Effects of nutrient limitations on the sinking velocity of Thalassiosira weissflogii

The sinking of diatoms is critic al to the formation of oceanic biological pumps and coastal hypoxic zones.However,little is known about the effects of different nutrient restrictions on diatom sinking.In this study,we measured the sinking velocity(SV) of Thalassiosira weissflogii using a new phytoplankton video observation instrument and analyzed major biochemical components under varying nutrient conditions.Our results showed that the SV of T.weissflogii under different nutrient limitation conditions varied substantially.The highest SV of(1.77±0.02) m/d was obtained under nitrate limitation,signific antly surpassing that under phosphate limitation at(0.98±0.13) m/d.As the nutrient limitation was released,the SV steadily decreased to(0.32±0.03) m/d and(0.15±0.05) m/d,respectively.Notably;under conditions with limited nitrate and phosphate concentrations,the SV values of T.weissflogii significantly positively correlated with the lipid content(P <0.001),with R^(2) values of 0.86 and 0.69,respectively.The change of the phytoplankton SV was primarily related to the intracellular compo sition,which is controlled by nutrient conditions but did not significantly correlate with transparent extracellular polymer and biosilica contents.The results of this study help to understand the regulation of the vertical sinking process of diatoms by nutrient restriction and provide new insights into phytoplankton dynamics and their relationship with the marine nutrient structure.

营养盐亏缺与恢复对威氏海链藻(Thalassiosira weissflogii)生长和生化组成的影响

通过室内纯培养,研究了营养盐亏缺以及解除亏缺对威氏海链藻(Thalassiosira weissflogii)的细胞形态、细胞增殖、胞内蛋白质、可溶性糖含量变化的影响,考察了藻细胞生长和生化组成的恢复情况。结果表明,在多种营养盐亏缺(N亏缺、P亏缺、Si亏缺、N+P亏缺、贫营养)的条件下,威氏海链藻生长受到不同程度的抑制,全部受试细胞形态均出现不同程度变异,细胞增殖显著低于正常营养供给。恢复营养,细胞形态的损伤能得以有效恢复,细胞增殖能力得以一定程度的有限恢复,其中氮、磷亏缺的恢复效应最为明显。营养盐亏缺,各处理组细胞生化组成显著低于正常培养状态。恢复营养,氮、磷亏缺组藻细胞生化组成仍显著低于正常营养供给,生化组成的恢复效应不明显,生理活性无法恢复,而硅盐亏缺的藻细胞生长和生化组成均能恢复到正常水平。实验证明,微藻细胞的生化组成比形态变化与增殖更能反映营养盐亏缺,可作为微藻受氮、磷营养盐限制的指标。

磷酸盐和硝酸盐浓度对海链藻Thalassiosira sp.沉降的影响

为了研究氮、磷营养盐比例变化对近海硅藻的生理效应及其对硅藻相关碳汇的影响,分别采用半连续培养和一次性培养的方式对海链藻(Thalassiosirasp.)在不同氮磷比及不同氮、磷营养盐浓度的条件下进行模拟培养实验。结果表明:在半连续培养中,营养盐限制明显降低海链藻的胞内叶绿素含量及蛋白质含量,增加了胞内生物硅含量和碳水化合物含量,藻细胞密度变大增加沉降速率;在一次性培养中,指数生长期的沉降速率最低,随着细胞生长逐步到达衰退期,沉降速率随之升高,而在最低营养盐浓度条件下最高。海链藻的沉降速率在低氮磷比的条件下显著升高。因此,近海氮、磷营养元素结构的变化也会对浮游植物相关的碳沉降产生重要影响,在富营养化的生态效应研究中不容忽视。

温度、盐度及光照强度对海链藻(Thalassiosira sp.)生长的影响

报道了温度、盐度、光照对海洋硅藻海链藻生长的影响。结果表明 ,海链藻的适应温度范围比较广 ,从9～27℃都可维持正常生长 ,15～21℃为其适温范围 ;在盐度15～35范围内 ,盐度对海链藻的影响不大 ,在盐度为20时 ,海链藻获得最大的生长率;此外 ,海链藻具有广泛的光适应性 ,在7.5～90μmol/(m2·s)的光照范围内均可正常生长。

