scholarly journals Water and Sediment Bacterial Communities in a Small Mediterranean, Oxygen-Stratified, Saline Lake (Lake Alboraj, SE Spain)

2021 ◽  
Vol 11 (14) ◽  
pp. 6309
Author(s):  
Yolanda Espín ◽  
Alfonso Menchén ◽  
José Luis Moreno ◽  
David Sanz ◽  
Manuel Álvarez-Ortí ◽  
...  
Keyword(s):  
Water Column ◽  
Bacterial Communities ◽  
Ecological Status ◽  
Natura 2000 ◽  
Rrna Gene ◽  
Natura 2000 Network ◽  
Se Spain ◽  
Water And Sediment ◽  
Different Depths ◽  
Physical And Chemical

Lake Alboraj, located in southeast Spain, was declared natural Microreserve and included into European Natura-2000 Network due to its contribution to environmental heritage. Unfortunately, the ecological status of the lake has changed dramatically, mainly due to the lowering of water table caused by groundwater abstractions for irrigation. It is a permanent small karstic lake whose surface has reduced in the last decades to nearly the third part of its historical water level. The water column shows a marked seasonal oxycline, that splits an aerobic upper layer (epilimnion) from an anaerobic layer below (hypolimnion). Sequencing 16S rRNA gene amplicons and applying chemical tools at epilimnion, hypolimnion and sediment, showed a clear gradient in the bacterial community structure, which support the co-existence of assimilatory and dissimilatory microbial mediated reactions. Results allows to infer that microbial stratification could provide various physical and chemical environments at different depths in the water column related to biogeochemical reactions providing N-S-C- recycling processes.

scholarly journals Dispersion and Intersection of Hydrothermal Plumes in the Manus Back-Arc Basin, Western Pacific

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Zhigang Zeng ◽  
Xiaoyuan Wang ◽  
Bramley J. Murton ◽  
Haiyan Qi ◽  
Berit Lehrmann ◽  
...  
Keyword(s):  
Water Column ◽  
Ph Value ◽  
Chemical Properties ◽  
Hydrothermal Systems ◽  
Pacmanus Hydrothermal Field ◽  
Different Depths ◽  
Hydrothermal Plumes ◽  
Back Arc ◽  
Physical And Chemical ◽  
Fluid Sources

The composition of hydrothermal plumes reflects the physical and chemical characteristics of seafloor hydrothermal fluids, which in turn reflects the host rock and subseafloor reaction conditions as well as the water column processes that act to alter the plumes as they disperse and age. Here, we show that the turbidity, current, pH value, dissolved Fe (dFe), and dissolved Mn (dMn) compositions of hydrothermal plumes can be used to understand the spatial distribution and source of hydrothermal systems in the submarine geological environment. Data were obtained from 18 hydrocast stations, among which the water column samples were collected at 8 stations during the MANUS cruise of R/V KEXUE in 2015. The results showed that the Satanic Mills plume and Fenway plume rose approximately 140 m and 220 m above the seafloor, respectively. In the Satanic Mills plume, dFe remained longer than dMn during lateral plume dispersal. There was a clear intersection of the Satanic Mills plume and Fenway plume between 1625 m and 1550 m in the PACMANUS hydrothermal field, and the varied dispersion trends of the mixed plumes were affected by current velocities at different depths. The physical and chemical properties of the seawater columns in the Manus Basin were affected by the input of high-Mn, high-Fe, and low-Mg vent fluids. The turbidity and dFe, dMn, and dissolved Mg concentrations in the sections of the plumes proximal to the Satanic Mills, Fenway, and Desmos vent sites were generally higher (turbidity, Mn, and Fe) and lower (Mg) than those in the sections of the plumes that were more distal from the vent sites. This implied that the plumes proximal to their vent fluid sources, which were interpreted to have relatively young ages, dispersed chemically over time, and their concentrations became more similar to those of the plumes that were more distal from their vent fluid sources.

