Reef reconstruction after extinction events of the latest ordovician in the Yangtze platform,South China

Summary Early Silurian reef reconstruction on the Yangtze Platform, in the northern part of the South China Block, is preceded by a combination of regional and global processes. During most of Ashgill time (Late Ordovician), the area was dominated by Wufeng Formation deep water graptolitic black shales. Reefs largely disappeard in the middle of the Ashgill Stage, from the northwestern margin of Cathaysian Land (southeastern South China Block), in advance of the Late Ordovician glaciation and mass extinction, due to regional sea-level changes and regional uplift, unrelated to the mass extinction itselt. Late Ordovician microbial mudmound occurrence is also found in the western margin of the Yangtze Platform, its age corresponding to theDicellograptus complexus graptolite biozone of pre-extinction time. On the Yangtze Platform, a thin, non-reef-bearing carbonate, the Kuanyinchiao Formation (=Nancheng Formation in some sites), thickness generally no more than 1m, occurs near several landmasses as a result of Hirnantian regression. Reappearance of the earliest Silurian carbonates consisting of rare skeletal lenses in the upper part of Lungmachi Formation, are correlated to theacensus graptolite biozone, early Rhuddanian of Shiqian, northeastern Guizhou, near Qianzhong Land. Carbonate sediments gradually developed into beds rich in brachiopods and crinoids in the lower part of Xiangshuyuan Formation, middle Rhuddanian. In the middle part of Xiangshuyan Formation, biostromes, containing abundant and high diversity benthic faunas such as corals, crinoids and brachiopods, show beginnings of reconstruction of reef facies. Substantial reef recovery occurred in the upper part of Xiangshuyuan Formation, lower Aeronian, as small patch reefs and biostromes. During the late Aeronian, carbonate sediments, especially reefs and reef-related facies, expanded on the upper Yangtze Platform, and radiation of reefs occurred in Ningqiang Formation, upper Telychian. The long period of reef recovery, taking several million years, remains difficult to explain, because redistribution of any refugia faunas would be expected to take place soon after the extinction. Reefs and reef-related facies subsequently declined after Telychian time due to regional uplift of the major portion of the Yangtze Platform. Carbonate facies are therefore uncommon in South China during the rest of Silurian time.     

Diverse radial symmetry among the Cambrian Fortunian fossil embryos from northern Sichuan and southern Shaanxi provinces,South China

The Cambrian Fortunian fossil embryos exhibit embryonic development of ancient animals and hence have important bearings on evolutionary developmental biology. They have radial symmetry, and may be early representatives of cnidarians. Here we report new material of three-dimensionally phosphatized fossil embryos from the Fortunian Kuanchuanpu Formation and coeval strata in northern Sichuan and southern Shaanxi provinces, South China. The new material includes previously reported fossil embryos assignable to Pseudooides prima with biradial symmetry or pseudo-hexaradial symmetry, Quadrapyrgites quadratacris with tetraradial symmetry, and Olivooides multisulcatus with pentaradial symmetry. Additionally, we recovered two new types of fossil embryos, i.e., Embryo I with hexaradial symmetry and Embryo II with octaradial symmetry, and they are tentatively suggested to represent new cnidarians. In contrast to the diverse radial symmetry of the Fortunian cnidarians, modern cnidarians exhibit stable tetraradial symmetry in medusozoans, biradial symmetry in anthozoans, and bilateral symmetry in siphonophores (Hydrozoa). The current study supports the view that the tetraradial symmetry of modern medusozoans is a surviving remnant of their Fortunian relatives.     

