Anaerobic methane oxidation potential and bacteria in freshwater lakes: Seasonal changes and the influence of trophic status

Nitrite-dependent anaerobic methane oxidation (n-damo), mainly carried out by n-damo bacteria, is an important pathway for mitigating methane emission from freshwater lakes. Although n-damo bacteria have been detected in a variety of freshwater lakes, their potential and distribution, and associated environmental factors, remain unclear. Therefore, the current study investigated the potential and distribution of anaerobic methanotrophs in sediments from Erhai Lake and Dianchi Lake, two adjacent freshwater lakes in the Yunnan Plateau with different trophic status. Both lakes showed active anaerobic methane oxidation potential and harbored a high density of n-damo bacteria. Based on the n-damo pmoA gene, sediment n-damo bacterial communities mainly consisted of Candidatus Methylomirabils oxyfera and Candidatus Methylomirabils sinica, as well as novel n-damo organisms. Sediment anaerobic methane oxidation potential and the n-damo bacterial community showed notable differences among seasons and between lakes. The environmental variables associated with lake trophic status (e.g. total nitrogen, ammonia nitrogen, nitrate nitrogen, and total organic carbon) might have significant impacts on the anaerobic methane oxidation potential, as well as the abundance and community structure of n-damo bacteria. Therefore, trophic status could determine the n-damo process in freshwater lake sediment.     

Flavobacteria blooms in four eutrophic lakes: linking population dynamics of freshwater bacterioplankton to resource availability

Heterotrophic bacteria are major contributors to biogeochemical cycles and influence water quality. Still, the lack of representative isolates and the few quantitative surveys leave the ecological role and significance of single bacterial populations to be revealed. Here we analyzed the diversity and dynamics of freshwater Flavobacteria populations in four eutrophic temperate lakes. From each lake, clone libraries were constructed using primers specific for either the class Flavobacteria or Bacteria. Sequencing of 194 Flavobacteria clones from 8 libraries revealed a diverse freshwater Flavobacteria community and distinct differences among lakes. Abundance and seasonal dynamics of Flavobacteria were assessed by quantitative PCR with class-specific primers. In parallel, the dynamics of individual populations within the Flavobacteria community were assessed with terminal restriction fragment length polymorphism analysis using identical primers. The contribution of Flavobacteria to the total bacterioplankton community ranged from 0.4 to almost 100% (average, 24%). Blooms where Flavobacteria represented more than 30% of the bacterioplankton were observed at different times in the four lakes. In general, high proportions of Flavobacteria appeared during episodes of high bacterial production. Phylogenetic analyses combined with Flavobacteria community fingerprints suggested dominance of two Flavobacteria lineages. Both drastic alterations in total Flavobacteria and in community composition of this class significantly correlated with bacterial production, emphasizing that resource availability is an important driver of heterotrophic bacterial succession in eutrophic lakes.     

Characterization of aerobic heterotrophic bacteria in cold and nutrient-poor freshwater ecosystems

Aerobic heterotrophic bacteria present in the surface water of three cold and nutrient-poor lakes in the Chilean Patagonia (Alto Reino, Las Dos Torres and Venus) were analysed for genetic similarity and metabolic diversity using 16S ribosomal DNA and the Biolog EcoPlate^TM system, respectively. Bacterial fingerprints of water samples in enriched and non-enriched nutrient broth demonstrated a >50% fingerprinting similarity between the lakes. Metabolic activity was also similar. However, the Biolog EcoPlate^TM system carbon substrates revealed functional diversity. Lake Las Dos Torres showed the most fingerprinting similarity between enriched and non-enriched cold water samples. The amounts of living and viable bacteria were also higher in this lake’s water sample, suggesting a predominance of facultative oligotrophic groups. DNA sequencing analysis demonstrated the presence of phylum Bacteroidetes in Lake Alto Reino; phyla Bacteroidetes and Gammaproteobacteria in Lake Las Dos Torres; and phyla Bacteroidetes, Alphaproteobacteria, and Gammaproteobacteria in Lake Venus. Although each lake had a unique bacterial community structure, the different bacterial groups may be performing similar metabolic functions, given the similarity in extreme environmental conditions.     