双环海链藻(Thalassiosira diporocyclus Hasle)赤潮

20 0 1— 2 0 0 2年的秋冬季节 ,于中国东南沿海的南澳岛周围海域突发了双环海链藻赤潮 ,该赤潮藻及其赤潮在中国都是首次记录。该赤潮藻以实心胶质块的群体形式出现 ,其群体一般呈球形或椭球形 ,常为茶褐色 ,大小不一 ,直径多数在 2— 3mm之间 ,最小的不到 0 1mm ,最大的约有 5mm。胶质块由双环海链藻和数种羽纹硅藻组成 ,前者分布于外层 ,后者包埋其中。双环海链藻的细胞密度最大达 1 75× 10 7cells/L ,占浮游植物总细胞数的 78 8%。如把包埋其中的羽纹硅藻考虑进去 ,赤潮藻胶质块的组成细胞总密度则高达 2 2 8× 10 7cells/L以上 ,占浮游植物总细胞数的 95 9%。赤潮藻的密度由湾内向外海呈显著递减趋势 ,与营养盐的平面分布格局相反。该赤潮起源于外海 ,赤潮发生机制可能与 2 0 0 1— 2 0 0 2厄尔尼诺年导致的水温异常升高有关。

First record of Thalassiosira curviseriata Takano (Bacillariophyta) and its bloom in the East China Sea

A bloom caused by a diatom, Thalassiosira curviseriata Takano （Bacillariophyta） , is recorded in the East China Sea for the first time in China during a red tide investigation cruise （MC2005 -2） from 27 March to 12 April 2005. This bloom was developed with the competition of Chaetoceros debilis and Skeletonema spp. The highest cell density of T. curviseriata, which has reached 1.27 × 10^6 cells/dm3, was found in the surface and middle water layers of Stas ZD, ZB in the East China Sea （27. 22°-29.48°N, 121.53° - 122. 98°E）in early spring in 2005. During the blooming period of T. curviseriata, the population with high cell density was found in the water area with temperature of 10 -15 ℃ and salinity of 29.0 - 33.5. The percentage of the predominant species, T. curviseriata, has reached 95.8% of total diatom cells at one time in the middle water layer. The morphological characteristics of T. curviseriata, were observed with light microscope （LM） and transmission electronic microscope （TEM）. The cells are 5.0 - 12. 6 μm in diameter, connecting each other by mucilaginous thread to form spiral and curved chains. Description and LM and TEM images of T. curviseriata are presented. T. curviseriata is ecologically characterized by eurythermy and euryhalinity, and its population variation is affected mainly by silicate, the ratios of phosphorus to silicon and nitrogen to silicon.

Development of a real-time PCR method for Thalassiosira rotula rapid detection

Gene specific primers and DNA probe were designed based on the sequence of 18S rDNA cloned from the red tide alga Thalassiosira rotula. A real-time fluorescent quantitative PCR （RFQ - PCR） method was developed for quantitative detection of T. rotula. The RFQ - PCR assay data showed that the results obtained with the RFQ - PCR quite good agreement with those with the light microscope （LM） counting method, which suggested that the RFQ - PCR could be a useful method for red tide alga detection.

海链藻(Thalassiosira sp.)对氮磷需求量的研究

初步研究了海链藻对氮磷的需求 ,使用光密度法测定了微藻的细胞数。结果表明 :以等物质的量氮的 NH4Cl,Na NO3 和 NH4NO3 作为氮源时 ,选择 NH4NO3 可以获得较快的生长率并维持较长时间的指数生长期 ;氮浓度的最适范围为 0 .5 4～ 1 .0 8mmol/L,而 2 .1 6mmol/L以上的高浓度NH4NO3 则对海链藻的生长有一定的抑制作用 ;磷浓度在 0 .0 1 5～ 0 .1 2 mmol/L时 ,海链藻保持大致相同的生长速率 ,最适为 0 .0 3～ 0 .0

