Diatom and Diatomite: Different Focus on Natural Media to Material Science Path

Bio-silica issued from diatom, a microalgae, is attracted increasing attention in material science thanks to its peculiar nanoarchitecture and related properties with versatile applications. The present work is a deep analysis on morphological and chemical properties of bio-silica issued from fossil origin (diatomaceous earth) and living one (algal paste). An optimization in purification protocol was performed to obtain multiparous bio-silica from its raw media with keeping its original shape entirely. Multiple characterization methods as scanning electronic microscopy (SEM), infrared spectroscopy, x-ray diffraction (DRX), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), nitrogen adsorption and inverse gas chromatography (IGC), were used to check the purification protocol efficiency as well as to gather accurate information on morphology and chemical composition of diatom material obtained in large amount.

Lineaperpetua gen.nov.:a new diatom genus in the Thalassiosirales supported by morphology and molecular data

Based on a combination of morphology and molecular data of ribosomal DNA genes,a new diatom genus Lineaperpetua gen.nov.Yu,You,Kociolek&Wang is described.The features that help define Lineaperpetua at the level of genus include:a tangentially undulated valve face;continuous cribra areolae on the valve interior consisting of pores arranged as strips;single rimoportula located inside the ring of marginal fultoportulae.Additionally,phylogenetic analysis based on nuclear small subunit(SSU)rDNA sequences and nuclear large subunit(LSU)rDNA gene placed the three strains of L.lacustris in a single,monophyletic clade at a considerable sequence distance from the other genera(Thalassiosira,Conticribra,Planktoniella,Shinodiscus,and other genera)belonging to Thalassiosirales.Despite the similarities with some species of Thalassiosira,Conticribra,and Spicaticribra,the suite of features found in Lineaperpetua differentiate it from these other genera.These molecular data and morphological characters suggest an affinity of the new genus to the Thalassiosiraceae.

Yuzaoea gen. nov., a new biraphid diatom(Bacillariophyceae)genus and its phylogenetic significance

The flexed frustules in pennate diatoms are usually associated with monoraphid diatoms. Interestingly, we found a biraphid diatom species with flexed frustules in an offshore intertidal beach environment on Weizhou Island,Beihai City, Guangxi Zhuang Autonomous Region, China. Therefore, based on morphological characteristics, we described a new genus of diatoms Yuzaoea sinensis gen. et sp. nov. CH Li, HH Liu, YH Gao & CP Chen. The frustule of this genus is characterized by heterogeneous frustule with one concave valve and one convex valve,complete raphe on both valves, straight and moderately eccentric raphe, uniseriate striae and girdle bands with a single row of areolae. The most identifying feature of this genus was the flexed frustule, which is rare in biraphid diatoms and common in monoraphid diatoms. We compared the morphometric characteristics of genus Yuzaoea with genus Rhoikoneis and several genera within the family Rhoicospheniaceae, including Rhoicosphenia,Campylopyxis, and Cuneolus. Phylogenetic analyses based on SSU rRNA and rbc L showed that the genus Yuzaoea was the sister group to the clade of Rhoicosphenia with a high support value(bootstrap values = 100%), and the clade “Yuzaoea+Rhoicosphenia” was sister to the clade of monoraphid diatoms, in which the genera Achnanthidium, Planothidium and some Cocconeis with high support values(bootstrap = 100%).Morphologically, the genus Yuzaoea shares many morphological features with monoraphid diatoms like genera Achnanthidium and Planothidium and the members within the Rhoicospheniaceae. Therefore, based on a combined morphological studies and phylogenetic results we suggested that this branch may represented the evolution of one kind monoraphid diatoms, from biraphid diatoms(e.g. genus Yuzaoea), to incompleted biraphid diatoms(e.g. genera Rhoicosphenia, Campylopyxis), to monoraphid diatoms(e.g. genera Achnanthidium and Planothidium).

