Dynamics of microphytobenthic biomass in a coastal area of western Seto Inland Sea, Japan   总被引：2，自引：0，他引：2  

Hitomi Yamaguchi  Shigeru Montani  Hiroaki Tsutsumi  Ken-ichiro Hamada  Naoko Ueda  Kuninao Tada 《Estuarine, Coastal and Shelf Science》2007,75(4):423-432

This study focused on the causes of the variation in microphytobenthic biomass and the effects of this variation on macrobenthic animals in the western Seto Inland Sea, Japan, where the importance of microphytobenthos as the primary food source for benthic animals has been recently reported. We investigated the microphytobenthic biomass together with light attenuation of seawater, phytoplanktonic biomass, macrobenthic density and biomass at eight stations (water depth = 5–15 m) during four cruises in 1999–2000. The increased light attenuation coefficient of the water column associated with increased concentration of the phytoplanktonic Chl-a caused a decrease in light flux that reached the seafloor. The biomass of the microphytobenthos within the upper 1 cm of the sediment, 1.9–46.5 mg Chl-a m⁻², was inversely correlated with the phytoplanktonic biomass in the overlying water column, 10.9–65.0 mg Chl-a m⁻². Thus, interception of light by phytoplankton is considered to be a main cause of the variation in the microphytobenthic biomass. The microphytobenthos biomass showed a significant positive correlation with the macrobenthic density (78–9369 ind. m⁻²) and biomass (0.4–78.8 gWW m⁻²). It appears that the increase in oxygen production by the microphytobenthos allowed macrobenthic animals to become more abundant, as a consequence of oxygenation of the organically enriched muddy sediments (14.5 ± 2.69 mg TOC g⁻¹). This study suggests that the variation in the microphytobenthic biomass is influenced by the phytoplanktonic biomass due to shading effect, and the balance between these two functional groups might affect the variability in the macrobenthic density and biomass.  相似文献   

A study on the chemical forms of radionuclides in seawater—II chloride and sulfate complexes of60Co     

Shigeki Hirano  Taku Koyanagi 《Journal of Oceanography》1980,36(1):35-38

The apparent stability constants for chloride and sulfate ions with Co (II) at ionic strength of 0.67 were determined by the cation exchange method. The value of the stability constant ₁ for chloride ion with Co (II) ion was 0.79±0.055. The stability constants ₁, ₂ and ₃ for sulfate ion with Co (II) ion were 12.0±0.27, 91.5±11.4 and l,110±250, respectively. The chemical species of Co (II) in seawater was estimated at the pH of 8.0 to be present as Co²⁺ (63%), CoCl⁺ (27%) and CoSO₄ ⁰ (8.6%) using the known value of dissociation constant of Co (II), and under the assumption that only major inorganic anions are responsible for the chemical equilibrium of Co (II).  相似文献   

Preferential dissolution of SiO<Subscript>2</Subscript> from enstatite to H<Subscript>2</Subscript> fluid under high pressure and temperature     

Ayako Shinozaki  Hiroyuki Kagi  Hisako Hirai  Hiroaki Ohfuji  Taku Okada  Satoshi Nakano  Takehiko Yagi 《Physics and Chemistry of Minerals》2016,43(4):277-285

Stability and phase relations of coexisting enstatite and H₂ fluid were investigated in the pressure and temperature regions of 3.1–13.9 GPa and 1500–2000 K using laser-heated diamond-anvil cells. XRD measurements showed decomposition of enstatite upon heating to form forsterite, periclase, and coesite/stishovite. In the recovered samples, SiO₂ grains were found at the margin of the heating hot spot, suggesting that the SiO₂ component dissolved in the H₂ fluid during heating, then precipitated when its solubility decreased with decreasing temperature. Raman and infrared spectra of the coexisting fluid phase revealed that SiH₄ and H₂O molecules formed through the reaction between dissolved SiO₂ and H₂. In contrast, forsterite and periclase crystals were found within the hot spot, which were assumed to have replaced the initial orthoenstatite crystals without dissolution. Preferential dissolution of SiO₂ components of enstatite in H₂ fluid, as well as that observed in the forsterite H₂ system and the quartz H₂ system, implies that H₂-rich fluid enhances Mg/Si fractionation between the fluid and solid phases of mantle minerals.  相似文献   

