Vertical and temporal variability of protist and prokaryotic summer plankton communities in a North Sea fjord

Understanding microbial community structure and the underlying control mechanisms are fundamental purposes of aquatic ecology. However, little is known about the seasonality and how trophic conditions regulate plankton community in subtropical reservoirs. In this study, we study the prokaryotic and picoeukaryotic communities and their interactions during wet and dry seasons in two subtropical reservoirs: one at oligotrophic state and another at mesotrophic state. Distinct microbial community compositions (prokaryotes and picoeukaryotes) and seasonal variation pattern were detected in the oligotrophic and mesotrophic reservoirs. The interactions between prokaryotic and picoeukaryotic communities were more prevalent in the oligotrophic reservoir, suggesting enhanced top-down control of small eukaryotic grazers on the prokaryotic communities. On the other hand, the microbial community in the mesotrophic reservoir was more influenced by physico-chemical parameters and showed a stronger seasonal variation, which may be the result of distinct nutrient levels in wet and dry seasons, indicating the importance of bottom-up control. Our study contributes to new understandings of the environmental and biological processes that shape the structure and dynamics of the planktonic microbial communities in reservoirs of different trophic states.

为了解丹江口库区浮游生物群落的多样性，本研究于2020年7月在丹江口库区丹库、汉库和入库支流等区域共计9个样点采集水体样品，抽滤并提取总DNA样本后，基于18S和16S分子标记进行单分子实时测序，分别探究真核和原核浮游生物群落的多样性及其群落特征.结果表明：（1）真核浮游生物群落的主要优势类群包括节肢动物、链型植物、绿藻门、硅藻门等；本研究在种水平上鉴定出库区分布广泛且相对丰度较大的物种，包括弯曲隐藻、对蛋白核隐藻和空球藻等，它们与库区化学需氧量密切相关；库区化学需氧量是影响真核浮游生物群落格局的重要环境因子.（2）原核浮游生物群落的主要优势类群为变形菌门；原核生物中相对丰度较大的不动杆菌Acinetobacter是污水污染的指示菌群；群落中起重要作用的Limnohabitans与水体的富营养化密切相关；尽管库区蓝藻相对丰度较低，但与蓝藻关系密切的CL500-29_marine_group和hgcI_clade两类细菌在浮游生物群落中也起着重要作用；原核生物群落中的各类物种均指示丹江口水库的水生态健康存在一定风险，需要加强监测以预防生态环境的恶化.（3）丹江口水库不同区域的浮游生物群落异质性较大，tb-RDA分析显示丹江口的浮游生物群落可以分为丹库型、汉库型和入库支流型，其组间差异要大于组内差异.综上所述，丹江口水库的浮游生物群落具有明显的空间异质性，整个库区的群落结构与水体富营养化、水体有机污染和污水污染等方面相关，需要加强对丹江口库区的水生态监测.;The diversity of plankton community in Danjiangkou Reservoir was investigated, water samples were collected from 9 locations in Danku, Hanku and tributary of Danjiangkou Reservoir in July 2020, based on single molecule real-time sequencing. The 18S and 16S gene were used to explore the diversity and community characteristics of eukaryotic and prokaryotic, respectively. Our study has found several aspects:(1) The dominant species of eukaryotic plankton community belong to Arthropoda, Streptophyta, Chlorophyta and Bacillariophyta. We identified the most widely distributed species with high relative abundance, include Cryptomonas curvata, Cryptomonas pyrenoidifera, Eudorina elegans etc., they all associated with the chemical oxygen demand. Thus, the chemical oxygen demand is the key environmental factor for the eukaryotic plankton community. (2) The dominant species of prokaryotic plankton community belong to Proteobacteria. Acinetobacter with high relative abundance is the indicator of sewage pollution, the important species Limnohabitans is associated with eutrophication. Cyanobacteria showed a low relative abundance, but bacteria associated with cyanobacteria like CL500-29_marine_group and hgcI_clade played a pivotal role in the prokaryotic community. Thus, the bioindicator showed the Danjiangkou Reservoir has risk in ecological health and needs further monitor. (3) The plankton community showed a high heterogeneity in different area, the tb-RDA analysis revealed the plankton community in Danjiangkou Reservoir can be divided into three different types, Danku type, Hanku type and tributary type, the difference was higher between different groups than within group, the roots of the difference between these groups lie in the different richness in the community. To sum up, the plankton community showed obvious spatial heterogeneity in Danjiangkou Reservoir, their community structure is associated with water eutrophication, organic pollution, sewage pollution etc., aquatic ecosystem monitoring should be strengthened urgently.