The Middle and Late Holocene climate change in Bohai Bay revealed by diatom proxy

A total of 98 samples from two boreholes in shallow sea area and two oyster reefs in adjacent coastal plain in the northwestern coast of Bohai Bay were collected for diatom analyses and species identification.The ratio of the marine species Thalassionema nitzschioides to the intertidal-coastal species complex Cyclotella striata/stylorum serves as a novel proxy for assessing the strength of marine influence.Chronological data,corrected for the local residence time effect,facilitated the construction of a diatom proxy-based marine influence curve for the study area.This curve delineates the dynamics of marine influence and their correlations with paleo-climate fluctuations and the East Asian monsoon variability,as well as their role in chenier formation.Results include:(1)eight periods of intensified marine influence have been documented since 7000 a BP in the study area.The peak of each period,as determined by the diatom proxy,corresponds closely to the warm climatic phases and stronger East Asian summer monsoons,suggesting that the peaks marine influence indicate typically the periods of climatic warmth and monsoon activity intensification in the region;(2)a strong correlation exists between the development of cheniers and marine influence,and chenier formation began with the increasing marine influence and terminated at the end of warm periods as marine influence weakens.The climatic changes in the coastal area,as indicated by the diatom proxy,hold significant potential for future related research endeavors.

Theoretical investigation of excited dipole bound states of alkali-containing diatomic anions

Information about electronic excited states of molecular anions plays an important role in investigating electron attachment and detachment processes.Here we present a high-level theoretical study of the electronic structures of 12 alkali-metal-containing diatomic anions MX-(MX = LiH,LiF,LiCl,NaF,NaCl,NaBr,RbCl,KCl,KBr,RbI,KI and CsI).The equation-of-motion electron-attachment coupled-cluster singles and doubles(EOM-EA-CCSD) method is used to calculate the electron binding energies(EBEs) of 10 electronic excited states of each of the 12 molecule anions.With addition of different s-/p-/d-type diffusion functions in the basis set,we have identified possible excited dipole bound states(DBSs) of each anion.With the investigation of EBEs on the 12 MXs with dipole moment(DM) up to 12.1 D,we evaluate the dependence of the number of anionic excited DBSs on molecular DM.The results indicate that there are at least two or three DBSs of anions with a molecular DM larger than 7 D and a molecule with DM > 10 D can sustain a π-DBS of the anion.Our study has some implications for the excited DBS electronic states of alkali-metal-containing diatomic molecules.

Diatoms as indicators of environmental change in coastal areas:a case study in Lianjiang coast of East China Sea

Owing to the significant differences in environmental characteristics and explanatory factors among estuarine and coastal regions,research on diatom transfer functions and database establishment remains incomplete.This study analysed diatoms in surface sediment samples and a sediment core from the Lianjiang coast of the East China Sea,together with environmental variables.Principal component analysis of the environmental variables showed that sea surface salinity(SSS)and sea surface temperature were the most important factors controlling hydrological conditions in the Lianjiang coastal area,whereas canonical correspondence analysis indicated that SSS and pH were the main environmental factors affecting diatom distribution.Based on the modern diatom species–environmental variable database,we developed a diatom-based SSS transfer function to quantitatively reconstruct the variability in SSS between 1984 and 2021 for sediment core HK3 from the Lianjiang coastal area.The agreement between the reconstructed SSS and instrument SSS data from 1984 to 2021 suggests that diatombased SSS reconstruction is reliable for studying past SSS variability in the Lianjiang coastal area.Three low SSS events in AD 2019,2013,and 1999,together with an increased relative concentration of freshwater diatom species and coarser sediment grain sizes,corresponded to two super-typhoon events and a catastrophic flooding event in Lianjiang County.Thus,a diatom-based SSS transfer function for reconstructing past SSS variability in the estuarine and coastal areas of the East China Sea can be further used to reflect the paleoenvironmental events in this region.

