Jellyfish patch formation investigated by aerial photography and drifter experiment     

Shinya Magome  Tomohiro Yamashita  Takeshi Kohama  Atsushi Kaneda  Yuichi Hayami  Satoru Takahashi  Hidetaka Takeoka 《Journal of Oceanography》2007,63(5):761-773

Jellyfish patch formation is investigated by conducting a drifter experiment combined with aerial photography of a sustained patch of the moon jellyfish in Hokezu Bay, Japan. Jellyfish patches are aggregations of individuals that are caused by a combination of swimming (active influence) and advection by currents (passive influence). The drifter experiment involved the injection of 49 drifters around a distinct surface patch of jellyfish within an area of approximately 300 m × 300 m. The drifters’ motion, caused only by the passive influence, was recorded in a series of 38 aerial photographs taken over approximately 1 h. The ambient uniform current field larger than the patch scale was estimated from the movement of the centroid position of drifters, while the distribution of horizontal divergence and relative vorticity around the patch was estimated from the time-derivative in areas of triangles formed by the drifters. The centroid positions of both drifters and patches moved stably toward the bay head at different speeds. The difference vector between the patch and drifter centroids was directed to the sun, and was opposite to the ambient current. The distributions of vorticity and divergence around patches exhibited inhomogeneity within the patch scale, and the drifters in this nonuniform current field aggregated near the convergence area within 1 h. The results suggest that horizontal patch formation is predominantly influenced by passive factors at the surface of Hokezu Bay. Furthermore, the upward swimming against downwelling may make sustained patch in surface layer.  相似文献   

厦门东海域定置网渔获鱼类种类组成及其季节变化   总被引：7，自引：1，他引：7  

黄良敏  张雅芝  姚舒栓 《台湾海峡》2006,25(4):509-520

2003年7月～2004年6月对厦门东部海域的定置网渔获鱼类进行采样分析．结果表明厦门东海域至少有鱼类242种，隶属于19个目81科145属，主要是沿岸近底层和底栖的小型鱼类．以鲈形目种类最多，共计127种，占总数的52．5％、经济种类有116种．主要优势种有：青鳞小沙丁鱼、孔鳞小沙丁鱼、斑鲦、马拉邦虫鳗、裸鳍虫鳗、中华须鳗、前鳞鲻、眶棘双边鱼、多鳞鳝、皮氏叫姑鱼、短棘银鲈、列牙垒幸4、黄斑蓝子鱼、褐蓝子鱼、锯塘鳢、锻虎鱼类、褐菖鲇、绿鳍鱼、鳄鲡、卵鳎、中华单角鲍等．渔获种类在秋季及冬初最多，夏季较多，而冬末和春初最少．渔获种类的季节变化比较明显，与海洋表层水温变化有关，种类的月更替率比较高．  相似文献   

台湾海峡西部海域软质海底多毛类的生态   总被引：2，自引：0，他引：2  

吴启泉 《台湾海峡》1993,12(4):324-334

本文根据１９８４－１９８５年４航次底栖生物调查资料，首次全面地研究了台湾海峡西部海域多毛类的种类组成，数量分布及其与环境因子的关系。结果表明，该海域多毛类４０４种，习见种１９１种，区系属亚热带性质；平均生物量４．３３ｇ／ｍ＾２，平均栖息密度６８个／ｍ＾２；有沿岸性和外洋性两种明显不同的生态类型，前者位于沿岸水系常年控制海域，种类多，数量较大，后者位于南部粗粒沉积物分布区，种类较少；多毛类高数量区与  相似文献   

Composition and distribution of meiobenthos in amursky bay (peter the great bay, the east sea)     

