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Colección de artículos en temáticas antárticas publicados por investigadores de la Universidad de Magallanes en diferentes fuentes, acorde a las políticas del editor.
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Browsing Artículos by Subject "Antarctic Circumpolar Current"
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Item Divergence time estimations and contrasting patterns of genetic diversity between antarctic and southern south america benthic invertebrates(Sociedad de Biología de Chile, 2012) González-Wevar, Claudio Alejandro; Díaz, Angie; Gerard, Karin; Poulin, Elie; Cañete, Juan I.Diversity, abundance and composition of taxonomic groups in the Southern Ocean differ from elsewhere in the planet, since the biogeography in this region refl ects the complex interactions of tectonics, oceanography, climate and biological elements since the Eocene. Several groups of marine benthic organisms exhibit high levels of genetic divergence among provinces in this region, supporting the existence of a vicariance process through plate tectonics, while other groups with high dispersive capacity exhibit recent divergence processes. Moreover, the discovery of non- Antarctic decapod larvae in Antarctic Peninsula suggests that some groups can travel across the Antarctic Circumpolar Current. Here we analyzed levels of genetic divergence in congeneric species of three Southern Ocean’s benthic invertebrate groups with dispersive potential. For this purpose we included in the analyses COI sequences of an echinoid (Sterechinus), a gastropod (Nacella), and a bivalve (Yoldia). Considering the levels of genetic differentiation and assuming the molecular clock hypothesis we estimated the separation of invertebrates from the two continents. We also compared levels of genetic variation between Antarctic and sub-Antarctic species of Nacella and Sterechinus to determine the effect of the Quaternary glacial episodes in the demography of these species. We detected clear genetic differences between Antarctic and sub-Antarctic congeneric species of Sterechinus, Nacella, and Yoldia. According to our results, the installation of an effective barrier between Antarctica and sub-Antarctica occurred almost at the same time (between 3.7 and 5.0 Ma) for these groups of organisms, long after the physical separation of both continents. Genetic comparisons between Antarctic and Sub-Antarctic species of Nacella and Sterechinus detected lower levels of genetic diversity in Antarctic species, suggesting more pronounced effects of the glacial episodes in Antarctica than in South America. These results may refl ect the dramatic effect of the Quaternary glacial cycles on Antarctic population sizes, especially in groups with narrow bathymetric ranges. The present study provides new evidence about the differentiation processes between Antarctic and South American organisms. None of the analyzed genera showed evidence for recurrent gene fl ow across the Antarctic Circumpolar Current since the Mio-Pliocene. Genetic comparisons indicate that Antarctic and Sub-Antarctic species were differentially affected by glacial periods.Item Glacial reduction and millennial-scale variations in Drake Passage throughflow(National Academy of Sciences, 2015-11-03) Lamy, Frank; Arz, Helge W.; Kilian, Rolf; Lange, Carina B.; Lembke-Jene, Lester; Wengler, Marc; Kaiser, Jerôme; Baeza-Urrea, Oscar; Hall, Ian R.; Harada, Naomi; Tiedemann, Ralf; Thiemens, Mark H.The Drake Passage (DP) is the major geographic constriction for the Antarctic Circumpolar Current (ACC) and exerts a strong control on the exchange of physical, chemical, and biological properties between the Atlantic, Pacific, and Indian Ocean basins. Resolving changes in the flow of circumpolar water masses through this gateway is, therefore, crucial for advancing our understanding of the Southern Ocean’s role in global ocean and climate variability. Here, we reconstruct changes in DP throughflow dynamics over the past 65,000 y based on grain size and geochemical properties of sediment records from the southernmost continental margin of South America. Combined with published sediment records from the Scotia Sea, we argue for a considerable total reduction of DP transport and reveal an up to ∼40% decrease in flow speed along the northernmost ACC pathway entering the DP during glacial times. Superimposed on this long-term decrease are high-amplitude, millennial- scale variations, which parallel Southern Ocean and Antarctic temperature patterns. The glacial intervals of strong weakening of the ACC entering the DP imply an enhanced export of northern ACC surface and intermediate waters into the South Pacific Gyre and reduced Pacific–Atlantic exchange through the DP (“cold water route”). We conclude that changes in DP throughflow play a critical role for the global meridional overturning circulation and interbasin exchange in the Southern Ocean, most likely regulated by variations in the westerly wind field and changes in Antarctic sea ice extent.Item Patrones de diversidad y estructura genética en especies antárticas y subantárticas de Nacella (Nacellidae)(Universidad de Magallanes, 2016) González-Wevar, Claudio A.; Hüne, Mathias; Rosenfeld, Sebastián; Gérard, Karin; Mansilla, Andrés; Poulin, ElieLa biogeografía del Océano Austral es el resultado de la compleja interacción de distintas fuerzas macroevolutivas sobre su particular biota en el tiempo y en el espacio. Los procesos de tectónica de placas que derivaron en la separación de los continentes junto al establecimiento de la Corriente Circumpolar Antártica y el enfriamiento paulatino de la región desde el Eoceno se han asociado directamente a la composición, abundancia y distribución de su fauna marina bentónica. Más recientemente, los procesos glaciales del Cuaternario impactaron fuertemente la distribución de la variación genética intraespecífica en una variedad de taxones. El género Nacella (Patellogastropoda: Nacellidae) incluye 11 especies nominales que se distribuyen en distintas provincias del Océano Austral. En este estudio se compararon los patrones de diversidad y estructura genética a nivel del DNA mitocondrial de cuatro especies de Nacella provenientes de Antártica marítima (Nacella concinna), Sudamérica (Nacella magellanica) y de dos islas ubicadas en el sector Índico del Océano Austral: Kerguelén (Nacella edgari) y Marión (Nacella delesserti). Bajos niveles de diversidad genética y ausencia de estructura caracterizan a cada una de las especies analizadas lo que muestra el tremendo impacto del avance y retroceso de los hielos sobre la demografía de todas ellas. Baja diversidad haplotípica, genealogías cortas y las demografías específicas sugieren la ocurrencia de efectos poblacionales más severos en Antártica marítima e Isla Marión que en el resto de las regiones subantárticas.