‘Filament’ marker beds in the Karababa-A Member (Turonian) of the Arabian platform,SE Turkey: Palaeo-environmental significance,stratigraphy and correlation potential     

O. Mülayim  I.O. Yilmaz  B. Sari  B. Ferré 《Proceedings of the Geologists' Association. Geologists' Association》2021,132(2):188-198

A ‘filament’ event bed/level corresponds to the occurrence of thin elongate calcitic, shells, or plates of pelagic, bivalve or crinoidal, origin, within pelagic, laminated and organic-matter rich limestones. These organic-rich limestones had been generally deposited under hypoxic/anoxic conditions in an outer-ramp environment. These thin elongate, bivalve shells, or crinoidal plates, are found broken in small pieces, disintegrated, or simply preserved parallel to bedding as almost complete specimens. Such ‘filament’ beds were spotted in SE Turkey in deposits, namely the Karababa-A Member, around the Cenomanian-Turonian boundary (C/TB) and above. On a global scale, these filament event beds illustrate sea-level rise related to eustacy and/or climatic change. The abundance of filaments close to the C/TB is a biological marker of high organic productivity resulting from a climatic change to warmer conditions. The prevailing higher sea-level conditions were then favourable to the accumulation and preservation of organic-rich facies, characteristic of the Oceanic Anoxic Event 2 (OAE2). Using both biostratigraphic and carbon isotopic data, those deposits were dated from the latest Cenomanian-Turonian age. ‘Filament’ event beds were recorded in the same order, except for some small differences. A good number of these bio-events are global. Consequently, on a global scale, they are susceptible to constrain the C/TB, especially the base of the Turonian stage, with a significant degree of confidence.  相似文献   

Large 14C age offsets between the fine fraction and coexisting planktonic foraminifera in shallow Caribbean sediments     

《Quaternary Geochronology》2017

Absolute chronologies in paleoceanographic records are often constructed using the ¹⁴C dating of coarse fraction foraminifera (>150 μm). However, due to processes such as changes in sediment sources or abundances, sedimentation rates, bioturbation, reworking, the adsorption of modern carbon, etc., several studies conducted in different environmental settings have shown time-lags between records obtained from various granulometric fractions. In this study, we examined temporal phasing between the coarse foraminifera and fine fractions by studying changes in the abundances of δ¹⁸O, the ¹⁴C ages of the planktonic foraminifera Globigerinoides ruber (G. ruber, 250–350 μm), and the sediment fine fraction (<63 μm) over the last 45 ka in a core obtained from the northern Caribbean Sea. All of the records were found to be in phase during part of the Holocene (at least for the last ≈6 ka). As determined from δ¹⁸O records and ¹⁴C ages, the fine fraction was younger than G. ruber during the Last Deglaciation (of 1.89 ka). The coupling between bioturbation and changes in the fine fraction, and G. ruber abundances, as tested using a numerical model of the bioturbation record within a mixed-layer depth of 8 cm, was sufficient to explain the results. ¹⁴C age discrepancies increased from 5.64 to 8.5 ka during Marine Isotopic Stages (MIS) 2 and 3, respectively. These chronological discrepancies could not be explained by only one process and seemed to result from the interplay between mechanisms: size-differentiated bioturbation (for 1.5 to 2.5 ka), the adsorption of modern atmospheric CO₂ (for 3.04 to 5.92 ka), and variations in sedimentological processes that influenced the fine carbonate fraction. However, even if variations in the mineralogical composition of the fine carbonate fraction were identified using scanning-electron microscopy observations, X-ray diffraction measurements, and geochemical analyses (the mol % MgCO₃ of magnesian calcite and the Sr/Ca ratio of the bulk fine fraction), they can not account for the observed age differences. The results presented for core MD03-2628 extend beyond this case study because they illustrate the need for a detailed characterization of the various size fractions prior to paleoclimate signal interpretations, especially for chronological studies.  相似文献   

热带西太平洋Y3和M2海山微食物网主要类群生态分布与比较   总被引：2，自引：0，他引：2  

赵丽  赵燕楚  王超锋  张武昌  孙晓霞  李学刚  赵苑  肖天 《海洋与湖沼》2017,48(6):1446-1455

2014年12月和2016年3月分别对热带西太平洋Y3海山(中层海山)和M2海山(浅海山)微食物网主要类群(包括聚球藻、原绿球藻、微微型真核浮游生物、异养细菌和浮游纤毛虫)丰度和生物量垂直分布进行了研究。结果表明,Y3和M2海山水文环境比较相似但略有区别,叶绿素最大值层(DCM)分别在75—100m和110m水层,微食物网各主要类群在垂直尺度上的分布与叶绿素a浓度紧密相关。其中浮游纤毛虫呈现"双峰型"模式,即丰度高值出现在表层和DCM层;原绿球藻和微微型真核浮游生物呈现"单峰型"模式,丰度高值出现在DCM层;聚球藻和异养细菌峰型相对不显著,DCM层以浅丰度较高,DCM层以深丰度明显降低。分析其原因,可能是受到温度、光照和营养盐的共同影响。Y3和M2海山微食物网结构的垂直变化不完全一致。其中,Y3海山30m以浅和150m以深异养细菌生物量占绝对优势,75—100m水层自养型生物(原绿球藻和微微型真核浮游生物)占绝对优势;M2海山75m以浅和200m以深异养细菌占绝对优势,110—150m自养型生物占绝对优势。M2海山自养型生物占优势的水层要明显深于Y3海山,可能与它们的海山类型和采样季节不同有关。  相似文献   

Dynamics of phytoplankton associations in three reservoirs in northeastern Brazil assessed using Reynolds’ theory     

