Stability Of Lake Ecosystem Research Articles

Microbial eukaryote community succession over hundreds of years in Chinese lakes

Microbial eukaryotes play critical roles in maintaining the health and stability of lake ecosystems. Consequently, investigating the spatial and temporal evolution of microbial eukaryotic community structures and associated environmental drivers can inform water ecology studies and water environmental protection efforts. In this study, sediment core samples were collected from Lakes Chaohu, Erhai, Lugu and Fuxian in China to reconstruct lake microbial eukaryotic community succession using sediment DNA profiling methods. Mantel tests were used to identify the key factors influencing community succession and explore the mechanisms underlying ecological network changes. Statistical analyses revealed that community structures and diversity in Lakes Chaohu and Erhai shifted in the 2000s and 1980s, respectively, while the communities of Lakes Fuxian and Lugu did not exhibit significant changes during the study period, which may be due to the oligotrophic state of these two lakes. Ciliophora and Chlorophyta were the primary eukaryotic microbial taxa in the four lakes during the study period, with overall relative abundances of 27.2 % and 22.3 %, respectively. The diversities of microbial eukaryotic communities in the lakes were significantly correlated with nutrient enrichment and meteorological factors. Lastly, the ecological niche gap of microbial eukaryotes gradually overlapped after community shifts in Lake Chaohu, while biased interactions strengthened. Overall, this study reveals the impacts of long-term human activities and climate change on lake ecosystems from multiple perspectives of microbial eukaryotic community structure, diversity and ecological network, these findings will contribute to integrate microbial indicators in freshwater environmental monitoring in the future.

Microbiological features of the salt lakes of the Kulunda lake system

The object of the study was the water and bottom sediments of the Bolshoye Yarovoye and Burlinskoye salt lakes located in the Kulunda steppe lowland and having recreational value. The aim of this work is to study the antibacterial and anti-candidiasis properties of water and bottom sediments of lakes in the Kulunda lake region in the context of their ecological state. The main factors affecting the basins of lakes B. Yarovoe and Burlinskoe are the intensification of the recreational load due to the development of domestic tourism, the activities of industrial enterprises, and, as a consequence, the washout of pollutants, the extraction and transportation of salt (in Lake Burlinskoe) and the almost complete extraction of silt mud. (in Lake B. Yarovoe), plowing of adjacent territories. No causative agents of infectious diseases were found in the water and bottom sediments, and the total microbial count is about 102 CFU / ml. The predominant group of microorganisms found on agar culture media are non-spore-bearing bacteria. The water of the salty lake B. Yarovoe, filtered from microorganisms, possesses inhibitory properties in relation to all studied 14 gram-positive and gram-negative test strains of microorganisms, and the water of Lake Burlinskoye in relation to nine strains: gram-negative bacteria Salmonella sonnei 32, Klebsiella pneumonia В-4894, Рseudomonas mirabilis 160205, Serratia marcescens d, Pseudomonas aeruginosa ATCC 9027, Escherichia coli 6645 ATCC 25922, gram-positive bacteria Staphylococcus aureus ATCC 6538, Mycobacterium smegmatis GK and regarding the causative agent of candidiasis Candida albicans 620. It was also shown that pure cultures of spore-forming bacteria isolated from the water and bottom sediments of the studied lakes also have antagonistic activity. The ecological stability of lake ecosystems, in spite of anthropogenic transformation and climatic changes affecting the water and salt regime, is based on biogenic processes that provide resistance to microorganisms introduced from outside, including pathogenic ones, and their elimination.

Quantification of the covariation of lake microbiomes and environmental variables using a machine learning-based framework.

It is known that microorganisms are essential for the functioning of ecosystems, but the extent to which microorganisms respond to different environmental variables in their natural habitats is not clear. In the current study, we present a methodological framework to quantify the covariation of the microbial community of a habitat and environmental variables of this habitat. It is built on theoretical considerations of systems ecology, makes use of state-of-the-art machine learning techniques and can be used to identify bioindicators. We apply the framework to a data set containing operational taxonomic units (OTUs) as well as more than twenty physicochemical and geographic variables measured in a large-scale survey of European lakes. While a large part of variation (up to 61%) in many environmental variables can be explained by microbial community composition, some variables do not show significant covariation with the microbial lake community. Moreover, we have identified OTUs that act as "multitask" bioindicators, i.e., that are indicative for multiple environmental variables, and thus could be candidates for lake water monitoring schemes. Our results represent, for the first time, a quantification of the covariation of the lake microbiome and a wide array of environmental variables for lake ecosystems. Building on the results and methodology presented here, it will be possible to identify microbial taxa and processes that are essential for functioning and stability of lake ecosystems.

