Sedimentary records of reduction in resting egg production of <Emphasis Type="Italic">Daphnia galeata</Emphasis> in Lake Biwa during the 20th century: a possible effect of winter warming

To clarify long-term variations in the resting egg production of Daphnia galeata in Lake Biwa during the 20th century, we examined an abundance of plankton remains and ephippia in a 26-cm sediment core with a time resolution of approximately 2–6 years. Historical changes shown by these plankton remains indicated that the Daphnia population has not produced resting eggs since the 1980s, but it has remained the most abundant zooplankton species in the lake. Plankton monitoring data collected from 1966 to 2000 revealed that the overwintering individuals (January–March) of D. galeata plankters showed a significant increasing trend in recent years, such increase being negatively correlated with ephippial abundance in the sediment samples. Further analyses showed that the dominant phytoplankton in winter has changed from large inedible diatoms to edible flagellated algae, probably due to changes in vertical mixing regimes resulting from winter warming. These changes that occurred in the last several decades suggest that global warming has improved winter food conditions and thus enabled the Daphnia plankton to maintain its population without producing resting eggs in Lake Biwa.     

Determination of dissolved nucleic acids in seawater by the fluorescence dye, ethidium bromide

A new method for the determination of dissolved double-stranded deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) in seawater was developed, evaluated and used to study the fates of these nucleic acids in marine ecosystems. These nucleic acids, which were pre-concentrated on a hydroxyapatite column, were determined fluorometrically by the use of ethidium bromide dye, which binds specifically to the double-stranded polynucleotide. No dissolved organic matter coexisting in the pre-concentrated sample solution interfered in the analysis of DNA and RNA. Column recoveries of DNA and RNA in a sample volume of up to 11 were 93% and 97%, respectively, and 90% of both at 51. The detection limits of DNA and RNA concentrated from a 51 sample by this fluorometric method were 0.6 and 1.1 μg l⁻¹, respectively. The concentration of dissolved nucleic acids in the waters from Tokyo Bay and Sagami Bay showed great variation in space and time. DNA ranged from 1 to 32 μg l⁻¹, and RNA from below the detection limit to 34 μg l⁻¹. The total amount of phosphorus in nucleic acids was an important fraction (12.9 ± 8.2%) of the dissolved organic phosphorus (DOP) and showed a good correlation with DOP.     

On the Application of Mwp in the Near Field and the March 11, 2011 Tohoku Earthquake

Tsunami Warning Centers issue rapid and accurate tsunami warnings to coastal populations by estimating the location and size of the causative earthquake as soon as possible after rupture initiation. Both US Tsunami Warning Centers have therefore been using Mwp to issue Tsunami Warnings 5–10 min after Earthquake origin time since 2002. However, because Mwp (Tsuboi et al., Bulletin of the Seismological society of America 85:606–613, 1995) is based on the far-field approximation to the P-wave displacement due to a double couple point source, we should only very carefully apply Mwp to data obtained in the near field, at distances of less than a few wavelengths from the fault. On the other hand, the surface waves from Great Earthquakes, including those that occur just offshore of populated areas, such as the 2011 Tohoku earthquake, clip seismographs located near the fault. Because the first arriving P-waves from such large events are often on scale, Mwp should provide useful information, even for these Great Earthquakes. We therefore calculate Mwp from 18 unclipped STS-1 broadband P-wave seismograms, recorded at 2–15° distance from the Tohoku epicenter to determine if Mwp can usefully estimate Mw for this earthquake, using data obtained close to the epicenter. In this case there should be a good chance to get reliable Mwp values for stations at epicentral distances of 9–10°, since the source duration for the Tohoku earthquake is less than 200 s and the time window used to estimate Mwp is 120 s in duration. Our analysis indicates that Mwp does indeed give reliable results (Mw ~ 9.1) beginning at about 11° distance from the epicenter. The values of Mwp from seismic waveforms obtained at 11–15° epicentral distance from the Mw 9.1 off the east coast of Tohuku earthquake of March 11, 2011 fell within the range 9.1–9.3, and were available within 4–5 min after origin time. Even the Mwp values of 7.7–8.4, obtained at less than 5° epicentral distance, exceed the PTWC’s threshold of Mw 7.6 for issuing a regional tsunami warning to coastal populations within 1,000 km of the epicenter, and of Mw 6.9 for issuing a local tsunami warning to the coastal populations of Hawaii.     

