Pronounced temporal changes in soil microbial community and nitrogen transformation caused by benzalkonium chloride

As one typical cationic disinfectant, quaternary ammonium compounds (QACs) were approved for surface disinfection in the coronavirus disease 2019 pandemic and then unintentionally or intentionally released into the surrounding environment. Concerningly, it is still unclear how the soil microbial community succession happens and the nitrogen (N) cycling processes alter when exposed to QACs. In this study, one common QAC (benzalkonium chloride (BAC) was selected as the target contaminant, and its effects on the temporal changes in soil microbial community structure and nitrogen transformation processes were determined by qPCR and 16S rRNA sequencing-based methods. The results showed that the aerobic microbial degradation of BAC in the two different soils followed first-order kinetics with a half-life (4.92 vs. 17.33 days) highly dependent on the properties of the soil. BAC activated the abundance of N fixation gene (nifH) and nitrification genes (AOA and AOB) in the soil and inhibited that of denitrification gene (narG). BAC exposure resulted in the decrease of the alpha diversity of soil microbial community and the enrichment of Crenarchaeota and Proteobacteria. This study demonstrates that BAC degradation is accompanied by changes in soil microbial community structure and N transformation capacity.     

三峡水库开县消落区水域冬季蓄水期间藻类群落结构与水质评价

2008年12月三峡水库第一次试验性蓄水至172.8 m后,开县老县城区域被淹没呈水库特征,对蓄水后开县消落区水域水生生物生态及水体营养状态的研究目前还鲜见报道.为了解172.8 m水位后开县消落区水域水环境的现状及藻类群落结构的变化,于2009年1月和2009年12月冬季蓄水期间2次对包括汉丰湖在内的开县消落区水域4个样点藻类组成、数量和生物量的分布及变化情况进行了跟踪观测,初步分析了浮游植物种群结构的变化趋势,并从生物角度评估了水域的水质营养状况.结果表明,2次采样共鉴定出浮游植物6门37属69种(含变种),优势种群均为甲藻和隐藻,2009年12月藻类细胞密度和生物量低于2009年1月.藻类种群结构和污染指示种评价结果显示,冬季蓄水期间开县消落区各采样断面的营养水平属于中-富营养类型.多样性分析的结果表明开县消落区水域冬季蓄水期间处于中污染状态.     

Microbial diversity accumulates in a downstream direction in the Three Gorges Reservoir

Organic and inorganic materials migrate downstream and have important roles in regulating environmental health in the river networks. However, it remains unclear whether and how a mixture of materials (i.e., microbial species) from various upstream habitats contribute to microbial community coalescence upstream of a dam. Here we track the spatial variation in microbial abundance and diversity in the Three Gorges Reservoir based on quantitative PCR and 16S rRNA gene high-throughput sequencing data. We further quantitatively assess the relative contributions of microbial species from mainstem, its tributaries, and the surrounding riverbank soils to the area immediately upstream of the Three Gorges Dam (TGD). We found an increase of microbial diversity and the convergent microbial distribution pattern in areas immediately upstream of TGD, suggesting this area become a new confluence for microbial diversity immigrating from upstream. Indeed, the number of shared species increased from upstream to TGD but unique species decreased, indicating immigration of various sources of microbial species overwhelms local environmental conditions in structuring microbial community close to TGD. By quantifying the sources of microbial species close to TGD, we found little contribution from soils as compared to tributaries, especially for sites closer to TGD, suggesting tributary microbes have greater influence on microbial diversity and environmental health in the Three Gorges Reservoir. Collectively, our results suggest that tracking microbial geographic origin and evaluating accumulating effects of microbial diversity shed light on the ecological processes in microbial communities and provide information for regulating aquatic ecological health.     