Hydrological Variability of Water Level of Dianchi Lake and Its Application

The water level is an important indicator for lake operation management, and the variability of lake water level will have an important impact on the ecological suitability of aquatic vegetation. The ecological water level of lakes is the minimum water level for maintaining the structural and functional integrity and biodiversity of lake ecosystems. Therefore, it is very important to determine the ecological water level of lakes is for maintaining the harmony and stability of lake ecosystems. This paper analyzed the characteristics of water level, the lowest and suitable ecological water levels and the guarantee degree, by using the monthly water level data of Dianchi Lake from 1961 to 2016. The main conclusions are as follows: (1) The water level of Dianchi Lake mainly had a change period of about 15 years; (2) The abrupt change point of water level of Dianchi Lake occurred in 1994; (3) The lowest and suitable ecological water levels of Dianchi Lake and its actual water level had a typical unimodal distribution. The ecological water level in spring and winter was high, while that in summer and autumn was low. Thereinto, the lowest and suitable ecological water levels in May were lowest, 1885.86m and 1886.04m respectively, while those in November were highest, 1886.60m and 1886.78m respectively. (4) The guarantee degree of the lowest ecological water level of Dianchi Lake was as high as 93%∼95% within the year, while the guarantee degree of the suitable ecological water level could only reach 46%∼50%. The guarantee rate of the ecological water level during the low water level period was higher than that during the high water level period, and the guarantee degree of the interannual ecological water level varied greatly over the years. The lowest guarantee degree occurred in 1988 and 1989 with 0%, followed by the guarantee degrees of 50% and 8% in 1993, and they had reached 100% since 1994.

Quantifying change in pelagic plankton network stability and topology based on empirical long-term data

Over the last 34 years, Lake Müggelsee has experienced concurrent warming and nutrient reduction. While the effects of environmental change on single taxonomic or physical–chemical variables have been relatively well researched in isolation, understanding how environmental change propagates through the ecological network remains a major challenge. Capitalizing on the long-term monitoring program of the German Long-Term Ecosystem Research Network site Lake Müggelsee (1979-ongoing), we identified three time periods (1979–1995; 1996–2005; 2006–2013) which differed significantly in phytoplankton biomass and relative plankton community composition. Using multivariate first order autoregressive (MAR1) modeling on 13 pelagic plankton groups and four abiotic variables, we quantified interaction networks and indicators of stability and centrality for each period. Our results suggested that the Müggelsee network was bottom-up regulated in all periods and that stability increased over time. Moreover, in all three networks, non-trophic and indirect interactions appeared to be as commonly present as trophic and direct interactions. Using network centrality measures of betweenness and closeness, we identified keystone plankton groups and groups particularly responsive to environmental change based on variation in centrality ranks over time. Given a more comprehensive understanding of the interaction network at hand, MAR1 model-derived stability and centrality measures may potentially be used as integrated ecological indicators to monitor changes in stability of lake ecosystems and to identify particularly vulnerable components of the network.

X-ray microanalysis and microbial colonization of leaves in Lake Wallenpaupack in eastern Pennsylvania

The microbial decomposition of leaf litter provides a major source of organic carbon and other nutrients and is important in ensuring the stability of lake ecosystems. Lake leaf litter can also act as a sink for immobilization of nutrients and elements. This investigation utilizes the scanning electron microscope and the energy-dispersive x-ray microanalysis technique to study the effects of agricultural or septic tank leakage pollutants on microbial colonization and elemental accumulation in leaves submerged in a lake in eastern Pennsylvania.White oak and red maple leaves were placed in mesh bags in the littoral zone of three cove sites at lake Wallenpaupack, a 13 mile-long, 5,700 acre lake located in the Pocono Mountains in eastern Pennsylvania. Cove 1 was surrounded by a wooded area and received water input from a wetland preserve. Cove 2 was suspected of contamination by septic tank leakage. Cove 3 received water input from a tributary passing through a heavily farmed drainage basin.