scholarly journals Silicon application and related changes in soil bacterial community dynamics reduced ginseng black spot incidence in Panax ginseng in a short-term study

2019 ◽  
Author(s):  
Meijia Li ◽  
Qiuxia Wang ◽  
Zhengbo Liu ◽  
Xiaoxi Pan ◽  
Yayu Zhang
Keyword(s):  
Community Structure ◽  
Bacterial Community ◽  
Panax Ginseng ◽  
Bacterial Communities ◽  
Community Dynamics ◽  
Bacterial Flora ◽  
Black Spot ◽  
Rrna Gene ◽  
Short Term ◽  
Physical And Chemical

Abstract Background This study analyzed the effect of silicon (Si) application on the occurrence of ginseng black spot caused by Alternaria panax . We explored the differences in soil physical and chemical factors and microbial community structure following Si application as well as the key factors that affected the occurrence of ginseng black spot in soil. Potted Panax ginseng plants were used to assess the effect of Si treatment on ginseng black spot. Soil physical and chemical properties were comprehensively analyzed. Bacterial communities were analyzed using Illumina HiSeq sequencing targeting the 16S rRNA gene. Results After inoculation with A. panax , the morbidity (and morbidity index) of ginseng with and without Si was 52% (46) and 83% (77), respectively. Soil physical and chemical analysis showed that under the ginseng black spot inoculation, bacterial communities were mainly affected by pH and available potassium, followed by ammonium nitrogen and available Si. NMDS and PLS-DA analyses and the heat maps of relative abundance revealed that Si application elevated the resistance of ginseng black spot as regulated by the abundance and diversity of bacterial flora in rhizosphere soils. Heatmap analysis at the genus level revealed that A. panax + Si inoculations significantly increased the soil community abundance of Sandaracinus , Polycyclovorans , Hirschia , Haliangium , Nitrospira , Saccharothrix , Aeromicrobium , Luteimonas , and Rubellimicrobium and led to a bacterial community structure with relative abundances that were significantly similar to that of untreated soil. Conclusions Short-term Si application also significantly regulated the structural impact on soil microorganisms caused by ginseng black spot. Our findings indicated that Si applications may possibly be used in the prevention and treatment of ginseng black spot.

scholarly journals Integrating the Water Framework Directive into the Habitats Directive: analysis of distribution patterns of lacustrine EU habitats in lakes of Lombardy (northern Italy)

2017 ◽  
Author(s):  
Rossano Bolpagni ◽  
Mattia M. Azzella ◽  
Chiara Agostinelli ◽  
Andrea Beghi ◽  
Eugenia Bettoni ◽  
...  
Keyword(s):  
Water Framework Directive ◽  
Ecological Status ◽  
Natura 2000 ◽  
Northern Italy ◽  
Habitats Directive ◽  
The European Union ◽  
Aquatic Habitats ◽  
Eutrophic Lakes ◽  
Natura 2000 Network ◽  
Use Of Resources

<p>The existence of strong potential synergies between the Water Framework Directive (WFD) and the Habitats Directive (HD) is widely acknowledged. Indeed, ensuring favourable conservation conditions for aquatic habitats and species of conservation concern is closely related to the achievement of a good ecological status in water bodies. However, since these two sets of European laws are generally applied without any coordination, an inefficient use of resources may adversely affect their goals. The main negative outcome is an increase in the cost of monitoring programs for collecting data in nature (<em>i.e.</em>, physical and chemical parameters, species and habitats, plant communities). The use of macrophytes as a bioindicator, as imposed by the WFD, may instead help to integrate data on aquatic EU habitats and enhance knowledge of such habitats outside the Natura 2000 network. The aim of present study was to evaluate the usefulness of data collected in WFD monitoring surveys as a means of inferring the occurrence and the distribution of lacustrine aquatic habitats in countries belonging to the European Union (EU). The main aim of the analysis was to identify the depth gradient distribution of diagnostic macrophyte <em>taxa</em> in two EU habitats (3140, <em>i.e.</em>, <em>Chara</em>-dominated benthic communities, and 3150, <em>i.e.</em>, natural eutrophic lakes) using data collected in lakes in Lombardy (northern Italy), some of which are included in the Natura 2000 network (10 out 16). While recognizing the limitations of the data collected within the two frameworks, the results confirmed the marked usefulness of WFD data as a means of enhancing the knowledge available on lacustrine aquatic habitats in the EU. WFD data can actively help to improve the basic information on aquatic habitats, thereby more effectively supporting regional strategies for biodiversity conservation as well as recovery programs.</p><p> </p>

