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Dinámica sucesional y ecología trófica de la comunidad perifítica en dos ambientes del sistema lagunar de Yahuarcaca (Amazonas, Colombia)
Get PDFEl presente estudio analiza el proceso de sucesión de la comunidad perifítica en las fracciones bacteriana, algal y de protozoos, durante los períodos hidrológicos contrastantes de aguas bajas y aguas altas en el sistema lagunar de Yahuarcaca, ubicado en la llanura aluvial del río Amazonas (Leticia, Colombia). Cada 12 horas durante tres días consecutivos se colectaron tres láminas de acetato por ambiente (región limnética y entre los macrófitos) y se guardaron directamente en una bolsa Ziploc® abierta justo debajo de la lámina, colectando en su totalidad el material adherido y aquel ligado al sustrato. El proceso de colonización bacteriana para el período de aguas bajas inició a las 12h con valores de 2.98E+06 - 1.84E+06 cel/ml; a las 36 y 48h con 6.36E+06 - 6.16E+06 cel/ml y finalizó con un descenso de 2.57E+06 - 1.32E+06 cel/ml a las 72h. Para el período de aguas altas se presentó un aumento en la densidad de este componente con valores iniciales de 1.55E+07 - 8.54E+06 cel/ml debido al aumento de materia orgánica disponible en el sistema debido al proceso de inundación. En la primera etapa de colonización algal predominaron Encyonema aff. vulgare, Pinnularia acrosphaeria, Eunotia pectinallis, E. arcus, E. aff. transfuga, E. aff. trópico-arcus, Navicula sp y Amphora ovalis, considerados géneros bidimensionales. En la segunda etapa aparecieron Gomphonema affine, G. gracile, Melosira varians y Pinnularia sp; y en la última fase se encontraron especies capaces de mantener una alta tasa de crecimiento en condiciones de baja luminosidad con estructuras de fijación que les permiten levantarse sobre el sustrato para aprovechar mejor los recursos como Fragillaria aff. intermedia, F. aff. ulna, Aulacoseira varians, Oedogonium sp, Ulothix sp y Nostoc sp. En último lugar, para la fracción de protozoos los primeros colonizadores fueron los organismos flagelados, reportados como consumidores de bacterias, algas y detritos. Tan pronto las poblaciones bacterianas alcanzaron altos valores, los ciliados bacteriófagos de vida libre predominaron, posteriormente estos dieron paso a los ciliados fijos (tipo vorticélidos) que consumen material partículado. La temperatura y la conductividad fueron las variables que presentaron mayor relación con la fracción algal, comportamiento inverso de la fracción bacteriana, la cual dominó en las horas iniciales del proceso. Para el caso de los protozoos, el pH fue el factor que más influyó en la presencia y abundancia durante la sucesión, presentando dominancia hacia las horas finales durante los dos períodos hidrológicos. La disminución y aparición de nuevas especies algales hacia las horas finales del proceso de colonización, evidenciaron un cambio en la estructura del perifiton y una completa sucesión de la comunidad en un lapso de 72 horas para este sistema de la Amazonia colombiana. / Abstract. This study analyzes the succession process of the periphytic community in the bacterial, algae and protozoa fractions, during the contrasting hydrologic periods of low and high waters in the Yahuarcaca lagoon system located in the floodplain of the Amazon river (Leticia, Colombia). Every 12 hours, for three consecutive days, three acetate sheets were collected by environment (limnetic region and between macrophytes) stored directly in a Ziploc ® bag open just below the sheet, collecting entirely the material adhered and that bound to the substrate. The process of bacterial colonization for the low water period began at the 12h with values of 2.98E +06 - 1.84E +06 cells / ml at the 36h and 48h with 6.36E +06 - 6.16E +06 cells / ml and ended with a decline of 2.57E +06 - 1.32E +06 cells / ml at the 72 h. For the high-water period there was an increase in the density of this component with initial values of 1.55E +07 - 8.54E +06 cells / ml due to the increase of organic matter available in the system due to the flooding process. In the first stage of algal colonization predominated Encyonema aff. vulgare, Pinnularia acrosphaeria, Eunotia pectinallis, E. arcus, E. aff. transfuga, E. aff. tropic-arcus, Navicula sp and Amphora ovalis, considered bidimensional genres. In the second stage appeared Gomphonema affine, G. gracile, Melosira varians and Pinnularia sp; and in the last phase were found species able to maintain a high growth rate in low light with mounting structures that allow them to rise above