Production and degradation of fluorescent dissolved organic matter derived from bacteria

Dynamics of fluorescent dissolved organic matter (FDOM) in ocean environments has received attention over the past few decades. Although it has appeared that in situ production of oceanic FDOM is mainly due to bacteria, the production and bio- and photodegradation processes of bacterial FDOM have not been elucidated. In this study, a culture experiment with bacteria was carried out to assess the production and biodegradation processes of bacterial FDOM. Photodegradation of bacterial FDOM and dissolved organic carbon (DOC) was also examined by exposure to a solar simulator. Bacterial FDOM consists of six components which were determined by parallel factor analysis (PARAFAC). Fluorescence intensities of protein-like FDOM increased with the bacterial biomass, but the increases of humic-like FDOM lagged behind the protein-like FDOM by 5–10 days. Exposure to simulated sunlight caused significant decreases in fluorescence intensities of all components; 52–94% of the initial intensities were lost during 24 h. While, the DOC concentration exhibited a small decrease through the experiment (1.9–11.1%). These results showed that photodegradability of bacteria derived DOC was much less than the fluorescence, indicating that the lifetime of bacteria-derived DOC is much longer than the length estimated by the fluorescence. The role of photobleached FDOM derived from bacteria may be significant in the biogeochemical cycle at the surface layer.     

Use of flood chronology for detailed environmental analysis: a case study of Lake Kizaki in the northern Japanese Alps,central Japan

This paper presents a study of the usefulness of flood layers as a time marker in sediments and a report of a case study of Lake Kizaki in central Japan. A flood layer can be identified as a layer having a higher density, coarser grain size, lower TN content, and higher C/N ratio than those of the upper and lower horizons. It can also be characterized by a hyperpycnal sequence composed of a basal coarsening-upward unit and a top fining-upward unit. When flood layers can be correlated with heavy rains in meteorological records, detailed age markers are well established in the sediment. Five flood layers were identified in the surface sediment of Lake Kizaki, and they could be attributed to the historical heavy rainfalls that took place on July 12, 1995; September 28, 1983; August 25, 1974; September 26, 1959; and September 1, 1949 under the constraint of an age model. A precise age model is essential to clarify the environmental changes such as the pollutant history in detail.     

Helium isotopic fingerprints of the heavy land subsidence left in groundwater of the Saga Plain,near Beppu–Shimabara graben,Kyushu, Japan

The Saga Plain is near Beppu–Shimabara graben, a region of potential active volcanism. In the graben, mantle He, which has a high ³He/⁴He ratio of 1.1 × 10⁻⁵, escapes easily from the underlying subduction zone. In groundwater of the Saga Plain, except in the Shiroishi district, this ratio gradually increased as the dissolved He content increased, to a maximum of 5 × 10⁻⁶. In central Shiroishi, however, the ratio reached a minimum of 8.7 × 10⁻⁷ with increasing dissolved He content, suggesting that groundwater in central Shiroishi has selectively accumulated radiogenic He, which has a very low ratio of 1 × 10⁻⁸, rather than reflecting the regional He, which is rich in mantle He. This can be explained if groundwater in Shiroishi has become mixed with fossil pore water drawn from impermeable marine clay aquitard layers. The withdrawal of pore water has also caused severe land subsidence in central Shiroishi.     

Tributyltin in blood of marine fish collected from a coastal area of northern Kyushu, Japan

We investigated levels of the pollutant tributyltin (TBT) in blood of pufferfishes (six species), Japanese sea perch, red sea bream, Japanese common goby, Japanese flounder, rockfish, conger eel, and sea mullet collected off the coast of northern Kyushu, Japan. We found considerable levels of TBT (1.4-190 ng/mL) accumulated in the blood of these fish. Blood TBT concentrations were 1.3-22.5 times liver concentrations and 4.9-78 times muscle concentrations, except in conger eel and mullet. We detected TBT (16-111 ng/mL-blood) in the plasma of the fine-patterned puffer (Takifugupoecilonotus) year-round, without any apparent seasonal trend. These results suggest that fish inhabiting coastal areas of Kyushu, Japan, continue to be contaminated with TBT.     

Comparative analysis of measurements of stratospheric aerosol by lidar and aerosol sonde above Ny-Ålesund in the winter of 1995 [Comparative analysis of lidar and OPC observations]

Solid polar stratospheric cloud (PSC) layers observed by lidar and a balloon-borne optical particle counter (OPC) on 17 December 1995 are reexamined in a comparative analysis framework. The typical radius of solid particles in the observed PSC is determined through the comparative analysis to have been approximately 2.3 μm. A backward trajectory analysis for the air mass in which the solid particles were observed shows that the air mass had experienced temperatures 2–3 K below the frost point of nitric acid tri-hydrate (NAT) during the 4 days preceding the observations. The back-trajectory analysis traces the air mass back to northern Greenland and Ellesmere Island on 16 December, one day before the observations. A microphysical box model is used to investigate possible mechanisms of formation for the observed solid particles. The results of this model suggest that the solid particles formed under mesoscale temperature fluctuations associated with mountain lee wave activity induced by the relatively high terrestrial elevations of northern Greenland and Ellesmere Island.     