The Expression Characteristics and Potential Functions of Heat Shock Factors in Diatom Phaeodactylum tricornutum

Heat shock transcription factor(HSF)are essential regulators of heat shock protein(HSP)gene expression in plants and algae,contributing to their resilience against biotic and abiotic stresses.However,the localization,structure,phylogenetic relationship,and characteristics of PtHSF genes in microalgae,especially in diatom Phaeodactylum tricornutum,remain largely unexplored.This study presents a comprehensive analysis of the PtHSF gene family in P.tricornutum.A genome-wide analysis identified 68 PtHSF genes,which were classified into two distinct subfamilies:traditional and untraditional.Motif and structure analyses revealed evidence of multiple duplication events within the PtHSF gene family.Expression profiling revealed diurnal patterns,with 34 genes being downregulated during the light period and upregulated during the dark period,while 19 genes exhibited the opposite pattern.These findings suggest that PtHSF genes may have specialized functions during the diurnal cycle and play a crucial role in maintaining cellular homeostasis in response to various stresses.Notably,PtHSF16,30,and 43 genes exhibited higher expression levels,suggesting their potential importance.This study provides a valuable foundation for future investigations into the specific functions of HSFs under different stress conditions and their regulatory mechanisms in P.tricornutum and other microalgae.

The role of copper in enhancing the performance of heteronuclear diatomic catalysts for the electrochemical CO_(2)conversion to C_(1) chemicals

Diatomic catalysts(DACs)with two adjacent metal atoms supported on graphene can offer diverse functionalities,overcoming the inherent limitations of single atom catalysts(SACs).In this study,density functional theory calculations were conducted to investigate the reactivity of the carbon dioxide(CO_(2))reduction reaction(CO_(2)RR)on metal sites of both DACs and SACs,as well as their synergistic effects on activity and selectivity.Calculation of the Gibbs free energies of CO_(2)RR and associated values of the limiting potentials to generate C_(1) products showed that Cu acts as a promoter rather than an active catalytic centre in the catalytic CO_(2)conversion on heteronuclear DACs(CuN_(4)-MN_(4)),improving the catalytic activity on the other metal compared to the related SAC MN_(4).Cu enhances the initial reduction of CO_(2)by promoting orbital hybridization between the key intermediate*COOH 2p-orbitals and the metals 3d-orbitals around the Fermi level.This degree of hybridization in the DACs CuN_(4)-MN_(4) decreases from Fe to Co,Ni,and Zn.Our work demonstrates how Cu regulates the CO_(2)RR performance of heteronuclear DACs,offering an effective approach to designing practical,stable,and high-performing diatomic catalysts for CO_(2)electroreduction.

Quantitative relationship between surface sedimentary diatoms and water depth in North-Central Bohai Bay,China

To study the quantitative relationship between surface sedimentary diatoms and water depth,67 surface samples were collected for diatom analysis on eight profiles with water depth variation from the muddy intertidal zone to the shallow sea area in North-Central Bohai Bay,China.The results showed that the distribution of diatoms changed significantly in response to the change in water depth.Furthermore,the quantitative relationship between the distribution of dominant diatom species,their assemblages,and the water depth was established.The water depth optima for seven dominant species such as Cyclotella striata/stylorum,Paralia sulcata,and Coscinodiscus perforatus and the water depth indication range of seven diatom assemblages were obtained in the study area above the water depth(elevation)of-10 m.The quantitative relationship between surface sedimentary diatoms and water depth provides a proxy index for diatom-paleo-water depth reconstruction in the strata in Bohai Bay,China.

Paclobutrazol induces the concurrent accumulation of chrysolaminarin and lipids in the diatom Phaeodactylum tricornutum

Paclobutrazol is a plant growth regulator and inhibitor of endogenous gibberellin synthesis.It is a powerful inhibitor of vegetative growth by changing the photosynthetic rate and plant hormone levels,thereby affecting plant growth and development.In this study,the effects of paclobutrazol on the model diatom Phaeodactylum tricornutum were investigated.Results show that 2.5-mg/L and 10-mg/L paclobutrazol significantly inhibited the algal growth by inhibiting chlorophyll synthesis,which affects photosynthesis.The antioxidant system,including catalase(CAT)and glutathione peroxidase(GPx)was severely damaged.Chrysolaminarin content was significantly elevated and doubled up to 127 mg/g dry cell weight(DCW)by 10-mg/L paclobutrazol treatment.In combination with transcriptomic analysis,paclobutrazol was demonstrated to play a regulatory role in the accumulation of chrysolaminarin and neutral lipids.

