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Phytoplankton biomass and production in the northern Gulf of California
No full textEl norte del Golfo de California (NGC) es una de las regiones más productivas del golfo. Su alta producción fitoplanctónica (PP) sustenta una gran diversidad biológica y pesquerías con capturas elevadas. En la parte noroccidental del NGC se encuentra el hábitat de la vaquita (Phocoena sinus), el cetáceo con el mayor peligro de extinción en el mundo debido a que su población es muy pequeña (pocos cientos de individuos). El objetivo de este estudio es demostrar que el NGC se ha mantenido como un sistema sano en el nivel de los productores primarios a pesar de la posible falta del aporte de nutrientes por el Río Colorado y que el tamaño pequeño de la población de la vaquita no se debe al colapso de su ecosistema pelágico. Con el propósito de explorar la posibilidad de una tendencia negativa de la biomasa y producción fitoplanctónicas en el NGC en las últimas décadas (~los últimos 35 años) se utilizó información generada por sensores orbitando en satélites (CZCS, SeaWIFS y MODIS-Aqua). Se analizó la variación temporal y espacial de la temperatura superficial del mar (TSMsat), la concentración de clorofila (Chlsat) y PP obtenida como productor estándar de la página web Ocean Productivity de Oregon State University. Se generaron series de tiempo para cuatro cuadrantes relativamente costeros en el NGC, dos en la parte occidental y dos en la parte oriental. El cuadrante noroccidental abarca aproximadamente el hábitat de la vaquita. La Chlsat y PP presentaron valores más altos en el cuadrante noroccidental que en el resto de los cuadrantes en la época de “invierno”, y más claramente en verano. Esto puede deberse al efecto de advección de aguas turbias del Alto Golfo hacia el cuadrante NW que generan una sobreestimación de la Chlsat por el contenido tan alto de detritus y materia orgánica disuelta de color (CDOM). Se presentaron cambios interanuales de Chlsat y PP debido al impacto de la secuencia de eventos ENSO en la región. Sin embargo, la variación estacional fue la dominante en las cuatro localidades. Los máximos de TSMsat se presentaron en agosto y septiembre (30-31°C) y los mínimos en enero y febrero (16-17 °C). Los máximos de Chlsat y PP se presentaron en marzo y abril (2-3 mg m-3, 2-3 g C m-2 día-1) y los mínimos en agosto y septiembre (0.2-0.9 mg m-3, 0.5-1.1 g C m-2 día-1). Estos valores de Chlsat y PP indican que el ecosistema pelágico del NGC es muy productivo con condiciones mesotróficas en “verano” y eutróficas en “invierno”.The northern Gulf of California (NGC) is one of the most productive regions of the gulf. Its high phytoplankton production (PP) supports a great biodiversity and fisheries with high yields. The habitat of the vaquita (Phocoena sinus), the cetacean with the highest risk of extinction in the world because of its very small population (few hundred individuals) is located in the northwestern part of the NGC. The objective of this study is to demonstrate that the NGC has remained as a healthy system at the level of primary producers in spite of the lack of input of freshwater and its nutrients from the Colorado River, and that the small size of the vaquita population is not due to the collapse of its pelagic ecosystem. With the objective of exploring the possibility of a negative tendency of phytoplankton biomass and production in the NGC during the latest decades (i.e., ~the last 35 years) information derived from remote sensors orbiting on satellites was used (CZCS, SeaWIFS and MODIS-Aqua). Temporal and spatial variation of sea surface temperature (TSMsat), chlorophyll concentration (Chlsat) and PP (obtained as standar product from website Ocean Productivity of Oregon State University) were analyzed. Times series for four coastal quadrants were generated, two in the western part and two in the eastern part of the NGC. The northwestern (NW) quadrant covers the vaquita habitat. The NW quadrant had higher Chlsat and PP values than the others in winter and especially in the summer. This may be due to the effect of advection of Upper Gulf turbid waters into the NW quadrant, generating an overestimation of Chlsat because the high concentration of detritus and colored dissolved organic matter (CDOM). Interannual changes of Chlsat and PP occurred because of the impact of the sequence of ENSO events in the region. However, the seasonal variation was dominant in the whole region. Maxima TSMsat occurred in August and September (30 - 31 °C) and minima in January and February (16 - 17 °C). Highest Chlsat and PP were recorded in March and April (2-3 mg m-3, 2-3 g C m-2 day-1) and minima in August and September (0.2-0.9 mg m-3, 0.5-1.1 g C m-2 day-1). These values indicate that the pelagic ecosystem of the NGC is very productive with mesotrophic in “summer” and eutrophic in “winter” conditions
