Seasonal Changes in Mayfly Communities and Abundance in Relation to Water Physicochemistry in Two Rivers at Different Elevations in Northern Peninsular Malaysia     

Suhaila Abdul Hamid  Mohd Ravi Che Salmah  Hamady Dieng  Abu Hassan Ahmad  Tomomitsu Satho  Fumio Miake 《湿地科学》2011,9(3):240-250

A field study was performed at rivers in Gunung Jerai forest reserve(Kedah,Malaysia) to assess seasonal changes in mayfly community structure and abundance in relation to altitude and water physicochemistry.Rivers at lower(Batu Hampar River) and higher(Teroi River) elevations were visited through dry and wet seasons in September 2007 to August 2008.Monthly visits were made to 20 sites on each river,and water and aquatic insects were sampled using D-pond aquatic nets.Water was warmer,more acid,and more turbid in Teroi River during wet season.Ammonia was the only nutrient exhibiting significant seasonal variations(greater during wet season).Chemical oxygen demand content was higher in Teroi River where biochemical oxygen demand content was low during wet season.Species richness was higher in Batu Hampar River,but displayed seasonal variations only in Teroi River.Among the eight families encountered,Baetidae was the commonest.Baetid abundance was usually high during wet season,and those belonging to the dominant genus(Baetis) were more abundant in Teroi River.Heptageniidae was the second commonest family;its predominant genus,Thalerospyrus was more abundant in Teroi River during dry season.Caenidae,Leptophlebiidae and Oligoneuriidae were only found in Batu Hampar River where their abundances peaked during dry season,i.e.,Habrophlebiodes sp.and Isonychia sp.Ephemerellidae and Teloganodidae occurred only in Teroi River,with the first found only during dry season.Mayflies were recorded under very distinct physicochemical conditions,illustrating their potential usefulness for assessing water quality.Caenids,leptophlebids,oligoneurids ephemerellids and teloganodids seem to be particularly sensitive to temperature,acidity,turbidity,chemical oxygen demand and biochemical oxygen demand,parameters that varied with river altitude.  相似文献   

Morphological Features of Co-Rich Manganese Deposits and Their Relation to Seabed Slopes   总被引：7，自引：0，他引：7  

Tetsuo Yamazaki  Rahul Sharma 《Marine Georesources & Geotechnology》2000,18(1):43-76

The morphological features associated with Co-rich manganese deposits, the size variations of nodules, and the occurrence of different substrates have been analyzed, to evaluate the influence of various seabed slope angles on the distribution of these features. The coverage and size of the crusts depend on their surface morphology and seabed topography, resulting in cobble-type, lineated, or step-like outcrops. Small nodules (1 - 4 cm in diameter) dominate all seabed slopes, with a few locations having nodules ranging from 1 to 8 or 1 to 10 cm. Sediments invariably occur as substrates for nodules and as cover for crusts, their coverage being inversely proportional to that of the nodules and crust outcrops. Steeper seafloor areas have large crust outcrops exposed with no or few nodules and sediments associated with them. The intermediate slopes have a combination of nodules, sediments, and crusts in various proportions, depending on topography and gradient. Large-scale nodule occurrences, followed by sediment fields and crust outcrops on seabed slopes of greater than 3 degrees, 3 - 7 degreees, and less than 15 degrees, respectively, represent typical morphological distribution zones of the Co-rich manganese deposits on a seamount in the central Pacific Ocean. A transition zone between nodule-dominated fields and large crust outcrops occurs for slopes from 7 degrees to 15 degrees. This detailed study on distribution of Co-rich deposits gives a better understanding for purposes of their exploitation.  相似文献   

EVAPOTRANSPIRATION OF LOW-LYING PRAIRIE WETLAND IN MIDDLE REACHES OF HEIHE RIVER IN NORTHWEST CHINA     

Yusuke YAMAZAKI  Jumpei KUBOTA 《中国地理科学(英文版)》2005,15(4):325-329

1 IN T R O D U C T IO NW aterbalance and interactions are foundation to utilizew aterresources rationally in arid inland river basins inC hina (W U etal.,2005).W ateravailability in those ar-eas m ay be the m ain constraint to poverty alleviation,publiche…  相似文献   

Possible observational evidence for the θ⁻² angular distribution of the opening half-angle of gamma-ray burst jets     

Daisuke Yonetoku  Ryo Yamazaki  Takashi Nakamura  Toshio Murakami 《Monthly notices of the Royal Astronomical Society》2005,362(3):1114-1118

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A strong motion database for the chiba seismometer array and its engineering analysis     

Tsuneo Katayama  Fumio Yamazaki  Shigeru Nagata  Lin Lu  Turgay Turker 《地震工程与结构动力学》1990,19(8):1089-1106

A three-dimensional seismometer array was installed in the Chiba Experiment Station of the Institute of Industrial Science, University of Tokyo in 1982. The array system consists of 44 three-component accelerometers densely placed both on the ground surface and in boreholes. A complementary system for the measurement of ground and buried pipe strains was also installed at the same site. The array system has been successfully in operation, and more than 160 earthquakes have been recorded. Considering a wide use of these seismograms, the Chiba array database has recently been created comprising twenty-seven major events. This paper describes the Chiba array system and its strong motion database. Results of engineering analysis using the selected records are also presented.  相似文献   