Conodont biostratigraphy and carbon isotope chemostratigraphy of the Middle to Upper Ordovician on the western Yangtze Platform,South China

Middle and Late Ordovician strata in the nearshore area of the western Yangtze Platform are investigated. In total, 241 δ¹³C_carb samples and 108 conodont samples from the Songliang and Tuanjie sections in the northeastern Yunnan Province were collected for chemostratigraphic and biostratigraphic studies. Altogether, 21 species belonging to 16 conodont genera were recovered from the two sections, among which Ansella jemtlandica, Drepanoistodus basiovalis, Hamarodus brevirameus, and Microzarkodina hagetiana are important age indicators within the Dapingian to early Katian interval. Four carbon isotope shifts are recognized in the studied sections: a negative shift in the early Darriwilian, the middle Darriwilian carbon isotope excursion (MDICE), the early Katian Guttenberg carbon isotope excursion (GICE), and a further positive carbon isotope shift later in the early Katian which is a new record of this event in South China. Integrated carbon chemostratigraphy and conodont biostratigraphy indicate early Darriwilian and early Katian ages for the base and top, respectively, of the Huadan Formation at the Songliang section, and a Darriwilian to early Katian age for the Shihtzupu Formation at the Tuanjie section.     

Carbon,nitrogen and phosphorus ecological stoichiometry of Lateolabrax macultus and Acanthogobius ommaturus in the Estuary of Yangtze River,China

Most stoichiometric models do not consider the importance of ontogenetic changes in body nutrient composition. Among aquatic animals, body elemental ontogenetic changes may be particularly important in fish due to bone formation at larval–juvenile development stage. We investigated the stoichiometric characteristics and ontogenetic variation of carbon (C), nitrogen (N), phosphorous (P) and calcium (Ca) in the whole fish without gut of Lateolabrax macultus and Acanthogobius ommaturus from the Yangtze Estuary. Some differences were found in the whole-fish nutrient content across species as well as fish length and mass groups. Mean body content of L. macultus was 41.2% for C (34.9–44.9%), 11.8% for N (10.3–12.9%), and 3.3% for P (1.4–5.4%) and the molar ratio of C:N:P was 32:8:1. A. ommaturus had the following mean compositions: carbon, 43.4% (40.0–45.9%); nitrogen, 13.2% (11.7–14.1%); phosphorus, 2.9% (1.6–6.0%) and molar ratio of C:N:P was 38:10:1. The variation of C content in of L. macultus was minimum (0.05), followed by N (0.06), and the variation of P content was the highest (0.22). The variation of C content in A. ommaturus was minimum (0.03), followed by N (0.04), and the variation of P content was also the highest (0.27). Both species varied the least in C, moderate in N and the most in P. Comparing the two species, A. ommaturus was significantly higher for C, N, C:P, N:P and significantly lower for P and C:N than L. macultus. The positive correlation between C and N contents was significant (P < 0.01) for both species. In contrast, C and P concentrations showed little correlation (P > 0.05). The contents of C, N in L. macultus showed significant negative correlation with total length and wet mass, respectively, while C:N ratio showed significant positive correlation with them. As for A. ommaturus, the content of C and the ratio of C:N showed significant negative correlation with total length and wet mass, respectively. The two estuarine fishes in this study mainly consumed fish, shrimps and crabs, which could be the reason that the stoichiometry of L. macultus and A. ommaturus are higher than other freshwater fishes that have been reported previously. In both species, the content of calcium was highly correlated with the content of body P, which indicated that the change of the content of P is associated with bone formation in ontogeny. Fish shape, scale type, the ratio of head length/standard length and the degree of ossification of the internal skeleton and outer integument might have caused the results that L. macultus had higher contents of P and Ca than A. ommaturus.     