Nutrient input from the Colorado River to the northern Gulf of California is not required to maintain a productive pelagic ecosystem
Get PDF"La alta producción fitoplanctónica (PF) del norte del golfo de California (NGC) sustenta una gran biodiversidad y pesquerías con capturas elevadas. El NGC es el hábitat de la vaquita (Phocoena sinus), el cetáceo que se encuentra en mayor peligro de extinción en el mundo. El objetivo de este estudio es demostrar que el NGC es un sistema sano en el ámbito de los productores primarios a pesar de la falta del aporte de nutrientes del río Colorado, y que el tamaño pequeño de la población de la vaquita no se debe al colapso de su ecosistema pelágico. Se utilizó información satelital (CZCS, SeaWiFS y Aqua-MODIS) con el propósito de explorar la posibilidad de una tendencia negativa de la biomasa y producción fitoplanctónicas en el NGC en los últimos ~35 años. Se analizó la variación espaciotemporal de la temperatura superficial del mar (TSMsat), la concentración de clorofila (Chlsat) y PF. Se generaron series de tiempo para cuatro cuadrantes, dos en la parte occidental y dos en la parte oriental del NGC. El cuadrante noroccidental abarca el hábitat de la vaquita y presentó valores de Chlsat y PF más altos que el resto de los cuadrantes. Esto puede deberse a la advección de aguas turbias del Alto Golfo hacia el cuadrante noroccidental. Se observaron cambios semianuales e interanuales de Chlsat y PF, pero los estacionales fueron dominantes en las cuatro localidades. Los máximos de TSMsat se registraron en agosto y septiembre (30–31 ºC) y los mínimos en enero y febrero (16–17 ºC). Los máximos de Chlsat y PF se registraron en marzo y abril (2–3 mg m–3, 2–3 g C m–2 día–1, respectivamente) y los mínimos en agosto y septiembre (0.2–0.9 mg m–3, 0.5–1.1 g C m–2 día–1, respectivamente). Estos valores de Chlsat y PF indican que el NGC es muy productivo (mesotrófico en verano-otoño y eutrófico en invierno-primavera).""The high phytoplankton production (PP) of the northern Gulf of California (NGC) supports a rich biodiversity and fisheries with high yields. The NGC is the habitat of the vaquita (Phocoena sinus), the cetacean most at risk of extinction in the world. The objective of this study is to demonstrate that the NGC is a healthy system at the level of primary producers despite the lack of nutrient input from the Colorado River, and that the small size of the vaquita population is not attributable the collapse of its pelagic ecosystem. Information derived from satellite sensors (CZCS, SeaWiFS, and Aqua-MODIS) was used to explore the possibility of a negative tendency in phytoplankton biomass and PP in the NGC during the last ~35 years. Temporal and spatial variations in sea surface temperature (SSTsat), chlorophyll concentration (Chlsat), and PP were analyzed. Times series were generated for four coastal quadrants, two in the western part and two in the eastern part of the NGC. The NW quadrant covers the vaquita habitat, and it had higher Chlsat and PP values than the others. This may be due to advection of turbid Upper Gulf waters into the NW quadrant. Semiannual and interannual changes in Chlsat and PP occurred, but the seasonal signal was dominant in the whole region. SSTsat maxima occurred in August and September (30–31 ºC) and minima in January and February (16–17 ºC). Chlsat and PP maxima were recorded in March and April (2–3 mg m-3, 2–3 g C m–2 day–1, respectively) and minima in August and September (0.2–0.9 mg m–3, 0.5–1.1 g C m–2 day–1, respectively). These values indicate that the pelagic ecosystem of the NGC is very productive (mesotrophic in summer-autumn and eutrophic in winter-spring).
