Mercury in deep ice-rich permafrost deposits of Siberia. Russian Conference

The late Pleistocene ice-rich Yedoma permafrost is extremely sensitive to Arctic warming. Warming air temperatures, decreasing sea ice extent lead to an increasing degradation of the Yedoma permafrost and thus to a greater sediment input from coastal shorelines and river floodplains to the Laptev Sea. Thus, so far freeze-locked sediments and any potentially hazardous contaminants contained in them are entering Arctic waters and the biological food chain. Shallow (down to <2m) Arctic permafrost soil layers were found to include high levels of mercury (Hg) due to natural enrichment processes of environmentally available Hg (Schuster et al. 2018). However, opposed to seasonal thaw processes of the active layer and long-term gradual thaw through active layer deepening, abrupt thaw processes such as thermokarst, thermo-erosion, and coastal erosion are capable of mobilising permafrost-soils and stored contaminants from tens of meters depth within years to decades. In this study, we determined Hg concentrations from various deposits in Siberia’s deep permafrost sediments. We studied links between sediment properties and Hg enrichment in order to assess a first deep Hg inventory in late Pleistocene permafrost down to 36 m below surface. To do this, we used sediment profiles from seven sites representing different permafrost degradation states on Bykovsky Peninsula (northern Yakutian coast) and in the Yukechi Alas region (Central Yakutia). We analysed 41 samples for Hg content, total carbon, total nitrogen and organic carbon as well as grain size distribution, bulk density and mass specific magnetic susceptibility. Figure 1: (a) geographical overview and detailed location of the study site at Bykovsky Peninsula (b) and Yukechi Alas in Yakutia (c); (d) stratigraphical transect of the study sites and different states of degrading permafrost in Siberia. The numbers indicate the areas of interest in this study. 1) Talik in Yedoma (unfrozen), 2) late Pleistocene Yedoma (frozen), 3) talik in thermokarst (unfrozen), 4) refrozen drained lake basin = Alas (frozen), 5) talik in thermokarst close to sea (unfrozen), 6) talik below seawater flooded thermokarst basins (= lagoons) (unfrozen). We show that the deep sediments (to 30 meter below surface) are characterized by an Hg concentration of 9.72 ± 9.28 μg kg-1 and an correlation of Hg to organic carbon, total nitrogen, grain-size distribution and mass specific magnetic susceptibility. Hg concentrations are higher in the generally sandier sediment of the Bykovsky Peninsula than in the siltier sediment of the Yukechi Alas. In conclusion, we found that the deep permafrost sediments, frozen since tens of millennia, contain sizeable amounts of Hg. Even though the average amount of Hg is with 9.72 μg/kg below levels immediately critical for life and our median is 85 % less (Schuster et al. 2018) than found in Arctic topsoil outside Siberia. Even if the Hg concentrations are not particularly high compared to other sites, the permafrost’s huge spatial coverage results in a significant amount of Hg that can be introduce into nearby aquatic environments and food webs. As the next step, the consequences of old Hg re-entering the active biogeochemical cycles and food webs with ongoing Arctic warming remain unclear and need to be studied in more detail. References 1. Schuster, P. et al. Geophysical Research Letters, 2018, 45, 1463– 1471, https://doi.org/10.1002/2017GL07557

Aquatic community response to volcanic eruptions on the Ecuadorian Andean flank: evidence from the palaeoecological record

Aquatic ecosystems in the tropical Andes are under increasing pressure from human modification of the landscape (deforestation and dams) and climatic change (increase of extreme events and 1.5 °C on average temperatures are projected for AD 2100). However, the resilience of these ecosystems to perturbations is poorly understood. Here we use a multi-proxy palaeoecological approach to assess the response of aquatic ecosystems to a major mechanism for natural disturbance, volcanic ash deposition. Specifically, we present data from two Neotropical lakes located on the eastern Andean flank of Ecuador. Laguna Pindo (1°27.132′S–78°04.847′W) is a tectonically formed closed basin surrounded by a dense mid-elevation forest, whereas Laguna Baños (0°19.328′S–78°09.175′W) is a glacially formed lake with an inflow and outflow in high Andean Páramo grasslands. In each lake we examined the dynamics of chironomids and other aquatic and semi-aquatic organisms to explore the effect of thick (> 5 cm) volcanic deposits on the aquatic communities in these two systems with different catchment features. In both lakes past volcanic ash deposition was evident from four large tephras dated to c.850 cal year BP (Pindo), and 4600, 3600 and 1500 cal year BP (Baños). Examination of the chironomid and aquatic assemblages before and after the ash depositions revealed no shift in composition at Pindo, but a major change at Baños occurred after the last event around 1500 cal year BP. Chironomids at Baños changed from an assemblage dominated by Pseudochironomus and Polypedilum nubifer-type to Cricotopus/Paratrichocladius type-II, and such a dominance lasted for approximately 380 years. We suggest that, despite potential changes in the water chemistry, the major effect on the chironomid community resulted from the thickness of the tephra being deposited, which acted to shallow the water body beyond a depth threshold. Changes in the aquatic flora and fauna at the base of the trophic chain can promote cascade effects that may deteriorate the ecosystem, especially when already influenced by human activities, such as deforestation and dams, which is frequent in the high Andes

Cross-Hemisphere Study Reveals Geographically Ubiquitous, Plastic-Specific Bacteria Emerging from the Rare and Unexplored Biosphere

