Sponges boring into precious corals: an overview with description of a new species of Alectona (Demospongiae, Alectonidae) and a worldwide identification key for the genus     

Barbara Calcinai  Carlo Cerrano  Nozomu Iwasaki  & Giorgio Bavestrello 《Marine Ecology》2008,29(2):273-279

Precious corals represent peculiar substrata for several species of boring sponges that exploit their carbonatic scleraxis, strongly decreasing their commercial value. Here we describe a new species of the genus Alectona from Japan recorded in a colony of Paracorallium japonicum (Kishinouye, 1903). The spicular complement of the new species consists of diactinal spicules covered by mushroom-like tubercles, often modified into styloid forms, and fusiform amphiasters with two or sometimes four verticils, each generally made up of six short tubercled rays. A complete survey of the literature on boring sponges recorded in precious corals in the Mediterranean Sea and Pacific Ocean indicates that the species of the family Alectonidae are the most strictly associated to this kind of substratum. Their world distribution, in fact, partially or totally overlap that of their coral hosts.  相似文献   

Chemical composition of volcanic gases in Japan     

I. Iwasaki  T. Ozawa  M. Yoshida  T. Katsura  B. Iwasaki  M. Kamada 《Bulletin of Volcanology》1962,24(1):23-48

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Occurrence and chemical composition of the Eoarchean carbonate rocks of the Nulliak supracrustal rocks in the Saglek Block of northeastern Labrador,Canada     

Satoshi Yoshida  Akira Ishikawa  Shogo Aoki  Tsuyoshi Komiya 《Island Arc》2021,30(1):e12381

The Eoarchean Nulliak supracrustal rocks in the Saglek Block of northeastern Labrador, Canada, contain some of the world's oldest carbonate rocks. This work attempted to reveal the origin of the carbonate rocks and estimate the surface environmental conditions of the early Earth based on their occurrence and geochemistry. They occur together with mafic and ultramafic rocks in Pangertok Inlet and St. John's Harbour South, whereas they are interlayered with pelitic rock layers with quartzofeldspathic mineral assemblages in St. John's Harbour East and Big Island. The geological occurrence suggests that the formers were formed around hydrothermal fields, whereas the latters were deposited near a continental margin. Some carbonate rocks have high SiO₂, Al₂O₃, and Zr contents, indicating that the silicification and involvement of detrital materials influenced their composition; thus, pure carbonate rocks were selected using a combined filter of the SiO₂, TiO_2, Al₂O₃, Zr, and Ba contents. The selected carbonate rocks have positive La, Eu, Gd, Y, U, Pb, and Sr anomalies, negative Nb, Zr, and Hf anomalies, and relatively small enrichment in heavy rare earth elements (HREEs). The La and Y anomalies suggest that they originated from chemical sediments precipitated from seawater. On the other hand, the small HREE-enrichment suggests that REEs were mainly dissolved as REE-carbonate complexes in seawater or that the riverine influxes were dominated by the detritus of Eoarchean continental crusts, presumably composed of HREE-depleted TTG. The U anomaly suggests that uranium was more dissolved than Th as U-bearing carbonate complexes in seawater. The Nulliak carbonate rocks also show a positive correlation between Y and Eu anomaly values, suggesting that the precipitation of iron-oxyhydroxide causing the Y anomaly was more significant near the hydrothermal fields than the continental margin, consistent with an alkaline hydrothermal model.  相似文献   

Steric sea level changes estimated from historical ocean subsurface temperature and salinity analyses   总被引：13，自引：0，他引：13  

Masayoshi Ishii  Masahide Kimoto  Kenji Sakamoto  Sin-Iti Iwasaki 《Journal of Oceanography》2006,62(2):155-170

An historical objective analysis of subsurface temperature and salinity was carried out on a monthly basis from 1945 to 2003 using the latest observational databases and a sea surface temperature analysis. In addition, steric sea level changes were mainly examined using outputs of the objective analyses. The objective analysis is a revised version of Ishii et al. and is available at 16 levels in the upper 700 m depth. Artificial errors in the previous analysis during the 1990s have been worked out in the present analysis. The steric sea level computed from the temperature analysis has been verified with tide gauge observations and TOPEX/Poseidon sea surface height data. A correction for crustal movement is applied for tide gauge data along the Japanese coast. The new analysis is suitable for the discussion of global warming. Validation against the tide gauge reveals that the amplitude of thermosteric sea level becomes larger and the agreement improves in comparison with the previous analysis. A substantial part of local sea level rise along the Japanese coast appears to be explained by the thermosteric effect. The thermal expansion averaged in all longitudes from 60°S to 60°N explains at most half of recent sea level rise detected by satellite observation during the last decade. Considerable uncertainties remain in steric sea level, particularly over the southern oceans. Temperature changes within MLD make no effective contribution to steric sea level changes along the Antarctic Circumpolar Current. According to statistics using only reliable profiles of the temperature and salinity analyses, salinity variations are intrinsically important to steric sea level changes in high latitudes and in the Atlantic Ocean. Although data sparseness is severe even in the latest decade, linear trends of global mean thermosteric and halosteric sea level for 1955 to 2003 are estimated to be 0.31 ± 0.07 mm/yr and 0.04 ± 0.01 mm/yr, respectively. These estimates are comparable to those of the former studies.  相似文献   