Distribución y abundancia de cetáceos en aguas mexicanas del golfo de México
No full textThere are 21 species of cetaceans in the Gulf of Mexico: one baleen whale and 20 odontocetes (toothed whales). Most of the knowledge about this group comes from the U.S. Exclusive Economic Zone; in contrast, their ecology has been poorly studied in the Mexican waters. This lack of basic information limits the assessments of the population status of cetacean in the Gulf of Mexico. The main objective of this study was to create a baseline on the distribution and abundance of cetaceans in Mexican waters of the Gulf of Mexico. First, the current knowledge on cetaceans was determined, conducting a bibliographic search of historical records of sightings and strandings, and another search one on peer-review papers to identify the most studied species and subjects. Records of 16 species of cetaceans were compiled in Mexican waters of the Gulf, adding four species than those previously reported, and 90% of these records were common bottlenose dolphins. Moreover, in Mexico a substantial delay was found in relation to the studies made in the U.S. waters. Likewise, the common bottlenose dolphin has been the most studied species in the Gulf of Mexico. Secondly, the habitat suitability of 12 species was modeled using the maximum entropy algorithm (MaxEnt), and a spatial approach was used to identify those geographic regions capable of supporting a high diversity of cetaceans. Overall, depth, minimum sea surface temperature, and bottom slope were the most contributing predictors in the models. Similarly, high suitability areas of 10 species were located on the continental slope, and four suitable regions were identified: (1) the Mississippi Canyon and the Louisiana-Texas slope in the northern Gulf, (2) the west Florida slope in the east-northeastern, (3) the Rio Grande slope in the west-northwestern, and (4) Tamaulipas-Veracruz in the west-southwestern. Finally, the population density and abundance of delphinids was estimated in the southwestern Gulf of Mexico. Four aerial surveys were conducted between August 2015 and February 2017, using distance sampling protocols, and the data were analyzed using hierarchical Bayesian approach. Delphinids abundance in the southwestern Gulf of Mexico was in the order of the hundreds of animals (N= 668; 95 %-CI: 340 – 1,179), with a global density of 1.91 individuals 100 km-2 (95 %-CI: 0.97 – 3.38). The results reported are a first approximation to understand the distribution and abundance of cetaceans in Mexican waters of the Gulf...En el golfo de México hay 21 especies de cetáceos: un misticeto (ballenas barbadas) y 20 odontocetos (cetáceos dentados). La mayor parte del conocimiento sobre este grupo proviene de la Zona Económica Exclusiva de Estados Unidos; en contraste, su ecología ha sido poco estudiada en las aguas mexicanas. Esta falta de información básica limita la evaluación del estado de sus poblaciones en el golfo de México. El objetivo principal de este trabajo fue crear la línea de base sobre la distribución y abundancia de los cetáceos en aguas mexicanas del golfo de México. En primer lugar, se determinó el estado actual del conocimiento de los cetáceos en aguas mexicanas, para lo cual se hizo una búsqueda bibliográfica de los registros históricos de avistamientos y varamientos, y otra sobre publicaciones científicas para conocer cuáles son las especies y temáticas más estudiadas. Se recopilaron registros de 16 especies de cetáceos en aguas mexicanas del golfo, añadiéndose cuatro especies a las reportadas previamente, y 91% de estos registros fueron tursiones. Además, se encontró que en México existe un retraso importante en relación a los estudios hechos en aguas de Estados Unidos. Asimismo, se encontró que el tursión ha sido la especie más estudiada en el golfo de México. En segundo lugar, se modeló la idoneidad ambiental de 12 especies de cetáceos, para lo cual se utilizó el algoritmo de máxima entropía (MaxEnt) y para identificar aquellas regiones geográficas capaces de soportar una alta diversidad de cetáceos se utilizó un enfoque espacial. En general, la profundidad, la temperatura mínima de la superficie del mar y la pendiente del fondo fueron los predictores que más contribuyeron a los modelos. Igualmente, se encontró que áreas de alta idoneidad para 10 especies se localizaron en el talud continental y se identificaron cuatro regiones idóneas: (1) el cañón del Mississippi y el talud de Luisiana-Texas en el norte del golfo, (2) la terraza occidental de Florida en el este-noreste, (3) el talud del Río Bravo en el oeste-noroeste, y (4) el talud de Tamaulipas-Veracruz en el oeste-suroeste. Finalmente, se estimó la densidad poblacional y abundancia de delfínidos en el suroeste del golfo. Cuatro muestreos aéreos se llevaron a cabo entre agosto 2015 y febrero 2017, utilizando protocolos de muestreo de distancias y los datos se analizaron mediante un modelo jerárquico bayesiano. Se encontró que la abundancia de los delfínidos en el suroeste del golfo de México estuvo ..
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
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