Solute Sources and Processes in the Achankovil River Basin,Western Ghats,Southern India/Sources de Solutés et Processus Associés Dans le Bassin du Fleuve Achankovil,Ghats Occidentaux,Inde du Sud     

《水文科学杂志》2013,58(2)

Abstract

A time series survey was carried out in 2002 to understand the hydrogeochemical processes taking place in the Achankovil River of the Western Ghats Range. The water is neutral with pH and EC ranges from 6.32 to 7.56 and 24–54 µS cm^?1, respectively. Chloride and sodium are the dominant anion and cation in the water respectively. Correlation analysis of the chemical parameters of the water shows that few ions have additional sources. The majority of carbonate is derived from carbonate weathering followed by silicate weathering. Cation concentrations show decreasing trend from upstream to downstream in contrast to the increasing trend in the major world rivers. Dissolved silica in pre-monsoon water is low. The river chemistry is dominated by rock weathering induced by precipitation. Thermodynamic plots show that dolomite, kaolinite, albite and chlorite are in equilibrium with the river water. Chemical weathering is predominant here compared to physical weathering. The overall material transport seems to be lower compared to the other Indian rivers; nevertheless, the solute loads are comparable to certain large rivers such as the River Cauvery in southern India. The solute flux including the nutrient flux is very high among the Western Ghats rivers in relation to its size, which will certainly supplement the productivity of the lake/estuary and the coastal waters. Since this study is restricted to a one-year period, long-term data procurement and analysis along with micro nutrients studies are needed, which are lacking in the present study, to gain insight into the material flux by this river into the Arabian Sea.  相似文献   

夏季东海陆架不同水团对悬浮体物质组成及粒度分布的影响     

雷栋  王珍岩  李文建 《海洋与湖沼》2019,50(4):740-751

基于2012年7月东海陆架水文及悬浮体粒度等实测数据,分析不同水团内悬浮体物质组成和粒度分布特征,并探究其影响因素,为查明东海陆架海区陆源沉积物输运扩散机制、揭示海底沉积物来源和成因机制等提供理论依据。结果显示:夏季东海陆架悬浮体由两部分构成,即≤128μm的无机颗粒和?128μm以浮游生物为主的颗粒,其平均体积浓度分别为3.5μL/L和8.4μL/L。悬浮体空间分布受到该海域水团类型的制约。长江冲淡水、台湾暖流表层水、台湾暖流深层水、台湾海峡暖水以及东海冷涡的悬浮体粒径均呈双峰分布,峰值位于27.7—74.7μm和391μm;苏北沿岸流影响海域悬浮体粒径呈单峰分布,小颗粒端含量极低。悬浮体粒度组成及其空间分布差异与水团挟带的无机颗粒、营养盐输送以及水体界面阻隔密切相关。其中,长江冲淡水挟带大量无机颗粒和营养盐进入东海,致使其无机颗粒和浮游生物含量均为研究区最高;苏北沿岸流经长距离扩散后挟带的无机颗粒大多已经沉降,因此无机颗粒含量在研究区最低,而其挟带的丰富营养盐,致使浮游生物含量为次高值;台湾暖流表层水、台湾暖流深层水、东海冷涡以及台湾海峡暖水中悬浮体均以无机颗粒为主,其中前三个水团的水体界面处浮游生物含量较高;不同水团垂向交界处常形成温、盐跃层,跃层能够抑制底层营养盐向表层的扩散,导致跃层位置成为浮游生物高含量区。  相似文献   

Environmental responses of jellyfish polyps as drivers of medusa populations off the coast of Namibia     

L Ziegler  MJ Gibbons 《African Journal of Marine Science》2018,40(3):323-329

Jellyfish populations in the southeastern Atlantic off the coast of Namibia have increased subsequent to the decline of small pelagic fisheries at the end of the 1960s, although the environment there has also become warmer and the waters off Walvis Bay have become richer in zooplankton in recent years. Laboratory experiments were conducted with the scyphozoan jellyfish Chrysaora fulgida to investigate the effects of food density (0, 30, 70, 100 or 150 Artemia nauplii 200 ml^?1), feeding frequency (once daily or once every third day) and water temperature (12, 16 or 20 °C) on the asexual reproduction, growth and development of polyps. The results of a generalised linear mixed-effects model reveal that all variables impacted asexual reproduction, with greater polyp production attained at higher food concentrations, increased feeding frequencies and increased temperatures. The most common mode of asexual reproduction was by lateral budding. These laboratory results suggest that polyps of C. fulgida may have proliferated off Namibia in recent times, which would contribute to increased numbers of jellyfish there.  相似文献   