Post-collapse evolution of small-N clusters     

Shogo Inagaki 《Astrophysics and Space Science》1986,118(1-2):367-370

N-body simulations were made to study post-collapse evolution of small-N clusters. The qualitative behaviour of the dynamical evolution is the same as in the Fokker-Planck approximation. The flatter is the mass spectrum, the more violent is the activity of binaries and so are the expansion and contraction of the cluster core.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   

Oxygen, silicon, and Mn-Cr isotopes of fayalite in the Kaba oxidized CV3 chondrite: Constraints for its formation history     

Xin Hua  Gary R. Huss  Shogo Tachibana 《Geochimica et cosmochimica acta》2005,69(5):1333-1348

The iron-rich olivine end-member, fayalite, occurs in the matrix, chondrules, Ca-Al-rich inclusions (CAIs), silicate aggregates, and dark inclusions in the Kaba and Mokoia oxidized CV3 chondrites. In most occurrences, fayalite is associated with magnetite and troilite. To help constrain the origin of the fayalite (Fa_98-100), we measured oxygen and silicon isotopic compositions and Mn-Cr systematics in fayalite from two petrographic settings of the Kaba meteorite. One setting consists of big fayalite laths embedded in the matrix and radiating from a core of fine-grained magnetite and sulfide, while the other setting consists of small fayalite-magnetite-sulfide assemblages within or at the surface of Type I barred or porphyritic olivine chondrules. Oxygen in the big fayalite laths and small chondrule fayalites falls on the terrestrial fractionation line, and is distinct from that in chondrule forsterites, which are enriched in ¹⁶O (Δ¹⁷O = ∼−4‰). Oxygen in the big fayalite laths may be isotopically heavier than that in chondrule fayalites. Silicon isotopes suggest that forsterite is ∼1‰/amu heavier than adjacent fayalite within Kaba chondrules. However, we were unable to confirm large silicon isotopic differences among fayalites reported previously. The Mn-Cr data for big Kaba fayalites give an initial ⁵³Mn/⁵⁵Mn ratio of (2.07 ± 0.17) × 10⁻⁶, consistent with literature results on Mokoia chondrule fayalites. The combined data suggest that fayalites in both petrographic settings formed at about the same time, ∼9.7 Ma after the formation of CAIs. Our data indicate that those fayalite-magnetite-troilite assemblages replacing metal inside and around chondrules formed by aqueous alteration on the meteorite parent body. The formation site and mechanism for the big fayalite laths is less clear, but the petrographic setting indicates that they did not form in situ. None of the models that have been suggested for formation of these fayalites is entirely satisfactory.  相似文献   

Monitoring and simulation of water, heat,and CO2 fluxes in terrestrial ecosystems based on the APEIS-FLUX system   总被引：2，自引：0，他引：2  

WATANABEMasataka WANGQinxue HAYASHISeiji MURAKAMIShogo LIUJiyuan OUYANGZhu LIYan LIYingnian WANGKelin 《地理学报(英文版)》2005,15(2):131-141

1IntroductionInJune1992,theworldsummitorganizedbytheUnitedNations,withparticipantsincludingnationalleadersfromaroundtheworld,concludedwithAgenda21(UnitedNations,1992),theRioDeclarationonEnvironmentandDevelopment,inRiodeJaneiro.Thedeclarationpromptedcountr…  相似文献   

Differentiation of volcanic emanation around the boiling point of water in geothermal regions in Japan     

I. Iwasaki  T. Ozawa  M. Yoshida 《Bulletin of Volcanology》1966,29(1):517-527

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V_pIV_s ratio structure of the Lofoten continental margin, northern Norway, and its geological implications     

Shuichi Kodaira  Martin Bellenberg    Takaya Iwasaki    Toshihiko Kanazawa    Hans B. Hirschleber  Hideki Shimamura 《Geophysical Journal International》1996,124(3):724-740

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III-3 A study on floating body of wave energy absorber     

Naomasa Iwasaki  Norimasa Takagi  Masanori Abe  Masaki Sakuta 《Ocean Engineering》1985,12(6):569

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