南海某些表层沉积硅藻的分布及其古环境意义

本文通过对南海表层沉积物样品的硅藻分析,试图揭示南海某些表层沉积硅藻的分布规律,以便为南海古海洋学研究提供科学依据。研究发现,Thalassionema nitzshioides为南海地区表层沉积硅藻的优势种,且其百分含量无明显的区域差异,体现了南海与周围海洋水体交换相对较弱的特征。除此之外,南海表层沉积硅藻的分布主要受到海洋环流的影响,表现在黑潮暖流、印度洋暖水的入侵以及沿岸流对南海表层沉积硅藻分布的影响。其中,Nitzshia marina, Azpeitia neocrenulata , Azpeitia africana , Rhizosolenia bergonii等暖水硅藻可作为黑潮暖流及印度洋暖水入侵南海强度的指标种。而Cyclotella stylorum , Cyclotella striata , Diploneis bombus , Traychneis aspera , Tabularia tabulata等则可看作判断沿岸流对南海水体影响强度的标志种。     

中国海表层沉积生物硅含量与硅藻丰度空间分布规律

生物硅是海洋硅循环及古海洋学的主要研究对象,主要由硅藻、放射虫、硅鞭藻和海绵骨针等硅质生物壳体组成。由于硅藻是海洋硅质生物以及海洋浮游植物群落的优势种群,故生物硅常被用作判断硅藻生产力甚至整个海洋初级生产力的重要指标。相对于硅藻的鉴定和统计分析,生物硅含量分析有其便利快捷的明显优势,然而生物硅组成的复杂性使其在现代海洋学及古海洋学的应用中存在一定的风险,但是目前有关生物硅含量与硅藻生产力的相关性及其对现代海洋和古海洋研究的影响尚未引起足够的关注。本文通过收集整理大量已发表的我国边缘海表层沉积物生物硅与硅藻的相关研究成果,在此基础上探讨了我国边缘海沉积生物硅含量与硅藻丰度的空间分布及其耦合性,及其对海洋生产力研究的指示意义。从现有的研究数据可以看出东中国海,主要包括东海和黄海,以及南海陆架浅海区表层沉积生物硅含量与硅藻丰度均无明显的空间变化规律,而南海表层沉积生物硅含量与硅藻丰度均表现为由陆架向海盆逐渐增加的趋势,与水深呈明显正相关关系。整个中国边缘海沉积生物硅含量和硅藻丰度的空间分布格局与现代水体初级生产力的分布格局差异明显,陆源输入的稀释作用对此起到了重要影响。通过进一步的分析发现,南海表层沉积硅藻对生物硅的贡献还存在明显的区域变化,表现为在陆坡及其邻近海盆区硅藻对沉积生物硅的贡献较大,而在深海海盆区放射虫及其他硅质生物对生物硅的贡献不容忽视。为了更好地利用生物硅、硅藻及其他相关参数研究边缘海硅循环及古海洋环境演变,未来需要更多地关注除硅藻以外的硅质生物,如硅鞭藻、海绵骨针等,对生物硅的贡献及其对海洋硅的生物地球化学过程的影响。     

福建敖江口表层沉积硅藻空间分布特征

为探讨福建敖江口表层沉积硅藻空间分布特征,2019年7月对敖江口进行表层沉积硅藻的采样调查,并研究了硅藻与环境因子的关系。结果表明,从13个站点共检出硅藻114种,隶属于39属。硅藻丰度具有从河口向外海先减少后增加的变化特征。聚类分析表明,主要硅藻属种可划分为淡水种组合带和半咸水-咸水种组合带。典型对应分析（CCA）表明,表层海水温度和盐度是影响硅藻分布的主要环境变量。河口区盐度相对较低,主要分布淡水种双面曲壳藻、优美曲壳藻和颗粒沟链藻;外海区北部盐度相对较高,主要分布咸水种流水双菱藻;外海区南部盐度相对较低,主要分布淡水种优美曲壳藻和颗粒沟链藻;滩涂的沉积物较粗,主要分布优美曲壳藻。此外,河口区和外海区南部可能存在一定的水体污染。     

