Distribution Of Bacterioplankton Research Articles

Abundance and Distribution of Bacterioplankton in the Middle and Lower Reaches of the Ob River in Areas Impacted by Cities

Abundance and Distribution of Bacterioplankton in the Middle and Lower Reaches of the Ob River in Areas Impacted by Cities

Shifts in bacterioplankton community structure between dry and wet seasons in a tropical estuary strongly affected by riverine discharge

Estuaries are among the most productive ecosystems in the world and are highly dynamic due to the interaction of freshwater and seawater, which results in strong spatial gradients in physico-chemical conditions. Bacterioplankton play a central role in these systems, driving the fluxes of carbon and energy, and being central for contaminant removal in human-impacted areas. Most studies on bacterioplankton dynamics have been carried out in temperate estuaries, and they show that salinity is a major factor driving bacterioplankton distribution. Tropical estuaries, although largely understudied, experience drastic variations in river discharge between the dry and the rainy seasons, influencing the spatial distribution of the salinity gradient and thus likely impacting bacterioplankton communities. Using Illumina sequencing of the 16S rRNA gene, here we studied bacterial communities from the Nicoya's Gulf (Costa Rica), a large tropical estuary characterized by high riverine discharge during the rainy season, to explore seasonal changes in the spatial distribution and connectivity of these communities along the Gulf. Our results show pronounced differences in bacterial diversity and community structure between seasons and zones within the estuary (the shallow upper Gulf, the middle zone and the lower zone, located in the marine end of the estuary). Bacterial communities from the different regions were more similar during the rainy season, suggesting a larger degree of microbial connectivity likely driven by the fast water circulation fueled by the riverine discharge. In the dry season, Enterobacteriales and Cyanobacteria dominated bacterial communities, whereas in the rainy season Alphaproteobacteria was the dominant group. These contrasting seasonal trends were consistent with the seasonal variations observed in bacterial assemblages during a year at a single station in the upper region of the Gulf. We conclude that the Gulf is highly dynamic in both the spatial and temporal scale and that bacterioplankton communities are strongly influenced by the riverine and tidal inputs during both seasons. This study sheds light on the sources of variability in the structure of bacterial communities in tropical estuarine systems, an understudied type of aquatic ecosystem, and sets the basis to design further comprehensive studies on their microbial diversity.

Diversity, structure, and distribution of bacterioplankton and diazotroph communities in the Bay of Bengal during the winter monsoon.

The Bay of Bengal (BoB) is conventionally believed to be a low productive, oligotrophic marine ecosystem, where the diazotroph communities presumed to play a vital role in adding "new" nitrogen through the nitrogen fixation process. However, the diazotroph communities in the oceanic region of the BoB are still poorly understood though it represents most of the seawater volume. The present study investigated a detailed account of the bacterioplankton community structure and distribution in the oceanic BoB during the winter monsoon using high throughput sequencing targeting the 16S rRNA and nifH genes. Our study observed diverse groups of bacterioplankton communities in the BoB including both cyanobacterial and non-cyanobacterial phylotypes. Cyanobacteria (Prochlorococcus spp. and Synechococcus spp.) and Proteobacteria (mainly α-, γ-, and δ-Proteobacteria) were the most abundant groups within the bacterial communities, possessing differential vertical distribution patterns. Cyanobacteria were more abundant in the surface waters, whereas Proteobacteria dominated the deeper layers (75 m). However, within the diazotroph communities, Proteobacteria (mainly γ-Proteobacteria) were the most dominant groups than Cyanobacteria. Function prediction based on PICRUSt revealed that nitrogen fixation might more active to add fixed nitrogen in the surface waters, while nitrogen removal pathways (denitrification and anammox) might stronger in deeper layers. Canonical correspondence analysis (CCA) indicated that temperature, salinity, and silicate were major environmental factors driving the distribution of bacterial communities. Additionally, phosphate was also an important factor in regulating the diazotroph communities in the surface water. Overall, this study provided detailed information on bacterial communities and their vital role in the nitrogen cycles in oligotrophic ecosystems.

