes in soil physicochemical properties and influential characteristics of the plant community, such as competitive behavior, phenology, productivity, and nutrient composition. In the context of a 2-year diversity experiment in freshwater mesocosms (0, 1, 2, 3, or 4 richness levels), we assessed the direct and indirect impacts of three plant community characteristics – species richness, total biomass, and tissue N concentration – on three processes in the soil N cycle – soil net ammonification, net nitrification, and denitrification potentials. Species richness had a positive effect on net ammonification potential (NAP) through higher redox potentials and likely faster microbial respiration. All NAP rates were negative, however, due to immobilization and high rates of ammonium removal. Net nitrification was inhibited at higher species richness without mediation from the measured soil properties. Higher species richness also inhibited denitrification potential through increased redox potential and decreased nitrification. Both lower biomass and/or higher tissue ratios of carbon to nitrogen, characteristics indicative of the two annual plants, were shown to have stimulatory effects on all three soil N processes. The two mediating physicochemical links between the young macrophyte community and microbial N processes were soil redox potential and temperature. Our results suggest that early-successional annual plant communities play an important role in the development of ecosystem N multifunctionality in newly created wetland soils.

  5. AMEG: the new SETAC advisory group on aquatic macrophyte ecotoxicology

    OpenAIRE

    Arts, G.; Davies, J.; Dobbs, M.; Ebke, P.; Hanson, M.; Hommen, U.; Knauer, K.; Loutseti, S.; Maltby, L; Mohr, S; Poovey, A.; Poulsen, V.

    2010-01-01

    \\ud Introduction and background\\ud \\ud Primary producers play critical structural and functional roles in aquatic ecosystems; therefore, it is imperative that the potential risks of toxicants to aquatic plants are adequately assessed in the risk assessment of chemicals. The standard required macrophyte test species is the floating (non-sediment-rooted) duckweed Lemna spp. This macrophyte species might not be representative of all floating, rooted, emergent, and submerged macrophyte species be...

  6. AMEG: the new SETAC advisory group on auqatic macrophyte ecotoxicology

    OpenAIRE

    Arts, G.H.P.; Davies, J.; Dobbs, M.; Ebke, P.; Hanson, M.A.

    2010-01-01

    ntroduction and background Primary producers play critical structural and functional roles in aquatic ecosystems; therefore, it is imperative that the potential risks of toxicants to aquatic plants are adequately assessed in the risk assessment of chemicals. The standard required macrophyte test species is the floating (non-sediment-rooted) duckweed Lemna spp. This macrophyte species might not be representative of all floating, rooted, emergent, and submerged macrophyte species because of dif...

  7. AMEG: the new SETAC advisory group on aquatic macrophyte ecotoxicology

    OpenAIRE

    Arts, G.; Davies, J.; Dobbs, M.; Ebke, P.; Hanson, M; Hommen, U.; Knauer, K; Loutseti, S.; Maltby, L.; Mohr, S.; Poovey, A.; Poulsen, V.

    2010-01-01

    \\ud Introduction and background\\ud \\ud Primary producers play critical structural and functional roles in aquatic ecosystems; therefore, it is imperative that the potential risks of toxicants to aquatic plants are adequately assessed in the risk assessment of chemicals. The standard required macrophyte test species is the floating (non-sediment-rooted) duckweed Lemna spp. This macrophyte species might not be representative of all floating, rooted, emergent, and submerged macrophyte species be...

  8. 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

  9. Factors involved in spatiotemporal dynamics of submerged macrophytes in a Portuguese coastal lagoon under Mediterranean climate

    Science.gov (United States)

    Antunes, Cristina; Correia, Otília; Marques da Silva, Jorge; Cruces, Anabela; Freitas, Maria da Conceição; Branquinho, Cristina

    2012-09-01

    Submerged macrophytes are key in coastal ecosystems, with important structural and functional roles. Thus, the characterization of the submerged aquatic vegetation dynamics is of prime importance for assessing the ecological status of coastal ecosystems. The main aim of this study was to assess the spatial and temporal dynamics of submerged macrophytes biomass in a temporarily open coastal lagoon in Melides, Portugal, and to evaluate the physiological performance of the dominant macrophyte in the system. This lagoon is subject to several disturbances such as the dramatic changes in water physicochemical parameters over time, since temporarily opens to the sea occur renewing the lagoon water content. Moreover it is under a Mediterranean climate with the inherently high temporal variability of precipitation and high temperatures during the summer. Our study shows that the submerged macrophyte community was dominated initially by Ruppia cirrhosa and then replaced by Potamogeton pectinatus, which showed a marked temporal and spatial pattern with extremely high values of biomass in August and in the inner part of the lagoon. The spatial and temporal biomass patterns in submerged macrophytes were mainly related with water level, salinity, pH and transparency. The physiological performance of R. cirrhosa was lower when there was greater biomass accumulation and in extremely shallow waters, whereas physiological vigor seemed to be greater at moderate temperatures and in areas with higher salinity and dissolved oxygen. The data from this study can be used to predict submerged biomass macrophyte responses to extreme water quality changes and to feed a decision support system for the best period to promote the seasonal artificial breaching of the sandy barrier.

  10. Dissolved organic carbon release by marine macrophytes

    Directory of Open Access Journals (Sweden)

    C. Barrón

    2012-02-01

    Full Text Available Estimates of dissolved organic carbon (DOC release by marine macrophyte communities (seagrass meadows and macroalgal beds were obtained experimentally using in situ benthic chambers. The effect of light availability on DOC release by macrophyte communities was examined in two communities both by comparing net DOC release under light and dark, and by examining the response of net DOC release to longer-term (days experimental shading of the communities. All most 85% of the seagrass communities and almost all of macroalgal communities examined acted as net sources of DOC. There was a weak tendency for higher DOC fluxes under light than under dark conditions in seagrass meadow. There is no relationship between net DOC fluxes and gross primary production (GPP and net community production (NCP, however, this relationship is positive between net DOC fluxes and community respiration. Net DOC fluxes were not affected by shading of a T. testudinum community in Florida for 5 days, however, shading of a mixed seagrass meadow in the Philippines led to a significant reduction on the net DOC release when shading was maintained for 6 days compared to only 2 days of shading. Based on published and unpublished results we also estimate the global net DOC production by marine macrophytes. The estimated global net DOC flux, and hence export, from marine macrophyte is about 0.197 ± 0.015 Pg C yr−1 or 0.212 ± 0.016 Pg C yr−1 depending if net DOC flux by seagrass meadows was estimated by taking into account the low or high global seagrass area, respectively.

  11. 斧头湖水生植物多样性及群落演替研究%DIVERSITY VARIATION AND COMMUNITY SUCCESSION OF AQUATIC MACROPHYTES IN LAKE FUTOU

    Institute of Scientific and Technical Information of China (English)

    李中强; 任慧; 郝孟曦; 张萌; 徐军

    2012-01-01

    . Before the early 1980s, vegetation coverage was 100%. At the end of 1980s, coverage decresed to 80.5%, and the coverage further decresed significantly to 16.7% in 1999 and increased to 47.9% in 2009. From 1988 to 2009, emergent macrophytes increased the coverage from 24.18% to 56.93%, and Nelumbo nucifera became the dominant species in the summer. In this period, the coverages of submersed and floating-leaved macrophytes declined from Al.25% and 28.57% to 29.21% and 10.35%, respectively. Associations dominated by Nymphoides peltata in floating-leaved plants and dominated by Elodea nuttalli in submersed plants increased in the communities. Associations of Ceratophyllum demersum, Myriophyllum spicatum, and Ceratophyllum demersum also increased. Potamogeton maackianus decreased significantily. Overall, the aquatic macrophyte communities in the lake have changed markedly since the natural succession status in the 1950s changed toward the artificial succession status due to human disturbances observed in this study. Vegetation type, vegetation coverage, biomass and structure of community changed drastically. Our analyses indicated that the main reasons of species replacement of aquatic plant were human disturbances such as aquaculture in enclosures, mowing and introducing species, and natural factors such as water level fluctuation, life span and reproduction strategy. Based on this study, thorough planning of comprehensive exploitation and utilization of Lake Futou are needed in future lake management.%根据2009年调查结果,结合分析前人研究资料,研究了斧头湖水生植物多样性及其群落的变化.结果表明从1988-2009年近20年间斧头湖水生植物种类和优势种均发生一定程度的变化,一些对干扰较为敏感的种类如睡莲已经消失,原来的优势种如微齿眼子菜、密齿苦草和轮叶黑藻等变为亚优势种或伴生种; 同时出现一些人工栽培外来水生植物.斧头湖水生植被由20世纪50年代的自

  12. Effect of removal of free-floating macrophytes on zooplankton habitat in shallow wetland

    Directory of Open Access Journals (Sweden)

    Choi Jong-Yun

    2014-01-01

    Full Text Available Submerged macrophytes improve the structural heterogeneity of microhabitats in aquatic ecosystems, often providing an important habitat for zooplankton. However, excessive development of free-floating macrophytes on the water surface can reduce the biomass of submerged macrophytes and result in a relatively simple habitat structure. We hypothesized that controlling the development of free-floating macrophytes would result in a more complex habitat structure by promoting the development of submerged macrophytes. After applying three experimental treatments (NR, no removal; IR, intermediate removal; CR, complete removal of free-floating macrophytes, we found that CR of free-floating macrophytes improved the growth and development of submerged macrophytes and supported a large zooplankton assemblage. However, the largest zooplankton assemblage (in terms of abundance and diversity was recorded after the IR treatment. Although submerged macrophytes were abundant in the CR treatment, the number, abundance, and density of zooplankton species were much lower than those in the IR treatment. Preferential selection of different macrophyte types by zooplankton presumably led to variation in plant utilization of niches, and the simultaneous presence of different macrophyte life forms created a complex microhabitat structure that induced high species diversity and zooplankton density.

  13. Diaspore bank of aquatic macrophytes maintaining species diversity in a Neotropical pond

    Directory of Open Access Journals (Sweden)

    Fernando Alves Ferreira

    2016-12-01

    Full Text Available The diaspore bank is an important component of biological diversity acting mainly as storage and source of diaspores, which also indicate dynamics and patterns of maintenance of plant diversity. We tested the hypothesis that the diaspore bank would be the responsible factor for the maintenance of the aquatic plant species, used two techniques to evaluate the diaspore bank: seedling emergence and direct counting of field samples. Density and richness of the diaspore bank were correlated with plant cover of the aquatic macrophyte communities and also with the euphotic zone radiation in different phases of the hydrological cycle. The diaspore bank is a key factor in maintenance of aquatic macrophyte assemblages in this pond. Nymphaea amazonum was one of the dominant species in the pond and presented temporally peaks of plant cover. Furthermore, depth allowed induction of germination of stored diaspores. Therefore, the diaspore bank may predict which species colonizes a site when environmental characteristics are favorable and allows inferring which processes are linked to changes in structure of aquatic macrophyte assemblages. These mechanisms are the means for recovery of macrophyte species under natural disturbances, represented by water level oscillations in floodplains.

  14. Microbial community diversity and composition varies with habitat characteristics and biofilm function in macrophyte-rich streams

    DEFF Research Database (Denmark)

    Levi, Peter S.; Starnawski, Piotr; Poulsen, Britta

    2017-01-01

    Biofilms in streams play an integral role in ecosystem processes and function yet few studies have investigated the broad diversity of these complex prokaryotic and eukaryotic microbial communities. Physical habitat characteristics can affect the composition and abundance of microorganisms...

  15. Response of littoral macrophytes to water level fluctuations in a storage reservoir

    OpenAIRE

    Krolová M.; Čížková H.; Hejzlar J.; Poláková S.

    2013-01-01

    Lakes and reservoirs that are used for water supply and/or flow regulations have usually poorly developed littoral macrophyte communities, which impairs ecological potential in terms of the EU Water Framework Directive. The aim of our study was to reveal controlling factors for the growth of littoral macrophytes in a storage reservoir with fluctuating water level (Lipno Reservoir, Czech Republic). Macrophytes occurred in this reservoir only in the eulittoral zone i.e., the shoreline region be...

  16. Macrophytes: Limitations of Using Them to Assess Reservoir Status According to the Water Framework Directive

    OpenAIRE

    Alaoui, Khadija Sossey; Galoux, Daniel; Rosillon, Francis

    2014-01-01

    Macrophytes are among the major groups of organisms that the Water Framework Directive (WFD) recommends should be used in assessing the status of natural lakes. The use of macrophytes in reservoir monitoring is still limited and further studies are needed on their inter-calibration and sources of variation. Many status assessment methods based on macrophyte communities have been defined for lakes. Nevertheless, few of them have been tested for reservoirs. The purpose of the study is to hig...

  17. Response of littoral macrophytes to water level fluctuations in a storage reservoir

    OpenAIRE

    Krolová M.; Čížková H.; Hejzlar J.; Poláková S.

    2013-01-01

    Lakes and reservoirs that are used for water supply and/or flow regulations have usually poorly developed littoral macrophyte communities, which impairs ecological potential in terms of the EU Water Framework Directive. The aim of our study was to reveal controlling factors for the growth of littoral macrophytes in a storage reservoir with fluctuating water level (Lipno Reservoir, Czech Republic). Macrophytes occurred in this reservoir only in the eulittoral zone i.e., the shoreline region be...

  18. Archaea Dominate the Ammonia-Oxidizing Community in the Rhizosphere of the Freshwater Macrophyte Littorella uniflora

    DEFF Research Database (Denmark)

    Herrmann, Martina; Saunders, Aaron M.; Schramm, Andreas

    2008-01-01

    Archaeal and bacterial ammonia monooxygenase genes (amoA) had similar low relative abundances in freshwater sediment. In the rhizosphere of the submersed macrophyte Littorella uniflora, archaeal amoA was 500- to >8,000-fold enriched compared to bacterial amoA, suggesting that the enhanced...

  19. Habitat and scale shape the demographic fate of the keystone sea urchin Paracentrotus lividus in Mediterranean macrophyte communities.

    Directory of Open Access Journals (Sweden)

    Patricia Prado

    Full Text Available Demographic processes exert different degrees of control as individuals grow, and in species that span several habitats and spatial scales, this can influence our ability to predict their population at a particular life-history stage given the previous life stage. In particular, when keystone species are involved, this relative coupling between demographic stages can have significant implications for the functioning of ecosystems. We examined benthic and pelagic abundances of the sea urchin Paracentrotus lividus in order to: 1 understand the main life-history bottlenecks by observing the degree of coupling between demographic stages; and 2 explore the processes driving these linkages. P. lividus is the dominant invertebrate herbivore in the Mediterranean Sea, and has been repeatedly observed to overgraze shallow beds of the seagrass Posidonia oceanica and rocky macroalgal communities. We used a hierarchical sampling design at different spatial scales (100 s, 10 s and <1 km and habitats (seagrass and rocky macroalgae to describe the spatial patterns in the abundance of different demographic stages (larvae, settlers, recruits and adults. Our results indicate that large-scale factors (potentially currents, nutrients, temperature, etc. determine larval availability and settlement in the pelagic stages of urchin life history. In rocky macroalgal habitats, benthic processes (like predation acting at large or medium scales drive adult abundances. In contrast, adult numbers in seagrass meadows are most likely influenced by factors like local migration (from adjoining rocky habitats functioning at much smaller scales. The complexity of spatial and habitat-dependent processes shaping urchin populations demands a multiplicity of approaches when addressing habitat conservation actions, yet such actions are currently mostly aimed at managing predation processes and fish numbers. We argue that a more holistic ecosystem management also needs to incorporate the

  20. Remote Sensing supports EULAKES project for mapping submerged macrophytes in Lake Garda

    Science.gov (United States)

    Matta, Erica; Bresciani, Mariano; Giardino, Claudia; Bolpagni, Rossano; Pellegrini, Giovanna; Braga, Federica

    2013-04-01

    Lake bottoms have an important role in the aquatic ecosystem: bathymetry and morphology may affect the hydrodynamic processes in coastal waters, while the presence of aquatic macrophytes helps to preserve the ecology. Within the context of macrophyte monitoring programs, technical advances in remote sensing with higher spatial and spectral resolutions provide opportunities for big scale ecological studies, with the possibility to assess a multitemporal analysis. One of the objectives of the EULAKES project has been to map aquatic vegetation cover inside the Garda Lake from hyperspectral MIVIS (Multispectral Infrared and Visible Imaging Spectrometer) aerial images thanks to the application of a bio-optical model inversion technique (BOMBER: Bio-Optical Model Based tool for Estimating water quality and bottom properties from Remote sensing images). MIVIS images, with a spectral resolution of 102 bands, working between 430 and 1270 nm, were previously corrected for atmospheric, adjacency and glint effects before being processed with the BOMBER tool. One complete MIVIS overflight (12 runs) acquired on June 27th 2011, allowed the retrieval of a macrophyte presence map all around the first 7m deep coastal belt, with a validation error of about 10%, resulting from 89 in situ measures performed during images acquisition. A relevant spatial distribution could be observed, with higher aquatic plants concentration in the Southern part of the lake. A further local cover distribution map localized on the Sirmione Peninsula was integrated with previous results to perform a temporal analysis of macrophyte colonization patterns along this reduced littoral zone for the last 14 years (acquisitions on September 1997, July 2005 and July 2010). Considerable modifications in terms of macrophyte structural complexity and colonized areas were detectable: a drastic reduction of well-established dense communities (more than 70% of cover) and increasing of un-colonized areas were followed by

  1. The phylogeographic structure of Hydrilla verticillata (Hydrocharitaceae) in China and its implications for the biogeographic history of this worldwide-distributed submerged macrophyte.

    Science.gov (United States)

    Zhu, Jinning; Yu, Dan; Xu, Xinwei

    2015-05-24

    Aquatic vascular plants are a distinctive group, differing from terrestrial plants in their growth forms and habitats. Among the various aquatic plant life forms, the evolutionary processes of freshwater submerged species are most likely distinct due to their exclusive occurrence in the discrete and patchy aquatic habitats. Using the chloroplast trnL-F region sequence data, we investigated the phylogeographic structure of a submerged macrophyte, Hydrilla verticillata, the single species in the genus Hydrilla, throughout China, in addition to combined sample data from other countries to reveal the colonisation and diversification processes of this species throughout the world. We sequenced 681 individuals from 123 sampling locations throughout China and identified a significant phylogeographic structure (NST > GST, p China indicates that China is most likely the centre of Hydrilla genetic diversity. The worldwide distribution of Hydrilla is due to recent vicariance and dispersal events that occurred in different clades during the Pleistocene. Our findings also provide useful information for the management of invasive Hydrilla in North America.

  2. Aquatic macrophytes in cool aseasonal and seasonal streams: a comparison between Ecuadorian highland and Danish lowland streams

    DEFF Research Database (Denmark)

    Jacobsen, Dean; Terneus, Esteban

    2001-01-01

    -forms (submerged, amphibious, semiaquatic) was, however, different as submerged plants were less diverse in the Ecuadorian streams. Further, all submerged plants found in the Ecuadorian streams belonged to cosmopolitan genera with a mainly north-temperate distribution. We suggest that the low number of submerged......The diversity and community structure of aquatic macrophytes in aseasonal streams cool by altitude and seasonal streams cool by latitude was compared using a standardised approach. The aquatic vegetation in 12 small highland streams in the Ecuadorian Andes (3400–4100 m) and in 12 physically...... and chemically similar lowland streams in Denmark was examined. Our study confirmed that aquatic macrophyte communities in the neotropics are not particularly species rich. Total as well as mean species richness per stream were about the same in the two regions. The species richness within different life...

  3. Influence of Disturbance on Habitats and Biological Communities in Lowland Streams

    DEFF Research Database (Denmark)

    Pedersen, Morten Lauge; Friberg, N.

    2009-01-01

    We studied 68 small lowland streams in Denmark of which the majority were affected by physical and chemical stress or a combination of both. Using DCA analyses, we analysed macrophyte and macroinvertebrate communities along a combined disturbance gradient. Both macrophytes and macroinvertebrate...... communities responded to the combined pressure gradient. We used a rigorous classification of the 68 sites, into 5 disturbance groups, with respect to physical and chemical disturbance and studied the effects of disturbance on physical habitat structure and density and diversity of macrophytes......, macroinvertebrates and fish. Physical habitat structure in the disturbed streams was similar, except for variations in width which was lowest, and coverage of mud, which was highest in heavily disturbed streams. Macrophyte communities were impacted by disturbance. Average species richness and diversity were...

  4. Ocean Acidification Differentially Affects the Photosynthesis of Key New England Macrophytes

    Science.gov (United States)

    Fachon, E.; Ets-Hokin, J. M.; Donham, E. M.; Price, N.

    2016-02-01

    While the influence of anthropogenic CO2 emissions on seawater chemistry is detrimental to calcification among CaCO3 reliant organisms such as commercially important shellfish species, non-calcareous macrophytes like seagrasses and seaweeds can experience enhanced growth under elevated pCO2 conditions and may be a substantial, if ephemeral, CO2 sink. Most marine macrophytes rely on enzyme conversion of HCO3- to supply the inorganic carbon necessary for photosynthesis; the ability to down-regulate this energetically expensive carbon acquisition under high pCO2 conditions could determine future species success. We exposed four commercially and ecologically relevant New England macrophytes (Saccharina latissima, Fucus vesiculosus, Ulva lactuca, and Zostera marina) to pre-industrial (280 uatm), present (400 and 520 utam - recorded in Casco Bay) and future (640, 880 and 1120 uatm - as predicted by the IPCC) pCO2 levels in 1.5 hr long respirometry assays after 72 hrs acclimation. CO2 consumption, photosynthetic quotient (Q = CO2 consumed:O2 evolved), and change in carbonate saturation state (Ωcalcite) were calculated for each sample using differences in initial and final carbonate chemistry and dissolved oxygen concentrations. All species experienced increases in rate of CO2 uptake and Q under elevated pCO2 treatments, but response level differed across species. Saccharina latissima had the greatest relative effect on all parameters measured, consuming 4 times more carbon at high pCO2 levels than the lowest performing species. While all macrophytes were able to raise Ωcalcite, the magnitude of change decreased at higher pCO2 levels, suggesting a limitation to the degree to which photosynthesis can locally raise calcification potential for sensitive native or farmed populations of shellfish in the future. The varied responses observed across species have implications for future community structures and for phytoremediation efforts.

  5. Fluoride remediation using floating macrophytes

    Directory of Open Access Journals (Sweden)

    Naba Kumar Mondal

    2014-04-01

    Full Text Available Six aquatic macrophytes, such as Pistia stratiotes, Ceratophyllum demersum, Nymphoides indica, Lemna major, Azolla pinnata,and Eichhornia crassipes were considered for remove fluoride from aqueous solution. Five different concentrations (10, 30, 50, and 100 ppm of fluoride solution were taken in 1 L plastic container. Fixed weight (20 g of macrophytes along with 500 ml fluoride solution was taken in each plastic container for 72 hours observation. Results demonstrated all the macrophytes show highest fluoride removal during 24 h to 48 h, but after 72 h their efficiency reduced drastically. The species N. indica showed better removal efficiency than other experimental macrophytes. In general, pigment measurement data indicated higher concentration at 72 h. However, Pistia sp. showed higher concentration of pigmentation at intermediate time interval (48 h. Higher level of dry weight to fresh weight ratio was recorded for L. major and A. pinnata at all concentrations, excepting at 10 ppm. In addition, all macrophytes showed lower RGR at higher concentration. Isotherm study indicated that macrophyte C. demersum is a good fitted with Freundlich and Langmuir isotherm whereas L. major with Langmuir isotherm during 24 hours.

  6. Response of littoral macrophytes to water level fluctuations in a storage reservoir

    National Research Council Canada - National Science Library

    Krolová, M; Čížková, H; Hejzlar, J; Poláková, S

    2013-01-01

    Lakes and reservoirs that are used for water supply and/or flow regulations have usually poorly developed littoral macrophyte communities, which impairs ecological potential in terms of the EU Water Framework Directive...

  7. Macrophytes shape trophic niche variation among generalist fishes

    Science.gov (United States)

    Vejřík, Lukáš; Šmejkal, Marek; Čech, Martin; Sajdlová, Zuzana; Frouzová, Jaroslava; Kiljunen, Mikko; Peterka, Jiří

    2017-01-01

    Generalist species commonly have a fundamental role in ecosystems as they can integrate spatially distinct habitats and food-web compartments, as well as control the composition, abundance and behavior of organisms at different trophic levels. Generalist populations typically consist of specialized individuals, but the potential for and hence degree of individual niche variation can be largely determined by habitat complexity. We compared individual niche variation within three generalist fishes between two comparable lakes in the Czech Republic differing in macrophyte cover, i.e. macrophyte-rich Milada and macrophyte-poor Most. We tested the hypothesis that large individual niche variation among generalist fishes is facilitated by the presence of macrophytes, which provides niches and predation shelter for fish and their prey items. Based on results from stable nitrogen (δ15N) and carbon (δ13C) isotopic mixing models, perch (Perca fluviatilis L.) and rudd (Scardinius erythrophthalmus (L.)) showed larger individual variation (i.e., variance) in trophic position in Milada as compared to Most, whereas no significant between-lake differences were observed for roach (Rutilus rutilus (L.)). Contrary to our hypothesis, all the three species showed significantly lower individual variation in the relative reliance on littoral food resources in Milada than in Most. Rudd relied significantly more whereas perch and roach relied less on littoral food resources in Milada than in Most, likely due to prevalent herbivory by rudd and prevalent zooplanktivory by perch and roach in the macrophyte-rich Milada as compared to macrophyte-poor Most. Our study demonstrates how the succession of macrophyte vegetation, via its effects on the physical and biological complexity of the littoral zone and on the availability of small prey fish and zooplankton, can strongly influence individual niche variation among generalist fishes with different ontogenetic trajectories, and hence the overall

  8. Role of macrophyte life forms in driving periphytic microalgal assemblages in a Brazilian reservoir

    Directory of Open Access Journals (Sweden)

    Ubirajara L. Fernandes

    2015-08-01

    Full Text Available Macrophytes play several roles in aquatic ecosystems, including the provision of habitat for many aquatic organisms, especially the periphyton. The aims of this study were to characterize the structure of periphytic microalgal assemblages on different aquatic macrophyte life forms in order to establish similarities between assemblages from nearby sampling sites. We hypothesized that i aquatic macrophytes with different life forms and morphological characteristics could differently influence the structure of the periphyton and that ii the greatest similarity in periphyton composition should be observed among macrophytes that occupy the same sampling site. The study was conducted from 2006 to 2008 in the Thomaz Osterne de Alencar reservoir (Crato City, Ceará State, Brazil and involved the taxonomic surveying of microalgae attached to five different macrophytes with the application of structural descriptors (richness, abundance, frequency, diversity and equitability. A total of 127 taxa, of which 44% belonged to the Chlorophyta, were identified. The microalgae assemblages showed high species richness on Salvinia auriculata Aubl., a free-floating macrophyte, and large abundance on Apalanthe granatensis (Humb. & Bonpl. Planch., a submerged anchored macrophyte. ANOVA indicated that periphyton significantly varied among the macrophytes investigated, and nearby sampling sites showed no structural similarities in microalgal assemblages. In general, we can conclude that the structure of periphyton assemblages is influenced by the substrate (i.e., macrophyte organ, as this can not only promote high diversity and equitability but can also be a predictor of dissimilarity in the distribution and frequency of occurrence of microalgae. These results reinforce the findings of other studies that have shown that macrophytes play an important role in structuring the periphyton assemblages.

  9. Reconstruction and water purification of submerged macrophytes community in eutrophicated Gehu Lake during summer%夏季富营养化滆湖中沉水植物群落重建及水质净化效果

    Institute of Scientific and Technical Information of China (English)

    黄峰; 李勇; 潘继征; 陶花; 赵海光

    2011-01-01

    通过滆湖原位围隔试验分析了不同单种及混种沉水植物群落随环境变化的生长状况及对水质的净化效果.结果表明:(1)夏季,沉水植物生物量的平均值与透明度/水位存在显著线性相关性,进一步表明沉水植物的生长在很大程度上依赖于光强和水深.(2)各植物区(除马来眼子菜区外)的高锰酸盐指数、TN高于空白对照区.(3)对比空白对照区,苦草区、金鱼藻区、金鱼藻—伊乐藻区对NH3-N、TP、叶绿素a的去除率都在25%以上.对比敞水区,金鱼藻—伊乐藻区、苦草—马来眼子菜区、苦草—伊乐藻区对TP的去除率分别为33.5%、20.8%、9.9%;金鱼藻—伊乐藻区对叶绿素a的去除率为41.4%.(4)TP和叶绿素a存在显著线性关系,反映了沉水植物可通过对TP的去除有效控制藻类的生长.(5)苦草、金鱼藻—伊乐藻群落、苦草—马来眼子菜群落对水体中NH3-N、TP、叶绿素a的平均去除速率(V)都符合V-时间(t)回归方程.(6)在沉水植物群落恢复中可优先考虑金鱼藻—伊乐藻、苦草—马来眼子菜群落等有稳定及较高平均去除速率的沉水植物群落重建形式.%In-situ enclosure experiment was conducted in Genu Lake to investigate the effect of environmental change on growth and purification performance of different single and mixture submerged macrophytes community. Results showed that the average biomass of submerged macrophytes was significant linearly correlated with transparency and water level, which indicated that the growth of submerged macrophytes was highly dependent on the light intensity and water depth. The permanganate index and TN in test area were higher than that in control area except for the test area planting Potamogeton malaianus. Compared with control area, planting Vallisneria spiralis, Cera-tophyllum demersum and Ceratophyllum demersum-Elodea nuttallii could removal more than 25% of NH3-N, TP and chlorophyll-a; Compared

  10. AMEG: the new SETAC advisory group on auqatic macrophyte ecotoxicology

    NARCIS (Netherlands)

    Arts, G.H.P.; Davies, J.; Dobbs, M.; Ebke, P.; Hanson, M.A.

    2010-01-01

    ntroduction and background Primary producers play critical structural and functional roles in aquatic ecosystems; therefore, it is imperative that the potential risks of toxicants to aquatic plants are adequately assessed in the risk assessment of chemicals. The standard required macrophyte test

  11. AMEG: the new SETAC advisory group on auqatic macrophyte ecotoxicology

    NARCIS (Netherlands)

    Arts, G.H.P.; Davies, J.; Dobbs, M.; Ebke, P.; Hanson, M.A.

    2010-01-01

    ntroduction and background Primary producers play critical structural and functional roles in aquatic ecosystems; therefore, it is imperative that the potential risks of toxicants to aquatic plants are adequately assessed in the risk assessment of chemicals. The standard required macrophyte test spe

  12. Structure and function of the bacterial communities during rhizoremediation of hexachlorobenzene in constructed wetlands.

    Science.gov (United States)

    Zhang, Cuiping; Wang, Bei; Dai, Xiaoyan; Li, Shuying; Lu, Guangqiu; Zhou, Yuanqing

    2017-04-01

    Vertical flow constructed wetlands (VF CWs) are considered to be effective for treating organic pollutants. The rhizosphere of macrophytes such as Phragmites sp., Typha sp. serves as an active and dynamic zone for the microbial degradation of organic pollutants. However, it is still not clear how soil bacterial communities respond to macrophytes and pollutants during the process. For this purpose, the seedlings of Phragmites australis and Typha angustifolia were planted respectively in the VF CWs added with HCB at a dose of 2 mg/kg. During 96 days of cultivation, we monitored hexachlorobenzene (HCB) removal efficiency by GC/MS and the structure of the rhizosphere bacterial communities in the different VF CWs by denaturing gradient gel electrophoresis (DGGE), and constructed bacterial clone library based on PCR-amplified 16S rRNA gene. As expected, the rhizosphere bacterial communities also remained insensitive to HCB exposure in the wetland soil. The diversity of these microbes presented two stages, from the varied up and down to equilibrium in the entire experimental period. Molecular analysis revealed that the phylum Firmicutes dominated over the bacterial communities. The genera that increased under HCB stress included the well-known HCB-degrading bacteria (Pseudomonas sp. and Alcaligenes sp.) and other common bacteria found in contaminated soil but with lesser known practical functions (Burkholderia sp., Lysinibacillus fusiformis, and Bacillus cereus). Furthermore, there was a certain variance in the relative abundances of the bacterial phyla and HCB removal efficiency among different VF CW treatments. The degradation of HCB in T. angustifolia microcosms was faster than that in P. australis and unvegetated wetlands, and the highest bacterial diversity and richness was found in the VF CWs comprising T. angustifolia.

  13. Regulation and role of epiphytic nitrification and denitrification in macrophyte-dominated systems

    Energy Technology Data Exchange (ETDEWEB)

    Eriksson, Peder G.

    2000-02-01

    This thesis examines mechanisms regulating bacterial nitrification and denitrification in attached microbial communities on surfaces of aquatic macrophytes. It also evaluates the role of epiphytic nitrification and denitrification for the nitrogen turnover in macrophyte-dominated nutrient-rich freshwater. Epiphytic nitrification is promoted in light and epiphytic denitrification occurs mainly in dark, because the metabolic activity of the aquatic macrophyte and its epiphytes induce in light high and in dark low oxygen concentrations in epiphytic communities. Epiphytic nitrification and denitrification are also affected by the physical and chemical characteristics of the aquatic macrophyte. The spatial distribution of nitrification in emergent macrophyte wetlands is related to the species composition of the emergent vegetation, possibly because of a macrophyte species-related release of organic nitrification inhibitors. Contrasting to nitrifying bacteria, which are lithotrophic, denitrifying bacteria use organic substances as an energy source and are therefore stimulated by the release of organic matter from aquatic macrophytes. Epiphytic communities support more denitrification in nutrient-rich than in nutrient-poor environments. In lakes and ponds, epiphytic denitrification is higher at sheltered locations than at locations exposed to wind-induced water movements or currents. In flowing water, epiphytic denitrification occurs mainly at low oxygen concentrations in the surrounding water. However, because aquatic macrophytes impede water flow and induce low oxygen concentrations in dark, epiphytic denitrification can be present within dense vegetation despite of high oxygen concentrations in the surrounding water. Epiphytic nitrification is almost unaffected by flow conditions, and can occur both in light and in dark. In shallow-water systems such as treatment wetlands, aquatic macrophytes often provide most of the accessible surface area for attached nitrifying and

  14. Analysis of the impact of water level fluctuations on macrophytes in Miyun Reservoir after receiving water transferred by the South-to-North Water Diversion Project

    Science.gov (United States)

    Yu, L.; Gu, H.; Lou, C. H.; Zhang, L.; Meng, Q. Y.

    2016-08-01

    As the main primary producers in aquatic ecosystems, macrophytes affect the structure and function of aquatic ecosystems, and their distribution is controlled by water depth. Miyun Reservoir in Beijing will have to experience substantial changes in water level and surface area as it begins to receive water transferred by the South-to-North Water Diversion Project, which will have an adverse impact on the macrophytes growing there. In this study, a hydrodynamic model was constructed with MIKE21 and then used in a simulation in three scenarios: dry year, normal year and wet year. The results suggest that during water diversion, the annual and interannual water level fluctuations will be too significant for them to adapt and as a result, the original macrophytes in the reservoir tend to die and disappear completely. The area of the zone suitable for macrophyte growth, or suitable growth zone (SGZ), fluctuated. Restricted by the main dam and auxiliary dam to its south, the overall suitable growth zone moved toward the northeast and northwest of the reservoir, with a northeastward movement of its centroid. The distance and path of movement varied between scenarios. After the water diversion was completed, the suitable growth zone shrunk in the three scenarios. It is predicted that the macrophyte species diversity and richness of the reservoir can recover to the levels recorded before water diversion only in dry year. These results suggest that manual interventions should be implemented after water diversion to speed up the natural recovery of aquatic plant communities in Miyun Reservoir and thereby maintain the stability of the aquatic ecosystem.

  15. Spatiotemporal patterns in community structure of macroinvertebrates inhabiting calcareous periphyton mats

    Science.gov (United States)

    Liston, S.E.; Trexler, J.C.

    2005-01-01

    Calcareous floating periphyton mats in the southern Everglades provide habitat for a diverse macroinvertebrate community that has not been well characterized. Our study described this community in an oligotrophic marsh, compared it with the macroinvertebrate community associated with adjacent epiphytic algae attached to macrophytes in the water column, and detected spatial patterns in density and community structure. The floating periphyton mat (floating mat) and epiphytic algae in the water column (submerged epiphyton) were sampled at 4 sites (???1 km apart) in northern Shark River Slough, Everglades National Park (ENP), in the early (July) and late (November) wet season. Two perpendicular 90-m transects were established at each site and ???100 samples were taken in a nested design. Sites were located in wet-prairie spikerush-dominated sloughs with similar water depths and emergent macrophyte communities. Floating mats were sampled by taking cores (6-cm diameter) that were sorted under magnification to enumerate infauna retained on a 250-??m-mesh sieve and with a maximum dimension >1 mm. Our results showed that floating mats provide habitat for a macroinvertebrate community with higher densities (no. animals/g ash-free dry mass) of Hyalella azteca, Dasyhelea spp., and Cladocera, and lower densities of Chironomidae and Planorbella spp. than communities associated with submerged epiphyton. Densities of the most common taxa increased 3x to 15x from early to late wet season, and community differences between the 2 habitat types became more pronounced. Floating-mat coverage and estimated floating-mat biomass increased 20 to 30%, and 30 to 110%, respectively, at most sites in the late wet season. Some intersite variation was observed in individual taxa, but no consistent spatial pattern in any taxon was detected at any scale (from 0.2 m to 3 km). Floating mats and their resident macroinvertebrate communities are important components in the Everglades food web. This

  16. Discovering Network Structure Beyond Communities

    CERN Document Server

    Nishikawa, Takashi; 10.1038/srep00151

    2011-01-01

    To understand the formation, evolution, and function of complex systems, it is crucial to understand the internal organization of their interaction networks. Partly due to the impossibility of visualizing large complex networks, resolving network structure remains a challenging problem. Here we overcome this difficulty by combining the visual pattern recognition ability of humans with the high processing speed of computers to develop an exploratory method for discovering groups of nodes characterized by common network properties, including but not limited to communities of densely connected nodes. Without any prior information about the nature of the groups, the method simultaneously identifies the number of groups, the group assignment, and the properties that define these groups. The results of applying our method to real networks suggest the possibility that most group structures lurk undiscovered in the fast-growing inventory of social, biological, and technological networks of scientific interest.

  17. Discovering network structure beyond communities.

    Science.gov (United States)

    Nishikawa, Takashi; Motter, Adilson E

    2011-01-01

    To understand the formation, evolution, and function of complex systems, it is crucial to understand the internal organization of their interaction networks. Partly due to the impossibility of visualizing large complex networks, resolving network structure remains a challenging problem. Here we overcome this difficulty by combining the visual pattern recognition ability of humans with the high processing speed of computers to develop an exploratory method for discovering groups of nodes characterized by common network properties, including but not limited to communities of densely connected nodes. Without any prior information about the nature of the groups, the method simultaneously identifies the number of groups, the group assignment, and the properties that define these groups. The results of applying our method to real networks suggest the possibility that most group structures lurk undiscovered in the fast-growing inventory of social, biological, and technological networks of scientific interest.

  18. 水生植物对沉积物微生物群落功能多样性的影响%Effects of Aquatic Macrophyte Planting on Functional Diversity of Microbial Community in Sediment

    Institute of Scientific and Technical Information of China (English)

    赵良元; 陶晶祥; 刘敏

    2015-01-01

    Differences in the functiona1 diversity of microbia1 community between rhizosphere sediment of Acorus calamus and non-rhizosphere sediment were investigated using Biolog-Eco microplates.Results showed that the growth of Acorus calamus could significantly increase the microbial activity and diversity in the rhizosphere sedi-ment.The total microorganism activity (AWCD,average well color development)and the diversity including the Shannon-Wiener index,Simpson index,richness index and Pielou evenness index of rhizosphere sediment was sig-nificantly higher than that of non-rhizosphere sediment.Microorganisms using sugar as the main carbon source was the main microorganism groups in the rhizosphere sediment of Acorus calamus,whereas microbes in the non-rhizo-sphere sediment mainly used ester and amine as carbon source.The carbon sources causing the metabolic differ-ences between non-rhizosphere sediment and rhizosphere sediment were D-Cellobiose,β-Methyl-D-Glucoside,Glu-cose-1-Phosphate,D-Galacturonic Acid,D-Glucosaminic Acid,Phenylethyl-amine,N-Acetyl-D-Glucosamine,D-Galactonic Acid y-Lactone,D-Mannitol and D,L-a-Glycerol.Analysis on the differences of functional diversity in microbial community between rhizosphere and nonrhizosphere sediment aims to reveal the mechanism of rhizosphere effect of aquatic macrophyte and provides scientific basis for improving the efficiency of pollutant removal by aquatic macrophyte.%为研究水生植物对沉积物微生物群落功能多样性的影响,采用Biolog-Eco微平板法分析非根际沉积物及菖蒲根际沉积物微生物群落功能多样性差异。结果表明:水生植物菖蒲的生长可大大提高沉积物中微生物的活性及多样性,菖蒲根际微生物总活性(AWCD)、微生物多样性指数(包括Shannon-Wiener 指数、丰富度指数及Pielou 均匀度指数)均显著高于非根际沉积物;菖蒲根际沉积物微生物主要是一些利用酯类及糖类作为碳源的微生物

  19. Vulnerabilities of macrophytes distribution due to climate change

    Science.gov (United States)

    Hossain, Kaizar; Yadav, Sarita; Quaik, Shlrene; Pant, Gaurav; Maruthi, A. Y.; Ismail, Norli

    2017-08-01

    The rise in the earth's surface and water temperature is part of the effect of climatic change that has been observed for the last decade. The rates of climate change are unprecedented, and biological responses to these changes have also been prominent in all levels of species, communities and ecosystems. Aquatic-terrestrial ecotones are vulnerable to climate change, and degradation of the emergent aquatic macrophyte zone would have contributed severe ecological consequences for freshwater, wetland and terrestrial ecosystems. Most researches on climate change effects on biodiversity are contemplating on the terrestrial realm, and considerable changes in terrestrial biodiversity and species' distributions have been detected in response to climate change. This is unfortunate, given the importance of aquatic systems for providing ecosystem goods and services. Thus, if researchers were able to identify early-warning indicators of anthropogenic environmental changes on aquatic species, communities and ecosystems, it would certainly help to manage and conserve these systems in a sustainable way. One of such early-warning indicators concerns the expansion of emergent macrophytes in aquatic-terrestrial ecotones. Hence, this review highlights the impact of climatic changes towards aquatic macrophytes and their possible environmental implications.

  20. Vulnerabilities of macrophytes distribution due to climate change

    Science.gov (United States)

    Hossain, Kaizar; Yadav, Sarita; Quaik, Shlrene; Pant, Gaurav; Maruthi, A. Y.; Ismail, Norli

    2016-06-01

    The rise in the earth's surface and water temperature is part of the effect of climatic change that has been observed for the last decade. The rates of climate change are unprecedented, and biological responses to these changes have also been prominent in all levels of species, communities and ecosystems. Aquatic-terrestrial ecotones are vulnerable to climate change, and degradation of the emergent aquatic macrophyte zone would have contributed severe ecological consequences for freshwater, wetland and terrestrial ecosystems. Most researches on climate change effects on biodiversity are contemplating on the terrestrial realm, and considerable changes in terrestrial biodiversity and species' distributions have been detected in response to climate change. This is unfortunate, given the importance of aquatic systems for providing ecosystem goods and services. Thus, if researchers were able to identify early-warning indicators of anthropogenic environmental changes on aquatic species, communities and ecosystems, it would certainly help to manage and conserve these systems in a sustainable way. One of such early-warning indicators concerns the expansion of emergent macrophytes in aquatic-terrestrial ecotones. Hence, this review highlights the impact of climatic changes towards aquatic macrophytes and their possible environmental implications.

  1. Significant Scales in Community Structure

    CERN Document Server

    Traag, V A; Van Dooren, P

    2013-01-01

    Many complex networks show signs of modular structure, uncovered by community detection. Although many methods succeed in revealing various partitions, it remains difficult to detect at what scale some partition is significant. This problem shows foremost in multi-resolution methods. We here introduce an efficient method for scanning for resolutions in one such method. Additionally, we introduce the notion of "significance" of a partition, based on subgraph probabilities. Significance is independent of the exact method used, so could also be applied in other methods, and can be interpreted as the gain in encoding a graph by making use of a partition. Using significance, we can determine "good" resolution parameters, which we demonstrate on benchmark networks. Moreover, optimizing significance itself also shows excellent performance. We demonstrate our method on voting data from the European Parliament. Our analysis suggests the European Parliament has become increasingly ideologically divided and that nationa...

  2. The role of emergent vegetation in structuring aquatic insect communities in peatland drainage ditches

    NARCIS (Netherlands)

    Whatley, M.H.; van Loon, E.E.; Vonk, J.A.; van der Geest, H.G.; Admiraal, W.

    2014-01-01

    Availability of macrophyte habitat is recognized as an important driver of aquatic insect communities in peatland drainage ditches; however, eutrophication can lead to the decline of submerged vegetation. While emergent vegetation is able to persist in eutrophicated ditches, vegetation removal, carr

  3. Identifying Community Structures in Dynamic Networks

    CERN Document Server

    Alvari, Hamidreza; Sukthankar, Gita; Lakkaraju, Kiran

    2016-01-01

    Most real-world social networks are inherently dynamic, composed of communities that are constantly changing in membership. To track these evolving communities, we need dynamic community detection techniques. This article evaluates the performance of a set of game theoretic approaches for identifying communities in dynamic networks. Our method, D-GT (Dynamic Game Theoretic community detection), models each network node as a rational agent who periodically plays a community membership game with its neighbors. During game play, nodes seek to maximize their local utility by joining or leaving the communities of network neighbors. The community structure emerges after the game reaches a Nash equilibrium. Compared to the benchmark community detection methods, D-GT more accurately predicts the number of communities and finds community assignments with a higher normalized mutual information, while retaining a good modularity.

  4. PIXE analysis of chromium phytoaccumulation by the aquatic macrophytes Eicchornia crassipes

    Science.gov (United States)

    Espinoza-Quiñones, F. R.; Rizzutto, M. A.; Added, N.; Tabacniks, M. H.; Módenes, A. N.; Palácio, S. M.; Silva, E. A.; Rossi, F. L.; Martin, N.; Szymanski, N.

    2009-04-01

    The uptake of hexavalent chromium in free living floating aquatic macrophytes Eicchornia crassipes cultivated in non-toxic chromium-doped hydroponic solutions is presented. A Cr-uptake bioaccumulation experiment was carried out using healthy macrophytes grown in a temperature controlled greenhouse. Six samples of nutrient media and plants were collected during the 23 day experiment. Roots and leaves were acid digested with the addition of an internal Gallium standard, for thin film sample preparation and quantitative Cr analysis by PIXE method. The Cr 6+ mass uptake by the macrophytes reached up to 70% of the initial concentration, comparable to former results and literature data. The Cr-uptake data were described using a non-structural first order kinetic model. Due to low cost and high removal efficiency, living aquatic macrophytes E. crassipes are a viable biosorbent in an artificial wetland of a water effluent treatment plant.

  5. PIXE analysis of chromium phytoaccumulation by the aquatic macrophytes Eicchornia crassipes

    Energy Technology Data Exchange (ETDEWEB)

    Espinoza-Quinones, F.R. [Department of Chemical Engineering - Postgraduate Program - NBQ, West Parana State University, Rua da Faculdade, 645, Jardim Santa Maria, 85903-000 Toledo, Parana (Brazil)], E-mail: f.espinoza@terra.com.br; Rizzutto, M.A.; Added, N.; Tabacniks, M.H. [Physics Institute, University of Sao Paulo, Rua do Matao s/n, Travessa R 187, 05508-900 Sao Paulo, SP (Brazil); Modenes, A.N.; Palacio, S.M.; Silva, E.A.; Rossi, F.L.; Martin, N.; Szymanski, N. [Department of Chemical Engineering - Postgraduate Program - NBQ, West Parana State University, Rua da Faculdade, 645, Jardim Santa Maria, 85903-000 Toledo, Parana (Brazil)

    2009-04-15

    The uptake of hexavalent chromium in free living floating aquatic macrophytes Eicchornia crassipes cultivated in non-toxic chromium-doped hydroponic solutions is presented. A Cr-uptake bioaccumulation experiment was carried out using healthy macrophytes grown in a temperature controlled greenhouse. Six samples of nutrient media and plants were collected during the 23 day experiment. Roots and leaves were acid digested with the addition of an internal Gallium standard, for thin film sample preparation and quantitative Cr analysis by PIXE method. The Cr{sup 6+} mass uptake by the macrophytes reached up to 70% of the initial concentration, comparable to former results and literature data. The Cr-uptake data were described using a non-structural first order kinetic model. Due to low cost and high removal efficiency, living aquatic macrophytes E. crassipes are a viable biosorbent in an artificial wetland of a water effluent treatment plant.

  6. Macrophytes: Freshwater Forests of Lakes and Rivers.

    Science.gov (United States)

    McDermid, Karla J.; Naiman, Robert J.

    1983-01-01

    Physical, chemical, and biological effects on macrophytes (aquatic plants) on the freshwater ecosystem are discussed. Research questions and issues related to these organisms are also discussed, including adaptations for survival in a wet environment, ecological consequences of large-scale macrophyte eradication, seasonal changes in plant…

  7. Community detection in networks: Structural communities versus ground truth

    Science.gov (United States)

    Hric, Darko; Darst, Richard K.; Fortunato, Santo

    2014-12-01

    Algorithms to find communities in networks rely just on structural information and search for cohesive subsets of nodes. On the other hand, most scholars implicitly or explicitly assume that structural communities represent groups of nodes with similar (nontopological) properties or functions. This hypothesis could not be verified, so far, because of the lack of network datasets with information on the classification of the nodes. We show that traditional community detection methods fail to find the metadata groups in many large networks. Our results show that there is a marked separation between structural communities and metadata groups, in line with recent findings. That means that either our current modeling of community structure has to be substantially modified, or that metadata groups may not be recoverable from topology alone.

  8. Enhancing community detection by local structural information

    CERN Document Server

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

    2016-01-01

    Many real-world networks such as the 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 positive effect on community detection in the networks. Here, various local similarity measures are used to extract the local structural information and then are 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 to the improvement for the community detection methods, while the positive effect of the local similarity measures is closely related to the networks under study and the applied community detection methods.

  9. A preliminary evaluation of lake morphometric traits influence on the maximum growing depth of macrophytes

    Directory of Open Access Journals (Sweden)

    Mattia M. Azzella

    2014-03-01

    Full Text Available Underwater light regime is widely considered the principal determinant of aquatic plant depth distribution. The majority of previous studies dealing with macrophytes in lakes have singled out Secchi disk transparency (SD values as the key empirical proxy to explain the maximum depth of macrophyte colonization (Zc. Few studies have investigated the role played by lake morphometry in structuring macrophyte beds. Using a balanced dataset including 20 Italian lakes (10 shallow and 10 deep lakes, we analysed transparency and lake morphometric traits to investigate their possible effects on Zc. Our results demonstrate that lake area plays a significant role, and confirm a direct influence of SD values on Zc. Considering lakes with an equal degree of transparency, smaller lakes may yield a lower Zc than larger ones. Morphology has a great influence on lake ecological characteristics especially on water thermal conditions and mixing depth. Based on our data, we argue that the thermal stratification plays a non negligible role in explaining macrophytes zonation, due to its influence on macrophytes life cycles and phytoplankton vertical distribution. Therefore, the present data suggest the need to enhance and refine our knowledge about the relationship between aquatic plants distribution and lake thermal conditions to better model the response of macrophytes to climate change and eutrophication.

  10. The study of aquatic macrophytes in Neotropics: a scientometrical view of the main trends and gaps.

    Science.gov (United States)

    Padial, A A; Bini, L M; Thomaz, S M

    2008-11-01

    Aquatic macrophytes comprises a diverse group of organisms including angiosperms, ferns, mosses, liverworts and some macroalgae that occur in seasonally or permanently wet environments. Among other implications, aquatic macrophytes are highly productive and with an important structuring role on aquatic environments. Ecological studies involving aquatic plants substantially increased in the last years. However, a precise view of researches devoted to aquatic macrophytes in Neotropics is necessary to reach a reliable evaluation of the scientific production. In the current study, we performed a scientometrics analysis of the scientific production devoted to Neotropical macrophytes in an attempt to find the main trends and gaps of researches concerning this group. The publication devoted to macrophytes in Neotropics increased conspicuously in the last two decades. Brazil, Argentina, Mexico and Chile were the most productive among Neotropical countries. Our analyses showed that the studies dealt mostly with the influences of aquatic macrophytes on organisms and abiotic features. Studies with a predictive approach or aiming to test ecological hypothesis are scarce. In addition, researches aiming to describe unknown species are still necessary. This is essential to support conservation efforts and to subsidize further investigations testing ecological hypotheses.

  11. A macrophyte submodel for aquatic ecosystems

    Science.gov (United States)

    Collins, Carol Desormeau; Wlosinski, Joseph H.

    1989-01-01

    A macrophyte submodel has been incorporated and tested in CE-QUAL-R1, a one-dimensional, vertically averaged model of reservoir water quality. A quasi two-dimensional scheme was necessary to represent the spatial relationship of macrophytes in reservoirs adequately. The macrophyte processes modeled were photosynthesis, dark respiration, excretion and nonpredatory mortality. Process equations for photosynthesis as a function of light and temperature, and dark respiration as a function of temperature were tested using data from laboratory studies. The submodel was field tested, along with other components of CE-QUAL-R1, using data collected at Eau Galle Reservoir, WI, U.S.A.

  12. Simple relationships to predict attributes of fish assemblages in patches of submerged macrophytes

    Directory of Open Access Journals (Sweden)

    Fernando Mayer Pelicice

    Full Text Available Submerged macrophytes play an important role in structuring habitats and, therefore, in determining patterns of aquatic biodiversity. Because these plants are widespread in shallow areas of many Neotropical reservoirs, the present work investigated if variables related to habitat structure, measured in patches of submerged macrophytes (Egeria densa and E. najas, can be used to predict fish assemblage attributes (fish density and species richness. Based on patch characteristics at fine spatial extents (macrophyte patches within reservoir arms, we considered plant biomass, volume and proportional volume (i.e. percentage of macrophyte volume in the water column as potential predictors. Fish and macrophytes were sampled with a 1-m² throw trap in littoral habitats of Rosana Reservoir, Paranapanema River, and simple correlation analyses were performed. Fish richness and abundance were highly correlated with all variables (R = 0.53 to 0.90, a relationship consistently observed in all sites. When compared to biomass, plant volume and proportional volume did not yield stronger correlations. We observed stronger correlations when E. densa and E. najas patches were analyzed separately (mono-specificity, probably because particular effects of each macrophyte on habitat structuring were removed (e.g. unnoticed morphological differences or unknown effects on habitat quality. The high R values observed in all pairwise relationships are uncommon in ecological studies, highlighting the predictive potential of variables related to habitat structure. These results suggest that, at small spatial extents, macrophyte biomass may represent an interesting predictor of fish density and richness in reservoirs with extensive colonization of submerged plants.