西菲律宾海盆表层沉积硅藻分布特征

本文对西菲律宾海盆186个表层沉积硅藻样品进行分析,共鉴定出硅藻68个种和变种,隶属于26个属。西菲律宾海盆硅藻总平均丰度为1 111.5粒/g。硅藻属种主要以外洋暖水种和广温种为主,其中Azpeitia nodulifera的百分含量最高,其次是Hemidiscus cuneiformis,Coscinodiscus africanus,Thalasiosira excentrica和Nitzschia marina,以上5种硅藻占所有硅藻百分含量的88%以上。西菲律宾海盆大部分站位热带远洋种含量均高于20%,这与现今黑潮暖流流经该区相吻合。通过主成分分析,该海域表层沉积硅藻可分划为3个区域。此外,整个菲律宾海盆大部分海域都分布有Ethmodiscus rex,但西菲律宾海盆的分布范围更广。     

东海南部陆缘(莆、泉段)全新世沉积硅藻

对东海南部陆缘莆田、泉州地区两口钻井岩芯系统的沉积硅藻研究,共发现33属117种（或变种）硅藻化石,根据剖面硅藻组合特征的变化,结合计算机的对应分析结果划分了硅藻带,建立该区全新世的7个硅藻组合序列,恢复当时古环境演变的7个阶段,填补该区沉积硅藻系统研究的空白,丰富了海陆过渡沉积硅藻的研究。     

广西防城港湾表层沉积硅藻分布特征

本文对广西防城港湾23个表层沉积物样品中硅藻进行分析,鉴定出硅藻170种,分属50属。其中Thalassionema nitzschioides是本区域内最为丰富的硅藻种类。分析结果表明,防城港湾表层沉积硅藻分布主要受到海水盐度的影响,其中Cyclotella striata,C.stylorum,T.nitzschioides,T.frauenfeldii可以作为高盐度海水环境的指示种,Cocconeis disculus多出现于陆上淡水与外洋海水交汇的半咸水海域,而Achnanthes levanderi,Navicula minima,N.minuscula则可以很好地指示低盐度环境。     

长江口及东海春季底栖硅藻、原生动物和小型底栖生物的生态特点

利用Ludox-QPS方法并结合沉积环境因子的综合分析,研究了2011年4月采自长江口及东海10个站位以底栖硅藻、纤毛虫和异养小鞭毛虫为代表的微型底栖生物及小型底栖生物的组成、丰度和生物量、分布及生态特点。结果表明,底栖硅藻的丰度 (5.92 ? 104 ind/10 cm2) 和生物量 (83.29 ?g C/10 cm2) 远高于纤毛虫 (丰度为1036 ind/10 cm2,生物量为3.33 ?g C/10 cm2)、异养小鞭毛虫 (丰度为4451 ind/10 cm2,生物量为2.51 ?g C/10 cm2) 和小型底栖生物 (丰度为1947 ? 849 ind/10 cm2,生物量为49.01? 22.05 ?g C/10 cm2)。在鉴定出的11个小型底栖生物类群中,线虫占小型底栖生物总丰度的90%和总生物量的37%。底栖硅藻生物量在长江口及东海海域呈由近岸向外海逐渐降低的分布特点,而底栖纤毛虫、异养小鞭毛虫及小型底栖生物的分布则正相反。在垂直分布上,76%的硅藻和80%的线虫分布在0–2 cm沉积物表层,仅1%的硅藻和6%的线虫分布在5–8 cm分层。统计分析表明,底栖硅藻的现存量与沉积物中叶绿素a含量呈极显著的正相关,与底层水温度呈弱的正相关;该海域底栖原生动物和小型底栖生物的分布受多个因子而非单一环境因子的共同作用。对比分析表明,长江口及东海单位体积沉积物中的硅藻丰度较水体中的硅藻丰度高2个数量级,沉积物中相当部分的叶绿素a含量可能系底栖硅藻所贡献;表层8 cm沉积物中纤毛虫的丰度约是上层30 m水柱中纤毛虫丰度的30倍,生物量约是后者的40倍。尽管纤毛虫在生物量上远小于小型底栖生物,但其估算的生产力约是后者的3倍;而异养小鞭毛虫由于个体更小,其周转率可能较纤毛虫更高。长江口及东海陆架区原生动物和小型底栖生物的高现存量及生产力预示着其在该海域生态系统中的重要作用。     

黄海表层沉积物的孢粉、藻类组合

黄海是位于我国大陆与朝鲜半岛之间的一个陆架浅海。其表层沉积的孢粉、藻类分布可分为四个孢粉区:1.蒿—藜—禾本科孢粉区;2.松—栎—草本花粉—刺球藻孢粉区;3.松—椭球藻—栎—蕨属—凤尾蕨孢粉区;4.松—栎—凤尾蕨—椭球藻孢粉区。通过整个海区表层沉积的孢粉、藻类研究,着重探讨了:表层沉积孢粉组合和陆缘植被的关系;再沉积孢粉化石与海盆物质来源;刺球藻、椭球藻的分布与水深的关系;硅藻分布与深度、水团的关系;红树植物花粉与海流。     

