Impact of extreme rainfall and flood events on harmful cyanobacterial communities and ecological safety in the Baiyangdian Lake Basin, China.

Globally, climate change has intensified extreme rainfall events, leading to substantial hydrological changes in aquatic ecosystems. These changes, in turn, have increased the frequency of harmful algal blooms, particularly those of cyanobacteria. This study examines cyanobacterial community dynamics in the Baiyangdian Lake Basin, China, after heavy rainfall and flooding events. The aim was to clarify how such extreme hydrological events affect cyanobacterial populations in floodplain ecosystems and assess related ecological risks. The results demonstrated a significant increase in cyanobacterial diversity, exemplified by an increase of the Shannon diversity index from an average of 1.7 to 2.1 (p < 0.05). Following heavy rainfall and subsequent flooding, the average relative abundance of cyanobacteria in the microbial community increased from 7.59 % to 9.62 %, along a notable rise in the abundance of harmful cyanobacteria. The community structure exhibited notable differences after flooding, showing an increase in species richness, but a decrease in community tightness and clustering, as well as a reduction in niche overlap among harmful cyanobacteria. Environmental factors such as dissolved oxygen, water temperature, and pH were identified as crucial predictors of harmful cyanobacterial community differences and abundance variations resulting from flooding. These findings provide a critical framework for predicting ecological risks associated with the expansion of bloom-forming cyanobacteria in large shallow lake basins, particularly under intensified rainfall and flooding events. This insight is essential to anticipate potential ecological disruptions in sensitive aquatic ecosystems.

Dual optimization in anaerobic digestion of rice straw: Effects HRT and OLR coupling on methane production in one-stage and two-stage systems.

This experiment reports an energy-saving, cost-effective and environmental-friendly method to recover energy from high-cellulose waste: anaerobic digestion (AD) by extending hydraulic residence time (HRT) from 50d to 70d with ultra-high organic loading rate (OLR) of 2.28-2.80 g TS·L-1 d-1. The results indicate that biogas yield per VS and methane yield per VS increase with the extended HRT, with a maximum increase of up to 67.9%, while both yields decrease as OLR increases. The volumetric gas production (VGP) and volumetric methane production (VMP) improve by 20.2-37.3% when HRT is extended to 57 days and OLR is 2.80 g TS·L-1 d-1, reaching a peak at this point. As the biogas production capacity of the two-stage anaerobic digestion reaches its peak, the gap between the one-stage system and the two-stage system decreases from 23% to 7% under the same conditions. This demonstrates that optimizing HRT and OLR not only enhance the gas production efficiency of the AD system but also reduce the gas production disparity between single-stage and two-stage systems, thus serving as a cost-effective method for engineering operations. Microbial community analysis of each system reveals that extending HRT increases the abundance and diversity of microbial communities, while changes in HRT and OLR result in significant shifts in the distribution of methanogens. Through reasonable regulation of HRT and OLR, a balance can be found between the full degradation of organic matter and the system load, so as to maximize biogas production and efficiency.

Reduced primary productivity and notable resilience of phytoplankton community in the coastal water of southern China under a marine heatwave.

Increasing frequency, intensity and duration of marine heatwaves (MHWs) are supposed to affect coastal biological production in different regions to different extents. To understand how MHWs impact coastal primary productivity and community succession of phytoplankton and assess the changes in resilience of phytoplankton communities, we conducted a mesoscale enclosure experiment simulating a marine MHW in the coastal water of southern China. After 8 days of the MHW (+3 oC) treatment, community biomass was significantly lower than the control's, and primary productivity per volume of water was reduced by about 56%. Nevertheless, the phytoplankton community retrieved its biomass and primary productivity after the temperature was subsequently reset to that of the control. Although the MHW treatment decreased the abundance of diatom and increased the percentages of Synechococcus and Prasinophytes, the main phytoplankton functional types showed positive resilience that allowed the recovery of the phytoplankton community after the MHW. Our results indicate that key phytoplankton functional types in the southern coastal waters of China exhibited significant resilience, recovery, and temporal stability under the influence of the marine MHW by 3 oC rise. However, reduced primary productivity during the MHW period, along with decreased biomass density, might significantly influence secondary producers. In addition, the altered phytoplankton community structure may affect coastal food web processes at least during the MHW period.

