Morphogenesis and Molecular Phylogeny of a Marine Urostylid Ciliate Apokeronopsis wrighti(Protista, Ciliophora, Hypotrichia)

Hypotrichs are one of the highly differentiated ciliated lineages which play important roles in ecological, environmental,evolutionary and basic biological studies. In the present study, we investigated the living characteristics, infraciliature, nuclear apparatus, ontogenesis and phylogenetic position of a marine hypotrichous ciliate, Apokeronopsis wrighti Long et al., 2008, which was isolated from coastal waters in Shenzhen, China. The new isolate resembles the type population in terms of morphological characteristics, morphometrics, and SSU rRNA gene sequence that is with a 99.7% similarity. Ontogenesis of A. wrighti is characterized by oral primordium for the proter as well as marginal and dorsal kineties anlagen in both filial products formed de novo, and the cirral row arranged along the paroral and endoral arises from several anterior frontoventral-transverse cirral streaks. Phylogenetic analyses based on SSU and concatenated gene data suggest that five species of Apokeronopsis form a monophyletic clade, and the genus Apokeronopsis is closely related to Thigmokeronopsis and Metaurostylopsis.

Protist Interactions and Seasonal Dynamics in the Coast of Yantai, Northern Yellow Sea of China as Revealed by Metabarcoding

Facilitated by the high-throughput sequencing(HTS)technique,the importance of protists to aquatic systems has been widely acknowledged in the last decade.However,information of protistan biotic interactions and seasonal dynamics is much less known in the coast ecosystem with intensive anthropic disturbance.In this study,year-round changes of protist community composition and diversity in the coastal water of Yantai,a city along the northern Yellow Sea in China,were investigated using HTS for the V4 region of 18S rDNA.The interactions among protist groups were also analyzed using the co-occurrence network.Data analyses showed that Alveolata,Chlorophyta,and Stramenopiles are the most dominant phytoplanktonic protists in the investigated coastal area.The community composition displayed strong seasonal variation.The abundant families Dino-Group-I-Clade-1 and Ulotrichales_X had higher proportions in spring and summer,while Bathycoccaceae exhibited higher ratios in autumn and winter.Alpha diversities(Shannon and Simpson)were the highest in autumn and the lowest in spring(ANOVA test,P<0.05).Nutrients(SiO42−,PO43−),total organic carbon(TOC),and pH seemed to drive the variation of alpha diversity,while temperature,PO43−and TON were the most significant factors influencing the whole protist community.Co-variance network analyses reveal frequent co-occurrence events among ciliates,chlorophytes and dinoflagellate,suggesting biotic interactions have been induced by predation,parasitism and mixotrophy.

Planktonic protist communities in semi-enclosed mariculture waters: temporal dynamics of functional groups and their responses to environmental conditions

The functional groups of planktonic protist communities and their responses to the changes of environmental conditions were investigated in a semi-enclosed shrimp-farming pond in Qingdao,Shandong Province,China,during a six-month study period （a complete shrimp-culture cycle） from May to October 2002.The results reveal that： （1） the protist communities represented five trophic and functional groups of the species identified,about 60% were photoautotrophs,20% algivores,12% bacterivores,5% raptors and about 3% non-selectives;（2） the photoautotrophs,algivores and bacterivores were the primary contributors to the changes in the protist communities in short temporal scales,the succession of dominance typically being bacterivores→photoautotrophs→algivores,with the raptors dominating the protist communities in a single sample （early June）;（3） the photoautotrophs and non-selectives were the primary contributors to the peak of protist abundance in early October whereas the photoautotrophs,bacterivores,raptors and non-selectives mainly gave rise to two bimodal peaks of biomass in July and October respectively;（4） five functional groups of protist communities represented significant correlations with water nutrients （i.e.,NH 3-N,NO 3-N,and PO 4 ）,either alone or in combination with temperature,of which algivores and raptors were strongly correlated with phosphate and the concentration of Chl a,while bacterivores were strongly related to nitrogen and the concentration of bacteria.These findings confirm that planktonic protists are potentially useful bioindicators of water quality in the semi-enclosed mariculture system.

