Zoogeography of marine Bryozoa around South Africa     

MK Boonzaaier-Davids  WK Florence  MJ Gibbons 《African Journal of Marine Science》2020,42(2):185-198

The zoogeography of marine Bryozoa around South Africa was investigated using published distribution records, museum catalogues, and an examination of previously unworked bryozoan material in (mostly) museum collections. Although a total of 276 valid species are recognised, it was not possible to unambiguously assess geographic patterns of diversity. At all depth zones examined (shore and inner-shelf, 0–30 m; mid- and outer-shelf, 31–350 m; bathyal, >500 m), there was a clear geographic structure to communities that mirrored established regional patterns of biogeography. Too few samples were collected from the shelf edge (351–500 m) and they were consequently excluded from zoogeographic analysis. Communities on the shore and inner-shelf and on the mid- and outer-shelf were more similar to each other than they were to bathyal communities, and the pronounced structure in bathyal communities suggests heterogeneity in the deep sea around South Africa.  相似文献   

西北太平洋副热带逆流、北赤道流、北赤道逆流几个特征的比较     

孙湘平 《海洋科学进展》2000,18(1):1-12

根据137°E断面1967～1995年冬、夏季的温、盐资料,计算和分析该断面的地转流;分析144°E断面上投放卫星跟踪漂流浮标的漂移轨迹;结合CSK图集中的海面重力势分布,对副热带逆流、北赤道流和北赤道逆流几个特征的相同点和不同点进行比较,得出若干有益的结论:(1)副热带逆流、北赤道流、北赤道逆流,并不是单纯的单支海流,而是存在着两支或多支现象;(2)流速结构的带状分布,东、西向流相互交错间隔出现,流层较浅,均为表层流或近表层流;(3)多年平均而言,3支海流的流速以北赤道逆流最强,北赤道流次之,副热带逆流最弱;流量则不同,北赤道流最大,副热带逆流最小,北赤道逆流居中.3支海流的流速夏季均大于冬季,但流量稍有差异:副热带逆流和北赤道流均具有夏强、冬弱的特点,而北赤道逆流为冬强、夏弱;(4)冬季,副热带逆流的"源地",位于巴士海峡和台湾以东"副热带脊"的一个"暖脊"中心附近海域;(5)冬季,卫星跟踪漂流浮标的漂移轨迹,基本上反映出北赤道流和北赤道逆流的路径.但因副热带逆流区为涡旋频繁区,致使浮标漂移轨迹难以反映出副热带逆流的路径.  相似文献   

The circulation in the southern Huanghai Sea and northern East China Sea in June 1999   总被引：1，自引：0，他引：1  

Yaochu Yuan  Yonggang Liu  Mingyu Zhou  Arata Kaneko  Zhou Yuan  Noriaki Gohda 《海洋学报(英文版)》2003,22(3):321-332

On the basis of hydrographic data and current measurement (the mooring system, vessel-mounted ADCP and toward ADCP) data obtained in June 1999, the circulations in the southern Huang-hai Sea (HS) and northern East China Sea (ECS) are computed by using the modified inverse method. The Kuroshio flows northeastward through eastern part of the investigated region and has the main core at Section PN, a northward flow at the easternmost part of Section PN, a weaker anti-cyclonic eddy between these two northward flows, and a weak cyclonic eddy at the western part of Section PN. The above current structure is one type of the current structures at Section PN in ECS. The net northward volume transport (VT) of the Kuroshio and the offshore branch of Taiwan Warm Current (TWCOB) through Section PN is about 26.2×106m3/s in June 1999. The VT of the inshore branch of Taiwan Warm Current (TWCIB) through the investigated region is about 0.4×106m3/s. The Taiwan Warm Current (TWC) has much effect on the currents over the  相似文献   

