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81.
Two processes are generally explained as causes of temporal changes in the stoichiometric silicon/nitrogen (Si/N) ratios of
sinking particles and of nutrient consumption in the surface water during the spring diatom bloom: (1) physiological changes
of diatom under the stress of photosynthesis of diatom and (2) differences of regeneration between silicon and nitrogen. We
investigated which process plays an important role in these changes using a one-dimensional ecosystem model that explicitly
represents diatom and the other non-silicious phytoplankton. The model was applied to station A7 (41°30′ N, 145°30′ E) in
the western North Pacific, where diatom regularly blooms in spring. Model simulations show that the Si/N ratios of the flux
exported by the sinking particles at 100 m depth and of nutrient consumptions in the upper 100 m surface water have their
maxima at the end of the spring diatom bloom, the values and timings of which are significantly different from each other.
Analyses of the model results show that the differences of regeneration between silicon and nitrogen mainly cause the temporal
changes of the Si/N ratios. On the other hand, the physiological changes of diatoms under stress can hardly cause these temporal
changes, because the effect of the change in the diatom's uptake ratio of silicon to nitrogen is cancelled by that in its
sinking rate. 相似文献
82.
Several large deployments of neutrally buoyant floats took place within the Antarctic Intermediate (AAIW), North Atlantic Deep Water (NADW), and the Antarctic Bottom Water (AABW) of the South Atlantic in the 1990s and a number of hydrographic sections were occupied as well. Here we use the spatially and temporally averaged velocities measured by these floats, combined with the hydrographic section data and various estimates of regional current transports from moored current meter arrays, to determine the circulation of the three major subthermocline water masses in a zonal strip across the South Atlantic between the latitudes of 19°S and 30°S. We concentrate on this region because the historical literature suggests that it is where the Deep Western Boundary Current containing NADW bifurcates. In support of this notion, we find that a net of about 5 Sv. of the 15–20 Sv that crosses 19°S does continue zonally eastward at least as far as the Mid-Atlantic Ridge. Once across the ridge it takes a circuit to the north along the ridge flanks before returning to the south in the eastern half of the Angola Basin. The data suggest that the NADW then continues on into the Indian Ocean. This scheme is discussed in the context of distributions of dissolved oxygen, silicate and salinity. In spite of the many float-years of data that were collected in the region a surprising result is that their impact on the computed solutions is quite modest. Although the focus is on the NADW we also discuss the circulation for the AAIW and AABW layers. 相似文献
83.
With the development of high-resolution multibeam echosounder systems (MBES) for surveying shallow-water areas a new tool is available to monitor rapid changes in seabed morphology as, e.g., caused by the dumping of dredge spoil in coastal waters. In this study, four data sets of repeated bathymetric surveys with a MBES were processed and analyzed. The data were collected in a 1.94-km2 dumping site in the outer Weser Estuary (German Bight). Between June and December 1998, 2.6 million m3 of dredged sediment were deposited there. The bathymetric maps generated in the course of this study reveal features such as subaqueous dunes, scour holes, and mounds of dumped dredge spoil. The mean water depth decreased by about 1 m during the dumping period. Furthermore, difference grids showing changes in sediment volume allowed a calculation of the sediment budget for the monitored area. After a time period of only 5 months, 0.5 million m3 of the originally dumped 2.6 million m3 of dredge spoil had already been removed from the dumping site. 相似文献
84.
85.
东海黑潮及琉球群岛以东海流研究进展 总被引:4,自引:0,他引:4
东海是西太平洋的一个边缘海,它西部有广阔的大陆架,东面以九州岛、琉球群岛(由奄美诸岛、冲绳诸岛、先岛诸岛组成)和台湾岛连线为界,具有较深的海槽。黑潮是一支高温、高盐、高流速的西边界流,它起源于菲律宾以东海域、流经台湾东岸进入东海,沿东海大陆架外缘向东北向流动,穿越吐噶喇海峡返回太平洋。通常的把自台湾东北端起至吐噶喇海峡一段称为东海黑潮。此外,在琉球群岛以东海域也常年存在一支稳定的西边界流,称为琉球海流。
对于东海黑潮和琉球海流的硏究,主要起步于20世纪80年代,通过进行中日联合调查研究、中日副热带环流调查研究等,取得了许多重要成果,苏纪兰(1994)、袁耀初(2000,Yuan,2006)、管秉贤(2002)等人都做过评述。本文基于以上研究评述,主要叙述200年以来对东海黑潮及琉球海流的硏究新进展。 相似文献
86.