the substrate in order to better leverage resources as Fragillaria aff. intermediate, F. aff. ulna, Aulacoseira varians, Oedogonium sp, Ulothix sp and Nostoc sp. Finally, for the fraction of protozoa the first settlers were the flagellated organisms, reported as consumers of bacteria, algae and detritus. As soon bacterial populations reached high values, free-living bacteriophage ciliates predominated, later these were replaced by fixed ciliates (vorticelid type) that consume particulate matter. Temperature and conductivity were the variables that had a close relationship with the algal fraction, inverse behavior of the bacterial fraction, which dominated in the initial hours of the process. For the case of protozoa, the pH was the most influential factor in the occurrence and abundance during succession, showing dominance towards the final hours during the two hydrological periods. The decline and rise of new algal species to the final hours of the colonization process, showed a change in the structure of periphyton and a complete succession of the community over a period of 72 hours for this system of the Colombian Amazon.Maestrí
Análisis de las relaciones tróficas en un lago de inundación de la Amazonia Colombiana
Get PDFTo determine the trophic relationships in a floodplain lake, we studied the Lake Yahuarcaca (Colombian Amazon), two kilometers west of the city of Leticia, which has the characteristics of a floodplain. During the period of low water hydrological developed an intensive survey of all the environmental compartments of the system include: coastal, benthic, and pelagic regions, riparian vegetation and birds. With this data, complementing with literature information, we construct the food web of the system. Seventy seven taxa were found according to his eating habits and were grouped in twenty two trophospecies, corresponding to four trophic levels. Within the topological characteristics of the network we established fourty links, a value of 0.082 connectance, two relationships of omnivory, two cases of cannibalism. A proportion of 23% of basal trophospecies, within which the detritus is included by functional analogy with producers; 59% of intermediate trofoespecies defined as species that are prey and predator in the system, and finally; 18% of top trophospecies, with no predator identified in the system, and are represented by carnivorous birds and some macroinvertebrates. The food web constructed permit to visualize energy relations between the body of water and the surrounding system, while allowing hypotheses about trophic pathways that sustain fish production in the lake Yahuarcaca, highlighting the importance of detritivore path, with few levels has highly efficient trophic flow in lakes of tropical flood.Para determinar las relaciones tróficas en un lago de inundación, se estudió el sistema lagunar de Yahuarcaca (Amazonas colombiano), dos kilómetros al Oeste de la ciudad de Leticia. Este sistema presenta las características de un plano inundable. Durante el período hidrológico de aguas bajas se desarrolló un muestreo intensivo de todos los compartimentos ecológicos del sistema que incluyen: región litoral, bentónica, pelágica, vegetación ribereña y aves, para construir, complementando la información de campo con información secundaria, la red trófica del sistema. Fueron encontrados 77 táxones que de acuerdo con sus hábitos alimenticios fueron agrupados en 22 trofoespecies, correspondientes a cuatro niveles tróficos. Dentro de las características topológicas de la red se establecieron 40 conexiones, un valor de conectancia de 0.082, dos relaciones de omnivoria, dos casos de canibalismo, una proporción de 23% de trofoespecies basales, dentro de las cuales se incluye el detrito por analogía funcional con los productores; 59% de trofoespecies intermedias definidas como especies que tienen presa y depredador en el sistema; y finalmente 18% de trofoespecies tope, que no tienen depredador identificado en el sistema y que están representadas por aves y algunos macroinvertebrados carnívoros. La red trófica construida, permite visualizar relaciones energéticas entre el cuerpo de agua y el sistema circundante, al tiempo que permite sugerir hipótesis sobre las vías tróficas que sostienen la producción pesquera del sistema Yahuarcaca, resaltando la importancia de la vía detritívora que, con pocos niveles tróficos es altamente eficiente en el flujo de energía en lagos de inundación tropicales
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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