Few studies have comprehensively investigated the temporal variability in soil microbial communities despite widespread recognition that the belowground environment is dynamic. In part, this stems from the challenges associated with the high degree of spatial heterogeneity in soil microbial communities and because the presence of relic DNA (DNA from dead cells or secreted extracellular DNA) may dampen temporal signals. Here, we disentangle the relationships among spatial, temporal, and relic DNA effects on prokaryotic and fungal communities in soils collected from contrasting hillslopes in Colorado, USA. We intensively sampled plots on each hillslope over 6 months to discriminate between temporal variability, intraplot spatial heterogeneity, and relic DNA effects on the soil prokaryotic and fungal communities. We show that the intraplot spatial variability in microbial community composition was strong and independent of relic DNA effects and that these spatial patterns persisted throughout the study. When controlling for intraplot spatial variability, we identified significant temporal variability in both plots over the 6-month study. These microbial communities were more dissimilar over time after relic DNA was removed, suggesting that relic DNA hinders the detection of important temporal dynamics in belowground microbial communities. We identified microbial taxa that exhibited shared temporal responses and show that these responses were often predictable from temporal changes in soil conditions. Our findings highlight approaches that can be used to better characterize temporal shifts in soil microbial communities, information that is critical for predicting the environmental preferences of individual soil microbial taxa and identifying linkages between soil microbial community composition and belowground processes.IMPORTANCE Nearly all microbial communities are dynamic in time. Understanding how temporal dynamics in microbial community structure affect soil biogeochemistry and fertility are key to being able to predict the responses of the soil microbiome to environmental perturbations. Here, we explain the effects of soil spatial structure and relic DNA on the determination of microbial community fluctuations over time. We found that intensive spatial sampling was required to identify temporal effects in microbial communities because of the high degree of spatial heterogeneity in soil and that DNA from nonliving sources masks important temporal patterns. We identified groups of microbes with shared temporal responses and show that these patterns were predictable from changes in soil characteristics. These results provide insight into the environmental preferences and temporal relationships between individual microbial taxa and highlight the importance of considering relic DNA when trying to detect temporal dynamics in belowground communities.

Microbial communities play an important role in ecological processes through direct or indirect interactions. However, the interspecific interaction pattern of reservoir microorganisms has still received little attention. The Hengshan Reservoir in Jiangsu province was selected as the research area. Surface and deep water samples were collected to respectively explore the response of planktonic microbial community structure and the molecular ecological network to water depth changes, as well as to identify the key species of planktonic microbial communities in different water depths. The results showed that the richness and evenness of planktonic microorganisms in the surface layer were higher than those in the deep layer, and there were significant differences in the community structure of planktonic microorganisms in different depths. Water depth indirectly affected the planktonic microbial community by changing the environmental heterogeneity, among which the indicators such as TOC, NO3-, NH4+, and PO43- had the most significant impact on the planktonic microbial community structure. In addition, the number of nodes and edges of the deep planktonic microbial molecular ecological network were significantly higher than those on the surface, and the type and number of key species in the deep planktonic microbial community were significantly higher than those on the surface, indicating that the network scale of the deep planktonic microbial community was larger; however, the interspecific cooperative relationship and network connectivity of the surface planktonic microbial community were stronger. These results will provide a scientific basis for the study of interspecific interactions of reservoir microbial communities and are of great significance for predicting the ecological law of microorganisms in reservoir ecosystems and the impact of global material cycles.