While it is now appreciated that the millions of tons of plastic pollution travelling through marine systems carry complex communities of microorganisms, it is still unknown to what extent these biofilm communities are specific to the plastic or selected by the surrounding ecosystem. To address this, we characterized and compared the microbial communities of microplastic particles, nonplastic (natural and wax) particles, and the surrounding waters from three marine ecosystems (the Baltic, Sargasso and Mediterranean seas) using high-throughput 16S rRNA gene sequencing. We found that biofilm communities on microplastic and nonplastic particles were highly similar to one another across this broad geographical range. The similar temperature and salinity profiles of the Sargasso and Mediterranean seas, compared to the Baltic Sea, were reflected in the biofilm communities. We identified plastic-specific operational taxonomic units (OTUs) that were not detected on nonplastic particles or in the surrounding waters. Twenty-six of the plastic-specific OTUs were geographically ubiquitous across all sampled locations. These geographically ubiquitous plastic-specific OTUs were mostly low-abundance members of their biofilm communities and often represented uncultured members of marine ecosystems. These results demonstrate the potential for plastics to be a reservoir of rare and understudied microbes, thus warranting further investigations into the dynamics and role of these microbes in marine ecosystems

Compression garments and fabric orthoses for rehabilitation and function: a systematic mapping review.

Background/aims: Compression garments, joint supports and dynamic movement orthoses all use elastic fibres and close-fitting designs and have been researched for their effects on movement. There is little cross-referencing between research into these interventions. This review aimed to improve inter-disciplinary understanding by analysing key characteristics of the published evidence. Methods: Systematic mapping reviews identify gaps in an evidence base and identify questions for more in-depth reviews. This review was conducted in-line with current guidance. MEDLINE, CINAHL and Sports Discuss were searched for primary research investigating compression garments and orthoses for movement and function. The following search terms were used: "elastane", "spandex", "Lycra", "elastomer*", "Theratog*", "compression", "Neoprene", "orthotic", "orthosis", "shorts", "garment*", "splint", "brace", "sock*" and "stockings". Studies were screened against predetermined criteria and key study characteristics extracted. Findings: Three hundred and fifty-one studies were selected and analysed. Compression garment research was most common (236 studies), followed by research into joint supports (64 studies) and dynamic movement orthoses (42 studies). Research largely reflects the purpose for which each intervention was originally designed. Common topics investigated include posture and movement control, proprioception and muscle activity. Pressure beneath compression garments was measured in 30% of studies. Conclusions: The review highlights a need for more robust study designs in patient populations and accurate description of interventions. There is a need for a review on the possible effects of compression and support on movement control which should be used to inform future primary research

Murine Leukemia Virus Spreading in Mice Impaired in the Biogenesis of Secretory Lysosomes and Ca2+-Regulated Exocytosis

Retroviruses have been observed to bud intracellularly into multivesicular bodies (MVB), in addition to the plasma membrane. Release from MVB is thought to occur by Ca(2+)-regulated fusion with the plasma membrane.To address the role of the MVB pathway in replication of the murine leukemia virus (MLV) we took advantage of mouse models for the Hermansky-Pudlak syndrome (HPS) and Griscelli syndrome. In humans, these disorders are characterized by hypopigmentation and immunological alterations that are caused by defects in the biogenesis and trafficking of MVBs and other lysosome related organelles. Neonatal mice for these disease models lacking functional AP-3, Rab27A and BLOC factors were infected with Moloney MLV and the spread of virus into bone marrow, spleen and thymus was monitored. We found a moderate reduction in MLV infection levels in most mutant mice, which differed by less than two-fold compared to wild-type mice. In vitro, MLV release form bone-marrow derived macrophages was slightly enhanced. Finally, we found no evidence for a Ca(2+)-regulated release pathway in vitro. Furthermore, MLV replication was only moderately affected in mice lacking Synaptotagmin VII, a Ca(2+)-sensor regulating lysosome fusion with the plasma membrane.Given that MLV spreading in mice depends on multiple rounds of replication even moderate reduction of virus release at the cellular level would accumulate and lead to a significant effect over time. Thus our in vivo and in vitro data collectively argue against an essential role for a MVB- and secretory lysosome-mediated pathway in the egress of MLV

Assembly of the Murine Leukemia Virus Is Directed towards Sites of Cell–Cell Contact

Applying 4D imaging, this study investigates the mechanism by which cell-cell contact enhances retrovirus spreading and demonstrates that viral budding is highly polarized towards sites of cell-cell contact

Dynamics of HIV-1 Assembly and Release

Assembly and release of human immunodeficiency virus (HIV) occur at the plasma membrane of infected cells and are driven by the Gag polyprotein. Previous studies analyzed viral morphogenesis using biochemical methods and static images, while dynamic and kinetic information has been lacking until very recently. Using a combination of wide-field and total internal reflection fluorescence microscopy, we have investigated the assembly and release of fluorescently labeled HIV-1 at the plasma membrane of living cells with high time resolution. Gag assembled into discrete clusters corresponding to single virions. Formation of multiple particles from the same site was rarely observed. Using a photoconvertible fluorescent protein fused to Gag, we determined that assembly was nucleated preferentially by Gag molecules that had recently attached to the plasma membrane or arrived directly from the cytosol. Both membrane-bound and cytosol derived Gag polyproteins contributed to the growing bud. After their initial appearance, assembly sites accumulated at the plasma membrane of individual cells over 1–2 hours. Assembly kinetics were rapid: the number of Gag molecules at a budding site increased, following a saturating exponential with a rate constant of ∼5×10−3 s−1, corresponding to 8–9 min for 90% completion of assembly for a single virion. Release of extracellular particles was observed at ∼1,500±700 s after the onset of assembly. The ability of the virus to recruit components of the cellular ESCRT machinery or to undergo proteolytic maturation, or the absence of Vpu did not significantly alter the assembly kinetics