Temporal species distributions of planktonic protist communities in semi-enclosed mariculture waters and responses to environmental stress

In order to evaluate the relationships between temporal species succession of planktonic protists and physical-chemical parameters in semi-enclosed mariculture waters, species distributions in response to environmental stress were investigated in a shrimp-farming pond near Qingdao, China during a complete shrimp-culture cycle （May to October 2002）. A clear temporal succession in species distribution was found over the complete farming cycle. For example, before the introduction of the shrimp larvae there was low-variability of species distribution in the protist communities whereas during the stages immediately after, there was higher variability in species composition. Multiple linear/logistic regression analyses demonstrate that 12 protist taxa （e.g., Gyrodinium spirale, Teleaulax acuta, Prorocentrum spp. and Mesodinium pupula） were related to the nutrients, in particular ammonia and phosphates, alone or in combination with water temperature. These results suggest that temporal variations in species distribution of planktonic protist communities might be used in assessing water quality of semi-enclosed mariculture waters.

Effect of Mariculture on Planktonic Protist:A Case Study in a Marine Ranch of Northern Yellow Sea,China

Mariculture exerts a direct influence on planktonic eukaryotic microorganisms protists.Previous studies have focused on phytoplankton,while the heterotrophic and parasitic protistan groups are unknown.Currently,in Muping Marine Ranch(MR)which is along the littoral zone of northern Yellow Sea of China,environmental DNA methods were employed to investigate the diversity and seasonal dynamics of near shore planktonic protists in response to mariculture.Through an integrated analysis of functional groups and a comparison to adjacent sea areas,we found a dominance of harmful algae blooms(HAB)species nearshore MR,and a significant reduction in the diversity of planktonic protists including photosynthetic,heterotrophic and parasitic groups.High nutrient and low salinity were suggested to drive the dominance of HAB species nearshore MR,which in return might inhibit predators,saprophytes and algal parasites.Our investigations revealed an Olisthodiscus luteus outbreak in spring,as well as significant seasonal variations in the planktonic protist community,which might be caused by the changes of temperature.The offshore hypoxia reduced the abundance of phytoplankton but increased mixotrophs and animal parasites of the protistan community nearshore MR.This study highlights the influence of mariculture on the overall community function of planktonic protists,and is helpful to assess the mariculture's impact on water health.

Nitrogen-based fertilizers differentially affect protist community composition in paddy field soils

Protists are one of the most diverse and dominant microbial groups and they play critical roles in the soil ecosystem.Although nitrogen fertilizers have a profound impact on protist communities,still less is known about how different nitrogen fertilizer types affect protist community composition in different soil types.Here we investigated the effects of six inorganic nitrogen fertilizers(urea,ammonium nitrate,ammonium sulfate,potassium nitrate,ammonium chloride,and diammonium hydrogen phosphate)and an organic fertilizer(a mixture of rice husk and cow manure)on protist community composition in three paddy field soils using a high-throughput sequencing method.The effect of the fertilizers on the functional groups of protists,namely consumers(predators and decomposers),photoautotrophs,and parasites(plant pathogens and animal parasites)was also analyzed.The results showed that nitrogen fertilizers had distinctive effects on the beta diversity of the protists,while we also observed that the same fertilizer had slightly different effects depending on the soil type.Amoebozoa and Rhizaria were the most affected protist taxonomical groups,while predatory protists were the main functional groups that were affected by nitrogen fertilizers.Random forest analysis showed that most of the fertilizer-affected protists were predators,among which Cercozoa was the most affected taxa.In conclusion,our results provide important insights into the impact of nitrogen fertilizers on soil protist communities.

From oral structure to molecular evidence:new insights into the evolutionary phylogeny of the ciliate order Sessilida(Protista,Ciliophora),with the establishment of two new families and new contributions to the poorly studied family Vaginicolidae