洪泽湖浮游动物时空分布特征及其驱动因素

洪泽湖是我国第四大淡水湖,承担着周边的工农业用水以及为人类提供渔业资源等重要功能.研究洪泽湖浮游动物群落结构变化可为洪泽湖生态环境的科学管理提供理论依据.通过2017年3月至2018年2月的逐月调查数据,结合洪泽湖浮游动物的种类组成、密度和生物量的时空变化,以及群落多样性和优势种的季节变化特征,并运用典范对应分析等方法探讨了洪泽湖浮游动物的时空变化与环境因子的相互关系.群落结构分析表明,洪泽湖浮游动物年均密度为383.87 ind·L^-1,年均生物量为1.36 mg·L^-1.洪泽湖浮游动物群落结构时空变化较大,时间上夏季浮游动物群落结构波动较大,秋季浮游动物密度与生物量均达到最大值,冬季浮游动物群落结构最为简单;空间上成子湖和溧河洼浮游动物较为丰富,差异较小,过水区浮游动物较少且变化较大.典范对应分析表明,洪泽湖浮游动物群落结构的时空变化与水位、总磷、水温和总氮等因素显著相关.不同时间浮游动物群落结构变化的主导因素不同,夏季主导因素是水位与水温;秋冬季主导因素是水温、营养盐及叶绿素等.不同湖区点位集中程度不同,过水区分布的更为分散,浮游动物群落结构差异较大,成子湖和溧河洼分布的相对集中,浮游动物群落结构差异较小.水位波动对浮游动物群落结构的变化影响最大,表现在水位波动会直接影响浮游动物群落结构,同时也会通过影响水质而间接影响浮游动物群落结构.     

北海湖微生物群落结构随季节变化特征

分别于夏季、秋季、冬季和春季采集北海湖水样,进行水质和微生物群落结构分析.水质分析表明,夏季和秋季的水质较冬季和春季差,其中TN和TP是影响水质的最重要因素.通过Mi Seq高通量测序分析微生物群落结构表明:蓝细菌门(Cyanobacteria)、变形菌门(Proteobacteria)、放线菌门(Actinobacteria)和拟杆菌门(Bacteroidetes)是湖水中的优势门,但在不同季节的分布不同.夏季和秋季微生物的多样性高,蓝细菌门(Cyanobacteria)是第一优势菌门(32.7%~43.2%),其中聚球藻属(Synechococcus)是优势蓝细菌.冬季变形菌门(Proteobacteria)的含量相对丰富,占细菌群落的34.8%~40.4%.而春季,放线菌门(Actinobacteria)和拟杆菌门(Bacteroidetes)的含量增加,两者之和占细菌群落的51.5%~64.3%.RDA(redundancy analysis)分析表明,水温是影响北海湖微生物群落结构的最主要环境因子.总体而言,北海湖水质符合景观水的标准,但夏季聚球藻属(Synechococcus)的大量繁殖使北海湖发生水华的风险增加,因此要加强对北海湖水质检测和管理.     

Distribution of bacterial communities across plateau freshwater lake and upslope soils

Microorganisms are involved in a variety of biogeochemical processes in natural environments. The differences between bacterial communities in freshwaters and upslope soils remain unclear. The present study investigated the bacterial distribution in a plateau freshwater lake, Erhai Lake (southwestern China), and its upslope soils. Illumina MiSeq sequencing illustrated high bacterial diversity in lake sediments and soils. Sediment and soil bacterial communities were mainly composed of Proteobacteria, Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi and Planctomycetes. However, a distinctive difference in bacterial community structure was found between soil and sediment ecosystems. Water content, nitrogen and pH affected the distribution of the bacterial community across Erhai Lake and its upslope soils. Moreover, the soil bacterial community might also be shaped by plant types. This work could provide some new insights into plateau aquatic and terrestrial microbial ecology.     