海链藻(Thalassiosira)与圆筛藻(Coscinodiscus)的形态学比较研究

海链藻属(Thalassiosira)和圆筛藻属(Coscinodiscus)的种类繁多,是硅藻门中的大属和代表属。两者的形态学特征具有较多相似之处,易混淆鉴定。通过光学显微镜和电镜观察,比较研究了海链藻和圆筛藻种类的形态学特征。海链藻种类除了具有1～2个唇形突之外,还具有数量较多的支持突,少数种类具有闭合突;筛膜位于壳面内侧;中孔在壳面外侧。而圆筛藻种类只具有数量众多的唇形突,且其中两个较大;筛膜位于壳面外侧;中孔在壳面内侧。由于两属形态学特征的区别只有在电镜下才能清晰观察到,因此尚有较多的分类修订工作需要进行。

Phosphorus deficiency affects multiple macromolecular biosynthesis pathways of Thalassiosira weissflogii

Phosphorus（P） is one of the key nutrients for the growth of phytoplankton. In this study, we used a method coupling label-free quantitation with liquid chromatography–mass spectrometry（LFQ–LC–MS/MS） to track the change of relative protein abundance between P-replete and P-deficient treatments in a non-model diatom, Thalassiosira weissflogii. Out of the 631 proteins identified, 132 were found to have significant changes in abundance（〉1.5 folds） between the two treatments, especially those proteins involved in macromolecular biosynthesis pathways. For example, the up-regulation of sulfolipid biosynthesis protein in the P-deficient culture suggested a switch from using phospholipids to sulfolipids. In addition, the ribosome subunits and tRNA synthetases were down-regulated, which might explain the decrease in protein content in the P-deficient culture. A vacuolar sorting receptor homologous protein was found to be 9.2-folds up-regulated under P-deficiency, indicating an enhancement in the vacuolar sorting pathway for protein degradation. Our results show that T. weissflogii has sophisticated responses in multiple macromolecular metabolism pathways under P-deficiency, a mechanism which can be critical for this species to survive under various levels of P availability in the environment

Preparation and characteristics of biosilica derived from marine diatom biomass of Nitzschia closterium and Thalassiosira

In this study, biosilica of high purity was successfully prepared from marine diatom （Nitzschia closterium and Thalassiosira） biomass using an optimized novel method with acid washing treatment followed by thermal treatment of the biomass. The optimal condition of the method was 2% diluted HCl washing and baking at 600℃. The SiO2 contents of N. closterium biosilica and Thalassiosira biosilica were 92.23% and 91.52%, respectively, which were both higher than that of diatomite biosilica. The SiO2 morphologies of both biosilica are typical amorphous silica. Besides, IV. closterium biosilica possessed micropores and fibers with a surface area of 59.81 m^2/g. And Thalassiosira biosilica possessed a mesoporous hierarchical skeleton with a surface area of 9.91 m^2/g. The results suggest that the biosilica samples obtained in this study present highly porous structures. The prepared porous biosilica material possesses great potential to be used as drug delivery carrier, biosensor, biocatalyst as well as adsorbent in the future.

Nutrient compositions of cultured Skeletonema costatum,Chaetoceros curvisetus,and Thalassiosira nordenskildii

We cultured different-sized fractions of dominant phytoplankton species, Skeletonema costatum, Chaetoceros curvisetus, and Thalassiosira nordenskioldii, collected in different sea areas in various seasons, and measured and compared their C, N, P, Si contents. The N content of these species is similar, while the C, P, and Si contents of S. costatum from eutrophic Changjiang （Yangtze River） estuary are higher than those from Jiaozhou Bay （JZB）, particularly the content of Si. The C, N, P, and Si contents of cultured phytoplankton in JZB increase with size fraction augmentation, and the percentages of C, N, and P follow the same trend, while the percentage of Si remain constant. Moreover, S. costatum from small-sized fraction assimilated Si more easily than C. curvisetus and T. nordenskirldii, which is explained by the dominance of S. costatum under the conditions of low SiO3-Si concentration in JZB. The C, N, P, and Si contents of cultured S. costatum collected during summer and winter are higher, which is consistent with the phytoplankton blooming seasons in JZB. The SiO3-Si concentration of seawater during spring restrain the growth of phytoplankton, supported by the fact that the N, P, and Si contents and their ratios in cells of cultured S. costatum are low in spring season.