Ciliated protists represent one of the most primitive and diverse lineages of eukaryotes,with nuclear dimorphism,a distinctive sexual process(conjugation),and extensive genome rearrangements.Among divergent ciliate lineages,the peritrich order Sessilida includes members with a colonial lifestyle,which may hint to an independent evolutionary attempt for multicellularity,although they are still single-celled organisms.To date,the evolution and phylogeny of this group are still far from clear,in part due to the paucity of molecular and/or morphological data for many taxa.In this study,we extend taxon sampling of a loricate group of sessilids by obtaining 69 new r DNA(SSU r DNA,ITS1-5.8S rDNA-ITS2,and LSU r DNA)sequences from 20 wellcharacterized representative species and analyze the phylogenetic relationships within Sessilida.The main findings are:(i)the genera Rhabdostyla and Campanella each represents a unique taxon at family level,supporting the establishment of two new families,i.e.,Rhabdostylidae n.fam.and Campanellidae n.fam.,respectively,the former being sister to a morphologically heterogeneous clade comprising Astylozoidae and several incertae sedis species and the latter occupying the basal position within the Sessilida clade;(ii)the structure of infundibular polykinety 3 is likely to be a phylogenetically informative character for resolving evolutionary relationships among sessilids;(iii)differences between sparsely and the densely arranged silverline systems could be a suprageneric taxonomic character;(iv)the monophyly of Vaginicolidae is confirmed,which is consistent with its specialized morphology,i.e.,the possession of a typical peritrich lorica which might be an apomorphy for this group;(v)within Vaginicolidae,the monotypic Cothurniopsis sensu Stokes,1893 is a synonym of Cothurnia Ehrenberg,1831,and a new combination is created,i.e.,Cothurnia valvata nov.comb.;(vi)Vaginicola sensu lato comprises at least two distinctly divergent clades,one affiliated with Thuricola and the other with a systematically puzzling clade represented by Vaginicola tincta.

Responses of protists with different feeding habits to the changes of activated sludge conditions:A study based on biomass data

Changes of protists, which were categorized into different functional groups primarily according to their feeding habits, in two full-scale municipal wastewater treatment systems experiencing sludge bulking were investigated over a period of 14 months. Protist biomass represented 3.7% to 5.2% of total biomass on average under normal sludge conditions, and the percentage increased significantly （p 〈 0.05） under sludge bulking conditions. The biomass of Chilodonella spp., capable of eating filamentous bacteria, tended to decrease in both systems when sludge bulking occurred, showing that the abnormal growth of filamentous bacteria did not lead to a biomass bloom of this group of protists. On the other hand, the bactivorous protists represented more than 96% of total protist biomass, and the biomass of this group, particularly the attached ciliates, increased significantly （p 〈 0.05） when sludge bulking occurred. The significant increase of the attached ciliates may have possibly facilitated the growth of filamentous bacteria through selectively preying on non-filamentous bacteria and further exacerbated sludge bulking. The redundancy analysis and correlation analysis results showed that the biomass changes of the attached ciliates were primarily related to the sludge volume index and to some extent related to five-day biochemical oxygen demand loading and hydraulic retention time.

Spatiotemporal distribution of protists in the Yarlung Zangbo River,Tibetan Plateau

Protists,which include eukaryotic algae and protozoa,are crucially important for biogeochemical cycling and the aquatic food web but are sensitive to environmental fluctuations.Despite investigations in the 1970s,protist diversity and biogeographic characteristics in the Tibetan Plateau are poorly understood.Within the framework of a regional survey of protist diversity,we used high-throughput amplicon sequencing to investigate the composition and spatiotemporal turnover of protist communities along the Yarlung Zangbo River,a representative aquatic habitat of the Tibetan Plateau.In total,we detected 9,959 amplicon sequence variants in protist communities along the river and associated lakes and wetlands.The alpha diversity of protists was highest in spring and declined in the autumn.Moreover,alpha diversity was much higher in the middle and upstream reaches and tributaries than in the connected lakes and wetlands.We discovered spatiotemporal heterogeneity in the composition of protist communities across the seasons.Bacillariophyta predominated in protist communities in cold seasons(spring and autumn)and colder(high-altitude)areas,whereas Ciliophora and Cercozoa species predominated in the warm season(summer)and warmer(low-altitude)areas.Of the environmental factors,altitude,turbidity and salinity correlated with spatiotemporal dissimilarities among protist communities.The breadth of the habitat niche was restricted by turbidity and altitude in river areas and by salinity in lake and wetland areas.Co-occurrence network analysis suggested that protist communities in the Yarlung Zangbo River were substantially more complex in the warm season than in the cold seasons,and that amplicon sequence variants belonging to Ochrophyta,Chlorophyta,and Ciliophora contributed greatly to the stability of the cooccurrence network.In summary,this study provides a comprehensive overview of the spatiotemporal dynamics of protist diversity in the Yarlung Zangbo River and improves our understanding of the environmental adaptation of protists living in aquatic habitats of the Tibetan Plateau.