Environmental heterogeneity and productivity drive the assemblage of benthic diatom:a case study of the Three Gorges Reservoir

Dam construction has a critical effect on river ecosystems in the world,resulting in a rapid decline in biodiversity and ecosystem health.However,the effect of dam construction on the assemblage pattern of benthic diatoms remains unclear.The benthic diatoms assemblages in the tributary backwater area of the Three Gorges Reservoir(TGR)were investigated under low water level(LWL)and high water level(HWL)conditions.Results show that Discostella stelligera,Nitzschia palea,and Craticula subminuscula were dominant species in LWL,while Achnanthidium minutissimum and Nitzschia dissipata were dominant in HWL.Furthermore,environmental variables,productivity parameters,diversity indices,and community similarity were found significantly different between LWL and HWL periods.The Mantel test indicated that both environmental and spatial factors had significant effects on diatom communities in backwater area,while productivity was also a key driving force in LWL.The variation partitioning analysis(VPA)further demonstrated that environment factors could explain the largest variance of diatom assemblages in HWL(9%)and LWL(11%),followed by spatial factors.The relative importance of productivity to diatom community was significantly enhanced in LWL,but only a slight effect was found in HWL.These results indicate that the diatom assemblages were shaped by both environmental filtering and spatial factors.The relative importance of spatial factors depended on the degree of productivity.Therefore,the homogenization of diatom communities due to environmental disturbance,e.g.eutrophication and dam building,is the underlying mechanism in assembling the benthic diatoms.

Mechanistic Insights into Electrocatalytic Nitrogen Reduction Reaction on the Pd-W Heteronuclear Diatom Supported on C_(2)N Monolayer:Role of H Pre-Adsorption

The electrocatalytic N_(2) reduction reaction(eNRR)is a potential alternative to the Haber-Bosch process for ammonia(NH3)production.Tremendous efforts have been made in eNRR catalyst research to promote the practical application of eNRR.In this work,by means of density functional theory calculations and the computational hydrogen electrode model,we evaluated the eNRR performance of 30 single metal atoms supported on a C_(2)N monolayer(M@C_(2)N),and we designed a new thermodynamically stable Pd-W hetero-metal diatomic catalyst supported on the C_(2)N monolayer(PdW@C_(2)N).We found that PdW@C_(2)N prefers to adsorb H over N_(2),and then,the pre-generated hydrogen-terminated PdW@C_(2)N selectively adsorbing N_(2) behaves as the actual functioning“catalyst”to catalyze the eNRR process,exhibiting excellent performance with a low overpotential(0.31 V),an ultralow NH3 desorption free energy(0.05 eV),and a high selectivity toward eNRR over hydrogen evolution reaction(HER).Moreover,PdW@C_(2)N shows a superior eNRR performance to its monomer(W@C_(2)N)and homonuclear diatom(W_(2)@C_(2)N)counterparts.The revealed mechanism indicates that the preferential H adsorption over N_(2) on the active site may not always hamper the eNRR process,especially for heteronuclear diatom catalysts.This work encourages deeper exploration on the competition of eNRR and HER on catalyst surfaces.

Rational design of Fe/Co-based diatomic catalysts for Li–S batteries by first-principles calculations

Fe/Co-based diatomic catalysts decorated on an N-doped graphene substrate are investigated by first-principles calculations to improve the electrochemical properties of Li–S batteries.Our results demonstrate that Fe CoN8@Gra not only possesses moderate adsorption energies towards Li2Snspecies,but also exhibits superior catalytic activity for both reduction and oxidation reactions of the sulfur cathode.Moreover,the metallic property of the diatomic catalysts can be well maintained after Li2Snadsorption,which could help the sulfur cathode to maintain high conductivity during the whole charge–discharge process.Given these exceptional properties,it is expected that Fe CoN8@Gra could be a promising diatomic catalyst for Li–S batteries and afford insights for further development of advanced Li–S batteries.