  13. CHOICE OF MACROPHYTE SUBSTRATE IN THE USE OF DIATOMS AS INDICATORS OF POND WATER QUALITY ASSESSMENT: PRELIMINARY DATA ON THE CASE OF ALALAY POND (COCHABAMBA, BOLIVIA

    Directory of Open Access Journals (Sweden)

    Eduardo A. Morales

    2012-06-01

    Full Text Available Alalay Pond is a 230-hectare, shallow aquatic ecosystem within Cochabamba, the third largest city in Bolivia. With the aim to determine the suitability of epiphytic diatoms for water quality assessment in the pond and to choose a substrate that would hold a representative bioindicator epiphytic community, the macrophytes Schoenoplectus californicus subsp. tatora (Kunth T. Koyama, Typha dominguensis Pers., Myriophyllum verticillatum L. and Azolla filiculoides Lam. were selected and differences in diatom community composition and structure were tested. Diatoms were collected during four sampling campaigns in the March-September, 2011 period, from three stations contiguous to the pelagic zone and prepared for analysis using standard, internationally used protocols. In all, 27 samples were collected from which 28 taxa characteristic of eutrophic environments were identified and 17 others could not be assigned names from the literature. Although many of the species are shared among sampling sites, the epiphytic communities developing at each station were different in structure and composition. Although, there are marked temporal variations in community features on each of the macrophytes, Shannon-Wiener and Pielou indexes, as well as canonical correspondence analysis, showed no marked differences within a single campaign and station among the 4 macrophytes. Shifts in structure and composition are denoted less commonly by species replacement and more often by changes in percent relative abundance of dominant and rare species. Very few species are restricted to a station or seem to show strong preference for a particular substrate. Taking into account growth, structural and ecological characteristics, as well as some phenological features of the macrophytes, S. californicus subsp. tatora and T. dominguensis are the most suitable substrates for water quality assessments in the pond. As demonstrated by multivariate analyses, among-site and time

  14. Community Extraction in Multilayer Networks with Heterogeneous Community Structure

    CERN Document Server

    Wilson, James D; Bhamidi, Shankar; Nobel, Andrew B

    2016-01-01

    Multilayer networks are a useful way to capture and model multiple, binary relationships among a fixed group of objects. While community detection has proven to be a useful exploratory technique for the analysis of single-layer networks, the development of community detection methods for multilayer networks is still in its infancy. We propose and investigate a procedure, called Multilayer Extraction, that identifies densely connected vertex-layer sets in multilayer networks. Multilayer Extraction makes use of a significance based score that quantifies the connectivity of an observed vertex-layer set by comparison with a multilayer fixed degree random graph model. Unlike existing detection methods, Multilayer Extraction handles networks with heterogeneous layers where community structure may be different from layer to layer. The procedure is able to capture overlapping communities, and it identifies background vertex-layer pairs that do not belong to any community. We establish large-graph consistency of the v...

  15. Macrophytes of the Grlište reservoir (Serbia: Fifteen years after its establishment

    Directory of Open Access Journals (Sweden)

    Stanković Ž.

    2009-01-01

    Full Text Available A large number of macrophytes, often in dense populations, have developed on the Grlište Reservoir, Serbia over a period of 15 years. Fast development of vegetation is a consequence of anthropogenic impact in lake management. The methodology used in this research covered 100% of the water body, including all areas with or without aquatic plants. The results indicate that plant communities are still in the early phase of development. This leaves space for future development of competitor macrophyte species (Najas marina, Eleocharis palustris, Typha latifolia, Typha angustifolia, Phragmites australis, etc. capable of endangering stability of the lake, which will tend toward eutrophication.

  16. Integration of geographic information systems and logistic multiple regression for aquatic macrophyte modeling

    Energy Technology Data Exchange (ETDEWEB)

    Narumalani, S. [Nebraska Univ., Lincoln, NE (United States). Dept. of Geography; Jensen, J.R.; Althausen, J.D.; Burkhalter, S. [South Carolina Univ., Columbia, SC (United States). Dept. of Geography; Mackey, H.E. Jr. [Westinghouse Savannah River Co., Aiken, SC (United States)

    1994-06-01

    Since aquatic macrophytes have an important influence on the physical and chemical processes of an ecosystem while simultaneously affecting human activity, it is imperative that they be inventoried and managed wisely. However, mapping wetlands can be a major challenge because they are found in diverse geographic areas ranging from small tributary streams, to shrub or scrub and marsh communities, to open water lacustrian environments. In addition, the type and spatial distribution of wetlands can change dramatically from season to season, especially when nonpersistent species are present. This research, focuses on developing a model for predicting the future growth and distribution of aquatic macrophytes. This model will use a geographic information system (GIS) to analyze some of the biophysical variables that affect aquatic macrophyte growth and distribution. The data will provide scientists information on the future spatial growth and distribution of aquatic macrophytes. This study focuses on the Savannah River Site Par Pond (1,000 ha) and L Lake (400 ha) these are two cooling ponds that have received thermal effluent from nuclear reactor operations. Par Pond was constructed in 1958, and natural invasion of wetland has occurred over its 35-year history, with much of the shoreline having developed extensive beds of persistent and non-persistent aquatic macrophytes.

  17. Genetic and nutritional characterization of some macrophytes, inhabiting the Bardawil Lagoon, Sinai, Egypt

    Directory of Open Access Journals (Sweden)

    Hosam E. Elsaied

    2015-12-01

    Full Text Available The ecological and economical significances of macrophytes, inhabiting the Mediterranean Lagoon, Bardawil, northern Sinai, Egypt, are still ambiguous, due to lack of knowledge. This study focused on genetic and nutritional characterization of three dominant macrophyte species at Bardawil Lagoon. Genetic identifications were done through genomic DNA extraction, followed by PCR amplifications and sequencing of 18S rRNA genes of the studied species. Phylogenetic analyses indicated that two of the recorded species showed homologies with the seagrass species, Posidonia oceanica and Halophila ovalis, with nucleotide identities 94.5% and 96.8%, respectively. The third species showed a unique phylogenetic lineage, representing nucleotide identity average, 86.5%, among the brown seaweeds, Heterokontophyta. Nutritional analyses indicated that the recorded seaweed-like macrophyte had the highest recommended nutritional contents, crude protein, 24.67%, with a total amino acid composition of 6.64 g/100 g protein, and carbohydrate, 38.16%, besides a calorific value of 3.063 K cal/g, among the studied macrophytes. To the best of our knowledge, this is the first attempt to characterize macrophyte community in Bardawil Lagoon, using both genetic and biochemical approaches.

  18. Social significance of community structure: Statistical view

    CERN Document Server

    Li, Hui-Jia

    2015-01-01

    Community structure analysis is a powerful tool for social networks, which can simplify their topological and functional analysis considerably. However, since community detection methods have random factors and real social networks obtained from complex systems always contain error edges, evaluating the significance of community structure partitioned is an urgent and important question. In this paper, integrating the specific characteristics of real society, we present a novel framework analyzing the significance of social community specially. The dynamics of social interactions are modeled by identifying social leaders and corresponding hierarchical structures. Instead of a direct comparison with the average outcome of a random model, we compute the similarity of a given node with the leader by the number of common neighbors. To determine the membership vector, an efficient community detection algorithm is proposed based on the position of nodes and their corresponding leaders. Then, using log-likelihood sco...

  19. Matching Community Structure Across Online Social Networks

    CERN Document Server

    Li, Lin

    2016-01-01

    The discovery of community structure in networks is a problem of considerable interest in recent years. In online social networks, often times, users are simultaneously involved in multiple social media sites, some of which share common social relationships. It is of great interest to uncover a shared community structure across these networks. However, in reality, users typically identify themselves with different usernames across social media sites. This creates a great difficulty in detecting the community structure. In this paper, we explore several approaches for community detection across online social networks with limited knowledge of username alignment across the networks. We refer to the known alignment of usernames as seeds. We investigate strategies for seed selection and its impact on networks with a different fraction of overlapping vertices. The goal is to study the interplay between network topologies and seed selection strategies, and to understand how it affects the detected community structu...

  20. Temporary fragmentation of a marginal lake and its effects on zooplankton community structure and organization

    Directory of Open Access Journals (Sweden)

    R. Nadai

    Full Text Available A river lateral lake (Coqueiral Lake marginal to Paranapanema River in its mouth zone into Jurumirim Reservoir, São Paulo, Brazil presented fragmentation into four small isolated bodies of water during a prolonged drought period, disrupting the link with the river. The aim of this work was to compare the temporal modifications on zooplankton community structure (total abundance, species richness, and diversity in the four water bodies. Zooplankton samplings and abiotic factor measurements were made in two periods - during isolation phase of the lake in relation to river and after re-establishment of hydrologic connectivity. A concentration effect on zooplankton abundance was recorded with drought progression, but without significant modifications in species richness and diversity. When the river inundation pulse occurred, a reduction in total zooplankton density was observed due to the dilution effect and a significant increase in species richness and diversity was recorded. Lateral water influx from the river to the lacustrine environment acts as a temporary disturbance factor on the zooplankton community structure. Zooplankton species composition presented some modifications between the two periods. Zooplankton organism drift in water from the river to the lake, removal of individuals from the aquatic macrophytes, and eclosion of resting eggs from sediment are probable factors that can increase zooplankton species richness immediately after lateral pulse inundation with water by the river.

  1. Temporary fragmentation of a marginal lake and its effects on zooplankton community structure and organization.

    Science.gov (United States)

    Nadai, R; Henry, R

    2009-08-01

    A river lateral lake (Coqueiral Lake marginal to Paranapanema River in its mouth zone into Jurumirim Reservoir, São Paulo, Brazil) presented fragmentation into four small isolated bodies of water during a prolonged drought period, disrupting the link with the river. The aim of this work was to compare the temporal modifications on zooplankton community structure (total abundance, species richness, and diversity) in the four water bodies. Zooplankton samplings and abiotic factor measurements were made in two periods--during isolation phase of the lake in relation to river and after re-establishment of hydrologic connectivity. A concentration effect on zooplankton abundance was recorded with drought progression, but without significant modifications in species richness and diversity. When the river inundation pulse occurred, a reduction in total zooplankton density was observed due to the dilution effect and a significant increase in species richness and diversity was recorded. Lateral water influx from the river to the lacustrine environment acts as a temporary disturbance factor on the zooplankton community structure. Zooplankton species composition presented some modifications between the two periods. Zooplankton organism drift in water from the river to the lake, removal of individuals from the aquatic macrophytes, and eclosion of resting eggs from sediment are probable factors that can increase zooplankton species richness immediately after lateral pulse inundation with water by the river.

  2. Social significance of community structure: statistical view.

    Science.gov (United States)

    Li, Hui-Jia; Daniels, Jasmine J

    2015-01-01

    Community structure analysis is a powerful tool for social networks that can simplify their topological and functional analysis considerably. However, since community detection methods have random factors and real social networks obtained from complex systems always contain error edges, evaluating the significance of a partitioned community structure is an urgent and important question. In this paper, integrating the specific characteristics of real society, we present a framework to analyze the significance of a social community. The dynamics of social interactions are modeled by identifying social leaders and corresponding hierarchical structures. Instead of a direct comparison with the average outcome of a random model, we compute the similarity of a given node with the leader by the number of common neighbors. To determine the membership vector, an efficient community detection algorithm is proposed based on the position of the nodes and their corresponding leaders. Then, using a log-likelihood score, the tightness of the community can be derived. Based on the distribution of community tightness, we establish a connection between p-value theory and network analysis, and then we obtain a significance measure of statistical form . Finally, the framework is applied to both benchmark networks and real social networks. Experimental results show that our work can be used in many fields, such as determining the optimal number of communities, analyzing the social significance of a given community, comparing the performance among various algorithms, etc.

  3. Social significance of community structure: Statistical view

    Science.gov (United States)

    Li, Hui-Jia; Daniels, Jasmine J.

    2015-01-01

    Community structure analysis is a powerful tool for social networks that can simplify their topological and functional analysis considerably. However, since community detection methods have random factors and real social networks obtained from complex systems always contain error edges, evaluating the significance of a partitioned community structure is an urgent and important question. In this paper, integrating the specific characteristics of real society, we present a framework to analyze the significance of a social community. The dynamics of social interactions are modeled by identifying social leaders and corresponding hierarchical structures. Instead of a direct comparison with the average outcome of a random model, we compute the similarity of a given node with the leader by the number of common neighbors. To determine the membership vector, an efficient community detection algorithm is proposed based on the position of the nodes and their corresponding leaders. Then, using a log-likelihood score, the tightness of the community can be derived. Based on the distribution of community tightness, we establish a connection between p -value theory and network analysis, and then we obtain a significance measure of statistical form . Finally, the framework is applied to both benchmark networks and real social networks. Experimental results show that our work can be used in many fields, such as determining the optimal number of communities, analyzing the social significance of a given community, comparing the performance among various algorithms, etc.

  4. Ammonia-oxidizing Bacteria and Archaea in the Rhizosphere of Freshwater Macrophytes

    DEFF Research Database (Denmark)

    Herrmann, Martina; Schramm, Andreas

    2007-01-01

    measurements revealed clear differences in ammonia oxidation rates. The diversity of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) was assessed using the ammonia monooxygenase (amoA) gene as functional marker. Both AOA and AOB could be detected in the rhizosphere of all three plant......AMMONIA-OXIDIZING ARCHAEA AND BACTERIA IN THE RHIZOSPHERE OF FRESHWATER MACROPHYTES Martina Herrmann and Andreas Schramm Department of Biological Sciences, Microbiology, University of Aarhus, Denmark Aquatic macrophytes such as Littorella uniflora and Lobelia dortmanna release oxygen from......-specific microbial community distinct from that of unvegetated sediment and (ii) that aquatic macrophytes have an impact on abundance and activity of nitrifying and denitrifying bacteria in freshwater sediment. The goal of this study was to test these hypotheses for the key functional group for coupled nitrification...

  5. Deciphering network community structure by surprise

    National Research Council Canada - National Science Library

    Aldecoa, Rodrigo; Marín, Ignacio

    2011-01-01

    .... A fundamental, unsolved problem is how to characterize the community structure of a network. Here, using both standard and novel benchmarks, we show that maximization of a simple global parameter, which we call Surprise...

  6. Matching Community Structure Across Online Social Networks

    OpenAIRE

    Lin LI; Campbell, W. M.

    2016-01-01

    The discovery of community structure in networks is a problem of considerable interest in recent years. In online social networks, often times, users are simultaneously involved in multiple social media sites, some of which share common social relationships. It is of great interest to uncover a shared community structure across these networks. However, in reality, users typically identify themselves with different usernames across social media sites. This creates a great difficulty in detecti...

  7. Understanding Microbial Communities: Function, Structure and Dynamics

    Science.gov (United States)

    2015-02-11

    microbial communities: Function, structure and dynamics’, at the Isaac Newton Institute, University of Cambridge, United Kingdom, from August to...dynamics’, at the Isaac Newton Institute, University of Cambridge, United Kingdom, from August to December 2014. The programme involved over 150...Communities: Function, Structure and Dynamics’, at the Isaac Newton Institute, Cambridge University, UK, from 19th August 2014 – 19th December 2014

  8. Efficiency and mechanism of the phytoremediation of decabromodiphenyl ether-contaminated sediments by aquatic macrophyte Scirpus validus.

    Science.gov (United States)

    Zhao, Liangyuan; Jiang, Jinhui; Chen, Chuanhong; Zhan, Shuie; Yang, Jiaoyan; Yang, Shao

    2017-05-01

    Phytoremediation is an economic and promising technique for removing toxic pollutants from the environment. Freshwater sediments are regarded as the ultimate sink of the widely used PBDE congener decabromodiphenyl ether (BDE-209) in the environment. In the study, the aquatic macrophyte Scirpus validus was selected to remove BDE-209 from three types of sediments (silt, clay, and sand) at an environmentally relevant concentration. After 18 months of phytoremediation experiment, S. validus significantly enhanced the dissipation rates of BDE-209 in all the sediments compared to the controls. Average removal rates of BDE-209 in the three treatments of silt, clay, and sandy sediments with S. validus were respectively 92.84, 84.04, and 72.22%, which were 148, 197, and 233% higher than that in the control sediments without S. validus. In the phytoremediation process, the macrophyte-rhizosphere microbe combined degradation was the main pathway of BDE-209 removal. Sixteen lower brominated PBDE congeners (di- to nona-) were detected in the sediments and plant tissues, confirming metabolic debromination of BDE-209 in S. validus. A relatively higher proportion of penta- and di-BDE congeners among the metabolites in plant tissues than that in the sediments indicated further debromination of PBDEs within plants. The populations and activities of microorganisms in the sediments were greatly promoted by S. validus. Bacterial community structure in BDE-209-contaminated rhizosphere sediments was different from that in the control rhizosphere sediment, as indicated by the dominant proportions of β-proteobacteria, δ-proteobacteria, α-proteobacteria, Acidobacteria, and Chloroflexi in the microbial flora. All these results suggested that S. validus was effective in phytoremediation of BDE-209 by the macrophyte-rhizosphere microbe combined degradation in aquatic sediments.

  9. Macrophytes: ecosystem engineers in UK urban rivers

    Science.gov (United States)

    Gibbs, H.; Gurnell, A.; Heppell, K.; Spencer, K.

    2012-04-01

    Macrophytes act as ecosystem engineers within river channels in that they have the ability to cause geomorphological and ecological change. They induce reductions in flow velocity and associated sediment accumulation, and their system of underground roots and rhizomes also reinforces the accumulated sediment reducing sediment erosion and resuspension and creating habitats. As sediments, particularly finer-grained, store contaminants including metals, this engineering means that in the specific context of urban rivers where sediments are more likely to be contaminated, macrophytes trap and hold contaminated sediments creating a potentially important sink of metals. However, depending on the ability for the macrophyte to reinforce the sediment and reduce erosion and resuspension, there is the potential for the sink to turn in to a source and metals to be released in to the overlying water. This research therefore looks at the ecosystem engineering ability of common macrophytes in UK urban rivers by looking at: (i) the effect upon flow velocity and sediment accumulation of Sparganium erectum (branched bur-reed); (ii) the sediment reinforcement ability of both S. erectum, Typha latifolia (bulrush) and Phalaris arundinacea (reed canary grass); and, (iii) the storage of metals within the sediment, overlying water and the macrophytes. Research was undertaken on the River Blackwater, an urban river in Surrey, UK which has extensive macrophyte growth. Flow velocity measurements and fine sediment depths were recorded both within and outside of dense stands of S. erectum. The uprooting resistance (as an indicator of sediment reinforcement) was measured for three species: S. erectum, T. latifolia and P. arundinacea. Additionally, some preliminary sampling was undertaken of the sediment, overlying water and the macrophytes to determine metal storage. Lower flow velocities and greater volumes of fine sediment were recorded within the stands of S. erectum as opposed to the

  10. Structure and spatial patterns of macrobenthic community in Tai Lake, a large shallow lake, China

    Science.gov (United States)

    Di Li,; Erickson, Richard A.; Song Tang,; Xuwen Li,; Zhichun Niu,; Xia Wang,; Hongling Liu,; Hongxia Yu,

    2016-01-01

    Tai Lake (Chinese: Taihu), the third-largest freshwater lake in China, suffers from harmful cyanobacteria blooms that are caused by economic development and population growth near the lake. Several studies have focused on phytoplankton in Tai Lake after a drinking water crisis in 2007; however, these studies primarily focused on microcystin bioaccumulation and toxicity to individual species without examining the effects of microcystin on macrobenthic community diversity. In this study, we conducted a survey of the lake to examine the effects of microcystine and other pollutants on marcobenthic community diversity. A totally of forty-nine species of macroinvertebrates were found in Tai Lake. Limnodrilus hoffmeisteri and Corbicula fluminea were the most abundant species. Cluster-analysis and one-way analysis of similarity (ANOSIM) identified three significantly different macrobenthic communities among the sample sites. More specifically, sites in the eastern bays, where aquatic macrophytes were abundant, had the highest diversity of macrobenthic communities, which were dominated by Bellamya aeruginosa, Bellamya purificata, L. hoffmeisteri, and Alocinma longicornis. Sites in Zhushan Bay contained relatively diverse communities, mainly composed of L. hoffmeisteri, C. fluminea, L. claparederanus, R. sinicus, and Cythura sp. Sites in the western region, Meiliang Bay and Wuli Bay had the lowest diversity, mainly composed ofL. hoffmeisteri, C. fluminea, Branchiura sowerbyi, and Rhyacodrilus sinicus. In addition, the relationships between macrobenthic metrics (Shannon–Wiener, Margalef, and Pielou) and environmental variables showed that community structure and spatial patterns of macrobenthos in Tai Lake were significantly influenced by chemical oxygen demand (CODCr), biochemical oxygen demand (BOD5), lead (Pb), and microcystin-LR (L for leucine and R for arginine). Our findings provide critical information that could help managers and policymakers

  11. Hierarchical community structure in complex (social) networks

    CERN Document Server

    Massaro, Emanuele

    2014-01-01

    The investigation of community structure in networks is a task of great importance in many disciplines, namely physics, sociology, biology and computer science where systems are often represented as graphs. One of the challenges is to find local communities from a local viewpoint in a graph without global information in order to reproduce the subjective hierarchical vision for each vertex. In this paper we present the improvement of an information dynamics algorithm in which the label propagation of nodes is based on the Markovian flow of information in the network under cognitive-inspired constraints \\cite{Massaro2012}. In this framework we have introduced two more complex heuristics that allow the algorithm to detect the multi-resolution hierarchical community structure of networks from a source vertex or communities adopting fixed values of model's parameters. Experimental results show that the proposed methods are efficient and well-behaved in both real-world and synthetic networks.

  12. Discovering Network Structure Beyond Communities

    OpenAIRE

    Nishikawa, Takashi; Adilson E Motter

    2011-01-01

    To understand the formation, evolution, and function of complex systems, it is crucial to understand the internal organization of their interaction networks. Partly due to the impossibility of visualizing large complex networks, resolving network structure remains a challenging problem. Here we overcome this difficulty by combining the visual pattern recognition ability of humans with the high processing speed of computers to develop an exploratory method for discovering groups of nodes chara...

  13. Response of littoral macrophytes to water level fluctuations in a storage reservoir

    Directory of Open Access Journals (Sweden)

    Krolová M.

    2013-05-01

    Full Text Available Lakes and reservoirs that are used for water supply and/or flow regulations have usually poorly developed littoral macrophyte communities, which impairs ecological potential in terms of the EU Water Framework Directive. The aim of our study was to reveal controlling factors for the growth of littoral macrophytes in a storage reservoir with fluctuating water level (Lipno Reservoir, Czech Republic. Macrophytes occurred in this reservoir only in the eulittoral zone i.e., the shoreline region between the highest and the lowest seasonal water levels. Three eulittoral sub-zones could be distinguished: the upper eulittoral with a stable community of perennial species with high cover, the middle eulittoral with relatively high richness of emergent and amphibious species present at low cover values, and the lower eulittoral devoid of permanent vegetation. Cover and species composition in particular sub-zones were primarily influenced by the duration and timing of flooding, followed by nutrient limitation and strongly reducing conditions in the flooded organic sediment. Our results stress the ecological importance of eulittoral zone in reservoirs with fluctuating water levels where macrophyte growth can be supported by targeted management of water level, thus helping reservoir managers in improving the ecological potential of this type of water bodies.

  14. Characterization of submerged macrophytes in a shallow lake using a combined approach of hyperspectral and LiDAR data

    Science.gov (United States)

    Valentini, E.; Bresciani, M.; Giardino, C.; Innocenti, C.; Taramelli, A.

    2009-12-01

    Aquatic vegetation is an important component of wetland ecosystems because of the key role in ecological functions of these environments. In the case of shallow lakes, such as the Trasimeno (central Italy), suspended sediment particles, frequently water level variation and algal bloom can lead to the reduction of underwater light penetration with feedback effect on submerged plants that sometimes drastically retreat. Macrophytes are an essential part of the productive zone in the Trasimeno lake and, by an equilibrium with algal growth, they contribute to the uptake of nutrients and pollutants, favour bottom quality, composition and stability and provide structural, food, shelter and breeding habitats for aquatic communities. The presence, abundance and species composition often represent a good limnological indicator of quality status of wetland areas. This study is a contribution on the knowledge of macrophytes of shallow lakes using a combined approach of airborne sensors such as MIVIS (Multi-spectral IR and Visible Imaging Spectrometer) and LiDAR (Light Detection and Ranging). The primary requirements for this ecosystem analysis are spatial and spectral resolution, accurate calibration and a suitable temporal baseline. Spectral Mixture Analysis (SMA) classifies individual mixed pixels according to the distribution of spectrally pure endmember fractions and provides a tool for discrimination and classification of wetlands areas. Physical and biological compositions are the primary determinants of the inherent reflectance properties at a landscape scale. We use SMA to discriminate among different types of reflectance properties on the basis of endmember fraction distributions. An in depth field validation has been also performed during the airborne survey that was on the 12 may 2009 and a spectral library of macrophytes has been collected. Field observations are necessary to calibrate and validate the spectral mixture model and subsequent thematic classification

  15. 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

  16. Shifting Niches for Community Structure Detection

    DEFF Research Database (Denmark)

    Grappiolo, Corrado; Togelius, Julian; Yannakakis, Georgios N.

    2013-01-01

    in complete networks, this approach seems to scale badly due to solutions with the wrong number of communities dominating the population. The new algorithm is based on a niching model, where separate compartments of the population contain candidate solutions with different numbers of communities. We......We present a new evolutionary algorithm for com- munity structure detection in both undirected and unweighted (sparse) graphs and fully connected weighted digraphs (complete networks). Previous investigations have found that, although evolutionary computation can identify community structure...... experimentally compare the new algorithm to the well-known algorithms of Pizzuti and Tasgin, and find that we outperform those algorithms for sparse graphs under some conditions, and drastically outperform them on complete networks under all tested conditions....

  17. Emergent Community Structure in Social Tagging Systems

    CERN Document Server

    Cattuto, Ciro; Servedio, Vito D P; Loreto, Vittorio

    2008-01-01

    A distributed classification paradigm known as collaborative tagging has been widely adopted in new Web applications designed to manage and share online resources. Users of these applications organize resources (Web pages, digital photographs, academic papers) by associating with them freely chosen text labels, or tags. Here we leverage the social aspects of collaborative tagging and introduce a notion of resource distance based on the collective tagging activity of users. We collect data from a popular system and perform experiments showing that our definition of distance can be used to build a weighted network of resources with a detectable community structure. We show that this community structure clearly exposes the semantic relations among resources. The communities of resources that we observe are a genuinely emergent feature, resulting from the uncoordinated activity of a large number of users, and their detection paves the way for mapping emergent semantics in social tagging systems.

  18. 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.

  19. Determinants of the detrital arthropod community structure

    DEFF Research Database (Denmark)

    Lessard, J.P.; Sackett, Tara E.; Reynolds, William N.;

    2011-01-01

    Understanding the factors that shape community structure, and whether those factors vary geographically, has a long history in ecology. Because the abiotic environment often varies in predictable ways along elevational gradients, montane systems are ideal to study geographic variation in the dete......Understanding the factors that shape community structure, and whether those factors vary geographically, has a long history in ecology. Because the abiotic environment often varies in predictable ways along elevational gradients, montane systems are ideal to study geographic variation...... in the determinants of community structure. In this study, we first examined the relative importance of environmental gradients, microclimate, and food resources in driving spatial variation in the structure of detrital communities in forests of the southeastern USA. Then, in order to assess whether the determinants...... for the effect of climatic variation along the elevational gradient, food resource addition and microclimate alteration influenced the richness and abundance of some taxa. However, the effect of food resource addition and microclimate alteration on the richness and abundance of arthropods did not vary...

  20. Modelling community structure in freshwater ecosystems

    NARCIS (Netherlands)

    Lek, S.; Scardi, M.; Verdonschot, P.F.M.; Descy, J.P.; Park, Y.S.

    2005-01-01

    The book presents approaches and methodologies for predicting the structure and diversity of key aquatic communities (namely diatoms, benthic macroinvertebrates and fish), under natural conditions and under man-made disturbance. Such an approach will make it possible to: 1) set up procedures for

  1. School, Community Leadership, and Election Structure

    Science.gov (United States)

    Allen, Ann

    2008-01-01

    This article examines how the political structure of school elections contributes to leadership perspectives related to school-community engagement. Interview data from school superintendents, school board presidents, and city mayors across four cities and two election types were analyzed to determine if differences in school election structure…

  2. Diversity and biomass of native macrophytes are negatively related to dominance of an invasive Poaceae in Brazilian sub-tropical streams

    OpenAIRE

    Luiz Felipe Gonçalves Fernandes; Mariana Carolina Teixeira; Sidinei Magela Thomaz

    2013-01-01

    Besides exacerbated exploitation, pollution, flow alteration and habitats degradation, freshwater biodiversity is also threatened by biological invasions. This paper addresses how native aquatic macrophyte communities are affected by the non-native species Urochloa arrecta, a current successful invader in Brazilian freshwater systems. We compared the native macrophytes colonizing patches dominated and non-dominated by this invader species. We surveyed eight streams in Northwest Paraná State (...

  3. Diversity and biomass of native macrophytes are negatively related to dominance of an invasive Poaceae in Brazilian sub-tropical streams

    OpenAIRE

    Luiz Felipe Gonçalves Fernandes; Mariana Carolina Teixeira; Sidinei Magela Thomaz

    2013-01-01

    Besides exacerbated exploitation, pollution, flow alteration and habitats degradation, freshwater biodiversity is also threatened by biological invasions. This paper addresses how native aquatic macrophyte communities are affected by the non-native species Urochloa arrecta, a current successful invader in Brazilian freshwater systems. We compared the native macrophytes colonizing patches dominated and non-dominated by this invader species. We surveyed eight streams in Northwest Paraná State (...

  4. How to Measure Significance of Community Structure in Complex Networks

    CERN Document Server

    Hu, Yanqing; Fan, Ying; Di, Zengru

    2010-01-01

    Community structure analysis is a powerful tool for complex networks, which can simplify their functional analysis considerably. Recently, many approaches were proposed to community structure detection, but few works were focused on the significance of community structure. Since real networks obtained from complex systems always contain error links, and most of the community detection algorithms have random factors, evaluate the significance of community structure is important and urgent. In this paper, we use the eigenvectors' stability to characterize the significance of community structures. By employing the eigenvalues of Laplacian matrix of a given network, we can evaluate the significance of its community structure and obtain the optimal number of communities, which are always hard for community detection algorithms. We apply our method to many real networks. We find that significant community structures exist in many social networks and C.elegans neural network, and that less significant community stru...

  5. Trophic structure and diversity in rocky intertidal upwelling ecosystems: A comparison of community patterns across California, Chile, South Africa and New Zealand

    Science.gov (United States)

    Blanchette, C. A.; Wieters, E. A.; Broitman, B. R.; Kinlan, B. P.; Schiel, D. R.

    2009-12-01

    The Benguela, California, and Humboldt represent three of the major eastern boundary upwelling ecosystems in the world. Upwelling ecosystems are highly productive, and this productivity forms the base of the food chain, potentially leading to ecosystems similar in trophic structure and diversity among upwelling regions. Here we compare the biological and trophic structure of rocky intertidal communities in each of these major upwelling regions. Our comparison includes a fourth region, New Zealand, which spans a similar latitudinal range, and experiences intermittent upwelling. The influence of oceanographic conditions on these communities was evaluated by using the long-term mean and standard deviation of satellite-based sea surface temperature (SST). Large differences emerged in the taxonomic richness in each of these systems, with California as the most and the Humboldt as the least taxonomically rich. Across all regions, richness tended to decrease progressively from lower trophic levels (macrophytes) to higher trophic levels (carnivores), and richness was inversely correlated with the proportion of variance in SST contained in the seasonal cycle, suggesting that strongly seasonal, predictable environments are relatively low in diversity. The functional and trophic structures were remarkably similar across these four regions of the world. Macrophytes were slightly dominant over filter-feeders in terms of space occupancy in all regions except the Benguela. Densities of herbivorous grazers were greatest in California and Benguela and far outnumbered carnivore densities in all regions. Despite some similarities, the overall structure of the communities from these regions differed significantly supporting the hypothesis that the biological and ecological consequences of similar physical forcing mechanisms (e.g. upwelling) are likely to be context-dependent.

  6. 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.

  7. A preferential attachment approach to community structure and the structure of communities

    CERN Document Server

    Young, Jean-Gabriel; Allard, Antoine; Dubé, Louis J

    2016-01-01

    We introduce an intuitive mechanism to describe both the emergence of community structure and the evolution of the internal structure of communities in social networks. Our idea is based on the simple assumption that each individual can, for every social group to which it belongs, develop connections and introduce new members. Complex behaviors emerge from opposing time scales for the activities of individuals and for the sum of individuals gathered in groups. We show how the resulting model reproduces behaviors observed in real social networks and in the anthropological theory known as Dunbar's number, i.e. the empirical observation of a maximal number of ties which an average individual can sustain within its social groups. Using this growth process, we organically reproduce the micro and mesoscopic structure of social networks. In so doing, we highlight two interesting properties of the community structure of social networks. First, strong correlations between the number of communities to which a node belo...

  8. Stochastic blockmodels and community structure in networks

    CERN Document Server

    Karrer, Brian

    2010-01-01

    Stochastic blockmodels have been proposed as a tool for detecting community structure in networks as well as for generating synthetic networks for use as benchmarks. Most blockmodels, however, ignore variation in vertex degree, making them unsuitable for applications to real-world networks, which typically display broad degree distributions that can significantly distort the results. Here we demonstrate how the generalization of blockmodels to incorporate this missing element leads to an improved objective function for community detection in complex networks. We also propose a heuristic algorithm for community detection using this objective function or its non-degree-corrected counterpart and show that the degree-corrected version dramatically outperforms the uncorrected one in both real-world and synthetic networks.

  9. Walk modularity and community structure in networks

    CERN Document Server

    Mehrle, David; Harkin, Anthony

    2014-01-01

    Modularity maximization has been one of the most widely used approaches in the last decade for discovering community structure in networks of practical interest in biology, computing, social science, statistical mechanics, and more. Modularity is a quality function that measures the difference between the number of edges found within clusters minus the number of edges one would statistically expect to find based on random chance. We present a natural generalization of modularity based on the difference between the actual and expected number of walks within clusters, which we call walk-modularity. Walk-modularity can be expressed in matrix form, and community detection can be performed by finding leading eigenvectors of the walk-modularity matrix. We demonstrate community detection on both synthetic and real-world networks and find that walk-modularity maximization returns significantly improved results compared to traditional modularity maximization.

  10. A cheating limit for structured communities

    Energy Technology Data Exchange (ETDEWEB)

    Perelson, Alan S [Los Alamos National Laboratory; Gerrish, Philip J [Los Alamos National Laboratory

    2008-01-01

    The constructive creativity of natural selection originates from its paradoxical ability to foster cooperation through competition. Cooperating communities ranging from complex societies to somatic tissue are constantly under attack, however, by non-cooperating mutants or transformants, called 'cheaters'. Structure in these communities promotes the formation of cooperating clusters whose competitive superiority can alone be sufficient to thwart outgrowths of cheaters and thereby maintain cooperation. But we find that when cheaters appear too frequently -- exceeding a threshold mutation or transformation rate -- their scattered outgrowths infiltrate and break up cooperating clusters, resulting in a cascading loss of community integrity, a switch to net positive selection for cheaters, and ultimately in the loss of cooperation. We find that this threshold mutation rate is directly proportional to the fitness support received from each cooperating neighbor minus the individual fitness benefit of cheating. When mutation rate also evolves, this threshold is crossed spontaneously after thousands of generations, at which point cheaters rapidly invade. In a structured community, cooperation can persist only if the mutation rate remains below a critical value.

  11. Regime shift from phytoplankton to macrophyte dominance in a large river: Top-down versus bottom-up effects

    Energy Technology Data Exchange (ETDEWEB)

    Ibanez, Carles, E-mail: carles.ibanez@irta.cat [IRTA Aquatic Ecosystems, Carretera Poble Nou, Km 5.5, 43540 St. Carles de la Rapita, Catalonia (Spain); Alcaraz, Carles; Caiola, Nuno; Rovira, Albert; Trobajo, Rosa [IRTA Aquatic Ecosystems, Carretera Poble Nou, Km 5.5, 43540 St. Carles de la Rapita, Catalonia (Spain); Alonso, Miguel [United Research Services S.L., Urgell 143, 08036 Barcelona, Catalonia (Spain); Duran, Concha [Confederacion Hidrografica del Ebro, Sagasta 24-26, 50071 Zaragoza, Aragon (Spain); Jimenez, Pere J. [Grup Natura Freixe, Major 56, 43750 Flix, Catalonia (Spain); Munne, Antoni [Agencia Catalana de l' Aigua, Provenca 204-208, 08036 Barcelona, Catalonia (Spain); Prat, Narcis [Departament d' Ecologia, Universitat de Barcelona, Diagonal 645, 08028 Barcelona Catalonia (Spain)

    2012-02-01

    The lower Ebro River (Catalonia, Spain) has recently undergone a regime shift from a phytoplankton-dominated to a macrophyte-dominated system. This shift is well known in shallow lakes but apparently it has never been documented in rivers. Two initial hypotheses to explain the collapse of the phytoplankton were considered: a) the diminution of nutrients (bottom-up); b) the filtering effect due to the colonization of the zebra mussel (top-down). Data on water quality, hydrology and biological communities (phytoplankton, macrophytes and zebra mussel) was obtained both from existing data sets and new surveys. Results clearly indicate that the decrease in phosphorus is the main cause of a dramatic decrease in chlorophyll and large increase in water transparency, triggering the subsequent colonization of macrophytes in the river bed. A Generalized Linear Model analysis showed that the decrease in dissolved phosphorus had a relative importance 14 times higher than the increase in zebra mussel density to explain the variation of total chlorophyll. We suggest that the described changes in the lower Ebro River can be considered a novel ecosystem shift. This shift is triggering remarkable changes in the biological communities beyond the decrease of phytoplankton and the proliferation of macrophytes, such as massive colonization of Simulidae (black fly) and other changes in the benthic invertebrate communities that are currently investigated. - Highlights: Black-Right-Pointing-Pointer We show a regime shift in a large river from phytoplankton to macrophyte dominance. Black-Right-Pointing-Pointer Two main hypotheses are considered: nutrient decrease and zebra mussel grazing. Black-Right-Pointing-Pointer Phosphorus depletion is found to be the main cause of the phytoplankton decline. Black-Right-Pointing-Pointer We conclude that oligotrophication triggered the colonization of macrophytes. Black-Right-Pointing-Pointer This new regime shift in a river is similar to that described

  12. Collective prediction based on community structure

    Science.gov (United States)

    Jiang, Yasong; Li, Taisong; Zhang, Yan; Yan, Yonghong

    2017-01-01

    Collective prediction algorithms have been used to improve performances when network structures are involved in prediction tasks. The training dataset of such tasks often contain information of content, links and labels, while the testing dataset have only content and link information. Conventional collective prediction algorithms conduct predictions based on the content of a node and the information of its direct neighbors with a base classifier. However, the information of some direct neighbor nodes may be not consistent with the target one. In addition, the information of indirect neighbors can be helpful when that of direct neighbors is scant. In this paper, instead of using information of direct neighbors, we propose to apply community structures in networks to prediction tasks. A community detection method is aggregated into the collective prediction process to improve prediction performance. Experimental results show that the proposed algorithm outperforms a number of standard prediction algorithms specially under conditions that labeled training dataset are limited.

  13. Contrasting patterns of free-living bacterioplankton diversity in macrophyte-dominated versus phytoplankton blooming regimes in Dianchi Lake, a shallow lake in China

    Science.gov (United States)

    Wang, Yujing; Li, Huabing; Xing, Peng; Wu, Qinglong

    2016-04-01

    Freshwater shallow lakes typically exhibit two alternative stable states under certain nutrient loadings: macrophyte-dominated and phytoplankton-dominated water regimes. An ecosystem regime shift from macrophytes to phytoplankton blooming typically reduces the number of species of invertebrates and fishes and results in the homogenization of communities in freshwater lakes. We investigated how microbial biodiversity has responded to a shift of the ecosystem regime in Dianchi Lake, which was previously fully covered with submerged macrophytes but currently harbors both ecological states. We observed marked divergence in the diversity and community composition of bacterioplankton between the two regimes. Although species richness, estimated as the number of operational taxonomic units and phylogenetic diversity (PD), was higher in the phytoplankton dominated ecosystem after this shift, the dissimilarity of bacterioplankton community across space decreased. This decrease in beta diversity was accompanied by loss of planktonic bacteria unique to the macrophyte-dominated ecosystem. Mantel tests between bacterioplankton community distances and Euclidian distance of environmental parameters indicated that this reduced bacterial community diff erentiation primarily reflected the loss of environmental niches, particularly in the macrophyte regime. The loss of this small-scale heterogeneity in bacterial communities should be considered when assessing long-term biodiversity changes in response to ecosystem regime conversions in freshwater lakes.

  14. Taxonomies of networks from community structure.

    Science.gov (United States)

    Onnela, Jukka-Pekka; Fenn, Daniel J; Reid, Stephen; Porter, Mason A; Mucha, Peter J; Fricker, Mark D; Jones, Nick S

    2012-09-01

    The study of networks has become a substantial interdisciplinary endeavor that encompasses myriad disciplines in the natural, social, and information sciences. Here we introduce a framework for constructing taxonomies of networks based on their structural similarities. These networks can arise from any of numerous sources: They can be empirical or synthetic, they can arise from multiple realizations of a single process (either empirical or synthetic), they can represent entirely different systems in different disciplines, etc. Because mesoscopic properties of networks are hypothesized to be important for network function, we base our comparisons on summaries of network community structures. Although we use a specific method for uncovering network communities, much of the introduced framework is independent of that choice. After introducing the framework, we apply it to construct a taxonomy for 746 networks and demonstrate that our approach usefully identifies similar networks. We also construct taxonomies within individual categories of networks, and we thereby expose nontrivial structure. For example, we create taxonomies for similarity networks constructed from both political voting data and financial data. We also construct network taxonomies to compare the social structures of 100 Facebook networks and the growth structures produced by different types of fungi.

  15. Taxonomies of networks from community structure

    Science.gov (United States)

    Onnela, Jukka-Pekka; Fenn, Daniel J.; Reid, Stephen; Porter, Mason A.; Mucha, Peter J.; Fricker, Mark D.; Jones, Nick S.

    2012-09-01

    The study of networks has become a substantial interdisciplinary endeavor that encompasses myriad disciplines in the natural, social, and information sciences. Here we introduce a framework for constructing taxonomies of networks based on their structural similarities. These networks can arise from any of numerous sources: They can be empirical or synthetic, they can arise from multiple realizations of a single process (either empirical or synthetic), they can represent entirely different systems in different disciplines, etc. Because mesoscopic properties of networks are hypothesized to be important for network function, we base our comparisons on summaries of network community structures. Although we use a specific method for uncovering network communities, much of the introduced framework is independent of that choice. After introducing the framework, we apply it to construct a taxonomy for 746 networks and demonstrate that our approach usefully identifies similar networks. We also construct taxonomies within individual categories of networks, and we thereby expose nontrivial structure. For example, we create taxonomies for similarity networks constructed from both political voting data and financial data. We also construct network taxonomies to compare the social structures of 100 Facebook networks and the growth structures produced by different types of fungi.

  16. Evaluation of a combined macrophyte-epiphyte bioassay for assessing nutrient enrichment in the Portneuf River, Idaho, USA.

    Science.gov (United States)

    Ray, Andrew M; Mebane, Christopher A; Raben, Flint; Irvine, Kathryn M; Marcarelli, Amy M

    2014-07-01

    We describe and evaluate a laboratory bioassay that uses Lemna minor L. and attached epiphytes to characterize the status of ambient and nutrient-enriched water from the Portneuf River, Idaho. Specifically, we measured morphological (number of fronds, longest surface axis, and root length) and population-level (number of plants and dry mass) responses of L. minor and community-level (ash-free dry mass [AFDM] and chlorophyll a [Chl a]) responses of epiphytes to nutrient enrichment. Overall, measures of macrophyte biomass and abundance increased with increasing concentrations of dissolved phosphorus (P) and responded more predictably to nutrient enrichment than morphological measures. Epiphyte AFDM and Chl a were also greatest in P-enriched water; enrichments of N alone produced no measurable epiphytic response. The epiphyte biomass response did not directly mirror macrophyte biomass responses, illustrating the value of a combined macrophyte-epiphyte assay to more fully evaluate nutrient management strategies. Finally, the most P-enriched waters not only supported greater standing stocks of macrophyte and epiphytes but also had significantly higher water column dissolved oxygen and dissolved organic carbon concentrations and a lower pH. Advantages of this macrophyte-epiphyte bioassay over more traditional single-species assays include the use of a more realistic level of biological organization, a relatively short assay schedule (~10 days), and the inclusion of multiple biological response and water-quality measures.

  17. Macrophytes of the Grlište reservoir (Serbia): Fifteen years after its establishment

    OpenAIRE

    Stanković Ž.; Borišev M.; Simić Slobodanka; Vučković Milijana; Igić Ružica; Vidović Milka; Miljanović B.

    2009-01-01

    A large number of macrophytes, often in dense populations, have developed on the Grlište Reservoir, Serbia over a period of 15 years. Fast development of vegetation is a consequence of anthropogenic impact in lake management. The methodology used in this research covered 100% of the water body, including all areas with or without aquatic plants. The results indicate that plant communities are still in the early phase of development. This leaves space for future development of competitor macro...

  18. A Social Network Model Exhibiting Tunable Overlapping Community Structure

    NARCIS (Netherlands)

    Liu, D.; Blenn, N.; Van Mieghem, P.F.A.

    2012-01-01

    Social networks, as well as many other real-world networks, exhibit overlapping community structure. In this paper, we present formulas which facilitate the computation for characterizing the overlapping community structure of networks. A hypergraph representation of networks with overlapping

  19. Epidemic spreading on complex networks with community structures

    CERN Document Server

    Stegehuis, Clara; van Leeuwaarden, Johan 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 and the vertex degrees. These models show that community structure is an important determinant of the behavior of percolation processes on networks, such as information diffusion or virus spreading: the community structure can both \\textit{enforce} as well as \\textit{inhibit} diffusion processes. Our models further show that it is the mesoscopic set of communities that matters. The exact internal structures of communities barely influence the behavior of percolation processes across networks. This insensitivity is likely due to the relative denseness of the communities.

  20. Bioprospecting of Marine Macrophytes Using MS-Based Lipidomics as a New Approach

    Directory of Open Access Journals (Sweden)

    Elisabete Maciel

    2016-03-01

    Full Text Available The marine environment supports a remarkable diversity of organisms which are a potential source of natural products with biological activities. These organisms include a wide variety of marine plants (from micro- to macrophytes, which have been used in the food and pharmaceutical industry. However, the biochemistry and biological activities of many of these macrophytes (namely macroalgae and halophytes, including seagrasses are still far from being fully explored. Most popular bioactive components include polysaccharides, peptides, phenolics and fatty acids (FAs. Polar lipids (glycolipids, phospholipids and betaine lipids are emerging as novel value-added bioactive phytochemicals, rich in n-3 FA, with high nutritional value and health beneficial effects for the prevention of chronic diseases. Polar lipids account various combinations of polar groups, fatty acyl chains and backbone structures. The polar lipidome of macrophytes is remarkably diverse, and its screening represents a significant analytical challenge. Modern research platforms, particularly mass spectrometry (MS-based lipidomic approaches, have been recently used to address this challenge and are here reviewed. The application of lipidomics to address lipid composition of marine macrophytes will contribute to the stimulation of further research on this group and foster the exploration of novel applications.

  1. Bioprospecting of Marine Macrophytes Using MS-Based Lipidomics as a New Approach.

    Science.gov (United States)

    Maciel, Elisabete; Costa Leal, Miguel; Lillebø, Ana Isabel; Domingues, Pedro; Domingues, Maria Rosário; Calado, Ricardo

    2016-03-08

    The marine environment supports a remarkable diversity of organisms which are a potential source of natural products with biological activities. These organisms include a wide variety of marine plants (from micro- to macrophytes), which have been used in the food and pharmaceutical industry. However, the biochemistry and biological activities of many of these macrophytes (namely macroalgae and halophytes, including seagrasses) are still far from being fully explored. Most popular bioactive components include polysaccharides, peptides, phenolics and fatty acids (FAs). Polar lipids (glycolipids, phospholipids and betaine lipids) are emerging as novel value-added bioactive phytochemicals, rich in n-3 FA, with high nutritional value and health beneficial effects for the prevention of chronic diseases. Polar lipids account various combinations of polar groups, fatty acyl chains and backbone structures. The polar lipidome of macrophytes is remarkably diverse, and its screening represents a significant analytical challenge. Modern research platforms, particularly mass spectrometry (MS)-based lipidomic approaches, have been recently used to address this challenge and are here reviewed. The application of lipidomics to address lipid composition of marine macrophytes will contribute to the stimulation of further research on this group and foster the exploration of novel applications.

  2. Hydroponic Uptake of Atrazine and Lambda-cyhalothrin in Aquatic Macrophytes

    Science.gov (United States)

    Bouldin, J. L.; Farris, J. L.; Moore, M. T.; Smith, S.; Cooper, C. M.

    2005-05-01

    Phytoremediation encompasses an array of plant-associated processes known to mitigate contaminants from soil, sediment, and water. Modification of pesticides associated with agricultural runoff includes processes directly associated with aquatic macrophytes in addition to soil geochemical modifications and associated rhizospheric degradation. Remediation attributes of two vegetative species common to agricultural drainages in the Mississippi Delta, USA, were assessed using atrazine and lambda-cyhalothrin. Concentrations used in 8-d hydroponic exposures were calculated using recommended field applications and a 5% runoff model from a 0.65-cm rainfall event on a 2.02-ha field. While greater atrazine uptake was measured in Juncus effusus, greater lambda-cyhalothrin uptake occurred in Ludwigia peploides. Maximum pesticide uptake was reached within 48 h for each exposure and subsequent translocation of pesticides to upper plant biomass occurred in macrophytes exposed to atrazine. Sequestration of 98.2% of lambda-cyhalothrin in roots of L. peploides was measured after 8 d. Translocation of lambda-cyhalothrin in J. effusus resulted in 25.4% of pesticide uptake partitioned to upper plant biomass. These individual macrophyte remediation studies measured species- and pesticide-specific uptake rates, indicating that the seasonality of pesticide applications and macrophyte emergence might interact strongly to enhance mitigation capabilities in edge-of-field conveyance structures.

  3. Assess the environmental health status of macrophyte ecosystems using an oxidative stress biomarker. Case studies: The Gulf of Aqaba and the Lagoon of Venice

    Science.gov (United States)

    Wahsha, Mohammad; Juhmani, Abdul-Salam; Buosi, Alessandro; Sfriso, Andrea; Sfriso, Adriano

    2017-04-01

    Macrophytes play a fundamental role in structuring communities in aquatic environments. They contribute to maintaining the ecosystem services. Unfortunately, nowadays, they are threatened by different sources of pollution. The release of such potentially toxic elements (PTEs) to the environment may influence negatively the ecosystem health, which often limits and sometimes disqualifies the ecosystem biodiversity. Indeed, the increasing concentration and distribution of PTEs in the marine ecosystem by mismanagement of industrial activities, overuse of agrochemicals, and waste disposal are causing worldwide concern. The aim of this work is to describe the developing of an innovative early warning tool, based on the implementation of the lipid peroxidation oxidative stress biomarker for the assessment and monitoring of ecological status in response to PTEs in different marine environments. Six sites were selected along the Jordanian coastline of the Gulf of Aqaba and the lagoon of Venice in Italy according to different morphological, ecological conditions and anthropogenic impact. Our results indicated that the effect of PTEs causes oxidative stress to macrophytes; in particular: Ulva fasciata and Ulva lactuca collected from the lagoon of Venice and Gulf of Aqaba respectively. The oxidative stress by PTEs alters the biochemical processes, as it stimulates the generation of reactive oxygen species (ROS) and accordingly the oxidative degradation of lipids (LPO). The by-products of LPO, the organic compound malondialdehyde (MDA) is significantly correlated (pphysical analysis has a limited environmental application. Thus, the implementation of MDA assay as an alternative diagnostic biomarker tool could be more effectively to recognize changes in the environment at an early stage. Keywords: Gulf of Aqaba, lagoon of Venice, macrophytes, lipid peroxidation.

  4. Community Structure in Congressional Cosponsorship Networks

    CERN Document Server

    Zhang, Yan; Traud, Amanda L; Porter, Mason A; Fowler, James H; Mucha, Peter J

    2007-01-01

    We study the United States Congress by constructing networks between Members of Congress based on the legislation that they cosponsor. Using the concept of modularity, we identify the community structure of Congressmen, as connected via sponsorship/cosponsorship of the same legislation, to investigate the collaborative communities of legislators in both chambers of Congress. This analysis yields an explicit and conceptually clear measure of political polarization, demonstrating a sharp increase in partisan polarization which preceded and then culminated in the 104th Congress (1995-1996), when Republicans took control of both chambers. Although polarization has since waned in the U.S. Senate, it remains at historically high levels in the House of Representatives.

  5. COMPOSTING AQUATIC MACROPHYTES: SALVINIA AURICULATA AND EICHHORNIA

    Directory of Open Access Journals (Sweden)

    Ana Kleiber Pessoa Borges

    2011-07-01

    Full Text Available High population growth and densities in urban areas and the consumerism present in modern societies have pronounced effect on the generation of organic waste, which may become an environmental problem. Aerobic composting is one of the best known alternatives to treating these wastes. This study aimed to evaluate the applicability of composting as an alternative to the disposal of organic wastes from aquatic macrophytes Eichhornia crassipes and Salvinia auriculata collected in the reservoir UHE Luis Eduardo Magalhães, Tocantins, Brazil and also produce an organic compound from different combinations of macrophytes, prunning residues and organic waste generated by the Campus of Palmas of UFT, TO. The study was conducted in an area of 80m² in unprotected environment at the experimental station of the Campus of Palmas. The experiments were done as three replications in the dry season (from 18.09.2008 to 11.21.2008 and rainy season (from 03.09.2009 to 05.04.2009 and the parameters temperature, pH, total nitrogen and carbon, and organic matter were monitored along with counts of microorganisms. It was possible to produce compost from the combinations of organic wastes within 65 days of composting during the dry season and 55 days in the rainy season. The aquatic macrophytes resulted in a good raw material for composting, since there is not a destination for the excess plant materials removed by the cleaning process of the reservoir.