Reaction of forsterite with hydrogen molecules at high pressure and temperature     

Ayako?ShinozakiEmail author  Hisako?Hirai  Hiroyuki?Kagi  Tadashi?Kondo  Taku?Okada  Daisuke?Nishio-Hamane  Shin-ichi?Machida  Tetsuo?Irifune  Takumi?Kikegawa  Takehiko?Yagi 《Physics and Chemistry of Minerals》2012,39(2):123-129

High pressure and temperature reactions of a mixture of forsterite and hydrogen molecules have been carried out using a laser heated diamond anvil cell at 9.8–13.2 GPa and ~1,000 K. In situ X-ray diffraction measurements showed no sign of decomposition or phase transitions of the forsterite under these experimental conditions, indicating that the olivine structure was maintained throughout all runs. However, a substantial expansion of the unit cell volume of the forsterite was observed for samples down to ~3 GPa upon quenching to ambient pressure at room temperature. The Raman spectroscopy measurements under pressure showed significant shifts of the Raman peaks of the Si–O vibration modes for forsterite and of the intramolecular vibration mode for H₂ molecules toward a lower frequency after heating. Additionally, no OH vibration modes were observed by Raman and FT-IR spectroscopic measurements. These lines of evidence show that the observed volume expansion in forsterite is not explained by the incorporation of hydrogen atoms as hydroxyl, but suggest the presence of hydrogen as molecules in the forsterite structure under these high pressure and temperature conditions.  相似文献   

Nutrient and Phytoplankton Dynamics in Harima-Nada, Eastern Seto Inland Sea, Japan During a 35-Year Period from 1973 to 2007     

Tetsuya Nishikawa  Yutaka Hori  Satoshi Nagai  Kazutaka Miyahara  Yukinobu Nakamura  Kazuhiro Harada  Minoru Tanda  Takehiko Manabe  Kuninao Tada 《Estuaries and Coasts》2010,33(2):417-427

Long-term monitoring of water quality and phytoplankton was conducted at 19 sampling stations in Harima-Nada, eastern Seto Inland Sea, Japan for 35 years from 1973 to 2007. There were two significant long-term changes, an increase in winter water temperatures of 0.042°C year^?1, and a decrease in dissolved inorganic nitrogen (DIN) from about 10 μM in the 1970s to ~5 μM in the late 1990s due to the reduction in nutrient inputs. DIN concentrations and total phytoplankton cell density were both higher during the 1970s to the early 1980s and then exhibited a significant decrease in the mid 1980s and remained relatively constant thereafter. Diatoms were the dominant phytoplankton group (>90%) over the 35-year period, and there was a dramatic shift from Skeletonema dominance (~70%) to Chaetoceros in the mid 1980s. This shift in diatom species may be attributed to differences in the life cycle of Skeletonema and Chaetoceros and the response to the decrease in DIN concentration.  相似文献   

Redating the onset of burning at Lynch's Crater (North Queensland): implications for human settlement in Australia     

C. S. M. Turney  A. P. Kershaw  P. Moss  M. I. Bird  L. K. Fifield  R. G. Cresswell  G. M. Santos  M. L. Di Tada  P. A. Hausladen  Y. Zhou 《第四纪科学杂志》2001,16(8):767-771

Lynch's Crater preserves a continuous, high‐resolution record of environmental changes in north Queensland. This record suggests a marked increase in burning that appears to be independent of any known major climatic boundaries. This increase is accompanied, or closely followed, by the virtually complete replacement of rainforest by sclerophyll vegetation. The absence of any major climatic shift associated with this increase in fire frequency therefore has been interpreted as a result of early human impact in the area. The age for this increase in burning, on the basis of conventional radiocarbon dating, was previously thought to be approximately 38 000 ¹⁴C yr BP, supporting the traditional model for human arrival in Australia at 40 000 ¹⁴C yr BP Here we have applied a more rigorous pre‐treatment and graphitisation procedure for radiocarbon dating samples from the Lynch's Crater sequence. These new dates suggest that the increase in fire frequency occurred at 45 000 ¹⁴C yr BP, supporting the alternative view that human occupation of Australia occurred by at least 45 000–55 000 cal. yr BP. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Upper Eocene travertine-lacustrine carbonate in the Jianchuan basin,southeastern Tibetan Plateau: Reappraisal of its origin and implication for the monsoon climate     