[已撤稿] 三亚珊瑚礁珊瑚藻种类及其空间特征与环境因子的关系     

雷新明  黄晖  练健生  张浴阳  杨剑辉 《热带海洋学报》2019,38(3):79-88

珊瑚藻是珊瑚礁生态系统中重要的功能性群体。2010年通过水肺潜水分析了三亚珊瑚礁区的珊瑚藻种类组成和丰度, 以及群落空间特征与环境因子的关系。共鉴定出3科10属25种珊瑚藻, 其中珊瑚藻科占优势地位。三亚珊瑚礁区的珊瑚藻优势种分别为叉节藻Amphiroa ephedraea、拟中叶藻Mesophyllum simulans、串胞新角石藻Neogoniolithon fosliei、中叶藻M. mesomorphum、圆锥呼叶藻Pneophyllum conicum、孔石藻Porolithon onkodes和布氏水石藻Hydrolithon boergesenii。基于多元统计的分析结果, 将调查采样站位分为近岸型和离岸型2个主要集群, 其中近岸型的珊瑚藻种类以浊度、沉积速率(0~63μm)和悬浮物耐受种类为主, 离岸型则以光依赖-沉积物敏感种类为主。以珊瑚藻种类组成和丰度为基础的群落相似性分析结果表明, 其空间变异处于显著性水平。生物与非生物变量的相关分析结果表明, 最佳两变量组合(浊度和盐度)显著影响三亚珊瑚礁区2种类型调查站位中的珊瑚藻集合。在同一个研究站位, 因受干扰程度不同, 深水处的珊瑚藻的覆盖率比浅水处高。分析结果表明, 在三亚独特的珊瑚礁区中, 自然或人为的物理干扰因素都对调节珊瑚藻群落结构非常重要。  相似文献   

Nutrient dynamics in the Sylt-Rømø Bight ecosystem,German Wadden Sea: An ecological network analysis approach     

Dan Baird  Harald Asmus  Ragnhild Asmus 《Estuarine, Coastal and Shelf Science》2008

Carbon, nitrogen, and phosphorus flow networks, consisting of 59 compartments, were constructed for the Sylt-Rømø Bight, a large shallow sea in the German Wadden Sea. These networks were analysed using ecological network analysis. Each network depicts the standing stock of each component in the ecosystem, and the flows between them. The trophic efficiency by which material is utilised in the Bight increase from 3%, to 6% to 17% for C, N and P, respectively. The number of cycles though which these elements pass increase from 1 197 for carbon, to 414?744 and 538?800 for nitrogen and phosphorus, respectively. The Finn Cycling Index, reflecting the amount of material recycled as a fraction of the total system activity, TST, increases from 17% for carbon, to 43% for nitrogen, to 81% for phosphorus. Other system level attributes such as the Average Path Length, the Average Internal Mutual Information, Relative Ascendancy, Relative and Normalized Redundancy, show an increase from the carbon to the nitrogen to the phosphorus networks. Phosphorus is tightly cycled over longer pathways than the other two elements, and also has the longest residence time in the Bight. Postulated differences between the behaviour of energy (or carbon) and biogeochemical networks in coastal ecosystems are evident from the results obtained from ecological network analysis.  相似文献   

Nutrient compositions of cultured Thalassiosira rotula and Skeletonema costatum from the Jiaozhou Bay in China     

