Step-like temperature fluctuations associated with inverted ramps in a stable surface layer   总被引：1，自引：0，他引：1  

Tokio Kikuchi  Osamu Chiba 《Boundary-Layer Meteorology》1985,31(1):51-63

Ensemble averages of temperature before and after step-like temperature fluctuations reveal the presence of inverted ramps in a stable surface layer. Normalized frequency of upward steps increases with increasing stability, whereas normalized magnitude of the temperature step decreases with stability and becomes constant at about R _i = 1. These results suggest that the significance of temperature steps increases as stability increases. In moderate stability, the temperature pattern shows a gradual decrease after an upward step, which can be called a time-inverted ramp. Descending air and large downward heat flux are observed in a time-inverted ramp, suggesting a contribution from an ordered motion in wind. On the other hand, the temperature steps are related to gravity waves in strong stability.  相似文献   

Photosynthesis-irradiance relationship of phytoplankton and primary production in the vicinity of Kuroshio warm core ring in spring     

Ken Furuya  Osamu Hasegawa  Takashi Yoshikawa  Satoru Taguchi 《Journal of Oceanography》1998,54(5):545-552

The light-saturated maximum value (P ^B _max) and initial slope (α) of the photosynthesis-irradiance (P-E) curve were examined in a warm streamer, a cold streamer and a warm core ring off the Sanriku area in the subarctic western North Pacific Ocean during an ADEOS/OCTS Sanriku field campaign in early May 1997. BothP ^B _max and α were within the ranges of temperate populations. A regional difference was apparent inP ^B _max: populations in the warm streamer tended to show higher value ranging between 1.92 and 4.74 mgC (mgChla)⁻¹h⁻¹ than those in the cold streamer and the warm core ring (1.35–2.87 mgC (mgChla)⁻¹h⁻¹). A depth variation was also observed in α in both the warm streamer and the warm core ring: shallow populations tended to have lower α than deep populations. The depth variations in bothP ^B _max and α resulted in a lower light intensity of the light saturation in a deeper population than that of a shallower one. These depth-related variations in the P-E parameters were likely a manifestation of “shade-adaptation” of photosynthesis. Photoinhibition was not observed over in situ surface light intensity varying below ca 1600 μmol photon m⁻²s⁻¹. Water-column primary productivity was biooptically estimated to be 233 to 949 mgC m⁻²d⁻¹ using vertical distributions of the P-E parameters, chlorophylla, phytoplankton light absorption and underwater irradiance. Applicability of surface data sets for estimation of water-column productivity is discussed.  相似文献   

Phytoremediation of shallow organically enriched marine sediments using benthic microalgae     

Yamamoto T  Goto I  Kawaguchi O  Minagawa K  Ariyoshi E  Matsuda O 《Marine pollution bulletin》2008,57(1-5):108-115

We examined whether replantation of benthic microalgae (BMA) can remediate shallow organically enriched sediment. Nitzschia sp., the dominant species in the tested area (Hiroshima Bay, Japan), was isolated and mass cultured, then replanted in the same area. Changes in the condition of the sediment were monitored for five months. During the study period, we observed an increase in redox potential (ORP) and a decrease in acid-volatile sulfide (AVS) in the experimental area, indicating that the sediment condition changed from reduced to oxic. Organic matter in the sediment, represented by chemical oxygen demand (COD), ignition loss (IL) and organic nitrogen (ON) decreased significantly, while inorganic nutrients (ammonia and phosphate) increased in the interstitial water. These changes imply that oxygen produced by the replanted BMA may have enhanced aerobic bacterial activity, accelerating the decomposition of organic matter. Thus, replantation of BMA shows potential as a novel and promising "phytoremediation" method for organically enriched sediment.  相似文献   

Process of the Tsushima Current formation revealed by ADCP measurements in summer   总被引：1，自引：0，他引：1  

Osamu Katoh  Kazuyuki Teshima  Osamu Abe  Hitoshi Fujita  Kuniaki Miyaji  Kenji Morinaga  Norihisa Nakagawa 《Journal of Oceanography》1996,52(4):491-507