云贵高原富营养化湖泊杞麓湖浮游生物群落的季节性演替及其驱动因子分析

杞麓湖是云贵高原典型的重富营养化湖泊,水生态系统已严重退化.为揭示杞麓湖浮游生物群落季节性演替规律,阐明浮游生物群落季节性演替的驱动因子,于2017-2018年对杞麓湖浮游生物及水质理化参数进行季节采样调查和浮游生物群落结构特征分析,并运用CCA（典范对应分析）方法分析浮游植物群落组成与环境因子的关系.结果表明:①杞麓湖夏季营养状态最高,达重度富营养水平,春秋冬三季均为中度富营养.水体SD（透明度）春季最高,夏季最低;ρ（Chla）、ρ（COD_Mn）均为夏季最高,冬季最低;ρ（TN）冬季最高,秋季最低;ρ（TP）春夏最高,冬季最低.②杞麓湖浮游植物共6门163种（其中包括8个变种）.浮游植物密度春季最低（0.66×108 L-1）而秋季最高（16.08×108 L-1）,主要为蓝藻门、绿藻门和硅藻门.其中,春季优势种为微细转板藻（Mougeotia parvula）;夏季优势种为孟氏浮丝藻（Planktothrix mougeotii）;秋冬季的优势种均为阿氏浮丝藻（Planktothrix agardhii）.③杞麓湖浮游动物32种,浮游动物密度冬季最低（13.2 ind./L）而夏季最高（3 696.0 ind./L）.其中,春季优势种为曲腿龟甲轮虫（Keratella valga）,夏季优势种为前节晶囊轮虫（Asplanchna priodonta）,秋季优势种为螺形龟甲轮虫（Keratella cochlearis）,而冬季优势种为桡足类幼体.研究显示,杞麓湖浮游动植物群落季节性演替明显,ρ（DTP）（DTP为溶解态磷）、ρ（TP）、ρ（NH₃-N）、ρ（COD_Mn）和WT（水温）是影响杞麓湖浮游植物群落季节性演替的主要驱动因子.      

温带季节性分层水库浮游植物功能类群的时空演替

为探究我国北方温带季节性分层水库浮游植物群落结构的时空演替特性,于2014年7月~2015年6月对山东枣庄市水源水库周村水库进行每月2次的分层采样分析,采用Renolyds和Padisák等提出的功能类群划分方法对水库浮游植物群落进行分类,并结合水库水文、水质,分析优势功能类群时空演替规律及其主要环境影响因子.结果表明:周村水库共检出浮游植物112种,隶属于7门63属,可划分为18个功能群类.周村水库浮游植物功能类群演替具有明显的季节性分布特性:其中夏秋季热分层期主要以鞘丝藻(Lyngbya sp.)、螺旋藻属(Spirulina sp.)等丝状蓝藻为代表的S₁功能类群占优势,而冬季混合期以梅尼小环藻(Cyclotella meneghiniana)、针杆藻(Synedra sp.)等能适应低温、弱光的C+D功能类群为优势群落;浮游植物功能类群分布在垂向上并无较大差异.冗余分析(RDA)显示:热分层、降雨量和水温是影响浮游植物功能类群时空演替的主要环境因子.     

红枫湖季节性热分层消亡期水体的理化特征

以云贵高原典型的人工河道型水库红枫湖为研究对象,对近2年来4个代表性湖区季节性热分层消亡期水体的理化特征进行了原位监测. 结果表明:红枫湖水体季节性热分层历经发生、发展和消亡的周期性演化过程,对湖泊水环境的变化起着重要的控制作用. 秋季初期,气温骤降易于引起季节性热分层的突发性消亡,表现为水体垂向混匀. 以2010年为例,分层消失使得上层水温由28.6 ℃降至23.0 ℃,ρ(DO)(溶解氧浓度)由9.6 mg/L降至4.0 mg/L,pH由8.8降至7.9,电导率由0.32 mS/cm升至0.36 mS/cm,局部湖区出现鱼类死亡现象;短时间内的剧烈垂直混合,致使沉积物营养盐扰动释放,上部水体ρ(TP)增加了约0.01 mg/L,ρ(TN)增加了0.1 mg/L. 红枫湖水体垂向混合可对湖泊水环境产生重要影响,其影响的水体深度和环境效应一方面与气温变幅等因素有关,另一方面还受湖泊温跃层位置和底层水体的绝对温度等因素控制,在预测该类突发性水质恶化事件及评估其环境影响时需予以考虑.      

Seasonal variations of soil bacterial communities in Suaeda wetland of Shuangtaizi River estuary, Northeast China

Estuarine wetland is the transitional interface linking terrestrial with marine ecosystems, and wetland microbes are crucial to the biogeochemical cycles of nutrients. The soil samples were collected in four seasons (spring, S1; summer, S2; autumn, S3; and winter, S4) from Suaeda wetland of Shuangtaizi River estuary, Northeast China, and the variations of bacterial community were evaluated by high-throughput sequencing. Soil properties presented a significant seasonal change, including pH, carbon (C) and total nitrogen (TN), and the microbial diversity, richness and structure also differed with seasons. Canonical correspondence analysis (CCA) and Mantel tests implied that soil pH, C and TN were the key factors structuring the microbial community. Gillisia (belonging to Bacteroidetes) and Woeseia (affiliating with Gammaproteobacteria) were the two primary components in the rhizosphere soils, displaying opposite variations with seasons. Based on PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) prediction, the xenobiotics biodegradation related genes exhibited a seasonal decline, while the majority of biomarker genes involved in nitrogen cycle showed an ascending trend. These findings could advance the understanding of rhizosphere microbiota of Suaeda in estuarine wetland.     