SHEN Zhiliang  WU Yulin  LIU Qun  YAO Yun 《海洋学报(英文版)》2008,27(4):147-155

Carbon, nitrogen, phosphorus, silicon composition of cultured two different sized phytoplankton common species of Thalazsiosira rotula and Skeletonema costatum from the Jiaozhou Bay were measured. Carbon, nitrogen, phosphorus, silicon contents in cell were obvious higher in T. rotula than in S. costatum, but the percents of nitrogen, phosphorus, sihcon contents in cell dry mass in T. rotula were lower than those in S. costatum. The dry mass concentrations of nitrogen,phosphorus, silicon in S. costatum were much higher than those in T. rotula, particularly silicon, the former was 6. 4 times of the latter, showing that S. costatum could more assimilate these elements. Especially, S. costatum had competitive dominance for assimilating silicon, which is beneficial to its becoming a major dominant species in relative short silicon of the Jiaozhou Bay. There were some differences in numerical value of nutrient ratios both laboratory-cultured phytoplankton and different sized suspended particulates （ mainly phytoplankton） in the Jiaozhou Bay, which was caused by the changes of environment. High contents of carbon, nitrogon and relative low phosporus, sil- icon, high molar ratio of nitrogen to phosphorus （far higher than Redfield value） and low ratio of silicon to phosphorus and silicon to nitrogen （far lower than Redfield values） in the two diatoms and different sized suspended particulates were consistent with those in the seawater. Relative short silicon in the seawater and phytoplankton showed that silicon was possibly affectting phytoplankton growth in the Jiaozhou Bay.  相似文献   

The invasion of the intertidal canopy-forming alga Fucus serratus L. to southwestern Iceland: Possible community effects     

Agnar Ingólfsson 《Estuarine, Coastal and Shelf Science》2008

The intertidal serrated wrack, Fucus serratus L. (Fucales: Phaeophyceae), has become an abundant canopy-forming alga along a ca. 100 km stretch of shore in southwestern Iceland in the last century. Its distribution has not changed noticeably since a survey in 1975/1976. Many experimental studies have shown that canopy-forming algae can have profound effects on the community structure. Although such experiments involving F. serratus are few it was decided to test predictions from these experiments on a geographical scale by comparing community compositions within the area where F. serratus is a dominant algae (since at least 1975/1976) with an adjacent area of similar size where F. serratus is absent (with a single exception without consequences). The work is based on measurements on some 372 stations in the F. serratus area, termed region A, and 227 stations from the F. serratus-free area, termed region B. Percentage cover of algae and sessile invertebrates was estimated on 2 m² on each station and animals collected from 800 cm² from each station. The vertical distribution of F. serratus was most similar to that of Fucus distichus and the two species often grew intermingled on the lower part of the shore. F. serratus appeared to have reduced the cover of F. distichus in the lowermost part of the shore, while having little or no effect on other canopy-forming species. The low abundance of Semibalanus balanoides in the F. serratus area (region A) is in line with experiments showing detrimental effect on this barnacle by whiplash of F. serratus. In general algal grazers were more abundant in region A, consistent with the greater attractiveness of F. serratus than other canopy-forming species to grazers, although this may be partly explained by the abundance of understorey algae in region A.  相似文献   

The meridional phosphine distribution in Saturn's upper troposphere from Cassini/CIRS observations     

L.N. Fletcher  P.G.J. Irwin  G.S. Orton  S.B. Calcutt  R. de Kok  F.W. Taylor 《Icarus》2007,188(1):72-88

The Cassini Composite Infrared Spectrometer (CIRS) has been used to derive the vertical and meridional variation of temperature and phosphine (PH₃) abundance in Saturn's upper troposphere. PH₃ has a significant effect on the measured radiances in the thermal infrared and between May 2004 and September 2005 CIRS recorded thousands of spectra in both the far (10-600 cm⁻¹) and mid (600-1400 cm⁻¹) infrared, at a variety of latitudes covering the southern hemisphere. Low spectral resolution (15 cm⁻¹) data has been used to constrain the temperature structure of the troposphere between 100 and 500 mbar. The vertical distributions of phosphine and ammonia were retrieved from far-infrared spectra at the highest spectral resolution (0.5 cm⁻¹), and lower resolution (2.5 cm⁻¹) mid-infrared data were used to map the meridional variation in the abundance of phosphine in the 250-500 mbar range. Temperature variations at the 250 mbar level are shown to occur on the same scale as the prograde and retrograde jets in Saturn's atmosphere [Porco, C.C., and 34 colleagues, 2005. Science 307, 1243-1247]. The PH₃ abundance at 250 mbar is found to be enhanced at the equator when compared with mid-latitudes. At mid latitudes we see anti-correlation between temperature and PH₃ abundance at 250 mbar, phosphine being enhanced at 45° S and depleted at 25 and 55° S. The vertical distribution is markedly different polewards of 60-65° S, with depleted PH₃ at 500 mbar but a slower decline in abundance with altitude when compared with the mid-latitudes. This variation is similar to the variations of cloud and aerosol parameters observed in the visible and near infrared, and may indicate the subsidence of tropospheric air at polar latitudes, coupled with a diminished sunlight penetration depth reducing the rate of PH₃ photolysis in the polar region.  相似文献   