A mesocosms approach was used to assess the seasonal variability and the effect of oil spills on the structure and dynamics of marine microbial plankton communities in a coastal upwelling system. To this aim, four experiments were conducted during the main characteristic periods of the seasonal cycle in the Ría de Vigo (NW of Spain): spring phytoplankton bloom, summer stratification, autumn upwelling and winter mixing. In each of these experiments, enclosed communities in control and oiled bags were monitored and key variables and rates were measured during 9 days. Temporal changes in community structure and function were interpreted applying a simple NPZD (Nutrients-Phytoplankton-Zooplankton-Detritus) model in which the strategy was to maintain invariant as many model parameters as possible. The analysis of those parameters that were modified to accurately simulate the time evolution of the microbial communities in the mesocosms, provided important information about the main processes influencing the plankton community structure and dynamics in the bags as well as about the effect of oil. This modelling approach allowed assessing the dynamics of the four communities just varying phytoplankton maximum growth rates, bacterial growth efficiencies, microzooplankton grazing rates and phytoplankton sinking rates. Comparison of parameters in control and oiled bags in each period allowed to infer the negligible effect of oil spills on the structure and dynamics of the microbial plankton communities in this coastal upwelling system.

Subsurface microbial communities mediate the transformation and fate of redox sensitive materials including organic matter, metals and radionuclides. Few studies have explored how changing geochemical conditions influence the composition of groundwater microbial communities over time. We temporally monitored alterations in abiotic forces on microbial community structure using 1L in-field bioreactors receiving background and contaminated groundwater at the Oak Ridge Reservation, TN. Planktonic and biofilm microbial communities were initialized with background water for 4 days to establish communities in triplicate control reactors and triplicate test reactors and then fed filtered water for 14 days. On day 18, three reactors were switched to receive filtered groundwater from a contaminated well, enriched in total dissolved solids relative to the background site, particularly chloride, nitrate, uranium, and sulfate. Biological and geochemical data were collected throughout the experiment, including planktonic and biofilm DNA for 16S rRNA amplicon sequencing, cell counts, total protein, anions, cations, trace metals, organic acids, bicarbonate, pH, Eh, DO, and conductivity. We observed significant shifts in both planktonic and biofilm microbial communities receiving contaminated water. This included a loss of rare taxa, especially amongst members of the Bacteroidetes, Acidobacteria, Chloroflexi, and Betaproteobacteria, but enrichment in the Fe- and nitrate- reducing Ferribacterium and parasitic Bdellovibrio. These shifted communities were more similar to the contaminated well community, suggesting that geochemical forces substantially influence microbial community diversity and structure. These influences can only be captured through such comprehensive temporal studies, which also enable more robust and accurate predictive models to be developed.

Planktonic microbial community and biological metabolism in a subtropical drinking water river-reservoir system

The development of oil exploration activities and an increase in shipping in Arctic areas have increased the risk of oil spills in this cold marine environment. The objective of this experimental study was to assess the effect of biostimulation on microbial community abundance, structure, dynamics, and metabolic potential for oil hydrocarbon degradation in oil-contaminated Arctic seawater. The combination of amplicon-based and shotgun sequencing, together with the integration of genome-resolved metagenomics and omics data, was applied to assess microbial community structure and metabolic properties in naphthenic crude oil-amended microcosms. The comparison of estimates for oil-degrading microbial taxa obtained with different sequencing and taxonomic assignment methods showed substantial discrepancies between applied methods. Consequently, the data acquired with different methods was integrated for the analysis of microbial community structure, and amended with quantitative PCR, producing a more objective description of microbial community dynamics and evaluation of the effect of biostimulation on particular microbial taxa. Implementing biostimulation of the seawater microbial community with the addition of nutrients resulted in substantially elevated prokaryotic community abundance (103-fold), a distinctly different bacterial community structure from that in the initial seawater, 1.3-fold elevation in the normalized abundance of hydrocarbon degradation genes, and 12% enhancement of crude oil biodegradation. The bacterial communities in biostimulated microcosms after four months of incubation were dominated by Gammaproteobacterial genera Pseudomonas, Marinomonas, and Oleispira, which were succeeded by Cycloclasticus and Paraperlucidibaca after eight months of incubation. The majority of 195 compiled good-quality metagenome-assembled genomes (MAGs) exhibited diverse hydrocarbon degradation gene profiles. The results reveal that biostimulation with nutrients promotes naphthenic oil degradation in Arctic seawater, but this strategy alone might not be sufficient to effectively achieve bioremediation goals within a reasonable timeframe.