  6. Review of alien marine macrophytes in Tunisia

    Directory of Open Access Journals (Sweden)

    Y. R. SGHAIER

    2014-06-01

    Full Text Available In the present study, the list of alien marine macrophytes introduced into Tunisia was updated in the light of available data and new observations. A total of 27 alien marine macrophytes have been recorded so far from Tunisia: 18 Rhodophyta, 3 Ochrophyta, 5 Chlorophyta and 1 Magnoliophyta. For each species, the locality (-ies, the year (or period and the source of the first observation in Tunisia are given. The distribution and the status (casual, cryptogenic, established or questionable of species in Tunisia were evaluated and, where appropriate, discussed. Among them, Hypnea cornuta is reported for the first time from Tunisia. Fourteen alien marine macrophytes are established, whereas seven cryptogenic and two casual species require further investigation. Eleven species are considered as invasive or potentially invasive in the Mediterranean Sea: Acrothamnion preissii, Asparagopsis armata, A. taxiformis Indo-Pacific lineage, Hypnea cornuta, Lophocladia lallemandii, Womersleyella setacea, Caulerpa chemnitzia, C. cylindracea, C. taxifolia, Codium fragile subsp. fragile and Halophila stipulacea. Finally, the case of four questionable species is also discussed.

  7. Aquatic macrophytes in natural and managed wetlands of Rio Grande do Sul State, Southern Brazil Macrófitas aquáticas em áreas úmidas naturais e manejadas do Rio Grande do Sul, sul do Brasil

    Directory of Open Access Journals (Sweden)

    Ana Silvia Rolon

    2010-06-01

    Full Text Available AIM: This study gathers the main results obtained from studies regarding dynamic of aquatic macrophyte community in natural and managed wetlands of Southern Brazil. We analyzed the aquatic macrophytes diversity in wetlands of Southern Brazil, the environmental factors that determine the structure of the aquatic macrophyte community in fragmented wetlands, the effects of floods on the dynamics of macrophytes, and the contributions to the rice field for the conservation of aquatic macrophytes; METHODS: The information was obtained from several researches carried in several spatial scales and different wetlands types over the last 10 years in Southern Brazil; RESULTS: The studies have reported the occurrence of approximately 250 species of aquatic macrophytes. Wetland area, habitat diversity, altitude and hydroperiod were determinant for macrophyte richness and composition in wetlands of Southern Brazil. Furthermore, flood events, long or short-term ones, are strongly associated to the structure of the aquatic macrophyte community. The rice field systems of Southern Brazil (crops and irrigation channel shelter a representative number of species of macrophyte found at natural wetlands in this region. The agricultural practices adopted over rice cultivation cycle in the rice fields have influenced the macrophyte richness and biomass. The different hydrological management practices adopted after the harvesting period (presence or lack of water surface did not influence the macrophyte richness and biomass, however it influenced the species composition; CONCLUSIONS: The increasing process of wetland degradation (e.g. fragmentation, flood control and rice field expansion presents a threat to the conservation aquatic macrophyte species.OBJETIVO: Este estudo reúne os principais resultados obtidos em trabalhos sobre a dinâmica da comunidade de macrófitas aquáticas em áreas úmidas naturais e manejadas do sul do Brasil. Nós analisamos a diversidade de

  8. Chemical, Physical, and Biological Factors Shape Littoral Invertebrate Community Structure in Coal-Mining End-Pit Lakes

    Science.gov (United States)

    Luek, Andreas; Rasmussen, Joseph B.

    2017-04-01

    Aquatic invertebrates form the base of the consumer food web in lakes. In coal-mining end-pit lakes, invertebrates are exposed to an environment with potentially challenging physical and chemical features. We hypothesized that the physical and chemical features of end-pit lakes reduce critical littoral habitat and thus reduce invertebrate diversity, thereby limiting the potential for these lakes to be naturalized. We used a multivariate approach using principle component analysis and redundancy analysis to study relationships between invertebrate community structure, habitat features, and water quality in five end-pit lakes and five natural lakes in the Rocky Mountain foothills of west-central Alberta, Canada. Results show a significantly different invertebrate community structure was present in end-pit lakes as compared with reference lakes in the same region, which could be accounted for by water hardness, conductivity, slope of the littoral zone, and phosphorus concentrations. Habitat diversity in end-pit lakes was also limited, cover provided by macrophytes was scarce, and basin slopes were significantly steeper in pit lakes. Although water chemistry is currently the strongest influencing factor on the invertebrate community, physical challenges of habitat homogeneity and steep slopes in the littoral zones were identified as major drivers of invertebrate community structure. The addition of floating wetlands to the littoral zone of existing pit lakes can add habitat complexity without the need for large-scale alterations to basing morphology, while impermeable capping of waste-rock and the inclusion of littoral habitat in the planning process of new pit lakes can improve the success of integrating new pit lakes into the landscape.

  9. Community structure in introductory physics course networks

    CERN Document Server

    Traxler, Adrienne L

    2015-01-01

    Student-to-student interactions are foundational to many active learning environments, but are most often studied using qualitative methods. Network analysis tools provide a quantitative complement to this picture, allowing researchers to describe the social interactions of whole classrooms as systems. Past results from introductory physics courses have suggested a sharp division in the formation of social structure between large lecture sections and small studio classroom environments. Extending those results, this study focuses on calculus-based introductory physics courses at a large public university with a heavily commuter and nontraditional student population. Community detection network methods are used to characterize pre- and post-course collaborative structure in several sections, and differences are considered between small and large classes. These results are compared with expectations from earlier findings, and comment on implications for instruction and further study.

  10. Information transfer in community structured multiplex networks

    CERN Document Server

    Solé-Ribalta, Albert; Gómez, Sergio; Arenas, Alex

    2015-01-01

    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 ...

  11. Study of aquatic macrophytes in the wetlands on the territory of Vrachanski Balkan nature park

    Directory of Open Access Journals (Sweden)

    Valčev Vladimir V.

    2010-01-01

    Full Text Available An overall study of the species composition and abundance of macrophytes in all open water bodies of a large protected territory was made for the first time in Bulgaria. Four high-mountain eutrophic lakes and the upper stretches of three rivers within the boundaries of Vrachanski Balkan Nature Park were investigated. Thirty-nine macrophyte species (higher plants and mosses were identified scattered around, or forming more or less distinct vegetation groups. Three of the lakes are new for the country locations of the species Elatine alsinastrum and Peplis portula. The processes of eutrophication are more advanced in the lakes. The habitats formed around the investigated water bodies have been determined. They are three habitats of European Community interest for Bulgaria. The major threats for the investigated wetlands on the territory of the Park are pointed out.

  12. Advances in ecological function and interaction mechanism of aquatic macrophyte-biofilm system%水生植物-生物膜体系的生态功能与互作机制研究进展

    Institute of Scientific and Technical Information of China (English)

    吕小央; 张松贺; 刘凯辉; 韩冰; 郭川

    2015-01-01

    水生植物是水生态系统的重要组成部分,是生物膜的天然载体,水生植被的恢复有利于提高水体生物膜面积。与非生物介质相比,水生植物与微生物间存在附着互作机制,一方面水生植物能为微生物提供附着场所和营养物质,其产生的化感物质对附着微生物的种类和数量有影响;另一方面,附着微生物也会对水生植物生长产生促进或遏制作用。另外,指出水流和水质对水生植物及生物膜的形成、结构以及群落组成产生重要影响;水生植物和生物膜作为一个复杂互作体系,是水体生态系统的基本单位,相关植物表面表面生物膜体系特征及其对水体中碳、氮等要素的转化及污染物的去除机制相关研究,将是今后水生态研究过程中的重点方向之一。%Being the key component of aquatic ecosystem , the aquatic macrophyte is a natural carrier of biofilm . The restoration of aquatic macrophyte contributes to the increase of water area of biofilm .Compared with the non-biological medium , there were a complex interaction mechanism between the aquatic macrophyte and the microbe . On one hand , aquatic macrophyte provide the attachment sites and nutrients for the microbe , and the allelochemicals emerged from the aquatic macrophyte have an effect on the types and quantity of attached microbe ;on the other hand , the attached microbe can promote or restrain the growth of aquatic macrophyte .Additionally , flow and water quality can have important effects on the formation , structure and the composition of community of aquatic macrophyte and biofilm . As a complex interaction system , aquatic macrophyte and biofilm is the fundamental unit of water ecosystem .The study on the characteristics of plant surface-surface biofilm system and its role on the transformation of carbon , nitrogen and other elements in water , and the pollutants removal mechanism should be one of the

  13. Fish assemblage dynamics in a Neotropical floodplain relative to aquatic macrophytes and the homogenizing effect of a flood pulse

    Science.gov (United States)

    Gomes, L.C.; Bulla, C. K.; Agostinho, A. A.; Vasconcelos, L. P.; Miranda, Leandro E.

    2012-01-01

    The presence of aquatic macrophytes is a key factor in the selection of habitats by fish in floodplain lakes because these plants enhance the physical and biological complexities of aquatic habitats. The seasonal flood pulse may influence this interaction, but there is no information in the literature about the effects that flood events may have on macrophytes assemblages and its associated effects on fish assemblages. Thus, this article aimed to investigate whether species richness, evenness and similarities in fish assemblage composition differed between littoral areas vegetated with macrophytes and unvegetated areas, before and after a flood. We sampled three lakes in the floodplain of the upper Paraná River basin. Sampling was conducted before (December 2004 and January 2005) and after (early March, late March and May 2005) a flood event. Overall, species richness and evenness were higher in macrophytes-covered areas. Before the flood, the composition of fish assemblages was distinct when comparing vegetated and unvegetated areas. After the flood, the similarity in fish assemblage composition was higher, indicating a homogenization effect of floods for fish inhabiting littoral areas of floodplain lakes. After the flood, opportunistic species dominated the fish assemblages in aquatic macrophytes, apparently restructuring assemblages in the littoral, restarting a succession process. Thus, the observed homogenization effect of the flood could minimize biological interactions and could induce fish assemblages to begin a new process of structurization.

  14. Richness and composition of macrophyte assemblages in four Amazonian lakes - doi: 10.4025/actascibiolsci.v35i3.11602

    Directory of Open Access Journals (Sweden)

    Sidinei Magela Thomaz

    2013-08-01

    Full Text Available Aquatic macrophytes are an important component in the structure of lakes in Neotropical floodplains, for example, because they support a high diversity of invertebrates and vertebrates. In this paper, we tested whether or not the variability of macrophyte assemblages is lower in spatially close quadrats than among quadrats of different lakes. The study was carried in four lakes in a large Amazonian floodplain (Purus river, where floating meadows were investigated. A total of 49 taxa of macrophytes were found. Five species dominated and three species were rare. Taxa richness, composition and beta diversity differed more between than within lakes. Because high beta diversity was found among the lakes, they should be considered individually important for maintaining the gamma diversity of macrophytes within the Purus River floodplain, and this should be considered in plans of lake management.  

  15. Classifying aquatic macrophytes as indicators of eutrophication in European lakes

    NARCIS (Netherlands)

    Penning, W.E.; Mjelde, M.; Dudley, B.; Hellsten, S.; Hanganu, J.; Kolada, A.; van den Berg, Marcel S.; Poikane, S.; Phillips, G.; Willby, N.; Ecke, F.

    2008-01-01

    Aquatic macrophytes are one of the biological quality elements in the Water Framework Directive (WFD) for which status assessments must be defined. We tested two methods to classify macrophyte species and their response to eutrophication pressure: one based on percentiles of occurrence along a phosp

  16. Salinity as a constraint on growth of oligohaline marsh macrophytes. II. Salt pulses and recovery potential

    Science.gov (United States)

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

    1999-01-01

    The ability of common oligohaline marsh macrophytes of the northern Gulf of Mexico coast to recover from pulses of increased salinity was investigated in a greenhouse experiment with Eleocharis palustris, Panicum hemitomon, Sagittaria lancifolia, and Scirpus americanus monocultures. Components of salinity pulses applied were final salinity reached (6 or 12 g/L), salinity influx rate (3 d or 3 wk), and duration of exposure (1, 2, or 3 mo). After each exposure period, we placed plants into freshwater until the end of the 120-d experiment to determine recovery potential. The four species varied in their ability to recover from the salinity pulses. Within a species, recovery varied with final salinity level and duration of exposure, and to a lesser extent with salinity influx rate. Scirpus americanus, growth of which was stimulated by salinity for 3 mo. Ability to recover decreased with increased salinity and increased duration of exposure for the remaining three species. Recovery of specific aspects of growth was also suppressed in these species by a rapid salinity influx rate compared to a slow influx rate. The complex variations in recovery patterns displayed by the different species may lead to changes in species dominance following the short-term salinity pulses that can occur during storm events, which in turn may affect marsh plant community composition and structure.

  17. Typology of State-Level Community College Governance Structures

    Science.gov (United States)

    Fletcher, Jeffrey A.; Friedel, Janice Nahra

    2017-01-01

    Despite having a well-documented history about community colleges across the United States, relatively few discussions have covered state-level governance structures. To understand the typology of state community college governance structures, it must first be recognized that community college governance is characterized as a complex web of…

  18. Permanence and Community Structure in Complex Networks

    CERN Document Server

    Chakraborty, Tanmoy; Ganguly, Niloy; Mukherjee, Animesh; Bhowmick, Sanjukta

    2016-01-01

    The goal of community detection algorithms is to identify densely-connected units within large networks. An implicit assumption is that all the constituent nodes belong equally to their associated community. However, some nodes are more important in the community than others. To date, efforts have been primarily driven to identify communities as a whole, rather than understanding to what extent an individual node belongs to its community. Therefore, most metrics for evaluating communities, for example modularity, are global. These metrics produce a score for each community, not for each individual node. In this paper, we argue that the belongingness of nodes in a community is not uniform. The central idea of permanence is based on the observation that the strength of membership of a vertex to a community depends upon two factors: (i) the the extent of connections of the vertex within its community versus outside its community, and (ii) how tightly the vertex is connected internally. We discuss how permanence ...

  19. Community Attachment and Satisfaction: The Role of a Community's Social Network Structure

    Science.gov (United States)

    Crowe, Jessica

    2010-01-01

    This paper links the micro and macro levels of analysis by examining how different aspects of community sentiment are affected by one's personal ties to the community compared with the organizational network structure of the community. Using data collected from residents of six communities in Washington State, network analysis combined with…

  20. Dynamics and control of diseases in networks with community structure.

    Directory of Open Access Journals (Sweden)

    Marcel Salathé

    2010-04-01

    Full Text Available The dynamics of infectious diseases spread via direct person-to-person transmission (such as influenza, smallpox, HIV/AIDS, etc. depends on the underlying host contact network. Human contact networks exhibit strong community structure. Understanding how such community structure affects epidemics may provide insights for preventing the spread of disease between communities by changing the structure of the contact network through pharmaceutical or non-pharmaceutical interventions. We use empirical and simulated networks to investigate the spread of disease in networks with community structure. We find that community structure has a major impact on disease dynamics, and we show that in networks with strong community structure, immunization interventions targeted at individuals bridging communities are more effective than those simply targeting highly connected individuals. Because the structure of relevant contact networks is generally not known, and vaccine supply is often limited, there is great need for efficient vaccination algorithms that do not require full knowledge of the network. We developed an algorithm that acts only on locally available network information and is able to quickly identify targets for successful immunization intervention. The algorithm generally outperforms existing algorithms when vaccine supply is limited, particularly in networks with strong community structure. Understanding the spread of infectious diseases and designing optimal control strategies is a major goal of public health. Social networks show marked patterns of community structure, and our results, based on empirical and simulated data, demonstrate that community structure strongly affects disease dynamics. These results have implications for the design of control strategies.

  1. Community Structure in Online Collegiate Social Networks

    Science.gov (United States)

    Traud, Amanda; Kelsic, Eric; Mucha, Peter; Porter, Mason

    2009-03-01

    Online social networking sites have become increasingly popular with college students. The networks we studied are defined through ``friendships'' indicated by Facebook users from UNC, Oklahoma, Caltech, Georgetown, and Princeton. We apply the tools of network science to study the Facebook networks from these five different universities at a single point in time. We investigate each single-institution network's community structure, which we obtain through partitioning the graph using an eigenvector method. We use both graphical and quantitative tools, including pair-counting methods, which we interpret through statistical analysis and permutation tests to measure the correlations between the network communities and a set of characteristics given by each user (residence, class year, major, and high school). We also analyze the single gender subsets of these networks, and the impact of missing demographical data. Our study allows us to compare the online social networks for the five schools as well as infer differences in offline social interactions. At the schools studied, we were able to define which characteristics of the Facebook users correlate best with friendships.

  2. Scale-dependent changes in the functional diversity of macrophytes in subtropical freshwater lakes in south China.

    Science.gov (United States)

    Fu, Hui; Zhong, Jiayou; Fang, Shaowen; Hu, Jianmin; Guo, Chunjing; Lou, Qian; Yuan, Guixiang; Dai, Taotao; Li, Zhongqiang; Zhang, Meng; Li, Wei; Xu, Jun; Cao, Te

    2017-08-15

    Ecological processes are generally scale-dependent and there is little consensus about the relative importance of deterministic versus stochastic processes in driving patterns of biological diversity. We investigated how the relationship between functional dispersion and environmental gradients changes with spatial scale in subtropical freshwater lakes. The functional alpha and beta dispersions of all the tested traits were significantly under-dispersed across spatial scales and along environmental gradients. Results showed more functional similarity within communities in leaf dry mass content and flowering duration but less functional turnover among communities in all the tested traits at regional scales (Yunnan-Guizhou plateau and the middle and low reaches of the Yangtze River). The strengths and directions of environmental effects on the functional alpha and beta dispersions depended on the selected traits, diversity metrics and spatial scales. Surprisingly, broad-scale factors - elevation and water transparency - decreased the functional turnover for most traits along the gradients, whereas fine-scale factors - water depth - produced the opposite patterns along the gradient, depending on the trait selected. Our study highlights the dominant role of deterministic assembly processes in structuring the local functional composition and governing the spatial functional turnover of macrophyte communities across multiple spatial scales.

  3. Feature Analysis and Modeling of the Network Community Structure

    Institute of Scientific and Technical Information of China (English)

    袁超; 柴毅; 魏善碧

    2012-01-01

    Community structure has an important influence on the structural and dynamic characteristics of the complex systems.So it has attracted a large number of researchers.However,due to its complexity,the mechanism of action of the community structure is still not clear to this day.In this paper,some features of the community structure have been discussed.And a constraint model of the community has been deduced.This model is effective to identify the communities.And especially,it is effective to identify the overlapping nodes between the communities.Then a community detection algorithm,which has linear time complexity,is proposed based on this constraint model,a proposed node similarity model and the Modularity Q.Through some experiments on a series of real-world and synthetic networks,the high performances of the algorithm and the constraint model have been illustrated.

  4. Biomass production by freshwater and marine macrophytes

    Energy Technology Data Exchange (ETDEWEB)

    North, W.J.; Gerard, V.A.; Kuwabara, J.S.

    1981-01-01

    Research on aquatic macrophytes as producers of biomass has been undertaken at Woods Hole Oceanographic Institution (WHOI) on the east coast and on the west coast by a group of collaborators in a joint effort known as the Marine Biomass Project. Studies at WHOI have focused on estuarine and coastal situations with some attention recently to freshwater plants. The Marine Farm Project has primarily been concerned with oceanic biomass production. A group at WHOI has undertaken a wide variety of studies concerning aquatic macrophytes including nutrient uptake, growth, yields, and environmental factors affecting yields. Aquatic biomass production systems have been surveyed on a worldwide basis and currently the role of carbon as a potential limiting nutrient in biomass culturing is being examined. The Marine Farm Project is presently attempting to grow giant kelp in offshore waters off southern California. Other work related to aquatic biomass production includes an investigation at the University of California, Berkeley, of microalgae in ponds. This paper will emphasize discussion of the kelp production phases of the Marine Farm Project. Activities by the WHOI are briefly summarized.

  5. An optimisation approach for shallow lake restoration through macrophyte management

    Science.gov (United States)

    Xu, Z. H.; Yin, X. A.; Yang, Z. F.

    2014-06-01

    Lake eutrophication is a serious global environmental issue. Phytoremediation is a promising, cost-effective, and environmentally friendly technology for water quality restoration. However, besides nutrient removal, macrophytes also deeply affect the hydrologic cycle of a lake system through evapotranspiration. Changes in hydrologic cycle caused by macrophytes have a great influence on lake water quality restoration. As a result of the two opposite effects of macrophytes on water quality restoration (i.e. an increase in macrophytes can increase nutrient removal and improve water quality while also increasing evapotranspiration, reducing water volume and consequently decreasing water quality), rational macrophyte control through planting and harvest is very important. In this study, a new approach is proposed to optimise the initial planting area and monthly harvest scheme of macrophytes for water quality restoration. The month-by-month effects of macrophyte management on lake water quality are considered. Baiyangdian Lake serves as a case study, using the common reed. It was found that water quality was closest to Grade III on the Chinese water quality scale when the reed planting area was 123 km2 (40% of the lake surface area) and most reeds would be harvested at the end of June. The optimisation approach proposed in this study will be a useful reference for lake restoration.

  6. An optimisation approach for shallow lake restoration through macrophyte management

    Directory of Open Access Journals (Sweden)

    Z. H. Xu

    2014-01-01

    Full Text Available Lake eutrophication is a serious global environmental issue. Phytoremediation is a promising, cost-effective, and environmentally friendly technology for water quality restoration. However, besides nutrient removal, macrophytes also deeply affect the hydrologic cycle of lake system through evapotranspiration. Changes in hydrologic cycle caused by macrophytes have a great influence on lake water quality restoration. As a result of the two opposite effects of macrophytes on water quality restoration (i.e. an increase in macrophytes can increase nutrient removal and improve water quality while also increasing evapotranspiration, reducing water volume and consequently decreasing water quality, rational macrophyte control through planting and harvest is very important. In this study, a new approach is proposed to optimise the initial planting area and monthly harvest scheme of macrophytes for water quality restoration. The month-by-month effects of macrophyte management on lake water quality are considered. Baiyangdian Lake serves as a case study, using the common reed. It was found that water quality was closest to Grade III on the Chinese water quality scale when the reed planting area was 123 km2 (40% of the lake surface area and most reeds would be harvested at the end of June. The optimisation approach proposed in this study will be a useful reference for lake restoration.

  7. Effects of taxonomy, sediment, and water column on C:N:P stoichiometry of submerged macrophytes in Yangtze floodplain shallow lakes, China.

    Science.gov (United States)

    Su, Haojie; Wu, Yao; Xie, Ping; Chen, Jun; Cao, Te; Xia, Wulai

    2016-11-01

    Carbon (C), nitrogen (N) and phosphorus (P) are the three most important essential elements limiting growth of primary producers. Submerged macrophytes generally absorb nutrients from sediments by root uptake. However, the C:N:P stoichiometric signatures of plant tissue are affected by many additional factors such as taxonomy, nutrient availability, and light availability. We first revealed the relative importance of taxonomy, sediment, and water column on plant C:N:P stoichiometry using variance partitioning based on partial redundancy analyses. Results showed that taxonomy was the most important factor in determining C:N:P stoichiometry, then the water column and finally the sediment. In this study, a significant positive relationship was found between community C concentration and macrophyte community biomass, indicating that the local low C availability in macrophytes probably was the main reason why submerged macrophytes declined in Yangtze floodplain shallow lakes. Based on our study, it is suggested that submerged macrophytes in Yangtze floodplain shallow lakes are primarily limited by low light levels rather than nutrient availability.

  8. Growing networks of overlapping communities with internal structure

    Science.gov (United States)

    Young, Jean-Gabriel; Hébert-Dufresne, Laurent; Allard, Antoine; Dubé, Louis J.

    2016-08-01

    We introduce an intuitive model that describes both the emergence of community structure and the evolution of the internal structure of communities in growing social networks. The model comprises two complementary mechanisms: One mechanism accounts for the evolution of the internal link structure of a single community, and the second mechanism coordinates the growth of multiple overlapping communities. The first mechanism is based on the assumption that each node establishes links with its neighbors and introduces new nodes to the community at different rates. We demonstrate that this simple mechanism gives rise to an effective maximal degree within communities. This observation is related to the anthropological theory known as Dunbar's number, i.e., the empirical observation of a maximal number of ties which an average individual can sustain within its social groups. The second mechanism is based on a recently proposed generalization of preferential attachment to community structure, appropriately called structural preferential attachment (SPA). The combination of these two mechanisms into a single model (SPA+) allows us to reproduce a number of the global statistics of real networks: The distribution of community sizes, of node memberships, and of degrees. The SPA+ model also predicts (a) three qualitative regimes for the degree distribution within overlapping communities and (b) strong correlations between the number of communities to which a node belongs and its number of connections within each community. We present empirical evidence that support our findings in real complex networks.

  9. Pinning controllability of complex networks with community structure.

    Science.gov (United States)

    Miao, Qingying; Tang, Yang; Kurths, Jürgen; Fang, Jian-an; Wong, W K

    2013-09-01

    In this paper, we study the controllability of networks with different numbers of communities and various strengths of community structure. By means of simulations, we show that the degree descending pinning scheme performs best among several considered pinning schemes under a small number of pinned nodes, while the degree ascending pinning scheme is becoming more powerful by increasing the number of pinned nodes. It is found that increasing the number of communities or reducing the strength of community structure is beneficial for the enhancement of the controllability. Moreover, it is revealed that the pinning scheme with evenly distributed pinned nodes among communities outperforms other kinds of considered pinning schemes.

  10. Monitoramento da composição específica da comunidade de macrófitas aquáticas no reservatório Luis Eduardo Magalhães Monitoring the specific composition of macrophyte communities in Luis Eduardo Magalhaes reservoir

    Directory of Open Access Journals (Sweden)

    S.F. Lolis

    2011-06-01

    Full Text Available O objetivo deste trabalho foi avaliar a composição e distribuição espacial e temporal da comunidade de macrófitas aquáticas diante de algumas variáveis abióticas no reservatório Luis Eduardo Magalhães, localizado no rio Tocantins. As coletas foram bimestrais, no período de março de 2005 a janeiro de 2006, em cinco regiões. Em cada região foram demarcados 15 pontos de coleta. Foram mensuradas a transparência da água e a condutividade elétrica em cada ponto de amostragem. Para avaliar a composição da comunidade e a distribuição das espécies, foi percorrida uma distância de cerca de 100 m de margem com embarcação em baixa velocidade, por aproximadamente 10 minutos. As espécies submersas foram inventariadas com um rastelo até 4 m de profundidade. Foi calculada a frequência de ocorrência e a diversidade beta. Os dados de presença e ausência das espécies foram analisados utilizando Análise de Correspondência Destendenciada DCA. Uma ANOVA One-Way foi empregada para avaliar o efeito dos períodos e regiões sobre as variáveis abióticas e bióticas. Foi aplicado o teste a posteriori de Tukey quando houve diferenças significativas entre as variáveis analisadas (PThis study aimed to evaluate the composition and spatial and temporal distribution of a community of macrophytes in response to abiotic factors in Luis Eduardo Magalhães Reservoir, in the Tocantins River. Samplings were collected every two months, from March 2005 to January 2006 in five regions of the reservoir. In each region, 15 collection sites were selected. The abiotic variables measured were the Secchi disk depth, electrical conductivity, air temperature, and rain and water levels. A standardized sampling effort was applied to assess macrophyte species distribution and community composition. In each site, a distance of 100 m from the shore was covered with a boat maintaining low and constant velocity, for approximately 10 minutes. The submerged species

  11. Influence of community structure on the synchronization of power network

    Science.gov (United States)

    Yang, Li-Xin; Jiang, Jun; Liu, Xiao-Jun

    2016-12-01

    This paper studies the synchronizability of power network with community structure. Second-order Kuramoto-like oscillators with dissimilar natural frequencies are used as a coarse-scale model for an electrical power network that contains generators and consumers. The impact of community structure on frequency synchronization of power network is investigated, focusing on the parameters such as community strength, community number and connection strategy between communities. Numerical simulations show that increasing the community strength above a certain critical threshold or adding new communities to the network will be beneficial for the synchronization. Of course, connecting high-degree nodes among communities will be a best strategy to enhance synchronization. Furthermore, it is observed that the synchronizability of the network is significantly influenced by adding new links with different characteristics.

  12. Enhancing community detection by using local structural information

    Science.gov (United States)

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

    2016-03-01

    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.

  13. A new dynamic null model for phylogenetic community structure.

    Science.gov (United States)

    Pigot, Alex L; Etienne, Rampal S

    2015-02-01

    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 allopatric speciation, colonisation and local extinction. Incorporating these processes fundamentally alters the structure of communities expected due to chance, with speciation leading to phylogenetic overdispersion compared to a classical statistical null model assuming equal probabilities of community membership. Applying this method to bird and primate communities in South America we show that patterns of phylogenetic overdispersion - often attributed to negative biotic interactions - are instead consistent with a species neutral model of allopatric speciation, colonisation and local extinction. Our findings provide a new null expectation for phylogenetic community patterns and highlight the importance of explicitly accounting for the dynamic history of assembly when testing the mechanisms governing community structure.

  14. Structure and biodiversity of zooplankton communities in freshwater habitats of a Vereda Wetland Region, Minas Gerais, Brazil

    Directory of Open Access Journals (Sweden)

    Olívia Penatti Pinese

    2015-09-01

    Full Text Available Abstract Aims: Vereda wetlands are among the most important aquatic habitats in Brazilian savannah (Cerrado because of their association with river springs and its relevancy for biodiversity conservation. This study aimed to determine and compare the biodiversity of zooplankton in vereda lakes, differentiated by the presence or absence of aquatic macrophytes at an environmental reserve in Uberlândia, Minas Geais, Southeastern Brazil. Zooplanctonic abundance patterns and their relation with environmental parameters were also discussed and presented through multivariate statistics. Methods Twelve samples were taken at water surface, at 15-day intervals in 2006. It was observed a total richness of 75 species, including 12 genera, 29 species and one sub-species as new records for Minas Gerais State. Results Rotifers were the predominant group and Lecanidae was the most diverse family. Among cladocerans, Chydoridae showed the greatest richness and Bosminidae the highest abundance. Few adult copepods were sampled in this study, but nauplii were very frequent. Cyclopidae was the most common family among copepods and there was no record of Calanoida. Conclusions The difference in composition among the studied lakes was remarkable. The lake with macrophytes showed the greatest richness but the lowest density, and the opposite situation occurred in the other lake. This can be explained by the fact that aquatic macrophytes, as primary producers, exert a bottom-up effect on zooplankton community, sustaining a high local diversity in contrast with a low numeric abundance of these microorganisms. Therefore, this pattern may have been created by the surround heterogeneity and, at the same time, by the reduction of available minerals of the system caused by macrophyte matter fixation. Many studies on zooplankton need to be developed in palm swamp communities in order to better comprehend the biological diversity and the energy balance in different habitats for

  15. Detect overlapping and hierarchical community structure in networks

    CERN Document Server

    Shen, Huawei; Cai, Kai; Hu, Mao-Bin

    2008-01-01

    Clustering and community structure is crucial for many network systems and the related dynamic processes. It has been shown that communities are usually overlapping and hierarchical. However, previous methods investigate these two properties of community structure separately. This paper propose an algorithm (EAGLE) to detect both the overlapping and hierarchical properties of complex community structure together. This algorithm deals with the set of maximal cliques and adopts an agglomerative framework. The quality function of modularity is extended to evaluate the goodness of a cover. The examples of application to real world networks give excellent results.

  16. Investigating Effects of Invasive Species on Plant Community Structure

    Science.gov (United States)

    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…

  17. Temporal abiotic variability structures invertebrate communities in agricultural drainage ditches

    NARCIS (Netherlands)

    Whatley, M.H.; Vonk, J.A.; van der Geest, H.G.; Admiraal, W.

    2015-01-01

    Abiotic variability is known to structure lotic invertebrate communities, yet its influence on lentic invertebrates is not clear. This study tests the hypothesis that variability of nutrients and macro-ions are structuring invertebrate communities in agricultural drainage ditches. This was determine

  18. Community Structural Instability, Anomie, Imitation and Adolescent Suicidal Behavior

    Science.gov (United States)

    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…

  19. Investigating Effects of Invasive Species on Plant Community Structure

    Science.gov (United States)

    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…

  20. Community Structural Instability, Anomie, Imitation and Adolescent Suicidal Behavior

    Science.gov (United States)

    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…

  1. Temporal abiotic variability structures invertebrate communities in agricultural drainage ditches

    NARCIS (Netherlands)

    Whatley, M.H.; Vonk, J.A.; van der Geest, H.G.; Admiraal, W.

    2015-01-01

    Abiotic variability is known to structure lotic invertebrate communities, yet its influence on lentic invertebrates is not clear. This study tests the hypothesis that variability of nutrients and macro-ions are structuring invertebrate communities in agricultural drainage ditches. This was

  2. Effect of paclobutrazol on three different aquatic macrophytes under ...

    African Journals Online (AJOL)

    admin

    2013-09-25

    Sep 25, 2013 ... macrophytes under in vitro monoculture or polyculture conditions ... provide many beneficial ecological services, but they could also be problematic .... addition, it was also important to remove all the leaves from the explants.

  3. The structure and evolution of plankton communities

    Science.gov (United States)

    Longhurst, Alan R.

    New understanding of the circulation of ancient oceans is not yet matched by progress in our understanding of their pelagic ecology, though it was the planktonic ecosystems that generated our offshore oil and gas reserves. Can we assume that present-day models of ecosystem function are also valid for ancient seas? This question is addressed by a study of over 4000 plankton samples to derive a comprehensive, global description of zooplankton community structure in modern oceans: this shows that copepods form only 50% of the biomass of all plankton, ranging from 70% in polar to 35% in tropical seas. Comparable figures are derived from 14 other taxonomic categories of zooplankton. For trophic groupings, the data indicate globally: geletinous predators - 14%; gelatinous herbivores - 4%; raptorial predators - 33%; macrofiltering herbivores - 20%; macrofiltering omnivores - 25%; and detritivores - 3%. A simple, idealized model for the modern pelagic ecosystem is derived from these percentages which indicates that metazooplankton are not the most important consumers of pico- and nano-plankton production which itself probably constitutes 90% of primary production in warm oceans. This model is then compared with candidate life-forms available in Palaeozoic and Mesozoic oceans to determine to what extent it is also valid for ancient ecosystems: it is concluded that it is probably unnecessary to postulate models fundamentally differing from it in order to accommodate the life-forms, both protozoic and metazoic, known to have populated ancient seas. Remarkably few life-forms have existed which cannot be paralleled in the modern ocean, which contains remarkably few life-forms which cannot be paralleled in the Palaeozoic ocean. As a first assumption, then, it is reasonable to assume that energy pathways were similar in ancient oceans to those we study today.

  4. Oligochaeta (Annelida: Clitellata) associated to aquatic macrophytes in Brazil

    OpenAIRE

    Nathalie Aparecida de Oliveira Sanches; Marina Gulo Alcorinte; Lucas Henrique Sahm; Guilherme Rossi Gorni; Maria Lúcia Ribeiro

    2016-01-01

    Oligochaeta are still characterized as a poorly studied group among the aquatic macroinvertebrates and few studies about their ecology were conducted in Brazil. Thus, our study aimed to provide an overview of the association between Oligochaeta and macrophytes, in Brazilian continental aquatic environments, by means of a literature review along with an inventory of species associated to aquatic macrophytes on marginal lagoons in the reservoir Ribeirão das Anhumas (Américo Brasiliense, São Pau...

  5. Aquatic macrophyte diversity of the Pantanal wetland and upper basin

    OpenAIRE

    VJ. Pott; Pott, A; LCP. Lima; SN. Moreira; AKM Oliveira

    2011-01-01

    This is a short review of the state of the art concerning diversity of aquatic macrophytes and the main aquatic vegetation types in the Brazilian Pantanal wetland and upper watershed. There are ca. 280 species of aquatic macrophytes on the Pantanal floodplain, with scarce endemism. On the upper watershed, Cerrado wetlands (veredas) and limestone springs have a distinct flora from the Pantanal, with twice the species richness. As a representative case of aquatic habitats influenced by river fl...

  6. Co-occurrence between macrophytes and macroinvertebrates: towards a new approach for the running waters quality evaluation?

    Directory of Open Access Journals (Sweden)

    Lorenzo Traversetti

    2014-08-01

    Full Text Available Several studies on concordance between macrophyte and macroinvertebrate communities were carried out for decades while any investigation on co-occurrence of single pair of taxa of these two groups was never addressed. Our main aim was to verify the existence of co-occurrence of single macrophyte–macroinvertebrate pair in a Mediterranean river of central Italy. We compared the co-occurrence frequencies of different plant and animal taxa with those expected by chance through the null model approach. Specifically, we proposed two main co-occurrence patterns of macrophyte and macroinvertebrate taxa in terms of aggregation (when groups co-occur more frequently than expected and segregation (when groups co-occur less frequently than expected. This approach was supported by correlations and analysis of covariance in order to identify the most significant co-occurring pairs. In this study we collected a total of 123 taxa (50 macrophytes + 73 macroinvertebrates in October 2008 and 102 (42+60 in June 2009. We obtained a total of 379 significantly correlating macrophyte-macroinvertebrate pairs. Amongst all these correlating pairs, 83.7% of them correlated in October session while 90.3% in June. All the correlating pairs showed a high relationships with human alterations in both the sampling sessions. Our results confirmed that direct correlations there are between macrophytes and macroinvertebrates, highlighting how these two biological groups co-occur mainly following the aggregative model in both sampling sessions. Therefore, it was possible to observe significant relationships between macrophyte and macroinvertebrate pairs along an entire river ecosystem. It allows us to demonstrate that there are some prospective for trying to increase the knowledge on macrophytes-macroinvertebrates co-occurrence and for suggesting to use only single pair of co-occurring taxa in the monitoring running water quality. Aware that more investigations ought to be

  7. Oligochaeta (Annelida: Clitellata associated to aquatic macrophytes in Brazil

    Directory of Open Access Journals (Sweden)

    Nathalie Aparecida de Oliveira Sanches

    2016-09-01

    Full Text Available Oligochaeta are still characterized as a poorly studied group among the aquatic macroinvertebrates and few studies about their ecology were conducted in Brazil. Thus, our study aimed to provide an overview of the association between Oligochaeta and macrophytes, in Brazilian continental aquatic environments, by means of a literature review along with an inventory of species associated to aquatic macrophytes on marginal lagoons in the reservoir Ribeirão das Anhumas (Américo Brasiliense, São Paulo, Brazil. In the review, we analyzed 10 articles, where we obtained data on 41 species. We also sampled 5 macrophyte genera, Egeria, Salvinia, Utricularia, Eleocharis, and Ceratophyllum, in August and December 2012 and in March and April 2013, in the reservoir Ribeirão das Anhumas. We registered 21 Oligochaeta species associated to these macrophytes. With the data obtained in the review along with the inventory of the reservoir Ribeirão das Anhumas, we found a total of 41 species associated to aquatic macrophytes, with a higher richness of the Naididae family (93.33%, followed by Opistocystidae (4.44%, and Alluroididae (2.22%. Our study inventoried about 48% of the Oligochaeta diversity registered in continental ecosystems in Brazil, thus highlighting the significance of macrophytes as a resource for these invertebrates, mainly for the Naididae family.

  8. Emergent macrophytes select for nitrifying and denitrifying microorganisms in constructed wetlands

    Science.gov (United States)

    Trias, Rosalia; Ramió Pujol, Sara; Bañeras, Lluis

    2014-05-01

    The use of constructed wetlands for wastewater treatment is a reliable low-cost alternative that has been widely developed during the last years. Several processes involving plants, sediments, and microbial communities contribute to nitrogen removal in wetlands. Vegetation plays an important role in this process, not only by nutrient assimilation but also by the stimulation of the plant associated microbiota. Plants supply oxygen at the close proximity of the root surface that may favour ammonia oxidizers. At the same time, exudation of organic compounds potentially speeds-up denitrification in the anoxic environment. The aim of this work was to understand the plant-microbe interactions at the root level in the Empuriabrava free water surface constructed wetland (Spain). The roots of the macrophytes Typha latifolia, Typha angustifolia, Phragmites australis and Bolboschoenus maritimus were sampled at four dates from January to September 2012, covering all the stages of plant growth. Additionally, sediment surrounding vegetation and non-vegetated sediments were sampled. Microbial community structure was analysed by pyrosequencing of bacterial and archaeal 16S rDNA and functional genes (nirK, nirS, nosZ and amoA). Bacterial communities were significantly different in sediments of the vegetated areas compared to the root surface. Plant roots exhibited a higher proportion of proteobacteria whereas Actinobacteria were dominant in sediments. The nitrifiers Nitrosomonas sp. and Nitrosococcus sp. accounted for less than 1% of all sequences. Archaeal communities were dominated by the Miscellaneous Crenarchaeotic Groups C2 and C3 and Methanomicrobia. Higher relative abundances of MCG were found in roots of P. australis, B. maritimus and T. angustifolia. Ammonia oxidizing archaea accounted for less than 0.1% of all sequences but were consistently more abundant in sediment samples compared to roots. NirK and NirS-type bacterial communities showed clearly distinct distribution

  9. Effects of Temperature, Salinity and Fish in Structuring the Macroinvertebrate Community in Shallow Lakes: Implications for Effects of Climate Change

    Science.gov (United States)

    Brucet, Sandra; Boix, Dani; Nathansen, Louise W.; Quintana, Xavier D.; Jensen, Elisabeth; Balayla, David; Meerhoff, Mariana; Jeppesen, Erik

    2012-01-01

    Climate warming may lead to changes in the trophic structure and diversity of shallow lakes as a combined effect of increased temperature and salinity and likely increased strength of trophic interactions. We investigated the potential effects of temperature, salinity and fish on the plant-associated macroinvertebrate community by introducing artificial plants in eight comparable shallow brackish lakes located in two climatic regions of contrasting temperature: cold-temperate and Mediterranean. In both regions, lakes covered a salinity gradient from freshwater to oligohaline waters. We undertook day and night-time sampling of macroinvertebrates associated with the artificial plants and fish and free-swimming macroinvertebrate predators within artificial plants and in pelagic areas. Our results showed marked differences in the trophic structure between cold and warm shallow lakes. Plant-associated macroinvertebrates and free-swimming macroinvertebrate predators were more abundant and the communities richer in species in the cold compared to the warm climate, most probably as a result of differences in fish predation pressure. Submerged plants in warm brackish lakes did not seem to counteract the effect of fish predation on macroinvertebrates to the same extent as in temperate freshwater lakes, since small fish were abundant and tended to aggregate within the macrophytes. The richness and abundance of most plant-associated macroinvertebrate taxa decreased with salinity. Despite the lower densities of plant-associated macroinvertebrates in the Mediterranean lakes, periphyton biomass was lower than in cold temperate systems, a fact that was mainly attributed to grazing and disturbance by fish. Our results suggest that, if the current process of warming entails higher chances of shallow lakes becoming warmer and more saline, climatic change may result in a decrease in macroinvertebrate species richness and abundance in shallow lakes. PMID:22393354

  10. Bryophytes and macro-algal growths as a part of macrophyte monitoring in rivers used for ecological assessment

    OpenAIRE

    Baláži P.; Hrivnák R.

    2015-01-01

    Altogether, 62 taxa of macrophytes including 18 bryophytes and 16 macro-algal growths were determined at 87 survey sites (73 rivers) representing the both ecoregions in Slovakia (Pannonian and Carpathian) during the years 2010–2013. Bryophytes represented the dominant community in the Carpathians, while the occurrence of macro-algal growths was relatively balanced in both ecoregions. Ordination analyses (DCA) showed an obvious shift ...

  11. Community Structure Detection Algorithm Based on the Node Belonging Degree

    Directory of Open Access Journals (Sweden)

    Jian Li

    2013-07-01

    Full Text Available In this paper, we propose a novel algorithm to identify communities in complex networks based on the node belonging degree. First, we give the concept of the node belonging degree, and then determine whether a node belongs to a community or not according to the belonging degree of the node with respect to the community. The experiment results of three real-world networks: a network with three communities with 19 nodes, Zachary Karate Club and network of American college football teams show that the proposed algorithm has satisfactory community structure detection.  

  12. Community structure of foraminiferal communities within temporal biozones from the western Arctic Ocean

    Science.gov (United States)

    Hayek, Lee-Ann C.; Buzas, Martin A.; Osterman, Lisa A.

    2007-01-01

    Community structure is often an overlooked dimension of biodiversity. Knowledge of community structure, the statistical distribution of the relative species abundance vector, makes possible comparisons and contrasts across time, space, and/or environmental conditions. Our results indicate that species of Arctic foraminifera in age-correlated cores from abyssal depths are each best described by log-series distributions. Using this structural information, we were able to determine that structural stability exists for at least 50 ka. The foraminiferal communities in this study show remarkable concordance, distributional similarity and support the neutral theory of biodiversity.

  13. Detecting Community Structure by Using a Constrained Label Propagation Algorithm.

    Directory of Open Access Journals (Sweden)

    Jia Hou Chin

    Full Text Available Community structure is considered one of the most interesting features in complex networks. Many real-world complex systems exhibit community structure, where individuals with similar properties form a community. The identification of communities in a network is important for understanding the structure of said network, in a specific perspective. Thus, community detection in complex networks gained immense interest over the last decade. A lot of community detection methods were proposed, and one of them is the label propagation algorithm (LPA. The simplicity and time efficiency of the LPA make it a popular community detection method. However, the LPA suffers from instability detection due to randomness that is induced in the algorithm. The focus of this paper is to improve the stability and accuracy of the LPA, while retaining its simplicity. Our proposed algorithm will first detect the main communities in a network by using the number of mutual neighbouring nodes. Subsequently, nodes are added into communities by using a constrained LPA. Those constraints are then gradually relaxed until all nodes are assigned into groups. In order to refine the quality of the detected communities, nodes in communities can be switched to another community or removed from their current communities at various stages of the algorithm. We evaluated our algorithm on three types of benchmark networks, namely the Lancichinetti-Fortunato-Radicchi (LFR, Relaxed Caveman (RC and Girvan-Newman (GN benchmarks. We also apply the present algorithm to some real-world networks of various sizes. The current results show some promising potential, of the proposed algorithm, in terms of detecting communities accurately. Furthermore, our constrained LPA has a robustness and stability that are significantly better than the simple LPA as it is able to yield deterministic results.

  14. Detecting Community Structure by Using a Constrained Label Propagation Algorithm

    Science.gov (United States)

    Ratnavelu, Kuru

    2016-01-01

    Community structure is considered one of the most interesting features in complex networks. Many real-world complex systems exhibit community structure, where individuals with similar properties form a community. The identification of communities in a network is important for understanding the structure of said network, in a specific perspective. Thus, community detection in complex networks gained immense interest over the last decade. A lot of community detection methods were proposed, and one of them is the label propagation algorithm (LPA). The simplicity and time efficiency of the LPA make it a popular community detection method. However, the LPA suffers from instability detection due to randomness that is induced in the algorithm. The focus of this paper is to improve the stability and accuracy of the LPA, while retaining its simplicity. Our proposed algorithm will first detect the main communities in a network by using the number of mutual neighbouring nodes. Subsequently, nodes are added into communities by using a constrained LPA. Those constraints are then gradually relaxed until all nodes are assigned into groups. In order to refine the quality of the detected communities, nodes in communities can be switched to another community or removed from their current communities at various stages of the algorithm. We evaluated our algorithm on three types of benchmark networks, namely the Lancichinetti-Fortunato-Radicchi (LFR), Relaxed Caveman (RC) and Girvan-Newman (GN) benchmarks. We also apply the present algorithm to some real-world networks of various sizes. The current results show some promising potential, of the proposed algorithm, in terms of detecting communities accurately. Furthermore, our constrained LPA has a robustness and stability that are significantly better than the simple LPA as it is able to yield deterministic results. PMID:27176470

  15. A stochastic model for detecting overlapping and hierarchical community structure.

    Directory of Open Access Journals (Sweden)

    Xiaochun Cao

    Full Text Available Community detection is a fundamental problem in the analysis of complex networks. Recently, many researchers have concentrated on the detection of overlapping communities, where a vertex may belong to more than one community. However, most current methods require the number (or the size of the communities as a priori information, which is usually unavailable in real-world networks. Thus, a practical algorithm should not only find the overlapping community structure, but also automatically determine the number of communities. Furthermore, it is preferable if this method is able to reveal the hierarchical structure of networks as well. In this work, we firstly propose a generative model that employs a nonnegative matrix factorization (NMF formulization with a l(2,1 norm regularization term, balanced by a resolution parameter. The NMF has the nature that provides overlapping community structure by assigning soft membership variables to each vertex; the l(2,1 regularization term is a technique of group sparsity which can automatically determine the number of communities by penalizing too many nonempty communities; and hence the resolution parameter enables us to explore the hierarchical structure of networks. Thereafter, we derive the multiplicative update rule to learn the model parameters, and offer the proof of its correctness. Finally, we test our approach on a variety of synthetic and real-world networks, and compare it with some state-of-the-art algorithms. The results validate the superior performance of our new method.

  16. Virality Prediction and Community Structure in Social Networks

    Science.gov (United States)

    Weng, Lilian; Menczer, Filippo; Ahn, Yong-Yeol

    2013-08-01

    How does network structure affect diffusion? Recent studies suggest that the answer depends on the type of contagion. Complex contagions, unlike infectious diseases (simple contagions), are affected by social reinforcement and homophily. Hence, the spread within highly clustered communities is enhanced, while diffusion across communities is hampered. A common hypothesis is that memes and behaviors are complex contagions. We show that, while most memes indeed spread like complex contagions, a few viral memes spread across many communities, like diseases. We demonstrate that the future popularity of a meme can be predicted by quantifying its early spreading pattern in terms of community concentration. The more communities a meme permeates, the more viral it is. We present a practical method to translate data about community structure into predictive knowledge about what information will spread widely. This connection contributes to our understanding in computational social science, social media analytics, and marketing applications.

  17. Virality Prediction and Community Structure in Social Networks

    Science.gov (United States)

    Weng, Lilian; Menczer, Filippo; Ahn, Yong-Yeol

    2013-01-01

    How does network structure affect diffusion? Recent studies suggest that the answer depends on the type of contagion. Complex contagions, unlike infectious diseases (simple contagions), are affected by social reinforcement and homophily. Hence, the spread within highly clustered communities is enhanced, while diffusion across communities is hampered. A common hypothesis is that memes and behaviors are complex contagions. We show that, while most memes indeed spread like complex contagions, a few viral memes spread across many communities, like diseases. We demonstrate that the future popularity of a meme can be predicted by quantifying its early spreading pattern in terms of community concentration. The more communities a meme permeates, the more viral it is. We present a practical method to translate data about community structure into predictive knowledge about what information will spread widely. This connection contributes to our understanding in computational social science, social media analytics, and marketing applications. PMID:23982106

  18. Plant genetics shapes inquiline community structure across spatial scales.

    Science.gov (United States)

    Crutsinger, Gregory M; Cadotte, Marc W; Sanders, Nathan J

    2009-04-01

    Recent research in community genetics has examined the effects of intraspecific genetic variation on species diversity in local communities. However, communities can be structured by a combination of both local and regional processes and to date, few community genetics studies have examined whether the effects of instraspecific genetic variation are consistent across levels of diversity. In this study, we ask whether host-plant genetic variation structures communities of arthropod inquilines within distinct habitat patches--rosette leaf galls on tall goldenrod (Solidago altissima). We found that genetic variation determined inquiline diversity at both local and regional spatial scales, but that trophic-level responses varied independently of one another. This result suggests that herbivores and predators likely respond to heritable plant traits at different spatial scales. Together, our results show that incorporating spatial scale is essential for predicting the effects of genetically variable traits on different trophic levels and levels of diversity within the communities that depend on host plants.

  19. Community structure in traffic zones based on travel demand

    Science.gov (United States)

    Sun, Li; Ling, Ximan; He, Kun; Tan, Qian

    2016-09-01

    Large structure in complex networks can be studied by dividing it into communities or modules. Urban traffic system is one of the most critical infrastructures. It can be abstracted into a complex network composed of tightly connected groups. Here, we analyze community structure in urban traffic zones based on the community detection method in network science. Spectral algorithm using the eigenvectors of matrices is employed. Our empirical results indicate that the traffic communities are variant with the travel demand distribution, since in the morning the majority of the passengers are traveling from home to work and in the evening they are traveling a contrary direction. Meanwhile, the origin-destination pairs with large number of trips play a significant role in urban traffic network's community division. The layout of traffic community in a city also depends on the residents' trajectories.

  20. Assembly and phylogenetic structure of Neotropical palm communities

    DEFF Research Database (Denmark)

    Eiserhardt, Wolf L.; Svenning, J.-C.; Balslev, Henrik

    Diversity, composition and dynamics of Neotropical palm communities are receiving an increasing amount of attention due to their economic importance, but also because their high species richness and functional diversity render them valuable model systems for overall forest biodiversity. However......, to better understand these palm communities, it is crucial to gain insight into the mechanisms responsible for their assembly. These can be dispersal limitation, environmental filtering, or biotic interactions. If the degree of niche conservatism is known for a group of organisms, patterns of community...... phylogenetic structure can be directly traced back to mechanisms of community assembly. We aim to examine this for Neotropical palm communities. Phylogenetic structure will be inferred on different spatial scales and for different community definitions (plot-based and environment-based). To overcome...

  1. Community structure of complex networks based on continuous neural network

    Science.gov (United States)

    Dai, Ting-ting; Shan, Chang-ji; Dong, Yan-shou

    2017-09-01

    As a new subject, the research of complex networks has attracted the attention of researchers from different disciplines. Community structure is one of the key structures of complex networks, so it is a very important task to analyze the community structure of complex networks accurately. In this paper, we study the problem of extracting the community structure of complex networks, and propose a continuous neural network (CNN) algorithm. It is proved that for any given initial value, the continuous neural network algorithm converges to the eigenvector of the maximum eigenvalue of the network modularity matrix. Therefore, according to the stability of the evolution of the network symbol will be able to get two community structure.

  2. Phylogenetic structure in tropical hummingbird communities

    DEFF Research Database (Denmark)

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

    2009-01-01

    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...... an expensive means of locomotion at high elevations. We found that communities in the lowlands on opposite sides of the Andes tend to be phylogenetically similar despite their large differences in species composition, a pattern implicating the Andes as an important dispersal barrier. In contrast, along...... the steep environmental gradient between the lowlands and the Andes we found evidence that species turnover is comprised of relatively distantly related species. The integration of local and regional patterns of diversity across environmental gradients and biogeographic barriers provides insight...