The addition of humic acid into soil contaminated with microplastics enhanced the growth of black gram (Vigna mungo L. Hepper) and modified the rhizosphere microbial community.

Microplastics have polluted agricultural soils, posing a substantial risk to crop productivity. Moreover, the presence of microplastic pollution has caused a disturbance in the composition of the microbial community in the soil surrounding plant roots, therefore impacting the growth of beneficial bacteria. A study was conducted to examine if humic acid (HA) can counteract the harmful effects of microplastics (MPs) on the growth of black gram crops and the composition of the rhizosphere soil microbial community, to reduce the negative impacts of microplastics on these microorganisms and crops. The research was carried out using mud pots and the plastic utilized for the experiment consisted of 60% high-density polyethylene (HDPE) and 40% polypropylene (PP). The soil was enriched with lignite-based potassium humate, which had a pH range of 8.0-9.5 and with 65% humic acid. The experiment consisted of six treatments: T1, which served as the control without HA and MP; T2, which involved the use of HA at a concentration of 0.15% w/w; T3, which involved the use of MP at a concentration of 0.2% w/w; T4, which involved the use of MP at a concentration of 0.4% w/w; T5, which involved the combination of HA at a concentration of 0.15% w/w and MP at a concentration of 0.2% w/w; and T6, which involved the combination of HA at a concentration of 0.15% w/w and MP at a concentration of 0.4% w/w. The plant growth characteristics, including germination percentage, nodule number, and chlorophyll content, were measured. In addition, the DNA obtained from the rhizosphere soil was analyzed using metagenomics techniques to investigate the organization of the microbial population. Seedlings in soil polluted with MP exhibited delayed germination compared to seedlings in uncontaminated soil. Following 60 days of growth, the soil samples treated with T5 (0.2% MP and 0.15% HA w/w) had the highest population of bacteria and rhizobium, with counts 5.58 ± 0.02 and 4.90 ± 0.02 CFU g-1 soil. The plants cultivated in T5 had the most elevated chlorophyll-a concentration (1.340 ± 0.06 mg g-1), and chlorophyll-b concentration (0.62 ± 0.02 mg g-1) while those cultivated in T3 displayed the lowest concentration of chlorophyll-a (0.59 ± 0.02 mg g-1) and chlorophyll-b (0.21 ± 0.04 mg g-1). Within the phylum, Proteobacteria had the highest prevalence in all treatments. However, when the soil was polluted with MPs, its relative abundance was reduced by 8.4% compared to the control treatment (T1). Conversely, treatment T5 had a 3.76% rise in relative abundance when compared to treatment T3. The predominant taxa found in soil polluted with MP were Sphingomonas and Bacillus, accounting for 19.3% of the total. Sphingomonas was the predominant genus (21.2%) in soil polluted with MP and supplemented with humic acid. Humic acid can be used as a soil amendment to mitigate the negative effects of MPs and enhance their positive advantages. Research has demonstrated that incorporating humic acid into soil is a viable method for maintaining the long-term integrity of soil's physical, chemical, and biological characteristics.

Tree species selection for optimizing soil carbon storage: Insights from litter decomposition and bacterial community analysis in coastal ecosystems.