Divergent changes in diversity and network complexity across different trophic-level organisms drive soil multifunctionality of fire-impacted subtropical forests

Widespread forest fires pose significant challenges to the diverse communities of soil-dwelling organisms and the multiple ecosystem functions they support.However,whether the biodiversity and interactions of various taxonomic groups respond to fire consistently in terms of direction and extent,and their relative role in regulating post-fire soil functioning,remains largely unexplored.In this study,we investigated whether the diversity and co-occurrence networks of soil organisms across various trophic levels(including bacteria,fungi,protists,and invertebrates)in subtropical forests exhibit consistent responses to fire.Furthermore,we investigated their contribution to regulating soil multifunctionality,which is measured by a range of soil extracellular enzyme activities,available nutrients and reduced potential fungal plant pathogens.Our findings revealed that fire led to a decline in the richness of fungi,protists,and invertebrates,without significantly impacting bacterial richness.Fire also simplified the microbial co-occurrence networks while complexifying the invertebrate networks.Interestingly,soil multifunctionality tended to decrease with the richness of lower-trophic communities(i.e.,bacteria),whereas it increased with that of high-trophic communities(i.e.,protists and invertebrates).Moreover,fire indirectly influenced soil multifunctionality by altering biodiversity and network complexity,particularly pronounced in high-trophic communities.Overall,our results underscored the divergent vulnerability of biodiversity and networks to fires across taxa groups,highlighting the crucial role of biodiversity and interactions of higher trophic taxa groups in shaping the recovery and functionality of fire-affected soils.

Salinity Acclimation Induces Reduced Energy Metabolism,Osmotic Pressure Regulation and Transcriptional Reprogramming in Hypotrichida Ciliate Gastrostyla setifera

Coastal and estuarine protists are frequently exposed to salinity undulation.While the tolerance and stress responses of microalgae to salinity have been extensively studied,there have been scarce studies on the physiological response of heterotrophic protists to salinity stressing.In this study,we investigated the physiological response of the heterotrophic ciliate Gastrostyla setifera to a salinity of 3,via a transcriptomic approach.The first transcriptome of genus Gastrostyla was obtained utilizing a group of manually isolated ciliate individuals(cells)and RNA-seq technique.The completeness of the transcriptome was verified.Differentially expressed gene(DEG)analysis was performed among the transcriptomes of G.setifera acclimated in saline water(salinity 3)and those cultured in fresh water.The results demonstrated a significant alternation in gene transcription,in which the ciliate exhibits a transcripttomic acclimation in responding salinity stressing.The up-regulated DEGs were enriched in the pathways of cytoskeleton proteins,membrane trafficking,protein kinases and protein phosphatases.These may represent enhanced functions of ion transport,stress response and cell protections.Pathways involved in energy metabolism and biosynthesis were markedly down-regulated,reflecting decreased cell activity.Particularly,we detected significantly down-regulated genes involved in several pathways of amino acid catabolism,which may lead to accumulation of amino acids in the ciliate cell.Amino acid could act as compatible solutes in the cytoplasm to maintain the osmotic balance in saline water.Overall,this work is an initial exploration to the molecular basis of the heterotrophic protist responding to salinity stressing.The result sheds light on the mechanisms of enhancement of cell protection,reduction of cell activity,and osmotic pressure regulation in ciliates acclimated to salinity.