  3. Detecting highly overlapping community structure by greedy clique expansion

    CERN Document Server

    Lee, Conrad; 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, 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 distinct cliques as seeds and expands these seeds by greedily optimizing a local fitness function. We perform extensive benchmarks on synthetic data to demonstrate that GCE's good performance is robust across diverse graph topologies. Significantly, GCE is the only algorithm to perform well on these synthetic graphs, in which every node belongs to multiple communities. Furthermore, when put to the task of identifying functional modules in protein interaction data, and college dorm assignments in Facebook friendship data, we find ...

  4. Effects of drought on avian community structure

    Science.gov (United States)

    Thomas P. Albright; Anna M. Pidgeon; Chadwick D. Rittenhouse; Murray K. Clayton; Curtis H. Flather; Patrick D. Culbert; Brian D. Wardlow; Volker C. Radeloff

    2010-01-01

    Droughts are expected to become more frequent under global climate change. Avifauna depend on precipitation for hydration, cover, and food. While there are indications that avian communities respond negatively to drought, little is known about the response of birds with differing functional and behavioural traits, what time periods and indicators of drought are most...

  5. Microbial Community Structure and Denitrification in a Wetland Mitigation Bank▿

    Science.gov (United States)

    Peralta, Ariane L.; Matthews, Jeffrey W.; Kent, Angela D.

    2010-01-01

    Wetland mitigation is implemented to replace ecosystem functions provided by wetlands; however, restoration efforts frequently fail to establish equivalent levels of ecosystem services. Delivery of microbially mediated ecosystem functions, such as denitrification, is influenced by both the structure and activity of the microbial community. The objective of this study was to compare the relationship between soil and vegetation factors and microbial community structure and function in restored and reference wetlands within a mitigation bank. Microbial community composition was assessed using terminal restriction fragment length polymorphism targeting the 16S rRNA gene (total bacteria) and the nosZ gene (denitrifiers). Comparisons of microbial function were based on potential denitrification rates. Bacterial community structures differed significantly between restored and reference wetlands; denitrifier community assemblages were similar among reference sites but highly variable among restored sites throughout the mitigation bank. Potential denitrification was highest in the reference wetland sites. These data demonstrate that wetland restoration efforts in this mitigation bank have not successfully restored denitrification and that differences in potential denitrification rates may be due to distinct microbial assemblages observed in restored and reference (natural) wetlands. Further, we have identified gradients in soil moisture and soil fertility that were associated with differences in microbial community structure. Microbial function was influenced by bacterial community composition and soil fertility. Identifying soil factors that are primary ecological drivers of soil bacterial communities, especially denitrifying populations, can potentially aid the development of predictive models for restoration of biogeochemical transformations and enhance the success of wetland restoration efforts. PMID:20453124

  6. Exploratory Visualization of Graphs Based on Community Structure

    Science.gov (United States)

    Liu, Yujie

    2013-01-01

    Communities, also called clusters or modules, are groups of nodes which probably share common properties and/or play similar roles within a graph. They widely exist in real networks such as biological, social, and information networks. Allowing users to interactively browse and explore the community structure, which is essential for understanding…

  7. Faculty Scholarship at Community Colleges: Culture, Institutional Structures, and Socialization

    Science.gov (United States)

    Morest, Vanessa Smith

    2015-01-01

    This chapter looks at community college faculty engagement in scholarship. Community college faculty spend the majority of their time engaged in teaching, and therefore their scholarship typically focuses on strengthening curriculum and instruction. The paper identifies some of the structural and cultural challenges and supports to scholarship at…

  8. A new dynamic null model for phylogenetic community structure

    NARCIS (Netherlands)

    Pigot, Alex L; Etienne, Rampal S

    2015-01-01

    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

  9. Ecological and evolutionary effects of stickleback on community structure.

    Directory of Open Access Journals (Sweden)

    Simone Des Roches

    Full Text Available Species' ecology and evolution can have strong effects on communities. Both may change concurrently when species colonize a new ecosystem. We know little, however, about the combined effects of ecological and evolutionary change on community structure. We simultaneously examined the effects of top-predator ecology and evolution on freshwater community parameters using recently evolved generalist and specialist ecotypes of three-spine stickleback (Gasterosteus aculeatus. We used a mesocosm experiment to directly examine the effects of ecological (fish presence and density and evolutionary (phenotypic diversity and specialization factors on community structure at lower trophic levels. We evaluated zooplankton biomass and composition, periphyton and phytoplankton chlorophyll-a concentration, and net primary production among treatments containing different densities and diversities of stickleback. Our results showed that both ecological and evolutionary differences in the top-predator affect different aspects of community structure and composition. Community structure, specifically the abundance of organisms at each trophic level, was affected by stickleback presence and density, whereas composition of zooplankton was influenced by stickleback diversity and specialization. Primary productivity, in terms of chlorophyll-a concentration and net primary production was affected by ecological but not evolutionary factors. Our results stress the importance of concurrently evaluating both changes in density and phenotypic diversity on the structure and composition of communities.

  10. variabilty in parasites' community structure and composition in cat ...

    African Journals Online (AJOL)

    Mgina

    ABSTRACT. This study investigated the composition and structure of the parasite communities in Cat fish ... The western shore is mainly sandy ... part of which is sandy and rocky and along the shores ..... Sediment And Microalgae From Lake ...

  11. Assessment of the Potential Biological Activity of Low Molecular Weight Metabolites of Freshwater Macrophytes with QSAR

    National Research Council Canada - National Science Library

    Kurashov, Evgeny A; Fedorova, Elena V; Krylova, Julia V; Mitrukova, Galina G

    2016-01-01

    ... (Prediction of Activity Spectra for Substances) for the major components of three macrophytes widespread in the Holarctic species of freshwater, emergent macrophyte with floating leaves, Nuphar lutea (L.) Sm...

  12. Host niches and defensive extended phenotypes structure parasitoid wasp communities.

    Directory of Open Access Journals (Sweden)

    Richard Bailey

    2009-08-01

    Full Text Available Oak galls are spectacular extended phenotypes of gallwasp genes in host oak tissues and have evolved complex morphologies that serve, in part, to exclude parasitoid natural enemies.Parasitoids and their insect herbivore hosts have coevolved to produce diverse communities comprising about a third of all animal species. The factors structuring these communities, however, remain poorly understood. An emerging theme in community ecology is the need to consider the effects of host traits, shaped by both natural selection and phylogenetic history, on associated communities of natural enemies. Here we examine the impact of host traits and phylogenetic relatedness on 48 ecologically closed and species-rich communities of parasitoids attacking gall-inducing wasps on oaks. Gallwasps induce the development of spectacular and structurally complex galls whose species- and generation-specific morphologies are the extended phenotypes of gallwasp genes. All the associated natural enemies attack their concealed hosts through gall tissues, and several structural gall traits have been shown to enhance defence against parasitoid attack. Here we explore the significance of these and other host traits in predicting variation in parasitoid community structure across gallwasp species. In particular, we test the "Enemy Hypothesis," which predicts that galls with similar morphology will exclude similar sets of parasitoids and therefore have similar parasitoid communities. Having controlled for phylogenetic patterning in host traits and communities, we found significant correlations between parasitoid community structure and several gall structural traits (toughness, hairiness, stickiness, supporting the Enemy Hypothesis. Parasitoid community structure was also consistently predicted by components of the hosts' spatiotemporal niche, particularly host oak taxonomy and gall location (e.g., leaf versus bud versus seed. The combined explanatory power of structural and

  13. Modeling community structure and topics in dynamic text networks

    CERN Document Server

    Henry, Teague; Chai, Christine; Owens-Oas, Derek

    2016-01-01

    The last decade has seen great progress in both dynamic network modeling and topic modeling. This paper draws upon both areas to create a Bayesian method that allows topic discovery to inform the latent network model and the network structure to facilitate topic identification. We apply this method to the 467 top political blogs of 2012. Our results find complex community structure within this set of blogs, where community membership depends strongly upon the set of topics in which the blogger is interested.

  14. Community detection for networks with unipartite and bipartite structure

    OpenAIRE

    Chang, Chang; Tang, Chao

    2013-01-01

    Finding community structures in networks is important in network science, technology, and applications. To date, most algorithms that aim to find community structures only focus either on unipartite or bipartite networks. A unipartite network consists of one set of nodes and a bipartite network consists of two nonoverlapping sets of nodes with only links joining the nodes in different sets. However, a third type of network exists, defined here as the mixture network. Just like a bipartite net...

  15. Patterns in marine microbial community structure

    OpenAIRE

    2012-01-01

    Programa en Oceanografía [EN] Understanding the distribution of the different picoplankton groups represents a central tenet of marine microbial ecology. Centering our study on the three major groups constituting the bulk picoplankton community (size 0.2-3 mm), we sought to analyze the distribution of autotrophic bacteria (Synechococcus and Prochlorococcus), photosynthetic Picoeukaryotes pPeuk, and heterotrophic bacteria. [ES] La comprensión de la distribución de los distint...

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

    Science.gov (United States)

    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.

  17. Community detection using global and local structural information

    Indian Academy of Sciences (India)

    Hai-Long Yan; Ju Xiang; Xiao-Yu Zhang; Jun-Feng Fan; Fang Chane; Gen-Yi Fu; Er-Min Guo; Xin-Guang Hu; Ke Hu; Ru-Min Wang

    2013-01-01

    Community detection is of considerable importance for understanding both the structure and function of complex networks. In this paper, we introduced the general procedure of the community detection algorithms using global and local structural information, where the edge betweenness and the local similarity measures respectively based on local random walk dynamics and local cyclic structures were used. The algorithms were tested on artificial and real-world networks. The results clearly show that all the algorithms have excellent performance in the tests and the local similarity measure based on local random walk dynamics is superior to that based on local cyclic structures.

  18. Community structure in time-dependent, multiscale, and multiplex networks.

    Science.gov (United States)

    Mucha, Peter J; Richardson, Thomas; Macon, Kevin; Porter, Mason A; Onnela, Jukka-Pekka

    2010-05-14

    Network science is an interdisciplinary endeavor, with methods and applications drawn from across the natural, social, and information sciences. A prominent problem in network science is the algorithmic detection of tightly connected groups of nodes known as communities. We developed a generalized framework of network quality functions that allowed us to study the community structure of arbitrary multislice networks, which are combinations of individual networks coupled through links that connect each node in one network slice to itself in other slices. This framework allows studies of community structure in a general setting encompassing networks that evolve over time, have multiple types of links (multiplexity), and have multiple scales.

  19. Jellyfish modulate bacterial dynamic and community structure.

    Science.gov (United States)

    Tinta, Tinkara; Kogovšek, Tjaša; Malej, Alenka; Turk, Valentina

    2012-01-01

    Jellyfish blooms have increased in coastal areas around the world and the outbreaks have become longer and more frequent over the past few decades. The Mediterranean Sea is among the heavily affected regions and the common bloom-forming taxa are scyphozoans Aurelia aurita s.l., Pelagia noctiluca, and Rhizostoma pulmo. Jellyfish have few natural predators, therefore their carcasses at the termination of a bloom represent an organic-rich substrate that supports rapid bacterial growth, and may have a large impact on the surrounding environment. The focus of this study was to explore whether jellyfish substrate have an impact on bacterial community phylotype selection. We conducted in situ jellyfish-enrichment experiment with three different jellyfish species. Bacterial dynamic together with nutrients were monitored to assess decaying jellyfish-bacteria dynamics. Our results show that jellyfish biomass is characterized by protein rich organic matter, which is highly bioavailable to 'jellyfish-associated' and 'free-living' bacteria, and triggers rapid shifts in bacterial population dynamics and composition. Based on 16S rRNA clone libraries and denaturing gradient gel electrophoresis (DGGE) analysis, we observed a rapid shift in community composition from unculturable Alphaproteobacteria to culturable species of Gammaproteobacteria and Flavobacteria. The results of sequence analyses of bacterial isolates and of total bacterial community determined by culture independent genetic analysis showed the dominance of the Pseudoalteromonadaceae and the Vibrionaceae families. Elevated levels of dissolved proteins, dissolved organic and inorganic nutrient release, bacterial abundance and carbon production as well as ammonium concentrations characterized the degradation process. The biochemical composition of jellyfish species may influence changes in the amount of accumulated dissolved organic and inorganic nutrients. Our results can contribute insights into possible changes in

  20. Jellyfish modulate bacterial dynamic and community structure.

    Directory of Open Access Journals (Sweden)

    Tinkara Tinta

    Full Text Available Jellyfish blooms have increased in coastal areas around the world and the outbreaks have become longer and more frequent over the past few decades. The Mediterranean Sea is among the heavily affected regions and the common bloom-forming taxa are scyphozoans Aurelia aurita s.l., Pelagia noctiluca, and Rhizostoma pulmo. Jellyfish have few natural predators, therefore their carcasses at the termination of a bloom represent an organic-rich substrate that supports rapid bacterial growth, and may have a large impact on the surrounding environment. The focus of this study was to explore whether jellyfish substrate have an impact on bacterial community phylotype selection. We conducted in situ jellyfish-enrichment experiment with three different jellyfish species. Bacterial dynamic together with nutrients were monitored to assess decaying jellyfish-bacteria dynamics. Our results show that jellyfish biomass is characterized by protein rich organic matter, which is highly bioavailable to 'jellyfish-associated' and 'free-living' bacteria, and triggers rapid shifts in bacterial population dynamics and composition. Based on 16S rRNA clone libraries and denaturing gradient gel electrophoresis (DGGE analysis, we observed a rapid shift in community composition from unculturable Alphaproteobacteria to culturable species of Gammaproteobacteria and Flavobacteria. The results of sequence analyses of bacterial isolates and of total bacterial community determined by culture independent genetic analysis showed the dominance of the Pseudoalteromonadaceae and the Vibrionaceae families. Elevated levels of dissolved proteins, dissolved organic and inorganic nutrient release, bacterial abundance and carbon production as well as ammonium concentrations characterized the degradation process. The biochemical composition of jellyfish species may influence changes in the amount of accumulated dissolved organic and inorganic nutrients. Our results can contribute insights into

  1. Measuring robustness of community structure in complex networks

    CERN Document Server

    Li, Hui-Jia; Chen, Luonan

    2015-01-01

    The theory of community structure is a powerful tool for real networks, which can simplify their topological and functional analysis considerably. However, since community detection methods have random factors and real social networks obtained from complex systems always contain error edges, evaluating the robustness of community structure is an urgent and important task. In this letter, we employ the critical threshold of resolution parameter in Hamiltonian function, $\\gamma_C$, to measure the robustness of a network. According to spectral theory, a rigorous proof shows that the index we proposed is inversely proportional to robustness of community structure. Furthermore, by utilizing the co-evolution model, we provides a new efficient method for computing the value of $\\gamma_C$. The research can be applied to broad clustering problems in network analysis and data mining due to its solid mathematical basis and experimental effects.

  2. Spatial structuring of bacterial communities within individual Ginkgo biloba trees.

    Science.gov (United States)

    Leff, Jonathan W; Del Tredici, Peter; Friedman, William E; Fierer, Noah

    2015-07-01

    Plant-associated microorganisms affect the health of their hosts in diverse ways, yet the distribution of these organisms within individual plants remains poorly understood. To address this knowledge gap, we assessed the spatial variability in bacterial community diversity and composition found on and in aboveground tissues of individual Ginkgo biloba trees. We sampled bacterial communities from > 100 locations per tree, including leaf, branch and trunk samples and used high-throughput sequencing of the 16S rRNA gene to determine the diversity and composition of these communities. Bacterial community structure differed strongly between bark and leaf samples, with bark samples harbouring much greater bacterial diversity and a community composition distinct from leaves. Within sample types, we observed clear spatial patterns in bacterial diversity and community composition that corresponded to the samples' proximity to the exterior of the tree. The composition of the bacterial communities found on trees is highly variable, but this variability is predictable and dependent on sampling location. Moreover, this work highlights the importance of carefully considering plant spatial structure when characterizing the microbial communities associated with plants and their impacts on plant hosts.

  3. Diversity and biomass of native macrophytes are negatively related to dominance of an invasive Poaceae in Brazilian sub-tropical streams

    Directory of Open Access Journals (Sweden)

    Luiz Felipe Gonçalves Fernandes

    2013-06-01

    Full Text Available Besides exacerbated exploitation, pollution, flow alteration and habitats degradation, freshwater biodiversity is also threatened by biological invasions. This paper addresses how native aquatic macrophyte communities are affected by the non-native species Urochloa arrecta, a current successful invader in Brazilian freshwater systems. We compared the native macrophytes colonizing patches dominated and non-dominated by this invader species. We surveyed eight streams in Northwest Paraná State (Brazil. In each stream, we recorded native macrophytes' richness and biomass in sites where U. arrecta was dominant and in sites where it was not dominant or absent. No native species were found in seven, out of the eight investigated sites where U. arrecta was dominant. Thus, we found higher native species richness, Shannon index and native biomass values in sites without dominance of U. arrecta than in sites dominated by this invader. Although difficult to conclude about causes of such differences, we infer that the elevated biomass production by this grass might be the primary reason for alterations in invaded environments and for the consequent impacts on macrophytes' native communities. However, biotic resistance offered by native richer sites could be an alternative explanation for our results. To mitigate potential impacts and to prevent future environmental perturbations, we propose mechanical removal of the invasive species and maintenance or restoration of riparian vegetation, for freshwater ecosystems have vital importance for the maintenance of ecological services and biodiversity and should be preserved.

  4. Linking community size structure and ecosystem functioning using metabolic theory.

    Science.gov (United States)

    Yvon-Durocher, Gabriel; Allen, Andrew P

    2012-11-05

    Understanding how biogeochemical cycles relate to the structure of ecological communities is a central research question in ecology. Here we approach this problem by focusing on body size, which is an easily measured species trait that has a pervasive influence on multiple aspects of community structure and ecosystem functioning. We test the predictions of a model derived from metabolic theory using data on ecosystem metabolism and community size structure. These data were collected as part of an aquatic mesocosm experiment that was designed to simulate future environmental warming. Our analyses demonstrate significant linkages between community size structure and ecosystem functioning, and the effects of warming on these links. Specifically, we show that carbon fluxes were significantly influenced by seasonal variation in temperature, and yielded activation energies remarkably similar to those predicted based on the temperature dependencies of individual-level photosynthesis and respiration. We also show that community size structure significantly influenced fluxes of ecosystem respiration and gross primary production, particularly at the annual time-scale. Assessing size structure and the factors that control it, both empirically and theoretically, therefore promises to aid in understanding links between individual organisms and biogeochemical cycles, and in predicting the responses of key ecosystem functions to future environmental change.

  5. Microbial community structure of a freshwater system receiving wastewater effluent.

    Science.gov (United States)

    Hladilek, Matthew D; Gaines, Karen F; Novak, James M; Collard, David A; Johnson, Daniel B; Canam, Thomas

    2016-11-01

    Despite our dependency on treatment facilities to condition wastewater for eventual release to the environment, our knowledge regarding the effects of treated water on the local watershed is extremely limited. Responses of lotic systems to the treated wastewater effluent have been traditionally investigated by examining the benthic macroinvertebrate assemblages and community structure; however, these studies do not address the microbial diversity of the water systems. In the present study, planktonic and benthic bacterial community structure were examined at 14 sites (from 60 m upstream to 12,100 m downstream) and at two time points along an aquatic system receiving treated effluent from the Charleston Wastewater Treatment Plant (Charleston, IL). Total bacterial DNA was isolated and 16S rRNA sequences were analyzed using a metagenomics platform. The community structure in planktonic bacterial communities was significantly correlated with dissolved oxygen concentration. Benthic bacterial communities were not correlated with water quality but did have a significant geographic structuring. A local restructuring effect was observed in both planktonic and benthic communities near the treated wastewater effluent, which was characterized by an increase in abundance of sphingobacteria. Sites further downstream from the wastewater facility appeared to be less influenced by the effluent. Overall, the present study demonstrated the utility of targeted high-throughput sequencing as a tool to assess the effects of treated wastewater effluent on a receiving water system, and highlighted the potential for this technology to be used for routine monitoring by wastewater facilities.

  6. Analysis of stability of community structure across multiple hierarchical levels

    CERN Document Server

    Li, Hui-Jia

    2015-01-01

    The analysis of stability of community structure is an important problem for scientists from many fields. Here, we propose a new framework to reveal hidden properties of community structure by quantitatively analyzing the dynamics of Potts model. Specifically we model the Potts procedure of community structure detection by a Markov process, which has a clear mathematical explanation. Critical topological information regarding to multivariate spin configuration could also be inferred from the spectral significance of the Markov process. We test our framework on some example networks and find it doesn't have resolute limitation problem at all. Results have shown the model we proposed is able to uncover hierarchical structure in different scales effectively and efficiently.

  7. Variation in fish community structure, richness, and diversity in 56 Danish lakes with contrasting depth, size, and trophic state: does the method matter?

    DEFF Research Database (Denmark)

    Menezes, Rosemberg; Borchsenius, Finn; Svenning, J.-C.

    2013-01-01

    The distribution of freshwater fish is influenced by food availability, habitat heterogeneity, competition, predation, trophic state, and presence/absence of macrophytes. This poses a challenge to monitoring, and researchers have been struggling to develop accurate sampling methods for obtaining...... community, as all methods miss some important species that other methods capture. However, electrofishing seems to be a fast alternative to gillnets for monitoring fish species richness and composition in littoral habitats of Danish lakes....

  8. Implementation and implications of macrophyte reconfiguration in hydraulic river modeling

    Science.gov (United States)

    Verschoren, Veerle; Schoelynck, Jonas; Buis, Kerst; Meire, Dieter; Bal, Kris; Meire, Patrick; Temmerman, Stijn

    2014-05-01

    In lowland rivers, abundant macrophyte growth can often be observed. The aquatic vegetation has an impact on the flow by creating friction which results in increased water levels and decreased flow velocities. At the same time submerged macrophytes are susceptible to hydrodynamic forces of the water. Their morphology is therefore often flexible and streamlined so that it enables reconfiguration (i.e. bending of macrophytes with water flow) and decreases potential damage at high flow velocities. Knowledge of these mutual interactions is crucial in order to model water flow in vegetated rivers. A correct estimation of flow velocity and water height is indispensable for the calculation of hydraulic, ecological and geomorphological parameters. The total resistance to water flow in a river can be described by a Manning coefficient. This value is influenced by river characteristics as well as by the presence of macrophytes. In this study a simple method is developed to quantify the resistance created by macrophytes after reconfiguration of their canopy. In order to achieve this we derive model formulations and plant parameters for three different macrophyte species and compare model simulation with measured flow velocity data for two case studies. Furthermore, the effect of macrophyte reconfiguration is investigated by modeling the same case studies with and without the implementation of macrophyte reconfiguration. It was found that the local resistance created by the vegetation was overestimated when reconfiguration was not considered. This resulted in an overestimation of stream velocity adjacent to the vegetation and an underestimation of the stream velocity within and behind the vegetation. Another effect was a higher water level gradient and consequently a higher Manning coefficient in the scenario without reconfiguration compared to the scenario with reconfiguration. Reconfiguration had also an influence on ecological and geomorphological parameters. It was found

  9. A local algorithm for detecting community structures in dynamic networks

    CERN Document Server

    Massaro, Emanuele; Guazzini, Andrea; Passarella, Andrea; Bagnoli, Franco

    2013-01-01

    The emergence and the global adaptation of mobile devices has influenced human interactions at the individual, community, and social levels leading to the so called Cyber-Physical World (CPW) convergence scenario [1]. One of the most important features of CPW is the possibility of exploiting information about the structure of social communities of users, that manifest through joint movement patterns and frequency of physical co-location: mobile devices of users that belong to the same social community are likely to "see" each other (and thus be able to communicate through ad hoc networking techniques) more frequently and regularly than devices outside of the community. In mobile opportunistic networks, this fact can be exploited, for example, to optimize networking operations such as forwarding and dissemination of messages. In this paper we present a novel local cognitive-inspired algorithm for revealing the structure of these dynamic social networks by exploiting information about physical encounters, logge...

  10. Polychaete community structure of Indian west coast shelf, Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Joydas, T.V.; Jayalakshmy, K.V.; Damodaran, R.

    CURRENT SCIENCE, VOL. 97, NO. 5, 10 SEPTEMBER 2009 634 Polychaete community structure of Indian west coast shelf, Arabian Sea Ellis 1 introduced the concept of taxono- mic sufficiency (TS) in which identifica- tion is required only to the level... the effects of pollution on marine communities. As TS moves progressively to species, costs, in terms of the expertise and time needed to identify organisms, decrease 4 . It is quicker and easier to train personnel to sort higher taxonomic levels than...

  11. 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.

  12. Random field Ising model and community structure in complex networks

    Science.gov (United States)

    Son, S.-W.; Jeong, H.; Noh, J. D.

    2006-04-01

    We propose a method to determine the community structure of a complex network. In this method the ground state problem of a ferromagnetic random field Ising model is considered on the network with the magnetic field Bs = +∞, Bt = -∞, and Bi≠s,t=0 for a node pair s and t. The ground state problem is equivalent to the so-called maximum flow problem, which can be solved exactly numerically with the help of a combinatorial optimization algorithm. The community structure is then identified from the ground state Ising spin domains for all pairs of s and t. Our method provides a criterion for the existence of the community structure, and is applicable equally well to unweighted and weighted networks. We demonstrate the performance of the method by applying it to the Barabási-Albert network, Zachary karate club network, the scientific collaboration network, and the stock price correlation network. (Ising, Potts, etc.)

  13. Structural diversity of forest communities on Baihuashan Mountain,Beijing

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The structural diversity of forests on Baihuashan Mountain,Beijing,was surveyed by a plotless method combined with branch and leaf coverage estimation in the different layers.New structural indices were constructed,calculated and compared among different communities.On the basis of previous work,structural diversity of forest communities at the stand level was described by a vertical complexity index and a horizontal heterogeneity index.From a correlational analysis among the new indices and other commonly used biodiversity indices,we concluded that the new indices are closely related to a tree height inequality index and the Shannon-Wiener index of the tree and shrub layer,which indicated that the new indices were good at indicating structural diversity in the different forests on Baihuashan Mountain.The results show that,in natural forests,structural diversity of pioneer communities is much lower than in late successive communities.In plantations,structural diversity is determined by the stage of development and tree species.Tending would increase horizontal heterogeneity and decrease vertical complexity.

  14. Observing and modelling phytoplankton community structure in the North Sea

    Science.gov (United States)

    Ford, David A.; van der Molen, Johan; Hyder, Kieran; Bacon, John; Barciela, Rosa; Creach, Veronique; McEwan, Robert; Ruardij, Piet; Forster, Rodney

    2017-03-01

    Phytoplankton form the base of the marine food chain, and knowledge of phytoplankton community structure is fundamental when assessing marine biodiversity. Policy makers and other users require information on marine biodiversity and other aspects of the marine environment for the North Sea, a highly productive European shelf sea. This information must come from a combination of observations and models, but currently the coastal ocean is greatly under-sampled for phytoplankton data, and outputs of phytoplankton community structure from models are therefore not yet frequently validated. This study presents a novel set of in situ observations of phytoplankton community structure for the North Sea using accessory pigment analysis. The observations allow a good understanding of the patterns of surface phytoplankton biomass and community structure in the North Sea for the observed months of August 2010 and 2011. Two physical-biogeochemical ocean models, the biogeochemical components of which are different variants of the widely used European Regional Seas Ecosystem Model (ERSEM), were then validated against these and other observations. Both models were a good match for sea surface temperature observations, and a reasonable match for remotely sensed ocean colour observations. However, the two models displayed very different phytoplankton community structures, with one better matching the in situ observations than the other. Nonetheless, both models shared some similarities with the observations in terms of spatial features and inter-annual variability. An initial comparison of the formulations and parameterizations of the two models suggests that diversity between the parameter settings of model phytoplankton functional types, along with formulations which promote a greater sensitivity to changes in light and nutrients, is key to capturing the observed phytoplankton community structure. These findings will help inform future model development, which should be coupled

  15. Does the Lagoa do Peixe sandbar opening influence the macrophyte richness and composition in Southern Brazil wetlands?

    Directory of Open Access Journals (Sweden)

    Ana Silvia Rolon

    2013-03-01

    Full Text Available The Lagoa do Peixe has its connection with the sea artificially opened every year at the end of winter. However, this management has been carried out without the evaluation of the impact of this opening in the aquatic biodiversity. This information is crucial for the management of the natural resources of the Lagoa do Peixe National Park, the unique Ramsar site in Southern Brazil. The following questions were analyzed: (1 Do richness and composition of aquatic macrophytes from Lagoa do Peixe floodplain varies temporarily according to the sandbar opening and closing? (2 Does the variation pattern of the macrophyte community changed according to the sandbar opening and closing? A set of eight sampling sites of 1ha were selected over the Lagoa do Peixe floodplain: four sites not influenced by the artificial sandbar opening and four sites influenced by this event, being two sites closer to the sandbar opening and the two sites distant to the sandbar opening. The samplings were carried out between November 2007 and October 2009. The results show that although the artificial sandbar breaching does not affect the aquatic macrophyte richness at the floodplain, it affects the dynamics of species composition. The hydrological variation related to this management can be the main factor of the continuous change in the species composition in the floodplain, especially in the Southern portion. In order to avoid impacts in the macrophyte conservation, the artificial sandbar opening should be considered carefully, since the area of study is one of the most important conservation units to wetland systems in Southern Brazil.

  16. Does the Lagoa do peixe sandbar opening influence the macrophyte richness and composition in Southern Brazil wetlands?

    Science.gov (United States)

    Rolon, Ana Silvia; Rocha, Odete; Maltchik, Leonardo

    2013-03-01

    The Lagoa do Peixe has its connection with the sea artificially opened every year at the end of winter. However, this management has been carried out without the evaluation of the impact of this opening in the aquatic biodiversity. This information is crucial for the management of the natural resources of the Lagoa do Peixe National Park, the unique Ramsar site in Southern Brazil. The following questions were analyzed: (1) Do richness and composition of aquatic macrophytes from Lagoa do Peixe floodplain varies temporarily according to the sandbar opening and closing? (2) Does the variation pattern of the macrophyte community changed according to the sandbar opening and closing? A set of eight sampling sites of 1ha were selected over the Lagoa do Peixe floodplain: four sites not influenced by the artificial sandbar opening and four sites influenced by this event, being two sites closer to the sandbar opening and the two sites distant to the sandbar opening. The samplings were carried out between November 2007 and October 2009. The results show that although the artificial sandbar breaching does not affect the aquatic macrophyte richness at the floodplain, it affects the dynamics of species composition. The hydrological variation related to this management can be the main factor of the continuous change in the species composition in the floodplain, especially in the Southern portion. In order to avoid impacts in the macrophyte conservation, the artificial sandbar opening should be considered carefully, since the area of study is one of the most important conservation units to wetland systems in Southern Brazil.

  17. Quantum Probabilistic Structures in Competing Lizard Communities

    CERN Document Server

    Aerts, Diederik; Kuna, Maciej; Sinervo, Barry; Sozzo, Sandro

    2012-01-01

    Almost two decades of research on the use of the mathematical formalism of quantum theory as a modeling tool for entities and their dynamics in domains different from the micro-world has now firmly shown the systematic appearance of quantum structures in aspects of human behavior and thought, such as in cognitive processes of decision-making, and in the way concepts are combined into sentences. In this paper, we extend this insight to animal behavior showing that a quantum probabilistic structure models the mating competition of three side-blotched lizard morphs. We analyze a set of experimental data collected from 1990 to 2011 on these morphs, whose territorial behavior follows a cyclic rock-paper-scissors (RPS) dynamics. Consequently we prove that a single classical Kolmogorovian space does not exist for the lizard's dynamics, and elaborate an explicit quantum description in Hilbert space faithfully modeling the gathered data. This result is relevant for population dynamics as a whole, since many systems, e...

  18. Structure of pond vegetation of a vereda in the Brazilian Cerrado

    OpenAIRE

    Moreira,Suzana Neves; POTT,Arnildo; Pott,Vali Joana; Damasceno-Junior, Geraldo Alves

    2011-01-01

    Abstract This is the first report on aquatic macrophytes in ponds of veredas (palm swamps) in the Cerrado (Brazilian savanna). We studied a pond in a vereda in Terenos, Mato Grosso do Sul state, central-western Brazil, during drought and flood periods to assess plant community structure and the relationship between species distribution and water depth. Sampling was carried out in five permanent transects, along which we placed sampling units of 1 m2 quadrats every 5 m. We estimated visually t...

  19. 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....

  20. Trophic and individual efficiencies of size-structured communities

    DEFF Research Database (Denmark)

    Andersen, Ken Haste; Beyer, Jan; Lundberg, P.

    2009-01-01

    Individual and trophic efficiencies of size-structured communities are derived from mechanistically based principles at the individual level. The derivations are relevant for communities with a size-based trophic structure, i.e. where trophic level is strongly correlated with individual size...... as in many aquatic systems. The derivations are used to link Lindeman's trophic theory and trophic theory based on average individuals with explicit individual-level size spectrum theory. The trophic efficiency based on the transfer of mass between trophic levels through predator-prey interactions...

  1. Chemical warfare in freshwater. Allelpathic effects of macrophytes on phytoplankton

    NARCIS (Netherlands)

    Mulderij, G.

    2006-01-01

    Aquatic macrophytes can excrete chemical substances into their enviroment and these compounds may inhibit the growth of phytoplankton. This process is defined as allelopathy: one organism has effects on another via the excretion of a (mixture of) chemical substance(s). With laboratory and field expe

  2. Experiments on growth interactions between two invasive macrophyte species

    NARCIS (Netherlands)

    Barrat-Segretain, M-H.; Elger, A.F.

    2004-01-01

    The success of invasive species has been attributed to the ability to displace other species by direct competition. We studied growth and possible competition between the two macrophyte species Elodea nuttallii and E. canadensis, because the former has been observed to replace the latter in the

  3. Macrophytes in estuarine gradients: flow through flexible vegetation

    NARCIS (Netherlands)

    Dijkstra, J.T.

    2012-01-01

    Aquatic plants –or macrophytes- are an important part of coastal, estuarine and freshwater ecosystems worldwide, both from an ecological and an engineering viewpoint. Their meadows provide a wide range of ecosystem services: forming a physical protection of the shoreline, enhancing water quality and

  4. African Journal of Science and Technology (AJST) MACROPHYTES ...

    African Journals Online (AJOL)

    opiyo

    MACROPHYTES ET GROUPEMENTS VÉGÉTAUX AQUATIQUES. ET AMPHIBIES DE LA ... plaine d'inondation indique que le marnage demeure important et la salinité des terres reste encore élevée. ..... The Journal of Ecology, vol. 54, n° 3 ...

  5. Herbivory on freshwater and marine macrophytes : A review and perspective

    NARCIS (Netherlands)

    Bakker, Elisabeth S.; Wood, Kevin A.; Pages, Jordi F.; Veen, G. F. (Ciska); Christianen, Marjolijn J. A.; Santamaria, Luis; Nolet, Bart A.; Hilt, Sabine

    2016-01-01

    Until the 1990s, herbivory on aquatic vascular plants was considered to be of minor importance, and the predominant view was that freshwater and marine macrophytes did not take part in the food web: their primary fate was the detritivorous pathway. In the last 25 years, a substantial body of

  6. Herbivory on freshwater and marine macrophytes : A review and perspective

    NARCIS (Netherlands)

    Bakker, Elisabeth S.; Wood, Kevin A.; Pages, Jordi F.; Veen, G. F. (Ciska); Christianen, Marjolijn J. A.; Santamaria, Luis; Nolet, Bart A.; Hilt, Sabine

    2016-01-01

    Until the 1990s, herbivory on aquatic vascular plants was considered to be of minor importance, and the predominant view was that freshwater and marine macrophytes did not take part in the food web: their primary fate was the detritivorous pathway. In the last 25 years, a substantial body of evidenc

  7. Species pool versus site limitations of macrophytes in urban waters

    DEFF Research Database (Denmark)

    Vermonden, K.; Leuven, R.S.E.W.; van der Velde, G.

    2010-01-01

    Biodiversity in urban areas is affected by a multitude of stressors. In addition to physico-chemical stress factors, the native regional species pool can be greatly reduced in highly urbanized landscapes due to area loss and fragmentation. In this study, we investigated how macrophyte composition...

  8. Chemical warfare in freshwater. Allelpathic effects of macrophytes on phytoplankton

    NARCIS (Netherlands)

    Mulderij, G.

    2006-01-01

    Aquatic macrophytes can excrete chemical substances into their enviroment and these compounds may inhibit the growth of phytoplankton. This process is defined as allelopathy: one organism has effects on another via the excretion of a (mixture of) chemical substance(s). With laboratory and field

  9. Community structure changes of macrobenthos in the South Yellow Sea

    Institute of Scientific and Technical Information of China (English)

    ZHANG Junlong; XU Fengshan; LIU Ruiyu

    2012-01-01

    The ecological environment in the Yellow Sea has changed greatly from the 1950s to 1990s and this has had significant impact on marine organisms.In this study,data on soft-sediment macrobenthos occurring in depths from 25 m to 81 m in the South Yellow Sea were used to compare changes in community structure.The agglomerative classification (CLUSTER) and multidimensional scaling (MDS) methods were applied.Five communities were recognized by cluster analysis:1.The Yellow Sea Cold Water Mass community dominated by cold water species,which changed slightly in species composition since the 1950s; 2.The mixed community with the coexistence of cold water species and warm water species,as had been reported previously; 3.The polychaete-dominated eurythermal community in which the composition changed considerably as some dominant species disappeared or decreased; 4.The Changjiang (Yangtze) River Estuarine community,with some typical estuarine species; 5.The community affected by the Yellow Sea Warm Current.The greatest change occurred in the coastal area,which indicated that the change may be caused by human activities.Macrobenthos in the central region remained almost unchanged,particularly the cold water species shielded by the Yellow Sea Cold Water Mass.The depth,temperature and median grain size of sediments were important factors affecting the distributions of macrobenthos in the South Yellow Sea.

  10. Is interspecific competition a major structuring force in animal communities?

    Directory of Open Access Journals (Sweden)

    P. A. J. Ryke

    1987-03-01

    Full Text Available Until recently the view that competition is the dominant ecological interaction was the prevailing one. Interspecific competition was widely regarded as a principal mechanism in determining community structure and organization and thus the distribution and abundance of species. The volume of literature that provides indirect evidence in favour of competition (observational approach greatly exceeds the number of studies that provide direct evidence (experimental approach. In part for this reason the importance of competition in community ecology is questioned by some ecologists. The strongest evidence for competition is derived from controlled field experiments which manipulate the abundancies of putative competitor species. It is stressed that to be able to study competition in the field and to test its theories, interaction coefficients have to be measured. In community studies the question should be asked how important competition, relative to other processes, is. A mechanistic perspective could be a powerful heuristic tool for community ecologists.

  11. Microbial Community Structure in Relation to Water Quality in ...

    Science.gov (United States)

    Weeks Bay is a shallow, microtidal, eutrophic sub-estuary of Mobile Bay, AL. High watershed nutrient inputs to the estuary contribute to a eutrophic condition characterized by frequent summertime diel-cycling hypoxia and dissolved oxygen (DO) oversaturation. Spatial and seasonal variability of microbial communities that contribute to estuarine ecosystem metabolism were characterized using high-throughput DNA sequencing. Surface water samples were collected from spring to fall at three sites along a transect of Weeks Bay from the Fish River to Mobile Bay. Water samples were analyzed for physiochemical properties and were also filtered onto Sterivex filters for DNA extraction. Genes for 16S rRNA and 18S rRNA were amplified and sequenced according to Earth Microbiome Project protocols. Sequences were assembled into contigs and clustered into OTUs with mothur using the Silva database. The prokaryotes were dominated by Cyanobacteria, Actinobacteria, and Spartobacteria, whereas the eukaryotes were dominated by Bacillariophyta (diatoms). Multivariate statistical analysis of microbial community composition and environmental data showed that Bacteria, Archaea and Eukaryota were clustered by season. BEST analysis by station showed that prokaryotic community structure was associated with salinity and CDOM (Rho=0.924), whereas eukaryotic community structure was most associated with salinity (Rho=0.846). Prokaryotic community structure within seasons was associated with six

  12. Bootstrap Percolation on Complex Networks with Community Structure

    CERN Document Server

    Chong, Wu; Rui, Zhang; Liujun, Chen; Jiawei, Chen; Xiaobin, Li; Yanqing, Hu

    2014-01-01

    Real complex networks usually involve community structure. How innovation and new products spread on social networks which have internal structure is a practically interesting and fundamental question. In this paper we study the bootstrap percolation on a single network with community structure, in which we initiate the bootstrap process by activating different fraction of nodes in each community. A previously inactive node transfers to active one if it detects at least $k$ active neighbors. The fraction of active nodes in community $i$ in the final state $S_i$ and its giant component size $S_{gci}$ are theoretically obtained as functions of the initial fractions of active nodes $f_i$. We show that such functions undergo multiple discontinuous transitions; The discontinuous jump of $S_i$ or $S_{gci}$ in one community may trigger a simultaneous jump of that in the other, which leads to multiple discontinuous transitions for the total fraction of active nodes $S$ and its associated giant component size $S_{gc}$...

  13. Colonization of leaf litter of two aquatic macrophytes, Mayaca fluviatilis Aublet and Salvinia auriculata Aublet by aquatic macroinvertebrates in a tropical reservoir

    Directory of Open Access Journals (Sweden)

    Marcia Cristina de Paula

    2011-04-01

    Full Text Available Decomposition and colonization of S. auriculata and M. fluviatilis by macroinvertebrates were analyzed during 40 days to determine whether differences existed on colonization by aquatic macroinvertebrates of two macrophytes with distinct habits (submerged versus fluctuant. Leaf litter of S. auriculata and M. fluviatilis were incubated in 24 litter bags (12 of each species, in a small reservoir surrounded by a cerrado fragment with low level of anthropic impact. After 10, 20, 30 and 40 days, the litter bags were removed and aquatic macroinvertebrates community was analyzed. Two hundred twenty macroinvertebrates were associated with S. auriculata and 261 were associated with M. fluviatilis, identified in 24 taxa. Both macrophyte species were colonized mainly by macroinvertebrate predators. Ablabesmyia with predator and collector food mechanisms was present in all sampling. The data showed an expressive increase of abundance during the process of decomposition and a decrease at the end of the experiment, in both macrophytes. Cluster analysis permitted inference that the colonization of the leaf liter by macroinvertebrates was determinated by incubation time of leaf litter not by the habit of macrophytes (submerged or fluctuant.

  14. Biological interactions in the co-occurrence of Eichhornia azurea and free-floating macrophytes - DOI: 10.4025/actascibiolsci.v31i4.5577

    Directory of Open Access Journals (Sweden)

    Sidinei Magela Thomaz

    2009-08-01

    Full Text Available The dynamic of plant communities is strongly influenced by biological interactions. We studied the effects of Eichhornia azurea on the growth of the free-floating macrophytes Eichhornia crassipes, Salvinia minima, Salvinia auriculata and Limnobium laevigatum. The experiments were carried out in three lakes of the upper Paraná river floodplain. We used 0.5 m side squares where these species grew for 11 days (S. auriculata and L. laevigatum and 17 days (E. crassipes and S. minima, in the presence and absence of E. azurea. There were no significant differences between the relative growth rates of macrophytes growing in the absence and presence of E. azurea. The relative interaction index showed the existence of competition between E. azurea and L. laevigatum, and neutrality with the other three species. There was no evidence of facilitation related to the improvement of physico-chemistry characteristics that could enhance macrophytes growth. However, we do not discard a ‘mechanical’ facilitation between E. azurea, which offers protection against wind and waves, and the other species of macrophytes

  15. Geochemical Analyses of Macrophytes (Potamogeton sp.) and ancient DNA from Lake Karakul, Tajikistan

    Science.gov (United States)

    Heinecke, Liv; Epp, Laura S.; Mischke, Steffen; Reschke, Maria; Stoof-Leichsenring, Kathleen; Rajabov, Ilhomjon; Herzschuh, Ulrike

    2016-04-01

    Mountain ecosystems are very sensitive towards changes in moisture and temperature and therefore most likely to be affected by climate change. To be able to get a closer insight into the alpine system of the Pamir Mountains, a 11.25 m long core was retrieved from the eastern basin of Lake Karakul (3,929 m asl), Tajikistan, in 2012. In order to gain insights into changes in the paleo-productivity of Lake Karakul over the last 29 cal kyrs BP, we investigate temporal gradients of elemental content (TOC, TN) and stable isotopes (δ13C, δ15N) of macrophyte remains (Potamogeton sp.) and plant communities obtained from ancient sedimentary DNA along the core. For the geochemical analyses we make use of the ability of submerged macrophytes, such as Potamogeton, to use HCO3- for photosynthesis in times of CO2 shortage and implement our results in a transfer function for paleo-productivity inferences. No data are available from 20 to 7 cal kyrs BP as no macrophyte remains are preserved, indicating unfavourable conditions for plant growth at the coring site or poor preservation conditions during this time. Biogeochemical analyses show significant variations from core base until approx. 20 cal kyrs BP with TOCPotamogeton 25-45 %, TNPotamogeton 0.5 % - 1.5 %, δ13CPotamogeton below -9 ‰ and δ15NPotamogeton of below 3.5 ‰ suggesting a cooler climate and reflecting the last glacial maximum. Sediments in the upper 4.5 m (approx. 6.7 cal kyrs BP) are rich in macrophyte remains. TOCPotamogeton and TNPotamogeton values from this part of the core are higher, and an enrichment of heavier isotopes with δ13CPotamogeton up to -7 ‰ and δ15NPotamogeton up to 6 ‰ indicating a higher productivity within the lake due to more favourable conditions for macrophyte growths on the lake floor. We assume shifts towards a warmer climate and changes in lake level as the dominating causes. Ancient sedimentary DNA was extracted from selected sediment slices and a metabarcoding approach (using

  16. 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.

  17. The corporate elite community structure of global capitalism

    NARCIS (Netherlands)

    E.M. Heemskerk; F.W. Takes

    2015-01-01

    A key debate on the merits and consequences of globalisation asks to what extent we have moved to a multipolar global political economy. Here we investigate this issue through the properties and topologies of corporate elite networks and ask: what is the community structure of the global corporate e

  18. 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....

  19. Community structure and Distribution of Phytomacrofauna in Iyagbe ...

    African Journals Online (AJOL)

    ADOWIE PERE

    Community structure and Distribution of Phytomacrofauna in Iyagbe Lagoon,. Southwest, Nigeria ... by site specific factors particularly with respect to depth of study stations as shown by correlation .... Samples for the analysis of other physico-chemical properties of ..... water quality relations in a tropical coastal. Ecosystem: ...

  20. Multilabel user classification using the community structure of online networks

    Science.gov (United States)

    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. PMID:28278242

  1. A framework for solving ill-structured community problems

    Science.gov (United States)

    Keller, William Cotesworth

    A multifaceted protocol for solving ill-structured community problems has been developed. It embodies the lessons learned from the past by refining and extending features of previous models from the systems thinkers, and the fields of behavioral decision making and creative problem solving. The protocol also embraces additional features needed to address the unique aspects of community decision situations. The essential elements of the protocol are participants from the community, a problem-solving process, a systems picture, a facilitator, a modified Delphi method of communications, and technical expertise. This interdisciplinary framework has been tested by a quasi experiment with a real world community problem (the high cost of electrical power on Long Island, NY). Results indicate the protocol can enable members of the community to understand a complicated, ill-structured problem and guide them to action to solve the issue. However, the framework takes time (over one year in the test case) and will be inappropriate for crises where quick action is needed.

  2. Correlations between community structure and link formation in complex networks.

    Directory of Open Access Journals (Sweden)

    Zhen Liu

    Full Text Available BACKGROUND: Links in complex networks commonly represent specific ties between pairs of nodes, such as protein-protein interactions in biological networks or friendships in social networks. However, understanding the mechanism of link formation in complex networks is a long standing challenge for network analysis and data mining. METHODOLOGY/PRINCIPAL FINDINGS: Links in complex networks have a tendency to cluster locally and form so-called communities. This widely existed phenomenon reflects some underlying mechanism of link formation. To study the correlations between community structure and link formation, we present a general computational framework including a theory for network partitioning and link probability estimation. Our approach enables us to accurately identify missing links in partially observed networks in an efficient way. The links having high connection likelihoods in the communities reveal that links are formed preferentially to create cliques and accordingly promote the clustering level of the communities. The experimental results verify that such a mechanism can be well captured by our approach. CONCLUSIONS/SIGNIFICANCE: Our findings provide a new insight into understanding how links are created in the communities. The computational framework opens a wide range of possibilities to develop new approaches and applications, such as community detection and missing link prediction.

  3. Oceanographic structure drives the assembly processes of microbial eukaryotic communities.

    Science.gov (United States)

    Monier, Adam; Comte, Jérôme; Babin, Marcel; Forest, Alexandre; Matsuoka, Atsushi; Lovejoy, Connie

    2015-03-17

    Arctic Ocean microbial eukaryote phytoplankton form subsurface chlorophyll maximum (SCM), where much of the annual summer production occurs. This SCM is particularly persistent in the Western Arctic Ocean, which is strongly salinity stratified. The recent loss of multiyear sea ice and increased particulate-rich river discharge in the Arctic Ocean results in a greater volume of fresher water that may displace nutrient-rich saltier waters to deeper depths and decrease light penetration in areas affected by river discharge. Here, we surveyed microbial eukaryotic assemblages in the surface waters, and within and below the SCM. In most samples, we detected the pronounced SCM that usually occurs at the interface of the upper mixed layer and Pacific Summer Water (PSW). Poorly developed SCM was seen under two conditions, one above PSW and associated with a downwelling eddy, and the second in a region influenced by the Mackenzie River plume. Four phylogenetically distinct communities were identified: surface, pronounced SCM, weak SCM and a deeper community just below the SCM. Distance-decay relationships and phylogenetic structure suggested distinct ecological processes operating within these communities. In the pronounced SCM, picophytoplanktons were prevalent and community assembly was attributed to water mass history. In contrast, environmental filtering impacted the composition of the weak SCM communities, where heterotrophic Picozoa were more numerous. These results imply that displacement of Pacific waters to greater depth and increased terrigenous input may act as a control on SCM development and result in lower net summer primary production with a more heterotroph dominated eukaryotic microbial community.

  4. Changes in soil bacterial community structure with increasing disturbance frequency.

    Science.gov (United States)

    Kim, Mincheol; Heo, Eunjung; Kang, Hojeong; Adams, Jonathan

    2013-07-01

    Little is known of the responsiveness of soil bacterial community structure to disturbance. In this study, we subjected a soil microcosm to physical disturbance, sterilizing 90 % of the soil volume each time, at a range of frequencies. We analysed the bacterial community structure using 454 pyrosequencing of the 16S rRNA gene. Bacterial diversity was found to decline with the increasing disturbance frequencies. Total bacterial abundance was, however, higher at intermediate and high disturbance frequencies, compared to low and no-disturbance treatments. Changing disturbance frequency also led to changes in community composition, with changes in overall species composition and some groups becoming abundant at the expense of others. Some phylogenetic groups were found to be relatively more disturbance-sensitive or tolerant than others. With increasing disturbance frequency, phylogenetic species variability (an index of community composition) itself became more variable from one sample to another, suggesting a greater role of chance in community composition. Compared to the tightly clustered community of the original undisturbed soil, in all the aged disturbed soils the lists of most abundant operational taxonomic units (OTUs) in each replicate were very different, suggesting a possible role of stochasticity in resource colonization and exploitation in the aged and disturbed soils. For example, colonization may be affected by whichever localized concentrations of bacterial populations happen to survive the last disturbance and be reincorporated in abundance into each pot. Overall, it appears that the soil bacterial community is very sensitive to physical disturbance, losing diversity, and that certain groups have identifiable 'high disturbance' vs. 'low disturbance' niches.

  5. Fishing degrades size structure of coral reef fish communities.

    Science.gov (United States)

    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

  6. Phylogenetic community structure during succession: evidence from three Neotropical forest sites

    NARCIS (Netherlands)

    Letcher, S.G.; Chazdon, R.L.; Andrade, A.; Bongers, F.; Breugel, van M.; Finegan, B.; Laurance, S.G.; Mesquita, R.; Martinez-Ramos, M.; Williamson, G.B.

    2012-01-01

    The phylogenetic structure of communities can reveal forces shaping community assembly, but the vast majority of work on phylogenetic community structure has been conducted in mature ecosystems. Here, we present an analysis of the phylogenetic structure of three Neotropical rain forest communities u

  7. Router-level community structure of the Internet Autonomous Systems

    CERN Document Server

    Beiró, Mariano G; Alvarez-Hamelin, J Ignacio

    2015-01-01

    The Internet is composed of routing devices connected between them and organized into independent administrative entities: the Autonomous Systems. The existence of different types of Autonomous Systems (like large connectivity providers, Internet Service Providers or universities) together with geographical and economical constraints, turns the Internet into a complex modular and hierarchical network. This organization is reflected in many properties of the Internet topology, like its high degree of clustering and its robustness. In this work, we study the modular structure of the Internet router-level graph in order to assess to what extent the Autonomous Systems satisfy some of the known notions of community structure. We show that the modular structure of the Internet is much richer than what can be captured by the current community detection methods, which are severely affected by resolution limits and by the heterogeneity of the Autonomous Systems. Here we overcome this issue by using a multiresolution d...

  8. Climate and species richness predict the phylogenetic structure of African mammal communities.

    Science.gov (United States)

    Kamilar, Jason M; Beaudrot, Lydia; Reed, Kaye E

    2015-01-01

    We have little knowledge of how climatic variation (and by proxy, habitat variation) influences the phylogenetic structure of tropical communities. Here, we quantified the phylogenetic structure of mammal communities in Africa to investigate how community structure varies with respect to climate and species richness variation across the continent. In addition, we investigated how phylogenetic patterns vary across carnivores, primates, and ungulates. We predicted that climate would differentially affect the structure of communities from different clades due to between-clade biological variation. We examined 203 communities using two metrics, the net relatedness (NRI) and nearest taxon (NTI) indices. We used simultaneous autoregressive models to predict community phylogenetic structure from climate variables and species richness. We found that most individual communities exhibited a phylogenetic structure consistent with a null model, but both climate and species richness significantly predicted variation in community phylogenetic metrics. Using NTI, species rich communities were composed of more distantly related taxa for all mammal communities, as well as for communities of carnivorans or ungulates. Temperature seasonality predicted the phylogenetic structure of mammal, carnivoran, and ungulate communities, and annual rainfall predicted primate community structure. Additional climate variables related to temperature and rainfall also predicted the phylogenetic structure of ungulate communities. We suggest that both past interspecific competition and habitat filtering have shaped variation in tropical mammal communities. The significant effect of climatic factors on community structure has important implications for the diversity of mammal communities given current models of future climate change.

  9. Climate and Species Richness Predict the Phylogenetic Structure of African Mammal Communities

    Science.gov (United States)

    Kamilar, Jason M.; Beaudrot, Lydia; Reed, Kaye E.