Diversity and distribution of bacterioplankton in the coastal upwelling waters off Hainan Island, China

Diversity and distribution of bacterioplankton in the coastal upwelling waters off Hainan Island, China

Spatial distribution of bacterioplankton community composition and their diversity in Lake Fuxian during thermal stratification period

水体垂向分层是深水湖泊一个重要的特征，这不仅影响水体理化环境因子，而且影响水生生物组成的垂向分布，但是对不同水层水体细菌的多样性和群落结构组成的形成与维持机制知之甚少. 本研究以抚仙湖为研究对象，在水体热力分层期间采集不同位点、不同水层水样，借助16S rDNA Illumina Miseq高通量测序技术，探究水体细菌多样性和群落结构组成的空间分布特征及关键影响因子. 研究结果表明：(1)抚仙湖北部湖心在水深15~40 m处出现温跃层，温度由23℃降至15℃，其余理化环境因子也存在明显的垂向分层现象；与垂向差异相比，表层水体各理化因子在水平方向上的差异相对较小. (2)在水平方向上，南部湖心表层水体细菌alpha多样性(Operational Taxonomic Unit数目和Faith's phylogenetic diversity)最高；在垂向上，水体细菌alpha多样性随着采样水深的增加呈现单峰分布，在30和40 m水层最高；水体细菌alpha和beta多样性的垂向差异均显著大于水平方向差异. (3)表层水体细菌主要由Actinomycetales、unidentified Cyanobacteria、Burkholderiales和Sphingobacteriales组成；温跃层中以Pseudomonadales为主；均温层的优势菌群为unidentified Chloroflexi、Actinomycetales和Burkholderiales. 典范对应分析表明溶解性有机碳、溶解氧、硝态氮、氨氮和总磷浓度是影响细菌群落组成的主要环境因子.;Deep lakes are typically characterized by thermal stratification throughout the year, except for a short mixing period in winter. This vertical partitioning has important effects on many biotic, physical and chemical characteristics of the water column. However, at present, little is known about how these changes affect the vertical distribution of bacterioplankton community diversity. In this study, Lake Fuxian with a relatively long thermal stratification period every year, was chosen for the investigation of bacterioplankton distribution, diversity and composition on August 25th, 2013. 16S rDNA Illumina Miseq high-throughput sequencing technology was performed on DNA extracted from water samples collected from different locations and different water depths. The results showed that: (1) A thermocline appeared in the lake center and in the northern part of this lake at the depth of 15-40 m, with the temperature dropping from 23℃ to 15℃. Other physical and chemical factors also showed obvious vertical stratification pattern. Horizontally, there is no significant difference in physicochemical features. (2) In the horizontal direction, the alpha diversities of plankton bacteria (the number of Operational Taxonomic Units and Faith's phylogenetic diversity) in the surface water of the southern lake center was the highest; in the vertical direction, the alpha diversity gradually increased with the increase of the sampling depth, topping at the depths of 30 m or 40 m, and then gradually decreased; the difference of the bacterioplankton alpha and beta diversity in the vertical direction was significantly greater than those in the horizontal direction. (3) The bacterioplankton in the epilimnion were mainly composed of Actinomycetales, unidentified Cyanobacteria, Burkholderiales and Sphingobacteriales; the relative abundance of Pseudomonadales in the thermocline significantly increased and became dominant; unidentified Chloroflexi, Actinomycetales and Burkholderiales were the dominant bacterial taxa in the hypolimnion. The canonical correspondence analysis demonstrated that the concentrations of dissolved organic carbon, dissolved oxygen, nitrate, ammonium and total phosphorus are the significant environmental variables shaping the bacterial community's composition and diversity.

Micro-scale spatial distribution of bacterioplankton in the Priplotinny (Near-dam) Reach of the Kuibyshev Reservoir in the early autumn period 2020