Coastal wetland ecosystems are critical sinks for atmospheric carbon dioxide, playing a vital role in global carbon cycling and climate regulation. The decomposition of leaf litter plays a crucial role in the formation and stability of soil organic carbon (SOC) in these environments. This study investigated the impact of leaf litter decomposition from five tree species (Populus deltoids, Ligustrum lucidum, Taxodium 'Zhongshanshan', Hibiscus hamabo, and Nerium oleander) on SOC dynamics, humus composition, and soil bacterial community structure in a tidal flat. Litterbags were used to monitor the mass loss and changes in litter chemical composition over 270 days. The results revealed significant differences in decomposition rates among the tree species, with Nerium oleander exhibiting the fastest decomposition and Populus deltoids the slowest. Surprisingly, initial litter chemistry did not correlate with decomposition rates; however, changes in lignin and hemicellulose content during decomposition were significantly related to mass loss. Despite its rapid decomposition, Nerium oleander litter resulted in the highest accumulation of SOC, total humus, and humin compared to the other species, challenging the conventional view that slower decomposition leads to greater SOC storage. The soil microbial community structure was significantly influenced by SOC, humus, and litter components, with distinct microbial assemblages associated with each tree species. A random forest model identified key bacterial taxa, predominantly Proteobacteria, as important predictors of SOC content, highlighting the role of bacterial diversity in regulating SOC dynamics. These findings underscore the importance of considering litter quality, decomposition dynamics, and bacterial community composition in strategies aimed at enhancing soil carbon sequestration. This study suggests that selecting tree species with rapidly decomposing litter, such as Nerium oleander, in coastal plantations can be an effective management tool for optimizing soil carbon storage, offering valuable insights for mitigating climate change impacts.

Investigating the inhibitory mechanism of methanogenesis during composting under the combined influence of amoxicillin and copper pollution.

This study investigated the effects of different levels of combined amoxicillin and copper (Cu) pollution on the methanogenesis of microbial communities during aerobic composting of dairy manure. Three groups were established: the control group (CK), a low-level combined pollution group (L), and a high-level combined pollution group (H). As the level of pollution increased, carbohydrate metabolism decreased during the thermophilic phase of composting, while signal translation increased. Compared with the initial phase, functional genes related to the acetoclastic pathway decreased significantly in abundance during the thermophilic phase, and cdh had the lowest relative abundance among acetoclastic pathway with a decrease of 81.52%, 81.88%, and 84.73% in groups CK, L, and H, respectively. The cumulative methane emissions in group H decreased by 31.56% and 9.23%, respectively, compared with those from groups CK and L. These results contribute to understanding the effects of combined amoxicillin and Cu pollution on methane emissions during composting.

Effects of carbon and nitrogen availability on soil microbial respiration and its metabolic response in subtropical plantations.

We examined the metabolic response of microbial respiration to glucose addition with the topsoil (0-10 cm) from five plantation types, including Quercus glauca, Castanopsis kawakamii, Pinus massoniana, Phoebe bournei, and Cinnamomum camphora plantations, in the Sanming Forest Ecosystem National Field Observation and Research Station in Fujian Province. The results showed that glucose addition significantly increased microbial respiration by 82.4%-349.5%, with significant difference among tree species. In the control, microbial respiration significantly correlated with microbial biomass carbon, soil organic carbon, and the fungi/bacteria ratio, indicating that microbial metabolism was regulated by soil organic carbon content and was associated with microbial biomass and community structure in the absence of labile carbon supply. In the glucose addition treatment, microbial respiration positively correlated with soil total nitrogen, dissolved organic nitrogen, and mineral nitrogen, indicating that microbial metabolism was mainly constrained by soil nitrogen content and its availability in the presence of adequate labile carbon supply. The metabolic response of microbial respiration, as indicated by the ratio of microbial respiration in the glucose addition treatment to that in the control, was primarily affected by soil carbon/nitrogen ratio, with a decrease in the ratio leading to an increase in the microbial metabolic response. Additionally, soil pH played an important role in mediating microbial metabolic response. The effect of the content and availability of soil carbon and nitrogen on microbial respiration depended on whether microbes were carbon-limited. Soil carbon content media-ted microbial respiration when microbes were carbon-limited, whereas soil nitrogen content and availability mediated microbial respiration after the alleviation of microbial carbon limitation.

Unique ecology of biofilms and flocs: Bacterial composition, assembly, interaction, and nitrogen metabolism within deteriorated bioreactor inoculated with mature partial nitrification-anammox sludge.

This work unraveled discrepant ecological patterns between biofilms and flocs in a deteriorated bioreactor inoculated with mature partial nitrification-anammox (PN/A) sludge. Based on 16S rRNA analysis, a comprehensive evaluation of neutral and null models, along with niche width, delineated that the bacterial community assembly in biofilms and flocs was dominantly driven by the stochastic process, and dispersal limitation critically shaped the community assembly. Co-occurrence network analysis revealed that environmental stress caused decentralized and fragmented bacterial colonies, and anammox bacteria were mainly peripheral in biofilms network and less involved in interspecific interactions. Simultaneous PN/A and partial denitrification-anammox (PD/A) processes were identified, whereas PN and PD process primarily occurred in the biofilms and flocs, respectively, as evidenced by metagenomics. Collectively, these outcomes are expected to deepen the basic understanding of complex microbial community and nitrogen metabolism under environmental disturbance, thereby better characterizing and serving the artificial ecosystems.

