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Particle-attached (PA) and free-living (FL) bacterial communities play essential roles in the biogeochemical cycling of essential nutrients in aquatic environments. However, little is known about the factors that drive the differentiation of bacterial lifestyles, especially in flooding lake systems. Here we assessed the compositional and functional similarities between the FL and PA bacterial fractions in a typical flooding lake—the Poyang Lake (PYL) of China. The results revealed that PA communities had significantly different compositions and functions from FL communities in every hydrological period, and the diversity of both PA and FL communities was affected mainly by the water regime rather than bacterial lifestyles. PA communities were more diverse and enriched with Proteobacteria and Bacteroidetes, while FL communities had more Actinobacteria. There was a higher abundance of photosynthetic and nitrogen-cycling bacterial groups in PA communities, but a higher abundance of members involved in hydrocarbon degradation, aromatic hydrocarbon degradation, and methylotrophy in FL communities. Water properties (e.g., temperature, pH, total phosphorus) significantly regulated the lifestyle variations of PA and FL bacteria in PYL. Collectively, our results have demonstrated a clear ecological differentiation of PA and FL bacterial communities in flooding lakes, suggesting that the connectivity between FL and PA bacterial fractions is water property-related rather than water regime-related. [ABSTRACT FROM AUTHOR]

Purpose: The home-field advantage (HFA) of litter decomposition is widespread in various terrestrial ecosystems, but whether it is present in wetland ecosystems and what the influencing factors are is less well-known. Here we conducted a 165-day transplanted litter decomposition experiment in a wetland ecosystem to explore the HFA effect and its relationships to litter quality and decomposer community structure. Methods: Three types of litter (sedge, silvergrass, and reed leaves) were transplanted in the Poyang Lake Wetlands of China, and the decomposition rate was accessed by periodic recovery of the remained litter samples. The bacterial and eukaryotic decomposer communities were determined by the rRNA gene sequencing method. Extracellular enzyme activities from litters were continuously monitored during decomposition. Co-occurrence networks were constructed to identify the keystone taxa. Results: We found that the HFA of litter decomposition was prevalent in wetlands, with home-field advantage for sedge and silvergrass litters, while home-field disadvantage for reed litter. The primary litter quality (especially TN and cellulose), enzymatic activity, and nutrient release pattern all affected the HFA effect. The most significant variation of decomposer community occurred among decay times, followed by litter types and decay sites. The difference in decomposer community composition among litters decreased with the decomposition time. The bacterial communities were significantly different among decay sites for all litters, while the eukaryotic communities were similar among decay sites until 165 days. The bacterial community was more sensitive to the HFA, while the eukaryotic community mainly contributed to the decomposition rate. Some habitat-specific decomposers contributed to the HFA, including Gammaproteobacteria, Alphaproteobacteria, Firmicutes, Ascomycota, Nematoda, and Ciliophora. The networks for litters with HFA had more nodes, more positive edges and keystone species than the litters without HFA. Conclusion: The initial litter quality and decomposer community (mainly bacteria) collectively drive the HFA of litter decomposition in wetlands, and the network analysis may be used to predict the HFA during litter decomposition. [ABSTRACT FROM AUTHOR]

Purpose: Wetland soils may face more severe water stress under future climate change. Our aim was to assess the change characteristics of wetland soil bacterial community and metabolic potentials under drought and flood conditions. Methods: Wetland soil was incubated under five different water environments (including constant moisture at 30%, natural air-dried, and 3 types of flooding depths) by conducting experimental microcosms. After 1, 21, and 132 days of incubation, the soil bacterial community structure and metabolic potential were examined by the 16S rRNA gene sequencing and Biolog-Ecoplates method, respectively. Results: The results showed that Actinobacteria and Firmicutes were significantly enriched under drought and flooding treatments, respectively. Compared to flooding, drought decreased soil microbial biomass and carbon metabolism more severely. However, the depth of flooding did not significantly change bacterial community composition and carbon metabolism. In addition, the responses of soil metabolic functions to drought were more sensitive than the change of bacterial community composition. When the wetland soil faced water stress (drought and flooding), its metabolic functions showed close correlations with bacterial community composition and were negatively affected by most of environmental factors (such as pH, NO3-N, and NH4-N). Conclusions: The results indicate that the drying condition is more severe and rapid than flooding in threatening soil microbial metabolic activity. In addition, the depth of flooding does not significantly change bacterial community composition and carbon metabolism. [ABSTRACT FROM AUTHOR]