Quaternary paleolake formation and cataclysmic flooding along the upper Yenisei River

A suite of geomorphological and sedimentological features in the catchment of the upper Yenisei River in the Sayan mountains of southern Siberia testifies to the occurrence of cataclysmic floods that flowed down the river. Evidence of large-scale high-energy flood events includes: 1) gravel dunes, up to a few meters high and spaced 50 to 80 m apart, in the Kyzyl Basin 2) landforms such as hanging valleys and paleochannels and 3) flood sediments in a tributary valley. The origins of the Yenisei floods were likely diverse due to complex hydrological processes operating in the Sayan mountains. The possibilities include failures of multiple, variably impounded (ice, sedimentary, tectonic scarp, and lava flow dams) paleolakes in the two large intermontane basins of Darkhadyn Khotgor and Todza, and other minor basins, in the upper Yenisei River catchment. Dating techniques applied to the paleolakes in the Darkhadyn Khotgor and Todza basins revealed their formation during various periods in the middle–late Pleistocene and Holocene. Flooding from the Darkhadyn Khotgor appears to explain many of the inferred flood features, although contributions by flooding from other paleolake basins cannot be ruled out. Computer simulation of the flooding caused by a Darkhadyn Khotgor paleolake ice-dam failure indicates a probable peak discharge of  3.5 × 10⁶ m³ s^− 1, approximately one-fifth that of the floods that formed the Channeled Scabland in the U.S.A. Many of the outburst events probably occurred in the late Quaternary, but earlier floods could also have occurred.     

Water requirements for cultivatingSalicornia bigeloviiTorr. with seawater on sand in a coastal desert environment

The forage and oilseed halophyte,Salicornia bigeloviiTorr., was grown in gravity-drained lysimeters set in open plots of the same crop over two seasons in a coastal desert environment in Sonora, Mexico. The lysimeters were irrigated daily with seawater (40 g l⁻¹salts) at rates ranging from 46–225% of potential evaporation. Biomass and seed yields increased with increasing irrigation depth over the range of treatments. Biomass yields ranged from 13·6–23·1 t DM ha⁻¹, equivalent to conventional forage crops, on seasonal water application depths of 2·3–3·8 m, but were markedly lower at lower irrigation depths. Increasing the irrigation depth lowered the soil solution salinity, resulting in greater growth and water use, and hence leaching fractions that were nearly even over irrigation treatments, averaging 0·5. Evapo-transpiration rose in direct proportion to the irrigation depth. Potential evaporation was estimated by site pan evaporation and by the Blaney-Criddle and Penman models using climatological data; the methods agreed within 15%. The ratio of evapo-transpiration to potential evaporation increased over the growing season and approached 1·5 by pan on the highest irrigation treatment due to the combined effects of high transpiration and high evaporation from the permanently moist soil surface. The best field predictor of biomass yield was the salinity of the soil moisture in the top 15 cm of soil profile, which constitutes the root zone for this crop. Root zone salinity must be kept at 70–75 g l⁻¹for high yields. Although irrigation and drainage requirements were high compared to conventional crops, seawater irrigation appears to be feasible in medium sand and could augment crop production along coastal deserts. The possibility of using this crop for animal production is discussed.     

Protective effect of phospholipid hydroperoxide glutathione peroxidase (PHGPx) against lipid peroxidation in mussels Perna perna exposed to different metals

Levels of antioxidant defenses and lipid peroxidation were evaluated in mussels exposed to lead (200 mg/l), iron (500 microg/l), cadmium (200 microg/l) and copper (40 microg/l), for 12, 24, 72 and 120 h. Glutathione S-transferase (GST) activity was unchanged with all treatments. Catalase (CAT) increased after 120 h of exposure to all metals. Mussels exposed to Cd for 12 h, and to Cu and Fe for 120 h had increased lipid peroxidation, which might be associated to decreased levels of reduced glutathione (GSH) and glutathione peroxidase (GPx) activity. Pb exposure caused GSH depletion after 12 h and increased GPx activity after 120 h. Negative correlations were observed between the enzyme phospholipid hydroperoxide glutathione peroxidase (PHGPx) and malonaldehyde (MDA) levels after Fe and Cu exposure, indicating a protective role of PHGPx against lipid peroxidation, and suggesting the use of this enzyme as a new potential biomarker of toxicity associated with contaminant exposure in mussels.     

