Export of algal biomass from the melting Arctic sea ice

In the Arctic, under-ice primary production is limited to summer months and is not only restricted by ice thickness and snow cover but also by the stratification of the water column, which constrains nutrient supply for algal growth. RV Polarstern visited the ice-covered Eastern Central basins between 82 to 89°N and 30 to 130°E in summer 2012 when Arctic sea ice declined to a record minimum. During this cruise, we observed a widespread deposition of ice algal biomass of on average 9 g C per m**2 to the deep-sea floor of the Central Arctic basins. Data from this cruise will contribute to assessing the impact of current climate change on Arctic productivity, biodiversity, and ecological function.

Investigation of knot nests on Ellesmere Island

Knots arrive on Ellesmere Island in late May or early June. At Hazen Camp small flocks were present on 3 June 1966, but the main influx occurred 5 June when many flocks were seen ranging in size from 6 to 60 individuals. The sexes appeared to arrive together, but the manner of pair-formation was not determined. By 7 June pairs were distributed over the tundra with large feeding flocks forming at snowfree wet marshy areas. Most nests were on Dryas-hummocked slopes and tundra, either dry or moist, with some on clay plains and summits in a mixed Dryas and Salix vegetation. A census area of 240 ha supported at least 3 breeding pairs, and possibly 5; the total number of pairs breeding in the Hazen Camp study area was estimated to be about 25 (1.09 pairs/km**2). Egg-laying (4 nests) extended from 15 to 28 June, with 3 of the 4 sets completed between 20 and 23 June. Both sexes incubated, one of the pair more regularly than the other. The song-flight display of the male was performed most frequently during egglaying and incubation. The incubation period of the last egg in one clutch was established as being between 21.5 and 22.4 days. Four nests hatched between 12 and 20 July, and the hatching period of the entire clutch was less than 24 hours. Four of 7 nests (57 %) survived and egg survival (53 %) was low. Families left the nesting area so on after hatching, concentrating at ponds where food was readily available for the young. Both adults attended the young during the pre-fledging period, but the females apparently departed before the young had hedged. Males left once the young could fly and the adult fall migration was complete by early August. Most 01 the young departed belore mid-August. Fall migration is complete by late August or early September. The breeding season appears to be timed to peak load supply for the young. Adult Chironomidae emergence was highest between 3 and 17 July, the period during which most successful nests hatched. The increasing scarcity of adult insects for the young after mid-July was offset by family movements over the tundra and the early departure of half the adult population. Food also seemed to influence the distribution of breeding pairs aver the tundra, restricting them to the general vicinity of marshes, streams, and ponds where food is most available when the young hatch. Territoriality in the Knot appears to be closely associated with the protection of the nest against predators and has at least a local effect in regulating the number of breeding pairs. Plant material was important in the diet of adult Knots throughout the summer and the primary food from the time of arrival until mid-June. After mid-June the percentage of animal matter increased as dipterous insects became available (especially adult Chironomidae), but plant materials continued to constitute a large part of the diet, usually more than 50 %. The food of the young before fledging consisted principally of adult chironomids.

Pulperos y pulperías rurales bonaerenses : Su influencia en la campaña y los pueblos, 1780-1820

En las últimas décadas se ha construido una nueva imagen del mundo rural pampeano que ha complejizado el análisis con nuevos temas, métodos y fuentes. En estos estudios si bien los pulperos y pulperías están presentes siempre figuran de manera lateral o complementaria. En este trabajo me propuse profundizar el estudio de pulperos y pulperías rurales una vez reconocida su influencia en materia económica, política y social tanto en la campaña en su conjunto como hacia el interior de los pueblos. El tema elegido entonces responde a la necesidad de un estudio exclusivo y exhaustivo sobre un grupo que entendemos ha cumplido una función muy relevante como elemento central en la expansión, ocupación y estructuración de la sociedad rural bonaerense al igual que lo fueron las estancias, los fuertes y las parroquias. La expansión y consolidación de la campaña bonaerense ha sido acompañada por el despliegue comercial en las últimas décadas del siglo XVIII. Podemos hablar de un fenómeno de retroalimentación entre comerciantes y explotaciones ganaderas protagonizado con frecuencia por las mismas personas. En este sentido las pulperías contribuyeron a la formación de pueblos, la ocupación de nuevas tierras y el desarrollo de relaciones pacíficas con los pueblos originarios, aunque a veces fueron agentes disruptores. Nos queda claro que las pulperías eran engranajes importantes dentro de la economía local y ubicaban a sus propietarios por encima de la mayoría de los productores. Sin embargo muchos pulperos también eran productores o viceversa y esa diversificación les permitía disminuir los riesgos y las posibilidades de "naufragio". Creemos haber matizado y en algunos casos rechazado algunas de las imágenes literarias que en general configuraron una visión muy negativa de los pulperos y sus negocios. El pulpero no era muy distinto a su clientela y formaba parte de las costumbres predominantes de la campaña más allá de tener, en muchos casos, una posición económica más holgada. En este sentido, muchos pulperos fueron vecinos referentes en sus pueblos cumpliendo distintas funciones más allá de la fundamental que era el abastecimiento de bienes básicos, ocuparon cargos en el andamiaje institucional y se erigieron en la "voz del pueblo". La posición privilegiada de algunos pulperos les permitía evadir el peso de la justicia y cuando ocupaban cargos sacar provecho de ellos. Esto refuerza la idea de connivencia entre comercializadores locales y el aparato institucional local en torno al usufructo del tráfico de cueros que cada vez se hacía más rentable.