Application of a 3-D chemical fate prediction model (FATE3D) to predict dioxin concentrations in the Tokyo Bay     

Norihiro Kobayashi  Tomomi Eriguchi  Kisaburo Nakata  Shigeki Masunaga  Fumio Horiguchi  Junko Nakanishi 《Estuarine, Coastal and Shelf Science》2006,70(4):621

A 3-D chemical fate prediction model (FATE3D) was applied to predict the dioxin concentrations in the seawater of Tokyo Bay, Japan. The simulations were carried out for a period of one year (from September 2002 to August 2003). Parameters such as meteorological data, flow field conditions, concentrations and sinking rates of organic particulate matter, initial and boundary conditions, and loading fluxes and physico-chemical properties of dioxins were used as the model inputs.The simulation results compared favorably with the field measurements of dioxin concentrations in the bay for both the particulate and dissolved phases, indicating the validity and predictive capability of the model. Furthermore, the differences in the seasonal cycles and distributions between the particulate- and dissolved-phase dioxins in the bay were estimated from the simulation results.However, the particulate-phase dioxin concentrations in the bottom layers (+1 m from the bottom) were underestimated, probably because the resuspension process was not taken into account in the model. The improvement of the model's predictive capability, including the resuspension process, shall be the focus of our next study.  相似文献   

Observations of a Kelvin-Helmholtz Billow in the Ocean     

Hua Li  Hidekatsu Yamazaki 《Journal of Oceanography》2001,57(6):709-721

We identified a Kelvin-Helmholtz billow from vertical turbulence velocity and instantaneous heat flux signals obtained from airfoil shear probes and thermistors mounted on a research submarine. The vertical turbulence velocity indicates that the horizontal scale of the billow was about 3.5 m. The spectral slope of the vertical turbulence velocity component is close to −2, revealing the flow is two-dimensional. We show a remarkable agreement between the length scales of the observed billow and those computed from direct numerical simulations based on similar conditions. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

On the Concentrations of the Dissolved Chemical Elements in the Estuary Water of the Chikugogawa River     

Iwao Hosokawa  Fumio Ohshima  Norihiko Kondo 《Journal of Oceanography》1970,26(1):1-5

When river water mixes with sea water in estuary area, the concentrations of the dissolved element in river water may be changed by either a simple physical mixing process or some complex chemical processes. It has been clarified in the Chikugogawa River estuary area that the change in concentrations of SO ₄ ²⁻ , BO ₃ ³⁻ , Mg²⁺, Ca²⁺ and F⁻ is only due to the mixing process but the change in concentrations of SiO ₃ ²⁻ and Al³⁺ is due to the chemical process in addition to the mixing process.   相似文献   

A dataset of continental river discharge based on JRA-55 for use in a global ocean circulation model     

Tatsuo Suzuki  Dai Yamazaki  Hiroyuki Tsujino  Yoshiki Komuro  Hideyuki Nakano  Shogo Urakawa 《Journal of Oceanography》2018,74(4):421-429

A dataset of historical river discharge into oceans was created using the CaMa-Flood global river routing model and adjusted runoff from the land component of JRA-55. The major rivers were well resolved with a 0.25° horizontal resolution. The total runoff on each drainage basin exhibits a distinctive bias on decadal time scales. The input runoff data were modified using 5-year low-pass-filtered multiplicative factors to fit the annual mean climatology and decadal variations in the reference dataset. The model incorporated data from 1958 to 2016. The yearly and seasonal variations of the major rivers are well represented by the model.  相似文献   

Accelerated continental-scale snowmelt and ecohydrological impacts in the four largest Siberian river basins in response to spring warming     

Kazuyoshi Suzuki  Tetsuya Hiyama  Koji Matsuo  Kazuhito Ichii  Yoshihiro Iijima  Dai Yamazaki 《水文研究》2020,34(19):3867-3881

River runoff from the four largest Siberian river basins (the Ob, Yenisei, Lena, and Kolyma) considerably contributes to freshwater flux into the Arctic Ocean from the Eurasian continent. However, the effects of variation in snow cover fraction on the ecohydrological variations in these basins are not well understood. In this study, we analysed the spatiotemporal variability of the maximum snow cover fraction (SCF_max) in the four Siberian river basins. We compared the SCF_max from 2000 to 2016 with data in terms of monthly temperature and precipitation, night-time surface temperatures, the terrestrial water storage anomaly (TWSA), the normalised difference vegetation index (NDVI), and river runoff. Our results exhibit a decreasing trend in the April SCF_max values since 2000, largely in response to warming air temperatures in April. We identified snowmelt water as the dominant control on the observed increase in the runoff contribution in May across all four Siberian river basins. In addition, we detected that the interannual river runoff was predominantly controlled by interannual variations in the TWSA. The NDVI in June was strongly controlled by the timing of the snowmelt along with the surface air temperature and TWSA in June. The rate of increase in the freshwater flux from the four Siberian rivers decreased from 2000 to 2016, exhibiting large interannual variations corresponding to interannual variations in the TWSA. However, we identified a clear increase trend in the freshwater flux of ~4 km³/year when analysing the long-term 39-year historical record (1978–2016). Our results suggest that continued global warming will accelerate the transition towards the earlier timing of snowmelt and spring freshwater flux into the Arctic Ocean. Our findings also highlight the effects of earlier snowmelt on ecohydrological changes in the Northern Hemisphere.  相似文献