Winter distribution of euphausiids (Euphausiacea) in the Barents Sea (2000–2005)     

Natalia G. Zhukova  Valentina N. Nesterova  Irina P. Prokopchuk  Galina B. Rudneva 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(21-22):1959

The purpose of the study is to analyze the state of the Barents Sea euphausiids populations in the warm period (2000–2005) based on the study of their structure dynamics and distribution under the influence of abiotic and biotic factors. For estimation of their aggregations in the bottom layer, the traditional method was used with the help of the modified egg net (0.2 m² opening area, 564 μm mesh size). The net is used for collecting euphausiids in the autumn–winter period when their activity is reduced, which results in high-catch efficiency. The findings confirmed the major formation patterns of the euphausiids species composition associated with climate change in the Arctic basin. As before, in the warm years, one can see a clear-cut differentiation of space distribution of the dominant euphausiids Thysanoessa genus with localization of the more thermophilic Thysanoessa inermis in the north-west Barents Sea and Thysanoessa raschii in the east. The major euphausiids aggregations are formed of these species. In 2004, the first data of euphausiids distribution in the northern Barents Sea (77–79°N) were obtained, and demonstrated extremely high concentrations of T. inermis in this area, with the biomass as high as 1.7–2.4 g m⁻² in terms of dry weight. These data have improved our knowledge of the distribution and euphausiids abundance during periods of elevated sea-water temperatures in the Barents Sea. The oceanic Atlantic species were found to increase in abundance due to elevated advection to the Barents Sea during the study period. Thus, after nearly a 30-year-long absence of the moderate subtropical Nematoscelis megalops in the Barents Sea, they were found again in 2003–2005. However in comparison with 1960, the north-east border of its distribution considerably shifted to 73°50′N 50°22′E. The portion of Meganyctiphanes norvegica also varied considerably—from 10% to 20% of the total euphausiids population in the warm 1950s–1960s almost to complete disappearing in 1970–1990s. The peak of this species’ occurrence (18–26%) took place in the beginning of warm period (1999–2000) after a succession of cold years. The subsequent reduction of the relative abundance of M. norvegica to 7% might have been mostly caused by fish predation during a period of low population densities of capelin. This high predation pressure may therefore have been mediated both by other pelagic fishes (i.e. herring, blue whiting, polar cod) but also by demersal fishes such as cod and haddock. Similar sharp fluctuations in the capelin stock (the major consumer of euphausiids) created marked perturbations in the food web in the Barents Sea in the middle 1980s and the early 1990s.  相似文献   

Enceladus' plume: Compositional evidence for a hot interior     

Dennis L. Matson  Julie C. Castillo  Torrence V. Johnson 《Icarus》2007,187(2):569-573

The combined observations of Saturn's moon Enceladus by the Cassini CAPS, INMS and UVIS instruments detected water vapor geysers in which were present molecular nitrogen (N₂), carbon dioxide (CO₂), methane (CH₄), propane (C₃H₈), acetylene (C₂H₂), and several other species, together with all of the decomposition products of water. We propose that the presence of N₂ in the plume indicates thermal decomposition of ammonia, and hence high temperatures in the interior of the moon (e.g., 500 to 800 K). Such an environment also appears to be suitable for the production of methane (CH₄) from carbon monoxide (CO), or carbon dioxide (CO₂). The presence of C₂H₂ and C₃H₈ strongly suggest that catalytic reactions took place within a very hot environment. The internal environment of Enceladus is inferred to be or have been favorable for aqueous, catalytic chemistry. This permits the synthesis of many complex organic compounds that could be detected in future Cassini observations.  相似文献