土壤原生生物的生态功能及其影响因素

【目的】土壤原生生物是指土壤中除植物、动物和真菌以外的所有真核生物,具有明显的系统发育和功能多样性特征,是地下生态系统的关键组成部分之一。与原核生物(细菌与古菌)和真菌相比,原生生物在土壤食物网中的作用常被忽视。本文系统论述了土壤原生生物的多样性及其生态功能,并综述了土壤养分、水分、pH、温度、重金属、微塑料等因子对土壤原生生物的影响,旨在阐明原生生物对土壤养分转化、土壤食物网和植物健康的生态作用及对主要环境因子的响应。【进展】土壤原生生物的数量、大小与形态各异,且营养级类群多样性丰富,它们可作为光合藻类、微生物捕食者、植物与动物的寄生者,在土壤食物网中扮演重要角色。光合型原生生物除潜在提高土壤氧浓度外,对陆地生态系统的碳储存具有重要贡献。消费型原生生物可通过捕食改变微生物群落,推动土壤微生物环,抑制植物病害,并提高植物性能。寄生型原生生物常被认为对宿主具有负面效应,如改变动物多样性,并引起植物病害。然而,寄生型原生生物对推动养分(如磷)循环也有贡献,且对植物的叶际细菌具有生防功能。总的来看,原生生物推动了陆地生态系统物质循环与能量流动向更高营养级的转移,并在土壤食物网中占据中心位置,发挥着关键生态功能。【展望】未来可从原生生物多样性特征及其维持机制、原生生物与其他土壤微生物或动物(如蚯蚓、线虫等)的互作与代谢关系、原生生物对土壤食物网物质循环与能量流动的贡献及相关影响因素进行深入研究。此外,原生生物生防剂的资源开发与应用,将利于缓解土壤与植物农药残留,也对保障土壤健康及其可持续利用与发展具有重要意义。

基于环境RNA研究西太平洋浅水海山区真核微生物多样性及其与细菌的关系

海山遍布大洋海底,由于其特殊海底地形和水文动力环境,孕育了丰富且特殊的生物群落。采用环境RNA技术分析西太平洋M4浅水海山区真核微生物的多样性和分布,并与环境DNA技术检获的结果进行比较,揭示二者的异同。研究发现,RNA和DNA技术检获的表层和DCM层群落结构相似,在200 m以深的水层中群落结构差异较大。共甲藻纲的相对丰度在DNA数据中占比高于RNA数据,因此可能被基于eDNA的技术高估;而甲藻纲和金藻纲则相反,存在被低估的可能性。通过真核微生物与细菌的共现网络,揭示甲藻虽然是海山区叶绿素最大层共现网络中的关键类群,但其与细菌的相互关系弱,且代谢活性较弱。金藻中行混合营养的类群以及Bicoecea类群,在深层海水中普遍存在,且具有较高的代谢活性。环境RNA技术可检获有生命活性的物种分布,为海山区真核微生物多样性及分布提供更完整的认知。

祁连山国家公园青海片区河流和湿地原生生物多样性研究

探索祁连山国家公园河流与湿地的原生生物群落结构特征及其对环境的响应,为片区生物多样性保护与利用提供依据。2020年7-8月对祁连山国家公园青海片区河流和湿地的21个水环境样点进行了水样采集和DNA分离,共获得DNA样品58份,利用宏基因组测序探究祁连山国家公园青海片区的原生生物种类组成和群落结构,并分析了其与环境因子之间的关系。结果显示:(1)共鉴定和注释到393个原生生物分类单元(operational taxonomic units,OTUs),分属于24门40纲95目126科162属,其中裸藻门、纤毛门种类最多,硅藻门、纤毛门丰度最高;(2)片区不同河流或湿地的原生生物群落结构存在显著差异,河流原生生物多样性显著高于湿地;(3)RDA分析显示原生生物群落主要受水体总磷、水温、pH、总有机碳、溶解氧、盐度、总氮、硝酸盐氮、氨氮和水流速度等环境因子的显著影响;(4)物种共现网络分析显示湿地原生生物群落共现网络较河流更稳定。

强还原土壤灭菌对土壤原生生物群落的影响

强还原土壤灭菌(Reductive soil disinfestation,RSD)是一种高效、安全以及环保的土壤灭菌方法。土壤原生生物是土壤微生物的重要组成部分,对土壤养分循环和植物生长起到一定的促进作用。目前关于强还原土壤灭菌对微生物群落影响的研究报道较多,但大都集中于细菌和真菌群落,较少关注原生生物群落。以长期连作番茄土壤为研究对象,设置4种不同RSD处理(对照组、添加玉米秸秆、添加甘蔗渣和添加玉米秸秆+甘蔗渣),RSD步骤为:按照上述4种不同处理添加有机物料,采用淹水和覆膜的方式隔绝空气,并在35℃条件下处理21 d,处理结束后在自然风干的第1、3、7和21天取样,选取第21天的土样进行高通量测序。通过高通量18S rRNA基因扩增子测序技术分析RSD处理后土壤原生生物群落组成和功能群落的变化,利用冗余分析明确影响原生生物群落的关键环境因子。结果表明,在自然风干期间不同RSD处理增加了土壤全碳含量,土壤速效磷含量呈先下降后上升再下降的变化趋势。RSD处理后丝足虫门(Cercozoa)、纤毛门(Cilipohora)以及变形虫门(Amoebozoa)为优势类群,其相对丰度分别为19.2%-25.9%、13.8%-26.9%和12.0%-28.8%。RSD处理提高了捕食型和寄生型原生生物群落的相对丰度,降低了自养型原生生物的相对丰度,并没有改善土壤原生生物群落多样性。土壤速效磷含量和土壤铵态氮含量是影响土壤原生生物群落的关键环境因子,其中土壤速效磷含量与捕食型、自养型和寄生型原生生物功能群落的相对丰度呈现显著相关性。该研究证明了RSD处理对土壤原生生物群落组成和群落功能组成有显著的影响。