A detailed study of the distribution of bacterioplankton and photosynthetic pigments of the Priplotinny Reach of the Kuibyshev Reservoir was carried out in early autumn 2020. The bacterioplankton cell numbers were 0.8-2.1 106 cells ml−1, and the biomass varied from 7 to 56 μg C L−1. The average chlorophyll a concentration of in the integral samples was 2.91 μg L−1, varying in the range of 1.1-9.6 μg L−1 (CV 30.7%). The pheophytin content was relatively low, 19.2 ± 10.4% of chlorophyll concentration, indicating the continued active phytoplankton development in the seston in the fall of 2020. From September 17 to October 3, a weak trend for an increase in bacterioplankton abundance as well as for a decrease in the chlorophyll a concentration and in the average cell volume was revealed. A significant (p < 0.05) correlation between the Chl a concentration in the total biomass of heterotrophic bacteria (r = 0.48) was observed. Under conditions of intense wind mixing, anthropogenic sources of pollution and the inflow of the inflow did not have a significant effect on the size structure of bacterioplankton. No pronounced local spatial complexes of stations were revealed in terms of quantitative and structural parameters of bacterioplankton and chlorophyll concentrations in the investigated part of the reservoir. In general, the concentration of pigments and the abundance and biomass of bacterioplankton correspond to the mesotrophic status of the Reach. Both the total number of bacterioplankton and the chlorophyll content in Pryplotinny Reach at the beginning of autumn 2020 are within the range of long-term monitoring values. While in the summer there is a clear long-term increasing trend of the bacterioplankton abundance, in the autumn the bacterioplankton numbers remain stable throughout the entire reservoir existence period.

Seasonality of the Microbial Community Composition in the North Atlantic

Planktonic communities constitute the basis of life in marine environments and have profound impacts in geochemical cycles. In the North Atlantic, seasonality drives annual transitions in the ecology of the water column. Phytoplankton bloom annually in spring as a result of these transitions, creating one of the major biological pulses in productivity on earth. The timing and geographical distribution of the spring bloom as well as the resulting biomass accumulation have largely been studied using the global capacity of satellite imaging. However, fine-scale variability in the taxonomic composition, spatial distribution, seasonal shifts, and ecological interactions with heterotrophic bacterioplankton has remained largely uncharacterized. The North Atlantic Aerosols and Marine Ecosystems Study (NAAMES) conducted four meridional transects to characterize plankton ecosystems in the context of the annual bloom cycle. Using 16S rRNA gene-based community profiles we analyzed the temporal and spatial variation in plankton communities. Seasonality in phytoplankton and bacterioplankton composition was apparent throughout the water column, with changes dependent on the hydrographic origin. From winter to spring in the subtropic and subpolar subregions, phytoplankton shifted from the predominance of cyanobacteria and picoeukaryotic green algae to diverse photosynthetic eukaryotes. By autumn, the subtropics were dominated by cyanobacteria, while a diverse array of eukaryotes dominated the subpolar subregions. Bacterioplankton were also strongly influenced by geographical subregions. SAR11, the most abundant bacteria in the surface ocean, displayed higher richness in the subtropics than the subpolar subregions. SAR11 subclades were differentially distributed between the two subregions. Subclades Ia.1 and Ia.3 co-occurred in the subpolar subregion, while Ia.1 dominated the subtropics. In the subtropical subregion during the winter, the relative abundance of SAR11 subclades “II” and 1c.1 were elevated in the upper mesopelagic. In the winter, SAR202 subclades generally prevalent in the bathypelagic were also dominant members in the upper mesopelagic zones. Co-varying network analysis confirmed the large-scale geographical organization of the plankton communities and provided insights into the vertical distribution of bacterioplankton. This study represents the most comprehensive survey of microbial profiles in the western North Atlantic to date, revealing stark seasonal differences in composition and richness delimited by the biogeographical distribution of the planktonic communities.

Unraveling the distribution patterns of bacterioplankton in a mesoscale cyclonic eddy confined to an oxygen-depleted basin

Mesoscale eddies in oxygen minimum zones profoundly affect the structure and productivity of marine planktonic communities and alter key biogeochemical cycles. The influence of a mesoscale cyclonic eddy on the spatial distribution of bacterioplankton was investigated in a semi-enclosed, oxygen-depleted basin in the Gulf of California, Mexico. Most of the bacterial taxa showed a strong vertical distribution from oxygen-rich surface waters to anoxic bottom waters, but also a horizontal distribution pattern in the upper ocean associated with the eddy presence. Synechococcocales, Flavobacteriales, SAR86, and Actinomarinales were abundant in the euphotic zone within the Gulf of California water mass, whereas SAR324, SAR406, SAR202, SUP05, Arctic97B-4, and Thioglobaceae dominated the bottom layer of this basin within the Subtropical Subsurface water mass. In contrast, bacterial taxa with a preference for mesopelagic waters (Thiomicrospirales, SAR324, SAR202, HOC36, UBA10353 marine group, and Nitrospinales) dominated surface waters of the eddy center where common surface taxa (Synechococcus, SAR86, and Actinomarinales) were scarce. These changes in community composition led to a distinct diversity of bacterioplankton between the center and edges of the eddy within the euphotic zone. These results show the strong role of oxygen and water masses in controlling the vertical distribution of bacterioplankton, whereas the eddy more strongly modifies the bacterial assemblage in the upper ocean.