scholarly journals Digestive gland microbiome of Pleurobema cordatum: mesocosms induce dysbiosis

2020 ◽  
Vol 86 (4) ◽  
pp. 280-289
Author(s):  
Alison K Aceves ◽  
Paul D Johnson ◽  
Carla L Atkinson ◽  
Brian C van Ee ◽  
Stephen A Bullard ◽  
...  
Keyword(s):  
Digestive Gland ◽  
Gut Microbiome ◽  
Bacterial Communities ◽  
16S Rrna Gene Sequencing ◽  
Rrna Gene ◽  
Artificial Rearing ◽  
Tennessee River ◽  
Wasting Syndrome ◽  
Water And Sediment ◽  
Rrna Gene Sequencing

ABSTRACT Herein, we characterized the digestive gland (‘gut’) bacterial community (microbiome) of the Ohio pigtoe, Pleurobema cordatum (Rafinesque, 1820), using 16S rRNA gene sequencing. Two populations were compared: wild P. cordatum (n = 5) from the Tennessee River and P. cordatum (n = 9) relocated to artificial mesocosms and exposed to various thermal regimes for 2 weeks. We also characterized the bacterial communities from the habitat (water and sediment) of these wild and mesocosm-held populations. The gut microbiome of wild P. cordatum was dominated by members of the bacterial phylum Tenericutes (72%). By contrast, the gut microbiome of mesocosm-held P. cordatum was dominated by members of the bacterial phylum Proteobacteria (64%). We found no temperature-associated difference in the gut microbiome of mesocosm-held P. cordatum. The bacterial communities of water and sediment from the Tennessee River were diverse and distinct from those of the studied mussels. By contrast, the bacterial communities of water and sediment in the mesocosms were dominated by Proteobacteria. These results suggest that when the studied mussels were moved into artificial rearing environments, their gut microbiome shifted to reflect that of their habitat (i.e. an increase in Proteobacteria). Moreover, the abundance of Tenericutes (also previously reported in other unionids) was reduced from 72% in wild mussels to 3% in mesocosm-held mussels. As a result, we think that mesocosm-held P. cordatum became dysbiotic, which could explain the observed wasting syndrome and associated trickling mortalities in captive P. cordatum.

scholarly journals Evidence for Vertical Transmission of Bacterial Symbionts from Adult to Embryo in the Caribbean Sponge Svenzea zeai

2009 ◽  
Vol 75 (19) ◽  
pp. 6147-6156 ◽  
Author(s):  
On On Lee ◽  
Pui Yi Chui ◽  
Yue Him Wong ◽  
Joseph R. Pawlik ◽  
Pei-Yuan Qian
Keyword(s):  
Water Column ◽  
Clone Library ◽  
Bacterial Communities ◽  
Denaturing Gradient Gel Electrophoresis ◽  
Rrna Gene ◽  
Vertical Transfer ◽  
Clone Library Analysis ◽  
Gradient Gel Electrophoresis ◽  
The Caribbean ◽  
Surrounding Seawater