胶州湾浮游原生生物时空分布特征--丰度周年变化及与环境因子间的关系

为了解胶州湾浮游原生生物时空分布特征及与环境因子间的关系,自2007年6月-2008年5月,对青岛胶州湾内5个站点表层水的浮游原生生物丰度及环境因子进行了累计24次的周年采样调查及定性、定量分析。结果显示：（1）浮游原生生物周年变动具有2个高峰,分别出现在4月和8月;（2）浮游硅藻、鞭毛藻和纤毛虫的丰度周年变动均为双峰型：春节（4月）高峰、秋节（8月）高峰;（3）浮游原生生物丰度与叶绿素a和溶解氧呈显著性相关,而其群落结构的变化与盐度、溶解氧、硝态氮和亚硝态氮的组合呈显著性相关。本工作为进一步探讨富营养化的内湾型近岸水体内原生生物生态学结构与功能提供了一份必要的基础资讯。

样品保藏方式与时间对海洋底栖细菌及原生生物荧光计数效能的影响

DAPI荧光染色技术已广泛应用于浮游细菌及原生生物的定量研究，但对底栖生物的定量效能尚缺必要的研究。比较了冷冻和冷藏两种保藏方式以及保存时间对DAPI荧光计数底栖细菌、蓝细菌、硅藻、不同粒级自养小鞭毛虫（PNF）和异养小鞭毛虫（HNF）的影响。对黄海冷水固三个站位表层2cm底栖样品进行的4℃冷藏与-20℃冷冻避光保存的比较研究表明，两种保藏方式下两个站位的所有研究对象均无显著差异，但另一站位的PNF（2～5μm和5～10μm）的冷藏保存显著优于冷冻保存。对选取的另外两个站位（0～2cm和2～5cm分层）的样品经1个月和4个月冷藏保存后的分析表明，对于底栖细菌、蓝细菌、PNF（5～10μm）、PNF（〉10gm）、HNF（〉10μm）和硅藻在保存1个月和4个月后的计数没有显著差异，而对于PNF（2～5μm）、HNF（2～5μm1、HNF（5～10μm）保存4个月的数量明显低于保存1个月的样品，如其中一个站位的0～2cm分层的PNF（2～5μm）丰度减少了47．4％，2～5cm分层的丰度减少了59．6％，HNF（2—5gm）和HNF（5～10μm）经4个月后丰度降为0。本研究表明，对底栖细菌、蓝细菌以及原生生物的定量计数可因样品、保藏方式及保存时间的不同而产生差异，因此对于底栖样品短期内宜采用避光、冷藏保存，并在带回实验室后尽快分析。

隐真菌的研究进展

隐真菌门(Cryptomycota)是最近才建立的、隶属于真菌界的一个新的门。本文简要回顾了隐真菌门的来历及建立的依据,介绍了隐真菌的研究进展。系统进化分析显示,隐真菌位于真菌进化树的基部;依据已有的分子序列估计其种类非常丰富,在土壤、海洋与淡水环境中广泛分布。隐真菌细胞壁无几丁质,但其基因组中存在具有肌球蛋白结构域的II型几丁质合成酶基因;生活史相对简单,包括游动孢子、孢囊与孢子囊等阶段;通常在壶菌等真菌细胞内寄生,可通过吞噬作用吸收营养。由于壶菌可侵染浮游植物,因此推测隐真菌可能在水体初级生产及碎屑食物网中发挥调节作用。最后,对有关隐真菌的分子系统、分离与培养、基因组、多样性及分子生态学研究进行展望。

