Seasonal and Spatial Variations of Total Mass Flux around Coral Reefs in the Southern Ryukyus,Japan     

Mohamed?IsmailEmail author  Tadashi?Kimura  Yumiko?Suzuki  Makoto?Tsuchiya 《Journal of Oceanography》2005,61(3):631-644

Total mass flux, size distribution of sediment particles and some chemical components such as total carbon (TC), total nitrogen (TN) and calcium carbonate (CaCO₃) were monitored monthly using a multi-cup sediment traps at seven coral reef sites (6 reef flat and 1 reef slope) of the Marine Protected Areas around Ishigaki, Kohama, Kuroshima and Iriomote Islands in the southern Ryukyus, Japan from September 2000 to September 2001. The size distribution of trapped sediments revealed mostly uni-modal fine sand to mud in the reef flat and gravelly to coarse sand in the reef slope. The total mass flux ranged between 0.54 to 872 gm⁻²d⁻¹, and showed a pronounced seasonality (high in summer-autumn and low in spring) at each site, which was consistent with the rainfall and typhoon regime. Exceptionally high values were observed on the reef slope (Iriomote) in February–March 2001 (1533 gm⁻²d⁻¹) owing to a large amount of bottom sediment re-suspension. On the reef flat (Todoroki South and North; Ishigaki), values obtained in July–August 2001 (872 gm⁻²d⁻¹) and August–September 2001 (800 gm^{− 2}d⁻¹) indicate the high terrestrial discharge from Todoroki River. Trapped sediment particles consist of CaCO₃ (1.2–27.1%) and a non-carbonate fraction (98.8–72.9%), which contains total carbon (4.9–26%), carbonate carbon (CO₂-C) (0.2–3.1%) and non-carbonate carbon (NC-C) (7.9–25.6%). Total nitrogen content was in the range 0.02–0.48%. TN is contained mainly in the carbonate fraction and NC-C may be contained in the non-carbonate fraction. The low TN/OC ratio of the trapped sediments suggests that they were mostly of terrestrial origin and that both fractions migrated. The high total mass flux derived from Todoroki River exceeded the threshold at which a lethal effect on coral community is caused. The results stress the importance of conducting seasonal studies of sedimentation over more than one year and at more than one location in south Japan coral reef ecosystems to gain an understanding of the processes controlling the total mass fluxes and their nutrients content, also to develop an awareness of how to prevent the damage of coral reef ecosystems and, if it does occur, to allow mitigation measures to be undertaken.  相似文献   

气象卫星用于近海污染监测及赤潮预报方法探索     

杨超武  田庆久  张满郎  王晋年 《海洋科学进展》1997,(4)

近年来，由于工农业和沿海养殖业的发展，我国近海污染逐年加重，赤潮发生频次增加。因此，监测近海污染和赤潮发生预报方法研究势在必行。本文用ＮＯＡＡ／ＡＶＨＲＲ数据，分析近海水域污染状况，并探索赤潮发生的预报方法。  相似文献   

胶州湾海域水质预测   总被引：3，自引：0，他引：3  

孙英兰  孙长青  王丽霞  徐鸿楷 《中国海洋大学学报(自然科学版)》1994,(Z1)

在已建潮流模型的基础上,用ADI法建立了胶州湾扩大域变动边界的平流—扩散输运模型,以COD为指示因子,预测了胶州湾海域1995年、2000年的水质、青岛环海公路海上段、沧口区北半部污水截流、北水南调、集中排放以及胶州湾西部经济开发对海域水质的影响等。为青岛市环保部门制定环保规划提供决策依据。  相似文献   

Possible Density Change of the Origin of North Pacific Intermediate Water Due to Double Diffusion in the Mixed Water Region     

Ryuichiro?InoueEmail author  Jiro?Yoshida 《Journal of Oceanography》2005,61(5):871-883

In this study we test Talley's hypothesis that Oyashio winter mixed-layer water (26.5–26.6σ _θ) increases its density to produce the North Pacific Intermediate Water (NPIW) salinity minimum (26.7– 26.8σ_θ) in the Mixed Water Region, assuming a combination of cabbeling and double diffusion. The possible density change of Oyashio winter mixed-layer water is discussed using an instantaneous ratio of the change of temperature and salinity along any particular intrusion (R _l ). We estimate the range of R _l ^DD required to convert Oyashio winter mixed-layer water to the NPIW salinity minimum due to double diffusion, and then assume double-diffusive intrusions as this conversion mechanism. A double-diffusive intrusion model is used to estimate R _l ^DD in a situation where salt fingering dominates vertical mixing, as well as to determine whether Oyashio winter mixed-layer water can become the NPIW salinity minimum. Possible density changes are estimated from the model R _l ^DD by assuming the amount of density change due to cabbeling. From these results, we conclude that Oyashio winter mixed-layer water contributes to a freshening of the lighter layer of the NPIW salinity minimum (around 26.70σ_θ) in the MWR.  相似文献   

Estuary/ocean exchange and tidal mixing in a Gulf of Maine Estuary: A Lagrangian modeling study   总被引：2，自引：0，他引：2  

Ata Bilgili  Jeffrey A. Proehl  Daniel R. Lynch  Keston W. Smith  M. Robinson Swift 《Estuarine, Coastal and Shelf Science》2005,65(4):607-624

