Lake levels in the southern Bolivian Altiplano (19°–21°S.) during the Late Glacial based on diatom studies     

Florence Sylvestre  Simone Servant-Vildary  Marc Fournier  Michel Servant 《International Journal of Salt Lake Research》1995,4(4):281-300

This study is focused on the endorheic Uyni-Coipasa Basin located in the southern Bolivian Altiplano. Stratigraphical and fossil diatom studies based on a detailed radiocarbon chrnology revealed six phases in water-level changes and paleosalinity variations. At 15,430±80 yr B.P., lacustrine conditions settled in the southern Bolivian Altiplano. A saline lake, characterized by benthic meso-metasaline species, reached +4 m altitude above the present bottom of the basin. After 15,430±80 yr B.P., the level rapidly rose to +27 m, as suggested by a tychoplanktonic mesosaline flora. Between 14,500 years and 13,000 years, finely lanminated sediments at +32 m contained successively a dominance of epiphytic mesosaline to hypersaline species and tychoplanktonic oligosaline diatoms, indicating weak fluctuations in water-level and salinity. At 13,000 years, strong changes in the diatom flora occurred; epiphytic oligo-hypersaline diatoms were replaced by planktonic meso-polysaline species. They indicate a deep salt lake (the lake reached +100 m). After 12,000 years, the lake level abruptly dropped, as suggested by fluviatile sediments with a benthic mesopolysaline diatom flora. The main lake was replaced by shallow saline ponds. A wet pulse occurred at 11,400 years, characterized by low water level (+7 m) and high salinity. This lacustrine phase remained until 10,400 yr B.P. These data indicate changes in Precipitation minus Evaporation (P-E). Our regional interpretations are based on a comparison with teh available data on the northern (Lake Titicaca) and southern (Lipez are) Bolivian Altiplano and on the northern Chilean Altiplano (Atacama Desert).  相似文献   

Human disturbance and trophic status changes in Crystal Lake, McHenry County, Illinois, USA   总被引：6，自引：0，他引：6  

Yangdong Pan  Richard Brugam 《Journal of Paleolimnology》1997,17(4):369-376

The paleolimnology (sediment chemistry, ²¹⁰Pb dating, pollen, and diatoms) of Crystal Lake, McHenry County, Illinois, USA was studied to investigate the impact of European settlement on lake trophic status. Pollen clearly indicates a vegetational shift from Quercus dominance to Ambrosia. ²¹⁰Pb dating suggests that the Ambrosia rise likely occurs around the 1840's, which is consistent with historical records on the European settlement in this area. Coincident with the vegetational shifts, several diatom species, Cyclotella meneghiniana, Fragilaria crotenensis, Asterionella formosa and Tabellaria fenestrata, all increase while C. comta decreases after the settlement. However, C. comta and Aulacoseira ambigua, two dominant species, remain abundant throughout the entire core. Their relative abundances at the surface sediments reach presettlement levels. It is hypothesized that Crystal Lake, a glacial lake rich in CaCO₃, may have been able to assimilate increases of phosphorus by coprecipitating phosphorus with CaCO₃. Such a 'buffering mechanism may be responsible for the lake's resistance to trophic changes or recovery following disturbance.  相似文献   

一株抗硅藻附着的海绵附生菌的鉴定及发酵条件优化          下载免费PDF全文

刘书宇  俞思羽  夏翊腾  靳翠丽  张立奎  周晓见 《应用海洋学学报》2016,35(4):499-506

为了从海绵共附生微生物中寻找天然高效抗污损活性物质,本文针对前期研究获取的4株具有显著抗硅藻附着的活性菌株进行活性验证和比较,选出其中最优菌株进行菌种鉴定及发酵条件优化.比较了活性菌株对小新月菱形藻(Nitzschia closterium)、咖啡双眉藻(Amphora coffeaeformis)、碎片菱形藻(Nitzschia frustulum)附着的抑制活性,确定菌株UST050418-715为最优菌株;通过16S r DNA的测序分析,结合平板的菌落形态和扫描电镜下菌体特征,鉴定活性菌株UST050418-715为短小芽孢杆菌(Bacillus pumilus).为优化该菌株的培养条件,选择了酵母粉、蛋白胨、Na Cl、p H值进行四因素三水平的正交实验,对菌株培养条件进行优化.发现选择的4个因素对应的菌株发酵产物对硅藻附着的抑制活性大小不同,影响显著性顺序是酵母粉蛋白胨Na Clp H值,综合菌株发酵产物活性、粗提物产量和菌株生长情况进行分析,确定菌株UST050418-715基于海洋2216E培养基的最佳发酵条件为:蛋白胨含量7.5 g/dm3,酵母粉含量3 g/dm3,Na Cl含量10.45 g/dm3,p H值9.5.  相似文献   

广东沿岸海域发生赤潮的硅藻种类   总被引：8，自引：0，他引：8  

李永振 《台湾海峡》2001,20(2):274-278

根据1990－1991年在广东沿岸海域采集的178份浮游植物样品的鉴定，产结合近几年在广东沿海河口湾海域几次浮游植物采样的分析资料，报告了广东沿岸海域硅藻赤潮生物47种，逐种列出了其生态习性和地理分布及在广东沿岸海域的分布情况。  相似文献   

