Thalassioneis signyensis (bacillariophyceae) from northwest weddell sea icebergs, an emendation of the generic description

We offer an emended description of the genus Thalassioneis based on new observations of the type species, T. signyensis Round, from material sampled in the northwest Weddell Sea. Specimens from algal communities attached to submerged flanks of several icebergs were collected with a remote-operated vehicle (ROV-Phantom DS 2). The analyses were carried out by LM and SEM. Fresh material and frustules without organic matter allowed us to observe details not included in the original description such as type and structure of colonies and chloroplasts. The frustule shows an asymmetry with respect to the location of the apical pore fields, one of them situated on the valvar face and the other one displaced toward the mantle; the former is involved in joining contiguous cells to form long chains. Furthermore, we present details on the ultrastructure of the cingulum that consists of three to four open copulae with one or more rows of poroids. A brief discussion on the habit and ecology of this taxon, which may be endemic to the northwest Weddell Sea, is also presented. A comparison with similar genera, such as Brandinia, Creania, Fossula, Fragilaria, Rimoneis, Synedropsis, and Ulnaria, is included with an evaluation of morphological characteristics useful to differentiate them.Fil: Ferrario, Martha Elba. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Ficología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Cefarelli, Adrián Oscar. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Ficología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Robison, Bruce. Monterey Bay Aquarium Research Institute; Estados UnidosFil: Vernet, María. University of California at San Diego; Estados Unido

Composition and biomass of phytoplankton assemblages in coastal Antarctic waters: A comparison of chemotaxonomic and microscopic analyses

We describe the distribution of phytoplanktonic community composition and biomass from the Western Antarctic Peninsula coast (between 64° and 68° S) using 2 analytical techniques: microscopy and HPLC of photosynthetic pigments. Phytoplankton biomass was estimated as chlorophyll a (chl a) by HPLC and chemotaxonomic quantification of microalgae biomass was performed by multiple regression analysis of pigment concentrations. For the estimation of chl a: diagnostic pigment ratios, it was found of primary importance to differentiate between phytoplankton assemblages within the study area. Three assemblages were differentiated according to their total standing stock and analyzed independently. Phytoplankton biomass was also estimated as carbon (C) concentration by microscopic analysis of cell abundance and biovolumes. Microscopy and chemotaxonomy give a high level of agreement for phytoplankton characterization, showing an on/offshore gradient, with high diatom and cryptophyte biomass in coastal waters, and a mixed assemblage with low biomass in open waters. This gradient was not observed in total cell abundance, indicating that the biomass gradient is controlled by cell size. Microscopy also showed shifts in diatom species throughout the area. C and chl a biomass estimates for the individual microalgae groups were strongly correlated for cryptophytes, chlorophytes and most diatoms, but did poorly for dinoflagellates, prymnesiophytes and chrysophytes. From this study, we conclude that both microscopy and chemotaxonomy can be used to accurately characterize phytoplankton assemblages, but some limitations are present in both techniques. Based on phytoplankton C concentrations, we estimated an average in situ growth rate of 0.28 d-1. In situ cell C:chl a ratios had high variability (from 40 to 220) and were non-linearly related to sample growth rates. Significant differences were found among average C:chl a ratios of low (1 μg chl a l-1), with values of 112 and 74 μg C μg-1 chl a, respectively. In addition, our results support the hypothesis that C quotas of diatoms and other microalgae do not differ greatly from each other, as previously believed.Facultad de Ciencias Naturales y Muse

Composition and biomass of phytoplankton assemblages in coastal Antarctic waters: A comparison of chemotaxonomic and microscopic analyses

