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"freshwater lakes"
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Our ancient lakes : a natural history
\"An introduction to the biodiversity of ancient lakes, explaining the surprising, often controversial findings ancient lake research is yielding about the formation and persistence of species\"-- Provided by publisher.
Book
Spatiotemporal dynamics of giant viruses within a deep freshwater lake reveal a distinct dark-water community
Giant viruses (GVs) significantly regulate the ecological dynamics of diverse ecosystems. Although metagenomics has expanded our understanding of their diversity and ecological roles played in marine environments, little is known about GVs of freshwater ecosystems. Most previous studies have employed short-read sequencing and therefore resulted in fragmented genomes, hampering accurate assessment of genetic diversity. We sought to bridge this knowledge gap and overcome previous technical limitations. We subjected spatiotemporal (2 depths × 12 months) samples from Lake Biwa to metagenome–assembled genome reconstruction enhanced by long-read metagenomics. This yielded 293 GV metagenome-assembled genomes. Of these, 285 included previously unknown species in five orders of nucleocytoviruses and the first representatives of freshwater mirusviruses, which exhibited marked divergence from marine-derived lineages. The good performance of our long-read metagenomic assembly was demonstrated by the detection of 42 (14.3%) genomes composed of single contigs with completeness values >90%. GVs were partitioned across water depths, with most species specific to either the sunlit epilimnion or the dark hypolimnion. Epilimnion-specific members tended to be transient and exhibit short and intense abundance peaks, in line with the fact that they regulate the surface algal blooms. During the spring bloom, mirusviruses and members of three nucleocytovirus families were among the most abundant viruses. In contrast, hypolimnion-specific ones, including a mirusvirus genome, were typically more persistent in the hypolimnion throughout the water-stratified period, suggesting that they infect hosts specific to the hypolimnion and play previously unexplored ecological roles in dark water microbial ecosystems.
Journal Article
Rivers and lakes
This book looks at the world's rivers and lakes and how animals and plants have adapted to live in and around fresh water..
Book
Variability of Microbial Communities in Two Long-Term Ice-Covered Freshwater Lakes in the Subarctic Region of Yakutia, Russia
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 as well as 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 (~ 45%) and Actinobacteria (~ 21%) prevailed. There were significant differences between the communities of the lakes: Chthoniobacteraceae, Moraxellaceae, and Pirellulaceae were abundant in Lake Labynkyr, while Cyanobiaceae, 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. In April, Moraxellaceae and Ilumatobacteraceae were the most abundant in the water column, while Sphingomonadaceae was abundant both in water column and on the ice bottom. In May, the abundance of Comamonadaceae increased and reached the maximum in June, while Cyanobiaceae, Oxalobacteraceae, and Pirellulaceae followed. We found a correlation of the structure of bacterial communities with snow thickness, pH, Nmin 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.
Journal Article
Mysis segerstralei, an unexpected but important prey for resident Arctic charr (Salvelinus alpinus) in a Svalbard lake
Mysis segerstralei is distributed over a wide geographic area and in habitats with a variety of salinity conditions, including marine and brackish waters around Svalbard. The species has seldom been found in freshwater lakes, and the discovery of M. segerstralei in Lake Pulmankijärvi at the border between Northeastern Norway and Finland, may represent the single known freshwater occurrences in western Europe. Svalbard lake systems are characterized by very low water temperatures, long-term ice cover, and low levels of nutrients. Food is thus limited, and chironomids generally dominate the stomach contents in Arctic charr, the only freshwater fish species on Svalbard. Based on several surveys in more than 30 of Svalbard lakes over many decades, M. segerstralei has only been found as food for Arctic charr in Lake Vårfluesjøen. In a later fishery survey, we studied the diet of Arctic charr in this lake. The stomach contents from Arctic charr sampled in the profundal habitats were dominated by M. segerstralei, but the species was also among the most frequent prey items in the littoral and pelagic habitats. This unexpected occurrence of M. segerstralei demonstrates the high importance of mysids even in a low-productive, High Arctic lake.