The composition of the arbuscular mycorrhizal fungal bacteriome is species dependent.

BACKGROUND: In addition to their role as endosymbionts for plant roots, arbuscular mycorrhizal fungi (AMF) engage in complex interactions with various soil microorganisms, the rhizosphere, and the root endosphere of host plants. They also host diverse prokaryotic groups within their mycelia, contributing to what is termed multipartite symbiosis. In this study, we examined the impact of three AMF species-Rhizophagus irregularis, R. clarus, and R. cerebriforme-combined with microbial bioaugmentation on the diversity and composition of bacterial communities in the mycelia and hyphosphere. Using a microcosm design to separate the influence of host plant roots from AMF mycelia and Illumina MiSeq amplicon sequencing to analyze the bacterial communities. RESULTS: Our results revealed that, while AMF identity and microbial bioaugmentation did not affect the structure of bacterial communities in the hyphosphere soil, they significantly altered the communities associated with their mycelia. Although all three AMF species belong to the same genus, with R. irregularis and R. clarus being closely related compared to R. cerebriforme, we observed variations in the bacterial communities associated with their mycelia. Interestingly, the mycelial bacterial community of R. cerebriforme contained 60 bacteriome core taxa exclusive to it, while R. clarus and R. irregularis had 25 and 9 exclusive taxa, respectively. CONCLUSION: This study suggests that organismal phylogeny influences the bacterial communities associated with AMF mycelia. These findings provide new insights into AMF and bacterial interactions, which are crucial for the successful deployment of AMF inoculants. The taxonomic diversity of AMF inoculants is important for engineering the plant microbiome and enhancing ecosystem services.

Soil microbial community composition and diversity in the rhizosphere of Alsophila spinulosa growing in different habitats within the Chishui Alsophila National Nature Reserve in Guizhou Province, China.

The rhizosphere is considered a highly complex and dynamic ecosystem. Rhizosphere soil microorganisms influence the growth and development of plants by mediating the transformation and absorption of nutrients. In order to explore the microbial community composition and diversity of Alsophila spinulosa growing in different habitats. Rhizosphere samples were collected from four different habitats within the Chishui Alsophila National Nature Reserve in Guizhou Province, China. According to the high-throughput sequencing results of 16 s rDNA and ITS, Proteobacteria and Ascomycota were the most abundant bacterial and fungal phyla in the rhizosphere soil of all four habitats. The alpha diversity analysis indicated that two particular habitats, Buddha Rock and Botanical Garden, harbored the highest microbial richness and diversity. LEfSe analysis revealed that Buddha Rock contained the highest relative abundance of Bacteroidetes compared to the other three study areas. Meanwhile, Tiantang Gou contained the highest relative abundance of Basidiomycota. Bacterial community composition and diversity were greatly influenced by soil pH, while fungal community composition and diversity were greatly influenced by available phosphorus, organic carbon, sucrase, and urease. The results of this study provide a scientific basis for the habitat restoration of A. spinulosa, and the improvement of the structure of the A. spinulosa rhizosphere soil microbial community. Laying a theoretical foundation for the next screening of inter-root functional flora.

Fertilization shapes microbial life strategies, carbon and nitrogen metabolic functions in Camellia oleifera soil.