    2015-01-01

    We have little knowledge of how climatic variation (and by proxy, habitat variation) influences the phylogenetic structure of tropical communities. Here, we quantified the phylogenetic structure of mammal communities in Africa to investigate how community structure varies with respect to climate and species richness variation across the continent. In addition, we investigated how phylogenetic patterns vary across carnivores, primates, and ungulates. We predicted that climate would differentially affect the structure of communities from different clades due to between-clade biological variation. We examined 203 communities using two metrics, the net relatedness (NRI) and nearest taxon (NTI) indices. We used simultaneous autoregressive models to predict community phylogenetic structure from climate variables and species richness. We found that most individual communities exhibited a phylogenetic structure consistent with a null model, but both climate and species richness significantly predicted variation in community phylogenetic metrics. Using NTI, species rich communities were composed of more distantly related taxa for all mammal communities, as well as for communities of carnivorans or ungulates. Temperature seasonality predicted the phylogenetic structure of mammal, carnivoran, and ungulate communities, and annual rainfall predicted primate community structure. Additional climate variables related to temperature and rainfall also predicted the phylogenetic structure of ungulate communities. We suggest that both past interspecific competition and habitat filtering have shaped variation in tropical mammal communities. The significant effect of climatic factors on community structure has important implications for the diversity of mammal communities given current models of future climate change. PMID:25875361

  10. A seed-expanding method based on random walks for community detection in networks with ambiguous community structures

    Science.gov (United States)

    Su, Yansen; Wang, Bangju; Zhang, Xingyi

    2017-02-01

    Community detection has received a great deal of attention, since it could help to reveal the useful information hidden in complex networks. Although most previous modularity-based and local modularity-based community detection algorithms could detect strong communities, they may fail to exactly detect several weak communities. In this work, we define a network with clear or ambiguous community structures based on the types of its communities. A seed-expanding method based on random walks is proposed to detect communities for networks, especially for the networks with ambiguous community structures. We identify local maximum degree nodes, and detect seed communities in a network. Then, the probability of a node belonging to each community is calculated based on the total probability model and random walks, and each community is expanded by repeatedly adding the node which is most likely to belong to it. Finally, we use the community optimization method to ensure that each node is in a community. Experimental results on both computer-generated and real-world networks demonstrate that the quality of the communities detected by the proposed algorithm is superior to the- state-of-the-art algorithms in the networks with ambiguous community structures.

  11. Aquatic macrophytes as feeding site for small fishes in the Rosana Reservoir, Paranapanema River, southeastern Brazil.

    Science.gov (United States)

    Casatti, L; Mendes, H F; Ferreira, K M

    2003-05-01

    In the present investigation we studied the feeding habits of the fishes associated with aquatic macrophytes in the Rosana Reservoir, southeastern Brazil. Twenty fish species were collected during four field trips, regularly distributed across the dry and wet seasons. Focal snorkeling observations of the fishes were made over a total of six hours. Nine species were present in abundances of more than 1% and, therefore, had their feeding habits analyzed. Hemigrammus marginatus, Roeboides paranensis, Hyphessobrycon eques, Astyanax altiparanae, Serrasalmus spilopleura, and Bryconamericus stramineus were predominantly invertivores, with predominance of aquatic insects (Diptera, Ephemeroptera, and Trichoptera immatures) among their food items. The predominantly algivores were Apareiodon affinis, Serrapinnus notomelas, and Satanoperca pappaterra, with high frequency of filamentous blue-green algae, diatoms, clorophyts, and periderm. The different microhabitat exploitation plus diet composition suggests partitioning of resources and absence of food competition among the most representative fish species in the studied community, indicating the importance of the naturalistic approach to fish ecology studies.

  12. Effects of pulsed atrazine exposures on autotrophic community structure, biomass, and production in field-based stream mesocosms.

    Science.gov (United States)

    King, Ryan S; Brain, Richard A; Back, Jeffrey A; Becker, Christopher; Wright, Moncie V; Djomte, Valerie Toteu; Scott, W Casan; Virgil, Steven R; Brooks, Bryan W; Hosmer, Alan J; Chambliss, C Kevin

    2016-03-01

    The authors performed a multiple-pulsed atrazine experiment to measure responses of autotrophic endpoints in outdoor stream mesocosms. The experiment was designed to synthetically simulate worst-case atrazine chemographs from streams in agricultural catchments to achieve 60-d mean concentrations of 0 μg/L (control), 10 μg/L, 20 μg/L, and 30 μg/L. The authors dosed triplicate streams with pulses of 0 μg/L, 50 μg/L, 100 μg/L, and 150 μg/L atrazine for 4 d, followed by 7 d without dosing. This 11-d cycle occurred 3 times, followed by a recovery (untreated) period from day 34 to day 60. Mean ± standard error 60-d atrazine concentrations were 0.07 ± 0.03 μg/L, 10.7 ± 0.05 μg/L, 20.9 ± 0.24 μg/L, and 31.0 ± 0.17 μg/L for the control, 10-μg/L, 20-μg/L, and 30-μg/L treatments, respectively. Multivariate analyses revealed that periphyton and phytoplankton community structure did not differ among treatments on any day of the experiment, including during the atrazine pulses. Control periphyton biomass in riffles was higher immediately following the peak of the first atrazine pulse and remained slightly higher than some of the atrazine treatments on most days through the peak of the last pulse. However, periphyton biomass was not different among treatments at the end of the present study. Phytoplankton biomass was not affected by atrazine. Metaphyton biomass in pools was higher in the controls near the midpoint of the present study and remained higher on most days for the remainder of the study. Ceratophyllum demersum, a submersed macrophyte, biomass was higher in controls than in 20-μg/L and 30-μg/L treatments before pulse 3 but was not different subsequent to pulse 3 through the end of the present study. Maximum daily dissolved oxygen (DO, percentage of saturation) declined during each pulse in approximate proportion to magnitude of dose but rapidly converged among treatments after the third pulse. However

  13. Community structure and population genetics of Eastern Mediterranean polychaetes

    Directory of Open Access Journals (Sweden)

    Giorgos eChatzigeorgiou

    2014-10-01

    Full Text Available Species and genetic diversity are often found to co-vary since they are influenced by external factors in similar ways. In this paper, we analyse the genetic differences of the abundant polychaete Hermodice carunculata (Pallas, 1776 during two successive years at two locations in northern Crete (Aegean Sea and compare them to other populations in the Mediterranean Sea and the Atlantic Ocean. The genetic analysis is combined with an analysis of ecological divergence of the total polychaete community structure (beta diversity at these locations. The phylogenetic analysis of all included H. carunculata populations revealed two main clades, one exclusively found in the Mediterranean and a second occurring in both the Mediterranean and the Atlantic. Genetic diversity indices reveal unexpectedly high differences between the two Cretan populations, despite the absence of apparent oceanographic barriers. A similarly high divergence, represented by a high beta diversity index, was observed between the polychaete communities at the two locations. This comparatively high divergence of the genetic structure of a dominant species and the total polychaete community might be explained by the strong influence of local environmental factors as well as inter-specific interactions between the dominance of a single species and the members of the community.

  14. Microbial community structure of Arctic seawater as revealed by pyrosequencing

    Institute of Scientific and Technical Information of China (English)

    LI Yang; WANG Zhen; LIN Xuezheng

    2016-01-01

    This study aimed to determine the microbial community structure of seawater in (ICE-1) and out (FUBIAO) of the pack ice zone in the Arctic region. Approximate 10 L seawater was filtrated by 0.2 μm Whatman nuclepore filters and the environmental genomic DNA was extracted. We conducted a detailed census of microbial communities by pyrosequencing. Analysis of the microbial community structures indicated that these two samples had high bacterial, archaeal and eukaryotic diversity. Proteobacteria and Bacteroidetes were the two dominant members of the bacterioplankton community in both samples, and their relative abundance were 51.29% and 35.39%, 72.95%and 23.21%, respectively. Euryarchaeota was the most abundant archaeal phylum, and the relative abundance was nearly up to 100% in FUBIAO and 60% in ICE-1. As for the eukaryotes, no_rank_Eukaryota, Arthropoda and no_rank_Metazoa were the most abundant groups in Sample FUBIAO, accounting for 85.29% of the total reads. The relative abundance of the most abundant phylum in Sample ICE-1, no_rank_Eukaryota and no_rank_Metazoa, was up to 90.69% of the total reads. Alphaproteobacteria, Flavobacteria and Gammaproteobacteria were the top three abundant classes in the two samples at the bacterial class level. There were also differences in the top ten abundant bacterial, archaeal and eukaryotic OTUs at the level of 97% similarity between the two samples.

  15. Temporal and habitat distribution of macrophytes in lowland eutrophic reservoir Gruža in Serbia

    OpenAIRE

    Topuzović, Marina; Pavlović, Dragana; Ostojić, Aleksandar

    2016-01-01

    Background and Purpose: The research in this paper are based on the study of the distribution in time and space of macrophytes along the different parts of shoreline of Gruža Reservoir and emphasize the importance of establishing relations between distribution, diversity and mass of macrophytes and the ecological conditions of the environment. Development diversity of macrophytes needs to be constantly monitored and their regulation is necessary for Reservoir conservation, especially because...

  16. Temporal and spatial distribution of macrophytes in the Gruža Reservoir (Serbia)

    OpenAIRE

    Topuzović Marina; Pavlović Dragana; Ostojić A.

    2009-01-01

    A survey of aquatic macrophytes in the Gruža Reservoir (Serbia) was conducted during the period 2007-2008. Detailed data on the actual condition of macrophytes were established and compared between four parts of the reservoir. The distributions of most aquatic macrophytes of the Gruža Reservoir are heterogeneous, with different values of the MMT and MMO indices and low values of the distribution ratio. Quantitative analysis indicates that the greatest diversity and abundance of species can be...

  17. Temporal and habitat distribution of macrophytes in lowland eutrophic reservoir Gruža in Serbia

    OpenAIRE

    Topuzović, Marina; Pavlović, Dragana; Ostojić, Aleksandar

    2016-01-01

    Background and Purpose: The research in this paper are based on the study of the distribution in time and space of macrophytes along the different parts of shoreline of Gruža Reservoir and emphasize the importance of establishing relations between distribution, diversity and mass of macrophytes and the ecological conditions of the environment. Development diversity of macrophytes needs to be constantly monitored and their regulation is necessary for Reservoir conservation, especially because ...

  18. Invasive crayfish threaten the development of submerged macrophytes in lake restoration.

    Directory of Open Access Journals (Sweden)

    Jessica E M van der Wal

    Full Text Available Submerged macrophytes enhance water transparency and aquatic biodiversity in shallow water ecosystems. Therefore, the return of submerged macrophytes is the target of many lake restoration projects. However, at present, north-western European aquatic ecosystems are increasingly invaded by omnivorous exotic crayfish. We hypothesize that invasive crayfish pose a novel constraint on the regeneration of submerged macrophytes in restored lakes and may jeopardize restoration efforts. We experimentally investigated whether the invasive crayfish (Procambarus clarkii Girard affects submerged macrophyte development in a Dutch peat lake where these crayfish are expanding rapidly. Seemingly favourable abiotic conditions for macrophyte growth existed in two 0.5 ha lake enclosures, which provided shelter and reduced turbidity, and in one lake enclosure iron was added to reduce internal nutrient loading, but macrophytes did not emerge. We transplanted three submerged macrophyte species in a full factorial exclosure experiment, where we separated the effect of crayfish from large vertebrates using different mesh sizes combined with a caging treatment stocked with crayfish only. The three transplanted macrophytes grew rapidly when protected from grazing in both lake enclosures, demonstrating that abiotic conditions for growth were suitable. Crayfish strongly reduced biomass and survival of all three macrophyte species while waterfowl and fish had no additive effects. Gut contents showed that crayfish were mostly carnivorous, but also consumed macrophytes. We show that P. clarkii strongly inhibit macrophyte development once favourable abiotic conditions for macrophyte growth are restored. Therefore, expansion of invasive crayfish poses a novel threat to the restoration of shallow water bodies in north-western Europe. Prevention of introduction and spread of crayfish is urgent, as management of invasive crayfish populations is very difficult.

  19. Community structure benefits the fixation of cooperation under strong selection

    CERN Document Server

    Wu, Zhi-Xi; Yang, Han-Xin

    2014-01-01

    Recent empirical studies suggest that heavy-tailed distributions of human activities are universal in real social dynamics [Muchnik, \\emph{et al.}, Sci. Rep. \\textbf{3}, 1783 (2013)]. On the other hand, community structure is ubiquitous in biological and social networks [M.~E.~J. Newman, Nat. Phys. \\textbf{8}, 25 (2012)]. Motivated by these facts, we here consider the evolutionary Prisoner's dilemma game taking place on top of a real social network to investigate how the community structure and the heterogeneity in activity of individuals affect the evolution of cooperation. In particular, we account for a variation of the birth-death process (which can also be regarded as a proportional imitation rule from social point of view) for the strategy updating under both weak- and strong-selection (meaning the payoffs harvested from games contribute either slightly or heavily to the individuals' performance). By implementing comparative studies, where the players are selected either randomly or in terms of their ac...

  20. Dynamical evolution of the community structure of complex earthquake network

    CERN Document Server

    Abe, Sumiyoshi

    2012-01-01

    Earthquake network is known to be complex in the sense that it is scale-free, small-world, hierarchically organized and assortatively mixed. Here, the time evolution of earthquake networks is analyzed around main shocks in the context of the community structure. It is found that the maximum of the modularity measure quantifying existence of communities exhibits a peculiar behavior: its maximum value stays at a large value before a main shock, suddenly drops to a small values at the main shock, and then increases to relax to a large value again relatively slowly. In this way, a main shock is characterized in the language of theory of complex networks. The result is also interpreted in terms of the clustering structure of the earthquake network.

  1. Aquatic macrophyte diversity of the Pantanal wetland and upper basin.

    Science.gov (United States)

    Pott, V J; Pott, A; Lima, L C P; Moreira, S N; Oliveira, A K M

    2011-04-01

    This is a short review of the state of the art concerning diversity of aquatic macrophytes and the main aquatic vegetation types in the Brazilian Pantanal wetland and upper watershed. There are ca. 280 species of aquatic macrophytes on the Pantanal floodplain, with scarce endemism. On the upper watershed, Cerrado wetlands (veredas) and limestone springs have a distinct flora from the Pantanal, with twice the species richness. As a representative case of aquatic habitats influenced by river flood, some primary data are presented for the Pantanal Matogrossense National Park and associated Acurizal Preserve, analysing the floristic similarity among aquatic vegetation types. We comment on problems of conservation and observe that Panicum elephantipes Nees is one of the few natives to compete with the invasive Urochloa arrecta (Hack. ex T. Durand & Schinz) Morrone & Zuloaga.

  2. Aquatic macrophyte diversity of the Pantanal wetland and upper basin

    Directory of Open Access Journals (Sweden)

    VJ. Pott

    Full Text Available This is a short review of the state of the art concerning diversity of aquatic macrophytes and the main aquatic vegetation types in the Brazilian Pantanal wetland and upper watershed. There are ca. 280 species of aquatic macrophytes on the Pantanal floodplain, with scarce endemism. On the upper watershed, Cerrado wetlands (veredas and limestone springs have a distinct flora from the Pantanal, with twice the species richness. As a representative case of aquatic habitats influenced by river flood, some primary data are presented for the Pantanal Matogrossense National Park and associated Acurizal Preserve, analysing the floristic similarity among aquatic vegetation types. We comment on problems of conservation and observe that Panicum elephantipes Nees is one of the few natives to compete with the invasive Urochloa arrecta (Hack. ex T. Durand & Schinz Morrone & Zuloaga.

  3. 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.

  4. Patterns of the aquatic macrophyte cover in Cachoeira Dourada Reservoir (GO-MG

    Directory of Open Access Journals (Sweden)

    L. M Bini

    Full Text Available The relationship between the aquatic macrophyte cover in upper segments of tributaries and this cover in these tributaries but near the reservoir's main body was tested. Sixteen taxa belonging to 12 families of aquatic macrophytes were recorded in Cachoeira Dourada Reservoir. The most frequent species were Eichhornia azurea (frequency of occurrence = 92%; n = 37 sites and E. crassipes (44%. Upper segments of the tributaries were the main areas colonized by these aquatic macrophytes. The positive relationship between the aquatic macrophyte cover between the upper and lower segments of tributaries indicates the importance of dispersion in the colonization of the arms and the reservoir's main body.

  5. Patterns of the aquatic macrophyte cover in Cachoeira Dourada Reservoir (GO-MG).

    Science.gov (United States)

    Bini, L M; Oliveira, L G; Souza, D C; Carvalho, P; Pinto, M P

    2005-02-01

    The relationship between the aquatic macrophyte cover in upper segments of tributaries and this cover in these tributaries but near the reservoir's main body was tested. Sixteen taxa belonging to 12 families of aquatic macrophytes were recorded in Cachoeira Dourada Reservoir. The most frequent species were Eichhornia azurea (frequency of occurrence=92%; n=37 sites) and E. crassipes (44%). Upper segments of the tributaries were the main areas colonized by these aquatic macrophytes. The positive relationship between the aquatic macrophyte cover between the upper and lower segments of tributaries indicates the importance of dispersion in the colonization of the arms and the reservoir's main body.

  6. Systems modeling approaches for microbial community studies: From metagenomics to inference of the community structure

    Directory of Open Access Journals (Sweden)

    Mark eHanemaaijer

    2015-03-01

    Full Text Available Microbial communities play important roles in health, industrial applications and earth's ecosystems. With current molecular techniques we can characterize these systems in unprecedented detail. However, such methods provide little mechanistic insight into how the genetic properties and the dynamic couplings between individual microorganisms give rise to their dynamic activities. Neither do they give insight into what we call `the community state', that is the fluxes and concentrations of nutrients within the community. This knowledge is a prerequisite for rational control and intervention in microbial communities. Therefore, the inference of the community structure from experimental data is a major current challenge. We will argue that this inference problem requires mathematical models that can integrate heterogeneous experimental data with existing knowledge. We propose that two types of models are needed. Firstly, mathematical models that integrate existing genomic, physiological, and physicochemical information with metagenomics data so as to maximize information content and predictive power. This can be achieved with the use of constraint-based genome-scale stoichiometric modeling of community metabolism which is ideally suited for this purpose. Next, we propose a simpler coarse-grained model, which is tailored to solve the inference problem from the experimental data. This model unambiguously relate to the more detailed genome-scale stoichiometric models which act as heterogeneous data integrators. The simpler inference models are, in our opinion, key to understanding microbial ecosystems, yet until now, have received remarkably little attention. This has led to the situation where the modeling of microbial communities, using only genome-scale models is currently more a computational, theoretical exercise than a method useful to the experimentalist.

  7. Comparison and validation of community structures in complex networks

    CERN Document Server

    Gustafsson, M; Lombardi, A; Gustafsson, Mika; Hornquist, Michael; Lombardi, Anna

    2006-01-01

    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 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 f...

  8. Arsenic rich iron plaque on macrophyte roots - an ecotoxicological risk?

    Energy Technology Data Exchange (ETDEWEB)

    Taggart, M.A. [School of Biological Sciences, University of Aberdeen, Cruickshank Bld, St Machar Drive, Aberdeen, AB24 3UU (United Kingdom); Instituto de Investigacion en Recursos Cinegeticos, IREC (CSIC-UCLM-JCCM), Ronda de Toledo s/n, 13005 Ciudad Real (Spain)], E-mail: mark.taggart@uclm.es; Mateo, R. [Instituto de Investigacion en Recursos Cinegeticos, IREC (CSIC-UCLM-JCCM), Ronda de Toledo s/n, 13005 Ciudad Real (Spain); Charnock, J.M.; Bahrami, F. [Synchrotron Radiation Department, CCLRC Daresbury Laboratory, Warrington, Cheshire, WA4 4AD (United Kingdom); Green, A.J. [Department of Wetland Ecology, Estacion Biologica de Donana, CSIC, Pabellon del Peru, Avenida Maria Luisa s/n, 41013 Seville (Spain); Meharg, A.A. [School of Biological Sciences, University of Aberdeen, Cruickshank Bld, St Machar Drive, Aberdeen, AB24 3UU (United Kingdom)

    2009-03-15

    Arsenic is known to accumulate with iron plaque on macrophyte roots. Three to four years after the Aznalcollar mine spill (Spain), residual arsenic contamination left in seasonal wetland habitats has been identified in this form by scanning electron microscopy. Total digestion has determined arsenic concentrations in thoroughly washed 'root + plaque' material in excess of 1000 mg kg{sup -1}, and further analysis using X-ray absorption spectroscopy suggests arsenic exists as both arsenate and arsenite. Certain herbivorous species feed on rhizomes and bulbs of macrophytes in a wide range of global environments, and the ecotoxicological impact of consuming arsenic rich iron plaque associated with such food items remains to be quantified. Here, greylag geese which feed on Scirpus maritimus rhizome and bulb material in areas affected by the Aznalcollar spill are shown to have elevated levels of arsenic in their feces, which may originate from arsenic rich iron plaque. - Accumulation of metals with iron plaque on macrophyte roots in wetlands poses an ecotoxicological risk to certain herbivores.

  9. Microphyte and macrophyte-based lagooning in tropical regions.

    Science.gov (United States)

    Noumsi, I M K; Nya, J; Akoa, A; Eteme, R A; Ndikefor, A; Fonkou, T; Brissaud, F

    2005-01-01

    A 720 m2 plant made of 8 ponds in series, set in Yaounde (Cameroon), was successively operated as a macrophyte-based system (type M) from November 1997 to October 98, a microphyte-based system (type m) from October 1999 to September 2000 and a combination of macrophyte and microphyte ponds (type M + m) from May to July 2001. Average applied loads varied over the years; from 420 kg. BOD5 ha(-1)d(-1) on the year 1997/98, the loads reached 510 kg BOD5 ha(-1)d(-1) in 1999/2000 and 500 in 2001. Though the system became more and more overloaded and sludge accumulated rapidly in the first ponds, it provided average removals of SS, BOD5 and COD that were always higher than 90% whatever the type of lagooning. Performances in the removal of SS, organic matter and the abatement of N-NH4+ and PO4(3-) did not significantly differ according to the type of lagooning and the applied load. Macrophyte lagooning did not show any definitive superiority as to nutrient removal when compared to microphyte lagooning. Microphyte lagooning was the most effective process in faecal indicators removal.

  10. Diatom community structure on in-service cruise ship hulls.

    Science.gov (United States)

    Hunsucker, Kelli Zargiel; Koka, Abhishek; Lund, Geir; Swain, Geoffrey

    2014-10-01

    Diatoms are an important component of marine biofilms found on ship hulls. However, there are only a few published studies that describe the presence and abundance of diatoms on ships, and none that relate to modern ship hull coatings. This study investigated the diatom community structure on two in-service cruise ships with the same cruise cycles, one coated with an antifouling (AF) system (copper self-polishing copolymer) and the other coated with a silicone fouling-release (FR) system. Biofilm samples were collected during dry docking from representative areas of the ship and these provided information on the horizontal and vertical zonation of the hull, and intact and damaged coating and niche areas. Diatoms from the genera Achnanthes, Amphora and Navicula were the most common, regardless of horizontal ship zonation and coating type. Other genera were abundant, but their presence was more dependent on the ship zonation and coating type. Samples collected from damaged areas of the hull coating had a similar community composition to undamaged areas, but with higher diatom abundance. Diatom fouling on the niche areas differed from that of the surrounding ship hull and paralleled previous studies that investigated differences in diatom community structure on static and dynamically exposed coatings; niche areas were similar to static immersion and the hull to dynamic immersion. Additionally, diatom richness was greater on the ship with the FR coating, including the identification of several new genera to the biofouling literature, viz. Lampriscus and Thalassiophysa. These results are the first to describe diatom community composition on in-service ship hulls coated with a FR system. This class of coatings appears to have a larger diatom community compared to copper-based AF systems, with new diatom genera that have the ability to stick to ship hulls and withstand hydrodynamic forces, thus creating the potential for new problematic species in the biofilm.

  11. Bioactivity effect of two macrophyte extracts on growth performance of two bloom-forming cyanophytes

    Directory of Open Access Journals (Sweden)

    M.G. Ghobrial

    2015-01-01

    in 80 and 70 μl/100 ml treatments with R, −99.80 for both. There are significant differences between the overall averages for each solvent, both of 50% and 100% Potamogeton extracts against Oscillatoria. The highest inhibitory effect for Potamogeton against Oscillatoria was in 103, 800, 200 and 180 μl/100 ml using 50%, 100%, either acetone or ethanol extracts treatments, having LC50 932, 590, 129.50 and 101.428 μl/100 ml, respectively. The potential way for utilizing allelochemicals of aquatic macrophytes could be performed through extracting allelochemicals from dried plants and synthesizing allelochemicals with natural structures, as these macrophytes are available excessively in our lakes.

  12. Microbial community structure in the rhizosphere of rice plants

    Directory of Open Access Journals (Sweden)

    Björn eBreidenbach

    2016-01-01

    Full Text Available The microbial community in the rhizosphere environment is critical for the health of land plants and the processing of soil organic matter. The objective of this study was to determine the extent to which rice plants shape the microbial community in rice field soil over the course of a growing season. Rice (Oryza sativa was cultivated under greenhouse conditions in rice field soil from Vercelli, Italy and the microbial community in the rhizosphere of planted soil microcosms was characterized at four plant growth stages using quantitative PCR and 16S rRNA gene pyrotag analysis and compared to that of unplanted bulk soil. The abundances of 16S rRNA genes in the rice rhizosphere were on average twice that of unplanted bulk soil, indicating a stimulation of microbial growth in the rhizosphere. Soil environment type (i.e. rhizosphere versus bulk soil had a greater effect on the community structure than did time (e.g. plant growth stage. Numerous phyla were affected by the presence of rice plants, but the strongest effects were observed for Gemmatimonadetes, Proteobacteria and Verrucomicrobia. With respect to functional groups of microorganisms, potential iron reducers (e.g. Geobacter, Anaeromyxobacter and fermenters (e.g. Clostridiaceae, Opitutaceae were notably enriched in the rhizosphere environment. A Herbaspirillum species was always more abundant in the rhizosphere than bulk soil and was enriched in the rhizosphere during the early stage of plant growth.

  13. Variation of ant community structure on Ficus benguetensis

    Directory of Open Access Journals (Sweden)

    Shang-Yang Lin

    2016-03-01

    Full Text Available Although ants are commonly found on Ficus trees, information remains lacking on the pattern and diversity of the ant community visiting these trees. We hypothesize that dynamic changes in the availability and types of food can affect the composition as well as abundance of ant communities occurring on fig trees. To investigate the impact of resource availability, diversity, and variability on the ant community structure, we surveyed and recorded the fig phenology and ant abundance on 17 trees (11 male and six female trees of Ficus benguetensis in New Taipei City in northern Taiwan from 2011 to 2013. A total of 13 ant species were found on these fig trees, with 6 species more abundant than the others. The composition and relative abundance of the ant species occurring on F. benguetensis trees showed significant variations associated with tree sex, fig abundance, fig developmental phase, as well as temperature. A degree of dietary niche partitioning was also observed. We suggest that sexual differentiation in fig phenology plays a major role in controlling the availability and variance in food resources for ants, thereby shaping the complex ant communities foraging on F. benguetensis.

  14. Competition for space and the structure of ecological communities

    CERN Document Server

    Yodzis, Peter

    1978-01-01

    This volume is an investigation of interspecific competition for space, particularly among sessile organisms, both plant and animal, and its consequences for community structure. While my own contribu­ tion ----and the bulk of this volume --- lies in mathematical analysis of the phenomenon, I have also tried to summarize the most important natural historical aspects of these communities, and have devoted much effort to relating the mathematical results to observations of the natural world. Thus, the volume has both a synthetic and an analytic aspect. On the one hand, I have been struck by certain similarities among many communities, from forests to mussel beds, in which spatial com­ petition is important. On the other hand, I have analyzed this pheno­ menon by means of reaction-dispersal models. Finally, the mathematical analysis has suggested a conceptual framework for these communities which, I believe, further unifies and illuminates the field data. A focal perception of this work is that, just as niche...

  15. Making the links between community structure and individual well-being: community quality of life in Riverdale, Toronto, Canada.

    Science.gov (United States)

    Raphael, D; Renwick, R; Brown, I; Steinmetz, B; Sehdev, H; Phillips, S

    2001-09-01

    An inquiry into community quality of life was carried out within a framework that recognizes the complex relationship between community structures and individual well-being. Through use of focus groups and key informant interviews, community members, service providers, and elected representatives in a Toronto community considered aspects of their community that affected quality of life. Community members identified strengths of access to amenities, caring and concerned people, community agencies, low-cost housing, and public transportation. Service providers and elected representatives recognized diversity, community agencies and resources, and presence of culturally relevant food stores and services as strengths. At one level, findings were consistent with emerging concepts of social capital. At another level, threats to the community were considered in relation to the hypothesized role neo-liberalism plays in weakening the welfare state.

  16. A local immunization strategy for networks with overlapping community structure

    Science.gov (United States)

    Taghavian, Fatemeh; Salehi, Mostafa; Teimouri, Mehdi

    2017-02-01

    Since full coverage treatment is not feasible due to limited resources, we need to utilize an immunization strategy to effectively distribute the available vaccines. On the other hand, the structure of contact network among people has a significant impact on epidemics of infectious diseases (such as SARS and influenza) in a population. Therefore, network-based immunization strategies aim to reduce the spreading rate by removing the vaccinated nodes from contact network. Such strategies try to identify more important nodes in epidemics spreading over a network. In this paper, we address the effect of overlapping nodes among communities on epidemics spreading. The proposed strategy is an optimized random-walk based selection of these nodes. The whole process is local, i.e. it requires contact network information in the level of nodes. Thus, it is applicable to large-scale and unknown networks in which the global methods usually are unrealizable. Our simulation results on different synthetic and real networks show that the proposed method outperforms the existing local methods in most cases. In particular, for networks with strong community structures, high overlapping membership of nodes or small size communities, the proposed method shows better performance.

  17. Functional and spatial structure of the urbotechnozem mesopedobiont community

    Directory of Open Access Journals (Sweden)

    O. N. Kunah

    2016-09-01

    Full Text Available The results of studying the spatial structure of soil mesofauna of an urbanotechnozem by OMI- and RLQ-analysis are presented. The research was conducted on 5 June 2012 in the Botanic Garden of Oles Gonchar University (previously – territory of the Park Y. Gagarin, Dnipropetrovsk. The studied plot is situated on the slope of the Krasnopostachekaya balka (48°25'57.43" N, 35°2'16.52" E. The plot consists of 15 transects directed in a perpendicular manner in relation to the talweg. Each transect is made of seven sample points. The distance between points is 2 m. The coordinates of the lower left point were taken as (0; 0. The plot consisted of artificial grassland with a single tree. The vegetation was composed of grassland and steppe, of a mega-mesotrophic, xeromesophilic character. At each point the mesopedobionts were studied (data presented as L-table; temperature, electrical conductivity and soil penetration resistance, and grass height were measured (data presented as R-table. The soil-zoological test area was 25×25 cm. The mesopedobiont community was represented by 28 species and with total abundance 70.1 ind./m2. The following groups were dominant in the ecological structure of the soil animal community; saprohages, pratants, mesotrophocoenomorphs and the endogeic group. The measured edaphic characteristics were shown to play an important role in structurization of the ecological niche of the mesopedobiont community. The usage of morphological or physiological features of animals for the assessment of degree of specific distinctions is applicable for homogeneous taxonomic or ecological groups possessing comparable characteristics which also can be interpreted ecologically. The soil mesofauna is characterized by high taxonomic and ecological diversity of forms,which are difficult to compare by morphological or physiological criteria. The ecological value of characteristics in different groups will be not identical, and the basis for

  18. Improved community structure detection using a modified fine tuning strategy

    CERN Document Server

    Sun, Yudong; Josic, Kresimir; Bassler, Kevin E

    2009-01-01

    The community structure of a complex network can be determined by finding the partitioning of its nodes that maximizes modularity. Many of the proposed algorithms for doing this work by recursively bisecting the network. We show that this unduely constrains their results, leading to a bias in the size of the communities they find and limiting their effectivness. To solve this problem, we propose adding a step to the existing algorithms that does not increase the order of their computational complexity. We show that, if this step is combined with a commonly used method, the identified constraint and resulting bias are removed, and its ability to find the optimal partitioning is improved. The effectiveness of this combined algorithm is also demonstrated by using it on real-world example networks. For a number of these examples, it achieves the best results of any known algorithm.

  19. The CECAM Electronic Structure Library: community-driven development of software libraries for electronic structure simulations

    Science.gov (United States)

    Oliveira, Micael

    The CECAM Electronic Structure Library (ESL) is a community-driven effort to segregate shared pieces of software as libraries that could be contributed and used by the community. Besides allowing to share the burden of developing and maintaining complex pieces of software, these can also become a target for re-coding by software engineers as hardware evolves, ensuring that electronic structure codes remain at the forefront of HPC trends. In a series of workshops hosted at the CECAM HQ in Lausanne, the tools and infrastructure for the project were prepared, and the first contributions were included and made available online (http://esl.cecam.org). In this talk I will present the different aspects and aims of the ESL and how these can be useful for the electronic structure community.

  20. 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.

  1. The Evolution of Community Structure in a Coauthorship Network

    Directory of Open Access Journals (Sweden)

    William Mcdowell

    2011-12-01

    Full Text Available Mechanisms such as triadic closure and preferential attachment drive the evolution of social networks. Many models use these mechanisms to predict future links, and they generate realistic networks with scale-free degree distributions. These social networks also have community structure, or sets of vertices which are more connected to each other than the rest of the network. To study the evolution of research groups of scientists in a coauthorship network, we use a timeheterarchy representation to extend the mechanisms driving the evolution of the network to the level of this community structure. Specifically, we examine changes in the structure of groups in terms of mechanisms analogous to triadic closure and preferential attachment, and as a result, we find that the network evolves in the same way at the group-level and the individual-level. In addition, we find that interactions at the group-level might affect interactions at the individual-level in that members of a single group are more likely to strengthen their relationships than members of separate groups.

  2. [Effects of colistin sulfate residue on soil microbial community structure].

    Science.gov (United States)

    Ma, Yi; Peng, Jin-Ju; Chen, Jin-Jun; Fan, Ting-Li; Sun, Yong-Xue

    2014-06-01

    By using fumigation extraction and phospholipid fatty acid (PLFA) methods, the change of characteristics of soil microbial community structure caused by residue of colistin sulfate (CS) was studied. The results showed that the CS (w(cs) > or = 5 mg x kg(-1)) had a significant effect on the microbial biomass carbon (MBC) and it was dose-dependent where MBC decreased with the increase of CS concentration in soil. The MBC in soil decreased by 52. 1% when the CS concentration reached 50 mg x kg(-1). The total PLFA of soil in each CS treatment was significantly decreased during the sampling period compared with the control group and showed a dose-dependent relationship. The soil microbial community structure and diversity in the low CS group (w(cs) = 0.5 mg x kg(-1)) were not significantly different from the control group on 7th and 49th day. However, they were significantly different on 21st and 35th day especially in the high CS group (w(cs) = 50 mg x kg(-1)). It was concluded that CS could change the structure of soil microorganisms and varied with time which might be caused by the chemical conversion and degradation of CS in soil.

  3. Extending one-dimensional models for deep lakes to simulate the impact of submerged macrophytes on water quality

    NARCIS (Netherlands)

    Sachse, R.; Petzoldt, T.; Blumstock, M.; Moreira, S.; Pätzig, M.; Rücker, J.; Janse, J.H.; Mooij, W.M.; Hilt, S.

    2014-01-01

    Submerged macrophytes can stabilise clear water conditions in shallow lakes. However, many existing models for deep lakes neglect their impact. Here, we tested the hypothesis that submerged macrophytes can affect the water clarity in deep lakes. A one-dimensional, vertically resolved macrophyte mode

  4. Restoring macrophyte diversity in shallow temperate lakes: biotic versus abiotic constraints

    NARCIS (Netherlands)

    Bakker, E.S.; Sarneel, J.M.; Gulati, R.D.; Liu, Z.; Van Donk, E.

    2013-01-01

    Although many lake restoration projects have led to decreased nutrient loads and increased water transparency, the establishment or expansion of macrophytes does not immediately follow the improved abiotic conditions and it is often unclear whether vegetation with high macrophyte diversity will retu

  5. Macrophyte-phytoplankton interactions: the relative importance of allelopathy versus other factors

    NARCIS (Netherlands)

    Mulderij, G.; Nes, van E.H.; Donk, van E.

    2007-01-01

    Submerged aquatic macrophytes are important in shallow aquatic ecosystems because they stabilize the macrophyte-dominated state by increasing water transparency in various ways. One of these is the excretion of allelopathic substances inhibitory to phytoplankton, but it is still controversial whethe

  6. Macrophyte-phytoplankton interactions: the relative importance of allelopathy versus other factors

    NARCIS (Netherlands)

    Mulderij, G.; van Nes, E.H.; Van Donk, E.

    2007-01-01

    Abstract Submerged aquatic macrophytes are important in shallow aquatic ecosystems because they stabilize the macrophyte-dominated state by increasing water transparency in various ways. One of these is the excretion of allelopathic substances inhibitory to phytoplankton, but it is still controversi

  7. Competition between free-floating and submerged macrophytes in a future of climate change

    NARCIS (Netherlands)

    Netten, J.J.C.

    2011-01-01


    This research was about the asymmetric competition between free-floating and submerged macrophytes in shallow freshwater ecosystems. I studied the effect of climate change on the dominance of free-floating macrophytes in temperate regions. The research approach was a combination of outdoor me

  8. Competition between free-floating and submerged macrophytes in a future of climate change

    NARCIS (Netherlands)

    Netten, J.J.C.

    2011-01-01


    This research was about the asymmetric competition between free-floating and submerged macrophytes in shallow freshwater ecosystems. I studied the effect of climate change on the dominance of free-floating macrophytes in temperate regions. The research approach was a combination of outdoor

  9. Macrophyte species distribution, indices of biotic integrity and sampling intensity in isolated Florida marshes

    Science.gov (United States)

    This study tested macrophyte condition metrics calculated after decreasing the effort and area of sampling by 33% to 66%, as tested in 74 emergent isolated wetlands. Four belted transects from wetland edge to center were established and rooted macrophytes were identified. The eff...

  10. Effects of the herbicide 2,4-D on the growth of nine aquatic macrophytes

    NARCIS (Netherlands)

    Belgers, J.D.M.; Lieverloo, van R.J.; Pas, van der L.J.T.; Brink, van den P.J.

    2007-01-01

    A study was conducted to determine the effect of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) on nine submersed macrophyte species. The first objective of the study was to investigate the sensitivity of various endpoints in macrophyte toxicity tests. A second objective was to investigate the

  11. Experimental Effects of Lime Application on Aquatic Macrophytes: 4. Growth Response of Three Species

    Science.gov (United States)

    2007-04-01

    James PURPOSE: This investigation examined the growth response of three macrophyte species ( Elodea canadensis, Stuckenia pectinata, and Vallisnaria...different macrophyte species. These hypotheses were tested using experimental mesocosms. METHODS: Elodea canadensis, Stuckenia pectinata, and...Snel, P. E. Zanstra, and R. J. Helder. 1982. The mechanism of bicarbonate assimilation by the polar leaves of Potamogeton and Elodea . CO2 concentrations

  12. First steps in the Central-Baltic intercalibration exercise on lake macrophytes: where do we start?

    NARCIS (Netherlands)

    Tóth, L.G.; Poikane, S.; Penning, W.E.; Free, G.; Mäemets, H.; Kolada, A.; Hanganu, J.

    2008-01-01

    The Water Framework Directive (WFD 2000) defines macrophytes as one of the biological groups required for the ecological assessment of European surface waters. Several indices for macrophyte assessment have been proposed or are currently in use by different European states. As a first step towards p

  13. Macrophyte-phytoplankton interactions: the relative importance of allelopathy versus other factors

    NARCIS (Netherlands)

    Mulderij, G.; van Nes, E.H.; Van Donk, E.

    2007-01-01

    Abstract Submerged aquatic macrophytes are important in shallow aquatic ecosystems because they stabilize the macrophyte-dominated state by increasing water transparency in various ways. One of these is the excretion of allelopathic substances inhibitory to phytoplankton, but it is still

  14. Macrophyte-phytoplankton interactions: the relative importance of allelopathy versus other factors

    NARCIS (Netherlands)

    Mulderij, G.; Nes, van E.H.; Donk, van E.

    2007-01-01

    Submerged aquatic macrophytes are important in shallow aquatic ecosystems because they stabilize the macrophyte-dominated state by increasing water transparency in various ways. One of these is the excretion of allelopathic substances inhibitory to phytoplankton, but it is still controversial

  15. Trophic structure and community stability in an overfished ecosystem

    KAUST Repository

    Utne-Palm, Anne Christine

    2010-07-15

    Since the collapse of the pelagic fisheries off southwest Africa in the late 1960s, jellyfish biomass has increased and the structure of the Benguelan fish community has shifted, making the bearded goby (Sufflogobius bibarbatus) the new predominant prey species. Despite increased prédation pressure and a harsh environment, the gobies are thriving. Here we show that physiological adaptations and antipredator and foraging behaviors underpin the success of these fish. In particular, body-tissue isotope signatures reveal that gobies consume jellyfish and sulphidic diatomaceous mud, transferring "dead-end" resources back into the food chain.

  16. Analysis of community structure in networks of correlated data

    Energy Technology Data Exchange (ETDEWEB)

    Gomez, S.; Jensen, P.; Arenas, A.

    2008-12-25

    We present a reformulation of modularity that allows the analysis of the community structure in networks of correlated data. The new modularity preserves the probabilistic semantics of the original definition even when the network is directed, weighted, signed, and has self-loops. This is the most general condition one can find in the study of any network, in particular those defined from correlated data. We apply our results to a real network of correlated data between stores in the city of Lyon (France).

  17. Experimental warming effects on the bacterial community structure and diversity

    Science.gov (United States)

    Kim, W.; Han, S.; Adams, J.; Son, Y.

    2014-12-01

    The objective of this study is to investigate the responses of soil bacterial community to future temperature increase by conducting open-field warming experiment. We conducted an open-field experimental warming system using infra-red heater in 2011 and regulated the temperature of warmed plots by 3oC higher than that of control plots constantly. The seeds of Pinus densiflora, Abies holophylla, Abies koreana, Betula costata, Quercus variabilis, Fraxinus rhynchophylla, and Zelkova serrata were planted in each 1 m × 1 m plot (n=3) in April, 2012. We collected soil samples from the rhizosphere of 7 tree species. DNA was extracted and PCR-amplified for the bacterial 16S gene targeting V1-V3 region. The paired-end sequencing was performed at Beijing Genome Institute (BGI, Hong Kong, China) using 2× 100 bp Hiseq2000 (Illumina). This study aimed to answer the following prediction/hypothesis: 1) Experimental warming will change the structure of soil bacterial community, 2) There will be distinct 'indicator group' which response to warming treatment relatively more sensitive than other groups. 3) Warming treatment will enhance the microbial activity in terms of soil respiration. 4) The rhizoplane bacterial communities for each of 7 tree species will show different response pattern to warming treatment. Since the sequence data does not arrive before the submission deadline, therefore, we would like to present the results and discussions on December 2014, AGU Fall Meeting.

  18. Comparison of adult mosquito community structure on various habitats

    Institute of Scientific and Technical Information of China (English)

    ZHONG-CHENGYAN; HARRYZHONG

    2005-01-01

    The community structure of adult mosquitoes was compared from New Jersey light trap collections in six different types of habitats in Citrus County, Florida, USA. From October 1998 to December 2000, mosquitoes were collected three times a week from the following habitats (swamps, swamps and freshwater marshes, pine fiat-woods, pine fiat-woods and scrub, salt marshes, and salt marshes and mangroves). Mosquito density was highest in the swamps and freshwater marshes habitat, with an average of 95.65 specimens per trap.Density was lowest in the flatwoods and scrub habitat, with an average of 14.38 specimens per trap. Species dominance differed among habitats. Salt marshes produced the greatest aggregation index, while pine flatwoods produced the lowest. Conversely, diversity analysis showed that pine flatwoods had the greatest diversity, while salt marshes the lowest diversity. Similarity indices indicated that the adult mosquito communities from pine flatwoods and pine flatwoods and scrub were very similar (0.8583). The adult mosquito community of salt marshes was different from that of swamps and freshwater marshes (the similar index was 0.0217).

  19. 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

  20. Carbonic anhydrase levels and internal lacunar CO/sub 2/ concentrations in aquatic macrophytes

    Energy Technology Data Exchange (ETDEWEB)

    Weaver, C.I.

    1979-01-01

    Carbonic anhydrase levels were examined in a variety of aquatic macrophytes from different habitats. In general, carbonic anhydrase levels increased across the habitat gradient such that activities were low in submersed aquatic macrophytes and high in emergent macrophytes with floating-leaved and free-floating plants exhibiting intermediate activities. Internal lacunar CO/sub 2/ concentrations were analyzed in relation to carbonic anhydrase activities. There was no correlation between these two parameters. Internal CO/sub 2/ concentrations ranged from low to high in submersed macrophytes, but were low in floating-leaved and emergent macrophytes. The observed internal CO/sub 2/ concentrations are discussed in relation to the individual morphologies of the plants and the environments in which they occurred.

  1. Effects of altered estuarine submerged macrophyte bed cover on the omnivorous Cape stumpnose Rhabdosargus holubi.

    Science.gov (United States)

    Sheppard, J N; Whitfield, A K; Cowley, P D; Hill, J M

    2012-03-01

    The ecological importance of submerged macrophyte beds to fishes within estuaries was investigated through the example of the ubiquitous Cape stumpnose Rhabdosargus holubi, an omnivorous, vegetation and estuary-dependent species, using stable-isotope techniques and long-term abundance (catch-per-unit-effort) data from the East Kleinemonde Estuary, South Africa. Outputs from a Bayesian mixing model using δ(13) C and δ(15) N signatures indicated that the submerged macrophytes Ruppia cirrhosa and Potamogeton pectinatus were not a primary source of nutrition for R. holubi, confirming previous work that revealed that macrophytes are consumed but not digested. Long-term seine netting data showed reduced abundance of R. holubi during a prolonged period of macrophyte senescence, suggesting that submerged macrophyte habitats provide shelter that reduces mortality (predation risk) and a food-rich foraging area. © 2012 SAIAB. Journal of Fish Biology © 2012 The Fisheries Society of the British Isles.

  2. Aquatic macrophytes of Itaipu Reservoir, Brazil: survey of species and ecological considerations

    Directory of Open Access Journals (Sweden)

    Sidinei Magela Thomaz

    1999-01-01

    Full Text Available In a survey of the aquatic macrophytes of the Itaipu Reservoir, we identified 62 taxa in 25 families and 42 genera. The highest number taxa was observed for the emergent macrophytes (40 taxa. Reduced fluctuation in water level, increased light penetration, and sediment enrichment by nutrients and organic matter following the formation of the reservoir favored the appearance of a species-rich community of submerged macrophytes (23% of the taxa identified. The aquatic macrophytes were found mainly near the mouths of the main tributaries of the reservoir, in shallow area of depth less than 2 meters. In addition to the shallow depth, the greater nutrient input from the tributaries and relative protection from wind explained this distribution. Among the species found, Egeria najas merits mention for its occurrence in all localities sampled, with biomass values varying between 98 and 186 gDW/m². Some potential nuisance species such as Eichhornia crassipes, Salvinia auriculata, and Pistia stratiotes also deserve attention, since they were also observed to be covering large areas of Itaipu Reservoir.Em um levantamento de macrófitas aquáticas realizado no reservatório de Itaipu foram identificados 62 táxons pertencentes a 25 famílias e 42 gêneros. O maior número de táxons foi representado pelas macrófitas emergentes (40 táxons. O surgimento de uma rica comunidade de espécies submersas (23% dos táxons identificados parece ter sido favorecido pelas alterações decorrentes da formação dor reservatório, tais como redução da flutuação dos níveis de água, aumento da penetração de luz e enriquecimento do sedimento em nutrientes e matéria orgânica. As macrófitas aquáticas foram registradas principalmente próximo à foz dos tributários do reservatório, em áreas rasas (profundidade inferior a 2 metros. Além da reduzida profundidade, o maior aporte de nutrientes associado à proteção do vento explicam essa distribuição. Entre

  3. Structure and dynamics of the periphytic algae community of Iraí reservoir, Paraná State, Brazil - DOI: 10.4025/actascibiolsci.v32i1.3764 Structure and dynamics of the periphytic algae community of Iraí Reservoir, Paraná State, Brazil - DOI: 10.4025/actascibiolsci.v32i1.3764

    Directory of Open Access Journals (Sweden)

    Liliana Rodrigues

    2009-12-01

    Full Text Available In order to analyze the structure and dynamics of the periphytic community in Iraí reservoir, an eutrophic environment, samples were taken in two seasons: summer (April and winter (September of 2002, in littoral areas from three regions of the reservoir (upper, intermediary and lower. Rooted aquatic vegetation were used as sampling substrates, because they were found in all sampling sites. A total of 297 species was recorded (225 in April, 73 exclusive taxa; and 224 in September, with 72 exclusive taxa. Bacillariophyceae predominated in all regions in both seasons, in species number, as well in density. There were differences in richness among zones; intermediary and lower regions were more similar, mainly in September. The periphytic algae density differed significantly between seasons (p = 0.002; F = 16.48, with lower values in the summer. No significant difference in density was recorded among zones.In order to analyze the structure and dynamics of the periphytic community in Iraí reservoir, which is considered a eutrophic environment, samples were taken in two seasons: summer (April and winter (September of 2002, in littoral areas from three regions of the reservoir (upper, intermediary and lower. Aquatic macrophytes were used as sampling substrates, because they were found in all sampling sites. A total of 297 species was recorded (225 in April, 73 exclusive to this season; and 224 in September, with 72 exclusive taxa. Bacillariophyceae predominated in all regions in both seasons, in number of species as well as in density. There were differences in richness among zones; intermediary and lower regions were more similar, mainly in September. The periphytic algae density differed significantly between seasons (F = 16,48; p = 0,002, with lower values in the summer. No significant difference in density was recorded among zones.

  4. Maps of random walks on complex networks reveal community structure.

    Science.gov (United States)

    Rosvall, Martin; Bergstrom, Carl T

    2008-01-29

    To comprehend the multipartite organization of large-scale biological and social systems, we introduce an information theoretic approach that reveals community structure in weighted and directed networks. We use the probability flow of random walks on a network as a proxy for information flows in the real system and decompose the network into modules by compressing a description of the probability flow. The result is a map that both simplifies and highlights the regularities in the structure and their relationships. We illustrate the method by making a map of scientific communication as captured in the citation patterns of >6,000 journals. We discover a multicentric organization with fields that vary dramatically in size and degree of integration into the network of science. Along the backbone of the network-including physics, chemistry, molecular biology, and medicine-information flows bidirectionally, but the map reveals a directional pattern of citation from the applied fields to the basic sciences.

  5. 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.

  6. [Community structure of planktonic rotifers in the Pearl River Delta].

    Science.gov (United States)

    Gao, Yuan; Li, Xin-Hui; Lai, Zi-Ni; Yu, Jing; Wang, Chao; Zeng, Yan-Yi; Liu, Qian-Fu; Yang, Wan-Ling

    2014-07-01

    Four ecological investigations were carried out on planktonic rotifers in Pearl River Delta in 2012. The community structure, including spatial and temporal patterns of species composition, dominant species, biomass and biodiversity, was investigated. The correlation between the community structure of rotifers and the environmental factors was discussed. Moreover, the aggregation structures of rotifers were analyzed. A total of 53 rotifer species were found. Dominant species changed markedly with season and space. Polyarthra trigla had higher dominance. In terms of seasonal changes, the density and biomass were higher in dry season than in wet season, while the biodiversity and evenness indices were vice versa. The biomass and biodiversity of rotifers showed highly significant differences among seasons. In terms of spatial distribution, the average density and the average biomass showed an increase from the southwest to the northeast. The highest density and biomass were recorded in Shiqiao. The biodiversity and evenness indices had an opposite spatial distribution, with the highest values being recorded in Qingqi. The rotifer density was significantly different among the investigated sites, while the biomass and biodiversity were not significantly different. Correlation analysis demonstrated a highly significant positive correlation between rotifer density and biomass, as well as between biodiversity and evenness indices, and a highly negative correlation between biodiversity and biomass. The biodiversity and evenness indices both decreased markedly with the increase of biomass. Principal component analysis indicated that the rotifer density was closely correlated with environment factors, such as water temperature, pH, dissolved oxy- gen, chlorophyll a content, total phosphorus, and total nitrogen, in different seasons. Aggregation analysis based on rotifer density revealed five aggregation structures in the investigated sites, indicating significant differences

  7. Microbial Community Structure and Enzyme Activities in Semiarid Agricultural Soils

    Science.gov (United States)

    Acosta-Martinez, V. A.; Zobeck, T. M.; Gill, T. E.; Kennedy, A. C.

    2002-12-01

    The effect of agricultural management practices on the microbial community structure and enzyme activities of semiarid soils of different textures in the Southern High Plains of Texas were investigated. The soils (sandy clay loam, fine sandy loam and loam) were under continuous cotton (Gossypium hirsutum L.) or in rotations with peanut (Arachis hypogaea L.), sorghum (Sorghum bicolor L.) or wheat (Triticum aestivum L.), and had different water management (irrigated or dryland) and tillage (conservation or conventional). Microbial community structure was investigated using fatty acid methyl ester (FAME) analysis by gas chromatography and enzyme activities, involved in C, N, P and S cycling of soils, were measured (mg product released per kg soil per h). The activities of b-glucosidase, b-glucosaminidase, alkaline phosphatase, and arylsulfatase were significantly (Pconservation tillage in comparison to continuous cotton under conventional tillage. Principal component analysis showed FAME profiles of these soils separated distinctly along PC1 (20 %) and PC2 (13 %) due to their differences in soil texture and management. No significant differences were detected in FAME profiles due to management practices for the same soils in this sampling period. Enzyme activities provide early indications of the benefits in microbial populations and activities and soil organic matter under crop rotations and conservation tillage in comparison to the typical practices in semiarid regions of continuous cotton and conventional tillage.