乌梁素海富营养化湖区浮游细菌多样性及系统发育分析

水生生态系统富营养化与细菌群落之间的关系尚不明确。本文通过构建和分析16S rRNA基因片段克隆文库, 以期揭示乌梁素海富营养化水体细菌的多样性及其系统发育关系, 并探讨富营养化与细菌多样性之间的关系。利用Hae III对文库中的87个克隆子进行单酶切, 产生了23种带型, 文库覆盖度达到了73.6%, 反映出文库有较好的代表性。选择每种OTU的一个代表克隆进行测序分析, 基因序列系统发育分析结果表明, 乌梁素海中多数细菌与淡水生态系统中常见的细菌门类相同, 即α-, β-, γ-Proteobacteria, Bacteroidetes, Actinobacteria, 它们分别占总菌数的10.3%、41.4%、4.6%和6.9%, 其中β-Proteobacteria和Bacteroidetes是优势细菌类群。与典型淡水生态系统细菌群落组成不同的是, 乌梁素海中存在约10.3%的轻度嗜盐碱细菌。水体中83.9%的细菌与已培养的细菌的同源性低于97%, 其中58.9%的细菌未能鉴定到属; 其余总菌数16.1%的克隆与具有降解污染物生物活性的已知菌相近。Bacteroidetes、Firmicutes和β-Proteobacteria中的某些类群成为优势菌群可能是对乌梁素海水体富营养化的响应。     

Molecular Detection of Novel Anammox Bacterial Clusters in the Sediments of the Shallow Freshwater Lake Taihu

Previous studies have demonstrated the wide occurrence of anaerobic ammonium oxidizing (anammox) bacteria; however, there is very limited information on the distribution of these bacteria in freshwater habitats. In this study, the anammox bacterial communities were detected by molecular analysis targeting the 16S rRNA genes in the sediments of Lake Taihu, a large and shallow eutrophic freshwater lake in China. The recovery of specific 16S rRNA sequences with two stable monophyletic clusters indicated that anammox bacteria were present in Lake Taihu. A phylogenetic analysis indicated that these two groups represent two novel lineages within the first subgroup of anammox bacteria, independent of the treeing methods. High intra-lake variability in anammox bacterial diversity and community composition was observed, in particular, based on a 1% cut-off of 16S rRNA sequence variation. The spatial variability was largely related to the substrate availability, which was denoted by the correlations between the relative abundance of the two Taihu anammox bacterial groups and the concentrations of ammonium and nitrite. This indicates that the niche differentiation of anammox bacteria is linked to the environmental heterogeneity. These findings suggest that the freshwater lakes may accommodate different anammox bacterial communities and, thus, expand our knowledge on the diversity and distribution of anammox bacteria. Supplemental materials are available for this article. Go to the publisher's online edition of Geomicrobiology Journal to view the free supplemental files.     

Bacterial Community of the Largest Oligosaline Lake,Namco on the Tibetan Plateau

Bacterial abundances and diversity in the surface water of Lake Namco, the largest oligosaline lake on the Tibetan Plateau, were examined using flow cytometry approach and constructing 16S rRNA gene clone libraries. Bacterial abundances were from 0.08 × 10⁶ to 1.6 × 10⁶ cells mL^?1, and were in the reported range of other lakes of the Tibetan Plateau and high mountain regions. Bacterial abundances were significantly correlated with the concentrations of chlorophyll a (chl a), but showed no significant relationship with the dissolved organic carbon (DOC), which suggested that the amount of DOC released by algae was the key factor determining the bacterial abundance rather than the total DOC. The total trace elements concentrations also obviously connected with bacterial abundances, and 9 of 20 elements showed significant relationship. Bacterial 16S rRNA gene clone sequences were affiliated to the α-, β-, γ-, δ-, and ?-Proteobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria, Firmicutes, Acidobacteria, Planctomycetes, Verrucomicrobia, Candidate division OD1, or unclassified, and among these the β-Proteobacteria dominated. Bacteria in Lake Namco were most closely related to those retrieved from freshwater habitats. Relatively few sequences were closely related to those recovered from saline habitats. Eleven of 34 typical freshwater bacterial clusters were detected in the oligosaline Lake Namco. Bacterial diversity within the lake varied and was connected with the concentrations of DOC and chl a.     