A numerical simulation of the distribution of water temperature and salinity in the Seto Inland Sea

Constant flows, as well as oscillatory tidal flow, play an important role in the long-term dispersion of water in the Seto Inland Sea. Two kinds of numerical model (1-line and 2-line models) of the Seto Inland Sea have been developed to determine the role of density-induced currents, one type of the constant flow, in water dispersion in the Inland Sea. The seasonal variations of temperature, salinity and density fields are simulated and the density-induced current field is predicted at the same time. It is found that the most appropriate value of the longitudinal eddy diffusion coefficient,K _x, is 5×10⁶–7×10⁶ cm²sec^–1. The value of the overall mean dispersion coefficient is of the order of 10⁷cm²sec^–1 (Hayami and Unoki, 1970). Consequently, it is suggested that 50–70% of the total dispersion in the Seto Inland Sea can be attributed to currents other than density-induced currents,i.e., tidal currents, tide-induced currents and wind-driven currents.In winter, both density and velocity fields, calculated using the 1-line model, satisfy the conditions for the existence of a coastal front in Kii Channel and in the eastern Iyo-nada.     

Thermal metamorphism of CI and CM carbonaceous chondrites: An internal heating model

Abstract— Infrared diffuse reflectance spectra were measured for several thermally metamorphosed carbonaceous chondrites with CI-CM affinities which were recently found from Antarctica. Compared with other CI or CM carbonaceous chondrites, these Antarctic carbonaceous chondrites show weaker absorption bands near 3 μm due to hydrous minerals, and weaker absorption bands near 6.9 μm due to carbonates, interpreted as thermal metamorphic features. These absorption bands also disappear in the spectra of samples of the Murchison (CM) carbonaceous chondrite heated above 500 °C, implying that the metamorphic temperatures of the Antarctic carbonaceous chondrites considered here were higher than about 500 °C. Model calculations were performed to study thermal metamorphism of carbonaceous chondrites in a parent body internally heated by the decay of the extinct nuclide ²⁶Al. The maximum temperature of the interior of a body more than 20 km in radius is 500–700 °C for the bulk Al contents of CI and CM carbonaceous chondrites, assuming a ratio of ²⁶Al/²⁷Al = 5 × 10^?6 which has been previously proposed for an ordinary-chondrite parent body. The metamorphic temperatures experienced by the Antarctic carbonaceous chondrites considered here may be attainable by an internally heated body with an ²⁶Al/²⁷Al ratio similar to that inferred for an ordinary-chondrite parent body.     

Microbial community respiration and structure of dead zone sediments of Omura Bay, Japan

Monitoring sediment microbial community metabolism and structure is instrumental to understanding biogeochemical processes in and ecological impacts on bottom environments. The aim of this study was to determine potential community respiration and to reveal community dynamics of the microorganisms in the dead zone sediments of Omura Bay, Japan. The bay is highly enclosed and develops severe hypoxia in the central regions every summer. We collected sediment core samples from the center of the bay during hypoxia, estimated sediment oxygen consumption by using an adapted in vivo electron transport system activity (in vivo ETSA) assay, enumerated abundance of bacteria, and analyzed bacterial community structure by automated ribosomal intergenic spacer analysis. Higher ETSA and bacterial diversity were found in upper sediments (within 3?cm depth) from the center than the fringe of the bay. Sediment bacterial community structure of the bay center was distinct from that of the fringe. From these results, upper sediment in the dead zone of Omura Bay was characterized by (1) greater community respiration and (2) greater diversity of bacterial components compared with the non-hypoxic sediment of the bay fringe. These characteristics have important implications for understanding the interaction between microbial communities and the development of hypoxia in Omura Bay.     

Field measurements of absolute gravity in East Antarctica

Abstract This paper reports the results of field-based absolute gravity measurements aimed at detecting gravity change and crustal displacement caused by glacial isostatic adjustment. The project was initiated within the framework of the 53rd Japanese Antarctic Research Expedition （JARE53）. Absolute gravity measurements, together with GPS measurements, were planned at several outcrops along the Prince Olav Coast and S6ya Coast of East Antarctica, including at Syowa Station. Since the icebreaker Shirase （AGB 5003） was unable to moor alongside Syowa Station, operations were somewhat restricted during JARE53. However, despite this setback, we were able to complete measurements at two sites： Syowa Station and Langhovde. The absolute gravity value at the Syowa Station IAGBN （A） site, observed using an FG-5 absolute gravimeter （serial number 210; FG-5 #210）, was 982 524 322.7＋0.1 ktGal, and the gravity change rate at the beginning of 2012 was -0.26 gGal.a-1. An absolute gravity value of 982 535 584.2~0.7 ktGal was obtained using a portable A-10 absolute gravimeter （serial number 017; A-10 #017） at the newly located site AGS01 in Langhovde.