Effect of Temperature on the Release of Transparent Exopolymer Particles(TEP)and Aggregation by Marine Diatoms(Thalassiosira weissflogii and Skeletonema marinoi)

The presence of diatoms is accompanied by the production of a large amount of extracellular polymeric substances,which are mainly composed of carbohydrates.Transparent exopolymer particles(TEP)are a large class of extracellular polymeric substances with high stickiness that promotes the formation of aggregates and marine snow,which affects marine bio-carbon pump efficiency.The purpose of this research was to determine how temperature increases affect the allocation of cellular carbohydrates and the formation and aggregation of TEP.The results showed that the responses of two different diatom species(Thalassiosira weissflogii and Skeletonema marinoi)differed according to temperature.The cell density and chlorophyll a concentration of the former were not significantly correlated with temperature,while those of the latter were significantly decreased with increasing temperature.This indicates that the two species of diatom may have different heat tolerance ranges.A temperature increase will promote significant formation of TEP by both types of diatoms,including aggregation of S.marinoi as the temperature rises,meaning that the high temperature will produce an aggregate with a larger particle size and thus may increase the sedimentation rate of organic carbon.Moreover,the TEP aggregation of T.weissflogii did not increase;therefore,its particle size was smaller,and so it may remain on the sea surface at high temperatures for longer periods.These influences have a profound impact on the biogeochemical cycling of carbon.

应用双特异分子探针技术定性定量检测圆海链藻(Thalassiosira rotula)

设计了一套圆海链藻(Thalassiosira rotula)特异性探针,运用双特异分子探针技术,对圆海链藻(Thalassiosira rotula)进行了定性定量检测。结果表明,本实验中设计的一套探针与其它十几种藻无交叉反应,具有种特异性;细胞裂解液直接杂交检测优于提纯RNA样品检测;对自然样品做了初步检测,发现天然海水中的其它浮游生物对该检测方法影响很小。

The study of fluorescence characteristics and biochemical composition of a marine diatom Thalassiosira pseudonana 3H in light and dark cyclesI. The effects of nutrients

The effects of nutrients on the fluorescence characteristics and biochemical composition of marine diatom Thalassiosira pseudonana 3H in light and dark cycles were investigated with continuous culture. The results show that with the increase of nutrient deficiency, the ratio of enhanced fluorescence to fluorescence (Fd/F), cellular chloropyll-a and protein content of the algae decline, but the fluorescence yield (F/Chl) , DCMU enhanced fluorescence yield (Fd/Chl) , cellular carbohydrate content, carbohydrate/Chl, protein/Chl, carbohydrate/protein increase. The changing amplitude of each parameter is different at different nutrition status, sampling time and different light intensity.

海洋浮游硅藻Thalassiosira rotula细胞质膜电子转换与DIC浓度的关系

海洋浮游硅藻Ｔｈａｌａｓｉｏｓｉｒａｒｏｔｕｌａ细胞质膜存在电子转换，可还原外源电子受体Ｆｅ（ＣＮ）３－６．介质中溶解无机碳（ＤＩＣ）浓度的降低。

三苯基锡对假微型海链藻(Thalassiosira pseudonana)的生长抑制及温度的影响

在我国近岸海域环境中,三苯基锡分布十分广泛。本研究以假微型海链藻(Thalassiosira pseudonana)为目标物种,研究了4个不同温度条件下(10℃、15℃、25℃与30℃)三苯基锡暴露对其细胞生长以及光合作用参数(Fv/Fm与ФII)的影响。结果表明,假微型海链藻的细胞生长速率在高温与低温条件下均显著下降,而光合作用参数仅在30℃条件下受到显著影响。在暴露温度为10℃、15℃、25℃与30℃时,三苯基锡(triphenyltin,TPT)对假微型海链藻的生长抑制IC50值分别为1.81、1.69、1.09与0.73μg·L-1。TPT对假微型海链藻光合作用抑制的IC50随着温度的升高呈降低趋势。Two-way ANOVA分析结果显示,温度与三苯基锡的相互作用显著影响假微型海链藻的光合作用。上述研究结果可以为了解不同温度下三苯基锡对海洋微藻的毒性效应提供科学依据。