ABSTRACT The Caribbean reef sponge Svenzea zeai was previously found to contain substantial quantities of unicellular photosynthetic and autotrophic microbes in its tissues, but the identities of these symbionts and their method of transfer from adult to progeny are largely unknown. In this study, both a 16S rRNA gene-based fingerprinting technique (denaturing gradient gel electrophoresis [DGGE]) and clone library analysis were applied to compare the bacterial communities associated with adults and embryos of S. zeai to test the hypothesis of vertical transfer across generations. In addition, the same techniques were applied to the bacterial community from the seawater adjacent to adult sponges to test the hypothesis that water column bacteria could be transferred horizontally as sponge symbionts. Results of both DGGE and clone library analysis support the vertical transfer hypothesis in that the bacterial communities associated with sponge adults and embryos were highly similar to each other but completely different from those in the surrounding seawater. Sequencing of prominent DGGE bands and of clones from the libraries revealed that the bacterial communities associated with the sponge, whether adult or embryo, consisted of a large proportion of bacteria in the phyla Chloroflexi and Acidobacteria, while most of the sequences recovered from the community in the adjacent water column belonged to the class Alphaproteobacteria. Altogether, 21 monophyletic sequence clusters, comprising sequences from both sponge adults and embryos but not from the seawater, were identified. More than half of the sponge-derived sequences fell into these clusters. Comparison of sequences recovered in this study with those deposited in GenBank revealed that more than 75% of S. zeai-derived sequences were closely related to sequences derived from other sponge species, but none of the sequences recovered from the seawater column overlapped with those from adults or embryos of S. zeai. In conclusion, there is strong evidence that a dominant proportion of sponge-specific bacteria present in the tissues of S. zeai are maintained through vertical transfer during embryogenesis rather than through acquisition from the environment (horizontal transfer).

scholarly journals Silicon application and related changes in soil bacterial community dynamics reduced ginseng black spot incidence in Panax ginseng in a short-term study

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Meijia Li ◽  
Qiuxia Wang ◽  
Zhengbo Liu ◽  
Xiaoxi Pan ◽  
Yayu Zhang
Keyword(s):  
Community Structure ◽  
Bacterial Community ◽  
Panax Ginseng ◽  
Bacterial Communities ◽  
Community Dynamics ◽  
Bacterial Flora ◽  
Black Spot ◽  
Rrna Gene ◽  
Short Term ◽  
Physical And Chemical

Abstract Background This study analyzed the effect of silicon (Si) application on the occurrence of ginseng black spot caused by Alternaria panax. We explored the differences in soil physical and chemical factors and microbial community structure following Si application as well as the key factors that affected the occurrence of ginseng black spot in soil. Potted Panax ginseng plants were used to assess the effect of Si treatment on ginseng black spot. Soil physical and chemical properties were comprehensively analyzed. Bacterial communities were analyzed using Illumina HiSeq sequencing targeting the 16S rRNA gene. Results After inoculation with A. panax, the morbidity (and morbidity index) of ginseng with and without Si was 52% (46) and 83% (77), respectively. Soil physical and chemical analysis showed that under the ginseng black spot inoculation, bacterial communities were mainly affected by pH and available potassium, followed by ammonium nitrogen and available Si. NMDS and PLS-DA analyses and the heat maps of relative abundance revealed that Si application elevated the resistance of ginseng black spot as regulated by the abundance and diversity of bacterial flora in rhizosphere soils. Heatmap analysis at the genus level revealed that A. panax + Si inoculations significantly increased the soil community abundance of Sandaracinus, Polycyclovorans, Hirschia, Haliangium, Nitrospira, Saccharothrix, Aeromicrobium, Luteimonas, and Rubellimicrobium and led to a bacterial community structure with relative abundances that were significantly similar to that of untreated soil. Conclusions Short-term Si application also significantly regulated the structural impact on soil microorganisms caused by ginseng black spot. Our findings indicated that Si applications may possibly be used in the prevention and treatment of ginseng black spot.

scholarly journals INFLUENCE OF PHOSPHORUS-CONTAMINATED SEDIMENTS IN THE ABUNDANCE OF POTENTIALLY TOXIC PHYTOPLANKTON ALONG THE SFAX COASTS (GULF OF GABES, TUNISIA)