A 2‐week multidisciplinary study of the physical, chemical, and biological mechanisms controlling the initiation of the late summer blooms of the diazotrophic cyanobacteria, Aphanizomenon flos‐aquae Ralfs and Nodularia spumigena Mertens, in the Baltic Sea was carried out in a frontal region at the entrance to the Gulf of Finland in July 1993. The front is formed by inflowing saltier waters of the northern Baltic proper and outflowing fresher waters from the gulf, and its position and shape are largely controlled by wind conditions. In general, the waters of the northern Baltic proper are less stratified than the outflowing lesssaline waters. At the time of the study, the two major water masses differed in terms of phytoplankton community structure, both at species level and at the level of functional groups. Wind‐induced vertical mixing was instrumental in bringing nutrient pulses to the upper mixed layer in the less‐stratified, high‐saline water mass. Nutrient pulses were followed by enhancement of primary productivity and assimilation number (primary productivity/Chl a) in cyanobacterial (> 20 µm) and flagellate (<20 µm) size fractions. It is proposed that mesoscale blooms of A. flos‐aquae benefit from the nutrient‐pulsing events. Calm weather and solar heating, as reflected by rising temperatures in the upper mixed layer and overriding of water masses in the frontal region, resulted in substantial shallowing of the upper mixed layer, which initiated the bloom of N. spumigena.

Benthic microbial communities are a vital component of coastal subtidal zones, playing an essential role in nutrient cycling and energy flow, and are fundamental to maintaining the stability and functioning of marine ecosystems. However, the response of benthic prokaryotic and eukaryotic microbial communities to environmental changes remains poorly understood. Herein, we conducted a nearly semimonthly annual sampling survey to investigate the temporal patterns and underlying mechanisms of benthic prokaryotic and eukaryotic microbial communities in the subtidal sediments of Sanshan Island, situated in the eastern Laizhou Bay of the Bohai Sea, China. The results showed that the temporal variations in benthic microbial communities followed a distinct seasonal pattern, with turnover playing a more dominant role in community succession. Nonetheless, contrasting temporal variations were observed in the alpha diversity of benthic prokaryotic and eukaryotic microbial communities, as well as in the dominant taxa across different microbial communities. Water temperature, dissolved oxygen, electrical conductivity, salinity, total nitrogen (TN), NH4+, and PO43- were identified as the predominant environmental drivers. The assembly of benthic microbial communities was driven by different ecological processes, in which stochastic processes mainly shaped the benthic prokaryotic communities, while deterministic processes dominated the assembly of benthic eukaryotic microbial communities. Interactions within benthic microbial communities were primarily characterized by mutualistic or cooperative relationships, but the ability of prokaryotic and eukaryotic microbial communities to maintain stability under environmental disturbances showed notable differences. These results shed light on the temporal dynamics and potential driving mechanisms of benthic prokaryotic and eukaryotic microbial communities under environmental disturbances, highlighting the distinct roles of prokaryotic and eukaryotic communities in coastal subtidal zones and providing valuable insights for the management and conservation of coastal subtidal marine ecosystems.

Plankton distribution within a young cyclonic eddy off south-western Madagascar

Phytoplankton communities are increasingly subject to multiple stressors of natural or anthropogenic origin. The cumulative effect of these stressors, however, may vary considerably from the sum of impacts from individual stressors. Nonlinear effects such as changes in community traits can either boost up (synergistic) or weaken (antagonistic) single stressors. Despite previous empirical studies and meta analyses on the interaction types of various multiple stressors, a more fundamental understanding of cumulative effects is lacking. To fill this gap, we here propose a new theoretical framework that is centered on the concept of interaction traits and their trade-offs. The framework is applied to a novel size-based plankton model resolving multi-species phytoplankton-nutrients-detritus-zooplankton dynamics within the upper mixed layer. The model is validated using data from a series of outdoor mesocosm experiments. In the direct aftermath of single perturbations that increase net growth rate, here nutrient enrichment and grazer removal, the simulated phytoplankton community undergoes structural changes as visible in altered community traits. These temporal variations explain why the multiple stressor interaction switches from antagonistic to synergistic as compensatory trait variations reduce over time of the experiment. This finding can be generalized within our trait-based explanatory framework to mechanistically assess and predict effects of other stressor combinations and for other organism groups.

