Alberto Magno: su figura y su obra II

SCRIPTA MEDIAEVALIA es una publicación periódica, de frecuencia semestral, que reúne trabajos de investigación originales, textos e información sobre el pensamiento medieval. SCRIPTA MEDIAEVALIA integra el Núcleo Básico de Publicaciones Científicas Argentinas y es reseñada e indexada en: International Medieval Bibliography, Repertorio de Medievalismo Hispánico, Medioevo Latino y Latindex. SCRIPTA MEDIAEVALIA integra el Repositorio Bibliográfico de la Universidad Nacional de Cuyo: http://bdigital.uncu.edu.ar/ Este volumen se publica gracias a un subsidio de la Secretaría de Ciencia y Técnica de la Universidad Nacional de Cuyo.

La enseñanza de la literatura española en el CCH de la UNAM

El Colegio de Ciencias y Humanidades de la Universidad Nacional Autónoma de México celebra en 2010 cuarenta años de su creación como proyecto educativo innovador. Las generaciones de estudiantes de sus primeros 25 años -de 1971 a 1996- leyeron a muchísimos autores latinoamericanos y españoles. De los americanos, se identificaron con las letras de García Márquez, Cortázar, Fuentes, Benedetti y Vargas Llosa; de los peninsulares, acogieron con mucha sensibilidad a León Felipe, Antonio Machado, Pedro Salinas, Miguel Hernández y Federico García Lorca, entre otros. Los primeros aún se leen; los segundos desaparecieron de las actividades educativas. La literatura española fue imprescindible no sólo para conformar un bagaje literario de primer nivel en los estudiantes de esos años, sino que su lectura acercó la historia española a los jóvenes mexicanos y, con ello, les inculcó una visión solidaria de pensar la vida. A partir de 1996, cambiaron los programas. Mucho se ha ganado desde entonces en el terreno de la redacción y la comprensión lectora, no obstante, al omitir la literatura española, hemos perdido mucho. El año próximo se reformulará el plan de estudios del CCH y habrá otra oportunidad

La enseñanza de la literatura española en el CCH de la UNAM

El Colegio de Ciencias y Humanidades de la Universidad Nacional Autónoma de México celebra en 2010 cuarenta años de su creación como proyecto educativo innovador. Las generaciones de estudiantes de sus primeros 25 años -de 1971 a 1996- leyeron a muchísimos autores latinoamericanos y españoles. De los americanos, se identificaron con las letras de García Márquez, Cortázar, Fuentes, Benedetti y Vargas Llosa; de los peninsulares, acogieron con mucha sensibilidad a León Felipe, Antonio Machado, Pedro Salinas, Miguel Hernández y Federico García Lorca, entre otros. Los primeros aún se leen; los segundos desaparecieron de las actividades educativas. La literatura española fue imprescindible no sólo para conformar un bagaje literario de primer nivel en los estudiantes de esos años, sino que su lectura acercó la historia española a los jóvenes mexicanos y, con ello, les inculcó una visión solidaria de pensar la vida. A partir de 1996, cambiaron los programas. Mucho se ha ganado desde entonces en el terreno de la redacción y la comprensión lectora, no obstante, al omitir la literatura española, hemos perdido mucho. El año próximo se reformulará el plan de estudios del CCH y habrá otra oportunidad

La enseñanza de la literatura española en el CCH de la UNAM

El Colegio de Ciencias y Humanidades de la Universidad Nacional Autónoma de México celebra en 2010 cuarenta años de su creación como proyecto educativo innovador. Las generaciones de estudiantes de sus primeros 25 años -de 1971 a 1996- leyeron a muchísimos autores latinoamericanos y españoles. De los americanos, se identificaron con las letras de García Márquez, Cortázar, Fuentes, Benedetti y Vargas Llosa; de los peninsulares, acogieron con mucha sensibilidad a León Felipe, Antonio Machado, Pedro Salinas, Miguel Hernández y Federico García Lorca, entre otros. Los primeros aún se leen; los segundos desaparecieron de las actividades educativas. La literatura española fue imprescindible no sólo para conformar un bagaje literario de primer nivel en los estudiantes de esos años, sino que su lectura acercó la historia española a los jóvenes mexicanos y, con ello, les inculcó una visión solidaria de pensar la vida. A partir de 1996, cambiaron los programas. Mucho se ha ganado desde entonces en el terreno de la redacción y la comprensión lectora, no obstante, al omitir la literatura española, hemos perdido mucho. El año próximo se reformulará el plan de estudios del CCH y habrá otra oportunidad

Dolomite-rich coralline algae in reefs resist dissolution in acidified conditions

Coral reef ecosystems develop best in high-flow environments but their fragile frameworks are also vulnerable to high wave energy. Wave-resistant algal rims, predominantly made up of the crustose coralline algae (CCA) Porolithon onkodes and P. pachydermum, are therefore critical structural elements for the survival of many shallow coral reefs. Concerns are growing about the susceptibility of CCA to ocean acidification because CCA Mg-calcite skeletons are more susceptible to dissolution under low pH conditions than coral aragonite skeletons. However, the recent discovery of dolomite (Mg0.5Ca0.5(CO3)), a stable carbonate, in P. onkodes cells necessitates a reappraisal of the impacts of ocean acidification on these CCA. Here we show, using a dissolution experiment, that dried dolomite-rich CCA have 6-10 times lower rates of dissolution than predominantly Mg-calcite CCA in both high-CO2 (~ 700 ppm) and control (~ 380 ppm) environments, respectively. We reveal this stabilizing mechanism to be a combination of reduced porosity due to dolomite infilling and selective dissolution of other carbonate minerals. Physical break-up proceeds by dissolution of Mg-calcite walls until the dolomitized cell eventually drops out intact. Dolomite-rich CCA frameworks are common in shallow coral reefs globally and our results suggest that it is likely that they will continue to provide protection and stability for coral reef frameworks as CO2 rises.

