Box model analysis of hydrography and behaviour of nitrogen and phosphorus in a eutrophic estuary     

Yasuo Matsukawa  Teruaki Suzuki 《Journal of Oceanography》1985,41(6):407-426

In order to investigate the mechanism of eutrophication in Atsumi Bay which is a shallow and partially mixed estuary, distributions of temperature, salinity and concentrations of nitrogen and phosphorus in all their chemical forms were observed once a month throughout a year. Supplies of freshwater and nutrients are estimated and balances of salt and nutrients are examined using a modified box model. The deduced estuarine hydrography and calculated values of photosynthesis, decomposition, deposition and sedimentation are compared with those obtained byin situ observations and laboratory experiments. It is found that the factors responsible for the appearance of heavy eutrophication include not only the general increase of nutrient supply from land but also nutrient accumulation in the rainy season just before summer, the N/P ratio of the supply from land being favourable for uptake by phytoplankton, formation of semi-closed circulations of the nutrients associated with stratification and vertical circulation of estuarine water, and possibly the inorganic turnover of phosphorus (PO₄-P) under aerobic and anaerobic conditions. The usefulness of the modified box model for obtaining a synoptic understanding of the estuarine system is also demonstrated.  相似文献   

Branching and joining of the Tsushima Current around the Oki Islands     

Osamu Katoh  Kenji Morinaga  Kuniaki Miyaji  Kazuyuki Teshima 《Journal of Oceanography》1996,52(6):747-761

We discussed the branching and joining of the Tsushima Current around the Oki Islands, based on ADCP and CTD measurements carried out in June 1990 by the quadrireciprocal method (Katoh, 1988). The volume transport of the northeastward current northwest of the Izumo Coast was about 2 Sv. The triple-branch structure of the Tsushima Current was obscure there. This northeastward current divided into the eastward and northward currents, with volume transports of 0.5 Sv and 1.5 Sv, respectively, at the west entrance of the Oki Strait. Most of the first branch of the Tsushima Current seemed to be separated again from the other confluent branches and to pass through the Oki Strait as this eastward current. The northward current was composed of the second and the third branches of the Tsushima Current. It detoured the Oki Islands, and almost all of it returned south to the Tajima Coast. In the vicinity of the Tajima Coast, the eastward current was abruptly strengthened through the confluence of the southward one which was originated from the northward current west of the Oki Islands. This showed that the first branch finally joined the compound of the second and the third branches detouring the Oki Islands. Between the Oki Strait and the Tajima Coast, the two-layer structure of currents was clearly found.  相似文献   

Nitrogen budget in Tokyo Bay with special reference to the low sedimentation to supply ratio     

Yasuo Matsukawa  Katsuyuki Sasaki 《Journal of Oceanography》1990,46(2):44-54

In order to determine why the sedimentation to supply ratio of nutrients in Tokyo Bay is markedly small, the nitrogen budget was investigated for 1979, when a systematic and continuous observation of flow and salinity was carried out. The data were analyzed by use of a simple advective-diffusive box model and dissolved oxygen balance in the lower layer was also examined. The calculated values of two-layer flow, settling, primary production, mineralization, denitrification, and dissolved oxygen consumption were comparable to those observed.The factors making the sedimentation to supply ratio makedly small were summarized as: 1) a strong and stable two-layer flow generated by a large freshwater supply, 2) further intensification of this two-layer flow by the northern winter monsoon, 3) coincidence of the discharge region with the supply region of nutrients caused by the transverse inclination of the interface, probably due to the earth's rotation. 4) effective discharge of nutrients from the bay due to a strong tidal flow and a possible cyclonic tidal residual circulation in the inner bay mouth, 5) incomplete consumption of nutrient salts by phytoplankton in the upper layer even in the most productive season, and 6) possible denitrification in the anaerobic bottom water in summer and in the bottom sediment itself throughout the year in the inner bay.  相似文献   

The content of selenium and its chemical form in sea water   总被引：1，自引：0，他引：1  

Yukio Sugimura  Yoshimi Suzuki  Yasuo Miyake 《Journal of Oceanography》1976,32(5):235-241