Spatial Distribution Patterns of Bacterioplankton in the Oxygen Minimum Zone of the Tropical Mexican Pacific.

Microbial communities within oxygen minimum zones (OMZs) are crucial drivers of marine biogeochemical cycles; however, we still lack an understanding of how these communities are distributed across an OMZ. We explored vertical (from 5 to 500m depth) and horizontal (coast to open ocean) distribution of bacterioplankton and its relationships with the main oceanographic conditions in three transects of the tropical Mexican Pacific OMZ. The distribution of the microbial diversity and the main clades changed along the transition from oxygen-rich surface water to the OMZ core, demonstrating the sensitivity of key bacterial groups to deoxygenation. The euphotic zone was dominated by Synechococcales, followed by Flavobacteriales, Verrucomicrobiales, Rhodobacterales, SAR86, and Cellvibrionales, whereas the OMZ core was dominated by SAR11, followed by SAR406, SAR324, SAR202, UBA10353 marine group, Thiomicrospirales and Nitrospinales. The marked environmental gradients along the water column also supported a high potential for niche partitioning among OMZ microorganisms. Additionally, in the OMZ core, bacterial assemblages from the same water mass were more similar to each other than those from another water mass. There were also important differences between coastal and open-ocean communities: Flavobacteriales, Verrucomicrobiales, Rhodobacterales, SAR86, and Cellvibrionales were more abundant in coastal areas, while Synechococcales, SAR406, SAR324, SAR202, UBA10353 marine group, and Thiomicrospirales were more abundant in the open ocean. Our results suggest a biogeographic structure of the bacterioplankton in this OMZ region, with limited community mixing across water masses, except in upwelling events, and little dispersion of the community by currents in the euphotic zone.

Heterotrophic Bacterioplankton of the Laptev and East Siberian Sea Shelf Affected by Freshwater Inflow Areas

The present study examined the hydrochemical and biological parameters influencing the spatial distribution of bacterioplankton in the Laptev Sea and the East Siberian Sea shelf regions affected by the Khatanga, Indigirka and Kolyma rivers runoff during September 2017. The highest bacterial abundance and the amount of actively respiring bacteria were determined in rivers delta and in surface water along the edge of continental shelf. Despite the expectations based on previous studies salinity was not the determining factor affecting spatial distribution and activity of bacterioplankton. Bacterial abundance and biomass were significantly and positively correlated with chlorophyll “a” and pheophytin content.

Illumina MiSeq sequencing and network analysis the distribution and co-occurrence of bacterioplankton in Danjiangkou Reservoir, China.

Network analysis has contributed to studies of the interactions of microorganisms and the identification of key populations. However, such analysis has rarely been conducted in the study of reservoir bacterioplankton communities. This study investigated the bacterioplankton community composition in the surface water of the Danjiangkou Reservoir using the Illumina MiSeq sequencing platform. We observed that the bacterioplankton community primarily consisted of 27 phyla and 336 genera, including Actinobacteria, Proteobacteria, and Bacteroidetes, demonstrating the richness of the community composition. Redundancy analysis of the bacterioplankton communities and environmental variables showed that the total nitrogen (TN), pH, chemical oxygen demand (COD), and permanganate index (CODMn) were important factors affecting the bacterioplankton distribution. Network analysis was performed using the relative abundances of bacterioplankton based on the phylogenetic molecular ecological network (pMEN) method. The connectivity of node i within modules (Zi), the connectivity of node i among modules (Pi), and the number of key bacteria were high at the Taizishan and Heijizui sites, which were associated with higher TN contents than at the other sites. Among the physicochemical properties of water, TN, ammonia nitrogen (NH4-N), pH, COD, and dissolved oxygen (DO) might have great influences on the functional units of the bacterial communities in bacterioplankton molecular networks. This study improves the understanding of the structure and function of bacterioplankton communities in the Danjiangkou Reservoir.