2019 ◽  
Vol 4 (4) ◽  
pp. 458-470 ◽  
Author(s):  
Wafa Feki-Sahnoun ◽  
Hasna Njah ◽  
Nouha Barraj ◽  
Mabrouka Mahfoudi ◽  
Fourat Akrout ◽  
...  
Keyword(s):  
Water Column ◽  
Best Management Practices ◽  
Management Practices ◽  
Monitoring Program ◽  
Ecological Status ◽  
Organic Load ◽  
Toxic Phytoplankton ◽  
Benthic Dinoflagellates ◽  
Phytoplankton Monitoring ◽  
Physical And Chemical

This is the first work performed in the shellfish production area located along the Sfax coasts (southern Tunisia) on the spatial and temporal patterns of toxic phytoplankton. It relates the excessive introduction of phosphorus in coastal waters from sediments contaminated with that nutrient. A multivariate approach was applyed using data derived from the National Phytoplankton Monitoring Program (REPHY) (2006-2009). We also examine if there is a direct relationship between the abundance of toxic phytoplankton and physical and chemical parameters. This study is based on phytoplankton composition and abundance, as well as physical and chemical data to evaluate the ecological status of the Sfax coasts, at shellfish farms. A total of 13 taxa included in the Intergovernmental Oceanographic Commission (IOC) toxic algae checklist and well-known bloom formers were identified in REPHY. Higher nutrient spring samples were distinguished from those of lower nutrient summer waters. The Redundancy Analysis (RDA) separated the toxic species into two groups related to nutrients availability. The large amounts of phosphorus and organic matter affected the toxic phytoplankton structure, due to the pollution of chemical origin underlining an organic load hardly biodegradable in Sfax coasts. Many of these species recorded in the water column were benthic dinoflagellates, a fact that could be explained by the resuspension of these organisms by hydrodynamics. The knowledge obtained in this study can be used to develop best management practices of the sediment compartment as well as the water column, which is crucial in the framework of any phytoplankton monitoring program. INFLUÊNCIA DE SEDIMENTOS CONTAMINADOS POR FÓSFORO NA ABUNDÂNCIA DE FITOPLANCTÔNPOTENCIALMENTE TÓXICO NAS COSTAS DE SFAX (GOLFO DE GABES, TUNÍSIA)ResumoEste é o primeiro trabalho realizado na área de produção de moluscos, situada ao longo das costas de Sfax (sul da Tunísia) que relaciona os padrões espaciais e temporais do fitoplâncton tóxico com a introdução excessiva de fósforo nas águas costeiras a partir da remobilização de sedimentos contaminados com esse nutriente. Foi usada uma abordagem multivariada com Base em dados derivados do Programa Nacional de Monitoramento de Fitoplâncton (REPHY) (2006-2009). Também foi analisada a relação entre a abundância de fitoplâncton tóxico e parâmetros físico-químicos. Este estudo baseia-se na composição e abundância de fitoplâncton, além de dados físicos e químicos para avaliar o estado ecológico das costas de Sfax, em áreas de cultivo de moluscos. Um total de 13 táxons incluídos na lista de algas tóxicas da Comissão Intergovernamental Oceanográfica e espécies geradoras de blooms de fitoplanctôn, bem conhecidas, foram identificados. Amostras de primavera, associadas a águas com mais nutrientes foram diferenciadas das amostras de verão em que a água tem teores mais baixos de nutrientes. A Análise de Redundância (RDA) separou as espécies tóxicas em dois grupos relacionados à disponibilidade de nutrientes. Os resultados revelaram que teores elevados de fósforo e matéria orgânica afetaram a estrutura do fitoplâncton tóxico, devido à poluição de origem química subjacente a uma carga orgânica dificilmente biodegradável nas costas de Sfax. Muitas das espécies encontradas na coluna de água são dinoflagelados bentônicos, fato que pode ser explicado pela ressuspensão desses organismos pelo hidrodinamismo. Os conhecimentos obtidos neste trabalho podem ser usados para desenvolver melhores práticas de gerenciamento costeiro e programas de monitoramento de fitoplâncton. Palavras Chave: Costas do sul de Sfax. Microalgas prejudiciais. Análise multivariada. Parâmetros físicos e químicos.