Olga N. Pavlyuk  Julia A. Trebukhova 《Ocean Science Journal》2005,40(3):10-16

Qualitative and quantitative composition of meiobenthos was studied in Amursky Bay (Peter the Great Bay, the East Sea). Ten taxonomic groups were found, where nematodes were dominant. Density of meiobenthos in ground sediments of the Bay were not uniform, and the average density was measured at 126.4±62.3 ind. m^-2. 56 species of nematodes were detected, and dominant species wereSabatieria palmaris, Paracanthonchus macrodon, Sphaerolaimus limosus, S. gracilis andOncholaimium ramosum. Five taxocenes of nematodes were allocated based on the results of cluster analysis and species domination according to density. Low diversity in species composition of nematodes was noted in the northwestern part of the Bay, which is a zone of desalination, and in the eastern part, which is exposed to household drains.  相似文献   

Summer distribution and geochemical composition of suspended-particulate matter in the east china sea     

Jia-Jang Hung  Chia-Lin Chan  Gong-Ching Gong 《Journal of Oceanography》2007,63(2):189-202

The distribution and geochemical composition of suspended-particulate matter (SPM) in the East China Sea (ECS) were investigated during the summer period of high continental runoff to elucidate SPM sources, distribution and cross-shelf transport. The spatial variability of SPM distribution (0.3–6.5 mg l⁻¹) and geochemical composition (POC, Al, Si, Fe, Mn, Ca, Mg and K) in the ECS was pronounced during summer when the continental fluxes of freshwater and terrestrial materials were highest during the year. Under the influences of Changjiang runoff, Kuroshio intrusion, surface production and bottom resuspension, the distribution generally showed strong gradients decreasing seaward for both biogenic and lithogenic materials. Particulate organic carbon was enriched in surface water (mean ∼18%) due to the influence of biological productivity, and was diluted by resuspended and/or laterally-transported materials in bottom water (mean 9.4%). The abundance of lithogenic elements (Al, Si, Fe, Mn) increased toward the bottom, and the distribution correlations were highly significant. Particulate CaCO₃ distribution provided evidence that the SPM of the bottom water in the northern part of the study area was likely mixed with sediments originally derived from Huanghe. A distinct benthic nepheloid layer (BNL) was present in all seaward transects of the ECS shelf. Sediment resuspension may be caused by tidal fluctuation and other forcing and be regarded as the principal agent in the formation of BNL. This BNL was likely responsible for the transport of biogenic and lithogenic particles across or along the ECS shelf. Total inventories of SPM, POC and PN are 46, 2.8 and 0.4 Tg, respectively, measured over the total area of 0.45 × 10⁶ km² of the ECS shelf. Their mean residence times are about 27, 13 and 11 days, respectively. The inventory of SPM in the water column was higher in the northernmost and southernmost transects and lower in the middle transects, reflecting the influences of terrestrial inputs from Changjiang and/or resuspended materials from Huanghe deposits in the north and perhaps from Minjiang and/or Taiwan’s rivers in the south. The distribution and transport patterns of SPM and geochemical elements strongly indicate that continental sources and cross-shelf transport modulate ECS particulate matter in summer.  相似文献   

Spatial and temporal distribution patterns of deep‐sea mesozooplankton in the eastern Mediterranean – indications of a climatically induced shift?     

Rolf Koppelmann  & Horst Weikert 《Marine Ecology》2007,28(2):259-275

Zooplankton samples from the eastern Mediterranean were collected in April/May 1999 with a multiple opening and closing net (mesh size 333 μm) to examine the distribution and taxonomic composition of mesozooplankton, mainly Calanoida (Copepoda), some years after the onset of the Eastern Mediterranean Transient (EMT), a climatically induced shift in hydrography. The samples from seven stations on a transect from the Ionian Sea to the eastern part of the Levantine Basin were collected at closely spaced vertical intervals from the surface to water depths of 4250 m. Data from January 1987, June 1993, January 1998 and October 2001 from the main site of investigation, south of Crete, were used to describe the temporal evolution before (1987), during (1993) and after (1998–2001) the EMT. The eastern Mediterranean mesozooplankton fauna is dominated by three Calanoida species along the west–east transect, with varying abundances in different depth‐zones: Haloptilus longicornis in the epipelagic zone, Eucalanus monachus in the mesopelagic zone, and Lucicutia longiserrata in the bathypelagic zone. A drastic change in mesozooplankton composition and abundance occurred at the main site during the EMT, whereupon increased abundances of Candacia elongata and L. longiserrata were observed in the bathypelagic zone in the following years; L. longiserrata accounted for 43% of the total mesozooplankton in this zone. The hypothesis is posed that the Mediterranean deep‐sea ecosystem is able to respond quickly to changes in the environment and memorizes these changes over time. We claim that the biological effects of climatically induced changes can be easily monitored in the deep eastern Mediterranean Sea using calanoid copepod key species due to the hydrographically extreme, but ‘simply structured’ ecosystem.  相似文献   