Size-Fractionated Primary Production Estimated by a Two-Phytoplankton Community Model Applicable to Ocean Color Remote Sensing 总被引:3,自引:0,他引:3
In order to estimate primary production from ocean color satellite data using the Vertical Generalized Production Model (VGPM; Behrenfeld and Falkowski, 1997), we propose a two-phytoplankton community model. This model is based on the two assumptions that changes in chlorophyll concentration result from changes of large-sized phytoplankton abundance, and chlorophyll specific productivity of phytoplankton tends to be inversely proportional to phytoplankton size. Based on the analysis of primary production data, P
opt
B
, which was one parameter in the VGPM, was modeled as a function of sea surface temperature and sea surface chlorophyll concentration. The two-phytoplankton community model incorporated into the VGPM gave good estimates in a relatively high productive area. Size-fractionated primary production was estimated by the two-phytoplankton community model, and P
opt
B
of small-sized phytoplankton was 4.5 times that of large-sized phytoplankton. This result fell into the ranges observed during field studies. 相似文献
87.
Spatial and temporal variability of heat content above the thermocline in the tropical Pacific Ocean 总被引:1,自引:0,他引:1
Abstract-Heat content of the upper layer above the 20℃ isotherm in the tropical Pacific Ocean isestimated by using the sea temperature data set with a resolution 2°latitude×5°longitude (1980~1993)for the water depths (every 10 m) from 0 m to 400 m, and its temporal and spatial variabilities are an-alyzed. (1) The temporal variability indicates that the total heat in the upper layer of the equatorial Pa-cific Ocean is charcterized by the interannual variability. The time series of the equatorial heat anomaly5 months lead that of the El Nino index at the best positive lag correlation between the two, and theformer 13 months lag behind the latter at their best negative lag correlation. Therefore the equatorialheat content can be used as a better predictor than the El Nino index for a warm or cold event. In addi-tion, it is also found that less heat anomaly in the equator corresponds to the stronger warm events inthe period (1980~1993) and much more heat was accumulated in the 4 years including 1992/1 相似文献
88.
Long-term Sensor Drift Found in Recovered Argo Profiling Floats 总被引:5,自引:0,他引:5
We recovered three Argo profiling floats after 2 to 2.5 years of operation, and recalibrated their temperature, conductivity, and pressure sensors. The results demonstrate that these floats exhibited a significant drift in salinity of −0.0074 to −0.0125, primarily due to the conductivity sensor drift. Combined with the recalibration result for another previously recovered float, the indication is that the negative salinity drift increases nearly in proportion to the operating period of floats. The increasing rate is −0.0041 (±0.0015) year−1, which yields a salinity drift of −0.016 (±0.006) for the expected float lifetime of four years. The present result suggests that reducing the float surfacing time would improve the accuracy of the salinity measurements. 相似文献
89.
INTRODUCTIONCryptomonasisunicellularbiflagellatewhichisacommongenusofCryptophyta .Thecellsareusuallystronglycompressedlaterally .ThereareoneortwolargeChloroplaststhatcontainchlorophylla ,c ,somecharacteristiccarotenoidsandphycobilinpigments (Huetal.,1 997;Wei… 相似文献
90.
盐渍洼地蟹种培育试验 总被引:1,自引:0,他引:1
盐渍洼地种蟹培育是解决成蟹养殖种苗来源的重要途径,文中介绍的幼蟹放养,饲养管理与水质控制,幼蟹生长率与土增重量的变化,蟹种成活率与回捕率等对蟹种池墉强化培育提供了经验与理论依据。 相似文献