Impact of long-term nitrogen addition on carbon stocks in trees and soils in northern Europe

The aim of this study was to quantify the effects of fertiliser N on C stocks in trees (stems, stumps, branches, needles, and coarse roots) and soils (organic layer +0–10 cm mineral soil) by analysing data from 15 long-term (14–30 years) experiments in Picea abies and Pinus sylvestris stands in Sweden and Finland. Low application rates (30–50 kg N ha⁻¹ year⁻¹) were always more efficient per unit of N than high application rates (50–200 kg N ha⁻¹ year⁻¹). Addition of a cumulative amount of N of 600–1800 kg N ha⁻¹ resulted in a mean increase in tree and soil C stock of 25 and 11 kg (C sequestered) kg⁻¹ (N added) (“N-use efficiency”), respectively. The corresponding estimates for NPK addition were 38 and 11 kg (C) kg⁻¹ (N). N-use efficiency for C sequestration in trees strongly depended on soil N status and increased from close to zero at C/N 25 in the humus layer up to 40 kg (C) kg⁻¹ (N) at C/N 35 and decreased again to about 20 kg (C) kg⁻¹ (N) at C/N 50 when N only was added. In contrast, addition of NPK resulted in high (40–50 kg (C) kg⁻¹ (N)) N-use efficiency also at N-rich (C/N 25) sites. The great difference in N-use efficiency between addition of NPK and N at N-rich sites reflects a limitation of P and K for tree growth at these sites. N-use efficiency for soil organic carbon (SOC) sequestration was, on average, 3–4 times lower than for tree C sequestration. However, SOC sequestration was about twice as high at P. abies as at P. sylvestris sites and averaged 13 and 7 kg (C) kg⁻¹ (N), respectively. The strong relation between N-use efficiency and humus C/N ratio was used to evaluate the impact of N deposition on C sequestration. The data imply that the 10 kg N ha⁻¹ year⁻¹ higher deposition in southern Sweden than in northern Sweden for a whole century should have resulted in 2.0 ± 1.0 (95% confidence interval) kg m⁻² more tree C and 1.3 ± 0.5 kg m⁻² more SOC at P. abies sites in the south than in the north for a 100-year period. These estimates are consistent with differences between south and north in tree C and SOC found by other studies, and 70–80% of the difference in SOC can be explained by different N deposition.     

湖南会同5个亚热带树种的细根构型及功能特征分析

细根(直径2mm)具有复杂的分枝系统,不同树种间的细根在空间分布、形态和大小上有较大差异,研究不同树种的细根构型及不同根序的养分特征,对认识不同树种的细根形态和化学成分的变异格局,及其对树种地下生态位分离(niche segregation)、共存和森林生态系统功能过程的影响有着重要意义。在湖南会同林区选择青冈(Cyclobalanopsis glauca)、枫香(Liquidanbar formosana)、拟赤杨(Alniphyllum fortunei)、杉木(Cunninghamia lanceolata)、马尾松(Pinus massoniana)等5个亚热带树种,用挖掘法采集完整的细根根系,按照Pregitzer细根分级方法对细根分级,用Win-RHIZO根系测定系统对细根构型的参数进行测定,同时测定各级根系的C、N含量,以探讨各树种各级细根的功能特征,揭示不同树种细根构型与养分策略之间的关系。结果表明:5个亚热带树种细根1级根比根长、比表面积最高,直径最细;3级根比根长、比表面积最低,直径最粗。不同树种之间细根形态特征和构型也表现出差异性:枫香的1级根序比根长最大,为31.45m·g-1,杉木的最小,为16.34m·g-1,枫香和杉木之间差异显著。马尾松的1、2级根序的比表面积最大,杉木的1级根序的比表面积最小,青冈2级根序的比表面积最小,3级根序比表面积杉木最大,青冈最小。不同树种之间的细根直径差异达到极显著水平,各根序的平均直径以杉木的最大,拟赤杨的最小。5个树种细根根尖密度大小顺序为马尾松青冈枫香杉木拟赤杨,各树种细根分叉数以拟赤杨和马尾松的较高,杉木最低。除杉木和枫香外,5个树种细根C含量均呈现出随着根序上升而增加的趋势,C/N比也随根序的上升而增加,而细根N含量呈现出随着根序上升而明显下降的趋势。细根平均C含量以杉木的最高,拟赤杨的最低,马尾松、青冈与枫香之间的差异不显著。细根平均N含量以拟赤杨的最高,马尾松的最低。C/N比以马尾松的最高,拟赤杨的最低。5个树种中,马尾松的外生菌根有很强的拓展能力,因此能显著地增强植物根系的养分、水分吸收能力,即使在贫瘠和干旱的土壤环境中,也能有效地利用有限的养分和水分,促进个体生长。而杉木细根吸收养分和水分的效率及能力最小。     

