Trabajo intensivo en los umbrales para la alfabetización en Misiones- Parte II. 16H205

La noción de umbral ha sido planteada en etapas anteriores de nuestros trabajos de investigación. Sus definiciones y aplicaciones han sido publicadas y contrastadas en numerosas reuniones de la especialidad. Su formulación, que cubre un amplio espectro de caracteres semióticos y de prácticas socioculturales, se centra en este caso en la crítica transición de los diálogos cotidianos (familiares, vecinales, comunitario) a los diálogos escolares (nivel inicial y educación general básica I), en virtud de las singularidades que presenta en zonas rurales e interculturales en nuestra provincia. El alto porcentaje de población rural, sus migraciones laborales transversales y hacia los asentamientos suburbanos, adquiere para este proyecto una relevancia singular que se articula con las dinámicas interculturales. Los diagnósticos sobre fracaso escolar insisten en señalar dos indicadores agravados en el primer ciclo: deserción y repitencia, configuraciones cuantitativas en las que quedan solapadas las tensiones semióticas de la grave crisis del sistema educativo. La experiencia acumulada en trabajos de campo, diagnósticos, encuestas, entrevistas, cursos de transferencia, contrastes de resultados y propuestas en diversos foros nacionales e internacionales con investigadores de distintas orientaciones, se constituye en la base de sustentación para postular este proyecto de alfabetización intercultural, con miras a obtener una formación específica y adecuada a las necesidades de los niños de la región. La topología del umbral configura una red conceptual estratégica que prolifera en múltiples alternativas para intervenir en la contingencia, a fin de emprender procesos alfabetizadores equilibrados con un instrumental teórico y metodológico basado principalmente en la textualidad de la vida cotidiana.

Seawater carbonate chemistry near the Island of Ischia, Italy, 2008

We present the first study of the effects of ocean acidification on settlement of benthic invertebrates and microfauna. Artificial collectors were placed for 1 month along pH gradients at CO2 vents off Ischia (Tyrrhenian Sea, Italy). Seventy-nine taxa were identified from six main taxonomic groups (foraminiferans, nematodes, polychaetes, molluscs, crustaceans and chaetognaths). Calcareous foraminiferans, serpulid polychaetes, gastropods and bivalves showed highly significant reductions in recruitment to the collectors as pCO2 rose from normal (336-341 ppm, pH 8.09-8.15) to high levels (886-5,148 ppm) causing acidified conditions near the vents (pH 7.08-7.79). Only the syllid polychaete Syllis prolifera had higher abundances at the most acidified station, although a wide range of polychaetes and small crustaceans was able to settle and survive under these conditions. A few taxa (Amphiglena mediterranea, Leptochelia dubia, Caprella acanthifera) were particularly abundant at stations acidified by intermediate amounts of CO2 (pH 7.41-7.99). These results show that increased levels of CO2 can profoundly affect the settlement of a wide range of benthic organisms.

(Table 1) Presence of sublittoral macroalgae in the investigated profiles in Potter Cove, King George Island, Antarctica

The vegetation of a small fjord and its adjacent open shore was documented by subaquatic video. The distribution of individual species of macroalgae and the composition of assemblages were compared with gradients of light availability, hydrography, slope inclination, substratum, and exposition to turbulence and ice. The sublittoral fringe is usually abraded by winterly ice floes and devoid of large, perennial algae. Below this zone, the upper sublittoral is dominated by Desmarestia menziesii on steep rock faces, where water movements become irregular, or by Ascoseira mirabilis and Palmaria decipiens on weakly inclined slopes with steady rolling water movements. In the central sublittoral above 15 m, where turbulence is still active, Desmarestia anceps is outcompeting all other species on solid substratum, However, the species is not able to persist on loose material under these conditions. Instead, Himantothallus grandifolius may occur. Deeper, where turbulence usually is negligible, Desmarestia anceps also covers loose material. The change of dominance to Himantothallus grandifolius in the deep sublittoral cannot completely be explained at present. Himantothallus grandifolius also prevails in a mixed assemblage under the influence of grounding icebergs. Most of the smaller algae are opportunists with different degrees of tolerance for turbulence, but some apparently need more stable microhabitats and thus are dependent from continuing suppression of competitive large phaeophytes.

Succession of benthic hard-bottom communities in the shallow sublitoral of Comau Fjord, Chile

Succession was already studied over decades. The present thesis investigated the succession on hard substrate at two different study sites within the fjord Comau, Chile. Nine plates were installed at both sites (mouth of fjord and inner fjord) and photographed over three years. Additionally the natural community was recorded and a ground truthing was carried out to verify the analyzed species. Respectively at both sites over 50 different species were identified. Abundance data decreased with only one exception continuously, whereas the percentage cover increased. But the communities on the recruitment plates do still not reach the community structure of the natural environment. The present data showed that the hard-bottom succession in the fjord Comau is best described by the TOLERANCE MODEL (Connell & Slatyer, 1977). An important species of the natural community is the stony coral Desmophyllum dianthus, which normally (outside the fjord) grows beneath 1000 m water depth. The results of this work indicate that the mature community is not reached after 36 months.