Mineral and organic fertilizers as well as microbial inoculations are crucial to maintain and to improve soil health and quality, ecosystem functions, and fruit yield in Camellia oleifera plantations. However, how these fertilizers shape the life strategies and functions of microbial communities in soil is unclear. Here, we conducted a one-year field experiment with three types of fertilizers: mineral (NPK), manure (Man), and microbial (MicrF), and analyzed soil properties, bacterial and fungal communities to assess microbial life strategies, functional traits and their determinants. The application of MicrF strongly increased the diversity of both soil bacterial (by 6.4%) and fungal communities (by 23%). Organic matter inputs from Man and MicrF had greater effects on the life strategies of bacteria than fungi: the dominant r-strategy bacteria (Proteobacteria, Bacteroidetes, and Actinobacteria) increased with Man and MicrF, but K-strategists (Acidobacteria) decreased. Conversely, the abundance of r-strategy fungi (Ascomycota) decreased, but that of K-fungi (Basidiomycota) increased. Predictions of the functions indicated that microbial fertilization accelerated the bacterial carbohydrates, carbon and nitrogen metabolism, while also increasing the prevalence of wood saprotrophic fungi. The changes in the taxonomic and functional characteristics of the microbial communities induced priming effects by co-metabolism, which were mainly regulated by contents of soil organic carbon, available phosphorus, and ammonium nitrogen, as well as carbon to nitrogen ratio. The application of MicrF is an effective approach to increase the diversity and multifunctionality of soil microbial communities in Camellia oleifera plantations, including organic matter decomposition, carbon and nitrogen metabolism. These findings provide valuable insights into the fertilizer regimes based on microbial ecological strategies and functional profiles in Camellia oleifera plantations.

Use of embedding immobilized biofillers to improve hydrolysis acidification efficiency in domestic wastewater treatment.

This study evaluated the effectiveness of embedding immobilization technology in wastewater treatment and its capacity to enhance the hydrolysis acidification process. Based on this technology, a stable anaerobic environment has been maintained. Results showed that the rates of dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) conversion both exceeded 98 % under short hydraulic retention time (HRT = 2h) and ambient temperature. Notably, acetic acid and propionic acid comprised up to 90.9 % of the total volatile fatty acids in the effluent, providing suitable carbon sources for downstream denitrification. 16S rRNA gene sequencing indicated that biofillers effectively enriched and retained functional bacteria, causing norank_Anaerolineaceae (11.6 %-29.7 %) and norank_Bacteroidetes_vadinHA17 (10.8 %-14.9 %) as the dominant genera in the reactor, which were crucial for refractory organic matter degradation. Immobilized biofillers effectively improved wastewater biodegradability, supporting a stable microbial community with high DON and DOP conversion rates as well as increased VFA accumulation.

Electro-mediated cathodic oxygen drives respiration chain electron transfer of electroactive bacteria to enhance refractory organic biological oxidation.

In electro-mediated biological system (EMBS), biological anode and cathode components were incorporated into an anaerobic bioreactor, providing a small amount of oxygen to the cathode as an electron acceptor. Oxygen diffusion also impacts the anode's anaerobic ecological environment. This study unraveled how oxygen influences the metabolism and electron transport chain during the biological oxidation of refractory organics. Under the influence of electromotive force, the straight-chain model pollutant N,N-dimethylformamide (DMF) showed rapid degradation and better ammonification, with maximum rates reaching 0.53 h-1 and 26.6 %, respectively. Elevated electromotive force promoted the enrichment of functional electroactive bacteria on the anode and enhanced the availability of electron storage sites, thereby facilitating electron transfer at the anode-biofilm interface. Conversely, the anodic micro-aerobic environment disrupted the anaerobic microbial community structure, and the competitive interactions among fermentative bacteria and electroactive bacteria inhibited DMF degradation. Metagenomic analysis confirmed that cathodic oxygen up-regulated the pyruvate metabolism and the tricarboxylic acid (TCA) cycle to generate NADH and synthesize ATP. The electromotive force induced by cathodic oxygen accelerated the electron transfer in respiratory chains of electroactive bacteria, driving the oxidation of NADH and enhancing the degradation of organics. This study improves our understanding of the regulatory mechanisms governing metabolic pathways under the influence of cathodic oxygen. It offers potential for developing more efficient EMBS in industrial wastewater pretreatment, ensuring that oxygen is prevented from diffusing to the anode during micro-aeration at the cathode.

Biochar amendment affects the microbial genetic profile of the soil, its community structure and phospholipid fatty acid contents.