Patterns in Benthic Biodiversity Link Lake Trophic Status to Structure and Potential Function of Three Large,Deep Lakes

Relative to their scarcity, large, deep lakes support a large proportion of the world’s freshwater species. This biodiversity is threatened by human development and is in need of conservation. Direct comparison of biodiversity is the basis of biological monitoring for conservation but is difficult to conduct between large, insular ecosystems. The objective of our study was to conduct such a comparison of benthic biodiversity between three of the world’s largest lakes: Lake Tahoe, USA; Lake Hövsgöl, Mongolia; and Crater Lake, USA. We examined biodiversity of common benthic organism, the non-biting midges (Chironomidae) and determined lake trophic status using chironomid-based lake typology, tested whether community structure was similar between the three lakes despite geographic distance; and tested whether chironomid diversity would show significant variation within and between lakes. Typology analysis indicated that Lake Hövsgöl was ultra-oligotrophic, Crater Lake was oligotrophic, and Lake Tahoe was borderline oligotrophic/mesotrophic. These results were similar to traditional pelagic measures of lake trophic status for Lake Hövsgöl and Crater Lake but differed for Lake Tahoe, which has been designated as ultra-oligotrophic by traditional pelagic measures such as transparency found in the literature. Analysis of similarity showed that Lake Tahoe and Lake Hövsgöl chironomid communities were more similar to each other than either was to Crater Lake communities. Diversity varied between the three lakes and spatially within each lake. This research shows that chironomid communities from these large lakes were sensitive to trophic conditions. Chironomid communities were similar between the deep environments of Lake Hövsgöl and Lake Tahoe, indicating that chironomid communities from these lakes may be useful in comparing trophic state changes in large lakes. Spatial variation in Lake Tahoe’s diversity is indicative of differential response of chironomid communities to nutrient enrichment which may be an indication of changes in trophic state within and across habitats.     

Bacterial diversity within five unexplored freshwater lakes interconnected by surface channels in East Antarctic Dronning Maud Land (Schirmacher Oasis) using amplicon pyrosequencing

The Schimacher Oasis, an ice-free plateau in East Antarctic Dronning Maud Land, consists of over 120 freshwater lakes. These lakes are connected largely through four major surface channels. The bacterial diversity in these lake ecosystems remains largely unexplored. In this study, we compared the bacterial diversity in five freshwater lakes (L42, L46, L47, L50, and L51) interconnected by two surface channels using bacterial tag-encoded FLX amplicon pyrosequencing (bTEFAP) method. We further compared the resultant bacterial composition from these five lakes with another freshwater lake in the Schirmacher Oasis, Lake Tawani(P), which is not connected through the same surface channels. Using bTEFAP, we differentiated nine different phyla with the phyla Proteobacteria (especially the class Alphaproteobacteria) and Bacteroidetes (the class Sphingobacteria) dominating in lakes interconnected by surface channel 1, while the phyla Chloroflexi and Firmicutes were highly abundant in lakes interconnected by surface channel 2. The operational taxonomic unit (OTU) network and Principle Coordinate Analysis (PCoA) plot based on unweighted UNIFRAC determined that the bacterial assemblages found in these five lakes are different than the bacterial composition residing in Lake Tawani(P). The distribution and the diversity of the bacterial communities in Schirmacher Oasis freshwater lakes that are connected through surface channels may provide an insight into the role of the extreme physico-chemical parameters that help shape microbially driven functional ecosystems in other oases on this icy continent.     

Rhodoferax-related pufM gene cluster dominates the aerobic anoxygenic phototrophic communities in German freshwater lakes

The presence of aerobic anoxygenic phototrophs (AAPs) has been repeatedly reported from various marine environments, but their distribution in freshwater lakes was neglected until recently. We investigated the phylogenetic composition of AAP communities in 10 lakes in Northeastern Germany with different trophic status including oligotrophic Lake Stechlin and humic matter rich Lake Grosse Fuchskuhle. The AAP community was composed by members of Alpha- and Betaproteobacteria, but their contribution varied largely among the studied lakes. Our results show that AAP community composition in the studied lakes was affected mostly by pH and humic matter content. While alkaline lakes were mostly composed of Betaproteobacteria, the acidic and humic matter rich south-west (SW) basin of Lake Grosse Fuchskule was dominated (87%) by Alphaproteobacteria. The most frequent group within Betaproteobacteria was a cluster of pufM genes which was phylogenetically related to Rhodoferax representing 38.5% of all retrieved sequences. Alphaproteobacteria-related sequences had a broader phylogenetic diversity including six different taxa dominated by Sphingomonas- and Rhodobacter-like bacteria in lakes with alkaline to neutral pH. In the acidic and humic matter-rich SW basin of Lake Grosse Fuchskuhle, however, Methylobacterium-related sequences dominated the AAP community. We suggest that the variable AAP community structure might reflect the potential of these bacteria to cope with the contrasting conditions in freshwater environments.     