Diatom-based dissolved inorganic nitrogen reconstruction in the Changjiang River estuary and its adjacent areas

A five-component weighted average partial least squares(WA-PLS)calibration model was developed by analysing diatom assemblages in 34 surface sediment samples(collected in 2015)from the Changjiang River estuary(CRE)and its adjacent areas to infer dissolved inorganic nitrogen(DIN)concentrations.Eighteen additional sets of surface sediment diatoms and corresponding upper water DIN data(collected in 2012)were used to evaluate the accuracy of the model,and the relationship between observed and diatom-inferred DIN(DI-DIN)values(R2=0.85)illustrated the strong performance of the transfer function,indicating that precise reconstructions of former DIN are possible.The diatom-DIN transfer function was applied to the diatom record from a sediment core DH8-2(1962‒2012)collected in the Fujian-Zhejiang area south of the CRE.The reconstruction based on the DI-DIN model showed a significant DIN increase from 1962-2012,reflecting the influence of human activities on the very large increase in eutrophication.Three distinct periods can be seen from the changes in DIN and diatom taxa.In the 1962-1972 period,the DIN content was relatively low,with an average of 5.94μmol/L,and more than 80%of the diatom species identified were benthic taxa.In the 1972-2004 period,as the impact of human activities intensified,large nutrient inputs caused the DIN content to increase,with an average of 8.25μmol/L.The nutrient inputs also caused a significant change in the nutrient components and a distinct increase in small planktonic taxa.In the 2004-2012 period,the DIN content continued to rise,fluctuating at approximately 10μmol/L.A continuous increase in the frequency of planktonic taxa(up to 65.48%)indicated that eutrophication was further intensified,which was confirmed by the transformation from diatom-induced red tide to dinoflagellate-induced red tide during this period.

Novel Proposal of Bio-based Sewing Timber Joint:Learning from Diatoms

The twenty-first century is one of the most complex in the history of humanity,mainly due to the ecological crisis it is going through.The construction sector generates about 40%of CO2 emissions into the environment;the foregoing should motivate this sector to seek new alternatives to develop new building practices.Taking these current needs into account,this document classifies and presents a multidisciplinary solution that integrates biology,engineering and architecture to develop a new and innovative lightweight timber structure;it divides with a main structure made of timber and an innovative joint system made of bio-polymers connecting all the panels.Through the study of diatoms,it was able to analyze the bio-morphology of the structure,joints and in particular the geometry since they were the inspiration for the design of this structure that presents an innovative and novel design of structural optimization.Through parametric design and digital fabrication,it was able to create a complex geometry that obtains excellent structural behavior.This research discusses and explores how materials,geometry led to the optimization of a structure and how new structures can arise,thanks to biology new solutions can be obtained that are completely sustainable,being a clear example of how to combat the effects of the climate change and in a precise way it highlights the advantages of the bio-design in the architectural design.

