Clinoenstatite in volcanic rocks from the Bonin Islands

Multiply-twinned clinoenstatite has been found in andesitic rocks from Chichi-jima and Mukojima in the Bonin Islands.The clinoenstatite occurs as (1) reaction rims around olivine, (2) composite crystals with bronzite, and (3) anhedral phenocrysts rimmed or included by bronzite.The clinoenstatite is chemically characterized by low contents of Ca (less than 0.5 wt.% oxide), Fs (9.2–11.5) and Al (less than 0.6 wt.% oxide) relative to the coexisting bronzite. The partition coefficient, K _{D op} ^cp =(Mg/Fe²⁺)^cp/(Mg/Fe²⁺)^op between coexisting clinoenstatite and bronzite, ranges from 1.02 to 1.32 (average 1.17). The Fe²⁺/Mg+Fe²⁺ ratios of coexisting clinoenstatite and bronzite are different in different rock types, which suggests variable inversion temperatures of protoenstatite to orthopyroxene in boninite.Bronzite phenocrysts in a specimen, ranging from Fs15 to Fs30, coexist with augite phenocrysts, whereas those in the other specimens, ranging from Fs12 to Fs18, do not coexist with augite phenocrysts. These differences in petrographical nature and mineral chemistry among the specimens examined may be due to variations in their quenching stages.The boninite clinoenstatite and bronzite are relatively rich in Ca and Mg, compared with the Papuan and Mariana pyroxenes, which seems to depend upon the rock chemistry.     

Swell-dominant surface waves observed by a moored buoy with a GPS wave sensor in Otsuchi Bay,a ria in Sanriku,Japan

Real-time monitoring of wind and surface waves in Otsuchi Bay, Iwate, Tohoku, Japan, commenced in October 2012, using a mooring buoy with an ultrasonic anemometer and a single-mode GPS wave sensor. Wind and wave data are distributed hourly in real time via the Internet along with a chart of their time series. We analyzed data monitored in the first 3 months in order to assess the variability and occurrence of wind and waves and to elucidate the main reasons for wave variation in Otsuchi Bay. The monitoring data revealed that surface waves in the bay were predominantly affected by swells propagated from the northeastern offshore region and that the wave height was significantly correlated with the component of wind velocity toward Otsuchi Bay in the northeastern offshore region that faces the bay mouth. The offshore wind field was expected to provide information useful for predicting coastal waves in a ria bay in Sanriku such as Otsuchi Bay. However, it should be emphasized that the horizontal distribution of the offshore wind field which has a significant effect on the surface waves in a ria bay depends heavily on the topographic shape of the bay.     

Relationship between canopy height and the reference value of surface conductance for closed coniferous stands

When estimating the dry‐canopy evaporation rate of coniferous stands using the Penman–Monteith equation, it is crucial to determine the reference value of surface conductance G_s. This paper examines the relationship between canopy height and the reference value of G_s based on the maximum value of G_s with a vapour pressure deficit ≥ 1·0 kPa, ?_{s max}. There is a clear correlation between canopy height and ?_{s max} when the projected leaf area index ≥3·0. This suggests that using this relationship will enable more accurate determination of the reference value of G_s for closed stands. Copyright © 2003 John Wiley & Sons, Ltd.     

Geological features indicative of processes related to the hematite formation in Meridiani Planum and Aram Chaos, Mars: a comparison with diagenetic hematite deposits in southern Utah, USA

In order to understand the formation of the few but large, hematite deposits on Mars, comparisons are often made with terrestrial hematite occurrences. In southern Utah, hematite concretions have formed within continental sandstones and are exposed as extensive weathered-out beds. The hematite deposits are linked to geological and geomorphological features such as knobs, buttes, bleached beds, fractures and rings. These terrestrial features are visible in aerial and satellite images, which enables a comparison with similar features occurring extensively in the martian hematite-rich areas. The combination of processes involved in the movement and precipitation of iron in southern Utah can provide new insights in the context of the hematite formation on Mars. Here we present a mapping of the analogue geological and geomorphological features in parts of Meridiani Planum and Aram Chaos. Based on mapping comparisons with the Utah occurrences, we present models for the formation of the martian analogues, as well as a model for iron transport and precipitation on Mars. Following the Utah model, high albedo layers and rings in the mapped area on Mars are due to removal or lack of iron, and precipitation of secondary diagenetic minerals as fluids moved up along fractures and permeable materials. Hematite was precipitated intraformationally where the fluid transporting the reduced iron met oxidizing conditions. Our study shows that certain geological/geomorphological features can be linked to the hematite formation on Mars and that pH differences could suffice for the transport of the iron from an orthopyroxene volcanoclastic source rock. The presence of organic compounds can enhance the iron mobilization and precipitation processes. Continued studies will focus on possible influence of biological activity and/or methane in the formation of the hematite concretions in Utah and on Mars.     

Bacterial growth rate and the relative abundance of bacteria to heterotrophic nanoflagellates in the euphotic and disphotic layers in temperate coastal waters of Sagami Bay,Japan

This study aimed to clarify the vertical differences in bacterial growth and grazing pressure on bacteria by heterotrophic nanoflagellates (HNF) and to identify the controlling factors of bacterial growth in temperate coastal waters of Sagami Bay, Japan. In addition to environmental factors, the annual monthly variations in bacterial growth rate (BGR) and the relative abundance of bacteria to HNF (BA/HNFA) were investigated in the euphotic and disphotic layers between May 2012 and May 2013. Significant vertical differences in BGR and BA/HNFA were evident between the two layers during the thermal stratification times of May to October 2012 and April to May 2013. BGR indicated significantly stronger limitation of bacterial growth in the euphotic layer compared to the disphotic layer. In contrast, significantly lower BA/HNFA was observed in the euphotic layer, suggesting significantly higher grazing pressure on bacteria by HNF. However, significant differences in BGR and BA/HNFA were not observed between the two layers from November 2012 to Match 2013, when the water column was well-mixed vertically due to the cooling and wind-induced mixing of surface water. This study indicates that bacteria in the euphotic layer grow less actively and are more vulnerable to predatory grazing by HNF relative to the disphotic layer during the stratification period. Further, multiple regression analyses indicate that bacterial growth was most controlled by the concentrations of chlorophyll a and dissolved organic carbon in the euphotic and disphotic layers, respectively.     

High nutrients in the coastal area after heavy rain observed in the central Seto Inland Sea in July 2012

Temporary enhancement of the nutrient concentrations in the coastal area was observed after heavy rain in the central Seto Inland Sea in July 2012. After passage of a stationary front accompanied by heavy rain, the river outflow was enhanced, and low salinity and high nutrient concentrations were detected near the mouths of rivers. The offshore salinity and nutrients increased and decreased, respectively, which suggested that a snapshot event, such as heavy rain, could influence the short-term variation of the coastal marine environmental conditions, such as the salinity and nutrient distributions.