扬子台地西北缘志留纪笔石Oktavites spiralis (Geinitz, 1842)发育过程研究

Oktavites spiralis(Geinitz,1842)是志留系特列奇阶(Telychian)的笔石带化石,其形态特征明显,在全球范围内广泛分布,地层对比意义较强。然而,该种宽泛的化石定义以及缺乏居群变异研究,造成了对该化石延限的争议,不利于地层的精确对比。笔者对产自陕西紫阳、岚皋地区特列奇阶Oktavites spiralis带至Cyrtograptus lapworthi笔石带的45个Oktavites spiralis不同发育阶段的幼体标本进行研究,建立了较完整的发育序列,从而对该种的始部特征有了更为深入的了解,增加了描述的精确性。同时,通过始部特征的对比研究,可将Oktavites spiralis和与之共生的Oktavites contortus(Perner,1897)明确区分为2个独立的种。此外,对Oktavites spiralis和Oktavites contortus发育过程的研究,也可成为该属进一步精确厘定的主要依据之一。     

A nearshore–offshore trend in acritarch distribution from the Early–Middle Ordovician of the Yangtze Platform, South China

The stratigraphical interval of the late Early Ordovician Didymograptus deflexus and the early Middle Ordovician Azygograptus suecicus graptolite Biozones was investigated from seven sections from the upper Yangtze Platform, southern China. These are located on different parts of the platform, between the nearshore environments of the Kunming area, Yunnan Province, and the offshore carbonate shelf of the Yichang area, Hubei Province. The assemblages recovered from the different parts of the platform vary both in terms of diversity and composition. The nearshore environments show low diversity assemblages with about 10 acritarch species, whereas the offshore shelf environments reflect higher diversities with about 40 species. The composition of the assemblages also changes from simple morphologies (micrhystrids, leiosphaerids, fusiform acritarchs) in nearshore environments to specimens with longer and more complexly branched processes on the shelf. The polygonomorph acritarchs are common over all the upper Yantze Platform, while the acanthomorph genera Baltisphaeridium and Peteinosphaeridium are the most abundant taxa on the offshore carbonate shelf area. Phylogenetic or sea-level changes are probably not responsible for the compositional and diversity changes that occurred during the investigated interval. This study confirms previous interpretations that poorly diversified Palaeozoic acritarch assemblages occur in neritic environments and more complex, highly diversified assemblages are found on the shelf.     

臭氧胁迫对水稻生长以及C、N、S元素分配的影响

采用开顶式气室(Open-top Chamber, OTC),对水稻"3694繁"(Oryza sativa L., 3694 Fan)在浙江嘉兴进行田间原位臭氧(O₃)熏气实验,研究不同臭氧浓度熏气对水稻生长以及C、N,S元素分配的影响。实验设置分4个水平:过滤大气组(CF,10 nL/L)、自然大气组(NF,40 nL/L)和两个不同浓度的臭氧处理组(O₃-1:100 nL/L; O₃-2:150 nL/L)。主要结果表明:(1)开始臭氧熏气时,各个处理组单茎水稻各组分生物量没有差异. 在熏气后期(水稻成熟期),臭氧处理使单茎水稻根、茎和穗生物量显著下降,根冠比降低,株高显著降低,表明臭氧胁迫增加水稻地上部分的干物质分配,且对株高的影响可能大于对地上生物量的影响;(2)臭氧处理使水稻根和茎C元素含量下降,叶C元素含量上升,表明臭氧胁迫提高了叶片中碳分配,而降低了根和茎的碳分配;(3)各个组分N元素含量上升和碳氮比下降;(4)茎、叶和穗S元素含量上升,可能会增强水稻抗氧化系统的作用,从而抵抗臭氧胁迫。所有实验结果表明臭氧浓度升高会对水稻生长产生严重不利影响,从而导致水稻各个组分的C、N、S元素分配格局发生改变。     