Isolation and phylogenetic analysis of cultivable manganese bacteria in sediments from the Arctic Ocean

Isolation, molecular identification and phylogenetic analysis were carried out to investigate the biodiversity of manganese bacteria in sediments which were collected from the Arctic Ocean during the 2nd Chinese Arctic Scientific Expedition. 21 and 19 species of cultivable strains were isolated from sediments at Stations P11 and S11, respectively, according to their distinct morphological character on the screening plate of manganese medium. Molecular identification and phylogenetic analysis showed that the cultivable manganese bacteria from Station P11 were basically composed of γ-Proteobacteria (γ subgroup of the Proteobacteria branch of the domain Bacteria) and Actinobacteria, which accounted for 86% and 14%, respectively. The isolates of γ-Proteobacteria mainly included Psychrobacter, Shewanella, Acinetobacter and Marinobacter, of which Psychrobacter was the major genus, which accounted for 67% of the γ-Proteobacteria. The cultivable manganese bacteria from Station S11 included α-Proteobacteria, γ-Proteobacteria and Flavobacteria of Bacteroides. The γ-Proteobacteria mainly included Shewanella, Marinomonas and Alteromonas. The majority of α-Proteobacteria was Sphingomonas. The phylogenetic analysis indicated that bacteria from sediments at Stations P11 and S11 had different cultivable manganese microbial communities. All tested strains had higher resistance to Mn2+, of which Marinomonas sp. S11-S-4 had the highest resistant ability.     

Alkaliphilic anaerobic community at pH 10

Relict or ancient microbial communities in extreme environment might be analogous to the centers of origin of bacterial diversity. A bacterial community of an alkaline lake was investigated, and the diversity of bacteria found there indicates that both conditions of autonomy and phylogenetic variety are fulfilled for anaerobic bacteria developing at pH 10±0.2. Major functional groups in the trophic network were present. Representatives of proteolytic, bacteriolytic, cellulolytic, saccharolytic, dissipotrophic, acetogenic, sulfate-reducing, methanogenic bacteria were isolated.     

Do Patterns of Bacterial Diversity along Salinity Gradients Differ from Those Observed for Macroorganisms?

It is widely accepted that biodiversity is lower in more extreme environments. In this study, we sought to determine whether this trend, well documented for macroorganisms, also holds at the microbial level for bacteria. We used denaturing gradient gel electrophoresis (DGGE) with phylum-specific primers to quantify the taxon richness (i.e., the DGGE band numbers) of the bacterioplankton communities of 32 pristine Tibetan lakes that represent a broad salinity range (freshwater to hypersaline). For the lakes investigated, salinity was found to be the environmental variable with the strongest influence on the bacterial community composition. We found that the bacterial taxon richness in freshwater habitats increased with increasing salinity up to a value of 1‰. In saline systems (systems with >1‰ salinity), the expected decrease of taxon richness along a gradient of further increasing salinity was not observed. These patterns were consistently observed for two sets of samples taken in two different years. A comparison of 16S rRNA gene clone libraries revealed that the bacterial community of the lake with the highest salinity was characterized by a higher recent accelerated diversification than the community of a freshwater lake, whereas the phylogenetic diversity in the hypersaline lake was lower than that in the freshwater lake. These results suggest that different evolutionary forces may act on bacterial populations in freshwater and hypersaline lakes on the Tibetan Plateau, potentially resulting in different community structures and diversity patterns.     

Metagenomic Insights into the Evolution, Function, and Complexity of the Planktonic Microbial Community of Lake Lanier, a Temperate Freshwater Ecosystem