Development of density measurement for metals at high pressures and high temperatures using X-ray absorption imaging combined with externally heated diamond anvil cell

A technique for density measurement under high pressure and high temperature was developed using the X-ray absorption imaging method combined with an externally heated diamond anvil cell. The densities of solid and liquid In were measured in the pressure and temperature ranges of 3.2–18.6 GPa and 294–719 K. The densities obtained through the X-ray absorption imaging method were in good agreement (less than 2.0% difference) with those obtained through X-ray diffraction. Based on the measured density, the isothermal bulk modulus of solid In is determined as 48.0 ± 1.1?40.9 ± 0.8 GPa at 500 K, assuming K′ = 4 to 6. The compression curve of liquid In approaches that of solid In at higher pressures and does not cross over the solid compression curve in the measurement range. The present technique enables us to determine the densities of both solids and liquids precisely in a wide pressure and temperature range.     

Two-stage model of incorporation of seamount and oceanic blocks into sedimentary melange: Geochemical and biostratigraphic constraints in Jurassic Chichibu accretionary complex, Shikoku, Japan

Abstract The significance of timing and formation of mélange in accretionary prisms, particularly concerning basaltic and related rocks and pelagic sediments, is exemplified in the Sawadani area of the Jurassic Chichibu accretionary complex in Shikoku, southwest Japan. Major and trace element geochemistry of the basaltic and related rocks indicates that all are of a hot-spot origin which produced a seamount. Most of the rocks have a trend of differentiation from an alkalic parental magma. The time relationship between the blocks and matrices of the mélange deduced from radiolarian fossil evidence and macro- to microscopic characteristics of contacts between different lithologies indicates two stages of mixing of materials in the seafloor. The first mixing occurred on the flank of the seamount in the pelagic environments in the Late Permian, and the second occurred on the trench floor or in the accretionary prism after the Early Jurassic. These two stages show respectively the geological phenomena of a seamount within the Izanagi-Kula plate and its incorporation into the Asian continental margin.     

Stoichiometry among bioactive trace metals in the Chukchi and Beaufort Seas

The distribution of Al, Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb in seawater was investigated in the Chukchi and Beaufort Seas of the western Arctic Ocean in September 2000. The unfiltered and filtered seawater samples were used for determination of total dissolvable metal (TDM) and dissolved metal (DM), respectively. The concentration of labile particulate metal (LPM) was estimated with the difference between that of TDM and DM. The concentrations of TDAl, TDMn, TDFe, TDCo and TDPb varied substantially in the study area. The high concentrations occurred at stations near the Bering Strait, in the Mackenzie delta, and above reductive sediments on the shelf and slope. These elements were mostly dominated by labile particulate species, such as Fe?CMn oxides and species adsorbed on terrestrial clay. DCo was correlated with DMn over the study area (r?=?0.78, n?=?135), and the slope of the regression line was 27 times higher at a pelagic station than at a shelf station. TDNi, TDCu, TDZn and TDCd showed relatively small variations and were generally dominated by dissolved species. There was a moderate correlation between DCd and phosphate for all samples (r?=?0.79), whereas there were no significant correlation between the other DMs and nutrients. TDNi and TDCu showed a remarkable linearity for most stations except those near the Bering Strait (R ²?=?0.95, n?=?126). These results suggest that biogeochemical cycling including uptake by phytoplankton and remineralization from settling particles has only minor control over the distribution of trace metals in this area. Using the present data, the annual input of bioactive trace metals form the Bering Strait and the Mackenzie River was estimated. Also, the trace metal compositions of major water masses were evaluated. The dissolved elemental ratio was P:Al:Mn:Fe:Co:Ni:Cu:Zn:Cd?=?1:1.2?×?10^?2:4.4?×?10^?4:1.4?×?10^?3:3.7?×?10^?5:3.7?×?10^?3:1.4?×?10^?3:4.5?×?10^?3:2.2?×?10^?4 for Canada Basin deep water (CBDW). This ratio was significantly different from that for Pacific deep water and Bering Sea water, suggesting substantial modification of the trace metal compositions of seawater in the study area.     