Seawater carbonate chemistry, nutrients and growth rate of coral (Acropora intermedia) and coral-reef seaweed (Lobophora papenfussii) during experiments, 2011

Space competition between corals and seaweeds is an important ecological process underlying coral-reef dynamics. Processes promoting seaweed growth and survival, such as herbivore overfishing and eutrophication, can lead to local reef degradation. Here, we present the case that increasing concentrations of atmospheric CO2 may be an additional process driving a shift from corals to seaweeds on reefs. Coral (Acropora intermedia) mortality in contact with a common coral-reef seaweed (Lobophora papenfussii) increased two- to threefold between background CO2 (400 ppm) and highest level projected for late 21st century (1140 ppm). The strong interaction between CO2 and seaweeds on coral mortality was most likely attributable to a chemical competitive mechanism, as control corals with algal mimics showed no mortality. Our results suggest that coral (Acropora) reefs may become increasingly susceptible to seaweed proliferation under ocean acidification, and processes regulating algal abundance (e.g. herbivory) will play an increasingly important role in maintaining coral abundance.

Seawater carbonate chemistry, nitrogen concentration and macro community analyse, 2011

Rising anthropogenic CO2 emissions acidify the oceans, and cause changes to seawater carbon chemistry. Bacterial biofilm communities reflect environmental disturbances and may rapidly respond to ocean acidification. This study investigates community composition and activity responses to experimental ocean acidification in biofilms from the Australian Great Barrier Reef. Natural biofilms grown on glass slides were exposed for 11 d to four controlled pCO2 concentrations representing the following scenarios: A) pre-industrial (~300 ppm), B) present-day (~400 ppm), C) mid century (~560 ppm) and D) late century (~1140 ppm). Terminal restriction fragment length polymorphism and clone library analyses of 16S rRNA genes revealed CO2-correlated bacterial community shifts between treatments A, B and D. Observed bacterial community shifts were driven by decreases in the relative abundance of Alphaproteobacteria and increases of Flavobacteriales (Bacteroidetes) at increased CO2 concentrations, indicating pH sensitivity of specific bacterial groups. Elevated pCO2 (C + D) shifted biofilm algal communities and significantly increased C and N contents, yet O2 fluxes, measured using in light and dark incubations, remained unchanged. Our findings suggest that bacterial biofilm communities rapidly adapt and reorganize in response to high pCO2 to maintain activity such as oxygen production.

Effects of ocean acidification on population dynamics and community structure of crustose coralline algae

Calcification and growth of crustose coralline algae (CCA) are affected by elevated seawater pCO2 and associated changes in carbonate chemistry. However, the effects of ocean acidification (OA) on population and community-level responses of CCA have barely been investigated. We explored changes in community structure and population dynamics (size structure and reproduction) of CCA in response to OA. Recruited from an experimental flow-through system, CCA settled onto the walls of plastic aquaria and developed under exposure to one of three pCO2 treatments (control [present day, 389±6 ppm CO2], medium [753±11 ppm], and high [1267±19 ppm]). Elevated pCO2 reduced total CCA abundance and affected community structure, in particular the density of the dominant species Pneophyllum sp. and Porolithon onkodes. Meanwhile, the relative abundance of P. onkodes declined from 24% under control CO2 to 8.3% in high CO2 (65% change), while the relative abundance of Pneophyllum sp. remained constant. Population size structure of P. onkodes differed significantly across treatments, with fewer larger individuals under high CO2. In contrast, the population size structure and number of reproductive structures (conceptacles) per crust of Pneophyllum sp. was similar across treatments. The difference in the magnitude of the response of species abundance and population size structure between species may have the potential to induce species composition changes in the future. These results demonstrate that the impacts of OA on key coral reef builders go beyond declines in calcification and growth, and suggest important changes to aspects of population dynamics and community ecology.

Interactions among chronic and acute impacts on coral recruits: the importance of size-escape thresholds

Newly settled recruits typically suffer high mortality from disturbances, but rapid growth reduces their mortality once size-escape thresholds are attained. Ocean acidification (OA) reduces the growth of recruiting benthic invertebrates, yet no direct effects on survivorship have been demonstrated. We tested whether the reduced growth of coral recruits caused by OA would increase their mortality by prolonging their vulnerability to an acute disturbance: fish herbivory on surrounding algal turf. After two months' growth in ambient or elevated CO2 levels, the linear extension and calcification of coral (Acropora millepora) recruits decreased as CO2 partial pressure (pCO2) increased. When recruits were subjected to incidental fish grazing, their mortality was inversely size dependent. However, we also found an additive effect of pCO2 such that recruit mortality was higher under elevated pCO2 irrespective of size. Compared to ambient conditions, coral recruits needed to double their size at the highest pCO2 to escape incidental grazing mortality. This general trend was observed with three groups of predators (blenny, surgeonfish, and parrotfish), although the magnitude of the fish treatment varied among species. Our study demonstrates the importance of size-escape thresholds in early recruit survival and how OA can shift these thresholds, potentially intensifying population bottlenecks in benthic invertebrate recruitment.