Cyanobacterial blooms alter the relative importance of neutral and selective processes in assembling freshwater bacterioplankton community

CyanoHABs have substantial impacts on the functioning and sustainability of freshwater ecosystems by restricting light penetration, depleting dissolved oxygen, and producing various toxins. This study combined physicochemical variable measurements, 16S rRNA gene sequencing and microscopy observations to examine mechanisms that govern the assembly of bacterioplankton communities following the progress of cyanobacterial blooms in a freshwater reservoir. Throughout the sampling season, bacterioplankton distribution patterns were well predicted by a neutral model, which assumes passive dispersal and ecological drift as the predominate mechanisms for community assembly. The neutral model consistently explained the distribution of over 67% of bacterioplankton OTUs and its fit was weaker during the cyanobacterial blooms (R2 = 0.322) than the before- (R2 = 0.549) and after-bloom stages (R2 = 0.535). Variations of environmental factors, acting as selective pressures, explained shifts of non-neutral OTUs (above/under neutral prediction) (63.9%) better than neutral OTUs (34.5%). Co-occurrence network analysis organized microbial communities into modules and revealed strong positive correlations between bacterioplankton and cyanobacteria than with planktonic algae and zooplankton. Overall, our results suggest that neutral processes play significant roles in assembling bacterioplankton communities over a cyanobacterial bloom succession and its relative importance may be weakened by biotic pressures (interspecific interactions) during the bloom period. Our results also indicate that among biotic factors, cyanobacteria had greater impacts on bacterioplankton community assembly than planktonic algae and zooplankton.

Water masses influence bacterioplankton community structure in summer Kongsfjorden.

To ascertain the saying "Everything is everywhere, but the environment selects", it was imperative to find out the main factor influencing bacterioplankton composition at genus level of Kongsfjorden where was influenced both by glacier melting water and Atlantic water. Thus, bacterioplankton diversity was investigated using pyrosequencing. In addition, nutrients, chlorophyll a, in situ temperature and salinity were measured. There were seventeen of 33 identified genera with relative abundance > 0.1%. Redundancy analysis showed that 73.02% of bacterioplankton community variance could be explained by environmental parameters. Furthermore, most of the abundant genera demonstrated significant correlation with environment parameters revealed by correlation analysis. Moreover, phosphate, nitrate and Chl a concentration, and the abundance of top nine identified genera varied with water mass significantly as shown by analysis of variance. Our results supported the notion that environmental factors, especially water mass had significant effect on bacterioplankton distribution at genus level. Considering the high sensitivity to environmental change and low error rate in identification, bacterioplankton at genus level could be potential bio-markers for monitoring environmental changes.

Effects of Habitat Partitioning on the Distribution of Bacterioplankton in Deep Lakes.

In deep lakes, many investigations highlighted the existence of exclusive groups of bacteria adapted to deep oxygenated and hypoxic and anoxic hypolimnia. Nevertheless, the extent of bacterial strain diversity has been much less scrutinized. This aspect is essential for an unbiased estimation of genetic variation, biodiversity, and population structure, which are essential for studying important research questions such as biogeographical patterns, temporal and spatial variability and the environmental factors affecting this variability. This study investigated the bacterioplankton community in the epilimnetic layers and in the oxygenated and hypoxic/anoxic hypolimnia of five large and deep lakes located at the southern border of the Alps using high throughput sequencing (HTS) analyses (16S rDNA) and identification of amplicon sequence variants (ASVs) resolving reads differing by as little as one nucleotide. The study sites, which included two oligomictic (Garda and Como) and three meromictic lakes (Iseo, Lugano, and Idro) with maximum depths spanning from 124 to 410 m, were chosen among large lakes to represent an oxic-hypoxic gradient. The analyses showed the existence of several unique ASVs in the three layers of the five lakes. In the case of cyanobacteria, this confirmed previous analyses made at the level of strains or based on oligotyping methods. As expected, the communities in the hypoxic/anoxic monimolimnia showed a strong differentiation from the oxygenated layer, with the exclusive presence in single lakes of several unique ASVs. In the meromictic lakes, results supported the hypothesis that the formation of isolated monimolimnia sustained the development of highly diversified bacterial communities through ecological selection, leading to the establishment of distinctive biodiversity zones. The genera identified in these layers are well-known to activate a wide range of redox reactions at low O2 conditions. As inferred from 16S rDNA data, the highly diversified and coupled processes sustained by the monimolimnetic microbiota are essential ecosystem services that enhance mineralization of organic matter and formation of reduced compounds, and also abatement of undesirable greenhouse gasses.