Biochar (BC) amendment has been proposed as a promising strategy for mitigating greenhouse gas (GHG) emissions, specifically carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Conducting a meta-analysis to evaluate the impact of biochar on microbial genetic profile, community structure, and phospholipid fatty acid (PLFA) contents can aid in identifying key microbial groups involved in GHG production and consumption, and assessing the overall effectiveness of biochar in reducing GHG emissions. The present meta-analysis revealed that the addition of biochar resulted in a 22 % and 41 % reduction in pmoA and mcrA genes of methanogenic microorganisms, respectively. The mcrA/pmoA ratio significantly increased by 81 %. Gene abundances exhibited a positive response to biochar amendment, with increases observed in nifH, nirK, nirS, nosZ, and nosZ (nirS + nirK) genes by 13 %, 32 %, 37 %, 42 %, and 79 %, respectively. Moreover, biochar amendment influenced the microbial community structure accordingly. The concentration of PLFAs increased in response to BC treatment in the following order: A-bacteria (+49 %) < Fungi (+30 %) < Gram-pb (+21 %) < G-bacteria (+17 %) < Gram-nb (+11 %). These findings indicate that biochar amendment shapes the microbial community structure, further emphasizing its significance in enhancing soil fertility.

Coniferous Tree Species Identity and Leaf Aging Alter the Composition of Phyllosphere Communities Through Changes in Leaf Traits.

Phyllosphere microorganisms are essential for plant growth and health. Although there are an increasing number of studies showing that the composition of phyllosphere communities varies among different plant species, it remains unclear whether and how their bacterial and fungal community composition predictably varies with plant traits and leaf age. In this study, we used high-throughput sequencing to explore the diversity and composition of phyllosphere communities in needles of different ages (originating from different cohorts) for three evergreen coniferous species (Pinus koraiensis, Picea koraiensis, and Abies nephrolepis). Our results indicated that Gammaproteobacteria (bacteria) and Dothideomycetes (fungi) were dominant in newly formed needles, whereas Actinobacteria (bacteria) and Eurotiomycetes (fungi) were dominant in perennial needles. Tree species identity and needle age were the main factors explaining the variations of the α diversity (species richness of phyllosphere communities) and ß diversity (dissimilarity among phyllosphere communities). In particular, we found that leaf dry matter content, leaf mass per area, and total phosphorus content emerged as key predictors of composition and diversity of phyllosphere microbial communities, underscoring the major influence of tree species identity and needle age on phyllosphere communities through changes in plant functional traits. Finally, we found that the interaction between tree species identity and needle age also contributed significantly to explaining the diversity and composition of phyllosphere communities, probably because differences in plant functional traits or environmental conditions between new and perennial needles depend on tree growth rates and resource acquisition strategies. These findings provide new insights into the mechanisms of community assembly among different evergreen tree species and offer a better understanding of the interactions between plant traits and phyllosphere microorganisms during needle aging.

Investigation of Nitrogen Removal in Flue Gas Desulfurization and Denitrification Wastewater Utilizing Halophilic Activated Sludge.

In the process of flue gas desulfurization and denitrification, the generation of high-sulfate wastewater containing nitrogen is a significant challenge for biological wastewater treatment. In this study, halophilic activated sludge was inoculated in a Sequencing Batch Reactor to remove nitrogen from wastewater with a high sulfate concentration (60 g/L). With the influent concentration of 180 mg/L, the removal rate of total nitrogen was more than 96.7%. The effluent ammonium nitrogen concentration was lower than 1.94 mg/L, and the effluent nitrate nitrogen and nitrite nitrogen concentrations were even lower than 0.77 mg/L. The salt tolerance of activated sludge is mainly related to the increase in the content of ectoine in microbial cells. The Specific Nitrite Oxidation Rate is quite low, while the Specific Nitrite Reduction Rate and Specific Nitrate Reduction Rate are relatively strong. In the system, there are various nitrogen metabolic processes, including aerobic nitrification, anaerobic denitrification, and simultaneous nitrification-denitrification processes. By analyzing the nitrogen metabolic mechanisms and microbial community structure of the reaction system, dominate bacteria can be identified, such as Azoarcus, Thauera, and Halomonas, which have significant nitrogen removal capabilities.