  8. Physical and chemical properties of substrates produced using macrophytes aquatics

    Directory of Open Access Journals (Sweden)

    Walda Monteiro Farias

    2013-12-01

    Full Text Available Aquatic macrophytes are widely used as bioindicators of water quality because their proliferation usually occurs in eutrophic water sources and has hit several parts of Brazil and the world, restricted the multiple uses of aquatic ecosystems. However, this group of plants is able to retain considerable amounts of nutrients, presenting high productivity and high growth rate, thus, a good source of biomass for use in the production of substrates. In order to evaluate the potential of aquatic macrophytes water hyacinth (Eichhornia crassipes Solms., water lettuce (Pistia stratiotes L. and cattail (Typha domingensis Pers. in the production of substrates was performed in this work, the physical and chemical characterization and evaluation of the degree of humification. The treatments were arranged in a 3 × 4 factorial, completely randomized design with three replications. All substrates produced with 100% macrophyte density present within the limits of 400 kg m-3, considered ideal. The composite substrates with water hyacinth and water lettuce are with the electrical conductivity of 0,79 a 2,49 dS m-1 within recommended. organic compounds produced are considered mature and have high levels of nitrogen phosphorus and potassium; The substrate produced with 70% water lettuce +30 % dung and 70% composed of cattail manure +20% +10% topsoil and 70 +30% cattail manure have C/N ratio within the considered ideal; the humification ratio and humification index, except for the four treatments (70 % water lettuce manure +30%, 5 (100% water hyacinth and 8 (70% water hyacinth manure +30% are within the considered ideal, the percentage of humic acids and polymerization rate, except for treatments 1 (100% water lettuce and 12 (100% cattail, are shown below the ideal.

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

    Science.gov (United States)

    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.

  10. Perspectives on the Gender-Integrated Gay Community: Its Formal Structure and Social Functions

    Science.gov (United States)

    Fein, Sara Beck; Nuehring, Elane M.

    1975-01-01

    A gender-integrated homosexual community is described. Male and female members are compared as to participation in the community's formal organizational structure as well as in relation to several functions of that community. The integrated community differed in a number of dimensions from exclusively male and exclusively female homosexual…

  11. Using Model-based Overlapping Seed Expansion to detect highly overlapping community structure

    CERN Document Server

    McDaid, Aaron F

    2010-01-01

    As research into community finding in social networks progresses, there is a need for algorithms capable of detecting overlapping community structure. Many algorithms have been proposed in recent years that are capable of assigning each node to more than a single community. The performance of these algorithms tends to degrade when the ground-truth contains a more highly overlapping community structure, with nodes assigned to more than two communities. Such highly overlapping structure is likely to exist in many social networks, such as Facebook friendship networks. In this paper we present a scalable algorithm, MOSES, based on a statistical model of community structure, which is capable of detecting highly overlapping community structure, especially when there is variance in the number of communities each node is in. In evaluation on synthetic data MOSES is found to be superior to existing algorithms, especially at high levels of overlap. We demonstrate MOSES on real social network data by analyzing the netwo...

  12. Aquatic Macrophyte Risk Assessment for Pesticides

    NARCIS (Netherlands)

    Maltby, L.; Arnold, D.; Arts, G.H.P.; Davies, J.; Heimbach, F.; Pickl, C.; Poulsen, V.

    2009-01-01

    Given the essential role that primary producers play in aquatic ecosystems, it is imperative that the potential risk of pesticides to the structure and functioning of aquatic plants is adequately assessed. This book discusses the assessment of the risk of pesticides with herbicidal activity to

  13. Aquatic Macrophyte Risk Assessment for Pesticides

    NARCIS (Netherlands)

    Maltby, L.; Arnold, D.; Arts, G.H.P.; Davies, J.; Heimbach, F.; Pickl, C.; Poulsen, V.

    2009-01-01

    Given the essential role that primary producers play in aquatic ecosystems, it is imperative that the potential risk of pesticides to the structure and functioning of aquatic plants is adequately assessed. This book discusses the assessment of the risk of pesticides with herbicidal activity to aquat

  14. Network community structure alterations in adult schizophrenia: identification and localization of alterations.

    Science.gov (United States)

    Lerman-Sinkoff, Dov B; Barch, Deanna M

    2016-01-01

    A growing body of literature suggests functional connectivity alterations in schizophrenia. While findings have been mixed, evidence points towards a complex pattern of hyper-connectivity and hypo-connectivity. This altered connectivity can be represented and analyzed using the mathematical frameworks provided by graph and information theory to represent functional connectivity data as graphs comprised of nodes and edges linking the nodes. One analytic technique in this framework is the determination and analysis of network community structure, which is the grouping of nodes into linked communities or modules. This data-driven technique finds a best-fit structure such that nodes in a given community have greater connectivity with nodes in their community than with nodes in other communities. These community structure representations have been found to recapitulate known neural-systems in healthy individuals, have been used to identify novel functional systems, and have identified and localized community structure alterations in a childhood onset schizophrenia cohort. In the present study, we sought to determine whether community structure alterations were present in an adult onset schizophrenia cohort while stringently controlling for sources of imaging artifacts. Group level average graphs in healthy controls and individuals with schizophrenia exhibited visually similar network community structures and high amounts of normalized mutual information (NMI). However, testing of individual subject community structures identified small but significant alterations in community structure with alterations being driven by changes in node community membership in the somatosensory, auditory, default mode, salience, and subcortical networks.

  15. Community structure and seasonal variation of an inshore demersal fish community at Goa, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Ansari, Z.A.; Chatterji, A.; Ingole, B.S.; Sreepada, R.A.; Rivonker, C.U.; Parulekar, A.H.

    ) have also reported changes in composition of dominant groups due to high mechanized fishing pressure in the Gulf of Thailand. A similar trend was reported for the Terenggane coast of Malaysia, where Leiognathidae decreased significantly following heavy... temperate demersal fish community. In other fish communities, the abundant species are usually low in the tropical structure (Allen & Horn, 1975). The size of the dominant fish in a community is partially controlled by the size of the food organisms. Smaller...

  16. Effects of Greater flamingo Phoenicopterus ruber on macrophytes, chironimds and turbidity in natural marshes in Doñana, SW Spain

    OpenAIRE

    Rodríguez-Pérez, Héctor; Andy J Green

    2007-01-01

    Top predators and nutrient inputs are important factors determining the structure of freshwater aquatic systems. Greater flamingos (Phoenicopterus ruber) has been shown to destroy submerged macrophytes and may promote a switch from clear water to turbid water in the temporary marshes of Doñana National Park. We excluded flamingos from twenty 4x4 m plots distributed between two lucios (shallow seasonal lakes) within the marshes from February to July 2004. In July, we measured total suspended s...

  17. Soil phosphorus depletion and shifts in plant communities change bacterial community structure in a long-term grassland management trial.

    Science.gov (United States)

    Adair, Karen L; Wratten, Steve; Lear, Gavin

    2013-06-01

    Agricultural systems rely on healthy soils and their sustainability requires understanding the long-term impacts of agricultural practices on soils, including microbial communities. We examined the impact of 17 years of land management on soil bacterial communities in a New Zealand randomized-block pasture trial. Significant variation in bacterial community structure related to mowing and plant biomass removal, while nitrogen fertilizer had no effect. Changes in soil chemistry and legume abundance described 52% of the observed variation in the bacterial community structure. Legumes (Trifolium species) were absent in unmanaged plots but increased in abundance with management intensity; 11% of the variation in soil bacterial community structure was attributed to this shift in the plant community. Olsen P explained 10% of the observed heterogeneity, which is likely due to persistent biomass removal resulting in P limitation; Olsen P was significantly lower in plots with biomass removed (14 mg kg(-1) ± 1.3SE) compared with plots that were not mown, or where biomass was left after mowing (32 mg kg(-1) ± 1.6SE). Our results suggest that removal of plant biomass and associated phosphorus, as well as shifts in the plant community, have greater long-term impacts on soil bacterial community structure than application of nitrogen fertilizers.

  18. Community structure and composition of the Cambrian Chengjiang biota

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Based on previously published species data(228 species in over 18 phyla) and field sampling(114 species and 18406 individuals) in the Chengjiang-Haikou-Anning area,we analyzed quantitatively the paleocommunity composition and structure of the Cambrian Chengjiang biota(Cambrian Series 2,eastern Yunnan,China).Arthropods dominate the community both in species diversity(species:37%) and in abundance(individuals:51.8%).Priapulids(individuals:22.6%) and brachiopods(individuals:16.3%) follow in abundance rank.The arthropod Kunmingella douvillei(26.2%),the priapulid Cricocosmia jinning-ensis(15.4%),and the brachiopod Diandongia pista(11%) are the three most abundant species.Ecological analyses show that the community was dominated by epifaunal organisms(species:63%,individuals:68.4%) followed by infaunal organisms(species:11.9%,individuals:25.9%),nektobenthic organisms(species:11.5%,individuals:2.6%),and pelagic organisms(species:5.3%,individuals:3.1%).The diverse feeding strategies,dominated by suspension feeders(species:35.6%,individuals:26.1%) and hunter/scavengers(species:31.1%,individuals:40.4%),indicate the former existence of a complex food chain and intense competition.Epifaunal vagrant omnivores(28.2%),infaunal vagrant hunter/scavengers(19.8%),epifaunal sessile suspension feeders(17.7%),and epifaunal vagrant hunter/scavengers(15.3%) were the most abundant ecological groups,represented primarily by arthropods,poriferans,priapulids,and brachiopods.Ecological group analyses reveal that the early Cambrian Chengjiang biota is similar in community patterns and functional relations to modern biotas in shallow marine settings.

  19. Phytoplankton community structure in the VAHINE mesocosm experiment

    Science.gov (United States)

    Leblanc, Karine; Cornet, Véronique; Caffin, Mathieu; Rodier, Martine; Desnues, Anne; Berthelot, Hugo; Turk-Kubo, Kendra; Heliou, Jules

    2016-09-01

    The VAHINE mesocosm experiment was designed to trigger a diazotroph bloom and to follow the subsequent transfer of diazotroph-derived nitrogen (DDN) in the rest of the food web. Three mesocosms (50 m3) located inside the Nouméa lagoon (New Caledonia, southwestern Pacific) were enriched with dissolved inorganic phosphorus (DIP) in order to promote N2 fixation in these low-nutrient, low-chlorophyll (LNLC) waters. Initially, the diazotrophic community was dominated by diatom diazotroph associations (DDAs), mainly by Rhizosolenia/Richelia intracellularis, and by Trichodesmium, which fueled enough DDN to sustain the growth of other diverse diatom species and Synechococcus populations that were well adapted to limiting DIP levels. After DIP fertilization (1 µM) on day 4, an initial lag time of 10 days was necessary for the mesocosm ecosystems to start building up biomass. However, changes in community structure were already observed during this first period, with a significant drop of both Synechococcus and diatom populations, while Prochlorococcus benefited from DIP addition. At the end of this first period, corresponding to when most added DIP was consumed, the diazotroph community changed drastically and became dominated by Cyanothece-like (UCYN-C) populations, which were accompanied by a monospecific bloom of the diatom Cylindrotheca closterium. During the second period, biomass increased sharply together with primary production and N2-fixation fluxes near tripled. Diatom populations, as well as Synechococcus and nanophytoeukaryotes, showed a re-increase towards the end of the experiment, showing efficient transfer of DDN to non-diazotrophic phytoplankton.

  20. Bryophytes and macro-algal growths as a part of macrophyte monitoring in rivers used for ecological assessment

    Directory of Open Access Journals (Sweden)

    Baláži P.

    2015-01-01

    Full Text Available Altogether, 62 taxa of macrophytes including 18 bryophytes and 16 macro-algal growths were determined at 87 survey sites (73 rivers representing the both ecoregions in Slovakia (Pannonian and Carpathian during the years 2010–2013. Bryophytes represented the dominant community in the Carpathians, while the occurrence of macro-algal growths was relatively balanced in both ecoregions. Ordination analyses (DCA showed an obvious shift within studied survey sites from vascular plants to bryophytes, while macro-algal growths were more or less uniform distributed in the whole ordination space. Based on stepwise (forward selection in CCA, altitude and water surfaces as a land use type were the main environmental factors responsible for this pattern and explained 13.7% of the variability. Variation partitioning showed that the shares of environmental variables on the total variation decreased in the following order: both groups together 8.3% (landscape and geographical variables, physicochemical variables, followed by landscape and geographical variables (5.8% and purely physicochemical variables which had an insignificant effect on macrophyte composition. The importance of both groups (bryophytes and macro-algal growths in ecological assessment was also confirmed by their contribution to the mean IBMR value determined for each water body type. Anyway, our study showed that their contribution to ecological assessment is not focused only on small mountain streams where they are dominant. They may obviously affect ecological assessment also in many water body types in lowland rivers and large upland rivers as well.

  1. Macrobenthic community structure response to coastal hypoxia off Southeastern Arabian sea

    Digital Repository Service at National Institute of Oceanography (India)

    Ingole, B.S.; Periasamy, R.; De, K.

    The analysis of changes in macrobenthic community using multivariate statistical techniques has been applied to find the structure by the environmental condition. The aim of the study was to evaluate macrofaunal community patterns between natural...

  2. Generalized method for finding community structures in networks

    CERN Document Server

    Chang, Chang

    2013-01-01

    To date, most algorithms aiming to find community structures in networks mainly focus on unipartite or bipartite networks. However, to our knowledge, there is no algorithm specifically designed for the mixture network, a third type defined in our paper that represents a wide range of real-world networks. Interestingly, unipartite and bipartite networks can be viewed as limiting cases of a mixture network, suggesting that the mixture network can be considered as a general condition. Based on this observation, we propose a probabilistic model based on the link community model for a unipartite, undirected network [B. Ball, B. Karrer, and M. E. Newman, Phys. Rev. E 84, 036103 (2011)] by redefining this model in the context of a bipartite network and generalizing the bipartite network version model to a mixture network, the general condition, which can be used to find modules in unipartite, bipartite, and mixture networks in a unified framework. We show that both the model of Ball et al. (unipartite, undirected ne...

  3. Community Structure and Productivity in Western Mongolian Steppe

    Directory of Open Access Journals (Sweden)

    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.

  4. Community structure of ectomycorrhizal fungi in Swedish boreal forests

    Energy Technology Data Exchange (ETDEWEB)

    Jonsson, Lena [Swedish Univ. of Agricultural Sciences, Uppsala (Sweden). Dept. of Forest Mycology and Pathology

    1998-12-31

    The main aim of this work has been to elucidate the species composition and community structure of ectomycorrhizal fungi associated with mature trees and naturally regenerated seedlings in natural boreal forests in Sweden. Further, the effects of disturbances, such as wildfire and nitrogen inputs, were studied. Sporocarp surveys, morphological stratification and DNA-based analyses of mycorrhizas were used to describe the mycorrhizal fungal communities. In addition, a reference database useful for identifying individual mycorrhizas was developed based on analyses of sporocarp tissue. Overall, the species richness of ectomycorrhizal fungi was at least 30 to 40 times higher than that of their host trees. Naturally regenerated seedlings were colonized by the ectomycorrhizal fungal species present in the mycelial network of the old trees, indicating that the species composition will remain about the same provided that the host does not disappear. Wildfire, disturbing the fungal continuum, caused a shift in the frequencies of ectomycorrhizal fungi rather than a change in species composition. Nitrogen addition did not have any detectable effect on the abundance or species richness of mycorrhizas, but led to a decrease in sporocarp production. In all the studies, there was little resemblance between the species composition of sporocarps and that of mycorrhizas. The ITS-RFLP reference database was very useful in identifying single mycorrhizas, and proved to be a powerful tool for species identification of unknown mycorrhizas 76 refs, 2 figs, 2 tabs

  5. Plant based phosphorus recovery from wastewater via algae and macrophytes.

    Science.gov (United States)

    Shilton, Andrew N; Powell, Nicola; Guieysse, Benoit

    2012-12-01

    At present, resource recovery by irrigation of wastewater to plants is usually driven by the value of the water resource rather than phosphorus recovery. Expanded irrigation for increased phosphorus recovery may be expected as the scarcity and price of phosphorus increases, but providing the necessary treatment, storage and conveyance comes at significant expense. An alternative to taking the wastewater to the plants is instead to take the plants to the wastewater. Algal ponds and macrophyte wetlands are already in widespread use for wastewater treatment and if harvested, would require less than one-tenth of the area to recover phosphorus compared to terrestrial crops/pastures. This area could be further decreased if the phosphorus content of the macrophytes and algae biomass was tripled from 1% to 3% via luxury uptake. While this and many other opportunities for plant based recovery of phosphorus exist, e.g. offshore cultivation, much of this technology development is still in its infancy. Research that enhances our understanding of how to maximise phosphorus uptake and harvest yields; and further add value to the biomass for reuse would see the recovery of phosphorus via plants become an important solution in the future.

  6. Efficiency of aquatic macrophytes to treat Nile tilapia pond effluents

    Directory of Open Access Journals (Sweden)

    Henry-Silva Gustavo Gonzaga

    2006-01-01

    Full Text Available The effluents from fish farming can increase the quantity of suspended solids and promote the enrichment of nitrogen and phosphorus in aquatic ecosystems. In this context, the aim of this work was to evaluate the efficiency of three species of floating aquatic macrophytes (Eichhornia crassipes, Pistia stratiotes and Salvinia molesta to treat effluents from Nile tilapia culture ponds. The effluent originated from a 1,000-m² pond stocked with 2,000 male Nile tilapia Oreochromis niloticus. The treatment systems consisted of 12 experimental tanks, three tanks for each macrophyte species, and three control tanks (without plants. Water samples were collected from the: (i fish pond source water, (ii effluent from fish pond and (iii effluents from the treatment tanks. The following water variables were evaluated: turbidity, total and dissolved nitrogen, ammoniacal-N, nitrate-N, nitrite-N, total phosphorus and dissolved phosphorus. E. crassipes and P. stratiotes were more efficient in total phosphorus removal (82.0% and 83.3%, respectively and total nitrogen removal (46.1% and 43.9%, respectively than the S. molesta (72.1% total phosphorus and 42.7% total nitrogen and the control (50.3% total phosphorus and 22.8% total nitrogen, indicating that the treated effluents may be reused in the aquaculture activity.

  7. Measuring and Modeling Bipartite Graphs with Community Structure

    CERN Document Server

    Aksoy, Sinan; Pinar, Ali

    2016-01-01

    Network science is a powerful tool for analyzing complex systems in fields ranging from sociology to engineering to biology. This paper is focused on generative models of bipartite graphs, also known as two-way graphs. We propose two generative models that can be easily tuned to reproduce the characteristics of real-world networks, not just qualitatively, but quantitatively. The measurements we consider are the degree distributions and the bipartite clustering coefficient, which we refer to as the metamorphosis coefficient. We define edge, node, and degreewise metamorphosis coefficients, enabling a more detailed understand of the bipartite community structure. Our proposed bipartite Chung-Lu model is able to reproduce real-world degree distributions, and our proposed bipartite "BTER" model reproduces both the degree distributions as well as the degreewise metamorphosis coefficients. We demonstrate the effectiveness of these models on several real-world data sets.

  8. Pregnancy and birth in an indigenous Huichol community: from structural violence to structural policy responses.

    Science.gov (United States)

    Gamlin, Jennie B; Hawkes, Sarah J

    2015-01-01

    Mexico's indigenous regions are characterised by socio-economic marginalisation and poor health outcomes and the Maternal Mortality Rate in indigenous communities continues to be around six times higher than the national rate. Using as a case study the Huichol community of North-Western Mexico we will discuss how institutional health and welfare programmes which aim to address accepted risk factors for maternal health are undermined by a series of structural barriers which put indigenous women especially in harm's way. Semi-structured interviews and observational data were gathered between 2009 and 2011 in highland communities and on coastal tobacco plantations to where a large number of this ethnic group migrate. Many Huichol women birth alone, and to facilitate this process they maintain a low nutritional intake to reduce their infant's growth and seek spiritual guidance during pregnancy from a shaman. These practices are reinforced by feelings of shame and humiliation encountered when using institutional health provision. These are some of the structural barriers to care that need to be addressed. Effective interventions could include addressing the training of health professionals, focusing on educational inequalities and the structural determinants of poverty whilst designing locally specific programmes that encourage acceptance of available health care.

  9. Unraveling the Molecular Mechanisms Underlying the Nasopharyngeal Bacterial Community Structure

    Directory of Open Access Journals (Sweden)

    Wouter A. A. de Steenhuijsen Piters

    2016-03-01

    Full Text Available The upper respiratory tract is colonized by a diverse array of commensal bacteria that harbor potential pathogens, such as Streptococcus pneumoniae. As long as the local microbial ecosystem—also called “microbiome”—is in balance, these potentially pathogenic bacterial residents cause no harm to the host. However, similar to macrobiological ecosystems, when the bacterial community structure gets perturbed, potential pathogens can overtake the niche and cause mild to severe infections. Recent studies using next-generation sequencing show that S. pneumoniae, as well as other potential pathogens, might be kept at bay by certain commensal bacteria, including Corynebacterium and Dolosigranulum spp. Bomar and colleagues are the first to explore a specific biological mechanism contributing to the antagonistic interaction between Corynebacterium accolens and S. pneumoniae in vitro [L. Bomar, S. D. Brugger, B. H. Yost, S. S. Davies, K. P. Lemon, mBio 7(1:e01725-15, 2016, doi:10.1128/mBio.01725-15]. The authors comprehensively show that C. accolens is capable of hydrolyzing host triacylglycerols into free fatty acids, which display antipneumococcal properties, suggesting that these bacteria might contribute to the containment of pneumococcus. This work exemplifies how molecular epidemiological findings can lay the foundation for mechanistic studies to elucidate the host-microbe and microbial interspecies interactions underlying the bacterial community structure. Next, translation of these results to an in vivo setting seems necessary to unveil the magnitude and importance of the observed effect in its natural, polymicrobial setting.

  10. Responses of aquatic macrophyte cover and productivity to flooding variability on the Amazon floodplain.

    Science.gov (United States)

    Silva, Thiago S F; Melack, John M; Novo, Evlyn M L M

    2013-11-01

    Macrophyte net primary productivity (NPP) is a significant but understudied component of the carbon budget in large Amazonian floodplains. Annual NPP is determined by the interaction between stem elongation (vertical growth) and plant cover changes (horizontal expansion), each affected differently by flood duration and amplitude. Therefore, hydrological changes as predicted for the Amazon basin could result in significant changes in annual macrophyte NPP. This study investigates the responses of macrophyte horizontal expansion and vertical growth to flooding variability, and its possible effects on the contribution of macrophytes to the carbon budget of Amazonian floodplains. Monthly macrophyte cover was estimated using satellite imagery for the 2003-2004 and 2004-2005 hydrological years, and biomass was measured in situ between 2003 and 2004. Regression models between macrophyte variables and river-stage data were used to build a semiempirical model of macrophyte NPP as a function of water level. Historical river-stage records (1970-2011) were used to simulate variations in NPP, as a function of annual flooding. Vertical growth varied by a factor of ca. 2 over the simulated years, whereas minimum and maximum annual cover varied by ca. 3.5 and 1.5, respectively. Results suggest that these processes act in opposite directions to determine macrophyte NPP, with larger sensitivity to changes in vertical growth, and thus maximum flooding levels. Years with uncommonly large flooding amplitude resulted in the highest NPP values, as both horizontal expansion and vertical growth were enhanced under these conditions. Over the simulated period, annual NPP varied by ca. 1.5 (1.06-1.63 TgC yr(-1) ). A small increasing trend in flooding amplitude, and by extension NPP, was observed for the studied period. Variability in growth rates caused by local biotic and abiotic factors, and the lack of knowledge on macrophyte physiological responses to extreme hydrological conditions

  11. ORGANIC VS CONVENTIONAL: SOIL NEMATODE COMMUNITY STRUCTURE AND FUNCTION.

    Science.gov (United States)

    Kapp, C; Storey, S G; Malan, A P

    2014-01-01

    Global increases in human population are creating an ever-greater need for food production. Poor soil management practices have degraded soil to such an extent that rapidly improved management practices is the only way to ensure future food demands. In South Africa, deciduous fruit producers are realising the need for soil health, and for an increased understanding of the benefits of soil ecology, to ensure sustainable fruit production. This depends heavily on improved orchard management. Conventional farming relies on the addition of artificial fertilizers, and the application of chemicals, to prevent or minimise, the effects of the soil stages of pest insects, and of plant-parasitic nematodes. Currently, there is resistance toward conventional farming practices, which, it is believed, diminishes biodiversity within the soil. The study aimed to establish the soil nematode community structure and function in organically, and conventionally, managed deciduous fruit orchards. This was done by determining the abundance, the diversity, and the functionality of the naturally occurring free-living, and plant-parasitic, nematodes in deciduous fruit orchards in the Western Cape province of South Africa. The objective of the study was to form the basis for the use of nematodes as future indicators of soil health in deciduous fruit orchards. Orchards from neighbouring organic, and conventional, apricot farms, and from an organic apple orchard, were studied. All the nematodes were quantified, and identified, to family level. The five nematode-classified trophic groups were found at each site, while 14 families were identified in each orchard, respectively. Herbivores were dominant in all the orchards surveyed. Organic apples had the fewest herbivores and fungivores, with the highest number of carnivores. When comparing organic with conventional apricot orchards, higher numbers of plant-parasitic nematodes were found in the organic apricot orchards. The Maturity Index (MI

  12. 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.

  13. Temporal and spatial distribution of macrophytes in the Gruža Reservoir (Serbia

    Directory of Open Access Journals (Sweden)

    Topuzović Marina

    2009-01-01

    Full Text Available A survey of aquatic macrophytes in the Gruža Reservoir (Serbia was conducted during the period 2007-2008. Detailed data on the actual condition of macrophytes were established and compared between four parts of the reservoir. The distributions of most aquatic macrophytes of the Gruža Reservoir are heterogeneous, with different values of the MMT and MMO indices and low values of the distribution ratio. Quantitative analysis indicates that the greatest diversity and abundance of species can be found in those parts of the reservoir with the shallowest water and greatest indentation of the shoreline.

  14. Nematode community structure in the vicinity of a metallurgical factory.

    Science.gov (United States)

    Salamún, Peter; Renčo, Marek; Miklisová, Dana; Hanzelová, Vladimíra

    2011-12-01

    Soil nematode communities (taxa composition, trophic structure, ecological indices) in the area of metallurgical factory (Oravské ferozliatinárske závody) in Široká, Northern Slovakia were investigated in 2009. The factory belongs to main sources of emissions originated by ferroalloy production in this region. Four sites (meadows) were selected in a downwind direction from the factory: site A was located 0.85 km far from the factory, and the other sites were maintained in approximately 2-km intervals from each other. Chemical analysis of soil samples showed low concentrations of heavy metals (As, Cd, Cr, Cu, Ni, Pb and Zn), with all values being under Slovak limit concentrations of heavy metals in soils. Only the Cd content in the soil sample from site A slightly exceeded the allowable threshold, but it was decreasing with the distance from the factory, similarly as remaining metals except Cr, with slightly increasing trend of concentration. Within 64 identified nematode genera, the Helicotylenchus, Paratylenchus, Pratylenchus, Acrobeloides, Cephalobus and Rhabditis were most common and eudominant. This was clearly reflected on the trophic structure of nematode communities, where plant feeding nematodes and bacteriovorous prevailed. Significant negative correlation (P < 0.05) was observed between the abundance of bacteriovores and the concentration of Cu in the soil. On the other hand, fungivores showed significant correlation with Ni and Cr (P < 0.05) as well as predators with Cd, Pb and Zn contents in the soil (P < 0.01). The highly significant correlation (P < 0.05; P < 0.01) was found between As, Cd, Ni, Pb and Zn and Maturity Index 2-5. A negative relationship was detected between Maturity Index and the concentration of Cr in the soil (P < 0.01). On the other hand, Cu was in positive correlation with MI values. The MI, reflecting the degree of disturbances and changes in the structure and function of the soil ecosystem, was found

  15. Quantitative and qualitative characteristics of dissolved organic matter from eight dominant aquatic macrophytes in Lake Dianchi, China.

    Science.gov (United States)

    Qu, Xiaoxia; Xie, Li; Lin, Ying; Bai, Yingchen; Zhu, Yuanrong; Xie, Fazhi; Giesy, John P; Wu, Fengchang

    2013-10-01

    The aim of this research was to determine and compare the quantitative and qualitative characteristics of dissolved organic matters (DOM) from eight aquatic macrophytes in a eutrophic lake. C, H, N, and P in ground dry leaves and C, N, and P in DOM of the species were determined, and C/N, C/P, C/H, DOC/C, TDN/N, TDP/P, DOC/TDN, and DOC/TDP were calculated. Chemical structures of the DOM were characterized by the use of multiple techniques including UV-visible, FT-IR, and (13)C CP/MAS spectra. The results showed subtle differences in quantity and quality of DOM among species and life-forms. Except oriental pepper which had a C/H of 0.7, C/H of all the other species was 0.6. C/N and C/P of ground leaves was 10.5-17.3 and 79.4-225.3, respectively, which were greater in floating and submerged species than in the others. Parrot feather also had a small C/P (102.8). DOC/C, TDN/N, and TDP/P were 7.6-16.8, 5.5-22.6, and 22.9-45.6 %, respectively. Except C/N in emergent and riparian species, C/N in the other species and C/P in all the species were lower in their DOM than in the ground leaves. DOM of the macrophytes had a SUVA254 value of 0.83-1.80. The FT-IR and (13)C NMR spectra indicated that the DOM mainly contained polysaccharides and/or amino acids/proteins. Percent of carbohydrates in the DOM was 37.3-66.5 % and was highest in parrot feather (66.5 %) and crofton weed (61.5 %). DOM of water hyacinth, water lettuce, and sago pondweed may have the greatest content of proteins. Aromaticity of the DOM was from 6.9 % in water lettuce to 17.8 % in oriental pepper. DOM of the macrophytes was also different in polarity and percent of Ar-OH. Distinguished characteristics in quantity and quality of the macrophyte-derived DOM may induce unique environmental consequences in the lake systems.

  16. Community structure discovery method based on the Gaussian kernel similarity matrix

    Science.gov (United States)

    Guo, Chonghui; Zhao, Haipeng

    2012-03-01

    Community structure discovery in complex networks is a popular issue, and overlapping community structure discovery in academic research has become one of the hot spots. Based on the Gaussian kernel similarity matrix and spectral bisection, this paper proposes a new community structure discovery method. First, by adjusting the Gaussian kernel parameter to change the scale of similarity, we can find the corresponding non-overlapping community structure when the value of the modularity is the largest relatively. Second, the changes of the Gaussian kernel parameter would lead to the unstable nodes jumping off, so with a slight change in method of non-overlapping community discovery, we can find the overlapping community nodes. Finally, synthetic data, karate club and political books datasets are used to test the proposed method, comparing with some other community discovery methods, to demonstrate the feasibility and effectiveness of this method.

  17. Microzooplankton herbivory and community structure in the Amundsen Sea, Antarctica

    Science.gov (United States)

    Yang, Eun Jin; Jiang, Yong; Lee, SangHoon

    2016-01-01

    We examined microzooplankton abundance, community structure, and grazing impact on phytoplankton in the Amundsen Sea, Western Antarctica, during the early austral summer from December 2010 to January 2011. Our study area was divided into three regions based on topography, hydrographic properties, and trophic conditions: (1) the Oceanic Zone (OZ), with free sea ice and low phytoplankton biomass dominated by diatoms; (2) the Sea Ice Zone (SIZ), covered by heavy sea ice with colder water, lower salinity, and dominated by diatoms; and (3) the Amundsen Sea Polynya (ASP), with high phytoplankton biomass dominated by Phaeocystis antarctica. Microzooplankton biomass and communities associated with phytoplankton biomass and composition varied among regions. Heterotrophic dinoflagellates (HDF) were the most significant grazers in the ASP and OZ, whereas ciliates co-dominated with HDF in the SIZ. Microzooplankton grazing impact is significant in our study area, particularly in the ASP, and consumed 55.4-107.6% of phytoplankton production (average 77.3%), with grazing impact increasing with prey and grazer biomass. This result implies that a significant proportion of the phytoplankton production is not removed by sinking or other grazers but grazed by microzooplankton. Compared with diatom-based systems, Phaeocystis-based production would be largely remineralized and/or channeled through the microbial food web through microzooplankton grazing. In these waters the major herbivorous fate of phytoplankton is likely mediated by the microzooplankton population. Our study confirms the importance of herbivorous protists in the planktonic ecosystems of high latitudes. In conclusion, microzooplankton herbivory may be a driving force controlling phytoplankton growth in early summer in the Amundsen Sea, particularly in the ASP.

  18. Scalably Revealing the Dynamics of Soft Community Structure in Complex Networks

    Institute of Scientific and Technical Information of China (English)

    LI Huijia; LI Huiying

    2016-01-01

    Revealing the dynamics of community structure is of great concern for scientists from many fields.Specifically,how to quantify the dynamic details of soft community structure is a very interesting topic.In this paper,the authors propose a novel framework to study the scalable dynamic behavior of the soft community structure.First,the authors model the Potts dynamics to detect community structure using a "soft" Markov process.Then the soft stability of in a multiscale view is proposed to naturally uncover the local uniform behavior of spin values across multiple hierarchical levels.Finally,a new partition index is developed to detect fuzzy communities based on the stability and the dynamical information.Experiments on the both synthetically generated and real-world networks verify that the framework can be used to uncover hierarchical community structures effectively and efficiently.

  19. Detecting community structure in complex networks using an interaction optimization process

    Science.gov (United States)

    Kim, Paul; Kim, Sangwook

    2017-01-01

    Most complex networks contain community structures. Detecting these community structures is important for understanding and controlling the networks. Most community detection methods use network topology and edge density to identify optimal communities; however, these methods have a high computational complexity and are sensitive to network forms and types. To address these problems, in this paper, we propose an algorithm that uses an interaction optimization process to detect community structures in complex networks. This algorithm efficiently searches the candidates of optimal communities by optimizing the interactions of the members within each community based on the concept of greedy optimization. During this process, each candidate is evaluated using an interaction-based community model. This model quickly and accurately measures the difference between the quantity and quality of intra- and inter-community interactions. We test our algorithm on several benchmark networks with known community structures that include diverse communities detected by other methods. Additionally, after applying our algorithm to several real-world complex networks, we compare our algorithm with other methods. We find that the structure quality and coverage results achieved by our algorithm surpass those of the other methods.

  20. Interactions between nitrifying and denitrifying bacteria in gnotobiotic microcosms planted with the emergent macrophyte Glyceria maxima

    NARCIS (Netherlands)

    Bodelier, P.L.E.; Duyts, H.; Blom, C.W.P.M.; Laanbroek, H.J.

    1998-01-01

    The population dynamics of the chemolithoautotrophic nitrifiers Nitrosomonas europaea and Nitrobacter winogradskyi were studied in gnotobiotic microcosms fed with ammonium in response to the presence or absence of the emergent macrophyte Glyceria maxima and the heterotrophic denitrifying bacterium P

  1. Long-term allelopathic control of phytoplankton by the submerged macrophyte Elodea nuttallii

    NARCIS (Netherlands)

    Vanderstukken, M.; Declerck, S.A.J.; Decaestecker, E.; Muylaert, K.

    2014-01-01

    Keywords: allelochemicals; chemical ecology; competition; nutrient limitation; shallow lakes Summary 1.It is well known that submerged macrophytes can suppress phytoplankton blooms in lakes and thus promote water quality and biodiversity. One of the possible mechanisms through which submerged macrop

  2. Studies on heavy metal accumulation in aquatic macrophytes from Sevan (Armenia) and Carambolim (India) lake systems

    Digital Repository Service at National Institute of Oceanography (India)

    Vardanyan, L.G.; Ingole, B.S.

    in root system. The representative macrophytes from two different physiographic locations show similar trends and order in accumulating different metals generally. Of the 14 metals investigated, 9 (Ca, Fe, Al, Cr, Cu, Ba, Ti, Co and Pb) showed higher rates...

  3. Three-Gorge Dam influences wetland macrophytes in middle and lower reaches of Yangtze

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Dongting Lake, located in the middle and lower reaches of Yangtze, is regarded as a lake during the water swelling period and a continent in the ebbing period. The construction of the Three-Gorge Dam has influenced the water level of Dongting Lake and the growth of wetland macrophytes in the area. In this study, the growth of main species of wetland macrophytes, such as Carex and Phragmites at Dongting Lake, was observed, and the hydraulic gradient, one of the main factors dominating the abundance and distribution of wetland macrophytes, was also studied at six stations in Dongting Lake area and the effect of the Three-Gorge Dam construction on the growth of wetland macrophytes was observed.

  4. Closely related freshwater macrophyte species, Ceratophyllum demersum and em>C. submersum, differ in temperature response

    DEFF Research Database (Denmark)

    Hyldgaard, Benita; Sorrell, Brian Keith; Brix, Hans

    2014-01-01

    1. The importance of temperature responses of photosynthesis and respiration in determining species distributions was compared in two closely related freshwater macrophytes, Ceratophyllum demersum and C. submersum. The two species differed significantly in response to temperature in the short and...

  5. Effects of litter on substrate conditions and growth of emergent macrophytes

    NARCIS (Netherlands)

    Van der Putten, W.H.; Peters, B.A.M.; Van den Berg, R.S.

    1997-01-01

    Three successive emergent macrophytes (Typha latifolia L., Phragmites australis (Cav.) Steudel and Glyceria maxima (Hartman) Holmbly) were each grown in substrates collected from three different zones of shoreline vegetation development (non- vegetated sediment, the interface between T. latifolia an

  6. Nitrogen or phosphorus limitation in lakes and its impact on phytoplankton biomass and submerged macrophyte cover

    DEFF Research Database (Denmark)

    Søndergaard, Martin; Lauridsen, Torben Linding; Johansson, Liselotte Sander

    2017-01-01

    macrophyte cover. We conclude that P is of key importance for the ecological quality of Danish lakes but that increased N concentrations, particularly in shallow lakes with moderate to high TP, may have significantly adverse effects on lake water quality and ecological status in summer.......We used data on nutrients, chlorophyll a (Chla) and submerged macrophyte cover from up to 817 Danish lakes to elucidate seasonal variations in nitrogen (N) and phosphorus (P) concentrations and to study the impact of N or its role in combination with P. In both deep and shallow lakes, we found...... related more strongly to TP than to TN, but at high TP concentrations TN explained more of the variability in Chla than TP. Macrophyte cover tended to decrease at increasing TN when TP was between 0.1 and 0.4 mg/l. At macrophyte cover above 20%, Chla was considerably lower compared with lakes with low...

  7. Capabilities of Seven Species of Aquatic Macrophytes for Phytoremediation of Pentachlorophenol Contaminated Sediment

    Science.gov (United States)

    Zhao, Liangyuan; Guo, Weijie; Li, Qingyun; Li, Huan; Zhao, Weihua; Cao, Xiaohuan

    2017-01-01

    Sediments are regarded as the ultimate sink of pentachlorophenol(PCP) in aquatic environment, and capabilities of seven species of aquatic macrophytes for remediating PCP contaminated sediment were investigated. Seven species of aquatic macrophytes could significantly accelerate the degradation of PCP in sediments. Among all, canna indica L., Acorus calamus L. and Iris tectorum Maxim. can be used as efficient alternative plants for remediation of PCP contaminated sediment, which attained 98%, 92% and 88% of PCP removal in sediments, respectively. PCP was detected only in root tissues and the uptake was closely related to the root lipid contents of seven plants. The presence of seven aquatic macrophytes significantly increased microbial populations and the activities of dehydrogenase compared with control sediments, indicating that rhizosphere microorganism played important role in the remediation process. In conclusion, seven species of aquatic macrophytes may act as promising tools for the PCP phytoremediation in aquatic environment, especially Canna indica L., Acorus calamus L. and Iris tectorum Maxim.

  8. Long-term allelopathic control of phytoplankton by the submerged macrophyte Elodea nuttallii

    NARCIS (Netherlands)

    Vanderstukken, M.; Declerck, S.A.J.; Decaestecker, E.; Muylaert, K.

    2014-01-01

    Keywords: allelochemicals; chemical ecology; competition; nutrient limitation; shallow lakes Summary 1.It is well known that submerged macrophytes can suppress phytoplankton blooms in lakes and thus promote water quality and biodiversity. One of the possible mechanisms through which submerged

  9. Haloacetic acids in the aquatic environment. Part I: macrophyte toxicity.

    Science.gov (United States)

    Hanson, Mark L; Solomon, Keith R

    2004-08-01

    Haloacetic acids (HAAs) are contaminants of aquatic ecosystems with numerous sources, both anthropogenic and natural. The toxicity of HAAs to aquatic plants is generally uncharacterized. Laboratory tests were conducted with three macrophytes (Lemna gibba, Myriophyllum sibiricum and Myriophyllum spicatum) to assess the toxicity of five HAAs. Myriophyllum spp. has been proposed as required test species for pesticide registration in North America, but few studies have been conducted under standard test conditions. The HAAs in the present experiments were monochloroacetic acid (MCA), dichloroacetic acid (DCA), trichloroacetic acid (TCA), trifluoroacetic acid (TFA) and chlorodifluoroacetic acid (CDFA). MCA was the most toxic to Myriophyllum spp. with EC50 values ranging from 8 to 12.4 mg/l depending on the endpoint, followed by DCA (EC50 range 62-722.5 mg/l), TCA (EC50 range 49.5-1702.6 mg/l), CDFA (EC50 range 105.3 to >10,000 mg/l) and with TFA (EC50 range 222.1 to 10,000 mg/l) the least toxic. Generally, L. gibba was less sensitive to HAA toxicity than Myriophyllum spp., with the difference in toxicity between them approximately threefold. The range of toxicity within Myriophyllum spp. was normally less than twofold. Statistically, plant length and node number were the most sensitive endpoints as they had the lowest observed coefficients of variation, but they were not the most sensitive to HAA toxicity. Toxicological sensitivity of endpoints varied depending on the measure of effect chosen and the HAA, with morphological endpoints usually an order of magnitude more sensitive than pigments for all plant species. Overall, mass and root measures tended to be the most sensitive indicators of HAA toxicity. The data from this paper were subsequently used in an ecological risk assessment for HAAs and aquatic plants. The assessment found HAAs to be of low risk to aquatic macrophytes and the results are described in the second manuscript of this series.

  10. Experimental Effects of Lime Application on Aquatic Macrophytes: 3. Growth Response Versus Exposure Time

    Science.gov (United States)

    2008-01-01

    ERDC/TN APCRP-EA-17 January 2008 Experimental Effects of Lime Application on Aquatic Macrophytes : 3. Growth Response Versus Exposure Time by William...be effective in both suppressing submersed macrophyte growth and changing species composition (Babin et al. 1992; Chambers et al. 2001; Prepas et al...16 cm height) filled with homogenized sediment (obtained from Eau Galle Reservoir , WI; see James et al. (2005) for a description of sediment

  11. The use of macrophytes for heavy metal pollution control in urban wetlands

    OpenAIRE

    Zhang, Tiantian

    1990-01-01

    A literature survey has been undertaken to identify the role and function of aquatic macrophytes in the removal of contaminants from polluted surface waters. The survey focussed primarily on heavy metals, however nitrate, phosphate and hydrocarbon removal are also discussed and the application of aquatic macrophytes in wastewater treatment systems is also described. The objectives of the research are: To determine heavy metal variations in water, sediment and plant tissues in both fiel...

  12. Unusual bacterioplankton community structure in ultra-oligotrophic Crater Lake

    Science.gov (United States)

    Urbach, Ena; Vergin, Kevin L.; Morse, Ariel

    2001-01-01

    The bacterioplankton assemblage in Crater Lake, Oregon (U.S.A.), is different from communities found in other oxygenated lakes, as demonstrated by four small subunit ribosomal ribonucleic acid (SSU rRNA) gene clone libraries and oligonucleotide probe hybridization to RNA from lake water. Populations in the euphotic zone of this deep (589 m), oligotrophic caldera lake are dominated by two phylogenetic clusters of currently uncultivated bacteria: CL120-10, a newly identified cluster in the verrucomicrobiales, and ACK4 actinomycetes, known as a minor constituent of bacterioplankton in other lakes. Deep-water populations at 300 and 500 m are dominated by a different pair of uncultivated taxa: CL500-11, a novel cluster in the green nonsulfur bacteria, and group I marine crenarchaeota. b-Proteobacteria, dominant in most other freshwater environments, are relatively rare in Crater Lake (marine crenarchaeota and green nonsulfur bacteria. Comparison of Crater Lake to other lakes studied by rRNA methods suggests that selective factors structuring Crater Lake bacterioplankton populations may include low concentrations of available trace metals and dissolved organic matter, chemistry of infiltrating hydrothermal waters, and irradiation by high levels of ultraviolet light.

  13. 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.

  14. Interspecific associations and community structure: A local survey and analysis in a grass community

    Directory of Open Access Journals (Sweden)

    WenJun Zhang

    2014-09-01

    Full Text Available Interspecific associations in the plant community may help to understand the self-organizing assembly and succession of the community. In present study, Pearson correlation, net correlation, Spearman rank correlation, and point correlation were used to detect the interspecific (inter-family associations of grass species (families using the sampling data collected in a grass community of Zhuhai, China. We found that most associations between grass species (families were positive associations. The competition/interference/niche separation between grass species (families was not significant. A lot of pairs of grass species and families with statistically significant interspecific (inter-family associations based on four correlation measures were discovered. Cluster trees for grass species/families were obtained by using cluster analysis. Relationship among positive/negative associations, interspecific relationship and community succession/stability/robustness was discussed. I held that species with significant positive or negative associations are generally keystone species in the community. Although both negative and positive associations occur in the community succession, the adaptation and selection will finally result in the successful coexistence of the species with significant positive associations in the climax community. As the advance of community succession, the significant positive associations increase and maximize in climax community, and the significant negative associations increase to a maximum and then decline into climax community. Dominance of significant positive associations in the climax community means the relative stablility and equilibrium of the community. No significant associations usually account for the majority of possible interspecific associations at each phase of community succession. They guarantee the robustness of community. They are candidates of keystone species. Lose of some existing keystone species might be

  15. Growth of common brackish marsh macrophytes under altered hydrology and salinity regimes

    Science.gov (United States)

    Howard, Rebecca J.; Biagas, Janelda M.; Allain, Larry K.

    2016-01-01

    Coastal marsh plants are increasingly subject to physicochemical stressors under rising sea levels, and the maintenance of marsh ecological functions can depend on the ability of individual species and communities to tolerate or adapt to altered conditions. We conducted a greenhouse experiment to identify hydrology and salinity effects on growth of three common brackish marsh macrophytes of coastal Florida, USA: Distichlis spicata, Juncus roemerianus, and Spartina bakeri. The species were potted as monocultures and exposed to three salinities (0, 15, or 28 psu) and two hydrologic conditions (saturated, tidal) over 22 months. Final stem density of J. roemerianus and S. bakeri did not differ among treatments. In D. spicata, however, stem density was lowest at 28 psu and lower in tidal compared to saturated conditions. Mean stem height of all species was lowest at 28 psu. Aboveground biomass of J. roemerianus was not affected by the treatments, but in D. spicata andS. bakeri it was lowest at 28 psu. Results indicated that J. roemerianus was the most adaptable species and may, therefore, be more resilient to climate-change driven stressors. However, plant-plant interactions such as interspecific competition and facilitation can alter the response of individual species to environmental factors.

  16. Aquatic macrophytes as feeding site for small fishes in the Rosana Reservoir, Paranapanema River, Southeastern Brazil

    Directory of Open Access Journals (Sweden)

    Casatti L.

    2003-01-01

    Full Text Available In the present investigation we studied the feeding habits of the fishes associated with aquatic macrophytes in the Rosana Reservoir, southeastern Brazil. Twenty fish species were collected during four field trips, regularly distributed across the dry and wet seasons. Focal snorkeling observations of the fishes were made over a total of six hours. Nine species were present in abundances of more than 1% and, therefore, had their feeding habits analyzed. Hemigrammus marginatus, Roeboides paranensis, Hyphessobrycon eques, Astyanax altiparanae, Serrasalmus spilopleura, and Bryconamericus stramineus were predominantly invertivores, with predominance of aquatic insects (Diptera, Ephemeroptera, and Trichoptera immatures among their food items. The predominantly algivores were Apareiodon affinis, Serrapinnus notomelas, and Satanoperca pappaterra, with high frequency of filamentous blue-green algae, diatoms, clorophyts, and periderm. The different microhabitat exploitation plus diet composition suggests partitioning of resources and absence of food competition among the most representative fish species in the studied community, indicating the importance of the naturalistic approach to fish ecology studies.

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

    Directory of Open Access Journals (Sweden)

    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.

  18. Growth rate, protein:RNA ratio and stoichiometric homeostasis of submerged macrophytes under eutrophication stress

    Directory of Open Access Journals (Sweden)

    Xing W.

    2016-01-01

    Full Text Available Growth rate hypothesis (GRH and stoichiometric homeostasis of photoautotrophs have always been questioned. However, little is known about GRH and stoichiometric homeostasis of aquatic plants, especially submerged macrophytes. Therefore, we aim to test the GRH and explore stoichiometric homeostasis of four freshwater submerged macrophytes under eutrophication stress. At the single species level and the multi-species level, N:P ratios of Potamogeton maackianus, Myriophyllum spicatum, Vallisneria natans and Ceratophyllum demersum had no consistent trends with growth rates. However, protein:RNA ratios of P. maackianus, M. spicatum and V. natans all correlated negatively with growth rates, demonstrating GRH can apply to freshwater submerged macrophytes, even though they are threatening by eutrophication stress. Protein:RNA ratios positively correlated with N:P ratios in culture media and tissues in submerged macrophytes except in P. maackianus (30d, suggesting effects of varying N:P ratios in culture media on protein:RNA ratios are basically in concert with tissue N:P ratios under short-time eutrophication stress. Stoichiometric homeostasis coefficients (HN:P indicated submerged macrophytes have weak homeostasis. Stoichiometric homeostasis of V. natans was stronger than those of P. maackianus, M. spicatum and C. demersum. The differences in GRH and homeostasis of the four submerged macrophytes may be due to species traits.

  19. Potts model based on a Markov process computation solves the community structure problem effectively.

    Science.gov (United States)

    Li, Hui-Jia; Wang, Yong; Wu, Ling-Yun; Zhang, Junhua; Zhang, Xiang-Sun

    2012-07-01

    The Potts model is a powerful tool to uncover community structure in complex networks. Here, we propose a framework to reveal the optimal number of communities and stability of network structure by quantitatively analyzing the dynamics of the Potts model. Specifically we model the community structure detection Potts procedure by a Markov process, which has a clear mathematical explanation. Then we show that the local uniform behavior of spin values across multiple timescales in the representation of the Markov variables could naturally reveal the network's hierarchical community structure. In addition, critical topological information regarding multivariate spin configuration could also be inferred from the spectral signatures of the Markov process. Finally an algorithm is developed to determine fuzzy communities based on the optimal number of communities and the stability across multiple timescales. The effectiveness and efficiency of our algorithm are theoretically analyzed as well as experimentally validated.

  20. Potts model based on a Markov process computation solves the community structure problem effectively

    CERN Document Server

    Li, Hui-Jia; Wu, Ling-Yun; Zhang, Junhua; Zhang, Xiang-Sun

    2015-01-01

    Potts model is a powerful tool to uncover community structure in complex networks. Here, we propose a new framework to reveal the optimal number of communities and stability of network structure by quantitatively analyzing the dynamics of Potts model. Specifically we model the community structure detection Potts procedure by a Markov process, which has a clear mathematical explanation. Then we show that the local uniform behavior of spin values across multiple timescales in the representation of the Markov variables could naturally reveal the network's hierarchical community structure. In addition, critical topological information regarding to multivariate spin configuration could also be inferred from the spectral signatures of the Markov process. Finally an algorithm is developed to determine fuzzy communities based on the optimal number of communities and the stability across multiple timescales. The effectiveness and efficiency of our algorithm are theoretically analyzed as well as experimentally validate...

  1. Structure in Community College Career-Technical Programs: A Qualitative Analysis. CCRC Working Paper No. 50

    Science.gov (United States)

    Van Noy, Michelle; Weiss, Madeline Joy; Jenkins, Davis; Barnett, Elisabeth A.; Wachen, John

    2012-01-01

    Using data obtained from interviews and program websites at Washington community and technical colleges, the authors of this study examine the structure of community college career-technical programs in allied health, business and marketing, computer and information studies, and mechanics and repair. A framework for structure with four…

  2. 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…

  3. Effect of Elodea nuttallii roots on bacterial communities and MMHg proportion in a Hg polluted sediment.

    Directory of Open Access Journals (Sweden)

    Nicole Regier

    Full Text Available The objective of this study was to assess the effect of a rooted macrophyte Elodea nuttallii on rhizosphere bacterial communities in Hg contaminated sediments. Specimens of E. nuttallii were exposed to sediments from the Hg contaminated Babeni reservoir (Olt River, Romania in our microcosm. Plants were allowed to grow for two months until they occupied the entirety of the sediments. Total Hg and MMHg were analysed in sediments where an increased MMHg percentage of the total Hg in pore water of rhizosphere sediments was found. E. nuttallii roots also significantly changed the bacterial community structure in rhizosphere sediments compared to bulk sediments. Deltaproteobacteria dominated the rhizosphere bacterial community where members of Geobacteraceae within the Desulfuromonadales and Desulfobacteraceae were identified. Two bacterial operational taxonomic units (OTUs which were phylogenetically related to sulfate-reducing bacteria (SRB became abundant in the rhizosphere. We suggest that these phylotypes could be potentially methylating bacteria and might be responsible for the higher MMHg percentage of the total Hg in rhizosphere sediments. However, SRB were not significantly favoured in rhizosphere sediments as shown by qPCR. Our findings support the hypothesis that rooted macrophytes created a microenvironment favorable for Hg methylation. The presence of E. nuttallii in Hg contaminated sediments should therefore not be overlooked.

  4. Effect of Elodea nuttallii roots on bacterial communities and MMHg proportion in a Hg polluted sediment.

    Science.gov (United States)

    Regier, Nicole; Frey, Beat; Converse, Brandon; Roden, Eric; Grosse-Honebrink, Alexander; Bravo, Andrea Garcia; Cosio, Claudia

    2012-01-01

    The objective of this study was to assess the effect of a rooted macrophyte Elodea nuttallii on rhizosphere bacterial communities in Hg contaminated sediments. Specimens of E. nuttallii were exposed to sediments from the Hg contaminated Babeni reservoir (Olt River, Romania) in our microcosm. Plants were allowed to grow for two months until they occupied the entirety of the sediments. Total Hg and MMHg were analysed in sediments where an increased MMHg percentage of the total Hg in pore water of rhizosphere sediments was found. E. nuttallii roots also significantly changed the bacterial community structure in rhizosphere sediments compared to bulk sediments. Deltaproteobacteria dominated the rhizosphere bacterial community where members of Geobacteraceae within the Desulfuromonadales and Desulfobacteraceae were identified. Two bacterial operational taxonomic units (OTUs) which were phylogenetically related to sulfate-reducing bacteria (SRB) became abundant in the rhizosphere. We suggest that these phylotypes could be potentially methylating bacteria and might be responsible for the higher MMHg percentage of the total Hg in rhizosphere sediments. However, SRB were not significantly favoured in rhizosphere sediments as shown by qPCR. Our findings support the hypothesis that rooted macrophytes created a microenvironment favorable for Hg methylation. The presence of E. nuttallii in Hg contaminated sediments should therefore not be overlooked.