In order to clarify detailed current structures over the continental shelf margin in the East China Sea, ADCP measurements were carried out in summers in 1991 and 1994 by the quadrireciprocal method (Katoh, 1988) for removing diurnal and semidiurnal tidal flows from observed flows, together with CTD measurements. We discussed the process of the Tsushima Current formation in the East China Sea. The Tsushima Current with a volume transport of 2 Sv (1 Sv=10⁶ m³s^–1) was found north of 31°N. A current with a volume transport of 0.4 Sv was clearly found along the 100 m isobath. Between the Kuroshio and the current along the 100 m isobath, southeastward component of velocity was dominant compared to northwestward one. Four eastward to southeastward currents were found over the sea bed shallower than 90 m depth. Total volume transport of these four currents was 1 Sv, and they seemed to be originated from the Taiwan Strait. Intrusion of offshore water into the inner shelf northwest of Amami Oshima was estimated to have a volume transport of 0.6 Sv. It is concluded that the Tsushima Current is the confluence of these currents over the continental shelf margin with the offshore water intruding northwest of Amami Oshima.  相似文献   

基于EPMA的耳石Sr：Ca比分析及其在鱼类生活履历反演中的应用实例研究   总被引：4，自引：0，他引：4  

窦硕增  横内一樹  于鑫  曹亮  大竹二雄  塚本勝巳 《海洋与湖沼》2011,42(4):512-520

利用基于电子探针（EPMA）的耳石Sr：Ca比和Sr含量分析方法研究了长江口水域刀鲚、凤鲚、带鱼和长吻鲍的生活履历及生活史型。结果发现,刀鲚中除存在淡海水洄游性个体生活史型外。还存在出生并生活于河口或近海的非洄游性个体生活史型,其平均耳石Sr：Ca比在不同水环境履历的基准值为：淡水〈2．0×10^-3、河口（3．5—6...  相似文献   

Middle Layer Intrusion as an Important Factor Supporting Phytoplankton Productivity at a Tidal Front in Iyo Nada, the Seto Inland Sea, Japan     

Tamiji Yamamoto  Toshiya Hashimoto  Hidetaka Takeoka  Tenji Sugiyama  Osamu Matsuda 《Journal of Oceanography》2000,56(2):131-139

Field observations were conducted to examine the processes governing the phytoplankton distribution and photosynthetic activity in and around a tidal front formed in Iyo Nada, the Seto Inland Sea, Japan. The existence of a middle layer intrusion, which, it has been suggested, moves from the mixed region to the stratified region of the tidal front, was ascertained by the phytoplankton distribution in addition to a T-S diagram. Skeletonema costatum, which originally inhabited the mixed region, was used as the indicator to reveal the intrusion. However, the tip of water containing the S. costatum population did not extend deeply into the stratified region. The velocity of the intrusion seemed to be slow enough to make biological processes, such as nutrient uptake by phytoplankton and subsequent growth, as well as the decrease in cell density due to zooplankton grazing, dominate during the transportation. The patchy distribution of copepod nauplii implied that grazing has an influence on the distribution pattern of phytoplankton. The location of high photosynthetic activity did not coincide spatially with the center of high phytoplankton biomass, suggesting the importance of these biological processes. Therefore, it is considered that the middle layer intrusion plays a role as an inducer of subsequent biological processes at the tidal front by not only supplying nutrients from the mixed region but also by increasing the vertical diffusivity.  相似文献   

The Role of Suspended Oyster Culture on Nitrogen Cycle in Hiroshima Bay   总被引：1，自引：0，他引：1  

Putth Songsangjinda  Osamu Matsuda  Tamiji Yamamoto  Narasimmalu Rajendran  Hajime Maeda 《Journal of Oceanography》2000,56(2):223-231