超高选择性CO_(2)光还原为乙醇的CuNi异核双原子催化剂的精准设计

利用光催化还原技术将CO_(2)定向转化为乙醇(CO_(2)-乙醇)是解决日益严重的环境污染和能源危机的理想途径之一.然而,CO_(2)分子的高化学惰性以及C-C耦合反应的高化学能垒导致目前CO_(2)-乙醇转化反应的产率和选择性较低.因此,设计构建能够快速活化CO_(2)分子并同时促进C-C耦合的光催化材料具有重要研究意义.尽管已有研究表明,Cu+物种在促进C-C耦合方面具有一定优势,但其在催化反应过程中的不稳定性限制了其实际应用.基于上述认识,本文通过理论模拟预测发现,相比于Cu单原子,CuNi异核双原子(CuNi HDAs)不仅在CO_(2)活化及C-C耦合方面更具优势,而且能够有效锚定并固化Cu+物种.因此,本文设计了一种三步合成策略,精准地将Cu单原子锚定在(Ni,Zr)-UiO-66-NH2材料的Ni位上,合成了以CuNi HDAs为活性位点的Cu-(Ni,Zr)-UiO-66-NH2光催化材料.在可见光照射下,Cu-(Ni,Zr)-UiO-66-NH2表现出较好的催化CO_(2)-乙醇转化活性,其乙醇的产率和选择性分别达到~3218μmol·gCu^(-1)·h^(-1)和97.3%.光谱分析和密度泛函理论计算结果表明,Cu-(Ni,Zr)-UiO-66-NH2材料较好的光催化性能来源于CuNi HDAs特殊的电子结构.首先,CuNi HDAs通过CuNi-O界面化学键与吸光组分(Ni,Zr)-UiO-66-NH2相连,利用界面Cu-Ni-O键作为快速电子传输通道,CuNi HDAs能够富集到足够的光生电子用于涉及12电子的CO_(2)-乙醇转化反应,使得乙醇产率大幅提升.其次,Cu,Ni和O三种原子由于电子亲核能的差异,导致CuNi HDAs的电子分布呈现不对称性.这种不对称的电子结构能有效诱导CO_(2)分子的极化,打破其结构的对称性,从而显著降低CO_(2)分子的活化能.再次,相比于Cu单原子,CuNi HDAs对*CO中间体的吸附能力更强,这不仅增强了活性位点表面*CO中间体的覆盖度,还抑制CO的生成,为C-C耦合创造了充分条件.最后,由于Cu-Ni双活性位电子密度的差异,CuNi HDAs表面的C-C耦合反应势能较低,有利于*OCCHO中间体的快速生成,从而使乙醇产物的选择性大幅提升.综上,本文以理论计算模拟为指导,以UiO-66-NH2材料为基底,成功设计并制备了一种具有不对称电子结构的CuNi HDAs光催化材料,实现了高选择性CO_(2)光还原为乙醇.研究表明,CuNi HDAs的不对称结构在促进分子活化和降低C-C耦合反应能垒中起关键作用,同时促进了光生电子在CuNi HDAs活性位的富集.本文的研究结果为在原子尺度上设计并合成高性能的CO_(2)还原光催化剂提供了实验和理论参考.

砂质海岸底栖硅藻的研究进展

文章综述了国内外关于砂质海岸底栖硅藻的研究进展。作为砂质海岸主要的植物群,底栖硅藻通过一系列机制以适应多变的沙生环境。在潮间带的沉积物中,底栖硅藻是初级生产力和沙滩食物网的重要组成部分。沉积物、温度、盐度、光照、营养盐和生物因素等等都会对底栖硅藻的生长和群落分布产生影响。近年来,陆续有了关于我国潮间带底栖硅藻群落分布特征的研究,但总体来说,关于沙生境底栖硅藻的研究相对较少,需要进一步的调查以完善我国的硅藻生态学研究。