Improving the genome and proteome annotations of the marine model diatom Thalassiosira pseudonana using a proteogenomics strategy

Diatoms are unicellular eukaryotic phytoplankton that account for approximately 20%of global carbon fixation and 40%of marine primary productivity;thus,they are essential for global carbon biogeochemical cycling and climate.The availability of ten diatom genome sequences has facilitated evolutionary,biological and ecological research over the past decade;however,a complimentary map of the diatom proteome with direct measurements of proteins and peptides is still lacking.Here,we present a proteome map of the model marine diatom Thalassiosira pseudonana using high-resolution mass spectrometry combined with a proteogenomic strategy.In-depth proteomic profiling of three different growth phases and three nutrient-deficient samples identified 9526 proteins,accounting for~81%of the predicted protein-coding genes.Proteogenomic analysis identified 1235 novel genes,975 revised genes,104 splice variants and 234 single amino acid variants.Furthermore,our quantitative proteomic analysis experimentally demonstrated that a considerable number of novel genes were differentially translated under different nutrient conditions.These findings substantially improve the genome annotation of T.pseudonana and provide insights into new biological functions of diatoms.This relatively comprehensive diatom proteome catalog will complement available diatom genome and transcriptome data to advance biological and ecological research of marine diatoms.

基于转录组的假微型海链藻硫代谢相关途径分析

为分析近海广布藻华原因种应对广盐环境的细胞关键生命代谢活动过程的调控策略,本研究对不同盐度以及不同处理时间的假微型海链藻(Thalassiosira pseudonana)进行转录组测序,获得T.pseudonana硫代谢途径酶编码基因的差异表达结果。研究结果显示:在不同盐度下,共发现13个硫代谢途径的差异表达基因;随培养时间延长,低盐度培养的实验组相较于对照组有更多的硫代谢编码基因发生显著差异表达,如在硫酸盐同化过程中,在培养的第二天ATP硫酸化酶的基因表达量相对于第一天显著降低,其原因可能是因为藻细胞对硫酸盐同化需求的减少,从而可能会限制亚硫酸盐的形成;在低盐胁迫下,与半胱氨酸合成相关的酶(如丝氨酸乙酰转移酶)基因表达量显著降低,说明藻细胞减少了含硫氨基酸(如半胱氨酸)的合成,这些都会影响其正常的生命代谢活动。本研究表明,沿海河口区的盐度波动可能会对T.pseudonana的硫代谢产生重要影响,这一发现有助于深入理解近海广布藻华原因种应对盐度压力时的分子响应机制。

环境浓度下的纳米塑料对假微型海链藻的影响

为了解环境浓度海洋纳米塑料(Nanoplastics, NPs)对微藻的影响,本研究以两种粒径(0.1和1μm)的聚苯乙烯纳米塑料(Polystyrene nanoplastics, PSNPs)和海洋模式硅藻假微型海链藻(Thalassiosira pseudonana)为研究对象,从种群、光合生理、细胞色素、胞外聚合物(Extracelluar polymeric substances, EPS)和转录水平上比较环境浓度(5μg·L-1)下两种粒径NPs对假微型海链藻的影响。研究结果表明:(1)假微型海链藻经环境浓度下的两种粒径(0.1和1μm)的NPs处理后,前48 h内其生长和细胞色素组成均没有显著变化,但光合生理指标中的非光化学淬灭(Non-photochemical quenching, NPQ)显著上升。(2)假微型海链藻经环境浓度下的NPs处理后,其产生的EPS总量下降,但蛋白/碳水化合物上升,疏水性变强。(3)环境浓度下的NPs能够引起假微型海链藻的基因(LHCX、GPI、ABCt、APX、NRT等)表达的变化,0.1μm NPs胁迫下的差异表达基因比1μm NPs胁迫下的更多,差异表达量更显著。综合分析得到结论:环境浓度下的NPs能够对假微型海链藻产生影响,0.1μm NPs产生的影响更大。