Journal Article
Ice Thickness Assessment of Non-Freshwater Lakes in the Qinghai–Tibetan Plateau Based on Unmanned Aerial Vehicle-Borne Ice-Penetrating Radar: A Case Study of Qinghai Lake and Gahai Lake
Ice thickness has a significant effect on the physical and biogeochemical processes of a lake, and it is an integral focus of research in the field of ice engineering. The Qinghai–Tibetan Plateau, known as the Third Pole of the world, contains numerous lakes. Compared with some information, such as the area, water level, and ice phenology of its lakes, the ice thickness of these lakes remains poorly understood. In this study, we used an unmanned aerial vehicle (UAV) with a 400/900 MHz ice-penetrating radar to detect the ice thickness of Qinghai Lake and Gahai Lake. Two observation fields were established on the western side of Qinghai Lake and Gahai Lake in January 2019 and January 2021, respectively. Based on the in situ ice thickness and the propagation time of the radar, the accuracy of the ice thickness measurements of these two non-freshwater lakes was comprehensively assessed. The results indicate that pre-processed echo images from the UAV-borne ice-penetrating radar identified non-freshwater lake ice, and we were thus able to accurately calculate the propagation time of radar waves through the ice. The average dielectric constants of Qinghai Lake and Gahai Lake were 4.3 and 4.6, respectively. This means that the speed of the radar waves that propagated through the ice of the non-freshwater lake was lower than that of the radio waves that propagated through the freshwater lake. The antenna frequency of the radar also had an impact on the accuracy of ice thickness modeling. The RMSEs were 0.034 m using the 400 MHz radar and 0.010 m using the 900 MHz radar. The radar with a higher antenna frequency was shown to provide greater accuracy in ice thickness monitoring, but the control of the UAV’s altitude and speed should be addressed.
Journal Article
Sediment Ammonia-Oxidizing Microorganisms in Two Plateau Freshwater Lakes at Different Trophic States
Both ammonia-oxidizing archaea (AOA) and bacteria (AOB) can contribute to ammonia biotransformation in freshwater lake ecosystems. However, the factors shaping the distribution of sediment AOA and AOB in plateau freshwater lake remains unclear. The present study investigated sediment AOA and AOB communities in two freshwater lakes (hypertrophic Dianchi Lake and mesotrophic Erhai Lake) on the Yunnan Plateau (China). A remarkable difference in the abundance, diversity, and composition of sediment AOA and AOB communities was observed between Dianchi Lake and Erhai Lake. AOB usually outnumbered AOA in Dianchi Lake, but AOA showed the dominance in Erhai Lake. Organic matter (OM), total nitrogen (TN), and total phosphorus (TP) might be the key determinants of AOB abundance, while AOA abundance was likely influenced by the ration of OM to TN (C/N). AOA or AOB community structure was found to be relatively similar in the same lake. TN and TP might play important roles in shaping sediment AOA and AOB compositions in Dianchi Lake and Erhai Lake. Moreover, Nitrososphaera-like AOA were detected in Dianchi Lake. Nitrosospira- and Nitrosomonas-like AOB were dominant in Dianchi Lake and Erhai Lake, respectively. Sediment AOA and AOB communities in Dianchi Lake and Erhai Lake were generally regulated by trophic state.