scholarly journals Integrating the Water Framework Directive into the Habitats Directive: Analysis of distribution patterns of lacustrine EU habitats in lakes of Lombardy (northern Italy)

2017 ◽  
Vol 76 (s1) ◽  
Author(s):  
Rossano Bolpagni ◽  
Mattia M. Azzella ◽  
Chiara Agostinelli ◽  
Andrea Beghi ◽  
Eugenia Bettoni ◽  
...  
Keyword(s):  
Water Framework Directive ◽  
Ecological Status ◽  
Natura 2000 ◽  
Northern Italy ◽  
Habitats Directive ◽  
The European Union ◽  
Aquatic Habitats ◽  
Eutrophic Lakes ◽  
Natura 2000 Network ◽  
Use Of Resources

The existence of strong potential synergies between the Water Framework Directive (WFD) and the Habitats Directive (HD) is widely acknowledged. Indeed, ensuring favourable conservation conditions for aquatic habitats and species of conservation concern is closely related to the achievement of a good ecological status in water bodies. However, since these two sets of European laws are generally applied without any coordination, an inefficient use of resources may adversely affect their goals. The main negative outcome is an increase in the cost of monitoring programs for collecting data in nature (i.e., physical and chemical parameters, species and habitats, plant communities). The use of macrophytes as a bioindicator, as imposed by the WFD, may instead help to integrate data on aquatic EU habitats and enhance knowledge of such habitats outside the Natura 2000 network. The aim of present study was to evaluate the usefulness of data collected in WFD monitoring surveys as a means of inferring the occurrence and the distribution of lacustrine aquatic habitats in countries belonging to the European Union (EU). The main aim of the analysis was to identify the depth gradient distribution of diagnostic macrophyte taxa in two EU habitats (3140, i.e., Chara-dominated benthic communities, and 3150, i.e., natural eutrophic lakes) using data collected in lakes in Lombardy (northern Italy), some of which are included in the Natura 2000 network (10 out 16). While recognizing the limitations of the data collected within the two frameworks, the results confirmed the marked usefulness of WFD data as a means of enhancing the knowledge available on lacustrine aquatic habitats in the EU. WFD data can actively help to improve the basic information on aquatic habitats, thereby more effectively supporting regional strategies for biodiversity conservation as well as recovery programs. 

scholarly journals Planctomycetes as a Vital Constituent of the Microbial Communities Inhabiting Different Layers of the Meromictic Lake Sælenvannet (Norway)

2020 ◽  
Vol 8 (8) ◽  
pp. 1150
Author(s):  
Julia E. Storesund ◽  
Anders Lanzèn ◽  
Eva-Lena Nordmann ◽  
Hilde Rief Armo ◽  
Olga Maria Lage ◽  
...  
Keyword(s):  
16S Rrna ◽  
16S Rrna Gene ◽  
Water Column ◽  
Meromictic Lake ◽  
Stress Factors ◽  
Rrna Gene ◽  
Gene Sequences ◽  
16S Rrna Gene Sequences ◽  
Chemical Gradient ◽  
Different Depths