Artificial river flow regulation triggered spatio-temporal changes in marine macrobenthos of the Yellow River Estuary.

The Water Sediment Discharge Regulation (WSR) in the Yellow River transports a vast quantity of freshwater and materials to the Bohai Sea within 20 days, significantly altering the ambient environment of the estuary. To elucidate the ecological impacts of this typically artificial flood event, we investigated the benthic habitats and macrobenthic biodiversity within the Affected Core Area (ACA) influenced by this discharge. Our results show that: (1) The discharge created an area with extreme environmental conditions, extending from the southern estuary to Laizhou Bay. This led to a rapid transformation of the habitat, as evidenced by a significant increase in turbidity, ammonium, and silicate levels. Among these factors, nitrogen nutrients and pH were the dominant drivers of environmental filtration, shaping the macrobenthos community structure; (2) The changing habitat triggered spatial shifts in macrobenthos abundance based on the distance from the estuary. Compared to the northern estuary, species composition and C-diversity in the southern area decreased significantly. These changes collectively established a short-term biodiversity front in the estuary region; (3) Community stability declined, as evidenced by a 24.20% reduction in niche width for generalist species and a 90.91% shift in specialist species. Furthermore, the connectivity between species decreased, and the average path length of the network increased, resulting in a more fragmented community structure. Notably, some ecological patches dominated by generalist species (e.g. Alpheus distinguendus) emerged. These findings enhance our understanding of marine ecological responses to artificial flood events within the context of global environmental changes.

[Structural Characteristics of Phytoplankton Communities and Its Relationship with Environmental Factors in Different Habitats of Hedi Reservoir].

To explore the characteristics of phytoplankton communities and their relationship with environmental factors in different habitats of Hedi Reservoir, the inflow rivers, estuaries, and reservoir area of Hedi Reservoir were investigated in February （recession period）, April （flood period）, July （flood period）, and December （recession period） of 2022. During the investigation, 231 species of phytoplankton that belong to seven phyla were identified, and the cell density of phytoplankton ranged from 2.94 × 106 - 8.04 × 108 cells·L-1. Phytoplankton cell density in flood periods were higher than that in recession periods, and that was higher in estuaries and the reservoir area than that in inflow rivers. Meanwhile, the cell density of phytoplankton in the estuarine and reservoir area was dominated by Cyanobacteria throughout the year, especially Raphidiopsis raciborskii, whereas the cell density of phytoplankton in inflow rivers was dominated by Cyanophyta, Chlorophyta, and Bacillariophyta. In the inflow river area, the dominant species of cyanobacteria were Microcystis aeruginosa, Limnothrix redekei, Pseudanabaena circinalis, and Merismopedia punctata； the dominant species of Chlorophyta were Chlorella vulgaris and Crucigenia tetrapedia； and the dominant species of Bacillariophyta were Chlorella vulgaris and Melosira granulate. The highest biodiversity （Shannon-Wiener Index, Pielou index, and Margalef index） were observed in the inflow river area of Hedi Reservoir. The correlation analysis （Pearson） indicated that the environmental factors that were significantly correlated to phytoplankton communities included water temperature, dissolved oxygen, pH, conductivity, nitrogen, and phosphorus concentration. The RDA analysis indicated that phytoplankton communities in the inflow river area were mainly affected by pH and total nitrogen concentration, which were majorly affected by water temperature and pH in the estuarine area and chiefly affected by turbidity and pH in the reservoir. The pH affected the changes in phytoplankton communities in all three different habitats, whereas the inflow river area was significantly affected by total nitrogen concentration, and the estuarine and reservoir were significantly affected by water temperature and turbidity, respectively.

[Changes in Phytoplankton Community Structure in Qingcaosha Reservoir Based on Time Series Analysis].