Interannual variability of the phytoplankton community by the changes in vertical mixing and atmospheric deposition in the Ulleung Basin, East Sea: A modelling study

<p>Seasonal variability is a powerful component of the spatio-temporal dynamics of plankton communities, especially in the regions with oxygen-depleted waters. The Arabian Sea and the Black Sea are typical representatives of these regions. In both, the dinoflagellate Noctiluca scintillans (Macartney) Kofoid & Swezy, 1921, is one of the abundant plankton species which forms algal blooms. Sampling on coastal stations in the upper mixed layer by the plankton nets with the 120-140 µm mesh size was carried out in 2004-2010. Monthly data were averaged over years. A comparison of seasonal patterns of Noctiluca abundance pointed to the persistence of a bimodal seasonal cycle in both regions. The major peak was observed during spring in the Black Sea and during the winter (Northeast) monsoon in the Arabian Sea. The timing of the second (minor) peak was different over regions as well. This peak was modulated by advection of seasonally fluctuating velocity of coastal currents which transport waters enriched by nutrients by coastal upwelling. The abundance of Noctiluca of the major peak (with the concentration around 1.5*10<sup>6</sup> cells m<sup>-3</sup>) was from one to two orders as much high in the western Arabian Sea compared to the northern Black Sea. The remotely sensed chlorophyll-a concentration during the time of the major seasonal peak exhibited a fivefold difference over these regions. In terms of nutrient<sub></sub>concentration in the upper mixed layer (in particular, nitrates and silicates), a difference of about one order of magnitude was observed.</p>

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 55:81-93 (2009) - DOI: https://doi.org/10.3354/ame01283 Influence of allochthonous matter on microbial community structure and function in an upwelling system off the northwest Iberian Peninsula Eva Teira*, María Aranguren-Gassis, Jose González, Sandra Martínez-García, Patricia Pérez, Pablo Serret Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, Campus Lagoas-Marcosende, 36310 Vigo, Spain *Email: teira@uvigo.es ABSTRACT: The input of allochthonous matter of continental origin to coastal zones globally may cause changes in the activity (function) as well as the taxonomic composition (structure) of the microbial plankton community. The goal of the present study was the simultaneous analysis of microbial plankton community structure (size-fractionated phytoplankton biomass, bacterial community composition) and function (particulate and dissolved primary production, bacterial production, microbial plankton community respiration) in the northwest Iberian coastal transition zone during a dry (February 2005) and a rainy (October 2005) period. An influence of freshwater input was observed in October, even at an offshore site, but not in February. We found an autotrophic community dominated by picophytoplankton during both sampling periods. In contrast, the bacterial groups Beta- and Gammaproteobacteria were significantly more abundant during the high precipitation period. Primary production rates were low and similar during both sampling periods; however, bacterial production was 8-fold and community respiration was 3-fold higher in October than in February. Consequently, the microbial community metabolism was net autotrophic in February and net heterotrophic in October. The high precipitation and the significant presence of bacteria belonging to the Betaproteobacteria, typical for freshwater systems, in October compared to February, strongly suggest an influence of material of continental origin on microbial metabolism in this coastal transition zone. KEY WORDS: Microbial plankton structure · Primary production · Bacterial production · Respiration · Allochthonous matter · NW Iberian Peninsula Full text in pdf format PreviousNextCite this article as: Teira E, Aranguren-Gassis M, González J, Martínez-García S, Pérez P, Serret P (2009) Influence of allochthonous matter on microbial community structure and function in an upwelling system off the northwest Iberian Peninsula. Aquat Microb Ecol 55:81-93. https://doi.org/10.3354/ame01283 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 55, No. 1. Online publication date: April 06, 2009 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2009 Inter-Research.