人工湿地空气微生物群落碳源代谢特征

采用BIOLOG-GN微平板分析自由表面流人工湿地空气微生物群落碳源代谢特征,阐明空气微生物群落代谢功能与环境因子相关性.结果表明,不同季节人工湿地空气微生物AWCD值、优势群落及Mc Intosh指数均存在差异,春季和夏季空气微生物碳源代谢强度明显高于秋季和冬季(P0.01);4个季节人工湿地空气微生物优势群落依次为羧酸类代谢群落、糖类代谢群落、聚合物类代谢群落和羧酸类代谢群落,夏季空气微生物对6类化合物的利用水平高于其他季节(P0.05).主成分分析显示,秋季和冬季空气微生物碳源代谢特征相似,但与春季和夏季差别较大,胺类是区分人工湿地夏季与春季、秋季和冬季的主要碳源类型,羧酸类是区分春季与秋季和冬季空气微生物代谢差异的主要碳源类型.不同季节人工湿地空气微生物群落结构主导影响因子存在差异.     

Investigation of low-molecular weight organic acids and their spatiotemporal variation characteristics in Hongfeng Lake, China

The identities and concentrations of low-molecular-weight organic acids (LMWOAs) were determined by ion chromatography throughout a 20-m water column in Hongfeng Lake, China. The spatiotemporal variations of LMWOAs and their contributions to dissolved organic matter (DOM) in a research period of 24 hr were also investigated. The results demonstrated that five LMWOAs (lactic, acetic, pyruvic, sorbic, oxalic acid) were detected, and their total concentration and proportion in DOC were 6.55 μmol/L and 7.47%. Their average levels were 2.50, 0.65, 2.35, 0.96 and 0.09 μmol/L, respectively. LMWOAs were higher during daytime (10:00-18:00 on Jun 13, 2008) than nighttime (21:00-6:00 the next morning), in particular 4.99 μmol/L high in the epilimnion ( 1 m water depth), reflecting the fact that direct import from terrigenous sources and photochemical production from humic materials were dominant during LMWOAs’ origin and accumulation. The same factors caused LMWOAs to be 0.63 μmol/L in the epilimnion higher than in the hypolimnion. The rapid decrease of total organic acid (TOA) up until 18:00 mainly resulted from bio-uptake and mineralization in the hypolimnion (>1 m water depth). Pyruvic acid increased with time in the epilimnion and decreased in the hypolimnion, largely related to the two contrary processes of continuous degradation and synthesis of macromolecular organic matter during life materials’ cycle mediated by organisms. Simultaneously, plankton behavior and thermal stratification played a pivotal role in LMWOAs’ behavior in the water column, causing decreasing and increasing profiles. The distribution of LMWOAs represents an interesting resource for biogeochemical research of DOM in aquatic ecosystems.     

石油污染对场地中细菌群落的影响及其反馈机制

石油污染场地细菌群落的组成与分布差异性较大,且受多种因素影响.石油污染过程如何驱动场地中细菌群落变化仍然不明确,石油污染场地的细菌群落组装过程仍待研究.为了探明石油污染场地细菌群落结构及其与污染物之间的关系,以甘肃省某石化场地为研究区域,调查了油泥、石油污染土壤、未污染土壤及受污染含水层中沉积物的石油浓度、细菌群落结构多样性及其群落组装过程.结果表明:在好氧环境下,高石油浓度的油泥环境可以选择出具有降解石油能力的基因型（alkB基因和nah基因）,油泥环境中好氧降解基因拷贝数高达107 copies/g;而在含水层沉积物等厌氧环境下,好氧降解石油的基因拷贝数仅为106 copies/g,ass和bamA等厌氧降解基因也没有在厌氧环境中得到高效表达.石油污染土壤后,细菌群落的α-多样性降低,且与石油浓度呈显著负相关（P < 0.05）.与未污染土壤相比,油泥和受污染沉积物中细菌群落α-多样性降低了50%左右,而石油污染土壤中细菌群落的α-多样性降低了大约33%.在油泥、石油污染土壤和未污染土壤等地表环境中,群落组装主要受多样化和漂变等随机性过程主导,而与污染程度无关.在受污染含水层沉积物等厌氧环境中,微生物的群落组装主要受环境选择、种间竞争等确定性过程主导.研究显示,石油污染场地中的细菌群落多样性主要受石油浓度驱动,但是其对环境的反馈,例如降解基因的选择、群落组装过程等则需要较高的石油浓度才有所显示.      