Aki Sakuma  Akihiro Kano  Yoshihiro Kakizaki  Ryuji Tada  Honbo Zheng 《Island Arc》2021,30(1):e12416

The Asian monsoon is one of the largest climatic systems in the world, but age of its onset has been estimated differently ranging from the late Eocene to the Quaternary. We investigated the sedimentology and stable isotopic compositions of the upper Eocene Jiuziyan Formation, a terrestrial limestone unit in the Jianchuan basin, Yunnan Province in China. This limestone formation is restricted in several localities in the central part of the basin. Previously, this has been characterized as palustrine carbonate and the transition to the sublacustrine deposit of the overlying Shuanghe Formation was interpreted as the appearance of wetter climate during the late Eocene. Our observations of macro- and microfacies revealed sedimentary fabrics indicating rapid CaCO₃ precipitation, such as dendritic calcite and calcified reed stems, which are unlikely to develop in a simple lacustrine setting. High carbonate content (mostly >90 %) and restricted distribution of the Jiuziyan limestone indicate a depositional setting spatially limited and isolated from clastic influx. These findings, together with clearly higher δ¹³C values (−0.7 ‰ to +6.9 ‰) and lower δ¹⁸O values (−14.6 ‰ to −10.5 ‰) than those of the Shuanghe Formation, indicate that the limestone was mainly travertine, carbonate formed from endogenic spring water. The elevated δ¹³C resulted from a large amount of CO₂ degassing from spring water with high pCO₂. In addition, the occurrence of centimeter-scale lamination coupled with cyclic changes in δ¹³C and δ¹⁸O is almost identical with the modern annually-laminated travertine reported from Baishuitai in northern Yunnan Province, implying comparable amplitude of seasonal temperature and precipitation changes to the record of the modern travertine at Baishuitai. Our results do not contradict the previous interpretation of late Eocene wetting and additionally suggest the existence of the late Eocene monsoon climate in the Jianchuan basin.  相似文献   

Improved provenance tracing of Asian dust sources using rare earth elements and selected trace elements for palaeomonsoon studies on the eastern Tibetan Plateau   总被引：2，自引：0，他引：2  

Marion Ferrat  Dominik J. Weiss  Stanislav Strekopytov  Hongyun Chen  Youbin Sun  Ryuji Tada 《Geochimica et cosmochimica acta》2011,75(21):6374-6399

The Asian Monsoon forms an important part of the earth’s climate system, yet our understanding of the past interactions between its different sub-systems, the East Asian and Indian monsoons, and between monsoonal winds and other prevailing wind currents such as the Westerly jet, is limited, particularly in central Asia. This in turn affects our ability to develop climate models capable of accurately predicting future changes in atmospheric circulation patterns and monsoon intensities in Asia. Provenance studies of mineral dust deposited in terrestrial settings such as peat bogs can address this problem directly, by offering the possibility to examine past deposition rates and wind direction, and hence reconstruct past atmospheric circulation patterns. However, such studies are challenged by several issues, most importantly the identification of proxies that unambiguously distinguish between the different potential dust sources and that are independent of particle size. In addition, a single analytical method that is suitable for sample preparation of both dust source (i.e. desert sand, soil) and receptor (i.e. dust archive such as peat or soil profiles) material is desirable in order to minimize error propagation derived from the experimental and analytical work. Here, an improved geochemical framework of provenance tracers to study atmospheric circulation patterns and palaeomonsoon variability in central Asia is provided, by combining for the first time mineralogical as well as major and trace elemental (Sc, Y, Th and the rare earth elements) information on Chinese (central Chinese loess plateau, northern Qaidam basin and Taklamakan, Badain Juran and Tengger deserts), Indian (Thar desert) and Tibetan (eastern Qinghai-Tibetan Plateau) dust sources.Quartz, feldspars and clay minerals are the major constituents of all studied sources, with highly variable calcite contents reflected in the CaO concentrations. Chinese and Tibetan dust sources are enriched in middle REE relative to the upper continental crust and average shale but the Thar desert has a REE signature distinctly different from all other dust sources. There are significant differences in major, trace and REE compositions between the coarse and fine fractions of the surface sands, with the finest <4 μm fraction enriched in Al₂O₃, Fe₂O₃, MnO, MgO and K₂O and the <32 μm fractions in Sc, Y, Th and the REE relative to the coarse fractions. The <4 μm fraction best represents the bulk REE geochemistry of the samples. The provenance tracers Y/∑REE, La/Er, La/Gd, Gd/Er, La/Yb, Y/Tb, Y/La, Y/Nd and to a certain extent the europium anomaly Eu/Eu^∗ (all REE normalized to post-Archean Australian shale, PAAS) are particle size-independent tracers, of which combinations of Y/∑REE, La/Yb, Y/Tb, Y/La and Eu/Eu^∗ can be used to distinguish the Thar desert, the Chinese deserts, the Chinese loess plateau and the Tibetan soils. Their independence upon grain size means that these tracers can be applied to the long-range provenance tracing of Asian dust even when only bulk samples are available in the source region. Combinations of La/Th, Y/Tb, Y/∑REE, Sc/La and Y/Er distinguish the Tibetan soils from the Chinese loess plateau and the Chinese deserts. La/Th and notably Th/∑REE isolate the signature of the Badain Juran desert and the combination of Sc/La and Y/Er that of the Taklamakan desert. The similarity in all trace and REE-based provenance tracers between the northern Qaidam basin and Tengger desert suggests that these two deposits may have a common aeolian source.  相似文献   