桑沟湾养殖生态系统微食物环对长牡蛎(Crassostrea gigas)碳需求的贡献

采用海域大规模调查和模拟现场流水法测定了桑沟湾海域微食物环主要组分生物(微微型浮游生物、微型鞭毛虫和纤毛虫)在桑沟湾的季节分布和对长牡蛎食物来源的贡献。对桑沟湾海域浮游生物现存量的调查结果显示:微食物环生物丰度和生物量以冬季最低(P<0.05)。微食物环组成生物的生物量以微型鞭毛虫最大,占51.69%(无色素体微型鞭毛虫HNF贡献37.31%,有色素体微型鞭毛虫PNF贡献14.38%),其次是异养细菌(39.03%),纤毛虫和微微型真核浮游生物贡献较小,分别为2.31%和0.66%。使用模拟现场流水法,测定了长牡蛎对浮游生物的摄食,其清滤率变化范围为0.26-3.50L/(g·h),随着粒径的增大,长牡蛎对浮游生物的清滤率增加。长牡蛎对不同浮游生物的清滤率由大到小依次为:2μm以上有色素体浮游生物>纤毛虫>2μm以下有色素体浮游生物>无色素体微型鞭毛虫>异养细菌,长牡蛎对2μm以上有色素体浮游生物碳截留最大(289.20±62.36μg/(g·h)),其次是无色素体微型鞭毛虫,异养细菌和纤毛虫。传统的对于贝类食物来源的测定忽略了异养细菌、HNF以及纤毛虫,对微食物环框架的研究得出三种生物对长牡蛎的碳贡献为1563.58μg/(g·d)(17.94%),指示原生动物(异养鞭毛虫和纤毛虫)在长牡蛎的食谱组成中的地位不可忽视。异养细菌除了参与微食物环,还能被长牡蛎直接或者间接的摄食,成为长牡蛎的食物来源之一。本文结果为长牡蛎的养殖容量评估和微食物环生物对养殖生态系统的贡献分析提供了重要的数据支撑。

亚高山草地土壤原生生物群落结构和多样性海拔分布格局

生物多样性分布格局与维持机制即群落构建机制,是群落生态学研究的热点领域。微生物生态学中的一个关键问题是量化确定性过程和随机过程对微生物群落构建的相对贡献。尽管原生生物是土壤微生物群落中重要的组成部分,在微生物食物链中扮演着关键角色,但与细菌和真菌相比,目前对原生生物群落构建机制知之甚少。运用Illumina Miseq高通量测序技术,分析了五台山亚高山草地生态系统(海拔2000—3061 m范围内)土壤原生生物群落组成和多样性维持机制。结果表明,四个海拔梯度的土壤共获得有效序列520673条,分属于8个超群、24个门、65个纲、125个目、222个科和350个属。门水平上,丝足虫门(Cercozoa)、褐藻门(Ochrophyta)、纤毛门(Ciliophora)和顶复门(Apicomplexa)为主要优势类群。LEfSe分析显示,17个生物标志物对海拔梯度非常敏感,不同海拔梯度富集了不同的原生生物种群。尽管海拔对土壤原生生物群落的α多样性没有显著影响,但非度量多维尺度分析(NMDS)和相似性分析(ANOSIM)结果表明,原生生物群落组成和结构在海拔梯度上存在显著的差异(P<0.05)。冗余分析(RDA)显示海拔、土壤含水量、总氮和植物丰富度指数与原生生物群落结构存在显著相关性(P<0.05)。方差分解分析(VPA)和偏Mantel分析表明环境因子和空间变量对原生生物群落海拔分布格局均有显著影响,但是环境因子的相对作用(7.9%)明显大于空间变量(1.8%)。土壤原生生物群落之间的Bray⁃Curtis距离与海拔距离呈显著正相关关系(P<0.05),说明选择过程可能是亚高山草地土壤原生生物群落分布格局的主要驱动因素。零模型分析进一步证实了确定性过程在原生生物群落构建中的相对作用大于随机过程。总之,五台山亚高山草地土壤原生生物群落组成和结构沿海拔梯度具有显著的变化格局,群落构建主要由确定性过程和随机过程驱动,但确定性过程占主导地位。