沉水植物对沉积物微生物群落结构影响:以洪泽湖湿地为例

应用磷脂脂肪酸(PLFA)方法分析洪泽湖湿地典型沉水植物菹草群丛、蓖齿眼子菜群丛、菹-蓖混丛对其根系沉积物微生物群落结构的影响,以期了解沉水植物种类以及在不同生长时期对沉积物微生物群落结构的影响规律.结果表明,植物群丛根系沉积物PLFA总量在不同的时期发生了明显的变化,而同一时期的不同群丛PLFA总量差异不显著.沉积物微生物群落结构受沉水植物根系影响,菹草群丛中G~+/G~-(革兰氏阳性菌/革兰氏阴性菌)在3个不同生长时期比值为0.74、1.35、1.26,蓖齿眼子菜群丛G~+/G~-比值为0.89、0.98、1.49,菹-蓖混合群丛G~+/G~-比值为0.95、1.39、1.35,其G~+/G~-的变化和植物根系生长有密切关系.沉积物微生物群落结构受环境因子的影响,环境因子如T、p H、TOC、DO等与沉积物PLFA中特征磷脂存在相关性.     

Molecular characterization of methanogenic microbial communities for degrading various types of polycyclic aromatic hydrocarbon

Knowledge on methanogenic microbial communities associated with the degradation of polycyclic aromatic hydrocarbons (PAHs) is crucial to developing strategies for PAHs bioremediation. In this study, the linkage between the type of PAHs and microbial community structure was fully investigated through 16S rRNA gene sequencing on four PAH-degrading cultures. Putative degradation products were also detected. Our results indicated that naphthalene (Nap)/2-methylnaphthalene (2-Nap), phenanthrene (Phe) and anthracene (Ant) sculpted different microbial communities. Among them, Nap and 2-Nap selected for similar degrading bacteria (i.e., Alicycliphilus and Thauera) and methanogens (Methanomethylovorans and Methanobacterium). Nap and 2-Nap were probably activated via carboxylation, producing 2-naphthoic acid. In contrast, Phe and Ant shaped different bacterial and archaeal communities, with Arcobacter and Acinetobacter being Phe-degraders and Thiobacillus Ant-degrader. Methanogenic archaea Methanobacterium and Methanomethylovorans predominated Phe-degrading and Ant-degrading culture, respectively. These findings can improve our understanding of natural PAHs attenuation and provide some guidance for PAHs bioremediation in methanogenic environment.     

青藏高原克鲁克-托素湖湿地系统微生物多样性

克鲁克湖(Keluke Lake)和托素湖(Tuosu Lake)是青藏高原重要的湿地和水禽自然保护区,其水体微生物的多样性有待研究。利用Illumina测序平台进行16S rRNA基因(V3-V4区)高通量测序,并分析两湖水体微生物的群落结构和多样性。结果表明淡水克鲁克湖和咸水托素湖的物种注释OTU数目分别为331和148,获得克鲁克湖的已知细菌种类为16门34纲66属;托素湖为9门19纲54属。克鲁克湖的微生物优势类群以变形菌门(Proteobacteria)为主,次为蓝菌门(Cyanobacteria)和拟杆菌门(Bacteroidetes),其优势种群是未确定种属的蓝细菌、弓形杆菌属(Arcobacter)和盐单胞菌属(Halomonas)。托素湖的优势类群以变形菌门为主,次为厚壁菌门(Firmicutes),优势种群是盐单胞菌属。克鲁克湖的微生物物种丰富度、多样性和分布均匀度均显著高于咸水托素湖,但托素湖的物种优势度明显高于克鲁克湖。两湖优势微生物的属群分布与环境因子存在明显的正相关,此为高原湿地生态系统的环境监测与保护提供参考依据。     