We describe the distribution of phytoplanktonic community composition and biomass from the Western Antarctic Peninsula coast (between 64° and 68° S) using 2 analytical techniques: microscopy and HPLC of photosynthetic pigments. Phytoplankton biomass was estimated as chlorophyll a (chl a) by HPLC and chemotaxonomic quantification of microalgae biomass was performed by multiple regression analysis of pigment concentrations. For the estimation of chl a: diagnostic pigment ratios, it was found of primary importance to differentiate between phytoplankton assemblages within the study area. Three assemblages were differentiated according to their total standing stock and analyzed independently. Phytoplankton biomass was also estimated as carbon (C) concentration by microscopic analysis of cell abundance and biovolumes. Microscopy and chemotaxonomy give a high level of agreement for phytoplankton characterization, showing an on/offshore gradient, with high diatom and cryptophyte biomass in coastal waters, and a mixed assemblage with low biomass in open waters. This gradient was not observed in total cell abundance, indicating that the biomass gradient is controlled by cell size. Microscopy also showed shifts in diatom species throughout the area. C and chl a biomass estimates for the individual microalgae groups were strongly correlated for cryptophytes, chlorophytes and most diatoms, but did poorly for dinoflagellates, prymnesiophytes and chrysophytes. From this study, we conclude that both microscopy and chemotaxonomy can be used to accurately characterize phytoplankton assemblages, but some limitations are present in both techniques. Based on phytoplankton C concentrations, we estimated an average in situ growth rate of 0.28 d-1. In situ cell C:chl a ratios had high variability (from 40 to 220) and were non-linearly related to sample growth rates. Significant differences were found among average C:chl a ratios of low (1 μg chl a l-1), with values of 112 and 74 μg C μg-1 chl a, respectively. In addition, our results support the hypothesis that C quotas of diatoms and other microalgae do not differ greatly from each other, as previously believed.Facultad de Ciencias Naturales y Muse

Interannual variability in the distribution of the phytoplankton standing stock across the seasonal sea-ice zone west of the Antarctic Peninsula

The spatial distribution of phytoplankton cell abundance, carbon (C) biomass and chlorophyll a (Chl a) concentration was analysed during three summers (1996, 1997 and 1999) in a seasonal sea-ice area, west of the Antarctic Peninsula. The objective of the study was to assess interannual variability in phytoplankton spatial distribution and the mechanisms that regulate phytoplankton accumulation in the water column. Phytoplankton C biomass and Chl a distributions were consistent from year to year, exhibiting a negative on/offshore gradient. The variations in C concentration had a close and non-linear relationship with the upper mixed layer depth, suggesting that the vertical mixing of the water column is the main factor regulating phytoplankton stock. The magnitude of C gradients was 5-fold higher during 1996 than during 1997 and 1999. This was ascribed to interannual variations in the concentration of diatom blooms in the region influenced by sea-ice melting. Vertical distribution of the phytoplankton, as estimated from Chl a profiles, also varied along an on/offshore gradient: Chl a was distributed homogeneously in the upper mixed layer in coastal and mid-shelf stations and concentrated in the deep layer (40-100 m) occupied by the winter waters (WW, remnants of the Antarctic surface waters during summer) in more offshore stations. The region with a deep Chl a maximum layer (DCM layer) was dominated by a phytoplankton assemblage characterized by a relatively high concentration of diatoms. The extent of this region varied from year to year: it was restricted to pelagic waters during 1996, extended to the shelf slope during 1997 and occupied a major portion of the area during 1999. It is hypothesized that iron depletion in near surface waters due to phytoplankton consumption, and a higher concentration in WW, regulated this vertical phytoplankton distribution pattern. Furthermore, we postulate that year-to-year variations in the spatial distribution of the DCM layer were related to interannual variations in the timing of the sea-ice retreat. The similarity between our results and those reported in literature for other areas of the Southern Ocean allows us to suggest that the mechanisms proposed here as regulating phytoplankton stock in our area may be applicable elsewhere.Facultad de Ciencias Naturales y Muse