Effects of the Chemical Compositions of Salars de Uyuni and Atacama Brines on Lithium Concentration during Evaporation

During Li recovery from salar brines, Li concentration is typically increased to about 60,000 mg L^?1 by evaporation. We investigated the concentration changes of Li, Na, K, Mg, Cl, SO₄, and B during evaporation of both natural Uyuni and artificial Atacama brines. The Uyuni brine exhibited a maximum Li concentration of 6810 mg L^?1 at 31 days of evaporation, at which point the majority of the Na and K in the brine was removed. The Li concentration decreased with further evaporation due to precipitation as Li₂SO₄, such that the level at the 56 day mark was approximately 4130 mg L^?1. In contrast, the artificial Atacama brine showed no pronounced Li precipitation, even after 54 days, at which point the Li concentration was 21,800 mg L^?1. The initial concentrations of Na and K in the Atacama brine were higher than those in the Uyuni brine, and the Atacama solution still retained K after 54 days of evaporation. The order of precipitation of cation species during the evaporation of both brines was: Na, followed by K, Mg, and Li. Thus, Li precipitation in the Atacama brine might be prevented due to the more favored precipitations of Na and K, such that significant Li removal did not occur in this brine.     

Forecasting the effects of global warming on radial growth of subalpine trees at the upper and lower distribution limits in central Japan

Effects of global warming on radial growth were examined for the subalpine tree species Abies veitchii (1600–2200 m?a.s.l.), A. mariesii (2000–2500 m?a.s.l.) and Betula ermanii (1600–2500 m?a.s.l.) in central Japan, by using dendrochronological techniques. Chronologies of tree-ring widths were examined for the three species and of maximum latewood densities for the two Abies species at their upper and lower distribution limits (total 10 chronologies). We developed multiple regression models to reproduce these chronologies from the monthly mean temperature and sum of precipitation. Of the 10 chronologies, growth-climate relations could not be modeled for tree-ring width chronologies of the three species at their lower distribution limits because of low correlation. Annual mean temperature and annual sum of precipitation will increase about 3 °C and 100 mm, respectively, by 2100 in central Japan, according to 18 climatic change scenarios (6 general circulation models ×3 greenhouse gasses emission scenarios). We predicted tree-ring widths and maximum latewood densities by substituting 18 climatic change scenarios into the growth-climate models. Maximum latewood densities and tree-ring widths of A. mariesii at the upper and lower distribution limits increased by 2100. The rates of the increase tended to be greater for scenarios with more greenhouse gas emission. By contrast, maximum latewood densities of A. veitchii and tree-ring widths of B. ermanii were unchanged by 2100, irrespective of the three greenhouse gas emission scenarios. This study showed that radial growth of the three species responds differently to global warming and their responses are predictable by dendrochronological models.     

Correction to: Microtremor array method using spatial autocorrelation analysis of Rayleigh-wave data

Journal of Seismology -     

Microtremor array method using spatial autocorrelation analysis of Rayleigh-wave data

Journal of Seismology - Microtremor array measurements, and passive surface wave methods in general, have been increasingly used to non-invasively estimate shear-wave velocity structures for...     

Intrusion of Kuroshio-Derived bottom cold water into Osaka Bay and its possible cause

The bottom layer in Osaka Bay was occupied in August from 1980 to 1995 by a water mass of relatively low temperature and rich in nutrients in comparison to previous and following decades. The relationship between Osaka Bay bottom temperature and Kuroshio axis location south of Kii Peninsula has been investigated using the dataset archived by Osaka Research Institute of Environment of Agriculture and Fisheries and axis-location data provided by Marine Information Research Center. The correlation between bottom temperature in the bay and Kuroshio-axis distance from Cape Shionomisaki indicates that the bottom temperature in the bay decreases when the Kuroshio axis is a long distance from the cape, and vice versa. To investigate why the temperature distribution depends on the axis location, composite temperature maps are depicted using summer temperature data from 1970 to 2005 archived in the Japan Oceanographic Data Center (JODC) after dividing all data into two groups with different axis locations. These temperature maps and temperature-salinity plots using the same JODC data suggest a scenario: cold water in the Kuroshio intermediate layer is first upwelled on the eastern side of the Kii Peninsula and thereafter moves westward as a coastal boundary current in the Kelvin wave sense of the Northern Hemisphere when the Kuroshio axis is located around 74-km distance from Cape Shionomisaki. This scenario is validated using internal Froude number maps depicted using the JODC-archived hydrographic data and geostrophic current fields. In addition, the reanalysis daily data provided by Japan Coastal Ocean Predictability Experiment are used for the validation.