Meromictic lakes are permanently stratified lakes that display steep gradients in salinity, oxygen and sulphur compounds tightly linked to bacterial community structure and diversity. Lake Sælenvannet is a meromictic lake located south of Bergen, Norway. The 26 m deep lake is connected to the open sea and permanently stratified into two layers separated by a chemocline. The upper water layer is brackish with major input from water runoff from the surroundings. The bottom layer consists of old saline water with low or no oxygen concentrations. Bacteria from phylum Planctomycetes are reported to be ubiquitous in lake environments. They are involved in the degradation of complex carbon sources in aquatic environments and are also linked to anaerobic processes such as fermentation and sulphur reduction. To study Planctomycete distribution along a chemical gradient, we sampled the water column throughout Lake Sælenvannet in 2012 and profiled the microbial community using 16S rRNA amplicon sequencing (metabarcoding) with 454 pyrosequencing. Planctomycetes related 16S rRNA gene sequences were found to be present both in the oxic and anoxic parts of the lake and showed an uneven distribution throughout the water column, with the highest relative abundance of 10% found in the saline anoxic layer at 15 m depth. In a follow-up study in 2014, samples from eight different depths were collected for enrichment and isolation of novel Planctomycetes. This study resulted in successful isolation in pure culture of 10 isolates affiliated to four different genera from the family Planctomycetaceae. One strain closely related to Blastopirellula cremea was isolated from 9 m depth, and two novel strains affiliated to the genera Stieleria and Gimesia were isolated at 7 and 9 m depths, respectively. Furthermore, seven isolates with identical 16S rRNA gene sequences were retrieved from seven different depths which varied greatly in salinity and chemical composition. These isolates likely represent a new species affiliated to Rubinisphaera. The adaptation of this novel Planctomycete to water depths spanning the entire chemical gradient could indicate a high phenotypic plasticity and/or a very efficient survival strategy. Overall, our results show the presence of a diverse group of Planctomycetes in Lake Sælenvannet, with a strong potential for novel adaptations to chemical stress factors.

scholarly journals Variability of Microbial Communities in Two Long-term Ice-covered Freshwater Lakes in the Subarctic Region of Yakutia, Russia

2021 ◽  
Author(s):  
Yulia Robertovna Zakharova ◽  
Maria Victorovna Bashenkhaeva ◽  
Yuri Pavlovich Galachyants ◽  
Darya Petrovna Petrova ◽  
Irina Victorovna Tomberg ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Water Column ◽  
Bacterial Communities ◽  
Heterotrophic Bacteria ◽  
Nitrogen Concentration ◽  
Ice Cover ◽  
Rrna Gene ◽  
Subarctic Lakes ◽  
Subarctic Region

Abstract Although under-ice microbial communities are subject to a cold environment, low concentrations of nutrients, and a lack of light, they nevertheless take an active part in biogeochemical cycles. However, we still lack an understanding of how high their diversity is and how these communities are distributed during the long-term ice-cover period. Here we assessed for the first time the composition and distribution of microbial communities during the ice-cover period in two subarctic lakes (Labynkyr and Vorota) located in the area of the lowest temperature in the Northern Hemisphere. The diversity distribution and abundance of main bacterial taxa, and the composition of microalgae, varied by time and habitat. The 16S rRNA gene sequencing method revealed, in general, a high diversity of bacterial communities where Proteobacteria (~59%) and Actinobacteria (~11%) prevailed. There were significant differences between the communities of the lakes: Chthoniobacteraceae, Moraxellaceae, and Pirellulaceae were abundant in Lake Labynkyr, while Cyanobacteria, Oligoflexales, Ilumatobacteraceae, and Methylacidiphilaceae were more abundant in Lake Vorota. The most abundant families were evenly distributed in April, May and June their contribution was different in different habitats. Moraxellaceae, Ilumatobacteraceae dominated in April in the water column, while Sphingomonadaceae dominated both in water column and on the ice bottom. In May, the number of Comamonadaceae increased and reached the maximum in June, while Cyanobacteria, Oxalobacteraceae and Pirellulaceae followed. We found a correlation of the structure of bacterial communities with snow thickness, рН, total nitrogen concentration, and conductivity. We isolated psychrophilic heterotrophic bacteria both from dominating and minor taxa of the communities studied. This allowed for specifying their ecological function in the under-ice communities. These findings will advance our knowledge of the under-ice microbial life.

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