Interactome‐based abiotic and biotic impacts on biodiversity of plankton communities in disturbed wetlands

AbstractAimDespite great efforts for conservation, biodiversity in wetland ecosystems is still losing at an alarming rate. Thus, it is crucial to deeply understand ecological processes and mechanisms that potentially affect the loss of biodiversity.LocationSanjiang wetland in Sanjiang floodplain, north‐east China.MethodsBiological samples and environmental data were collected from five approximate habitats under different anthropogenic disturbance levels from Sanjiang wetland. Biodiversity of plankton communities (i.e., bacterioplankton and zooplankton) was characterized by high‐throughput sequencing‐based metabarcoding. Multidisciplinary methods including interactome‐based construction of scale‐free networks were employed to examine the complex biotic interactions and abiotic influence on plankton biodiversity.ResultsBoth environmental variables and community composition of plankton communities varied significantly among five habitats. Environmental filtering was identified as the dominant ecological process that drove the distinct community composition and geographical distribution of biodiversity. However, the significantly influential factors were different for bacterioplankton (e.g., pH and As) and zooplankton communities (e.g., NH4 and TP). In total, environmental factors could explain approximately 30% of community variation for both types of plankton communities. Based on interactome networks, more organism‐associated edges were identified than environment‐associated edges. Such a pattern suggests that, in addition to environmental influence, biotic interactions also play a crucial role to shape biodiversity variation.Main conclusionsBoth abiotic factors and biotic interactions largely contributed to the distinct composition and geographical distribution of bacterioplankton and zooplankton communities in Sanjiang wetland. Therefore, the interactome‐based investigation is recommended to examine synthesized impacts of abiotic and biotic variables, and such a comprehensive survey can largely facilitate our understanding of ecological processes and associated mechanisms that drive the loss of wetland biodiversity. Results from comprehensive surveys can help identify conservation priorities and improve the predictability of conservation programmes.

Bacterioplankton abundance and biomass stimulated by water masses intrusions over the Southern Brazilian Shelf (between 25°57'S and 29°24'S)

In order to understand the distribution of bacterioplankton along the continental shelf off the Santa Catarina coast (25°57'S and 29°24'S) and whether water masses were affecting this distribution, we measured abundance, biovolume, and biomass of bacterioplankton, and the physico-chemical characteristics of the water masses in three transects in two distinct seasons: summer and winter of 2010. During the austral summer, high continental runoffs from the Itajaí River and Babitonga Bay mix over the shelf with Tropical Water (TW) and originate the summer Subtropical Shelf Water (STSW). Bacterial biomass reached an average of 2.5–5.0 μgC L−1 in summer, with values observed in the southernmost transect (Araranguá) being one order of magnitude higher when compared to the others, where nutrient-rich South Atlantic Central Water (SACW) intrusions are often near the coast. On the contrary, in the austral winter, the Plata Plume Water (PPW) spread on the first 40 m of water positively influenced bacterial abundance and biomass, which were on average ten times higher than those observed in the summer (abundance of up to 2.5 × 109 cells L−1, and biomass up to 60 μgC L−1). As a conclusion, PPW, indicated by the colder waters, high silicate and Kd values, and high concentrations of particulate organic carbon have a positive effect on the abundance and biomass of bacterioplankton, whereas the intrusions of SACW, and local freshwater runoffs have secondary effects on bacterial parameters. This is the first description of the influence of PPW intrusions over the dynamics of bacterioplankton, considering two contrasting environmental periods, and, consequently, to carbon budget studies in the Southern Brazilian Shelf (SBS). Taking into account both abundance and biomass of bacterioplankton and their association with water masses in the SBS, our results provide fundamental information for further biogeochemical studies.

