The Bransfield Current System
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Along-Shelf Connectivity and Circumpolar Gene Flow in Antarctic
www.nature.com/scientificreports OPEN Along-shelf connectivity and circumpolar gene fow in Antarctic silverfsh (Pleuragramma Received: 16 March 2018 Accepted: 12 November 2018 antarctica) Published: xx xx xxxx Jilda Alicia Caccavo 1, Chiara Papetti1,2, Maj Wetjen3, Rainer Knust4, Julian R. Ashford5 & Lorenzo Zane1,2 The Antarctic silverfsh (Pleuragramma antarctica) is a critically important forage species with a circumpolar distribution and is unique among other notothenioid species for its wholly pelagic life cycle. Previous studies have provided mixed evidence of population structure over regional and circumpolar scales. The aim of the present study was to test the recent population hypothesis for Antarctic silverfsh, which emphasizes the interplay between life history and hydrography in shaping connectivity. A total of 1067 individuals were collected over 25 years from diferent locations on a circumpolar scale. Samples were genotyped at ffteen microsatellites to assess population diferentiation and genetic structuring using clustering methods, F-statistics, and hierarchical analysis of variance. A lack of diferentiation was found between locations connected by the Antarctic Slope Front Current (ASF), indicative of high levels of gene fow. However, gene fow was signifcantly reduced at the South Orkney Islands and the western Antarctic Peninsula where the ASF is absent. This pattern of gene fow emphasized the relevance of large-scale circulation as a mechanism for circumpolar connectivity. Chaotic genetic patchiness characterized population structure over time, with varying patterns of diferentiation observed between years, accompanied by heterogeneous standard length distributions. The present study supports a more nuanced version of the genetic panmixia hypothesis that refects physical-biological interactions over the life history. -
ARTICLE in PRESS + Model
ARTICLE IN PRESS + model YQRES-02696; No. of pages: 11: 4C: 2, 4 Quaternary Research xx (2006) xxx–xxx www.elsevier.com/locate/yqres A high resolution relative paleointensity record from the Gerlache-Boyd paleo-ice stream region, northern Antarctic Peninsula ⁎ Verónica Willmott a,b, Eugene W. Domack b, Miquel Canals a, , Stefanie Brachfeld c a Department of Stratigraphy, Paleontology and Marine Geosciences, University of Barcelona, Barcelona, Spain b Department of Geosciences, Hamilton College, Clinton, NY 13323, USA c Department of Earth and Environmental Studies, Montclair State University, NJ 07043, USA Received 9 August 2005 Abstract Herein we document and interpret an absolute chronological dating attempt using geomagnetic paleointensity data from a post-glacial sediment drape on the western Antarctic Peninsula continental shelf. Our results demonstrate that absolute dating can be established in Holocene Antarctic shelf sediments that lack suitable material for radiocarbon dating. Two jumbo piston cores of 10-m length were collected in the Western Bransfield Basin. The cores preserve a strong, stable remanent magnetization and meet the magnetic mineral assemblage criteria recommended for reliable paleointensity analyses. The relative paleomagnetic intensity records were tuned to published absolute and relative paleomagnetic stacks, which yielded a record of the last ∼8500 years for the post-glacial drape. Four tephra layers associated with documented eruptions of nearby Deception Island have been dated at 3.31, 3.73, 4.44, and 6.86 ± 0.07 ka using the geomagnetic paleointensity method. This study establishes the dual role of geomagnetic paleointensity and tephrochronology in marine sediments across both sides of the northern Antarctic Peninsula. -