Lake Lanier is an important freshwater lake for the southeast United States, as it represents the main source of drinking water for the Atlanta metropolitan area and is popular for recreational activities. Temperate freshwater lakes such as Lake Lanier are underrepresented among the growing number of environmental metagenomic data sets, and little is known about how functional gene content in freshwater communities relates to that of other ecosystems. To better characterize the gene content and variability of this freshwater planktonic microbial community, we sequenced several samples obtained around a strong summer storm event and during the fall water mixing using a random whole-genome shotgun (WGS) approach. Comparative metagenomics revealed that the gene content was relatively stable over time and more related to that of another freshwater lake and the surface ocean than to soil. However, the phylogenetic diversity of Lake Lanier communities was distinct from that of soil and marine communities. We identified several important genomic adaptations that account for these findings, such as the use of potassium (as opposed to sodium) osmoregulators by freshwater organisms and differences in the community average genome size. We show that the lake community is predominantly composed of sequence-discrete populations and describe a simple method to assess community complexity based on population richness and evenness and to determine the sequencing effort required to cover diversity in a sample. This study provides the first comprehensive analysis of the genetic diversity and metabolic potential of a temperate planktonic freshwater community and advances approaches for comparative metagenomics.     

Composition of freshwater bacterial communities associated with cyanobacterial blooms in four Swedish lakes

The diversity of freshwater bacterioplankton communities has not been extensively studied despite their key role in foodwebs and the cycling of carbon and associated major elements. In order to explore and characterize the composition of bacterioplankton associated with cyanobacterial blooms, large 16S rRNA clone libraries from four lakes experiencing such blooms were analysed. The four libraries contained 1461 clones, of which 559 were prokaryotic sequences of non-cyanobacterial origin. These clones were classified into 158 operational taxonomic units affiliated mainly with bacterial divisions commonly found in freshwater systems, e.g. Proteobacteria, Bacteriodetes, Actinobacteria, Verrucomicrobia and Planctomycetes. Richness and evenness of non-cyanobacterial clones were similar to other clone libraries obtained for freshwater bacterioplankton, suggesting that bacterial communities accompanying cyanobacterial blooms are as diverse as non-bloom communities. Many of the identified operational taxonomic units grouped with known freshwater clusters but the libraries also contained novel clusters of bacterial sequences that may be characteristic for cyanobacterial blooms. About 25% of the operational taxonomic units were detected in more than one lake. Even so, 16S rRNA heterogeneity analysis demonstrated large differences in community composition between lakes regardless of their similar characteristics and close proximity. Hence even the similar environmental conditions created by different cyanobacterial blooms may foster very dissimilar bacterial communities, which could indicate that the genetic diversity in lake bacteria have been underestimated in the past.     

Specific detection of different phylogenetic groups of chemocline bacteria based on PCR and denaturing gradient gel electrophoresis of 16S rRNA gene fragments

Specific amplification of 16S rRNA gene fragments in combination with denaturing gradient gel electrophoresis (DGGE) was used to generate fingerprints of Chromatiaceae, green sulfur bacteria, Desulfovibrionaceae, and β-Proteobacteria. Sequencing of the gene fragments confirmed that each primer pair was highly specific for the respective phylogenetic group. Applying the new primer sets, the bacterial diversity in the chemoclines of a eutrophic freshwater lake, a saline meromictic lake, and a laminated marine sediment was investigated. Compared to a conventional bacterial primer pair, a higher number of discrete DGGE bands was generated using our specific primer pairs. With one exception, all 15 bands tested yielded reliable 16S rRNA gene sequences. The highest diversity was found within the chemocline microbial community of the eutrophic freshwater lake. Sequence comparison revealed that the six sequences of Chromatiaceae and green sulfur bacteria detected in this habitat all represent distinct and previously unknown phylotypes. The lowest diversity of phylotypes was detected in the chemocline of the meromictic saline lake, which yielded only one sequence each of the Chromatiaceae, β-2-Proteobacteria, and Desulfovibrionaceae, and no sequences of green sulfur bacteria. The newly developed primer sets are useful for the detection of previously unknown phylotypes, for the comparison of the microbial diversity between different natural habitats, and especially for the rapid monitoring of enrichments of unknown bacterial species. Received: 22 January 1999 / Accepted: 28 April 1999     

Intra- and inter-lake variability of free-living and particle-associated Actinobacteria communities