Impact of Anthropogenic Organic Matter on the Distribution Patterns of Sediment Microbial Community from the Yangtze River,China

Abstract

How microbes respond to substantial and increasing anthropogenic disturbance remains an open question in river systems. We tested the hypothesis that the source and distribution of anthropogenic organic matter (OM) were significant factors affecting the spatial variation of the microbial community composition of the Yangtze River sediments. Bulk geochemical proxies and lignin phenols suggested a general decrease of terrestrial C3 plants or soil OM input from the middle to the lower reaches. Fecal sterols inferred higher sewage contamination levels in the middle reaches. Polycyclic aromatic hydrocarbons (PAHs) distribution indicated a dominant biomass and coal combustion signal in the middle reaches, whereas a mixed source including petroleum combustion in the lower reaches. Phylogenetic analysis revealed a large portion of Methanobacteria and Verrucomicrobia enriched in the middle reaches, whereas OM-degrading bacteria, including Flavobacteria, Acidobacteria, and Alphaproteobacteria were dominant in the lower reaches. Quantitative PCR analyses and multivariate analysis further demonstrated that sources and distribution of OM had combined effects in shaping alpha and beta-diversity of sediment microbial communities. Sewage discharge and incomplete OM combustion, respectively, were associated with Methylococcaceae, Chloroflexi, and Bacteroidetes groups. This study provides a foundation for further understanding of the river sediment microbial composition, considering the continued increase of anthropogenic influences.     

放牧强度对华北农牧交错带典型草地土壤化学计量特征的短期影响

放牧是天然草地的主要利用方式之一,不同放牧强度可能通过影响家畜的选择性采食、凋落物输入和微生物的组成及结构等影响草地土壤化学计量特征.本研究通过在华北农牧交错带典型草地一个连续3年(2017-2019年)的生长季放牧试验,测定了土壤全碳(TC)、全氮(TN)、可溶性有机碳(DOC)和可溶性氮(DN)含量,以及土壤微生物...     

Effects of medium carbon-to-nitrogen ratio on biofilm formation and plasmid stability

Biofilm formation and plasmid segregational instability in biofilm cultures of Escherichia coli DH5alpha (pMJR1750) were investigated under different medium-carbon-to-nitrogen (C/N) ratios. At C/N ratios of 0.07 and 1, net accumulation of both biofilm plasmid-bearing and plasmid-free cells continued through the entire experiment without attaining any apparent steady state. At C/N ratios of 5 and 10, net biofilm cell accumulation for the two populations reached apparent steady states after 84 and 72 h, respectively. At C/N ratios of 0.07 and 1, polysaccharide production increased slowly and reached about 2g alginate equivalent/cm(2) by the end of both experiments. At a C/N ratio of 5, polysaccharide increase significantly after 84 h, reaching about 7mug alginate equivalent/cm(2) prior to termination. At a C/N ratio of 10, polysaccharide increased significantly after 72 h and reached 21 mug alginate equivalent/cm(2) at 108 h. At C/N ratios of 0.07 and 1, protein production reached 6.5 and 4 mug/cm(2), respectively. At C/N ratios of 5 and 10, protein production increased slightly for the first 84 h and reached a maximum at 108 h, at 3 and 2 mug/cm(2), respectively, then decreased over the last 12 h of the experiment. Ratios of polysaccharide to protein increased with increasing C/N ratios. At C/N ratios of 0.07 and 1, the ratios between extracellular polysaccharide (EP) and protein were no more than 205 mug polysaccharide/mug protein, whereas those at C/N ratios of 5 and 10 increased to about 7 and 12 mug polysaccharide/mug protein, respectively.Probabilities of plasmid loss in the biofilm cultures increased with increasing C/N ratios. At C/N ratios of 0.07, 1, and 5, the probabilities of plasmid loss were 0.0013 +/- 0.011, 0.020 +/- 0.006 and 0.122 +/- 0.021, respectively. At a C/N ratio of 10, the probability of plasmid loss was significantly higher, reaching 0.38 +/- 0.125. The increase of probability of plasmid loss at higher C/N ratios results from competition between cell replication and extracellular polysaccharide production. (c) 1994 John Wiley & Sons, Inc.     