Feeding ecology and abundance of two sympatric skates, the shortfin sand skate Psammobatis normani McEachran, and the smallthorn sand skate P. rudis Gunther (Chondrichthyes, Rajidae), in the southwest Atlantic   总被引：1，自引：0，他引：1  

Mabragana  Ezequiel; Giberto  Diego A. 《ICES Journal of Marine Science》2007,64(5):1017-1027

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雷州半岛灯楼角珊瑚礁海区的浮游植物   总被引：8，自引：2，他引：8  

尹健强  黄晖  黄良民  林永水  李开枝  练健生 《海洋通报》2006,25(2):8-14

雷州半岛西南岸的珊瑚礁,是唯一的中国大陆沿岸现代珊瑚礁。根据2004年8月的调查资料研究分析了雷州半岛灯楼角珊瑚礁海区浮游植物的种类组成、生态类群和数量分布等,以期为珊瑚礁生态系的研究提供基础资料。结果显示:浮游植物共有108种(含变种和变型),其中硅藻门34属85种、甲藻门10属21种、蓝藻门1属2种,浮游植物的种数分布由近岸往远岸递增;浮游植物大致划分为近岸低盐类群、近海广布类群和外海高温高盐类群等3个生态类群;优势种有中肋骨条藻Skeletonemacostatum、菱形海线藻Thalassionemanitzschioides、奇异菱形藻Nitzschiaparadoxa等8种;多样性指数和均匀度平均值分别为3.448和0.655,总体分布比较均匀;浮游植物细胞总量平均值为93×104cells/m3,其中硅藻类占绝对优势,浮游植物分布不均匀,密集于灯楼角南面的A断面。  相似文献   

抑制栉孔扇贝第一极体对受精卵染色体行为及胚胎倍性组成的影响   总被引：4，自引：0，他引：4  

李永仁  阙华勇  张国范 《海洋科学》2005,29(8):66-70

采用细胞松弛素B（CB）处理，栉孔扇贝（Chlamys ferreri）抑制其受精卵的第一极体（PB1），研究抑制PB1对受精卵减数分裂过程及胚胎倍性组成的影响。结果发现，抑制第一极体显著改变了受精卵的染色体行为，在第二次减数分裂过程中共发现4种典型染色体分离类型，分别是三极分离（41．7％）、二极分离（11．7％）、双二极分离（24．9％）和非同步分离（2．8％），其余的受精卵（19．0％）染色体分离行为紊乱。对4-8细胞期胚胎的倍性组成进行分析，发现处理组中含有二倍体（10．9％）、三倍体（12．5％）、四倍体（19.5％）、五倍体（12．6％）以及非整倍体（46．6％）胚胎。研究结果表明，二极分离和双二极分离分别是形成三倍体和四倍体的主要机制，而其他的染色体分离行为将主要形成非整倍体。  相似文献   

南海西沙西南海域表层沉积物特征   总被引：3，自引：1，他引：3  

邱燕  姚伯初 《海洋地质与第四纪地质》1997,17(4):41-53

西沙西南海域表层沉积物样品矿物成分，地球化学，微体古生物分析测试结果表明：沉积物可分为７种类型，沉积环境主要是陆坡，部分为深海平原，海洋生物，海洋化学以及火山物质的沉积起到了积极的作用，陆源物质的影响较小，它们主要来源于北部大陆和南部岛礁等物源区。  相似文献