We have analysed the inter- and intra-lake variability of free-living and particle-associated freshwater Actinobacteria communities in four limnological different lakes of the Mecklenburg Lake District, Northeastern Germany. Denaturing gradient gel electrophoresis (DGGE) specific for Actinobacteria was used to investigate phylogenetic diversity and seasonal dynamics of actinobacterial communities in the epilimnion of all lakes (inter-lake variability) and to assess differences between Actinobacteria communities of the epi-, meta- and hypolimnion of a single lake (intra-lake variability) respectively. DGGE analyses showed significant inter- and intra-lake differences between Actinobacteria communities of all lakes and water layers as well as between free-living and particle-associated Actinobacteria. Phylogenetic inferences of 16S rRNA gene sequences suggest that particular members of particle-associated Actinobacteria were exclusively affiliated to certain actinobacterial lineages. The phylogenetic comparison of 16S rRNA gene sequences of all lakes and water layer, however, indicated the occurrence of almost similar phylogenetic lineages in all studied habitats and suggest high intracluster diversity within already known actinobacterial lineages. Non-metric multidimensional scaling (NMS) ordination analyses and Pearson's product moment correlations revealed several strong correlations between the investigated Actinobacteria communities and various limnological parameters, such as conductivity, total phosphorous, alkalinity or primary production. However, no uniform correlation patterns were found between lakes, water layers and bacterial fractions. These heterogeneous correlation patterns together with the phylogenetic similarities of Actinobacteria communities from different lakes indicate that particular Actinobacteria represent various ecotypes or exhibit a pronounced ecophysiological plasticity.     

Evaluating functional diversity conservation for freshwater fishes resulting from terrestrial protected areas

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Diversity of the major capsid genes (g23) of T4-like bacteriophages in the eutrophic Lake Kotokel in East Siberia, Russia

Numerous studies revealed high diversity of T4-like bacteriophages in various environments, but so far, little is known about T4-like virus diversity in freshwater bodies, particularly in eutrophic lakes. The present study was aimed at elucidating molecular diversity of T4-like bacteriophages in eutrophic Lake Kotokel located near Lake Baikal by partial sequencing of the major capsid genes (g23) of T4-like bacteriophages. The majority of g23 fragments from Lake Kotokel were most similar to those from freshwater lakes and paddy fields. Despite the proximity and direct water connection between Lake Kotokel and Lake Baikal, g23 sequence assemblages from two lakes were different. UniFrac analysis showed that uncultured T4-like viruses from Lake Kotokel tended to cluster with those from the distant lake of the same trophic status. This fact suggested that the trophic conditions affected the formation of viral populations, particularly of T4-like viruses, in freshwater environments.     

Modelling the importance of sediment bacterial carbon for profundal macroinvertebrates along a lake nutrient gradient

In dimictic, temperate lakes little is known about the quantitative importance of trophic coupling between pelagic and profundal communities. Although it is a generally accepted paradigm that profundal secondary production is dependent on autochthonous pelagic production (primarily diatoms), the importance of interactions between phytodetrital inputs, sediment bacteria, and macroinvertebrates are still not well understood. In this study, we used theoretical models to estimate macroinvertebrate carbon requirement (production + respiration) and bacterial production for lakes of different trophic categories. Comparisons of estimates show that the importance of bacterial production as a carbon source for benthic macroinvertebrates is inversely related to lake trophic state. Assuming that infauna assimilates 50% of ingested bacterial carbon, this food source could account for between 47% (oligotrophic lakes) and 2% (hypertrophic lakes) of their carbon demand. These calculations indicate that bacterial carbon should not be an important C-resource for profundal macroinvertebrates of eutrophic and hypertrophic lakes.     

太湖夏季浮游细菌群落多样性的空间格局

为了研究太湖夏季浮游细菌群落多样性与水体营养盐的关系,在太湖全湖范围内开展了一次大规模浮游细菌采样调查,分析了太湖不同湖区浮游细菌丰度和多样性组成。研究发现,浮游细菌丰度在不同湖区中存在明显的空间差异,从北部和西部湖区沿湖流向东南方向至湖心和南部沿岸再到东部湖区呈下降趋势,这与太湖水体营养水平从高到低变化趋势一致。浮游细菌丰度与营养盐浓度回归分析结果显示,总磷（TP）与细菌丰度存在较好的正相关（R2=0.6392,n=29,P0.01）,而总氮（TN）与细菌丰度无显著相关（R2=0.0663,n=29,P0.05）。因此,磷是太湖夏季浮游细菌生长的限制因子。不同湖区营养盐与浮游细菌群落多样性也具有显著的正相关,随着营养水平的升高,浮游细菌多样性增加。此外,细菌群落的组成在不同湖区间亦具有明显的空间异质性,与不同湖区营养水平空间变化一致。研究结果将有助于人们更好地理解淡水湖泊中微生物循环和生态系统功能。