春季桑沟湾硅藻群落结构对硅酸盐加富的响应研究

2021年5月,在水温13.83~16.96℃下,用现场陆基围隔实验方法研究添加硅酸盐对山东荣成桑沟湾养殖海区浮游植物丰度(以叶绿素a浓度表征)、粒径结构以及群落结构的影响。体积为100 L的直筒型透明聚乙烯袋围隔而成的实验单元,设置3个处理组,每组三个平行:自然海水组1.41μmol/L SiO_(3)-Si(对照组);低浓度组20.00μmol/L SiO_(3)-Si(LS组);高浓度组100.00μmol/L SiO_(3)-Si(HS组);取桑沟湾近岸表层海水70 L,经200μm筛绢过滤后注入实验单元,每个实验单元中均配置2 W的小型抽水泵,保持海水始终处于混匀状态,不与外部水体交换,添加的硅酸盐为分析纯九水硅酸钠,并固定在长200 cm、宽160 cm、高120 cm,容积约3 800 L的陆基围隔中,实验持续时间7 d。结果显示:(1)添加硅酸盐可提高浮游植物叶绿素a浓度,LS组和HS组叶绿素a浓度分别是对照组的1.95倍和1.94倍,主要是小型浮游植物和微型浮游植物的叶绿素a浓度显著提高;(2)硅藻是浮游植物群落结构的优势种,占物种丰富度的77.27%,硅藻细胞丰度变化范围为0.96×103~1.62×103cells/L,LS组和HS组的硅藻细胞丰度比对照组分别增加了53.53%和69.77%;(3)添加硅酸盐显著促进了小环藻(Cyclotella)、小新月菱形藻(Nitzschia closterium f.minutissima)、圆海链藻(Thalassiosira rotula)等生长(P<0.05),其中小新月菱形藻的藻细胞丰度增加显著,比对照组增加了181.69%;(4)添加硅酸盐对浮游植物多样性和均匀度无显著影响,但可显著增加浮游植物群落结构的物种丰富度(P<0.05)。本结果将为后续探索养殖水域关键时段硅元素补充策略、研发浮游植物初级生产力提升技术进而提高贝类养殖容量的可能性提供基础数据和有价值的线索。

基于eDNA宏基因组的草海湖泊硅藻群落及多样性分析

环境DNA(eDNA)技术作为新兴生物多样性监测方法,具有非侵入性、高效性及灵敏性的特点.为探究基于宏基因组测序的eDNA技术对喀斯特湖泊硅藻监测的适用性,以贵州草海为例,采集草海湖滨带的水样及表层沉积物样品,运用宏基因组学与eDNA相结合的方法,分析浮游及沉积硅藻的群落组成、生物多样性及KEGG代谢功能.结果表明:①草海硅藻群落共注释到4纲23目36科54属78种,在科分类阶元上以舟形藻科和海链藻科为优势类群.硅藻群落的Chao1指数平均值为42.88±15.35,Shannon-Wiener指数平均值为2.09±0.29.②硅藻群落KEGG通路功能最具代表性的是全局和概述图谱(global and overview maps),其次是能量代谢、翻译;优势KO基因主要为atpF基因、secA基因、rplT基因、rpoA基因、argH基因.③主坐标分析(PCoA)和相似性分析(ANOSIM)表明硅藻群落存在显著的环境介质差异;LEfSe分析揭示浮游硅藻群落的差异标志物主要为海链藻属(Thalassiosira)、小环藻属(Cyclotella),沉积硅藻主要是管状藻属(Fistulifera)、褐指藻属(Phaeodactylum)、微壳藻属(Nanofrustulum)等;Wilcoxon秩和检验表明,浮游硅藻的差异基因集中在叶酸生物合成通路、嘧啶代谢,沉积硅藻的差异基因集中在光合作用、氧化磷酸化等代谢功能.研究显示,高灵敏性的eDNA宏基因组技术能有效描述草海湖泊硅藻群落及多样性,在喀斯特湖泊生物多样性监测及水生态环境健康评估具有广阔的应用前景.

淡水硅藻水华成因与控制技术研究进展

在全球气候变暖和人类活动的共同影响下,硅藻水华爆发趋势加剧,并对水生态及供水安全产生负面影响.因此明确其形成原因并探索高效的防控技术至关重要.目前关于淡水硅藻水华已有较多研究成果,但缺少系统性整理.淡水硅藻水华爆发的关键因素为温度、光照、营养盐和流速.在原位防控方面,生态调度和扬水曝气等物理技术较为成熟,低剂量的化学药剂处理效果不佳,而生物方法的实施会受到环境条件的限制.联合使用混凝剂和助凝剂或氧化剂可以有效去除硅藻,但硅藻水华范围的扩大致使部分水厂未能及时调整工艺,影响制水效率.本文对硅藻水华的成因及防治方法进行了分析和总结,与蓝藻水华进行比较,并展望后续研究热点,对确保饮用水安全和水体污染控制与治理有着重要意义.