Journal Article
The Importance of Allelopathic Picocyanobacterium Synechococcus sp. on the Abundance, Biomass Formation, and Structure of Phytoplankton Assemblages in Three Freshwater Lakes
The contribution of picocyanobacteria to summer phytoplankton blooms, accompanied by an ecological crisis, is a new phenomenon in Europe. This issue requires careful investigation. We studied allelopathic activity of freshwater picocyanobacterium Synechococcus sp. on phytoplankton assemblages from three freshwater lakes. In this study, the allelopathic activity of the Synechococcus sp. on the total abundance, biomass, as well as structure of the phytoplankton assemblages were investigated. Our results indicated that addition of exudates obtained from Synechococcus sp. affected the number of cells and biomass of the phytoplankton communities; the degree of inhibition or stimulation was different for each species, causing a change in the phytoplankton abundance and dominance during the experiment. We observed that some group of organisms (especially cyanobacteria from the genus Aphanothece, Limnothrix, Microcystis, and Synechococcus) showed tolerance for allelopathic compounds produced and released by Synechococcus sp. It is also worth noting that in some samples, Bacillariophyceae (e.g., Amphora pediculus, Navicula pygmaea, and Nitzschia paleacea) were completely eliminated in the experimental treatments, while present in the controls. This work demonstrated that the allelopathic activity exhibited by the Synechococcus sp. is probably one of the major competitive strategies affecting some of the coexisting phytoplankton species in freshwater ecosystems. To our best knowledge this is the first report of the allelopathic activity of Synechococcus sp. in the freshwater reservoirs, and one of the few published works showing allelopathic properties of freshwater picocyanobacteria on coexisting phytoplankton species.
Journal Article
Coordinated Metacommunity Assembly and Spatial Distribution of Multiple Microbial Kingdoms within a Lake
Freshwater planktonic communities comprise a tremendous diversity of microorganisms. This study investigated the distribution patterns of microbial kingdoms (bacteria, fungi, protists, and microbial metazoans) within a lake ecosystem. Water samples were collected from 50 sites along the shoreline in a lake during an early eutrophication period, and MiSeq sequencing was performed with different marker genes. Metacommunity analyses revealed a bimodal occupancy-frequency distribution and a Clementsian gradient persisting throughout all microbial kingdoms, suggesting similar regional processes in all kingdoms. Variation partitioning revealed that environmental characteristics, macrophyte/macroinvertebrate composition, space coordinates, and distance-based Moran’s eigenvector maps (dbMEM) together could explain up to 29% of the community variances in microbial kingdoms. Kingdom synchrony results showed strong couplings between kingdoms (R² ≥ 0.31), except between Fungi and Metazoa (R² = 0.09). Another variation partitioning revealed that microbial kingdoms could well explain their community variances up to 73%. Interestingly, the kingdom Protista was best synchronized with the other kingdoms. A correlation network showed that positive associations between kingdoms outnumbered the negative ones and that the kingdom Protista acted as a hub among kingdoms. Module analysis showed that network modules included multi-kingdom associations that were prevalent. Our findings suggest that protists coordinate community assembly and distribution of other kingdoms, and inter-kingdom interactions are a key determinant in shaping their community structures in a freshwater lake.
Journal Article
Effect of organic matter derived from algae and macrophyte on anaerobic ammonium oxidation coupled to ferric iron reduction in the sediment of a shallow freshwater lake
As a recently discovered process of nitrogen cycling, anaerobic ammonium oxidation coupled to ferric iron reduction (Feammox) has attracted more attentions. This study investigated the spatial variation of Feammox in the sediment of different zones of a shallow freshwater lake and the effect of organic matter derived from algae and macrophyte on Feammox process. The potential Feammox rates showed significant differences among sediments from algae-dominated area (ADA), transitional area in the center of the lake (TDA), and macrophyte-dominated area (MDA), and in a descending order, ADA, MDA, and TDA. The potential Feammox rate ranged from 0.14 to 0.34 mg N kg
−1
day
−1
in the freshwater lake sediment. The potential Feammox rates of the sediment with algae or macrophyte amendment were 12.29% and 15.31% higher than the control test without algae and macrophyte amendment. The addition of algae or macrophyte to the sediment from TDA could improve the amount of HCl-extractable total Fe, Fe(III) reduction rate, and the abundance of FeRB. These results demonstrated that organic matter is one of the key regulators of Feammox process.
Journal Article