Considering ecosystem-based fisheries management in the California Current     

John C. Field  Robert C. Francis 《Marine Policy》2006

Recognizing that all management decisions have impacts on the ecosystem being exploited, an ecosystem-based approach to management seeks to better inform these decisions with knowledge of ecosystem structure, processes and functions. For marine fisheries in the California Current, along the West Coast of North America, such an approach must take into greater consideration the constantly changing climate-driven physical and biological interactions in the ecosystem, the trophic relationships between fished and unfished elements of the food web, the adaptation potential of life history diversity, and the role of humans as both predators and competitors. This paper reviews fisheries-based ecosystem tools, insights, and management concepts, and presents a transitional means of implementing an ecosystem-based approach to managing US fisheries in the California Current based on current scientific knowledge and interpretation of existing law.  相似文献   

Spatial variability of phytoplankton absorption coefficients and pigments off Baja California during November 2002     

Óscar A. Barocio-León  Roberto Millán-Núñez  Eduardo Santamaría-del-Ángel  Adriana González-Silvera  Charles C. Trees 《Journal of Oceanography》2006,62(6):873-885

We have estimated the spatial variability of phytoplankton specific absorption coefficients (a* _ph ) in the water column of the California Current System during November 2002, taking into account the variability in pigment composition and phytoplankton community structure and size. Oligotrophic conditions (surface Chl < 0.2 mg m⁻³) dominated offshore, while mesotrophic conditions (surface Chl 0.2 to 2.0 mg m⁻³) where found inshore. The specific absorption coefficient at 440 [a* _ph (440)] ranged from 0.025–0.281 m²mg⁻¹ while at 675 nm [a* _ph (675)] it varied between 0.014 and 0.087 m²mg⁻¹. The implementation of a size index based on HPLC data showed the community structure was dominated by picoplankton. This would reduce the package effect in the variability of a* _ph (675). Normalized a _ph curves were classified in two groups according to their shape, separating all spectra with peaks between 440 and 550 nm as the second group. Most samples in the first group were from surface layers, while the second group were from the deep chlorophyll maximum or deeper. Accessory photoprotective pigments (APP) tended to decrease with depth and accessory photosynthetic pigments (APS) to increase, indicating the importance of photoprotective mechanisms in surface layers and adaptation to low light at depth. Samples with higher ratios of APP:APS (>0.4) were considered as phytoplankton adapted to high irradiances, and lower ratios (<0.26) as adapted to low irradiances. We found a good relationship between APP:APS and a* _ph (440) for the deeper layer (DCM and below), but no clear evidence of the factors causing the variability of a* _ph (440) in the upper layer.  相似文献   

Tintinnids (Ciliophora) and Other Net Microzooplankton (> 30 µm) in Southwestern Atlantic Shelf Break Waters     

Gustavo A. Thompson  Viviana A. Alder    & Demetrio Boltovskoy   《Marine Ecology》2001,22(4):343-355

Abstract. Proportions of foraminifers, tintinnids, polycystine radiolarians, pteropods and crustacean larval stages were estimated in a collection of 76 vertically stratified (0 – 100 m) 30 µm net microplankton samples from 16 stations along the Argentine shelf-slope (around 200 m isobath – between 40 and 56° S), covered on 13 – 18 November 1996. Tintinnids were identified to species. Relative abundances of the microzooplankton assessed and chlorophyll a values allow to define two contrasting groups of stations: 'deep' and 'shallow'. The former, located in pelagic, purely subantarctic Malvinas Current waters, hosted higher proportions of foraminifers and lower proportions of tintinnids, as well as less chlorophyll a (all differences were significant at the 0.1 % level). 'Shallow' stations were located in the area of the thermohaline front where the Patagonian Current comes in contact with the Malvinas Current, and were generally characterized by higher chlorophyll a levels (up to 3.7 µg Chl a  · l^–1). The distribution of tintinnid species, on the other hand, allowed no discrimination between these two areas, although some of the dominant forms showed much higher relative abundances in one of the two groups of stations. Twenty-six tintinnid taxa were recorded, yet only 6 accounted for 95 % of the specimens identified. Tintinnid taxocoenoses were characterized by a few abundant species and many rare ones. Numbers of tintinnid species and specific diversity did not differ noticeably with depth and latitude. Cape Horn Current waters were detected in the area by the presence of expatriated organisms presumably originating at mid-latitudes in the South Pacific Ocean.  相似文献   

Low frequency variations in currents on the southern continental shelf of the Caspian Sea     

