Source identification and distribution reveals the potential of the geochemical Antarctic sea ice proxy IPSO25

The presence of a di-unsaturated highly branched isoprenoid (HBI) lipid biomarker (diene II) in Southern Ocean sediments has previously been proposed as a proxy measure of palaeo Antarctic sea ice. Here we show that a source of diene II is the sympagic diatom Berkeleya adeliensis Medlin. Furthermore, the propensity for B. adeliensis to flourish in platelet ice is reflected by an offshore downward gradient in diene II concentration in >100 surface sediments from Antarctic coastal and near-coastal environments. Since platelet ice formation is strongly associated with super-cooled freshwater inflow, we further hypothesize that sedimentary diene II provides a potentially sensitive proxy indicator of landfast sea ice influenced by meltwater discharge from nearby glaciers and ice shelves, and re-examination of some previous diene II downcore records supports this hypothesis. The term IPSO25-Ice Proxy for the Southern Ocean with 25 carbon atoms-is proposed as a proxy name for diene II

High contributions of sea ice derived carbon in polar bear (Ursus maritimus) tissue.

Polar bears (Ursus maritimus) rely upon Arctic sea ice as a physical habitat. Consequently, conservation assessments of polar bears identify the ongoing reduction in sea ice to represent a significant threat to their survival. However, the additional role of sea ice as a potential, indirect, source of energy to bears has been overlooked. Here we used the highly branched isoprenoid lipid biomarker-based index (H-Print) approach in combination with quantitative fatty acid signature analysis to show that sympagic (sea ice-associated), rather than pelagic, carbon contributions dominated the marine component of polar bear diet (72-100%; 99% CI, n = 55), irrespective of differences in diet composition. The lowest mean estimates of sympagic carbon were found in Baffin Bay bears, which were also exposed to the most rapidly increasing open water season. Therefore, our data illustrate that for future Arctic ecosystems that are likely to be characterised by reduced sea ice cover, polar bears will not only be impacted by a change in their physical habitat, but also potentially in the supply of energy to the ecosystems upon which they depend. This data represents the first quantifiable baseline that is critical for the assessment of likely ongoing changes in energy supply to Arctic predators as we move into an increasingly uncertain future for polar ecosystems

Pure seminoma: A review and update

Pure seminoma is a rare pathology of the young adult, often discovered in the early stages. Its prognosis is generally excellent and many therapeutic options are available, especially in stage I tumors. High cure rates can be achieved in several ways: standard treatment with radiotherapy is challenged by surveillance and chemotherapy. Toxicity issues and the patients' preferences should be considered when management decisions are made. This paper describes firstly the management of primary seminoma and its nodal involvement and, secondly, the various therapeutic options according to stage

Antiphased dust deposition and productivity in the Antarctic Zone over 1.5 million years

The Southern Ocean paleoceanography provides key insights into how iron fertilization and oceanic productivity developed through Pleistocene ice-ages and their role in influencing the carbon cycle. We report a high-resolution record of dust deposition and ocean productivity for the Antarctic Zone, close to the main dust source, Patagonia. Our deep-ocean records cover the last 1.5 Ma, thus doubling that from Antarctic ice-cores. We find a 5 to 15-fold increase in dust deposition during glacials and a 2 to 5-fold increase in biogenic silica deposition, reflecting higher ocean productivity during interglacials. This antiphasing persisted throughout the last 25 glacial cycles. Dust deposition became more pronounced across the Mid-Pleistocene Transition (MPT) in the Southern Hemisphere, with an abrupt shift suggesting more severe glaciations since ~0.9 Ma. Productivity was intermediate pre-MPT, lowest during the MPT and highest since 0.4 Ma. Generally, glacials experienced extended sea-ice cover, reduced bottom-water export and Weddell Gyre dynamics, which helped lower atmospheric CO2 levels

Polar bear (<i>Ursus maritimus</i>) data.

<p>a) QFASA estimates of marine mammal prey (Bearded seal <i>(Erignathus barbatus</i>), beluga whale (<i>Delphinapterus leucas</i>), harbour seal (<i>Phoca vitulina</i>), harp seal (<i>Pagophilus groenlandicus</i>), ringed seal (<i>Pusa hispida</i>) and walrus (<i>Odobenus rosmarus</i>)) consumed by individual polar bears (stacked coloured bars) and overlaid with H-Prints (black circles) of individual bears. Individual polar bears are grouped according to the geographical location of collection and the corresponding subpopulation designation: Baffin Bay, western Hudson Bay and southern Hudson Bay (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0191631#pone.0191631.g002" target="_blank">Fig 2</a>). For each subpopulation, mean QFASA estimates of marine mammal prey and mean (black circles) and median (grey diamonds) H-Prints are summarised in the single plot adjacent to each subpopulation plot (for H-Print-derived estimates of sympagic carbon, refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0191631#pone.0191631.t001" target="_blank">Table 1</a>). b) δ¹⁵N of individual bears (grey squares). For each subpopulation, mean δ¹⁵N are summarised in the single plot (box and whiskers) adjacent to each subpopulation plot.</p

Geographic setting.

<p>Map of polar bear subpopulations and locations of harvest (red dots) in Baffin Bay (BB), western Hudson Bay (WH) and southern Hudson Bay (SH). Coastlines were created using the Global Self-consistent, Hierarchical, High-resolution Geography database distributed under the GNU Lesser General Public license [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0191631#pone.0191631.ref028" target="_blank">28</a>].</p