Manganiferous schists and their origin,Hidaka Mountains,Hokkaido, Japan

Manganiferous quartz-mica schists (4 m in stratigraphic thickness) overlie epidote amphibolite in the Chiroro River area, Hidaka Mountains, Hokkaido. The schist layers have a considerable range of A/F ratios and bulk oxidation ratios which vary from 21.5 to 100. Manganese contents are from 4 to 30 times higher than that of the average shale with 0.09% MnO. The schists are essentially quartz-white mica-biotite-Mn garnet-tourmaline-±epidote-magnetite assemblages. A highly oxidized layer (5–8 cm thick) 95 cm above the epidote amphibolite contact is characterized by viridine-piemontite-spessartine-Mn white mica-Mn tourmaline-Ti-Mn haematite indicative of both high initial manganese content and very high f _O2 conditions of recrystallization.Viridine contains up to 17 mol% Mn³⁺SiO₅ and coexists with piemontite with between 13.6 and 15.4 wt% Mn₂O₃. Mn-poor-Fe-rich (Ps₃₂) epidote occurs in the less oxidized schist enclosing the viridine-piemontite bearing seam. Garnets vary widely in composition with end member variations (mol%) of Spess_22.9–80.5; And_0.2–11.7; Alm_1.1–57.1; Pyr_2.0–12.2; Gross_7.0–49.0. The more manganiferous garnets occur in rocks with higher oxidation ratios while almandiferous varieties occur in schists with low oxidation ratios. Biotite ranges from green to red-brown varieties (increasing Ti and Fe) with Mg/ (Mg+Fe) ratios varying from 56 to 48. Ten to fifteen percent octahedral R²⁺ is replaced by Al indicating a trend towards eastonite-siderophyllite. The white micas deviate only slightly from dioctahedral stoichiometry but have up to 25% of octahedral sites occupied by Fe, Mg and to a lesser extent Mn and Ti as R²⁺ Si⁴⁺2Al³⁺ and in highly oxidized rocks as (Fe,Mn)³⁺Al³⁺. The white mica in the highly oxidized viridine-piemontite schist is pale pinkishorange, exhibits reverse pleochroism, and has between 0.30 and 0.43 wt% Mn₂O₃.There is a close comparison, both in terms of stratigraphic thickness and Fe-Mn variation, between the Chiroro schist sequence and many oceanic cores so that the bulk chemistry and mineralogy of the pelitic schists is largely an extension of the original Eh-pH conditions of hemipelagic sedimentation and post-depositional adjustments during diagenesis. The thin viridine-piemontite bearing schist is correlated with an oxidized, Fe-Mn rich layer commonly found in present day oceanic cores. The viridine presumably formed by reaction of original ferro-manganese microgranules and clay minerals. Halmrolytic alteration of the underlying metabasalt resulted in leaching of Mn and Fe (in particular) into the overlying sediments and the formation of concentrations of haematite — manganese oxide — Mn garnet along the schist-epidote amphibolite contact.Estimation of the P-T conditions of metamorphism from the phase relations and compositions in the epidote amphibolite associated with the manganiferous schist gives T °C = 530560 and a minimum P _fluid > 3 kb which corresponds to the epidote amphibolite facies of Barrovian-type terrains.This paper is dedicated to Professor Kenzo Yagi on the occasion of his retirement from the Chair of Mineralogy, Department of Geology and Mineralogy, Hokkaido University, Sapporo, Japan     

侵蚀沉积模型在嘉陵江流域的应用

从20世纪50年代到80年代长江宜昌水文站观测的泥沙输送量逐年增加,但是到了90年代却出现了逐渐减少的趋势。泥沙量增加的原因主要是乱伐森林和土地利用方式的快速改变,而减少的原因则可能是采取了一系列防止水土流失的对策和在上游修建了许多大坝而造成的。嘉陵江流域是长江泥沙的主要源区之一,90年代每年从嘉陵江流域到长江的输沙量减少到1988年前的约36%。因此,分析该流域每年泥沙输送动态及其变化原因,对制定减小水土流失的森林规划,防止三峡水库的淤积以及保护长江流域的生存环境和生态系统等具有重大意义。本研究开发并改进了一个流域集水坡面上的侵蚀模型,并将它应用到1987年的嘉陵江流域,以对其适用性进行了研究。结果表明,该模式可被用于月度泥沙生产量的评估中。