By using the new fluorometric method of determination of the total selenium ( Se), Se (IV) and Se (VI), the content of selenium in sea weter was determined in the western North Pacific. Results showed that the content of Se in surface water ranged from 0.06 to 0.12g l^–1, while in deeper layers, the content increased to 0.20g l^–1. It was found that Se (IV) showed rather uniform distribution with depth, while Se (VI) increased with depth to about three times that in the surface. The ratio of Se (IV) to the Se ranged from 0.5 to 0.8 in the surface and 0.4 to 0.6 in the deep. The coexistence of the hexa- and tetravalent ions of selenium was confirmed both in surface and deep layers. Some results of observations on the content of selenium in the coastal areas of Japan were also reported.  相似文献   

Distributions and upward fluxes of particulate matter near bottom in the southeastern Bering Sea Shelf     

Masahiro Kajihara  Tsutomu Morinaga  Akihiko Sekine 《Journal of Oceanography》1986,42(5):389-401

Time-series measurements of temperature, salinity, suspended matter and beam attenuation coefficient () were measured at four hour intervals for about two days in June/ July 1982 in the middle shelf region and the coastal region of the southeastern Bering Sea. Current meters were also moored at the same locations.Depth-time distributions of indicated that profiles of suspended matter resulted from a combined process of resuspension of underlying sediments and sinking of suspended particles. Average-values for all measurements for particles revealed that the upward transport of particles due to resuspension formed a boundary layer, with a thickness apparently related to scalar speed. The average-profiles of the particle volume concentration were assumed to result from a balance between the sinking and diffusive flux of particles under a steady state, and the upward fluxes were calculated. Within the boundary layer, values of the upward fluxes of particulate organic matter linearly decreased with the logarithm of distance from the bottom. Fluxes of organic carbon at the upper edge of the boundary layer were 0.375 gC·m^–2·day^–1 in the middle shelf region (18 m above the bottom, bottom depth=78m) and 0.484gC·m^–2·day^–1 in the coastal region (25 m above the bottom, bottom depth=33m), and fluxes of nitrogen in both regions were 0.067 gN·m^–2·day^–1. The flux of organic carbon obtained in the middle shelf region (18 m above the bottom) agreed approximately with the flux (0.416 gC·m^–2·day^–1) calculated by substituting primary production data into the empirical equation of Suess (1980).  相似文献   

Ammonium uptake kinetics and interactions between nitrate and ammonium uptake inChattonella antiqua     

Yasuo Nakamura 《Journal of Oceanography》1985,41(1):33-38

Ammonium uptake kinetics and interactions between nitrate and ammonium uptake were examined inChattonella antiqua. After the addition of ammonium to the culture ofC. antiqua, the ammonium concentration decreased linearly with time. The ammonium uptake rate as a function of ammonium concentration followed the Michaelis-Menten equation; the maximal uptake rate was 2.0 pmol cell^–1hr^–1 and the half saturation constant, 2.2M. Although the ammonium uptake was not affected by nitrate, uptake of nitrate was rapidly (15min) suppressed by ammonium and a 50% reduction in nitrate uptake was observed at an ammonium concentration ofca. 2M.  相似文献   

Hydrography and budget of dissolved total nitrogen and dissolved oxygen in the stratified season in Mikawa Bay,Japan     

Teruaki Suzuki  Yasuo Matsukawa 《Journal of Oceanography》1987,43(1):37-48

Distributions of salinity, dissolved total nitrogen (DTN) and dissolved oxygen (DO) were observed once a month throughout a year in Mikawa Bay, one of the most eutrophic bays in Japan. Supply of freshwater, DTN and DO from the land and precipitation was estimated. Hydrography, circulation and transformation of DTN and DO during the stratified period were investigated simultaneously by a two-layered box model analysis dividing the bay into five boxes. The two-layered circulation was confirmed. In the upper layer of the river mouth regions, a high production of particulate organic nitrogen (PON) due to the strong upwelling together with the river inflow was found. On the other hand, in the lower layer of the bay mouth region, a high deposition of PON due to weak upwelling and sometimes downwelling and a high decomposition of PON due to the inflow of DO abundant water were also found. The reason why the eutrophication is more severe in the eastern part than in the north-western part of the bay is discussed.  相似文献   