Community differentiation of bacterioplankton in the epipelagic layer in the South China Sea.

The South China Sea (SCS) is the largest marginal sea in the western tropical Pacific Ocean and is characterized by complex physicochemical environments. To date, the biogeographic patterns of the microbial communities have rarely been reported at a basin scale in the SCS. In this study, the bacterial assemblages inhabiting the epipelagic zone across 110°E to 119°E along 14°N latitude were uncovered. The vertical stratification of both bacterial taxa and their potential functions were revealed. These results suggest that the water depth‐specific environment is a driver of the vertical bacterioplankton distribution. Moreover, the bacterial communities were different between the eastern stations and the western stations, where the environmental conditions were distinct. However, the mesoscale eddy did not show an obvious effect on the bacterial community due to the large distance between the sampling site and the center of the eddy. In addition to the water depth and longitudinal location of the samples, the heterogeneity of the phosphate and salinity concentrations also significantly contributed to the variance in the epipelagic bacterial community in the SCS. To the best of our knowledge, this study is the first to report that the variability in epipelagic bacterioplankton is driven by the physicochemical environment at the basin scale in the SCS. Our results emphasize that the ecological significance of bacterioplankton can be better understood by considering the relationship between the biogeographic distribution of bacteria and the oceanic dynamics processes.

Taxonomical Resolution and Distribution of Bacterioplankton Along the Vertical Gradient Reveals Pronounced Spatiotemporal Patterns in Contrasted Temperate Freshwater Lakes.

We examined the relationship between viruses and co-occurring bacterial communities across spatiotemporal scale in two contrasting freshwater lakes, namely meromictic Lake Pavin and dimictic Lake Aydat (Central France). Next-generation sequencing of 16S rRNA genes suggested distinct patterns in bacterioplankton community composition (BCC) between the lakes over depths and seasons. BCC were generally dominated by members of Actinobacteria, Proteobacteria, and Bacteroidetes covering about 95% of all sequences. Oxygen depletion at the bottom waters in Aydat and existence of permanent anoxia in the monimolimnion of Pavin resulted in the occurrence and dominance of lesser known members of lake communities such as Methylotenera, Methylobacter, Gallionella, Sulfurimonas, and Syntrophus in Pavin and Methylotenera and Sulfuritalea in Aydat. Differences in BCC appeared strongly related to dissolved oxygen concentration, temperature, viral infection, and virus-to-bacteria ratio. UniFrac analysis indicated a clear distinction in BCC when the percentage of viral infected bacterial cells and virus-to-bacteria ratio exceeded a threshold level of 10% and 5, respectively, suggesting a link between viruses and their potential bacterial host communities. Our study revealed that in both the lakes, the prevailing environmental factors across time and space structured and influenced the adaptation of bacterial communities to specific ecological niches.

Distribution of bacterioplankton with active metabolism in waters of the St. Anna Trough, Kara Sea, in autumn 2011

The distribution of bacterioplankton with active electron transport chains, as well as bacteria with intact cell membranes, was investigated for the first time in the region of St. Anna Trough in the Kara Sea. The average number of bacteria with active electron transport chains in the waters of the St. Anna Trough was 15.55 × 103 cells mL–1 (the limits of variation were 1.06–92.17 × 103 cells mL–1). The average number of bacteria with intact membranes was 33.46 × 103 cells mL–1 (the limits of variation were 6.78 to 103.18 × 103 cells mL–1). Almost all bacterioplankton microorganisms in the studied area were potentially viable, and the average share of bacteria with intact membranes was 92.1% of the total number of bacterioplankton (TNB) (the limits of variation were 76.2 to 98.4%). The share of bacteria with active metabolisms was 38.2% of the TNB (the limits of variation were 5.6–93.4%). The shares of the bacteria with active metabolisms were maximum in areas with the most stable environmental conditions (on the shelf and in deep water), whereas on the slope, where the gradients of water temperature and salinity were maximum, these values were lower.

南海北部海域春季浮游细菌和病毒空间分布及其影响因素

南海北部海域春季浮游细菌和病毒空间分布及其影响因素