The predominance of bivalves affects the cycle of materials in the coastal ecosystem. In the present study, the role of suspended oyster culture on the nitrogen cycle was demonstrated for the northern Hiroshima Bay. The nitrogen cycle was considered as two systems, (1) the primary production (PP) system and (2) the oyster culture (OC) system. The results show that about 26% of N productivity was supplied to process by cultured oysters in the OC system. This process varies seasonally due to the seasonal variations of PON, physiological activities and biomass of oysters. The N processing rates were found to be high in summer and low in winter. The biodeposition and excretion of N in the OC system are 3.0 and 2.1 ton N d^–1, while the natural sedimentation rate and N regeneration in the PP system are 8.3 and 18.0 ton N d^–1, which indicates that the PP system is a major system regenerating N in the water column. The release of total dissolved N from the bottom to the water column is about 8.3 ton N d^–1. The amount of N harvested as oyster product was about 1.3 ton N d^–1, which is about 10% of daily N loading in north Hiroshima Bay. According to the N cycle developed in the present study, the results suggest the significant role of suspended oyster culture on the nitrogen cycle in Hiroshima Bay. In addition, our results indicate that oyster production was efficiently harvested, suggesting that oyster culture could probably be used as a tool to remove N from Hiroshima Bay.  相似文献   

Surface current structure of the Tsushima Warm Current region in the Japan Sea derived by satellite-tracked surface drifters     

Tatsuro Watanabe  Daisuke Simizu  Kou Nishiuchi  Toru Hasegawa  Osamu Katoh 《Journal of Oceanography》2009,65(6):791-801

We examined the surface current structure in the Tsushima Warm Current (TWC) region of the Japan Sea based on a dataset from satellite-tracked surface drifters, including our new deployments during 2004–2008. The gridded mean current velocity and mean kinetic energy (KE) fields calculated from all available drifter data revealed the structure and seasonality of the three branches of the TWC. By comparing the eddy kinetic energy (EKE) field to the KE field, we found four regions where the ratio of EKE to KE was high. In particular, this ratio became extremely high east of the Oki Islands located between the first branch of the TWC (FBTWC) and the second branch of the TWC (SBTWC). Our analysis suggests that the generation of alternate warm and cold eddies east of the Oki Island induced this high ratio. The occurrence of a warm or cold eddy was related to the route—either nearshore or offshore—of the SBTWC. When the offshore route of the SBTWC became dominant, a warm eddy was frequently generated east of the Oki Islands. In contrast, when the nearshore route of the SBTWC became dominant, a cold eddy was more likely to be generated.  相似文献   

Comparing management of recreational Pagrus fisheries in Shark Bay (Australia) and Sagami Bay (Japan): Conventional catch controls versus stock enhancement     

Ronald W.D. Mitchell  Osamu Baba  Gary Jackson  Tatsuya Isshiki 《Marine Policy》2008

This paper compares the management of recreational fisheries for pink snapper (Pagrus auratus) in the inner gulfs of Shark Bay (Australia) and the closely related red sea bream (Pagrus major) in Sagami Bay (Japan). Fishing and other factors have resulted in population declines of these species in both regions. In response, fishery managers have employed contrasting management, more conventional catch controls in Shark Bay and stock enhancement in Sagami Bay. Although recreational harvest levels were higher than commercial levels in both fisheries, the driving mechanisms are comparatively different due to historical, social, economic and political issues in the respective locations.  相似文献   

Tributyltin in blood of marine fish collected from a coastal area of northern Kyushu, Japan     

Miki S  Ikeda K  Oba Y  Satone H  Honda M  Shimasaki Y  Onikura N  Arakawa O  Oshima Y 《Marine pollution bulletin》2011,62(11):2533-2536

We investigated levels of the pollutant tributyltin (TBT) in blood of pufferfishes (six species), Japanese sea perch, red sea bream, Japanese common goby, Japanese flounder, rockfish, conger eel, and sea mullet collected off the coast of northern Kyushu, Japan. We found considerable levels of TBT (1.4-190 ng/mL) accumulated in the blood of these fish. Blood TBT concentrations were 1.3-22.5 times liver concentrations and 4.9-78 times muscle concentrations, except in conger eel and mullet. We detected TBT (16-111 ng/mL-blood) in the plasma of the fine-patterned puffer (Takifugupoecilonotus) year-round, without any apparent seasonal trend. These results suggest that fish inhabiting coastal areas of Kyushu, Japan, continue to be contaminated with TBT.  相似文献