Incidencia de la mecanización agraria en la estructura comercial local entrerriana. La Ferretería "Irigoyen" de Gualeguaychú, 1953-1960

Este trabajo de investigación estudia la incidencia en la estructura comercial que produce la mecanización del campo, impulsada desde el gobierno nacional en la mitad del siglo XX. Las demandas de los productores de la zona de Gualeguaychú, Entre Ríos, provocan el esfuerzo del comercio local por satisfacerlas. Muestra clara de este proceso es el desenvolvimiento desarrollado por la firma "Ferretería Irigoyen", debiendo adaptarse a los nuevos tiempos. El análisis de la documentación del comercio, de los diarios locales y del testimonio oral, nos permite reflejar el impacto que causó la transformación agropecuaria en la estructura comercial de la firma.

La región Río de la Plata y el comercio ultramarino durante las últimas décadas del siglo XVIII : Actores, circulación comercial y mercancías

Fil: Camarda, Maximiliano. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

(Table 1) Egg laying and hatching dates and guarding duration of Adélie penguins (Pygoscelis adeliae) on Petrel Island, Antarctica

1. In Polar Regions, the extent and dynamics of sea-ice are changing. This affects the ocean productivity which consecutively impacts plankton communities and polar top predators like penguins. Yet, the underlying behavioural and physiological mechanisms remain poorly understood. 2. Here we monitored the ecophysiological responses of Adelie penguin (Pygoscelis adeliae) pairs during two seasons of contrasting timing of sea-ice retreat. Beside classical breeding parameters like foraging trip duration, body mass and reproductive success, we also investigated food-related stress (via plasma corticosterone concentration), nutritional state (via metabolite levels) and the use of penguins' habitat (via blood isotopic values). 3. Body mass and reproductive success remained unchanged but foraging trips were shorter when sea-ice retreated earlier. Constant plasma corticosterone concentrations indicated that none of the feeding conditions resulted in a food-related stress. However metabolite levels were lower when sea-ice retreated early, suggesting that the foraging performance and the quality/quantity of food differed. Indeed isotopic ratios indicated that coastal prey like fish contributed more to the penguins' diet when sea-ice retreated prematurely. 4. The early sea-ice retreat was related to higher chlorophyll concentrations, known to favour krill recruitment. Paradoxically, this was not associated to a higher krill contribution in the penguins' diet. We propose that a shift in the phytoplankton quality (rather than quantity), affecting krill recruitment, forced penguins to switch to more available prey like coastal fish. 5. In some Antarctic regions, sea-ice is retreating earlier and earlier. In the present study, even though the timing of sea-ice retreat and the consecutive ocean productivity differed drastically between the 2 years, Adelie penguins were not severely affected because they were able to adjust their at-sea behaviour and thus maintained their body condition and reproductive success unchanged. 6. This suggests that the timing of sea-ice retreat does not represent an important threat to populations of Adelie penguins at least as long as alternative resources are still available and other environmental parameters like winter sea-ice extent are not dramatically altered.