太湖五里湖富营养化的碳同位素记录

通过太湖五里湖表层沉积物柱样中总有机碳、总氮、总磷的变化,探讨了五里湖营养盐磷输入的历史记录,结合总有机碳碳同位素的分析,揭示了该湖富营养化和初级生产力的演化过程.总有机碳碳同位素值为-27.0‰～-26.3‰,平均-26,6‰,从底部向上波动变化,在深度12 cm处最大,然后向上逐渐减小,5 cm处降至最小,随之向上逐渐增大,反映了随着人为活动强度的加大,该湖水体富营养化程度逐渐加剧的特点,并且总有机碳碳同位素与有机碳、氮原子比值记录了湖泊水生植物群落由水草为主-草藻结合-藻类为主的演替过程.

Abstract：

Through the analysis of total organic carbon, total nitrogen, and total phosphorus con-centrations in surface sediment cores from Wuli Bay of Taihu Lake, the historical record of phos-phate input in the Bay was studied, and in combining with the analysis of carbon isotope value of bulk sedimentary organic matter, the evolution process of the primary productivity and eutrophi-cation in the Bay was revealed. The carbon isotope value of the sediment total organic C was -26. 6‰ on average, with a variation between-27.0‰ and-26. 3‰. It was decreased with depth up to the lowest value at 5 cm, subsequently increased gradually up to the highest value at 12 cm, and then fluctuated downward with the depth, which suggested that the evolvement of eu-trophication, productivity, and primary producer was associated with the increasing phosphorus input from human activities. Moreover, the concentrations of total phosphorus and the C/N atom-ic ratios of total organic carbon to total nitrogen recorded the succession process of aquatic plant community from float grass to float grass + algae to algae.     

Inverse relationship between carotenoid and lipid formation in Rhodotorula gracilis according to the C/N ratio of the growth medium

Production of carotenoid by Rhodotorula gracilis was highest at 26 mg/g dry weight with a carbon/nitrogen (C/N) ratio in the medium of 10:1. This was 15 times higher than when the C/N ratio was 160:1. With this high C/N ratio, the yeast produced up to 55% lipid compared only 20% lipid with the low C/N ratio. Both carotenoid and lipid production were non-growth associated.     

基质碳氮比对广叶绣球菌生长发育的影响

培养基质碳氮比显著影响食用菌菌丝生长及子实体生长发育.广叶绣球菌是一种珍贵的食药用真菌,前期研究发现其生长发育过程中对碳源的需求较多.本研究采用松木屑、复合氮源作为栽培原料,研究基质碳氮比对绣球菌菌丝生长及子实体生长发育的影响.结果 表明:6种不同碳氮比(C/N)的栽培基质对菌丝生长速度无显著影响,但是随着C/N比值的...     

