High heterogeneity of bacterioplankton community shaped by spatially structured environmental factors in West Lake, a typical urban lake in eastern China

Mechanisms of microbial coexistence in a patchy ecosystem: Differences in ecological niche overlap and species fitness between rhythmic and non-rhythmic species

Resource patchiness caused by external events breaks the continuity and homogeneity of resource distribution in the original ecosystem. For local organisms, this leads to drastic changes in the availability of resources, breaks down the co-existence of species, and reshuffles the local ecosystem. West Lake is a freshwater lake with resource patchiness caused by multiple exogenous disturbances that has strong environmental heterogeneity that prevents clear observation of seasonal changes in the microbial communities. Despite this, the emergence of rhythmic species in response to irregular changes in the environment has been helpful for observing microbial communities dynamics in patchy ecosystems. We investigated the ecological mechanisms of seasonal changes in microbial communities in West Lake by screening rhythmic species based on the ecological niche and modern coexistence theories. The results showed that rhythmic species were the dominant factors in microbial community changes and the effects of most environmental factors on the microbial community were indirectly realised through the rhythmic species. Random forest analyses showed that seasonal changes in the microbial community were similarly predicted by the rhythmic species. In addition, we incorporated species interactions and community phylogenetic patterns into stepwise multiple regression analyses, the results of which indicate that ecological niches and species fitness may drive the coexistence of these subcommunities. Thus, this study extends our understanding of seasonal changes in microbial communities and provides new ways for observing seasonal changes in microbial communities, especially in ecosystems with resource patches. Our study also show that combining community phylogenies with co-occurrence networks based on ecological niches and modern coexistence theory can further help us understand the ecological mechanisms of interspecies coexistence.

Environmental heterogeneity associated with boat activity shapes bacteria and microeukaryotic communities with discrepant response patterns

With the development of global tourism, tourist boats, a significant form of anthropogenic disturbance, are having an increasingly serious impact on the structure and function of aquatic ecosystems. In this study, the effects of different intensities of tourist boat activities on the microbial communities of West lake, were investigated by high-throughput sequencing. The results showed significant differences in the composition of bacterioplankton and microeukaryotic communities between the high-intensity boat activity (HIBA) area and low-intensity boat activity (LIBA) area. Variation partitioning analysis showed that environmental factors contributed the most to microbial community variation, and the effect of boat activities on microbial communities mainly occurred through coupling with environmental factors. The contribution of boat activity to microbial community changes occupies the second place, the first being environmental factors. Co-occurrence network analyses showed that microbial communities in the HIBA area had more nodes and edges, higher connectivity and lower modularity than in the LIBA area, suggesting a more complex and stable network. Networks of associations between potential keystone taxa and environmental factors reveal the way in which boat activity affects microbial communities. The bacterial community responded strongly to environmental factors associated with boat activities, whereas the microeukaryotic community was more likely to be regulated by interspecific interactions. This also suggests that when faced with disturbances from the boat activity, microeukaryotes might exert a stronger direct resistance effect compared to bacterioplankton. These findings imply that bacterioplankton and microeukaryotes demonstrate distinct response patterns in the presence of disturbance caused by boat activity. Our research expand our understanding of the effects of boat activities on aquatic ecosystems and provide further insights into the assessment of anthropogenic disturbances in aquatic ecosystems.

Spatio-Temporal Dynamics in Physico-Chemical Properties, Phytoplankton and Bacterial Diversity as an Indication of the Bovan Reservoir Water Quality

The study aimed to investigate the physico-chemical properties as well as phytoplankton and bacterial community diversity of Bovan Lake reservoir in Serbia to gain insight into the seasonal dynamic of water quality. All analyses were performed at three localities and water depths in spring, summer, autumn, and winter 2019. Seven phytoplankton phyla comprising 139 taxa were detected at all three localities (Chlorophyta 58%, Bacillariophyta 14%, Cyanobacteria 9%, Chrysophyta 5%, Dinophyta 5%, Euglenophyta 5%, and Cryptophyta 4%). Winter 2019 was characterized by the presence of 36 unique species in all phyla except Euglenophyta. Bacterial diversity analyses showed that Proteobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria, and Verrucomicrobia dominated the water intake locality at all three water depths (0.5, 10, and 20 m below the surface). In general, the physico-chemical parameters, phytoplankton, and bacterial community composition depended on the season and the water depth and showed that Bovan Lake was of satisfactory ecological status and water quality at all localities, and meets the needs for all intended purposes.

Assessment of rural ecological environment development in China's moderately developed areas: a case study of Xinxiang, Henan province

The reforming and opening-up has brought about the rapid development of China's economy, greatly improved the living standards of rural residents, and also caused the destruction of the rural ecological environment. Due to the backward production technology and pollution control technology, many township enterprises discharge excessive pollutants, and excessive application of chemical fertilizers and pesticides in agricultural production causes serious agricultural non-point source pollution. These pollution sources that cannot be effectively controlled cause a large number of water and land resource function decline. Not only the loss of agricultural production, but they also bring hidden danger to the survival of many rural residents. Taking Xinxiang city of Hunan province as an example, this paper selects 28 indicators and mainly uses AHP, entropy weight method, and fuzzy comprehensive evaluation method to evaluate and analyze the development level of rural ecological environment. This study can provide a reference for the Chinese government to formulate rural development planning and can also be used as a reference for the evaluation of rural ecological environment in developed and underdeveloped areas.