新疆阿尔泰山南部富蕴右旋走滑断裂带晚第四纪错断水系的遥感分析研究   总被引：2，自引：2，他引：0       下载免费PDF全文

张之武  付碧宏  Yasuo Awata 《第四纪研究》2008,28(2):273-279

富蕴断裂带位于阿尔泰山南侧,横切阿尔泰山褶皱带南缘及额尔齐斯深断裂,是一条呈北北西向展布的右旋走滑断裂带。沿断裂带发育一系列错断水系、错断冲积扇、挤压脊、走滑拉分盆地等反映右旋走滑活动的典型构造地貌标志。本研究在高分辨率遥感图像和数字高程模型分析的基础上,结合野外实地构造地貌测量,对沿富蕴断裂带发育的系统错断水系特征进行了详细分析研究。研究结果表明,沿富蕴断裂带发育不同级别的错断水系,大致可划分为6级:1931年地震形成的冲沟;90m左右断距的错断水系;150m左右断距的错断水系;500m左右断距的错断水系;1500m左右断距的错断水系;2000m以上断距的错断水系。同时,结合研究区及邻区的第四纪冰川资料讨论了不同级别水系可能形成时间:恰尔沟三级支流可能形成时间为末次冰期Ⅲ阶段末期,约20ka;恰尔沟二级支流可能形成时间为末次冰期Ⅰ阶段末期,约120ka;恰尔沟一级支流可能形成于该地区冰川广泛消融的倒数第2次冰期的Ⅱ阶段末期,约为250ka;恰尔沟、水磨沟、白杨沟、乌铁布拉克河、卡布尔特河等可能形成于倒数第3次冰期Ⅱ阶段末期,约为360ka。最后,我们估算出富蕴断裂带晚第四纪以来的平均右旋走滑速率为1.46～4.99mm/a。  相似文献   

Evaluation of change in subsurface thermal environment due to groundwater flow in the Tokyo Lowland,Japan     

Akinobu Miyakoshi  Takeshi Hayashi  Atsunao Marui  Yasuo Sakura  Shinichi Kawashima  Masafumi Kawai 《International Journal of Earth Sciences》2008,97(2):401-411

Information on the distribution of subsurface temperature and hydraulic heads at 24 observation wells in and around the Tokyo Lowland, the eastern part of the Tokyo Metropolitan area, were examined to make clear the relationship between groundwater and the subsurface thermal environment in the urban area. Minimums in temperature–depth logs due to subsurface temperature increasing at shallow parts were recognized in 21 wells. This fact shows subsurface temperature is affected by ground surface warming in almost all of this area. Deeper than minimums, where the effects of surface warming became relatively small, regional variation is observed as follows: high temperatures are shown in the central part to the southern part, and low temperatures shown in the inland to eastern part. The high temperature area corresponds to an area where the lower boundary of groundwater flow is relatively shallow. This area corresponds also to an area with severe land subsidence resulting from excessive groundwater pumping. It is considered that this high temperature area is formed by the effects of upward groundwater flow affected by hydrogeological conditions and pumping. On the other hand, a comparison between past data (1956–1967) and present data (2001–2003) revealed widespread decreasing temperature in the inland area. This is explained by downward groundwater flow based on an analysis of temperature–depth logs. This fact suggests that subsurface temperature is not only increasing from the effects of surface warming but also decreasing from the effects of groundwater environment change due to pumping.  相似文献   

Ecologic and taxonomic diversification in the Mesozoic brackish-water bivalve faunas in Japan, with emphasis on infaunalization of heterodonts     

Yasuo Kondo  Takeshi Kozai  Naoki Kikuchi  Kazuhiro Sugawara 《Gondwana Research》2006,10(3-4):316-327

Mesozoic brackish-water bivalve faunas in Japan diversified in three steps: at the beginning of the Early Jurassic, Early and Late Cretaceous. The Hettangian Niranohama Fauna in northeastern Honshu represents the establishment of a heterodont-dominated brackish-water fauna that persisted until the early Late Cretaceous. No similar composition is known from the Triassic. The infauna consists mostly of non-siphonate and some short-siphonate heterodonts, while the epifauna is represented by diverse pteriomorphian families. In the Early Cretaceous Tetori Group in central Honshu, the long-siphonate heterodonts Tetoria (Corbiculidae) and the semi-infaunal soft-bottom oyster Crassostrea appeared. The evolutionary diversification of the latter, known as the most important element of modern brackish-water faunas, may thus originate at that time. In the early Late Cretaceous (Cenomanian) of the Goshoura and Mifune Groups in west Kyushu, several euryhaline deep-burrowing heterodont families, such as Veneridae and Tellinidae, further diversified in the brackish and marine environments. The Late Cretaceous is characterized by massive shell biolithic beds in which large Crassostrea species are common, a feature common for Cenozoic brackish-water faunas. The long-term changes in the composition of the brackish-water faunas in Japan represents thus an evolutionary record, irrespective of the severe physiological and environmental conditions imposed on the highly conservative nature of the fauna.  相似文献