碳氮比和光强对小球藻合成虾青素的影响

本文研究了碳氮比和光强对小球藻Chlorella zofingiensis合成虾青素的影响。结果表明,随着碳氮比的增加,虾青素含量提高,但是过高的碳氮比限制藻细胞的生长,当碳氮比为133时,虾青素的产量最大,达到9.19mg／L。高光诱导在高碳氮比基础上进一步提高虾青素的含量及产量。200μmol／m^2.S光强在没有严重影响小球藻生长的同时,明显提高虾青素含量,最大虾青素产量达到12.52mg／L。文章对不同诱导条件下虾青素的合成机理以及利用异养自养相结合的方法提高虾青素产量的可能性进行了讨论。     

碳氮比和光强对小球藻合成虾青素的影响

本文研究了碳氮比和光强对小球藻Chlorella zofingiensis合成虾青素的影响。结果表明, 随着碳氮比的增加, 虾青素含量提高, 但是过高的碳氮比限制藻细胞的生长。当碳氮比为 133 时, 虾青素的产量最大, 达到 9.19 mg/L。高光诱导在高碳氮比基础上进一步提高虾青素的含量及产量。200 mmol/m2﹒s 光强在没有严重影响小球藻生长的同时, 明显提高虾青素含量, 最大虾青素产量达到 12.52 mg/L。文章对不同诱导条件下虾青素的合成机理以及利用异养自养相结合的方法提高虾青素产量的可能性进行了讨论。     

白江河泥炭地泥炭藓孢子萌发力对排水的响应

排水严重改变泥炭地的环境和生态过程,但对泥炭藓孢子萌发力的影响尚不清楚。在长白山地区白江河泥炭地,分别在优势植物为苔藓的近原始地段和优势植物为小灌木的排水地段,钻取泥炭柱芯为试验材料,逐层测试泥炭理化指标,提取泥炭藓孢子并进行萌发试验,统计孢子数量和萌发力;经过泥炭样品年代测定,建立深度年代关系曲线,研究泥炭藓孢子萌发力对排水的响应和机制。结果表明: 整个柱芯对比,近原始地段平均孢子数略高于排水地段,两地段的平均孢子萌发力无差异,排水地段的泥炭容重、总碳和总氮都显著高于近原始地段。柱芯上部对比,排水(1987年)以后两地段孢子累积速率无显著差异,但近原始地段的平均孢子萌发力(34%)远低于排水地段(72%)。近原始地段的碳氮比与孢子萌发力呈显著正相关;排水地段的总碳、pH和埋藏时间与孢子萌发力呈显著负相关。30年前的泥炭地排水虽对孢子累积影响不大,但通过加速分解而改变了泥炭的理化性质,提升了表层泥炭中孢子萌发力,因此降低孢子库的持久性,可能导致泥炭藓在灾变性干扰后的种群持续更新潜力下降。     

碳源种类及碳氮比对眼点拟微绿球藻生长密度、油脂含量和脂肪酸组成的影响

研究了三种碳源Na2CO3、NaHCO3、葡萄糖对眼点拟微绿球藻生长密度和油旨含量的影响,实验结果表明相对于葡萄糖,无机碳源NaHCO3更利于眼点拟微绿球藻的生长.以NaHCO3为碳源,研究了在不同的接种密度、NaNO3浓度下,C/N对眼点拟微绿球藻生长密度和油脂含量的影响.实验结果表明,C/N对眼点拟微绿球藻生长密度的影响与接种密度和NaNO3浓度有关,在高的NaNO3浓度时,C/N对眼点拟微绿球藻生长密度的影响很小;在低的NaNO3浓度时,随着C/N比的增加,微绿球藻的生长密度先增加后下降,存在最佳的C/N比.最佳的C/N比随接种密度而变化,在接种密度为OD440=0.10时,最佳C/N比为3,当接种密度提高到OD440=0.70时,最佳C/N比增加到5.NaNO3浓度和C/N对微藻油脂含量均有较大影响,在不同的接种密度和NaNO3浓度下都表现为C/N=1时最利于微藻油脂的积累,这与卡尔文循环过程中核酮糖-1,5-二磷酸羧化酶/加氧酶的活性有关.本实验的最佳产油培养条件为以NaHCO3为碳源,初始接种密度为OD440=0.70,C/N=1∶1,CNaNO3=0.225g/L,此时油脂产率为56.7 mg/(L·d),EPA产率为6.5 mg/(L·d).