Ênio Wocyli Dantas  Maria do Carmo Bittencourt-OliveiraAriadne do Nascimento Moura 《Limnologica》2012,42(1):72-80

The aim of the present study was to evaluate the influence of seasonality on the behavior of phytoplankton associations in eutrophic reservoirs with different depths in northeastern Brazil. Five collections were carried out at each of the reservoirs at two depths (0.1 m and near the sediment) at three-month intervals in each season (dry and rainy). The phytoplankton samples were preserved in Lugol's solution and quantified under an inverted microscope for the determination of density values, which were subsequently converted to biomass values based on cellular biovolume and classified in phytoplankton associations. The following abiotic variables were analyzed: water temperature, dissolved oxygen, pH, turbidity, water transparency, total phosphorus, total dissolved phosphorus, orthophosphate and total nitrogen. The data were investigated using canonical correspondence analysis. The influence of seasonality on the dynamics of the phytoplankton community was lesser in the deeper reservoirs. Depth affected the behavior of the algal associations. Variation in light availability was a determinant of changes in the phytoplankton structure. Urosolenia and Anabaena associations were more abundant in shallow ecosystems with a larger eutrophic zone, whereas the Microcystis association was more related to deep ecosystems with adequate availability of nutrients. The distribution of Cyclotella, Geitlerinema, Planktothrix, Pseudanabaena and Cylindrospermopsis associations was different from that seen in subtropical regions and the substitution of these associations was related to a reduction in the eutrophic zone rather than the mixture zone.  相似文献   

Acute effects of heavy metals on the expression of glutathione-related antioxidant genes in the marine ciliate Euplotes crassus     

Se-Hun Kim  Se-Joo Kim  Jae-Seong Lee  Young-Mi Lee 《Marine pollution bulletin》2014

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Biofilm Formation by Microorganisms Isolated from Paper Mill Effluent and its Public Health Implications     

Priyanka Lal  Vishnu Agarwal  Parul Pruthi  Swaranjit Singh Cameotra  Vikas Pruthi 《洁净——土壤、空气、水》2008,36(12):963-968

The microbiological assessment of biofilm formation from paper mill effluent discharged through a pipeline revealed a maximum microbial count for Pseudomonas (5·10⁶ cfu/mL) followed by Staphylococcus (4·10⁶ cfu/mL), Bacillus (8.2·10⁵ cfu/mL), Burkholderia (7.2·10⁵ cfu/mL), Enterobacter (5.3·10⁴ cfu/mL), Acinetobacter (4.1·10³ cfu/mL), Alcaligenes (1.2·10² cfu/mL) and Klebsiella (0.8·10² cfu/mL) species. Among these species, the maximum biofilm formation was observed after 24 h of incubation by Pseudomonas sp. using a crystal violet (CV) assay. This isolate was later identified by 16S rRNA amplification to be Pseudomonas aeruginosa PME1. Extracellular polymeric substances (EPS) of P. aeruginosa PME1 in the biofilm showed a reduction in total carbohydrate content (42%) with increased protein (9.0%), hexosamine (3.0%) and uronic acid (1.7%) content as compared to its planktonic form. Antimicrobial susceptibility testing revealed that P. aeruginosa PME1 biofilms were 17, 24, 27, 30, and 32 times more resistant to cefotaxime, imipenem, ceftazidime, tazobactam and piperacillin, respectively, than their free flowing counterparts.  相似文献   

Morphogenetic processes in division of Uronemella filificum (Ciliophora, scuticociliatida)     

MA Hongwei  Song Weibo  Ma Honggang 《中国海洋大学学报(英文版)》2002,1(2):140-144

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Morphogenetic Processes in Division of Uronemella filificum (Ciliophora, Scuticociliatida)     

Ma Hongwei  SONG Weibo  MA Honggang 《中国海洋大学学报(英文版)》2002,1(2)

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Acute toxicities of potassium permanganate, formalin, and Lugol’s iodine solution to a marine ciliate, Pleuronema coronatum (ciliophora, scuticociliatida)     

Qiu Yantao  Song Weibo 《中国海洋大学学报(英文版)》2002,1(2):211-214

Acute toxicities of potassium permanganate, formalin, and Lugol’s iodine solution to a commonly occurred marine ciliate Pleuronema coronatum (Ciliophora, Scuticociliatida) were measured. Linear regression analysis of the results highlighted the close relationships between doses of the medicines and mortalities of the organisms, thus providing a capability to predict toxicity effects from the dose. Toxic effects of the medicines on the ciliates were described in the present paper, and the median lethal concentrations (LC₅₀ values) were given. Results of measurements indicated that 2 h-LC₅₀ and 12 h-LC₅₀ values of formalin on P. coronatum were 59.00×10⁻⁶ and 43.57×10⁻⁶, while those of Lugol’s solutions were 90.13 and 67.84×10⁻⁶ respectively. The tolerance of P. coronatum to formalin is apparently lower than that to Lugol’s iodine solution and potassium permanganate is a suitable medicine to kill ciliates in short time.  相似文献   

Complementary Notes on a ‘Well-known’ Marine Heterotrichous Ciliate, Folliculinopsis producta (Wright, 1859) Frauré-Fremiet, 1936 (Protozoa, Ciliophora)     

JI Daode  LIN Xiaofeng  SONG Weibo Laboratory of Protozoology  Key Laboratory of Mariculture  Ocean University of China  Qingdao  P..R.China 《中国海洋大学学报(英文版)》2004,(1)

1　Introduction　Folliculina likeciliatesarecommonlyfoundinlit toralzonesandareeasilyrecognizedbytheirlargesi zesandspecialstructures (i.e.vase shapedloricaandperistomiallobe) .Tillnow ,dozensofspecieshavebeenreportedworldwide (Kahl,1 932 ;Faur啨Fremiet,1…  相似文献