Differences in the damage caused by hypoxia to the macrobenthic communities in source regions of hypoxic water and in regions with advected hypoxic water

The objective of this study was to determine the effects of transported hypoxic water on macrobenthic species composition in Isahaya Bay, Kyushu, Japan. To this end, we conducted a field survey of water quality, sediment quality, and the macrobenthic community across seasons. Hypoxic intensity, defined as the percentage of the time that a region exhibits hypoxic conditions [dissolved oxygen (DO) <?3.0 mg L^?1], was calculated for the summer period from July 1 to September 30, 2014 based on continuous monitoring data derived from six monitoring towers in the bay. Here, we discuss how the hypoxia-induced damage, defined as the change in the species compositions of the macrobenthic communities in the bay due to hypoxia, differs between the inner and middle regions of the bay (with muddy sediment) and the outer regions of the bay (with sandy sediment). A decrease in the density of macrobenthic species that was correlated to the period of lowest DO concentration (<?1.0 mg L^?1) was observed in the inner region of the bay. A large number of species disappeared from the macrobenthic community in the outer region after the DO concentration had dropped to its lowest level, even though this region presented the lowest hypoxic intensity (6.6%). The species that disappeared, including crustaceans and some polychaetes, were presumed to be sensitive to, and to have escaped from, hypoxia. Fewer species disappeared from the inner and intermediate regions of the bay, which had high hypoxic intensities of 14.0 and 26.7%, respectively, than from the outer region. The reason for this appeared to be a predominance of hypoxia-tolerant species in the inner and intermediate regions but not in the outer region. Our study suggests that estimating the effect of hypoxia in a spatially heterogeneous environment must be done with caution.     

Crustal deformations associated with volcanic activities

Two models of pressure source to interpret the crustal deformations associated with volcanic activities are discussed by example. It is pointed that the magma pressure causing the crust to be deformed may sometimes trigger remarkable tectonic earthquakes around volcanoes.     

Magma eruption rates of Merapi volcano,Central Java,Indonesia during one century (1890–1992)

The magma eruption rates of Merapi volcano form 1890 to 1992 are re-examined chronologically. For this volcano, movements of extruded lavas and domes as well as their extrusions are important because they control the modes of the subsequent activities and cause nuées ardentes and lahars. The monthly eruption rates varied widely, but the cumulative volume of lavas has increased linearly and is expressed as 0.1x10⁶ m³/month. The magma production rate of this volcano may have been constant for these 100 years. Recurrent excessive effusion of lavas is tentatively interpreted by assuming a magma reservoir. The averaged eruption rate is small in comparison with other volcanoes such as Nyramuragia, Kilauea and Vesuvio. However, it is remarkable that the activity has been continuous for these 100 years and the total amount of lava discharged during this period reached more than 10⁸ m³. A simple model for the formation of the 1992 lava dome is presented. The viscosity of the lavas is probably between 10⁶ and 10⁷ P and the length of the magma conduit is probably less than 10 km.     

Seismic energy releases from volcanoes

Seismic energy release during the precursory, eruptive and declining stages of volcanic activities provides various information about the mechanisms of volcanic eruptions and the temporary developments of their activities. Hitherto the energy release patterns from precursory earthquake swarms were used to predict the eruption times, especially of andesitic or dacitic volcanoes. In this paper the discussion is expanded to quantify the total amount of seismic energy released at the threshold of volcanic eruptions, with reference to the results observed at several volcanoes. The results generally indicate that the cumulative seismic energy release from the precursory earthquake swarms exceed 10¹⁷¹⁸ergs before eruptions at any andesitic or dacitic volvanoes. This allows the seismic efficiency, or the ratio of energy radiated seismically, and the energy required for the volumetric expansion to be estimated by incorporating available deformation data with the seismic data. The dependency of seismic efficiency on the type of volcanic activity, i. e. non-explosive outbreaks, phreatic and magmatic eruptions, dome formation, etc., was evaluated from observations at a few volcanoes that provided a variety of examples.     

CaPtO3 as a novel post-perovskite oxide

Structural, morphological, magnetic, and thermal properties have been investigated for a novel post-perovskite oxide CaPtO₃ synthesized under high pressure. By comparing obtained structural parameters with those for known post-perovskite compounds, we argue that the chemical bond has a strong covalent character. Precise measurements of the Langevin susceptibility χ ₀ = −9.6 × 10⁻⁵ emu/mol and Debye temperature θ ∼ 470 K provide a good opportunity to confirm the reliability of first-principle calculations on predicting physical properties of the Earth’s D” layer.     

Effects of spilled oil on microbial communities in a tidal flat

Effects of spilled oil on microbial communities in tidal flats were examined by use of a simulator for a tidal flat ecosystem. The simulator is composed of a wave generator, a tide control device, and a tidal flat. Sediment for the tidal flat was obtained at a natural tidal flat in Hiroshima Bay, Japan. After stabilizing the benthic organisms, fuel oil C was added to the surface of the flat at 1 lm(-2). Although the total number of micro-organisms remained at 1.5-3.5 x 10(9) cells g(-1) dry sediment irrespective of the addition of oil, bacterial communities which were analyzed based on the 16S rDNA showed clear changes after the addition of fuel oil C and after a subsequent recovery period. Bacterial colonies were randomly isolated from the oil-supplemented sediment during the experiments, and the isolates were examined for susceptibility to hydrocarbons in order to screen the oil-susceptible bacteria. The proportion of oil-susceptible bacteria in the isolates decreased with the addition of the oil. Oil-susceptible bacteria showed an inability to assimilate petroleum compounds as well as an inhibition of growth. The possibility of using oil-susceptible bacteria as an indicator of bioremediation in tidal flats was discussed.     

Simultaneous hard X-ray and optical observations of Sco X-1 and a model of semi-opaque X-ray sources

Simultaneous observations of hard X-ray and optical emission from Sco X-1 were carried out at Hyderabad, India, on April 16 and 19, 1972. During the first and the second observations Sco X-1 was on the average in a bright phase ofB=12.5 mag. and a slightly darker phase ofB=12.7 mag. respectively. During the first observation the X-ray intensity in the energy range 20–40 keV measured with balloon borne scintillation counters showed an enhancement of a factor of about two in coincidence with an optical flare ofB0.2 mag., whereas the apparent temperature derived from the X-ray spectrum observed in the energy range 20–35 keV showed no appreciable change. Both the X-ray intensity and the apparent temperature observed on April 19 are considerably lower than those observed on April 16. Taking into account the effect of radiative transfer in a hot plasma, the electron density and the optical depth for electron scattering of the plasma cloud are derived asn _e 3×10¹⁶ cm^–3 and _es 10 for the quiescent bright phase. The flare is explained by an increase of the plasma mass by about 30% and an increase of _es by _es 1 without appreciable change of the plasma temperature. The results on April 19 is interpreted as indicating that the quiescent dark phase may be characterized by a decrease of the plasma mass, its contraction and lower temperature.