Diálogos y reconstrucciones románticas entre Kathleen Raine y William Blake

Kathleen Raine (1908-2003), claramente influida por la poesía de William Blake, ha construido a lo largo del siglo XX su propio corpus poético de la mano de su maestro. La poeta británica no sólo dedicó años de su vida a estudiar la vida y la producción artística de Blake, sino que además adhiere a su concepción de la poesía, construida a partir de la imaginación, el poder divino del poeta. Desde una mirada comparatista, resulta difícil ignorar los puentes trazados por Raine con los ideales románticos, el homenaje a la naturaleza y a la creación. Ecos de dos de las más conocidas "Canciones de Inocencia y de Experiencia" de William Blake, “The Lamb” y “The Tiger” resuenan en la obra de Raine, en especial en “Spell of Creation”, perteneciente al poemario "The Year One" publicado en 1952. Este poema de Raine, además de abordar ejes románticos y recurrir a una estructura rítmica particular, también remite a la revolucionaria teoría de opuestos complementarios (coexistencia de contrarios presentes en la creación), elaborada por Blake, la cual permeó gran parte de su trabajo poético. A partir de la puesta en relación de poemas pertenecientes tanto a Blake como a Raine este artículo intenta señalar las continuidades dialógicas que se establecen en la temática de ellos.Facultad de Humanidades y Ciencias de la Educació

La literatura en las clases de inglés: hacia la producción creativa

La literatura se ha ganado un lugar de privilegio en el proceso de enseñanza-aprendizaje de una segunda lengua. Provee un contexto fantástico desde el cual proponer actividades y tareas que invitan a los alumnos a usar su imaginación y creatividad, a involucrarse personal y activamente en el proceso, a desarrollar sus habilidades de producción oral y escrita. La motivación que despierta la literatura crea una atmósfera de trabajo alegre y libre de tensiones. Es por eso que elegimos acerca material literario a nuestros alumnos una y ora vez. El propósito de nuestro trabajo es presentar algunas experiencias didácticas surgidas de proyectos con el poema “My Robot Does my Homework” y el relato de Alice in Wonderland. Estas han brindado excelentes oportunidades de enriquecer la enseñanza y de disfrutar con el uso creativo de la lengua.Facultad de Humanidades y Ciencias de la Educació

La literatura en las clases de inglés: hacia la producción creativa

La literatura se ha ganado un lugar de privilegio en el proceso de enseñanza-aprendizaje de una segunda lengua. Provee un contexto fantástico desde el cual proponer actividades y tareas que invitan a los alumnos a usar su imaginación y creatividad, a involucrarse personal y activamente en el proceso, a desarrollar sus habilidades de producción oral y escrita. La motivación que despierta la literatura crea una atmósfera de trabajo alegre y libre de tensiones. Es por eso que elegimos acerca material literario a nuestros alumnos una y ora vez. El propósito de nuestro trabajo es presentar algunas experiencias didácticas surgidas de proyectos con el poema “My Robot Does my Homework” y el relato de Alice in Wonderland. Estas han brindado excelentes oportunidades de enriquecer la enseñanza y de disfrutar con el uso creativo de la lengua.Facultad de Humanidades y Ciencias de la Educació

Gamificación: aprender jugando - parte 1

Este mes les proponemos reflexionar acerca del juego en el ámbito educativo y explorar el concepto de gamificación y su potencialidad gracias al empleo de las TICs.Facultad de Humanidades y Ciencias de la Educació

Gamificación: aprender jugando - parte 2

A la hora de planificar una clase gamificada, podemos recurrir a diversas estrategias que pueden ser utilizadas de manera aislada o en conjunto con otras. Entre ellas podemos mencionar: la presencia de metas y objetivos, la narrativa, el otorgamiento de recompensas, la retroalimentación, el estatus visible, las reglas, la restricción de tiempo, los indicadores de progreso y el factor sorpresa, entre otros. Las nuevas tecnologías son excelentes aliados a la hora de poner en práctica estas estrategias. Existe actualmente una amplia gama de aplicaciones a las que podemos recurrir para utilizar distintos ingredientes puntuales propios de los juegos en las clases.Facultad de Humanidades y Ciencias de la Educació