格陵兰西部海域表层沉积硅藻分布与海冰覆盖率关系探讨

格陵兰西部海域35个站点的表层沉积硅藻与月平均海冰覆盖率的典型对应分析(CCA)结果表明:4月、10月和12月平均海冰覆盖率是该海域硅藻分布的主要环境影响因子。根据分析结果得到的属种与站点得分情况,将格陵兰西部海域划分为4个区域:拉布拉多海海冰覆盖率最低,主要分布暖水种;戴维斯海峡多为冷水或极地硅藻分布;北部的巴芬湾海冰种开始大量出现,与该海域12月平均海冰覆盖率较高相关;Disko湾内10月平均海冰覆盖率最高,对应于海冰种、部分极地种和冷水种的高百分含量。     

东海陆缘(浙南段)晚第四纪硅藻的发现及古环境分析

东海陆缘(浙南段)温州沿海以往第四纪沉积已开展了一些研究,见有丰富的有孔虫、孢粉等生物化石,但未发现硅藻。本项研究在温州CH6井、台州CH5井岩心中发现了大量硅藻化石,本文以温州CH6井丰富的硅藻化石为依据,建立了晚第四纪硅藻组合序列,划分为12个硅藻带,并恢复其古环境演替,根据四个AMS ^14C年代数据,其时代属早、中全新世。     

Distribution patterns of diatom surface sediment assemblages in the Laptev Sea (Arctic Ocean)

The modern diatom distribution in the Laptev Sea, Arctic Ocean, was investigated in 89 surface sediment samples. Diatom concentrations are relatively low showing values between 0.01×10⁶ and 6.7×10⁶ valves per gram dry sediment. Based on a factor analysis using seventeen taxa or taxa groups five diatom surface sediment assemblages can be defined: the ice diatom assemblage of the central region of the Laptev Sea, the Chaetoceros assemblage of the eastern and southeastern shelf, the Thalassiosira antarctica assemblage of the continental slope and deep sea, the freshwater diatom assemblage in the vicinity of river mouths and deltas, and the Thalassiosira nordenskioeldii assemblage which shows a patchy occurrence on the central Laptev Sea shelf. The distribution pattern of diatom assemblages in surface sediment is significantly related to oceanographic conditions of surface water masses. The main factors controlling the distribution of diatoms in the Laptev Sea are the riverine freshwater input during the summer which strongly affects the salinity conditions, and the sea-ice extent. Furthermore, the composition of the Thalassiosira antarctica assemblage of the continental slope is largely influenced by dissolution and lateral transport processes.     

Diatom surface sediment assemblages around Iceland and their relationships to oceanic environmental variables

Canonical correspondence analysis of diatoms from surface sediment samples and oceanographic environmental variables shows that summer and winter sea-surface temperatures, water depth and winter sea-surface salinity are the main environmental factors affecting diatom distribution around Iceland. Of these, summer sea-surface temperature is the most important. Five diatom assemblages are distinguished and the distribution of these assemblages is clearly correlated with oceanic current patterns in the region. The sea-ice diatom assemblage is limited to the area where the East Greenland Current (Polar Water) has its strongest influence, and the cold diatom assemblage is basically controlled by the less cold East Icelandic Current (Modified Polar Water). The mixing diatom assemblage results from the interaction between the cold East Greenland and East Icelandic Currents and the warm Irminger Current. The warm diatom assemblage is located in the area dominated by the Irminger Current and may be used as an indicator of warm-water masses (Atlantic Water). The coastal diatom assemblage is the only one strongly influenced by both water depth and summer water temperatures.     

Diatom flora of surface sediments of the Amur River Estuary and adjacent areas of the Sea of Japan and the Sea of Okhotsk

Results of the study of the diatom flora from surface sediments of the Amur River Estuary and adjacent areas of the Sea of Japan and the Sea of Okhotsk are presented for the first time. This study revealed high species diversity of diatoms: 287 diatom taxa belonging to 80 genera were identified in 35 surface sediment samples. The ecological composition of diatom assemblages allowed us to evaluate the influence of the Amur River runoff on adjacent areas of the seas.     