  5. Organizational Structures to Support Oakland Community Schools. Knowledge Brief

    Science.gov (United States)

    John W. Gardner Center for Youth and Their Communities, 2015

    2015-01-01

    This brief is part of a series that shares findings from a research collaboration between the John W. Gardner Center for Youth and Their Communities at Stanford University and Oakland Unified School District (OUSD) focused on understanding implementation of the community school model in the district. This brief highlights findings related to…

  6. Supraglacial bacterial community structures vary across the Greenland ice sheet

    DEFF Research Database (Denmark)

    Cameron, Karen A.; Stibal, Marek; Zarsky, Jakub D.;

    2016-01-01

    The composition and spatial variability of microbial communities that reside within the extensive (>200 000 km(2)) biologically active area encompassing the Greenland ice sheet (GrIS) is hypothesized to be variable. We examined bacterial communities from cryoconite debris and surface ice across...

  7. A MODIS-Based Novel Method to Distinguish Surface Cyanobacterial Scums and Aquatic Macrophytes in Lake Taihu

    National Research Council Canada - National Science Library

    Liang, Qichun; Zhang, Yuchao; Ma, Ronghua; Loiselle, Steven; Li, Jing; Hu, Minqi

    2017-01-01

      Satellite remote sensing can be an effective alternative for mapping cyanobacterial scums and aquatic macrophyte distribution over large areas compared with traditional ship's site-specific samplings...

  8. Discovery of Opinion Leader Community Via Multilayer Structure based Time-dividing Approach

    Directory of Open Access Journals (Sweden)

    Yan Liu

    2013-07-01

    Full Text Available With the advent of web 3.0, social network has become an important way to disclosure and spread the public sentiment. Opinion leaders play an important role in leading the direction of the public opinion. In this paper, due to the structure of the community in the network, we extracted the community by replies of each post in BBS, and we came up with an opinion leader community mining method based on level structure. In this way the communities each other have a better overlap result. Thus, communities can have more relations. Then, we analyzed the revolution of the communities after we got the structure of the opinion leader communities and we put forward a time-dividing method, and divided the whole communities into different pieces based on the character of the post and the duration of the time and we came up with the suitable measurement parameter to get the evolution result of the communities. Finally, experiments prove the efficiency of the opinion leader community mining method and we summarize the properties of the opinion leader community in revolution.

  9. Spatial and temporal dynamics of macrophyte cover in a large regulated river.

    Science.gov (United States)

    Tena, A; Vericat, D; Gonzalo, L E; Batalla, R J

    2016-11-24

    The River Ebro basin is extensively dammed. Dams alter the geomorphological functioning of the river by altering its flow regime (e.g. reducing mean and maximum discharges), increasing bed stability (armouring) and decreasing turbidity (water clarity). These effects, together with an increase in nutrient concentrations and water temperature, have generated optimal conditions for the proliferation of aquatic macrophytes. In this paper, we analyse the temporal and spatial changes of macrophyte cover in the lowermost Ebro through a series of field campaigns carried out between 2009 and 2010. Special attention was paid to the spatial distribution of macrophytes in relation to flow hydraulics, channel geometry and bed sedimentology. Temporal changes in macrophyte cover were analysed in relation to the frequency and magnitude of both natural floods and flushing flows (artificial flow releases from dams with generally a magnitude that equates around a2-year flood in the river). Spatially, the proportion of macrophytes along the reaches showed a variable pattern, with a succession of areas with both high and low plant density, coinciding with the alternation of riffles and pools in the channel. The highest values of plant cover (>65%) occurred in riffles and in transition to riffle areas, while the lowest densities (1% or almost negligible) were observed in pools and transition to pool areas. Water depth and the grain-size distribution of the riverbed materials (i.e. D84), are found to be the main factors controlling the degree of plant cover in the lower Ebro. Temporally, the macrophyte proportion varied during the hydrological year, with a clear increment from late spring to early autumn (i.e. vegetation cover reached 40%, on average, of the channel surface). Macrophyte coverage decreases immediately following a flushing flow but in the long term, vegetation re-occupied the area again, even slightly increasing in some sections; overall, the mean percentage of macrophyte

  10. Plant genetics predicts intra-annual variation in phytochemistry and arthropod community structure.

    Science.gov (United States)

    Wimp, G M; Wooley, S; Bangert, R K; Young, W P; Martinsen, G D; Keim, P; Rehill, B; Lindroth, R L; Whitham, T G

    2007-12-01

    With the emerging field of community genetics, it is important to quantify the key mechanisms that link genetics and community structure. We studied cottonwoods in common gardens and in natural stands and examined the potential for plant chemistry to be a primary mechanism linking plant genetics and arthropod communities. If plant chemistry drives the relationship between plant genetics and arthropod community structure, then several predictions followed. We would find (i) the strongest correlation between plant genetic composition and chemical composition; (ii) an intermediate correlation between plant chemical composition and arthropod community composition; and (iii) the weakest relationship between plant genetic composition and arthropod community composition. Our results supported our first prediction: plant genetics and chemistry had the strongest correlation in the common garden and the wild. Our results largely supported our second prediction, but varied across space, seasonally, and according to arthropod feeding group. Plant chemistry played a larger role in structuring common garden arthropod communities relative to wild communities, free-living arthropods relative to leaf and stem modifiers, and early-season relative to late-season arthropods. Our results did not support our last prediction, as host plant genetics was at least as tightly linked to arthropod community structure as plant chemistry, if not more so. Our results demonstrate the consistency of the relationship between plant genetics and biodiversity. Additionally, plant chemistry can be an important mechanism by which plant genetics affects arthropod community composition, but other genetic-based factors are likely involved that remain to be measured.

  11. Supraglacial bacterial community structures vary across the Greenland ice sheet.

    Science.gov (United States)

    Cameron, Karen A; Stibal, Marek; Zarsky, Jakub D; Gözdereliler, Erkin; Schostag, Morten; Jacobsen, Carsten S

    2016-02-01

    The composition and spatial variability of microbial communities that reside within the extensive (>200 000 km(2)) biologically active area encompassing the Greenland ice sheet (GrIS) is hypothesized to be variable. We examined bacterial communities from cryoconite debris and surface ice across the GrIS, using sequence analysis and quantitative PCR of 16S rRNA genes from co-extracted DNA and RNA. Communities were found to differ across the ice sheet, with 82.8% of the total calculated variation attributed to spatial distribution on a scale of tens of kilometers separation. Amplicons related to Sphingobacteriaceae, Pseudanabaenaceae and WPS-2 accounted for the greatest portion of calculated dissimilarities. The bacterial communities of ice and cryoconite were moderately similar (global R = 0.360, P = 0.002) and the sampled surface type (ice versus cryoconite) did not contribute heavily towards community dissimilarities (2.3% of total variability calculated). The majority of dissimilarities found between cryoconite 16S rRNA gene amplicons from DNA and RNA was calculated to be the result of changes in three taxa, Pseudanabaenaceae, Sphingobacteriaceae and WPS-2, which together contributed towards 80.8 ± 12.6% of dissimilarities between samples. Bacterial communities across the GrIS are spatially variable active communities that are likely influenced by localized biological inputs and physicochemical conditions.

  12. 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

    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......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...

  13. The Organization and Structure of Community Education Offerings in Community Colleges

    Science.gov (United States)

    Miller, Michael; Grover, Kenda S.; Kacirek, Kit

    2014-01-01

    One of the key services community colleges provide is community education, meaning those programs and activities that are often offered for leisure or self-improvement and not for credit. Programs of this nature are increasingly challenged to be self-financing, whether through user fees or externally funded grants. The current study explored 75…

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

    Directory of Open Access Journals (Sweden)

    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.

  15. Assembly and phylogenetic structure of Neotropical palm communities

    DEFF Research Database (Denmark)

    Eiserhardt, Wolf L.; Svenning, J.-C.; Balslev, Henrik

    Diversity, composition and dynamics of Neotropical palm communities are receiving an increasing amount of attention due to their economic importance, but also because their high species richness and functional diversity render them valuable model systems for overall forest biodiversity. However...

  16. Reef community structure, Sand Island, Oahu HI, (NODC Accession 0000177)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These reports provide the results of nine years (1990-98) of an annual quantitative monitoring of shallow marine communities inshore of the Sand Island Ocean...

  17. Macrofouling community structure in Kanayama Bay, Kii Peninsula (Japan)

    Digital Repository Service at National Institute of Oceanography (India)

    Raveendran, T.V.; Harada, E.

    An investigation on the macrofouling community in Kanayama Bay, Kill Peninsula, Japan was undertaken from June 1994 to May 1995 by exposing fiber reinforced plastic (FRP) panels at subsurface and bottom (2.2 m) depths. The composition and abundance...

  18. What makes us a community: structure, correlations, and success in scientific world

    CERN Document Server

    Kalinin, Sergei V

    2015-01-01

    We explore the statistical structure of scientific community based on multivariate analysis of publication (or other identifiable metrics) distribution in the author space. Here, we define community based on keywords, i.e. projecting semantic content of the documents on predefined meanings; however, more complex approaches based on semantic clustering of publications are possible. Remarkably, this simple statistical analysis of publication metadata allows understanding of internal interactions with community in general agreement with experience acquired over decades of social interaction within it. We further discuss potential applications of this approach for ranking within the community, reviewer selection, and optimization of community output.

  19. Progressive recovery of a tropical deforested stream community after a flash flood

    Directory of Open Access Journals (Sweden)

    Lucas Cerqueira Marques

    2013-06-01

    Full Text Available AIM: In this study, we evaluated and compared community attributes from a tropical deforested stream, located in a pasture area, in a period before (PRED I and three times after (POSD I, II, and III a flash flood, in order to investigate the existence of temporal modifications in community structure that suggests return to conditions previous to the flash flood. METHODS: Biota samples included algae, macrophytes, macroinvertebrates, and fish assemblages. Changes in stream physical structure we also evaluated. Similarity of the aquatic biota between pre and post-disturbance periods was examined by exploratory ordination, known as Non-Metric Multidimensional Scaling associated with Cluster Analysis, using quantitative and presence/absence Bray-Curtis similarity coefficients. Presence and absence data were used for multivariate correlation analysis (Relate Analysis in order to investigate taxonomic composition similarity of biota between pre and post-disturbance periods. RESULTS: Our results evidenced channel simplification and an expressive decrease in richness and abundance of all taxa right after the flood, followed by subsequent increases of these parameters in the next three samples, indicating trends towards stream community recovery. Bray-Curtis similarity coefficients evidenced a greater community structure disparity among the period right after the flood and the subsequent ones. Multivariate correlation analysis evidenced a greater correlation between macroinvertebrates and algae/macrophytes, demonstrating the narrow relation between their recolonization dynamics. CONCLUSIONS: Despite overall community structure tended to return to previous conditions, recolonization after the flood was much slower than that reported in literature. Finally, the remarkably high flood impact along with the slow recolonization could be a result of the historical presence of anthropic impacts in the region, such as siltation, riparian forest complete depletion

  20. Temporal trends and effects of diversity on occurrence of exotic macrophytes in a large reservoir

    Science.gov (United States)

    Thomaz, Sidinei Magela; Carvalho, Priscilla; Mormul, Roger Paulo; Ferreira, Fernando Alves; Silveira, Márcio José; Michelan, Thaísa Sala

    2009-09-01

    Two exotic invasive macrophyte species (the emergent Urochloa subquadripara - tenner-grass - and the submersed Hydrilla verticillata - hydrilla) were investigated in a large sub-tropical reservoir. We analyzed their occurrences over an extended period and tested the hypothesis that macrophyte richness decreases their invasibility. The alternative hypothesis that the occurrence of these exotics is affected by fetch and underwater radiation (important determinants of macrophyte assemblage composition in this reservoir) was also tested. Incidence data (presence/absence) was obtained over 9.5 years at 235 stations. Logistic regression was applied to test whether the likelihood of occurrence of these two species was affected by macrophyte richness, fetch or underwater radiation. Tenner-grass was recorded at a high frequency and quickly recovered from disturbances caused by water drawdown. In contrast, H. verticillata was first recorded in 3 sites in January 2007, but it spread quickly, reaching 30.5% of the sites 19 months later. The main channel of the Paraná River was the main source of propagules for this species. The likelihood of occurrence of tenner-grass was positively affected by macrophyte richness but negatively affected by fetch. Thus, wave disturbance is probably more important than diversity in preventing invasion by this species. Hydrilla, by contrast, was negatively affected by macrophyte richness and positively affected by fetch and underwater radiation. Although this result might indicate that macrophyte diversity prevents hydrilla invasion, this is probably not true because hydrilla colonized deeper sites where few species of plant exist. Resistance to disturbances caused by water drawdown (tenner-grass) and waves (hydrilla) as well as persistency of tenner-grass and fast spread of hydrilla make these exotic species a cause for concern because of their potential impacts on water uses and maintenance of diversity.

  1. Monitoring the effects of floods on submerged macrophytes in a large river.

    Science.gov (United States)

    Ibáñez, Carles; Caiola, Nuno; Rovira, Albert; Real, Montserrat

    2012-12-01

    The lower Ebro River (Catalonia, Spain) has recently undergone a regime shift from a phytoplankton to a macrophyte-dominated system. Macrophytes started to spread at the end of the 1990s and since 2002 artificial floods (flushing flows) of short duration (1-2 days) are released from the Riba-roja dam once or twice a year in order to reduce macrophyte density. The aim of this study was to analyse the spatiotemporal trends of the submerged macrophytes in two stretches of the lower Ebro River using high-resolution hydroacoustic methods, in order to elucidate the effects of artificial floods and natural floods on its distribution and abundance. Results showed that the mean cover in the two studied stretches (Móra and Ginestar) was not reduced after a flushing flow (from 36.59% to 55.85% in Móra, and from 21.18% to 21.05% in Ginestar), but it was greatly reduced after the natural flood (down to 9.79% in Móra and 2.04% in Ginestar); surprisingly the cover increased in Móra after the artificial flood. In order to increase the efficiency of floods in controlling macrophyte spreading, the magnitude and frequency of them should largely increase, as well as the suspended sediment load, approaching as much as possible to the original flood pattern before dam construction. Hydroacoustic methods combined with geostatistics and interpolation in GIS can accurately monitor spatiotemporal trends of submerged macrophytes in large rivers. This is the first article to apply this monitoring system to submerged macrophytes in rivers. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. Structure and function of fish communities in the southern Lake Michigan basin with emphasis on restoration of native fish communities

    Science.gov (United States)

    Simon, Thomas P.; Stewart, Paul M.

    1999-01-01

    The southern Lake Michigan basin in northwest Indiana possesses a variety of aquatic habitats including riverine, palustrine, and lacustrine systems. The watershed draining this area is a remnant of glacial Lake Chicago and supports fish communities that are typically low in species richness. Composition of the presettlement Lake Michigan fish community near the Indiana Dunes has been difficult to reconstruct. Existing data indicate that the number of native species in the Lake Michigan watershed, including nearshore Lake Michigan, has declined by 22% since the onset of European settlement. Few remnants of natural fish communities exist, and those occur principally in the ponds of Miller Woods, the Grand Calumet Lagoons, and the Little Calumet River. These communities have maintained a relatively diverse assemblage of fishes despite large-scale anthropogenic disturbances in the area, including channelization, massive river redirection, fragmentation, habitat alteration, exotic species invasions, and the introduction of toxic chemicals. Data that we collected from 1985 to 1996 suggested that the Grand Calumet River has the highest proportion of exotic fish species of any inland wetland in northwest Indiana. Along the Lake Michigan shoreline, another group of exotics (e.g., round goby, alewife, and sea lamprey) have affected the structure of native fish communities, thereby altering lake ecosystem function. Stocking programs contribute to the impairment of native communities. Nonindigenous species have restructured the function of Lake Michigan tributaries, causing disruptions in trophic dynamics, guild structure, and species diversity. Several fish communities have been reduced or eliminated by the alteration and destruction of spawning and nursery areas. Degradation of habitats has caused an increase in numbers and populations of species able to tolerate and flourish when confronted with hydrologic alteration. Fish communities found on public lands in northwest

  3. 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.

  4. Microbes as Engines of Ecosystem Function: When Does Community Structure Enhance Predictions of Ecosystem Processes?

    Science.gov (United States)

    Graham, Emily B; Knelman, Joseph E; Schindlbacher, Andreas; Siciliano, Steven; Breulmann, Marc; Yannarell, Anthony; Beman, J M; Abell, Guy; Philippot, Laurent; Prosser, James; Foulquier, Arnaud; Yuste, Jorge C; Glanville, Helen C; Jones, Davey L; Angel, Roey; Salminen, Janne; Newton, Ryan J; Bürgmann, Helmut; Ingram, Lachlan J; Hamer, Ute; Siljanen, Henri M P; Peltoniemi, Krista; Potthast, Karin; Bañeras, Lluís; Hartmann, Martin; Banerjee, Samiran; Yu, Ri-Qing; Nogaro, Geraldine; Richter, Andreas; Koranda, Marianne; Castle, Sarah C; Goberna, Marta; Song, Bongkeun; Chatterjee, Amitava; Nunes, Olga C; Lopes, Ana R; Cao, Yiping; Kaisermann, Aurore; Hallin, Sara; Strickland, Michael S; Garcia-Pausas, Jordi; Barba, Josep; Kang, Hojeong; Isobe, Kazuo; Papaspyrou, Sokratis; Pastorelli, Roberta; Lagomarsino, Alessandra; Lindström, Eva S; Basiliko, Nathan; Nemergut, Diana R

    2016-01-01

    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.

  5. The structure of small mammal communities in some alpine habitats

    Directory of Open Access Journals (Sweden)

    Roberta Locatelli

    1998-12-01

    Full Text Available Abstract We studied the composition of several small mammal communities living in different mountain and forest habitats of the central eastern Italian Alps. The small mammals were then grouped together, by cluster analysis, according to similarities in species and density. From the 22 stations investigated, five groups emerged, each one having also distinct environmental characteristics. We observed that spruce forest communities are grouped separately from those of mixed forests (larch and Swiss stone pine. We must stress the considerable difference existing between the small mammal communities living in different kinds of coniferous forests. The larch and Swiss stone pine forest seem to be able to support a greater density of small mammals, which includes in particular the bank vole (Clethrionomys glareolus.

  6. Habitat modification by the stream macrophyte Justicia americana and its effects on biota.

    Science.gov (United States)

    Fritz, Ken M; Gangloff, Michael M; Feminella, Jack W

    2004-08-01

    We conducted an in-stream experiment to determine if and by what mechanisms the emergent macrophyte, Justicia americiana, enhances streambed stability and influences associated benthic organisms. Treatments included removal of aboveground stems, removal of stems and rhizomes, and a control. Stone stability and embeddedness were higher within intact patches of Justicia compared with areas where stems and rhizomes were removed. Presence of belowground structures binding stones and higher embeddedness were responsible for differences in stone stability among treatments. Sediment deposition was highly variable among treatments; however, silt and clay deposition was highest in the control when Justicia stems reached maximum biomass. Response of neighboring benthic organisms to Justicia treatments varied with organism mobility and trophic level. Sedentary unionid mussels were more abundant in the control than in the stem and rhizome-removal treatment, whereas abundance of mobile snails (Elimia ucheensis) and sessile plants (Podostemon ceratophyllum and mosses) did not differ among treatments. Justicia appears to modify the stream environment by: (1) increasing stability of streambed sediments, and (2) reducing current velocity, thereby enhancing deposition of fine sediments and organic matter.

  7. Microarthropod community structures (Oribatei and Collembola) in Tam Dao National Park, Vietnam

    Indian Academy of Sciences (India)

    Quang Manh Vu; Tri Tien Nguyen

    2000-12-01

    A study on the microarthropod community with special reference to species diversity of Oribatid and Collembola communities (Microarthropoda: Oribatei and Collembola) in Tam Dao National Park of Vietnam, a subtropical evergreen broad leaf alpine forest, was undertaken with the aim to explain how they are related to forest decline, and whether they can be used as bioindicators of forest plant succession. The results have shown that microarthropod community structures, particularly species diversity of oribatid and collembolan communities, are related to forest decline. Therefore they can be used as bioindicators of forest plant succession. In Tam Dao National Park, there was an inverse relation between species diversity of the oribatid and collembola communities. The species diversity of the oribatid community gradually decreased with forest decline whereas the species diversity of the collembola community gradually increased.

  8. The Structure and Distribution of Benthic Communities on a Shallow Seamount (Cobb Seamount, Northeast Pacific Ocean)

    Science.gov (United States)

    Curtis, Janelle M. R.; Clarke, M. Elizabeth

    2016-01-01

    Partially owing to their isolation and remote distribution, research on seamounts is still in its infancy, with few comprehensive datasets and empirical evidence supporting or refuting prevailing ecological paradigms. As anthropogenic activity in the high seas increases, so does the need for better understanding of seamount ecosystems and factors that influence the distribution of sensitive benthic communities. This study used quantitative community analyses to detail the structure, diversity, and distribution of benthic mega-epifauna communities on Cobb Seamount, a shallow seamount in the Northeast Pacific Ocean. Underwater vehicles were used to visually survey the benthos and seafloor in ~1600 images (~5 m2 in size) between 34 and 1154 m depth. The analyses of 74 taxa from 11 phyla resulted in the identification of nine communities. Each community was typified by taxa considered to provide biological structure and/or be a primary producer. The majority of the community-defining taxa were either cold-water corals, sponges, or algae. Communities were generally distributed as bands encircling the seamount, and depth was consistently shown to be the strongest environmental proxy of the community-structuring processes. The remaining variability in community structure was partially explained by substrate type, rugosity, and slope. The study used environmental metrics, derived from ship-based multibeam bathymetry, to model the distribution of communities on the seamount. This model was successfully applied to map the distribution of communities on a 220 km2 region of Cobb Seamount. The results of the study support the paradigms that seamounts are diversity 'hotspots', that the majority of seamount communities are at risk to disturbance from bottom fishing, and that seamounts are refugia for biota, while refuting the idea that seamounts have high endemism. PMID:27792782

  9. Geochip: A high throughput genomic tool for linking community structure to functions

    Energy Technology Data Exchange (ETDEWEB)

    Van Nostrand, Joy D.; Liang, Yuting; He, Zhili; Li, Guanghe; Zhou, Jizhong

    2009-01-30

    GeoChip is a comprehensive functional gene array that targets key functional genes involved in the geochemical cycling of N, C, and P, sulfate reduction, metal resistance and reduction, and contaminant degradation. Studies have shown the GeoChip to be a sensitive, specific, and high-throughput tool for microbial community analysis that has the power to link geochemical processes with microbial community structure. However, several challenges remain regarding the development and applications of microarrays for microbial community analysis.

  10. Impacts of aquatic macrophytes configuration modes on water quality.

    Science.gov (United States)

    Liu, Jiakai; Liu, Jinglan; Zhang, Rong; Zou, Yuqi; Wang, Huihui; Zhang, Zhenming

    2014-01-01

    Constructed wetland technology is regarded as an important ecological restoration technology and used widely in sewage disposal. In order to give them a wider scope of application and to improve their performance in water restoration, the current experiment was designed. Four aquatic macrophytes (dwarf cattail (TM), yellow-flowered iris (WI), water shallot (ST) and watermifoil (MS)) were picked and planted in artificial floating islands (AFIs) in different configurations (TM + WI, ST + MS and TM + WI + MS) and two patterns, radiation pattern (RP) and annular pattern (AP), for a 60-day experiment. Then, water quality and growth were monitored every 10 days. The results indicate that the different configurations performed diversely on waste water purification. First, a composite plant configuration removed more pollutant than a single one with the same total increment of biomass. Second, the plant configuration of MS + ST was most effective in total nitrogen (TN), total phosphorus (TP) or PO4(3-) removal, and TM + IW + MS was good at chemical oxygen demand (COD) and NO3(-) removal. However, different patterns comprised from the same species had a certain effect on absorption of pollutants. Generally speaking, plant configurations with a RP were better than an AP in purification. Accordingly, these provided the methods for the pollution wetland restoration.

  11. Relative importance of abiotic, biotic, and disturbance drivers of plant community structure in the sagebrush steppe.

    Science.gov (United States)

    Mitchell, Rachel M; Bakker, Jonathan D; Vincent, John B; Davies, G Matt

    2017-04-01

    Abiotic conditions, biotic factors, and disturbances can act as filters that control community structure and composition. Understanding the relative importance of these drivers would allow us to understand and predict the causes and consequences of changes in community structure. We used long-term data (1989-2002) from the sagebrush steppe in the state of Washington, USA, to ask three questions: (1) What are the key drivers of community-level metrics of community structure? (2) Do community-level metrics and functional groups differ in magnitude or direction of response to drivers of community structure? (3) What is the relative importance of drivers of community structure? The vegetation in 2002 was expressed as seven response variables: three community-level metrics (species richness, total cover, compositional change from 1989 to 2002) and the relative abundances of four functional groups. We used a multi-model inference framework to identify a set of top models for each response metric beginning from a global model that included two abiotic drivers, six disturbances, a biotic driver (initial plant community), and interactions between the disturbance and biotic drivers. We also used a permutational relative variable importance metric to rank the influence of drivers. Moisture availability was the most important driver of species richness and of native forb cover. Fire was the most important driver of shrub cover and training area usage was important for compositional change, but disturbances, including grazing, were of secondary importance for most other variables. Biotic drivers, as represented by the initial plant communities, were the most important driver for total cover and for the relative covers of exotics and native grasses. Our results indicate that the relative importance of drivers is dependent on the choice of metric, and that drivers such as disturbance and initial plant community can interact. © 2016 by the Ecological Society of America.

  12. Determination of Algae and Macrophyte Species Distribution in Three Wastewater Stabilization Ponds Using Metagenomics Analysis

    Directory of Open Access Journals (Sweden)

    Jack Wallace

    2015-06-01

    Full Text Available This study involved the evaluation of algae and macrophyte species distributions in three wastewater stabilization ponds (WSPs at a wastewater treatment plant in Ontario, Canada, which has experienced high pH levels at the final effluent and excessive algae growth during the summer since 2003. From samples collected from the system, the relative abundances of specific algae and aquatic plant (macrophyte taxa were assessed and correlated to water chemistry data. A strong shift from the dominance of green algae, chlorophyceae, in WSP#2, to the dominance of aquatic macrophytes, embryophyta, in WSP#4, was observed and corresponded to field observations. Correlation of the abundances to nutrient parameters suggested that the macronutrient rich conditions in WSP#2 allowed floating green algae to proliferate against macrophytes. In WSP#1 and WSP#4, macrophytes competed against algae and thrived, due to their adaptability to lower nutrient conditions. The pH increases occurred primarily in WSP#2 and were not buffered or reduced in WSP#1 and WSP#4. Two alternatives strategies for pH control were recommended for the system: decreasing algae growth in WSP#2 through duckweed seeding or macronutrient loading reduction; or designing and implementing a constructed wetland (CW in WSP#4 with soil and vegetation to buffer pH prior to release.

  13. Towards Deriving Renewable Energy from Aquatic Macrophytes Polluting Water Bodies in Niger Delta Region of Nigeria

    Directory of Open Access Journals (Sweden)

    Badmus Abdurrahman Adeleye

    2013-01-01

    Full Text Available This study was performed to derive methane rich biogas from biomass of harvested water hyacinth polluting water bodies in selected rivers of the Niger delta region of Nigeria. Field visits were undertaken on selected rivers in the Niger Delta region in which aquatic macrophytes were collected and inventorized. Also different types of aquatic macrophytes were surveyed. Control by harvesting macrophytes and deriving energy (methane-rich biogas from biomass of one (water hyacinth was successfully carried out in this study. An initial test was conducted to evaluate methane rich biogas production from water hyacinth collected from the wild. After a successful production of combustible biogas, laboratory experiments aimed at generating biogas from harvested biomass of aquatic mycrophyte (water hyacinth cultivated under eutrophic and oligotrophic conditions were undertaken in the laboratory. The result of the study showed highest biogas yield of 22 L over a 40 day retention time for water hyacinth raised under eutrophic conditions. Biogas yield for water hyacinth raised under oligotrophic conditions recorded the highest yield of 53L over an 11 day retention time. The conversion of the biomass of harvested aquatic macrophyte (water hyacinth from the Niger Delta into renewable energy, that is combustible biogas, demonstrated an inevitable option for the control and management of environmental pollution associated with aquatic macrophytes and their usability for poverty alleviation in the Niger Delta region of Nigeria.

  14. Management of fresh water weeds (macrophytes) by vermicomposting using Eisenia fetida.

    Science.gov (United States)

    Najar, Ishtiyaq Ahmed; Khan, Anisa B

    2013-09-01

    In the present study, potential of Eisenia fetida to recycle the different types of fresh water weeds (macrophytes) used as substrate in different reactors (Azolla pinnata reactor, Trapa natans reactor, Ceratophyllum demersum reactor, free-floating macrophytes mixture reactor, and submerged macrophytes mixture reactor) during 2 months experiment is investigated. E. fetida showed significant variation in number and weight among the reactors and during the different fortnights (P weeds) into three clusters-poor vermicompost substrates, moderate vermicompost substrate, and excellent vermicompost substrate. Two principal components (PCs) have been identified by factor analysis with a cumulative variance of 90.43 %. PC1 accounts for 47.17 % of the total variance represents "reproduction factor" and PC2 explaining 43.26 % variance representing "growth factor." Thus, the nature of macrophyte affects the growth and reproduction pattern of E. fetida among the different reactors, further the addition of A. pinnata in other macrophytes reactors can improve their recycling by E. fetida.

  15. Microbial community structure in three deep-sea carbonate crusts

    NARCIS (Netherlands)

    Heijs, S. K.; Aloisi, G.; Bouloubassi, I.; Pancost, R. D.; Pierre, C.; Damste, J. S. Sinninghe; Gottschal, J. C.; van Elsas, J. D.; Forney, L. J.

    2006-01-01

    Carbonate crusts in marine environments can act as sinks for carbon dioxide. Therefore, understanding carbonate crust formation could be important for understanding global warming. In the present study, the microbial communities of three carbonate crust samples from deep-sea mud volcanoes in the eas

  16. Characterization and exploitation of community structure in cover song networks

    CERN Document Server

    Serrà, Joan; Herrera, Perfecto; Serra, Xavier

    2011-01-01

    The use of community detection algorithms is explored within the framework of cover song identification, i.e. the automatic detection of different audio renditions of the same underlying musical piece. Until now, this task has been posed as a typical query-by-example task, where one submits a query song and the system retrieves a list of possible matches ranked by their similarity to the query. In this work, we propose a new approach which uses song communities to provide more relevant answers to a given query. Starting from the output of a state-of-the-art system, songs are embedded in a complex weighted network whose links represent similarity (related musical content). Communities inside the network are then recognized as groups of covers and this information is used to enhance the results of the system. In particular, we show that this approach increases both the coherence and the accuracy of the system. Furthermore, we provide insight into the internal organization of individual cover song communities, s...

  17. Post fumigation recovery of soil microbial community structure

    Science.gov (United States)

    Soil fumigants have been extensively used to control target soil-borne pathogens and weeds for the past few decades. It is known that the fumigants with broad biocidal activity can affect both target and non-target soil organisms, but the recovery of soil microbial communities are unknown until rece...

  18. Microbial activity and community structure in two drained fen soils in the Ljubljana Marsh

    NARCIS (Netherlands)

    Kraigher, Barbara; Stres, Blaz; Hacin, Janez; Ausec, Luka; Mahne, Ivan; van Elsas, Jan D.; Mandic-Mulec, Ines

    2006-01-01

    Fen peatlands are specific wetland ecosystems containing high soil organic carbon (SOC). There is a general lack of knowledge about the microbial communities that abound in these systems. We examined the microbial activity and community structure in two fen soils differing in SOC content sampled fro

  19. Relationship between microbial activity and microbial community structure in six full-scale anaerobic digesters

    NARCIS (Netherlands)

    Regueiro, L.; Veiga, P.; Figueroa, M.; Alonso-Gutierrez, J.; Stams, A.J.M.; Lema, J.M.; Carballa, M.

    2012-01-01

    High activity levels and balanced anaerobic microbial communities are necessary to attain proper anaerobic digestion performance. Therefore, this work was focused on the kinetic performance and the microbial community structure of six full-scale anaerobic digesters and one lab-scale co-digester. Hyd

  20. Teaching Interpersonal Skills to Psychiatric Outpatients: Using Structured Learning Therapy in a Community-Based Setting

    Science.gov (United States)

    Sprafkin, Robert P.; And Others

    1978-01-01

    The Structured Learning Therapy (SLT), a type of treatment used to assist psychiatric patients to learn skills they need for effective and satisfying living in the community, is described in this article. A description of the community-based treatment facility in which SLT may be utilized and the results of the evaluation studies are also…

  1. Microbial Community Structure and Enzyme Activities in a Sequence of Copper-Polluted Soils

    Institute of Scientific and Technical Information of China (English)

    GE Chao-Rong; ZHANG Qi-Chun

    2011-01-01

    The microbial community structure and enzyme activities of seven paddy soils with different Cu concentrations were investigated in the vicinity of a Cu smelter in Fuyang County, Zhejiang Province in Southeast China. The microbial community structure was analyzed using the phospholipid fatty acid (PLFA) and multiplex-terminal restriction fragment length polymorphism (M-TRFLP)techniques. There was no clear dose-response relationship between Cu pollution and soil enzyme activity except for urease. Both PLFA and M-TRFLP methods showed that Cu contamination had a large effect on the soil microbial community structure. PLFA indicators of Gram-positive bacteria (16:0i, 15:0i) and fungi (18:2w6,9) relatively decreased with increasing Cu concentration, whereas indicators of Gram-negative bacteria (19:0cy, 16:1w7) increased. The M-TRFLP results suggested that there was a dose-dependent response between Cu pollution and bacterial community or fungal community. The fungal community was more sensitive to Cu pollution than the bacterial community. Therewere no significant differences in archaeal community structure between the different Cu pollution plots and archaea might be more tolerant to Cu pollution than both bacteria and fungi.

  2. Impacts of Information Subsidies and Community Structure on Local Press Coverage of Environmental Contamination.

    Science.gov (United States)

    Griffin, Robert J.; Dunwoody, Sharon

    1995-01-01

    Finds that a press kit sent by an environmental group to midwestern newspapers influenced them to delegate local staff to cover the story. Indicates that the press's function to report or raise issues concerning industrial toxic releases and related health risks is tempered by community structure and particularly by community reliance on…

  3. How TK-TD and population models for aquatic macrophytes could support the risk assessment for plant protection products

    NARCIS (Netherlands)

    Hommen, U.; Schmitt, W.; Heine, S.; Brock, T.C.M.; Duquesne, S.; Manson, P.; Meregali, G.; Ochoa-Acuna, H.; Vliet, van P.; Arts, G.H.P.

    2016-01-01

    This case study of the SETAC workshop MODELINK demonstrates the potential use of mechanistic effects models for macrophytes to extrapolate from effects of a plant protection product observed in laboratory tests to effects resulting from dynamic exposure on macrophyte populations in edge-of-field wat

  4. Bimodality in stable isotope composition facilitates the tracing of carbon transfer from macrophytes to higher trophic levels

    NARCIS (Netherlands)

    Mendonca, R.; Kosten, S.; Lacerot, G.; Mazzeo, N.; Roland, F.; Ometto, J.P.; Paz, A.; Bueno, O.C.; Gomes, A.C.M.M.; Scheffer, M.

    2013-01-01

    Even though the suitability of macrophytes to act as a carbon source to food webs has been questioned by some studies, some others indicate that macrophyte-derived carbon may play an important role in the trophic transfer of organic matter in the food web of shallow lakes. To evaluate the importance

  5. Effects of transient temperature conditions on the divergence of activated sludge bacterial community structure and function.

    Science.gov (United States)

    Nadarajah, Nalina; Allen, D Grant; Fulthorpe, Roberta R

    2007-06-01

    The effect of temperature fluctuations on bacterial community structure and function in lab-scale sequencing batch reactors treating bleached kraft mill effluent was investigated. An increase in temperature from 30 to 45 degrees C caused shifts in both bacterial community structure and function. Triplicate reactors were highly similar for 40 days following startup. After the temperature shift, their community structure and function started to diverge from each other and from the control. A multi-response permutation procedure confirmed that the variability in community structure between transient and control reactors were greater than that among the triplicate transient reactors. The fact that these disturbances manifest themselves in different ways in apparently identical reactors suggests a high degree of variability between replicate systems.

  6. Population Age Structures of Tree Species in Four Plant Communities in the Great Dismal Swamp, Virginia

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The primary objective of the present study was to determine the age structures of species occurring in four plant communities in the Great Dismal Swamp, Virginia, by...

  7. The effect of bacteria on diatom community structure - The 'antibiotics' approach

    Digital Repository Service at National Institute of Oceanography (India)

    DeCosta, P.M.; Anil, A.C.

    aminoglycoside) and chloramphenicol, antibiotics that can potentially affect protein synthesis in diatom organelles and photosynthesis, were also used for comparison. The changes in diatom community structure and the resistant and tolerant bacterial fractions...

  8. Subtidal micro and meiobenthic community structure in the Gulf of Kachchh

    Digital Repository Service at National Institute of Oceanography (India)

    Ingole, B.S.; Goltekar, R.

    Community structure of the micro- and meiobenthos of subtidal sediment from the Gulf of Kachchh were investigated during April 2002 (premonsoon season). Sediment samples were collected from 23 stations representing the entire Gulf area. A total...

  9. Organizational Structures and Perceived Cultures of Community-Charter School in Ohio.

    Science.gov (United States)

    Fox, Jeannie L.

    2002-01-01

    Challenges the assumption that bureaucracy is bad for charter schools. Examines perceived autonomy, governance structures, leadership, and perceived culture of community-charter schools in Ohio. (Contains 15 references.) (PKP)

  10. [Colonization and community structural features of AM fungi in urban ecosystem: a review].

    Science.gov (United States)

    Shi, Li-jun; Diao, Zhi-kai; Liu, Run-jin

    2011-07-01

    Arbuscular mycorrhizal (AM) fungi, an important component of soil microbes, are of significance in maintaining the sustainable development of urban ecosystem. This paper summarized the characteristics of the colonization and community structure of AM fungi in urban ecosystems, and discussed the effects of urban ecological factors, e.g., human activities, vegetation re-establishment and maintenance, and urban soil status, on the colonization and community structure. It was considered that the researches on the community structure and function of AM fungi in urban ecosystems, such as the effects and mechanisms of the key urban ecological factors (e.g., water resource shortage and heat island effect) on the alternation of AM fungal community structure should be strengthened in the future.

  11. The roles of biological interactions and pollutant contamination in shaping microbial benthic community structure

    OpenAIRE

    Louati, H.; Ben Said, O.; A. Soltani; Got, P; Mahmoudi, E.; Cravo-Laureau, C.; Duran, R.; Aissa, P.; Pringault, Olivier

    2013-01-01

    Biological interactions between metazoans and the microbial community play a major role in structuring food webs in aquatic sediments. Pollutants can also strongly affect the structure of meiofauna and microbial communities. This study aims investigating, in a non-contaminated sediment, the impact of meiofauna on bacteria facing contamination by a mixture of three PAHs (fluoranthene, phenanthrene and pyrene). Sediment microcosms were incubated in the presence or absence of meiofauna during 30...

  12. Community-analyzer: a platform for visualizing and comparing microbial community structure across microbiomes.

    Science.gov (United States)

    Kuntal, Bhusan K; Ghosh, Tarini Shankar; Mande, Sharmila S

    2013-10-01

    A key goal in comparative metagenomics is to identify microbial group(s) which are responsible for conferring specific characteristics to a given environment. These characteristics are the result of the inter-microbial interactions between the resident microbial groups. We present a new GUI-based comparative metagenomic analysis application called Community-Analyzer which implements a correlation-based graph layout algorithm that not only facilitates a quick visualization of the differences in the analyzed microbial communities (in terms of their taxonomic composition), but also provides insights into the inherent inter-microbial interactions occurring therein. Notably, this layout algorithm also enables grouping of the metagenomes based on the probable inter-microbial interaction patterns rather than simply comparing abundance values of various taxonomic groups. In addition, the tool implements several interactive GUI-based functionalities that enable users to perform standard comparative analyses across microbiomes. For academic and non-profit users, the Community-Analyzer is currently available for download from: http://metagenomics.atc.tcs.com/Community_Analyzer/.

  13. Structure and function of a benthic invertebrate stream community as influenced by beaver (Castor canadensis).

    Science.gov (United States)

    McDowell, Donald M; Naiman, Robert J

    1986-03-01

    Beaver (Castor canadensis) affect the benthic invertebrate community of small woodland streams in Quebec through habitat modifications. Their activities influence community structure through the replacement of lotic taxa by lentic forms and community function by increasing the absolute importance of collectors and predators while decreasing the relative importance of shredders and scrapers in impounded sites. At our study site during the 1983 ice-free season, standing stocks of coarse particulate organic matter (>1 mm) were 2-5 times greater (Podonates, Tubificidae, and filtering pelycopods. Our results suggest that current paradigms applied to lotic ecosystems need to be reevaluated to incorporate the influence of beaver upon invertebrate communities.

  14. Does the Lagoa do Peixe sandbar opening influence the macrophyte richness and composition in Southern Brazil wetlands?

    Directory of Open Access Journals (Sweden)

    Ana Silvia Rolon

    2013-03-01

    Full Text Available The Lagoa do Peixe has its connection with the sea artificially opened every year at the end of winter. However, this management has been carried out without the evaluation of the impact of this opening in the aquatic biodiversity. This information is crucial for the management of the natural resources of the Lagoa do Peixe National Park, the unique Ramsar site in Southern Brazil. The following questions were analyzed: (1 Do richness and composition of aquatic macrophytes from Lagoa do Peixe floodplain varies temporarily according to the sandbar opening and closing? (2 Does the variation pattern of the macrophyte community changed according to the sandbar opening and closing? A set of eight sampling sites of 1ha were selected over the Lagoa do Peixe floodplain: four sites not influenced by the artificial sandbar opening and four sites influenced by this event, being two sites closer to the sandbar opening and the two sites distant to the sandbar opening. The samplings were carried out between November 2007 and October 2009. The results show that although the artificial sandbar breaching does not affect the aquatic macrophyte richness at the floodplain, it affects the dynamics of species composition. The hydrological variation related to this management can be the main factor of the continuous change in the species composition in the floodplain, especially in the Southern portion. In order to avoid impacts in the macrophyte conservation, the artificial sandbar opening should be considered carefully, since the area of study is one of the most important conservation units to wetland systems in Southern Brazil.La Lagoa do Peixe, en el sur de Brasil, tiene conexión artificial con el mar, porque cada año, al final del invierno, se abre un canal con tractor. Sin embargo, esta práctica se ha levado a cabo sin la evaluación de los efectos de esta apertura en la biodiversidad acuática. Las siguientes preguntas fueron analizadas: (1 ¿Varían la

  15. Seasonal and temporal dynamics of macrophytic assemblages and abiotic parameters of coastal lagoons in Western Greece (Mediterranean Sea)

    Science.gov (United States)

    Christia, Chrysoula; Papastergiadou, Eva

    2014-05-01

    Coastal lagoons are considered naturally stressed systems that experience frequent environmental disturbances and fluctuations and they are usually considered as physically controlled ecosystems. Coastal lagoons of Western Greece are representative of four different lagoon types covering a wide range of physiographical and hydrological characteristics. The seasonal differences in the physico-chemical parameters monitored from 2005 to 2007 were reduced in lagoon types (II and III) which characterized by better seawater communication when compared with the chocked lagoon types (Type I and IV). The latter types showed lower salinity values and high nutrient concentrations especially during the wet period. The macrophytic assemblages of coastal lagoons are typically dominated by few genera with great environmental plasticity and salinity competition, among other structuring abiotic variables. The implementation of DCA analysis revealed five distinct macrophytic assemblages in which dominant species were the angiosperms Zostera noltii, Ruppia cirrhosa, Cymodocea nodosa, Potamogeton pectinatus, the charophytes Lamprothamnium papulosum and Chara hispida f. corfuensis, as well as species preferring more marine conditions such as Acanthophora nayadiformis and Cystoseira barbata. The lagoon type IV differs from all other distinguished lagoon types due to the dominance of the species Potamogeton pectinatus and the charophyte Chara hispida f. corfuensis. Regarding the macrophytic assemblages and the univariate variables, important differences were recorded between lagoon types. Chocked lagoons showed low number of species and Shannon diversity index comparing with restricted lagoon types (Types II and III). The multiple linear regression analysis showed that transparency, pH, nitrates, alkalinity and Chl-a could affect the values of the above variables. A decline of angiosperms was referred on a worldwide scale and recorded also in coastal lagoons of Western Greece. A gradual

  16. Variability in a Community-Structured SIS Epidemiological Model.

    Science.gov (United States)

    Hiebeler, David E; Rier, Rachel M; Audibert, Josh; LeClair, Phillip J; Webber, Anna

    2015-04-01

    We study an SIS epidemiological model of a population partitioned into groups referred to as communities, households, or patches. The system is studied using stochastic spatial simulations, as well as a system of ordinary differential equations describing moments of the distribution of infectious individuals. The ODE model explicitly includes the population size, as well as the variability in infection levels among communities and the variability among stochastic realizations of the process. Results are compared with an earlier moment-based model which assumed infinite population size and no variance among realizations of the process. We find that although the amount of localized (as opposed to global) contact in the model has little effect on the equilibrium infection level, it does affect both the timing and magnitude of both types of variability in infection level.

  17. Disturbance drives phylogenetic community structure in coastal dune vegetation

    DEFF Research Database (Denmark)

    Brunbjerg, A.K.; Borchsenius, Finn; Eiserhardt, Wolf L.

    2012-01-01

    sorting to be the dominant determinant in this metacommunity system, with soil moisture, pH, and fertility requirement patterns explaining ≥77% of the compositional gradients, while geographic factors accounted for ≤2%. Partial Mantel tests confirmed this finding, with 31.6% of the variation in species......It has long been thought that environmental factors determine plant community assembly, but it is now increasingly argued that geographic spatial processes such as dispersal may also matter. Notably, the metacommunity framework considers local communities to be linked by dispersal and different...... by the local environment and broader-scale geographic spatial processes for local plant species composition using a data set of 3924 plots from coastal dunes across a large region (Denmark). We used ordination to identify the main gradients in species composition, and Linear Mixed-Effects modelling (LME...

  18. Pentachlorophenol (PCP) degradation microorganism community structure under microaeration condition

    Institute of Scientific and Technical Information of China (English)

    Chen Yuancai; Hao Yuan; Fu Shiyu; Zhan Huaiyu

    2007-01-01

    The comparison of pentachlorophenol (PCP)degradation was conducted under micro-aeration and anaerobic condition with three series of batch experiment,results of which indicated that during micro-aeration condition co-immobilized of anaerobic granular sludge and isolated aerobic bacterial species could enhance the efficiency of PCP reduction through the synergism of aerobes and anaerobes reductive dechlorination and exchange of metabolites within the co-immobilized granular sludge.While during anaerobic condition,there was no great difference in the three series.The specific activities experiment further confirmed that strict anaerobes were not affected over the presence of micro aeration environment.Microorganism community construction of co-immobilized anaerobic granular sludge and the mixed isolated aerobic community was also deduced.By the efficient cooperation of aerobes and anaerobes,the high efficiency removal rate of PCP was implemented.

  19. Modeling Risk Perception in Networks with Community Structure

    CERN Document Server

    Bagnoli, Franco; Guazzini, Andrea; Massaro, Emanuele; Rudolph, Stefan

    2012-01-01

    We study the influence of global, local and community-level risk perception on the extinction probability of a disease in several models of social networks. In particular, we study the infection progression as a susceptible-infected-susceptible (SIS) model on several modular networks, formed by a certain number of random and scale-free communities. We find that in the scale-free networks the progression is faster than in random ones with the same average connectivity degree. For what concerns the role of perception, we find that the knowledge of the infection level in one's own neighborhood is the most effective property in stopping the spreading of a disease, but at the same time the more expensive one in terms of the quantity of required information, thus the cost/effectiveness optimum is a tradeoff between several parameters.

  20. Microbial community structure affects marine dissolved organic matter composition

    Directory of Open Access Journals (Sweden)

    Elizabeth B Kujawinski

    2016-04-01

    Full Text Available Marine microbes are critical players in the global carbon cycle, affecting both the reduction of inorganic carbon and the remineralization of reduced organic compounds back to carbon dioxide. Members of microbial consortia all depend on marine dissolved organic matter (DOM and in turn, affect the molecules present in this heterogeneous pool. Our understanding of DOM produced by marine microbes is biased towards single species laboratory cultures or simplified field incubations, which exclude large phototrophs and protozoan grazers. Here we explore the interdependence of DOM composition and bacterial diversity in two mixed microbial consortia from coastal seawater: a whole water community and a <1.0-μm community dominated by heterotrophic bacteria. Each consortium was incubated with isotopically-labeled glucose for 9 days. Using stable-isotope probing techniques and electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry, we show that the presence of organisms larger than 1.0-μm is the dominant factor affecting bacterial diversity and low-molecular-weight (<1000 Da DOM composition over this experiment. In the <1.0-μm community, DOM composition was dominated by compounds with lipid and peptide character at all time points, confirmed by fragmentation spectra with peptide-containing neutral losses. In contrast, DOM composition in the whole water community was nearly identical to that in the initial coastal seawater. These differences in DOM composition persisted throughout the experiment despite shifts in bacterial diversity, underscoring an unappreciated role for larger microorganisms in constraining DOM composition in the marine environment.

  1. Biofilm diatom community structure: Influence of temporal and substratum variability

    Digital Repository Service at National Institute of Oceanography (India)

    Patil, J.S.; Anil, A.C.

    . delicatula and Amphora (TableIIa–d).ANOVAalsorevealedsignificantsub- stratum variations with respect to months (Table III). Diatomdistributionencounteredonthetestsubstrata Figure 4. Cluster dendrogram based on density of diatoms from the ambient water. a... suggested that pennate diatoms dominate the diatom fouling community irrespective of the nature of the sub- stratum and the exposure period. The dominance of pennate diatoms has also been reported in biofouling on test coupons exposed in the Arabian Sea...

  2. 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

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

    Directory of Open Access Journals (Sweden)

    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

  4. Bacterial Community Structure is Indicative of Chemical Inputs in the Upper Mississippi River

    Directory of Open Access Journals (Sweden)

    Christopher eStaley

    2014-10-01

    Full Text Available Local and regional associations between bacterial communities and nutrient and chemical concentrations were assessed in the Upper Mississippi River in Minnesota to determine if community structure was associated with discrete types of chemical inputs associated with different land cover. Bacterial communities were characterized by Illumina sequencing of the V6 region of 16S rDNA and compared to > 40 chemical and nutrient concentrations. Local bacterial community structure was shaped primarily by associations among bacterial orders. However, order abundances were correlated regionally with nutrient and chemical concentrations, and were also related to major land coverage types. Total organic carbon and total dissolved solids were among the primary abiotic factors associated with local community composition and co-varied with land cover. Escherichia coli concentration was poorly related to community composition or nutrient concentrations. Abundances of fourteen bacterial orders were related to land coverage type, and seven showed significant differences in abundance (P ≤ 0.046 between forested or anthropogenically-impacted sites. This study identifies specific bacterial orders that were associated with chemicals and nutrients derived from specific land cover types and may be useful in assessing water quality. Results of this study reveal the need to investigate community dynamics at both the local and regional scales and to identify shifts in taxonomic community structure that may be useful in determining sources of pollution in the Upper Mississippi River.

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

    Science.gov (United States)

    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.

  6. Genetic variation in plant morphology contributes to the species-level structure of grassland communities.

    Science.gov (United States)

    Whitlock, Raj; Grime, J Phil; Burke, Terry

    2010-05-01

    It is becoming apparent that genetic diversity can influence the species diversity and structure of ecological communities. Here, we investigated the intraspecific trait variation responsible for this relationship. We grew 10 genotypes of the sedge Carex caryophyllea, as monocultures, under standardized conditions and measured traits related to morphology, growth, and life history. The same genotypes had been prominent in determining the structure of multispecies experimental communities, equivalent in species diversity, in which the genetic diversity of the constituent plant species had been varied in parallel. The trait measurements revealed substantial phenotypic variation among Carex genotypes, related predominantly to differences in physical size and to the spatial deployment of above- and belowground tissue. Genotypes successful in experimental communities were larger in size and tended to adopt a "guerrilla" clonal growth strategy. In general, multivariate trait summaries of genotype size (and to a lesser extent, variation along a linear discriminant axis) predicted genotype and species abundance in experimental communities. However, one genotype exhibited a large disparity in this respect. The performance of this genotype lay closer to prediction when it was growing with a highly competitive grass genotype. The strength of the relationship between genotype size and performance within communities decreased with decreasing community genetic diversity. These results indicate that intraspecific trait measurements are useful for predicting and understanding community structure. They also imply that competitive interactions between the genotypes of different species play an increased role in determining phenotype in genetically impoverished communities.

  7. Using a two-phase evolutionary framework to select multiple network spreaders based on community structure

    Science.gov (United States)

    Fu, Yu-Hsiang; Huang, Chung-Yuan; Sun, Chuen-Tsai

    2016-11-01

    Using network community structures to identify multiple influential spreaders is an appropriate method for analyzing the dissemination of information, ideas and infectious diseases. For example, data on spreaders selected from groups of customers who make similar purchases may be used to advertise products and to optimize limited resource allocation. Other examples include community detection approaches aimed at identifying structures and groups in social or complex networks. However, determining the number of communities in a network remains a challenge. In this paper we describe our proposal for a two-phase evolutionary framework (TPEF) for determining community numbers and maximizing community modularity. Lancichinetti-Fortunato-Radicchi benchmark networks were used to test our proposed method and to analyze execution time, community structure quality, convergence, and the network spreading effect. Results indicate that our proposed TPEF generates satisfactory levels of community quality and convergence. They also suggest a need for an index, mechanism or sampling technique to determine whether a community detection approach should be used for selecting multiple network spreaders.