A Lagrangian particle method embedded within a 2-D finite element code, is used to study the transport and ocean–estuary exchange processes in the well-mixed Great Bay Estuarine System in New Hampshire, USA. The 2-D finite element model, driven by residual, semi-diurnal and diurnal tidal constituents, includes the effects of wetting and drying of estuarine mud flats through the use of a porous medium transport module. The particle method includes tidal advection, plus a random walk model in the horizontal that simulates sub-grid scale turbulent transport processes. Our approach involves instantaneous, massive [O(500,000)] particle releases that enable the quantification of ocean–estuary and inter-bay exchanges in a Markovian framework. The effects of the release time, spring–neap cycle, riverine discharge and diffusion strength on the intra-estuary and estuary–ocean exchange are also investigated.The results show a rather dynamic interaction between the ocean and the estuary with a fraction of the exiting particles being caught up in the Gulf of Maine Coastal Current and swept away. Three somewhat different estimates of estuarine residence time are calculated to provide complementary views of estuary flushing. Maps of residence time versus release location uncover a strong spatial dependency of residence time within the estuary that has very important ramifications for local water quality. Simulations with and without the turbulent random walk show that the combined effect of advective shear and turbulent diffusion is very effective at spreading particles throughout the estuary relatively quickly, even at low (1 m²/s) diffusivity. The results presented here show that a first-order Markov Chain approach has applicability and a high potential for improving our understanding of the mixing processes in estuaries.  相似文献   

环太湖河道污染物负荷量的初步研究   总被引：5，自引：1，他引：5       下载免费PDF全文

袁静秀  黄漪平 《海洋与湖沼》1993,24(5):485-493

根据１９８７－１９８８年环太湖河道水质，水量实测资料以及环湖主要河道的流量和水质的历史资料，结合平原水网地区的水情特征，提出了环太湖河道污染物负荷量的计算方法，并分析探讨了不同设计水情下环太湖河道污染物负荷量及其时空变化。结果表明，污染物负荷量与水情关系密切，枯水年的河道入湖污染物负荷量大于丰水年。环湖２２条主要河道的入湖污染物负荷量占全部河道入湖总量的７２％－９１％，且不同污染物入湖负荷量的分布  相似文献   

东海黑潮水与陆架水的季节性输运和交换     

林葵  陈则实  郭炳炎  汤毓祥 《海洋科学进展》1995,(4)

在流星分析和ｔ－Ｓ点聚分析的基础上，在台湾东北部ＩＳ断面和东海中部ＰＮ断面上选取适当的纵剖面作为分界面，将以面分成东、西两侧，计算了界面两侧的海水交换星。结果表明：１．东海陆架区海水交换可归纳为两种类型，即“穿插型”和“进退型”。２．参与分界面处海水交换总量的年平均是夏季最大，春、秋季次之，冬季最小。黑潮水向陆架区输运量为０．５８×１０６ｍ３／ｓ，陆架水向黑潮刚输运量为０．８４×１０６ｍ３／ｓ；参与交换的总量为１．４２×１０６ｍ３／ｓ．３．相对输运量计算结果表明；黑潮水对陆架区水文状况的影响是冬季最强，秋、春季次之，夏季最弱，而陆架水对黑潮区水文状况的影响是夏季最大，秋季次之，春季和冬季最小。  相似文献   

济州岛南部海区的双跃层现象     

苏育嵩  李凤岐  马鹤来  钱清瑛 《中国海洋大学学报(自然科学版)》1989,(Z1)

本文分析了济州岛南部区域温度双跃层现象的类型及其成因。特别阐明了双跃层的波状现象,指出:强流锋区的侧向效应,黑潮次—中层混合水的爬升,黄海冷水团边缘密度环流引起的侧向流动,以及上、下层流速、流向不一致引起的剪切作用,是导致双跃层波状现象的主要原因。发现上、下跃层之间存在着“跃层间环流”,这是一个有趣的海洋学现象,它将导致双扩散的发生和有利于双跃层的维持。  相似文献   

春季东海不同水域的表层叶绿素含量   总被引：5，自引：0，他引：5  

鲁北伟  王荣  王文琪 《海洋科学》1997,21(5):53-55

利用１９９４年春季在东海及台湾海峡首次获得的表层水中绿素含量大面走航连续观测资料，结合温盐分布及以往的有关东海及台湾海峡的海流和上升流的结论，分析了春季东海表层叶绿素含量在不同水域的分布特征。结果表明，叶绿素含量分布与水文结构关系密切。叶绿素含量值随不同海流流域而变，但在各海流流域内基本不变，黑潮表层水的叶绿素含量最低，其次是台湾暖流表层水，长江冲淡水与江浙沿岸流域的叶绿素含量较高；黑潮西侧弱流剧  相似文献   

海洋生态环境监测的指标体系研究   总被引：1，自引：0，他引：1  

单宇  李正炎 《海洋湖沼通报》2007,200(2):52-56

本文在总结国内外各种海洋生态监测方法的基础上,构建生物分布指数、生物暴露指数和生物反应指数,并由此确定生态质量总指教。生态质量总指数可以综合反映特定海洋环境的生物群落特征,典型污染物在生物体内的蓄积特征以及生物体对环境污染的生理生化反应特征,因此可以应用于近岸海洋环境质量的生态监测。  相似文献