南海北部15 kaBP以来表层海水温度变化:来自海洋硅藻的记录   总被引：3，自引：0，他引：3  

黄元辉  黄玥  蒋辉 《海洋地质与第四纪地质》2007,27(5):65-74

对西太平洋边缘海148个表层硅藻样品中菱形海线藻(Thalassionema nitzschioides)及其小形变种(Thalassionema nitzschioidesvar.parva)的分布与表层海水温度(SST)之间关系进行研究,将菱形海线藻小形变种与所有菱形海线藻百分含量的比值(简称硅藻Rparva值)视为温度指数,开展南海北部MD05-2904孔附近海域15kaBP以来表层海水温度变化研究。结果表明:(1)南海北部15 kaBP以来表层海水温度呈现明显的阶段性波动特点,即末次冰消期气候转暖过程中,12.9~11.5 kaBP前后温度略有下降,与新仙女木事件对应,全新世南海北部气候依次经历了升温期、高温期和降温期3个变化阶段;(2)全新世大暖期鼎盛期结束后,南海北部海水温度阶段下降,两次明显降温分别发生于4 kaBP前后和1.5 kaBP前后;(3)MD05-2904孔硅藻Rparva值时间序列曲线与董哥洞D4石笋δ18O曲线对比表明,南海北部表层海水温度变化与末次冰消期以来东亚季风强度变化关系较为密切。  相似文献   

南海深海表层沉积硅藻的分布   总被引：10，自引：1，他引：10  

陆钧 《海洋地质与第四纪地质》2001,21(2):27-30

定量分析了南海36个深海现代表层沉积样品中的硅藻，发现主要的种有Thalassionema nitzschilides、Chaetoceros messanensis、Coscinodiscus modulifer、Thalassionthrix longissima、Nitzschia marina和Cyclotella spp.。根据硅藻优势种含量、丰度等特征以及Q型聚类分析，大致划分为5个组合带，它们主要受温度、上升流等环境因素的影响。  相似文献   

Gradient responses of epilithic diatom communities in the Baltic Sea proper   总被引：1，自引：0，他引：1  

Anna Ulanova  Pauli Snoeijs   《Estuarine, Coastal and Shelf Science》2006,68(3-4):661

Diatom communities and assemblages are widely used as indicators of ecological change in aquatic environments and for reconstructing palaeo-environments. Good calibration data sets, directly linking changes in diatom composition to environmental factors, are needed for building reliable gradient models with high indicative value. Such models have a broad applicability because most diatom species have cosmopolitan distributions. This paper presents community analyses of brackish-water diatoms living on submerged stones in four areas of the Baltic Sea proper along the Swedish coast. The communities on the stones were composed of epilithic, epiphytic, epipelic, epipsammic and occasionally some pelagic species. Altogether, 158 quantitative samples were taken at 41 sites between 23 April and 11 May, 1990, and the data set contained 300 diatom taxa belonging to 75 genera. Species data were analysed with principal components analysis (PCA) and environmental factors were fitted passively by multiple regression analysis on the ordination results. Differences in community composition could be explained by variation in salinity (which was correlated with N:P and Si:P ratios and the occurrence of macroalgae on the stones), nutrient concentrations and variation in exposure to wave action (which was correlated to the occurrence of soft bottoms around the stones, water temperature and the occurrence of sand grains and macroalgae on the stones). Separate analyses for small taxa (cell biovolume <1000 μm³), for large taxa (cell biovolume ≥1000 μm³) and for small and large diatom taxa together showed that diatoms of different size classes respond differently to environmental variation.  相似文献   

杂色鲍苗大规模脱落死亡的初步研究     

王瑞旋  刘广锋  徐力文  王江勇  黎伟坚  陈毕生 《海洋科学》2007,31(4):53-57

研究了杂色鲍(Haliotis diversicolorReeve)鲍苗脱落死亡周期中水质、硅藻和细菌变化情况。结果显示,鲍苗脱落前各水质指标无明显变化,脱落前硅藻数量大幅度增加,以卵形藻(Cocconeisspp.)和舟形藻(Naviculaspp.)为主要种类。同时发现一株可疑致病菌,初步鉴定为溶藻弧菌(Vibrio alginolyticus)。实验表明水质等相关因子与鲍苗脱落无直接关系,而硅藻很可能是致病菌的“载体”,整个附着膜微环境与鲍苗存亡息息相关。  相似文献   

马里亚纳海槽区岩芯中浮游有孔虫和CaCO_3溶解及其影响溶解的因素     

高建西  周希林  鞠晓华 《海洋科学进展》1993,(2)

本文从浮游有孔虫壳体保存,数量,分异度值,底栖类/浮游类比率和CaCO_3含量诸方面讨论马里亚纳海槽区岩芯中溶解及其影响溶解的因素。  相似文献   

东海陆架晚第四纪沉积硅藻及其古海洋学意义   总被引：2，自引：0，他引：2  

李超  蓝东兆  方琦 《台湾海峡》2002,21(3):351-359

本文对东海陆架DG9617岩芯沉积硅藻进行了研究，共分析鉴定出97种和变种，有近10种硅藻在岩芯中连续分布，且有较高的含量，而其余种类含量极低，仅零星检出。根据该岩芯中产出硅藻种类、含量及硅藻丰度变化特征自下而上共划分出3个硅藻组合带及5个亚带。结合孢粉资料，对产出3个不同硅藻带岩芯的地层年代进行了对比研究，表明该岩芯所代表的地层年代为中－晚全新世，硅藻I组合带大致为大西洋期的沉积，硅藻Ⅱ组合带应为亚北方期的产物，而硅藻Ⅲ组合带与亚大西洋期对应。文中并对不同硅藻组合带产出时的古海洋环境进行了初步探讨。  相似文献