  8. Bacterial community structure and soil properties of a subarctic tundra soil in Council, Alaska.

    Science.gov (United States)

    Kim, Hye Min; Jung, Ji Young; Yergeau, Etienne; Hwang, Chung Yeon; Hinzman, Larry; Nam, Sungjin; Hong, Soon Gyu; Kim, Ok-Sun; Chun, Jongsik; Lee, Yoo Kyung

    2014-08-01

    The subarctic region is highly responsive and vulnerable to climate change. Understanding the structure of subarctic soil microbial communities is essential for predicting the response of the subarctic soil environment to climate change. To determine the composition of the bacterial community and its relationship with soil properties, we investigated the bacterial community structure and properties of surface soil from the moist acidic tussock tundra in Council, Alaska. We collected 70 soil samples with 25-m intervals between sampling points from 0-10 cm to 10-20 cm depths. The bacterial community was analyzed by pyrosequencing of 16S rRNA genes, and the following soil properties were analyzed: soil moisture content (MC), pH, total carbon (TC), total nitrogen (TN), and inorganic nitrogen (NH4+ and NO3-). The community compositions of the two different depths showed that Alphaproteobacteria decreased with soil depth. Among the soil properties measured, soil pH was the most significant factor correlating with bacterial community in both upper and lower-layer soils. Bacterial community similarity based on jackknifed unweighted unifrac distance showed greater similarity across horizontal layers than through the vertical depth. This study showed that soil depth and pH were the most important soil properties determining bacterial community structure of the subarctic tundra soil in Council, Alaska.

  9. Trust-oriented Utility-based Community Structure in Multiagent Systems

    Science.gov (United States)

    Kastidou, Georgia; Cohen, Robin

    The problem we address in this chapter is how to design the community structure of a multiagent system in such a way that agents join the communities that will maximize their utility and communities accept the agents that will maximize their utility, towards a stable and productive multiagent system. In order to accomplish this goal, we propose allowing communities to exchange information about the reputability of agents. In particular, it agent a 1 exists in community c 1 and would now like to join c 2, c 2 will ask c 1 for the reputation rating of a 1 and then decide whether to allow the agent to join. Allowing for the sharing of reputation ratings then requires i) a method for determining the truthfulness of the reputation reports ii) an incentive mechanism to encourage the sharing of information iii) some consideration of privacy of information within the system. In order for agents to make effective selection of communities in which to participate, it is also ideal community enjoy and about the tendency for the community to be truthful, when it reports reputation ratings of agents. We present a reputation sharing system that promotes effective community structure, along with examples to demonstrate the benefit of this particular approach.

  10. Effects of high nitrogen concentrations on the growth of submersed macrophytes at moderate phosphorus concentrations.

    Science.gov (United States)

    Yu, Qing; Wang, Hong-Zhu; Li, Yan; Shao, Jian-Chun; Liang, Xiao-Min; Jeppesen, Erik; Wang, Hai-Jun

    2015-10-15

    Eutrophication of lakes leading to loss of submersed macrophytes and higher turbidity is a worldwide phenomenon, attributed to excessive loading of phosphorus (P). However, recently, the role of nitrogen (N) for macrophyte recession has received increasing attention. Due to the close relationship between N and P loading, disentanglement of the specific effects of these two nutrients is often difficult, and some controversy still exists as to the effects of N. We studied the effects of N on submersed macrophytes represented by Vallisneria natans (Lour.) Hara in pots positioned at three depths (0.4 m, 0.8 m, and 1.2 m to form a gradient of underwater light conditions) in 10 large ponds having moderate concentrations of P (TP 0.03 ± 0.04 mg L(-1)) and five targeted concentrations of total nitrogen (TN) (0.5, 2, 10, 20, and 100 mg L(-1)), there were two ponds for each treatment. To study the potential shading effects of other primary producers, we also measured the biomass of phytoplankton (ChlaPhyt) and periphyton (ChlaPeri) expressed as chlorophyll a. We found that leaf length, leaf mass, and root length of macrophytes declined with increasing concentrations of TN and ammonium, while shoot number and root mass did not. All the measured growth indices of macrophytes declined significantly with ChlaPhyt, while none were significantly related to ChlaPeri. Neither ChlaPhyt nor ChlaPeri were, however, significantly negatively related to the various N concentrations. Our results indicate that shading by phytoplankton unrelated to the variation in N loading and perhaps toxic stress exerted by high nitrogen were responsible for the decline in macrophyte growth.

  11. [Insect community structure and its stability in a Zanthoxylum bungeanum garden with different planting pattern].

    Science.gov (United States)

    Zhang, Xiao-Ming; Li, Qiang; Chen, Guo-Hua; Yang, Jie; Gao, Xin; Song, Jia-Xiong

    2009-08-01

    An investigation was made on the insect community composition and structure in a Zanthoxylum bungeanum garden with corn-soybean - Z. bungeanum intercropping, soybean - Z. bungeanum intercropping, corn - Z. bungeanum intercropping, and only Z. bungeanum planting in Zhaotong City of Yunnan Province, and the community character index and principal component analysis were used to study the characters and stability of the insect community. A total of 326 insect species were recorded. In intercropped plots, the abundance, diversity, and evenness index of insect community were higher while the dominance index was lower, compared with those in monocultured Z. bungeanum plot. The diversity index of insect community decreased in the order of corn-soybean- Z. bungeanum intercropping > soybean - Z. bungeanum intercropping > corn - Z. bungeanum intercropping > only Z. bungeanum planting, and the insect community in corn-soybean - Z. bungeanum intercropping plot was relatively stable.

  12. Quantitative Comparison of Abundance Structures of Generalized Communities: From B-Cell Receptor Repertoires to Microbiomes

    Science.gov (United States)

    Saeedghalati, Mohammadkarim; Farahpour, Farnoush; Lange, Anja; Westendorf, Astrid M.; Seifert, Marc; Küppers, Ralf

    2017-01-01

    The community, the assemblage of organisms co-existing in a given space and time, has the potential to become one of the unifying concepts of biology, especially with the advent of high-throughput sequencing experiments that reveal genetic diversity exhaustively. In this spirit we show that a tool from community ecology, the Rank Abundance Distribution (RAD), can be turned by the new MaxRank normalization method into a generic, expressive descriptor for quantitative comparison of communities in many areas of biology. To illustrate the versatility of the method, we analyze RADs from various generalized communities, i.e. assemblages of genetically diverse cells or organisms, including human B cells, gut microbiomes under antibiotic treatment and of different ages and countries of origin, and other human and environmental microbial communities. We show that normalized RADs enable novel quantitative approaches that help to understand structures and dynamics of complex generalized communities. PMID:28114391

  13. 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.

  14. The network structure of human personality according to the NEO-PI-R: matching network community structure to factor structure.

    Directory of Open Access Journals (Sweden)

    Rutger Goekoop

    Full Text Available INTRODUCTION: Human personality is described preferentially in terms of factors (dimensions found using factor analysis. An alternative and highly related method is network analysis, which may have several advantages over factor analytic methods. AIM: To directly compare the ability of network community detection (NCD and principal component factor analysis (PCA to examine modularity in multidimensional datasets such as the neuroticism-extraversion-openness personality inventory revised (NEO-PI-R. METHODS: 434 healthy subjects were tested on the NEO-PI-R. PCA was performed to extract factor structures (FS of the current dataset using both item scores and facet scores. Correlational network graphs were constructed from univariate correlation matrices of interactions between both items and facets. These networks were pruned in a link-by-link fashion while calculating the network community structure (NCS of each resulting network using the Wakita Tsurumi clustering algorithm. NCSs were matched against FS and networks of best matches were kept for further analysis. RESULTS: At facet level, NCS showed a best match (96.2% with a 'confirmatory' 5-FS. At item level, NCS showed a best match (80% with the standard 5-FS and involved a total of 6 network clusters. Lesser matches were found with 'confirmatory' 5-FS and 'exploratory' 6-FS of the current dataset. Network analysis did not identify facets as a separate level of organization in between items and clusters. A small-world network structure was found in both item- and facet level networks. CONCLUSION: We present the first optimized network graph of personality traits according to the NEO-PI-R: a 'Personality Web'. Such a web may represent the possible routes that subjects can take during personality development. NCD outperforms PCA by producing plausible modularity at item level in non-standard datasets, and can identify the key roles of individual items and clusters in the network.

  15. Ammonia-oxidizing Bacteria and Archaea in the Rhizosphere of Freshwater Macrophytes

    DEFF Research Database (Denmark)

    Herrmann, Martina; Schramm, Andreas

    2007-01-01

    AMMONIA-OXIDIZING ARCHAEA AND BACTERIA IN THE RHIZOSPHERE OF FRESHWATER MACROPHYTES Martina Herrmann and Andreas Schramm Department of Biological Sciences, Microbiology, University of Aarhus, Denmark Aquatic macrophytes such as Littorella uniflora and Lobelia dortmanna release oxygen from...... measurements revealed clear differences in ammonia oxidation rates. The diversity of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) was assessed using the ammonia monooxygenase (amoA) gene as functional marker. Both AOA and AOB could be detected in the rhizosphere of all three plant...

  16. Aquatic macrophyte richness in Danish lakes in relation to alkalinity, transparency, and lake area

    DEFF Research Database (Denmark)

    Vestergaard, Ole Skafte; Sand-Jensen, Kaj

    2000-01-01

    alkalinity but 12.3 in lakes of high alkalinity due to a greater occurrence of the species-rich group of elodeids. Mean species richness per lake also increased significantly with increasing Secchi depth. No significant relationship between species richness and lake surface area was observed among the entire...... group of lakes or a subset of eutrophic lakes, as the growth of submerged macrophytes in large lakes may be restricted by wave action in shallow water and light restriction in deep water. In contrast, macrophyte species richness increased with lake surface area in transparent lakes, presumably due...

  17. Predicting aquatic macrophyte occurrence in soft-water oligotrophic lakes (Pyrenees mountain range

    Directory of Open Access Journals (Sweden)

    Cristina Pulido

    2014-08-01

    Full Text Available Distribution of aquatic macrophytes in lakes is related to geographical, morphological, catchment and water chemistry variables as well as human impacts, which modify the original environment. Here, we aim at building statistical models to establish the ecological niches of 11 aquatic macrophytes (10 different phanerogams and the genus Nitella from oligotrophic soft-water lakes and infer their ecological requirements and environmental constraints at the southernmost limit of their distribution. Macrophyte occurrence and environmental variables were obtained from 86 non-exploited oligotrophic soft-water lakes from the Pyrenees (Southern Europe; 42º50´N, 1º00´E; macrophytes inhabited 55 of these lakes. Optimum ranges and macrophyte occurrence were predicted in relation to 18 geographical, morphological, catchment and water chemistry variables using univariate and multivariate logistic models. Lakes at low altitude, in vegetated catchments and with low water concentration of NO3- and SO4-2, were the most suitable to host macrophytes. In general, individual species of aquatic macrophytes showed clear patterns of segregation along conductivity and pH gradients, although the specific combination of variables selected in the best models explaining their occurrence differed among species.  Based on the species response to pH and conductivity, we found Isoetes lacustris have its optimum in waters with low conductivity and pH (i.e. negative monotonic response. In contrast, Callitriche palustris, Ranunculus aquatilis, Subularia aquatica, Nitella spp., and Myriophyllum alterniflorum showed an optimum at intermediate values (i.e. unimodal response, whereas Potamogeton berchtoldii, Potamogeton alpinus, and Ranunculus trichophyllus as species had their optimum at relatively high water pH and conductivity (i.e. positive monotonic response. This pattern has been observed in other regions for the same species, although with different optima and tolerance

  18. Distribution and structure of zooplankton communities in the austral summer in the Prydz Bay, Antarctica

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    As a structure linking the ecosystem and population, community plays an important role in the marine ecology. Abundance of different species and development stages were used in our classification to the sampling stations with clustering-analysis and multi-dimension scaling, through which three geographic communities were marked out, respectively as following: the Salp community characterized by presence of Salp thompni in the northern area, the Near-shore community by Euphausia crystallorophias in the south and the main ocean community located between the above two communities. Indicator species method was then carried out between every two communities to findout which species or stages differ most. It tells that Rhincalanus gigas, adult cheatognath, late stages of Metridia gerlachei and calyptopis of Euphausiidae are indicators between Salp and neritic communities, between Krill and Salp communities are Salp thompni, adult and larvae of Cheatognath and R. gigas, and the most notable indicator between the Krill and the neritic communities are E. crystallorophias, then nauplii of Euphausiidae and Onceae conifera with less evidence.

  19. Phenol toxicity to the aquatic macrophyte Lemna paucicostata

    Energy Technology Data Exchange (ETDEWEB)

    Park, Ji-Sook [Division of Life Science, University of Incheon, Incheon 406-840 (Korea, Republic of); Brown, Murray T. [School of Marine Science and Engineering, University of Plymouth, Plymouth, Devon PL4 8AA (United Kingdom); Han, Taejun, E-mail: hanalgae@hanmail.net [Division of Life Science, University of Incheon, Incheon 406-840 (Korea, Republic of); Institute of Green Environmental Research, University of Incheon, Incheon 406-840 (Korea, Republic of)

    2012-01-15

    Phenol is a ubiquitous environmental pollutant and a widely used reference toxicant for many bioassays. However, little information is available regarding the toxic effects of phenol on aquatic macrophytes. Seventy-two hour bioassays, with different end-points, were carried out to assess phenol toxicity in Lemna paucicostata. A concentration-dependent decline in frond multiplication and colony disintegration was observed, with 11.38 and 22.76 {mu}M phenol resulting in browning of fronds and colony disintegration, respectively. Growth of fronds, as measured by changes in surface area, was significantly inhibited with EC{sub 50} value of 2.70 {mu}M. When pulse amplitude modulated chlorophyll a (Chl a) fluorescence imaging (i-PAM) was employed, the maximum quantum yield of PS II (F{sub v}/F{sub m}) significantly declined with increasing phenol concentrations with resultant EC{sub 50} of 1.91 {mu}M and coefficients of variation (CVs) generated for the EC{sub 50} values of less than 4.7%. A gradual increase in fluorescence emissions from chlorophylls a and b and pheophytin up to a concentration of 2.85 {mu}M was found but declined markedly at higher concentrations. The significant correlation between the F{sub v}/F{sub m} and surface growth rate data implies that the former is an appropriate biomarker of whole plant toxicity. Using imaging Chl a fluorescence on L. paucicostata provides a rapid, sensitive and reliable method for assessing the toxic risks posed by phenol to aquatic ecosystems and has practical applications for municipal and industrial waste water management.

  20. Structure of the scientific community modelling the evolution of resistance.

    Science.gov (United States)

    2007-12-05

    Faced with the recurrent evolution of resistance to pesticides and drugs, the scientific community has developed theoretical models aimed at identifying the main factors of this evolution and predicting the efficiency of resistance management strategies. The evolutionary forces considered by these models are generally similar for viruses, bacteria, fungi, plants or arthropods facing drugs or pesticides, so interaction between scientists working on different biological organisms would be expected. We tested this by analysing co-authorship and co-citation networks using a database of 187 articles published from 1977 to 2006 concerning models of resistance evolution to all major classes of pesticides and drugs. These analyses identified two main groups. One group, led by ecologists or agronomists, is interested in agricultural crop or stock pests and diseases. It mainly uses a population genetics approach to model the evolution of resistance to insecticidal proteins, insecticides, herbicides, antihelminthic drugs and miticides. By contrast, the other group, led by medical scientists, is interested in human parasites and mostly uses epidemiological models to study the evolution of resistance to antibiotic and antiviral drugs. Our analyses suggested that there is also a small scientific group focusing on resistance to antimalaria drugs, and which is only poorly connected with the two larger groups. The analysis of cited references indicates that each of the two large communities publishes its research in a different set of literature and has its own keystone references: citations with a large impact in one group are almost never cited by the other. We fear the lack of exchange between the two communities might slow progress concerning resistance evolution which is currently a major issue for society.

  1. The type of carbohydrates specifically selects microbial community structures and fermentation patterns.

    Science.gov (United States)

    Chatellard, Lucile; Trably, Eric; Carrère, Hélène

    2016-12-01

    The impact on dark fermentation of seven carbohydrates as model substrates of lignocellulosic fractions (glucose, cellobiose, microcrystalline cellulose, arabinose, xylose, xylan and wheat straw) was investigated. Metabolic patterns and bacterial communities were characterized at the end of batch tests inoculated with manure digestate. It was found that hydrogen production was linked to the sugar type (pentose or hexose) and the degree of polymerisation. Hexoses produced less hydrogen, with a specific selection of lactate-producing bacterial community structures. Maximal hydrogen production was five times higher on pentose-based substrates, with specific bacterial community structures producing acetate and butyrate as main metabolites. Low hydrogen amounts accumulated from complex sugars (cellulose, xylan and wheat straw). A relatively high proportion of the reads was affiliated to Ruminococcaceae suggesting an efficient hydrolytic activity. Knowing that the bacterial community structure is very specific to a particular substrate offers new possibilities to design more efficient H2-producing biological systems.

  2. Optimal Control Strategy for Traffic Driven Epidemic Spreading Based on Community Structure

    Directory of Open Access Journals (Sweden)

    Fei Shao

    2013-01-01

    Full Text Available It is shown that community structure has a great impact on traffic transportation and epidemic spreading. The density of infected nodes and the epidemic threshold have been proven to have significant relationship with the node betweenness in traffic driven epidemic spreading method. In this paper, considering the impact of community structure on traffic driven epidemic spreading, an effective and novel strategy to control epidemic spreading in scale-free networks is proposed. Theoretical analysis shows that the new control strategy will obviously increase the ratio between the first and the second moments of the node betweenness distribution in scale-free networks. It is also found that the more accurate the community is identified, the stronger community structure the network has and the more efficient the control strategy is. Simulations on both computer-generated and real-world networks have confirmed the theoretical results.

  3. On the relationship between the structural and socioacademic communities of an interdisciplinary coauthorship network

    CERN Document Server

    Rodriguez, Marko A

    2008-01-01

    This article presents a study that compares detected structural communities in a coauthorship network to the socioacademic characteristics of the scholars that compose the network. The coauthorship network was created from the bibliographic record of an overt interdisciplinary research group focused on sensor networks and wireless communication. The popular leading eigenvector community detection algorithm was employed to assign a structural community to each scholar in the network. Socioacademic characteristics were gathered from the scholars and include such information as their academic department, academic affiliation, country of origin, and academic position. A Pearson's $\\chi^2$ test, with a simulated Monte Carlo, revealed that structural communities best represent groupings of individuals working in the same academic department and at the same institution. A generalization of this result indicates that, contrary to the common conception of a multi-institutional interdisciplinary research group, collabo...

  4. Community Structure of Urban Forest and Disposition Characteristics of Trees in Hefei Ring Park

    Institute of Scientific and Technical Information of China (English)

    WUZemin; WANGYuan; ZHANGShaojie; YANGHaiyan; XUYinbi

    2004-01-01

    The methods of vegetation ecology were used to analyze the community structure of Hefei Ring Park, and species composition, distribution pattern of tree height and DBH were described. Through calculation of tree growth index and association correlation of component species, the community structures were analyzed. The results showed that community structures are complex, there are 22 pairs of species with positive association, and tree individual in the following communities grow well and are more stable, the major are Platycladus orientalis-Prunus cerasifera fatropurpurea-Osmanthus fragrans, Robinia pseduacacia-Ligustrum lucidum, Robinia pseudoacacia-Ginkgo biloba-Photinia serrulata, Populus cadadensis-Ligustrum lucidum-Osmanthus fragrans, Sophora japonica-Ligustrum lucidum-Buxus sinica, Cyclobalanopsis glauca-Distylium racemosum.

  5. Bacterial and Fungal Community Structures in Loess Plateau Grasslands with Different Grazing Intensities

    Directory of Open Access Journals (Sweden)

    Huhe

    2017-04-01

    Full Text Available The Loess Plateau of China is one of the most fragile ecosystems worldwide; thus, human production activities need to be conducted very cautiously. In this study, MiSeq high-throughput sequencing was applied to assess the relationship between bacterial and fungal community structures and changes in vegetation and soil physical and chemical properties induced by grazing, in four grasslands with different levels of grazing intensity (0, 2.67, 5.33, and 8.67 sheep/ha in the semiarid region of the Loess Plateau. The relative abundances of the bacterial community in the grasslands with 2.67 and 5.33 sheep/ha were significantly higher than those in grasslands with 0 and 8.67 sheep/ha, and the fungal diversity was significantly lower for grasslands with 2.67 sheep/ha than for the other grasslands. Redundancy analysis (RDA showed that plant biomass, nitrate, and total nitrogen have significant effects on bacterial community structure, whereas nitrate and total nitrogen also significantly affect fungal community structure. Variation partitioning showed that soil and plant characteristics influence the bacterial and fungal community structures; these characteristics explained 51.9 and 52.9% of the variation, respectively. Thus, bacterial and fungal community structures are very sensitive to grazing activity and change to different extents with different grazing intensities. Based on our findings, a grazing intensity of about 2.67 sheep/ha is considered the most appropriate in semiarid grassland of the Loess Plateau.

  6. The structure and functions of bacterial communities in an agrocenosis

    Science.gov (United States)

    Dobrovol'skaya, T. G.; Khusnetdinova, K. A.; Manucharova, N. A.; Balabko, P. N.

    2016-01-01

    The most significant factor responsible for the specific taxonomic composition of the bacterial communities in the agrocenosis studied was found to be a part or organ of plants (leaves, flowers, roots, fruits). A stage of plant ontogeny also determines changes of taxa. In the course of the plant growth, eccrisotrophic bacteria are replaced by hydrolytic ones that belong to the group of cellulose-decomposing bacteria. Representatives of the proteobacteria genera that are difficult to identify by phenotypic methods were determined using molecular-biological methods. They were revealed only on oat leaves in the moist period. As the vetch-oat mixture was fertilized with BIOUD-1 (foliar application) in the phyllosphere of both oats and vetch, on all the plant organs, representatives of the Rhodococcus genus as dominants were isolated. This fact was related to the capability of bacteria to decompose the complex aromatic compounds that are ingredients of the fertilizers applied. Another positive effect for plants of the bacterial communities forming in agrocenoses is the presence of bacteria that are antagonists of phytopathogenic bacteria. Thus, in agrocenoses, some interrelationships promoting the growth and reproduction of plants are formed in crop plants and bacteria.

  7. Can microcystins affect zooplankton structure community in tropical eutrophic reservoirs?

    Directory of Open Access Journals (Sweden)

    T. A. S. V. Paes

    Full Text Available Abstract The aim of our study was to assess whether cyanotoxins (microcystins can affect the composition of the zooplankton community, leading to domination of microzooplankton forms (protozoans and rotifers. Temporal variations in concentrations of microcystins and zooplankton biomass were analyzed in three eutrophic reservoirs in the semi-arid northeast region of Brazil. The concentration of microcystins in water proved to be correlated with the cyanobacterial biovolume, indicating the contributions from colonial forms such as Microcystis in the production of cyanotoxins. At the community level, the total biomass of zooplankton was not correlated with the concentration of microcystin (r2 = 0.00; P > 0.001, but in a population-level analysis, the biomass of rotifers and cladocerans showed a weak positive correlation. Cyclopoid copepods, which are considered to be relatively inefficient in ingesting cyanobacteria, were negatively correlated (r2 = – 0.01; P > 0.01 with the concentration of cyanotoxins. Surprisingly, the biomass of calanoid copepods was positively correlated with the microcystin concentration (r2 = 0.44; P > 0.001. The results indicate that allelopathic control mechanisms (negative effects of microcystin on zooplankton biomass do not seem to substantially affect the composition of mesozooplankton, which showed a constant and high biomass compared to the microzooplankton (rotifers. These results may be important to better understand the trophic interactions between zooplankton and cyanobacteria and the potential effects of allelopathic compounds on zooplankton.

  8. Violence, omissions and structures faced by LGBTI community individuals

    Directory of Open Access Journals (Sweden)

    Manuel Fernando Quinche Ramírez

    2016-07-01

    text works on the issue of legislative and conventional omissions, and identifies some of the traditional domain structures, those that impede the recognition and protection of this community’s rights.

  9. Creation of the Organisational Structure of a Safe Community

    National Research Council Canada - National Science Library

    Birute Pitrenaite; Algirdas Astrauskas; Birute Mikulskiene

    2011-01-01

    .... This study is intended to begin filling this gap. The objective of this paper is to offer the municipal organisational structure as one of the prerequisites for safe design and development of the municipality...

  10. Communities, modules and large-scale structure in networks

    Science.gov (United States)

    Newman, M. E. J.

    2012-01-01

    Networks, also called graphs by mathematicians, provide a useful abstraction of the structure of many complex systems, ranging from social systems and computer networks to biological networks and the state spaces of physical systems. In the past decade there have been significant advances in experiments to determine the topological structure of networked systems, but there remain substantial challenges in extracting scientific understanding from the large quantities of data produced by the experiments. A variety of basic measures and metrics are available that can tell us about small-scale structure in networks, such as correlations, connections and recurrent patterns, but it is considerably more difficult to quantify structure on medium and large scales, to understand the `big picture'. Important progress has been made, however, within the past few years, a selection of which is reviewed here.

  11. Metabolic and structural response of hyporheic microbial communities to variations in supply of dissolved organic matter

    Science.gov (United States)

    Findlay, S.E.G.; Sinsabaugh, R. L.; Sobczak, W.V.; Hoostal, M.

    2003-01-01

    Hyporheic sediment bacterial communities were exposed to dissolved organic matter (DOM) from a variety of sources to assess the interdependence of bacterial metabolism and community composition. Experiments ranged from small-scale core perfusions with defined compounds (glucose, bovine serum albumin) to mesocosms receiving natural leaf leachate or water from different streams. Response variables included bacterial production, oxygen consumption, extracellular enzyme activity, and community similarity as manifest by changes in banding patterns of randomly amplified polymorphic DNA (RAPD). All DOM manipulations generated responses in at least one metabolic variable. Additions of both labile and recalcitrant materials increased either oxygen consumption, production, or both depending on background DOM. Enzyme activities were affected by both types of carbon addition with largest effects from the labile mixture. Cluster analysis of RAPD data showed strong divergence of communities exposed to labile versus recalcitrant DOM. Additions of leaf leachate to mesocosms representing hyporheic flow-paths caused increases in oxygen consumption and some enzyme activities with weaker effects on production. Community structure yeas strongly affected; samples from the leachate-amended mesocosms clustered separately from the control samples. In mesocosms receiving water from streams ranging in DOC (0.5-4.5 mg L-1), there were significant differences in bacterial growth, oxygen consumption, and enzyme activities. RAPD analysis showed strongest clustering of samples by stream type with more subtle effects of position along the flowpaths. Responses in community metabolism were always accompanied by shifts in community composition, suggesting carbon supply affects both functional and structural attributes of hyporheic bacterial communities.

  12. Traveling salesman problems with PageRank Distance on complex networks reveal community structure

    Science.gov (United States)

    Jiang, Zhongzhou; Liu, Jing; Wang, Shuai

    2016-12-01

    In this paper, we propose a new algorithm for community detection problems (CDPs) based on traveling salesman problems (TSPs), labeled as TSP-CDA. Since TSPs need to find a tour with minimum cost, cities close to each other are usually clustered in the tour. This inspired us to model CDPs as TSPs by taking each vertex as a city. Then, in the final tour, the vertices in the same community tend to cluster together, and the community structure can be obtained by cutting the tour into a couple of paths. There are two challenges. The first is to define a suitable distance between each pair of vertices which can reflect the probability that they belong to the same community. The second is to design a suitable strategy to cut the final tour into paths which can form communities. In TSP-CDA, we deal with these two challenges by defining a PageRank Distance and an automatic threshold-based cutting strategy. The PageRank Distance is designed with the intrinsic properties of CDPs in mind, and can be calculated efficiently. In the experiments, benchmark networks with 1000-10,000 nodes and varying structures are used to test the performance of TSP-CDA. A comparison is also made between TSP-CDA and two well-established community detection algorithms. The results show that TSP-CDA can find accurate community structure efficiently and outperforms the two existing algorithms.

  13. Disturbed subsurface microbial communities follow equivalent trajectories despite different structural starting points

    Energy Technology Data Exchange (ETDEWEB)

    Handley, Kim M.; Wrighton, Kelly C.; Miller, Christopher S.; Wilkins, Michael J.; Kantor, Rose S.; Thomas, Brian C.; Williams, Kenneth H.; Gilbert, Jack A.; Long, Philip E.; Banfield, Jillian F.

    2015-03-01

    We explored the impact of the starting community composition and structure on ecosystem response to perturbations using organic carbon amendment experiments. Subsurface sediment was partitioned into flow-through columns, and the microbial communities were initially stimulated in situ by addition of acetate as a carbon and electron donor source. This drove community richness and evenness down, and pushed the system into a new biogeochemical state characterized by iron reduction. Reconstructed near-full-length 16S rRNA gene sequence analysis indicated a concomitant enrichment of Desulfuromonadales, Comamonadaceae and Bacteroidetes lineages. After 10 to 12 days, acetate was exchange for lactate in a subset of columns. Following the clear onset of sulfate reduction (35 days after acetate-amendment), acetate was substituted for lactate in additional columns. Acetatestimulated communities differed markedly during each biogeochemical regime and at each lactate-switch. Regardless, however, of when communities were switched to lactate, they followed comparable trajectories with respect to composition and structure, with convergence evident one week after each switch, and marked after one month of lactate amendment. During sulfate reduction all treatments were enriched in Firmicutes and a number of species likely involved in sulfate reduction (notably Desulfobulbus, Desulfosporosinus, Desulfitobacterium and Desulfotomaculum). Lactate treatments were distinguished by substantially lower relative abundances of Desulfotomaculum and Bacteroidetes, and enrichments of Psychrosinus and Clostridiales species. Results imply that the structure of the starting community was not significant in controlling organism selection in community succession.

  14. Spatial variability, structure and composition of crustose algal communities in Diadema africanum barrens

    Science.gov (United States)

    Sangil, Carlos; Sansón, Marta; Díaz-Villa, Tania; Hernández, José Carlos; Clemente, Sabrina; Afonso-Carrillo, Julio

    2014-12-01

    Crustose algal communities were studied in Diadema africanum urchin barrens around Tenerife (Canary Islands, NE Atlantic). A hierarchical nested sampling design was used to study patterns of community variability at different spatial scales (sectors, three sides of the island; sites within each sector, 5-10 km apart; stations within each site, 50-100 m apart). Although noncrustose species contributed the most to community richness, cover was dominated by crustose forms, like the coralline algae Hydrolithon farinosum, H. samoënse, H. onkodes, Neogoniolithon orotavicum and N. hirtum, and the phaeophycean Pseudolithoderma adriaticum. The structure of these communities showed high spatial variability, and we found differences in the structure of urchin barrens when compared across different spatial scales. Multivariate analysis showed that variability in community structure was related to the five environmental variables studied (wave exposure, urchin density, substrate roughness, productivity and depth). Wave exposure was the variable that contributed most to community variability, followed by urchin density and substrate roughness. Productivity and depth had limited influence. The effects of these variables differed depending on the spatial scale; wave exposure and productivity were the main variables influencing community changes at the largest scale (between different sectors of the island), while D. africanum density, roughness and depth were the most influential at medium and small scales.

  15. Community structure and regeneration types of Betula dahurica forest in Badaling forest center of Beijing

    Institute of Scientific and Technical Information of China (English)

    Zhang Yong; Zheng Zhi-hua; Zhang Zhi-xiang

    2007-01-01

    Using plant community analysis methods, we analyzed the floristic characteristics, species composition, community structure, population structure, and spatial distribution patterns of a Betula dahurica forest on the "1238" mountain of Badaling in Beijing, China. The results show that: 1) There are 33 plant species in the B. dahurica community, including 18 woody plant species. The B. dahurica forest is a monodominant community with 75.9% dominance. 2) Based on diameter at breast height (DBH)size class distribution, the population structure of B. dahurica and Acer mono-two heliophyllous and pioneer tree species is cascade-type, with both in an increasing stage. The population structure of Tilia mandshurica and T. mongolica, two shade-tolerant tree species, is inverse-J type, and they have more young seedling individuals and regenerate more stably. They are associated species of the pioneer tree species. The population structure of Quercus mongolica, as the associated species of climax species in the community, is sporadic, and its regeneration is fluctuating and random. Fraxinus rhynchophylla is a shade-tolerant tree species which has a unibar population structure and climax characteristics of pioneer tree species. The relative frequency of young seedlings reached 0.4.3) The dominant species B. dahurica is still in an increasing stage, and the regeneration of other species is steady or partly influences the community, putting the community in the pioneer species stage. From the population structure and distribution frequency ofF. rhynchophylla, the B. dahurica forest will approach to a climax state in the future.

  16. Relationship between phenol degradation efficiency and microbial community structure in an anaerobic SBR.

    Science.gov (United States)

    Rosenkranz, F; Cabrol, L; Carballa, M; Donoso-Bravo, A; Cruz, L; Ruiz-Filippi, G; Chamy, R; Lema, J M

    2013-11-01

    Phenol is a common wastewater contaminant from various industrial processes, including petrochemical refineries and chemical compounds production. Due to its toxicity to microbial activity, it can affect the efficiency of biological wastewater treatment processes. In this study, the efficiency of an Anaerobic Sequencing Batch Reactor (ASBR) fed with increasing phenol concentrations (from 120 to 1200 mg L(-1)) was assessed and the relationship between phenol degradation capacity and the microbial community structure was evaluated. Up to a feeding concentration of 800 mg L(-1), the initial degradation rate steadily increased with phenol concentration (up to 180 mg L(-1) d(-1)) and the elimination capacity remained relatively constant around 27 mg phenol removed∙gVSS(-1) d(-1). Operation at higher concentrations (1200 mg L(-1)) resulted in a still efficient but slower process: the elimination capacity and the initial degradation rate decreased to, respectively, 11 mg phenol removed∙gVSS(-1) d(-1) and 154 mg L(-1) d(-1). As revealed by Denaturing Gradient Gel Electrophoresis (DGGE) analysis, the increase of phenol concentration induced level-dependent structural modifications of the community composition which suggest an adaptation process. The increase of phenol concentration from 120 to 800 mg L(-1) had little effect on the community structure, while it involved drastic structural changes when increasing from 800 to 1200 mg L(-1), including a strong community structure shift, suggesting the specialization of the community through the emergence and selection of most adapted phylotypes. The thresholds of structural and functional disturbances were similar, suggesting the correlation of degradation performance and community structure. The Canonical Correspondence Analysis (CCA) confirmed that the ASBR functional performance was essentially driven by specific community traits. Under the highest feeding concentration, the most abundant ribotype probably involved in

  17. Genetic and ontogenetic variation in an endangered tree structures dependent arthropod and fungal communities.

    Directory of Open Access Journals (Sweden)

    Benjamin J Gosney

    Full Text Available Plant genetic and ontogenetic variation can significantly impact dependent fungal and arthropod communities. However, little is known of the relative importance of these extended genetic and ontogenetic effects within a species. Using a common garden trial, we compared the dependent arthropod and fungal community on 222 progeny from two highly differentiated populations of the endangered heteroblastic tree species, Eucalyptus morrisbyi. We assessed arthropod and fungal communities on both juvenile and adult foliage. The community variation was related to previous levels of marsupial browsing, as well as the variation in the physicochemical properties of leaves using near-infrared spectroscopy. We found highly significant differences in community composition, abundance and diversity parameters between eucalypt source populations in the common garden, and these were comparable to differences between the distinctive juvenile and adult foliage. The physicochemical properties assessed accounted for a significant percentage of the community variation but did not explain fully the community differences between populations and foliage types. Similarly, while differences in population susceptibility to a major marsupial herbivore may result in diffuse genetic effects on the dependent community, this still did not account for the large genetic-based differences in dependent communities between populations. Our results emphasize the importance of maintaining the populations of this rare species as separate management units, as not only are the populations highly genetically structured, this variation may alter the trajectory of biotic colonization of conservation plantings.

  18. Diatom community structure on commercially available ship hull coatings.

    Science.gov (United States)

    Zargiel, Kelli A; Coogan, Jeffrey S; Swain, Geoffrey W

    2011-10-01

    Diatoms are primary colonizers of both antifouling and fouling-release ship hull coatings. There are few published studies which report on diatom community development on modern ship hull coatings. This study reports diatom communities on eight commercial marine ship hull coatings exposed at three static immersion sites along the east coast of Florida, viz. Daytona, Sebastian, and Miami. The coatings tested were three ablative copper systems (Ameron ABC-3, International BRA-640, and Hempel Olympic 76600), two copper-free biocidal systems (E-Paint SN-1, Sherwin Williams HMF), and three fouling-release (FR) systems (International Intersleek 700, International Intersleek 900, and Hempel Hempasil). One hundred and twenty-seven species comprising 44 genera were identified, including some of the more commonly known foulers, viz. Achnanthes, Amphora, Cocconeis, Entomoneis, Licmophora, Melosira, Navicula, Nitzschia, Synedra, and Toxarium. A significant difference was seen among sites, with the more estuarine site, Sebastian, having lower overall diatom abundance and higher diversity than Daytona and Miami. Copper coatings were primarily fouled by Amphora delicatissima and Entomoneis pseudoduplex. Copper-free coatings were fouled by Cyclophora tenuis, A. delicatissima, Achnanthes manifera, and Amphora bigibba. FR surfaces were typified by C. tenuis, and several species of Amphora. The presence of C. tenuis is new to the biofouling literature, but as new coatings are developed, this diatom may be one of many that prove to be problematic for static immersion. Results show coatings can be significantly influenced by geographical area, highlighting the need to test ship hull coatings in locations similar to where they will be utilized.

  19. Microbes as engines of ecosystem function: when does community structure enhance predictions of ecosystem processes?

    Directory of Open Access Journals (Sweden)

    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.

  20. 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.

  1. 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.

  2. Bacterial community structure and diversity in a black soil as affected by long-term fertilization

    Institute of Scientific and Technical Information of China (English)

    WEI Dan; YANG Qian; ZHANG Jun-Zheng; WANG Shuang; CHEN Xue-Li; ZHANG Xi-Lin; LI Wei-Qun

    2008-01-01

    Black soil (Mollisol) is one of the main soil types in northeastern China.Biolog and polymerase chain reactiondenaturing gradient gel electrophoresis (PCR-DGGE) methods were used to examine the influence of various fertilizer combinations on the structure and function of the bacterial community in a black soil collected from Harbin,Heilongjiang Province.Biolog results showed that substrate richness and catabolic diversity of the soil bacterial community were the greatest in the chemical fertilizer and chemical fertilizer+manure treatments.The metabolic ability of the bacterial community in the manure treatment was similar to the control.DGGE fingerprinting indicated similarity in the distribution of most 16S rDNA bands among all treatments,suggesting that microorganisms with those bands were stable and not influenced by fertilization.However,chemical fertilizer increased the diversity of soil bacterial community.Principal component analysis of Biolog and DGGE data revealed that the structure and function of the bacterial community were similar in the control and manure treatments,suggesting that the application of manure increased the soil microbial population,but had no effect on the bacterial community structure.Catabolic function was similar in the chemical fertilizer and chemical fertilizer+manure treatments,but the composition structure of the soil microbes differed between them.The use of chemical fertilizers could result in a decline in the catabolic activity of fast-growing or eutrophic bacteria.

  3. Dynamic community detection based on network structural perturbation and topological similarity

    Science.gov (United States)

    Wang, Peizhuo; Gao, Lin; Ma, Xiaoke

    2017-01-01

    Community detection in dynamic networks has been extensively studied since it sheds light on the structure-function relation of the overall complex systems. Recently, it has been demonstrated that the structural perturbation in static networks is excellent in characterizing the topology. In order to investigate the perturbation structural theory in dynamic networks, we extend the theory by considering the dynamic variation information between networks of consecutive time. Then a novel similarity is proposed by combing structural perturbation and topological features. Finally, we present an evolutionary clustering algorithm to detect dynamic communities under the temporal smoothness framework. Experimental results on both artificial and real dynamic networks demonstrate that the proposed similarity is promising in dynamic community detection since it improves the clustering accuracy compared with state-of-the-art methods, indicating the superiority of the presented similarity measure.

  4. Dynamical origins of the community structure of multi-layer societies

    CERN Document Server

    Klimek, Peter; Eguiluz, Victor; Miguel, Maxi San; Thurner, Stefan

    2016-01-01

    Social structures emerge as a result of individuals managing a variety of different of social relationships. Societies can be represented as highly structured dynamic multiplex networks. Here we study the dynamical origins of the specific community structures of a large-scale social multiplex network of a human society that interacts in a virtual world of a massive multiplayer online game. There we find substantial differences in the community structures of different social actions, represented by the various network layers in the multiplex. Community size distributions are either similar to a power-law or appear to be centered around a size of 50 individuals. To understand these observations we propose a voter model that is built around the principle of triadic closure. It explicitly models the co-evolution of node- and link-dynamics across different layers of the multiplex. Depending on link- and node fluctuation rates, the model exhibits an anomalous shattered fragmentation transition, where one layer frag...

  5. Linking geology and microbiology: inactive pockmarks affect sediment microbial community structure.

    Directory of Open Access Journals (Sweden)

    Thomas H A Haverkamp

    Full Text Available Pockmarks are geological features that are found on the bottom of lakes and oceans all over the globe. Some are active, seeping oil or methane, while others are inactive. Active pockmarks are well studied since they harbor specialized microbial communities that proliferate on the seeping compounds. Such communities are not found in inactive pockmarks. Interestingly, inactive pockmarks are known to have different macrofaunal communities compared to the surrounding sediments. It is undetermined what the microbial composition of inactive pockmarks is and if it shows a similar pattern as the macrofauna. The Norwegian Oslofjord contains many inactive pockmarks and they are well suited to study the influence of these geological features on the microbial community in the sediment. Here we present a detailed analysis of the microbial communities found in three inactive pockmarks and two control samples at two core depth intervals. The communities were analyzed using high-throughput amplicon sequencing of the 16S rRNA V3 region. Microbial communities of surface pockmark sediments were indistinguishable from communities found in the surrounding seabed. In contrast, pockmark communities at 40 cm sediment depth had a significantly different community structure from normal sediments at the same depth. Statistical analysis of chemical variables indicated significant differences in the concentrations of total carbon and non-particulate organic carbon between 40 cm pockmarks and reference sample sediments. We discuss these results in comparison with the taxonomic classification of the OTUs identified in our samples. Our results indicate that microbial communities at the sediment surface are affected by the water column, while the deeper (40 cm sediment communities are affected by local conditions within the sediment.

  6. Linking geology and microbiology: inactive pockmarks affect sediment microbial community structure.

    Science.gov (United States)

    Haverkamp, Thomas H A; Hammer, Øyvind; Jakobsen, Kjetill S

    2014-01-01

    Pockmarks are geological features that are found on the bottom of lakes and oceans all over the globe. Some are active, seeping oil or methane, while others are inactive. Active pockmarks are well studied since they harbor specialized microbial communities that proliferate on the seeping compounds. Such communities are not found in inactive pockmarks. Interestingly, inactive pockmarks are known to have different macrofaunal communities compared to the surrounding sediments. It is undetermined what the microbial composition of inactive pockmarks is and if it shows a similar pattern as the macrofauna. The Norwegian Oslofjord contains many inactive pockmarks and they are well suited to study the influence of these geological features on the microbial community in the sediment. Here we present a detailed analysis of the microbial communities found in three inactive pockmarks and two control samples at two core depth intervals. The communities were analyzed using high-throughput amplicon sequencing of the 16S rRNA V3 region. Microbial communities of surface pockmark sediments were indistinguishable from communities found in the surrounding seabed. In contrast, pockmark communities at 40 cm sediment depth had a significantly different community structure from normal sediments at the same depth. Statistical analysis of chemical variables indicated significant differences in the concentrations of total carbon and non-particulate organic carbon between 40 cm pockmarks and reference sample sediments. We discuss these results in comparison with the taxonomic classification of the OTUs identified in our samples. Our results indicate that microbial communities at the sediment surface are affected by the water column, while the deeper (40 cm) sediment communities are affected by local conditions within the sediment.

  7. Importance of structure and density of macroalgae communities (Fucus serratus) for photosynthetic production and light utilisation

    DEFF Research Database (Denmark)

    Binzer, Thomas; Sand-Jensen, Kaj

    2002-01-01

    Determination of photosynthetic production in plant communities is essential for evaluating plant growth rates and carbon fluxes in ecosystems, but it cannot easily be derived from the photosynthetic response of individual leaves or thalli, which has been the focus of virtually all previous aquatic...... studies. To evaluate the regulation of aquatic community production, we measured the photosynthetic production of thallus parts and entire communities of Fucus serratus (L.) of different density and spatial structure exposed to varying photon flux density and dissolved CO2 concentration. Photosynthetic...... production in relation to photon flux density differed considerably between entire communities and individual thallus parts. No light saturation occurred in the communities, and all photosynthetic variables such as light compensation point, efficiency of light utilisation at low light and maximum production...

  8. The Structure of Psychopathology in a Community Sample of Preschoolers

    Science.gov (United States)

    Strickland, Jennifer; Keller, Jennifer; Lavigne, John V.; Gouze, Karen; Hopkins, Joyce; LeBailly, Susan

    2011-01-01

    Despite growing interest in the development of alternative diagnostic classification systems for psychopathology in young children, little is known about the adequacy of the DSM symptom structure for describing psychopathology in this population. This paper examines the fit of the DSM-IV emotional (ED) and disruptive behavior disorder (DD) symptom…

  9. Locating Elementary Teachers' Professional Communities in a Structured Collaboration Environment

    Science.gov (United States)

    Chu, Szu Yang

    2016-01-01

    As teacher collaboration becomes an increasingly common goal in school organization, teachers' experiences and perspectives in a Structured Collaboration Environment remain under-examined. This qualitative case study explored how teachers participated in collaborative work, the outcomes of collaboration, and supports and obstacles to productive…

  10. School Structures: Transforming Urban Complex Schools into Better Learning Communities

    Science.gov (United States)

    Haimendorf, Max; Kestner, Jacob

    2008-01-01

    This article, which forms part of the policy booklet "Lessons from the Front" written by participants and Ambassadors of the Teach First scheme, argues that educational outcomes are often adversely affected by the size and structure of many urban complex schools. Rather than multiplying the efforts of teachers, too often the organisational model…

  11. A Novel Top-k Strategy for Influence Maximization in Complex Networks with Community Structure.

    Directory of Open Access Journals (Sweden)

    Jia-Lin He

    Full Text Available In complex networks, it is of great theoretical and practical significance to identify a set of critical spreaders which help to control the spreading process. Some classic methods are proposed to identify multiple spreaders. However, they sometimes have limitations for the networks with community structure because many chosen spreaders may be clustered in a community. In this paper, we suggest a novel method to identify multiple spreaders from communities in a balanced way. The network is first divided into a great many super nodes and then k spreaders are selected from these super nodes. Experimental results on real and synthetic networks with community structure show that our method outperforms the classic methods for degree centrality, k-core and ClusterRank in most cases.

  12. Finding Community Structure in Networks Using a Shortest-Path-Based k-Means Algorithm

    Institute of Scientific and Technical Information of China (English)

    Jinglu GAO

    2013-01-01

    We consider the problem of detecting the community structure in a complex network,groups of nodes with a higher-than-average density of edges connecting them.In this paper we use the simulated annealing strategy to maximize the modularity,which has been indicated as a robust benefit function,associating with a shortest-path-based k-means iterative procedure for network partition.The proposed algorithm can not only find the communities,but also identify the nodes which occupy central positions under the metric of the shortest path within the communities to which they belong.The optimal number of communities can be automatically determined without any prior knowledge about the network structure.The applications to both artificial and real-world networks demonstrate the effectiveness of our algorithm.

  13. Meiobenthic and Macrobenthic Community Structure in Carbonate Sediments of Rocas Atoll (North-east, Brazil)

    Science.gov (United States)

    Netto, S. A.; Warwick, R. M.; Attrill, M. J.

    1999-01-01

    Rocas is the only atoll of the South Atlantic and it is built almost exclusively by coralline red algae, vermetid gastropods and encrusting foraminiferans. Patterns in the community structure of meiofauna and macrofauna, particularly nematodes and polychaetes, at Rocas Atoll, north-east Brazil, are determined and compared for different habitats: sublittoral, tidal flat, reef pools and lagoon. Nematodes and copepods were the most abundant meiofaunal taxa. In all studied habitats at Rocas Atoll, oligochaetes, nematodes and polychaetes numerically dominate the macrofauna. Univariate and multivariate analyses reveal clear differences in community structure between the habitats of the atoll, especially between the sublittoral and the inner habitats. The number of species, total density, diversity (H') and trophic structure vary significantly between the habitats, but the differences are dependent on which faunistic category (meiobenthic or macrobenthic) is analysed. Nematodes belonging to the Epsilonematidae and Draconematidae, together with a diverse community of meiobenthic polychaetes, characterize the sublittoral habitat of Rocas Atoll. Both meiofauna and macrofauna are depressed in the tidal flat, and the local sediment instability particularly affects the polychaete abundance. Reef pools and lagoons support a very dense aggregation of invertebrates, particularly the macrofauna, when compared with other carbonate reef sediments. However, differences in the structure of meiofauna and macrofauna communities between reef pools and lagoons are not significant. Changes in meiobenthic and macrobenthic community structure are related to the gradation in the physical environment of the atoll.

  14. Soil resources and topography shape local tree community structure in tropical forests.

    Science.gov (United States)

    Baldeck, Claire A; Harms, Kyle E; Yavitt, Joseph B; John, Robert; Turner, Benjamin L; Valencia, Renato; Navarrete, Hugo; Davies, Stuart J; Chuyong, George B; Kenfack, David; Thomas, Duncan W; Madawala, Sumedha; Gunatilleke, Nimal; Gunatilleke, Savitri; Bunyavejchewin, Sarayudh; Kiratiprayoon, Somboon; Yaacob, Adzmi; Supardi, Mohd N Nur; Dalling, James W

    2013-02-22

    Both habitat filtering and dispersal limitation influence the compositional structure of forest communities, but previous studies examining the relative contributions of these processes with variation partitioning have primarily used topography to represent the influence of the environment. Here, we bring together data on both topography and soil resource variation within eight large (24-50 ha) tropical forest plots, and use variation partitioning to decompose community compositional variation into fractions explained by spatial, soil resource and topographic variables. Both soil resources and topography account for significant and approximately equal variation in tree community composition (9-34% and 5-29%, respectively), and all environmental variables together explain 13-39% of compositional variation within a plot. A large fraction of variation (19-37%) was spatially structured, yet unexplained by the environment, suggesting an important role for dispersal processes and unmeasured environmental variables. For the majority of sites, adding soil resource variables to topography nearly doubled the inferred role of habitat filtering, accounting for variation in compositional structure that would previously have been attributable to dispersal. Our results, illustrated using a new graphical depiction of community structure within these plots, demonstrate the importance of small-scale environmental variation in shaping local community structure in diverse tropical forests around the globe.

  15. Temporal change in biological community structure in the Fountain Creek basin, Colorado, 2001-2008

    Science.gov (United States)

    Zuellig, Robert E.; Bruce, James F.; Stogner, Robert W.

    2010-01-01

    In 2001, the U.S. Geological Survey, in cooperation with Colorado Springs City Engineering, began a study to better understand the relations between environmental characteristics and biological communities in the Fountain Creek basin in order to aide water-resource management and guide future monitoring activities. To accomplish this task, environmental (streamflow, habitat, and water chemistry) and biological (fish and macroinvertebrate) data were collected annually at 24 sites over a 6- or 8-year period (fish, 2003 to 2008; macroinvertebrates, 2001 to 2008). For this report, these data were first analyzed to determine the presence of temporal change in macroinvertebrate and fish community structure among years using nonparametric multivariate statistics. Where temporal change in the biological communities was found, these data were further analyzed using additional nonparametric multivariate techniques to determine which subset of selected streamflow, habitat, or water-chemistry variables best described site-specific changes in community structure relative to a gradient of urbanization. This study identified significant directional patterns of temporal change in macroinvertebrate and fish community structure at 15 of 24 sites in the Fountain Creek basin. At four of these sites, changes in environmental variables were significantly correlated with the concurrent temporal change identified in macroinvertebrate and fish community structure (Monument Creek above Woodmen Road at Colorado Springs, Colo.; Monument Creek at Bijou Street at Colorado Springs, Colo.; Bear Creek near Colorado Springs, Colo.; Fountain Creek at Security, Colo.). Combinations of environmental variables describing directional temporal change in the biota appeared to be site specific as no single variable dominated the results; however, substrate composition variables (percent substrate composition composed of sand, gravel, or cobble) collectively were present in 80 percent of the environmental

  16. Climate-related differences in the dominance of submerged macrophytes in shallow lakes

    NARCIS (Netherlands)

    Kosten, S.; Kamarainen, A.; Jeppesen, E.; Nes, van E.H.; Peeters, E.T.H.M.; Lacerot, G.; Scheffer, M.

    2009-01-01

    It has been suggested that shallow lakes in warm climates have a higher probability of being turbid, rather than macrophyte dominated, compared with lakes in cooler climates, but little field evidence exists to evaluate this hypothesis. We analyzed data from 782 lake years in different climate zones

  17. Ambiguous climate impacts on the competition between submerged macrophytes and phytoplankton in shallow lakes

    NARCIS (Netherlands)

    Kosten, S.; Jeppesen, E.; Huszar, V.M.; Mazzeo, N.; Nes, van E.H.; Peeters, E.T.H.M.; Scheffer, M.

    2011-01-01

    1. Shallow lakes may switch from a state dominated by submerged macrophytes to a phytoplankton-dominated state when a critical nutrient concentration is exceeded. We explore how climate change may affect this critical nutrient concentration by linking a graphical model to data from 83 lakes along a

  18. Ecotypic differentiation in thermal traits in the tropical to warm-temperate green macrophyte Valonia utricularis

    NARCIS (Netherlands)

    Eggert, A.; Burger, E.M.; Breeman, Arno

    2003-01-01

    Differentiation of thermal traits (i.e. growth, survival and reproduction) was studied in the green macrophyte Valonia utricularis (Roth) C. Agardh, which has a world-wide tropical to warm-temperate distribution. Ecotypic differentiation between northeast Atlantic/Mediterranean and Indo-west Pacific

  19. Mowing Submerged Macrophytes in Shallow Lakes with Alternative Stable States: Battling the Good Guys?

    NARCIS (Netherlands)

    Kuiper, Jan J.; Verhofstad, Michiel J. J. M.; Louwers, Evelien; Bakker, Elisabeth S.; Brederveld, Robert J.; van Gerven, Luuk P. A.; Janssen, Annette B. G.; de Klein, Jeroen J. M.; Mooij, Wolf M.

    2017-01-01

    Submerged macrophytes play an important role in maintaining good water quality in shallow lakes. Yet extensive stands easily interfere with various services provided by these lakes, and harvesting is increasingly applied as a management measure. Because shallow lakes may possess alternative stable

  20. Effects of contrasting omnivorous fish on submerged macrophyte biomass in temperate lakes: a mesocosm experiment

    NARCIS (Netherlands)

    Dorenbosch, M.; Bakker, E.S.

    2012-01-01

    1.Freshwater fish can affect aquatic vegetation directly by consuming macrophytes or indirectly by changing water quality. However, most fish in the temperate climate zone have an omnivorous diet. The impact of fish as aquatic herbivores in temperate climates therefore remains unclear and depends on