Qingcaosha Reservoir is one among the important reservoirs and drinking water sources in Shanghai. Samples were collected from the reservoir every month from 2014 to 2021 to analyze phytoplankton community structure and water environmental factors to provide a reasonable reference for urban reservoir operation management, water resource protection, and development and utilization. The results showed that 561 species of phytoplankton were identified from eight phyla in 8a, mainly diatomata, chlorophyta, and cyanophyta, accounting for 34.94%, 34.58%, and 17.65% of the total species, respectively. A total of 26 dominant species were present in four phyla, and cyanobacteria accounted for 50%. Diatoms and green algae were the dominant species, cyanobacteria was the absolute dominant species, and other phyla accounted for a low proportion in the community structure. The Qingcaosha reservoir had the tendency of transforming into a cyanobacteria-type reservoir. The major dominant genera of chlorophyta were Scenedesmus, Ankistrodesmusc, and Chlorellaceae. The dominant genera of the phylum cyanobacteria were Merismopediaceae, Microcystaceae, Aphanocapsa, and Pseudanabaenaceae. The major dominant genera of the diatoms were Cyclotella, Melosira, and Aulacoseira. The dominant genus of xanthophyta was Tribonemataceae. Phytoplankton abundance ranged from 8.391×105 to 2.115×107 cells·L-1, with an average of 6.345×106 cells·L-1. The biomass of phytoplankton varied from 0.113 to 11.903 mg·L-1, with an average of 1.538 mg·L-1. The maximum abundance occurred in summer, and the maximum biomass occurred in spring. In spatial distribution, the maximum biomass and abundance appeared in the reservoir. Redundancy analysis （RDA） of phytoplankton community structure and water environmental factors showed that water temperature （WT）, dissolved oxygen （DO）, and nutrient salts （TN, TP） were important environmental factors affecting phytoplankton community structure, and significant changes occurred in 2014-2017 and 2018-2021. From 2018 to 2021, cyanobacteria disappeared and cyanobacteria dominated the reservoir and even changed to cyanobacteria-type reservoirs. From 2016 to 2021, half of the dominant species were cyanobacteria, and the cyanobacteria abundance accounted for the highest proportion during this period. The reasons for the extinction of xanthophyta were speculated to be the increase in phosphorus concentration and water temperature, and the reasons for the dominant position of cyanophyta, to be the rise of water level, water temperature, and alkaline water. Reservoirs use filter-feeding fish to control algal overgrowth； however, filter-feeding fish do not filter all algae and not all of their filter-feeding algae is easily digestible. In this study, it was observed that the size of digestible algae biomass in the four seasons was in the order of spring > summer > autumn > winter. RDA analysis of silver carp, bighead carp, and digestible algae showed that the biomass of digestible algae was positively correlated with that of silver carp and bighead carp in spring, autumn, and winter. These results suggest that the digestibility of algae changed the resource use efficiency of filter-feeding fish and led to changes in phytoplankton community structure. The phytoplankton community structure was directly affected by the descending effect of fish and indirectly affected by the digestibility of algae.

[Diversity and Functional Characteristics of Fungal Communities and Influencing Factors in Typical Paddy Fields of China].

To investigate the structure, diversity, and function of different paddy soil fungal communities and the factors affecting them in typical paddy cropping areas in China, five typical Chinese paddy soils were selected in this study, and the composition and diversity of soil fungal communities were comparatively analyzed using high-throughput sequencing technology and functionally predicted using the FUNGuild microecological tool. The results showed that： ① The fungal community diversity of soil samples from Heilongjiang （HLJ） was significantly lower than that of the other four regions （P<0.05）； the highest fungal community richness was found in paddy soils from Yunnan （YN）, which was significantly higher than that of the other regions （P<0.05）； and the soil samples from Hainan （HN）, Jiangxi （JX）, and Shandong （SD） were relatively close to each other. The highest average relative abundance at the level of the five typical paddy phyla was Ascomycota, and the genus with the highest average relative abundance was Tausonia. ② Fungi had the largest proportion of saprophytic trophic types, and their corresponding environmental functions were stronger. ③ The species abundance of soil fungi was highly significantly correlated with soil TP, EC, and BD （P<0.01）, and redundancy analyses also showed that soil TP was the main driver of the fungal community as well as the saprophytic functional taxa. The above results showed that the soil fungal community diversity and structure varied greatly among samples, and the relative abundance of fungal genera was affected by soil physical and chemical properties and altered the fungal community structure in paddy fields. The development of this study will provide theoretical references for the sustainable management based on fungal diversity and function of paddy fields.