Comparison of contemporary and fossil diatom assemblages from the western Antarctic Peninsula shelf

During the past ten years, the Antarctic Peninsula has been identified as the most rapidly warming region of the Southern Hemisphere and it is important to place this warming in the context of the natural climate and oceanographic variability of the recent geological past. Many biological proxies, such as marine diatom assemblages, have been used to determine Southern Ocean palaeoceanographic conditions during the Late Quaternary, however, few investigations have attempted to link observations of modern floras with the fossil record. In this study we examine a suite of modern austral spring (December 2003) and summer (February 2002) surface water samples from along the western Antarctic Peninsula (WAP) continental shelf and compare these to core-top, surface sediment samples. Using detrended correspondence analysis (DCA) and principal component analysis (PCA) of diatom abundance data we investigate the relationship of contemporary diatom floras with the fossil record. This multivariate analysis reveals that our modern assemblages can be divided into three groups: summer southern WAP sites, summer northern WAP sites, and spring WAP sites. Sea surface temperature (SST) is an important environmental variable for explaining seasonal differences in diatom assemblages between spring and summer, but sea surface salinity (SSS) is more important for understanding temporally-equivalent regional variations in assemblage. Our summer diatom samples are more reminiscent of early season assemblages, reflecting the unusually late sea ice retreat from the region that year. When the modern assemblages are compared to the fossil record, it is clear that most of the important diatoms from the summer assemblage are not preserved into the sediments, and that the fossil record more closely reflects spring assemblages. This observation is important for any future attempts to quantitatively reconstruct palaeoceanographic conditions along the WAP during the Late Quaternary and highlights the need for many more such studies in order to address longer timescales, such as interannual variability, in the context of the fossil record.     

Spatial variations in the water quality of Lough Erne, Northern Ireland, on the basis of surface sediment diatom analysis

SUMMARY. 1. Constrained cluster analysis of thirty-five surface sediment diatom assemblages shows that Lough Erne, a complex multi-basin lake in Northern Ireland, can be sub-divided into four main zones.
2. All areas of the lake system have planktonic diatoms typical of eutrophic lakes but the lack of small Stephanodiscus species in zone 4 suggests that this area of the system is least productive.
3. Surface sediment diatom assemblages can be used to assess spatial variations in complex lake systems and can thereby be used as a guide to the choice of sites for water quality monitoring and sediment coring.     

Correlation of surface sediment diatoms with the present lake water pH in 28 Algoma lakes,Ontario, Canada

The surface sediment diatom analysis of 28 Algoma lakes (pH 4.40–8.13) indicates that even though each lake has a widely different aquatic environment and characteristic diatom assemblage, a definite relationship exists between the lake water pH and their diatom assemblages. In the acidic lakes acidobiontic and acidophilous diatom species predominate whereas in circumneutral and alkaline lakes circumneutral and alkaliphilous diatoms were most common. Cluster analysis of the pH indicator diatom assemblages grouped the study lakes into three distinct cluster groups. These groups also closely corresponded to lake water pH. On the basis of published ecological information as well as their presence in our study lakes, the pH indicator status of a number of diatom taxa have been discussed. A detailed listing of the diatom taxa identified and their pH indicator status is provided in order to facilitate their use in future diatom-inferred pH studies.     

Diatom taphocoenoses in the coastal upwelling area off South West Africa

The diatom floral composition of 124 sediment samples from the South East Atlantic records the influence of coastal upwelling on sediment composition off South West Africa. Inner shelf samples between 19° and 24°S are rich in diatom valves and the patterns of diatom species distribution in these samples are related to the coastal upwelling process. Comparison with recent phytoplankton data shows that the sediment assemblages preserve many of the important species of the diatom biocoenoses, including Chaetoceros (resting spores), Delphineis karstenii, Thalassiosira eccentrica, and Thalassionema nitzschioides. Delphineis karstenii, a pioneer species in enriched coastal water, occurs nearshore and Chaetoreros resting spores are widespread, with highest relative abundance values in some more offshore samples. The abundance of the Thalassiosira eccentrica group and of Thalassionema nitzschioides in sediment samples in and near Walvis Bay reflects the recurrence of intense upwelling off this part of the coast. An abundance of large centric species has been reported in hydrological conditions characteristic of newly upwelled waters and, correspondingly, Actinocyclus octonarius and some large Coscinodiscus species occur in the sediments in nearshore patches or belts.