南四湖浮游硅藻季节性演替及其与环境因子的相关性

为研究南水北调东线工程调水对南四湖硅藻藻密度、种群结构变化的影响,于2010年5月—2013年4月在南四湖进行逐月采样,应用NMDS(non-metric multi-dimensional scaling,非度量性多元标度)分析硅藻种群组成的相似性,并通过冗余分析和Pearson相关性分析研究了硅藻种群结构和环境因子间的相关性. 结果表明:①共检出硅藻23属69种,硅藻藻密度在14.3×104~663.2×104 L-1之间,呈明显的季节性变化,表现为冬春季大于夏秋季;②硅藻种群演替呈明显的季节性变化,冬春季主要以冷水种尖针杆藻(冬春季所占比例分别为15.3%、24.0%)为主,夏秋季则以暖水种扭曲小环藻(夏秋季所占比例分别为17.8%、19.1%)为主;③氮磷营养盐水平、pH和表层水温是影响南四湖硅藻种群变化的主要环境因子. 南四湖硅藻种群对于环境因子变化的反应较为灵敏,可作为南四湖水质的潜在指示工具进行长期研究.      

黄土高原六道沟流域8种植物根际细菌与AMF群落多样性研究

采用末端限制性片段长度多态性(terminal restriction fragment length polymorphism,T-RFLP)方法,研究了神木县六道沟流域8种植物根际细菌与丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)群落多样性及其相互关系.目的是获得有关植物根际细菌和AMF群落的多样性指数,为生态环境修复提供科学依据.结果表明,8种植物根际细菌和AMF的种类和数量有较大差异,其中刺槐根际细菌的Shannon指数最高(4.01),垂柳最低(2.18),根际AMF的Shannon指数最高为小叶杨(2.07),最低为沙棘(1.21);聚类分析(cluster analysis)和冗余分析(redundancy analysis)结果表明,不同植物根际细菌和AMF的群落结构有较大差异,但同时部分植物间也存在相似性;8种植物根际细菌和AMF的多样性指数总体呈极显著的正相关(P<0.01);冗余分析结果表明在根际土壤环境因子中,对根际微生物群落多样性影响最大的环境因子为有机质含量.植物种类和根际环境对根际微生物群落结构有较大影响,同时,刺槐的根际细菌和AMF群落多样性指数均较高,故可作为六道沟流域植被恢复的先锋树种.     

污水处理系统微生物群落时空分布和构建机制研究进展

探索微生物群落时空分布和构建机制一直是环境微生物生态学研究的目标和挑战。近年来,微生物生态学规律和理论逐渐在工程系统中得到应用,分类群-面积关系、分类群-时间关系和距离-衰减效应等规律已在污水处理系统的微生物群落分布中得到验证。随着研究的发展,微生物时空分布研究已从群落分布规律的发现和描述,拓展到驱动群落分布的因素,即群落构建机制的探索。介绍了污水处理系统微生物群落时空分布规律和构建机制的研究进展,并对未来的方向进行了展望,强调了将生态理论和工程实践相结合的重要性。未来应在污水处理系统核心微生物研究、微生物群落的生物多样性、构建机制与污水处理性能的关联、多组学技术在微生物时空分布和构建机制研究中的应用等方面有所突破。     

青海湖硅藻组合及其季节变化——来自沉积物捕获器的初步研究

通过对青海湖捕获器中2010年7月至2011年10月份沉积物样品与青海湖湖岸7个地点表层样品的分析,获得青海湖现代硅藻组合及季节变化特征。捕获器沉积物样品中共鉴定出硅藻2纲32属56种,主要为咸水种与微咸水种。其中,优势种为Berkeleya rutilans、Cocconeis placentula var. euglypta、Cyclotella choctawhatcheeana和Nitzschia inconspicua,此四种占总数的82%以上。硅藻组合变化具显著的季节性差异,冬季主要以浮游种Cyclotella choctawhatcheeana占优势;非冰封期则以附生种Berkeleya rutilans、Nitzschia inconspicua与Cocconeis placentula var. euglypta占优势。青海湖湖水具有高碱度,硅藻的保存率不高,其保存率具有夏季高、冬季低的季节性变化,但这不是造成硅藻组合显著季节性变化的主要原因,其季节性变化主要取决于水生植物的生长与湖区冰情。