Magma discharge variations during the 2011 eruptions of Shinmoe-dake volcano, Japan, revealed by geodetic and satellite observations     

Tomofumi Kozono  Hideki Ueda  Taku Ozawa  Takehiro Koyaguchi  Eisuke Fujita  Akihiko Tomiya  Yujiro J Suzuki 《Bulletin of Volcanology》2013,75(3):1-13

We present precise geodetic and satellite observation-based estimations of the erupted volume and discharge rate of magma during the 2011 eruptions of Kirishima-Shinmoe-dake volcano, Japan. During these events, the type and intensity of eruption drastically changed within a week, with three major sub-Plinian eruptions on January 26 and 27, and a continuous lava extrusion from January 29 to 31. In response to each eruptive event, borehole-type tiltmeters detected deflation of a magma chamber caused by migration of magma to the surface. These measurements enabled us to estimate the geodetic volume change in the magma chamber caused by each eruptive event. Erupted volumes and discharge rates were constrained during lava extrusion using synthetic aperture radar satellite imaging of lava accumulation inside the summit crater. Combining the geodetic volume change and the volume of lava extrusion enabled the determination of the erupted volume and discharge rate during each sub-Plinian event. These precise estimates provide important information about magma storage conditions in magma chambers and eruption column dynamics, and indicate that the Shinmoe-dake eruptions occurred in a critical state between explosive and effusive eruption.  相似文献   

Decrease in anthropogenic nutrients and its effect on the C/N/P molar ratio of suspended particulate matter in hypertrophic Dokai Bay (Japan) in summer     

Kenichiro Hamada  Naoko Ueda  Machiko Yamada  Kuninao Tada  Shigeru Montani 《Journal of Oceanography》2012,68(1):173-182

Biologically important nutrient concentrations in Dokai Bay have declined as a result of reductions in anthropogenic inputs of total nitrogen and total phosphorus. A decrease in nutrient concentrations affects phytoplankton growth, thereby changing the biochemical characteristics of autochthonous particulate matter. We therefore investigated changes in the C/N/P molar ratio of suspended particulate matter (SPM) in the summer, when phytoplankton growth is vigorous, before environmental quality standards (EQSs) were attained (1995–1998) and afterward (2006–2009). We found that the ratio of particulate organic nitrogen (PON) to particulate phosphorus (PP) changed in conjunction with changes in the ratio of dissolved inorganic nitrogen to dissolved inorganic phosphorus (DIP) that resulted from reductions in nutrient loading. Furthermore, we suggest that because the DIP concentration in seawater was high before EQSs were attained, inorganic phosphorus was possibly adsorbed onto SPM. After the attainment of EQSs, however, the DIP concentration fell, and PON/PP was high. Phosphorus limitation of phytoplankton growth in the mouth of the bay may explain the high PON/PP ratios after EQS attainment.  相似文献