Co-occurrence of planktonic bacteria and archaea affects their biogeographic patterns in China's coastal wetlands

Planktonic bacteria and archaea play a key role in maintaining ecological functions in aquatic ecosystems; however, their biogeographic patterns and underlying mechanisms have not been well known in coastal wetlands including multiple types and at a large space scale. Therefore, planktonic bacteria and archaea and related environmental factors were investigated in twenty-one wetlands along China's coast to understand the above concerns. The results indicated that planktonic bacteria had different biogeographic pattern from planktonic archaea, and both patterns were not dependent on the wetland's types. Deterministic selection shapes the former's community structure, whereas stochastic processes regulate the latter's, being consistent with the fact that planktonic archaea have a larger niche breadth than planktonic bacteria. Planktonic bacteria and archaea co-occur, and their co-occurrence rather than salinity is more important in shaping their community structure although salinity is found to be a main environmental deterministic factor in the coastal wetland waters. This study highlights the role of planktonic bacteria-archaea co-occurrence on their biogeographic patterns, and thus provides a new insight into studying underlying mechanisms of microbial biogeography in coastal wetlands.

Patterns of Structural and Functional Bacterioplankton Metacommunity along a River under Anthropogenic Pressure

Bacteria, an integral part of aquatic ecosystems, are responsible for the circulation of matter and flow of energy. Since bacterioplankton rapidly responds to any natural and human-induced disturbances in the environment, it can serve as a bioindicator of these changes. Knowing factors that shape the microbial community structure may help the sustainable management of the water environment. However, the identification of environmental signals affecting the structure and function of bacterioplankton is still a challenge. The study analyses the impact of environmental variables on basic microbial parameters, which determines the effectiveness of ecological processes in rivers. Measurements of bacterioplankton abundance (BA) and extracellular enzyme activity (EEA) were based on fluorescent markers. The bacterial community structure was determined by 16S rRNA gene amplicon sequencing (Illumina). The results indicate spatial variation in bacterioplankton abundance. Temporal variation was not significant. Lipase and aminopeptidase had the highest level of activity. EEA was not correlated with bacterial abundance but was significantly correlated with temperature. Moreover, differences in lipase, α-glucosidase and β-glucosidase activity levels between spring and summer were noted. At the same time, the location of sampling site had a significant influence on aminopeptidase activity. The taxonomic analysis of bacterioplankton communities in the Brda River indicated that, although different numbers of OTUs were recorded in the studied river sections, bacterioplankton biodiversity did not change significantly along the river with distance downstream. Anthropogenically modified river sections were characterized by the dominance of Flavobacterium (Bacterioidetes) and hgcl clade (Actinobacteria) taxa, known for their ability to produce extracellular enzymes. PCoA analysis revealed that the sites located in the lower river course (urban area) had the most similar bacterial community structure (β-diversity). The study provides new insight into the changes in microbial communities along the river and emphasizes the potential impact of anthropogenization on these processes.

Evaluation of microbial diversity of three recreational water bodies using 16S rRNA metagenomic approach

Surface water plays a significant role in world development by promoting economic growth and health benefits to humans and animals whose lives depend on good water quality in the ecosystem. Thus, this study investigated the differences in physical and chemical properties of surface water from two lakes (Lakes Jackson and Talquin) and a pond (Pedrick Pond). Also, the influence of environmental factors on the microbial communities that live within the water environment was examined. Genomic DNA was extracted from the water samples collected and 16S rRNA sequencing method was employed to characterize the microbial community compositions across the three locations. The results obtained suggest that the water sources met the recommended recreational water quality criteria standard for clean water. Overall, Proteobacteria, Actinobacteria, Cyanobacteria, Bacteroidetes were the main bacterial phyla present in the communities, while Archaea was mainly dominated by Euryachaeota. Pressure, conductivity, temperature, dissolved oxygen (DO), and pH accounted for 74.2% of the variation in the distribution of the microbial community in the three locations (P < 0.05), while 58.2% of the variation in the microbial community distribution was accounted for by pressure and conductivity. The high temperature observed in the Pedrick Pond correlated with the distribution of genera hgcl_clades and Legionella. While in Lake Talquin, water conductivity was significantly associated with the abundance of Cyanobium_PCC_6307, Sediminibacterium, and Conexibacter. The results from this study indicate that the microbial communities in the two lakes are different from the pond and all the environmental variables accounted for a significant portion of the total variation, but pressure, conductivity, and temperature are more important factors due to significant correlation with the distribution of the microbial communities.