《Dynamics of Atmospheres and Oceans》2019

The Caspian Sea (CS) is the largest enclosed basin in the world, located inside the Eurasian continent in the Northern Hemisphere. Although there have been few studies of the dynamics of the coastal zone in the CS, observations show that oscillations with periods from 2–3 days to 1–3 weeks dominate. These oscillations are presumed to be related to the synoptic variability of direct wind impact and to coastally-trapped waves (CTW). Here, we describe and interpret current meter observations on the continental margins of the southern CS from 2012 to 2014 to identify and characterize CTW there. Time series analysis provides evidence for both remote and locally wind-forced eastward traveling signals with time lags consistent with CTW theory. A wind-forced model with two CTW modes is able to reproduce the structure, amplitudes, and phases of observed alongshore current fluctuations, explaining half of the variance at frequencies less than 1 cpd. Remote forcing effects are present at all times, but are most striking when the local winds are weak, as in summer. The CTW calculations also suggest that the source region for the remote forcing may extend farther north along the west coast of the CS.  相似文献   

准噶尔盆地南缘下组合现今温压场特征及其控制因素          下载免费PDF全文

靳 军 刘 明 刘雨晨 王 剑高崇龙  罗正江鲁 峰 任 影 《地质科学》2021,56(1):28-043

准噶尔盆地南缘下组合储层是近年来油气勘探的热点,目前南缘下组合储层多处于高温高压条件,但是温压发育特征及成因机理尚不明确。本文基于大量油田钻井实测温度和压力数据,对该区现今地温梯度及温度、压力分布特征进行了系统研究,探讨了温压场分布的控制因素。研究表明,准噶尔盆地南缘地区现今地温梯度普遍在13.2℃/km~23.7℃/km之间,平均为18.2℃/km,地温梯度高值分布于齐古断褶带中部和阜康断裂带西部。大地热流介于26.4 mW/m²~46.0 mW/m2,平均值为36.1 mW/m²,属于准噶尔盆地内地温梯度及热流较低的地区,这主要受到盆地基底格局的控制。南缘西段卡因迪克地区压力系数以常压为主,位于四棵树凹陷的高探1井、独山1井和西湖1井下组合地层在6000 m左右开始发育强超压。南缘东段下组合层系均发育弱超压或强超压,自西向东压力系数逐渐增高。根据声波时差—有效应力关系反映南缘地区下组合地层除不均衡压实作用外,还存在横向构造挤压及有机质生烃的超压机制,喜马拉雅期较强的横向构造挤压是盆地南缘下组合发育异常高压的重要因素之一,有机质生烃是西山窑组—三工河组超压层形成的主要原因。  相似文献   

基于1987-2010年实测资料对PN断面东海黑潮季节变化的分析     

WEI Yanzhou  PEI Yuhu  ZHANG Rong-Hua 《海洋学报(英文版)》2015,34(5):12-21

As the spatio-temporal variability of the Kuroshio is highly influenced by mesoscale eddies, representing its seasonal variability characteristics requires sufficiently long term observations to reduce...  相似文献   

88ka以来冲绳海槽北部古环境演化:来自元素地球化学的证据   总被引：1，自引：1，他引：0  

朱爱美  石学法  邹建军  张辉  吴永华  刘焱光 《海洋学报》2015,37(6):58-69

对CSH1岩心全样沉积物样品进行元素地球化学分析,揭示了过去88ka冲绳海槽北部沉积物成分、水动力条件及陆源碎屑物质源区风化历史。冲绳海槽北部碎屑沉积物母岩主要以长英质为主,在MIS 1期沉积物存在大量火山源物质。过去88ka,沉积物源区风化程度较弱,但是自冰消期以来有逐渐增强的趋势。沉积物Zr/Nb比值表明在MIS 1期和MIS 5.1期水动力较为强烈,这与黑潮增强的时间一致,可能是指示黑潮强度的一个指标。冲绳海槽北部陆坡沉积物陆源碎屑贡献在低海平面时期显著增加,而在MIS 1和MIS 5.1期生源贡献显著增加。冲绳海槽北部沉积物成分变化明显受到黑潮和入海径流的调节,实际上受海平面和东亚季风的制约。  相似文献