Altered Community Structure Research Articles

Effects of Different Preservation Methods on the Structure and Diversity of Intestinal Microbiota of Marine Fishes.

The fish intestine is a complex ecosystem where microbial communities are dynamic and influenced by various factors. Preservation conditions during field collection can introduce biases affecting the microbiota amplified during sequencing. Therefore, establishing effective, standardized methods for sampling fish intestinal microbiota is crucial. This study used hybrid groupers (Epinephelus fuscoguttatus♀ × E. lanceolatus♂) to examine the effects of six preservation methods: dry ice (1 day), dry ice (1 day) followed by -80°C storage (5 days), liquid nitrogen (1 day), liquid nitrogen (1 day) with subsequent -80°C storage (5 days), refrigeration at 4°C (3 days), and freezing at -20°C (3 days), with fresh samples as controls. High-throughput 16S rRNA sequencing assessed microbial diversity, community structure, dominant species, and OTU abundance across treatments. Results indicated that dry ice and liquid nitrogen methods, especially with -80°C storage, had minimal impact on microbial diversity and structure. Compared to other preservation methods, refrigeration at 4°C and freezing at -20°C may result in suboptimal reproducibility and altered community structure, particularly affecting rare microbial taxa. This study underscores the need for standardized preservation techniques to ensure accurate fish intestinal microbiota analysis and provides a foundation for future research.

Review of mayflies (Insecta Ephemeroptera) as a bioindicator of heavy metals and microplastics in freshwater.

Heavy metal and microplastic pollutions are prevalent in freshwater ecosystems, with many freshwater bodies being contaminated by one or both of these pollutants. Recent studies reported extreme detections of Cd, Pb and Zn, high concentrations of Cr, Pb and Cu and microplastics acting as vectors of pollutants, including heavy metals. Mayflies can serve as bioindicators of heavy metal contamination in freshwater ecosystems because changes in their community structure, physiology, and behaviour can reflect and help predict the concentrations of metals in these environments. This review discusses the ecological alterations induced by tissue metal concentration in mayflies and other macroinvertebrates. As sensitive taxa to heavy metal contamination, mayflies can reflect the impacts of this pollution through their ethology and relationship to the substrate, highlighting issues such as eutrophication, alterations in community structure, inhibitory effects and sediment toxicity. Mayflies are also highly affected by microplastic exposure, which leads to ingestion, bioaccumulation, biomagnification, habitat and community alteration, behavioural changes, physiology alteration and toxicity. Mayflies bioindication metrics for assessing the impact of heavy metals and microplastics include the examination of community alteration, functional feeding behaviour, molecular structure, dietary and toxicity impacts, bioaccumulation and biomagnification and biomarkers. Current challenges for the utilization of mayflies as bioindicators include temporal variations in sensitivity, lack of universally recognised protocols and need for standardised protocols for microplastic analysis. Additionally, the applicability of mayflies as bioindicators may vary across different ecosystems, emphasising the need for selecting suitable indicators that align with the unique characteristics of the ecosystem.

Polyethylene microplastics distinctly affect soil microbial community and carbon and nitrogen cycling during plant litter decomposition

Plant litter is an important input source of carbon and nitrogen in soil. While microplastics (MPs) and plant litter are ubiquitously present in soil, their combined impact on soil biogeochemical processes remains poorly understood. To address this gap, we examined the soil changes resulting from the coexistence of plant litter (Alfalfa) and polyethylene microplastics (PE). The soil changes included physicochemical properties, composition of soil dissolved organic matter, and structure of the soil microbial community. The results showed that the addition of polyethylene (PE) inhibited the degradation of humus-like substances and decreased the quantity of humic acid-like compounds in soil dissolved organic matter (DOM). PE negatively impacted plant litter decomposition, disrupted soil organic carbon (SOC) breakdown, interfered with the nitrogen cycle, and significantly altered microbial community structures during the process. By day 35, SOC and total nitrogen (TN) levels were reduced by 39.8% and 10.1%, respectively, in the presence of PE. Furthermore, PE significantly decreased the abundance of nitrogen-fixing microbes, including Streptomyces (43.1%) and Bacillus (45.9%), which play key roles in nitrate reduction to ammonium. This study highlights the environmental effects of MPs on plant litter decomposition and their potential implications for soil biogeochemical processes.

Litter removal increases plant diversity by promoting both native and exotic forbs in heavily invaded coastal sage scrub in Southern California, U.S.A.

Litter produced by exotic grasses is known to negatively impact native species through multiple mechanisms. While litter removal is a potential restoration tool to recover native species, the effects of litter removal on overall plant community structure are not well understood as most studies focus on native species recovery. In a litter removal experiment in Southern California, U.S.A., we found that plant communities receiving litter removal treatment differed in species composition from control plots and had 4.4% higher native forb relative abundance and 7.0% higher exotic forb relative abundance, on average. These changes in exotic and native forb abundance with litter removal altered community structure by increasing overall Shannon diversity, while only having a modest positive effect on overall species richness. In contrast, we found no effect of litter removal on the species richness or Shannon diversity of native species. Taken together, these findings suggest that in herbaceous systems litter removal is likely to alter community composition primarily by increasing the abundance of native and exotic forbs already present in the community, rather than by allowing the establishment of new native species. Our study adds to a growing body of literature demonstrating that litter produced by exotic grasses inhibits native forbs in California grasslands and coastal sage scrub and highlights a potential trade‐off between controlling exotic grass invaders and controlling exotic forb invaders. If managing for increased species diversity is the goal, litter removal may be an appropriate intervention to move plant communities toward a more diverse state.

Hybrid Soybean as Green Manure for Improving Soil Properties and Subsequent Crop Growth

The rapid increase in fertilizer use has led to the degradation of soil quality, nutrient imbalances, reduced biodiversity, and soil compaction. To address these challenges, hybrid soybeans with efficient biological nitrogen fixation capabilities and broad environmental adaptability were selected as green manure to reduce fertilizer application, thereby improving soil fertility and structure. This study utilized the varieties “Forage Soybean S001” (S001), “Neinong S002 Forage Soybean” (S002), “Mengnong S003 Forage Soybean” (S003), “Mengnong S004 Forage Soybean” (S004), “Mengnong S005 Forage Soybean” (S005), and “Mengnong S006 Forage Soybean” (S006) as green manure materials. The clean tillage (CK) treatment served as the control, ensuring a residue-free soil surface while maintaining consistent practices in soil preparation, irrigation, and field management across all treatments. Field planting of green manure and subsequent crops was conducted at the M-Grass Ecology and Environment (Group) Company’s experimental site in Hohhot in early May of 2023 and 2024. The plots each measured 20 m2, with three replications arranged in a randomized block design. A combination of field experiments and laboratory analyses was utilized to investigate the effects of incorporating various hybrid soybean varieties as green manure on soil nutrient levels, soil enzyme activity, soil microbial communities, and the subsequent growth of oats. The results indicated that incorporating various hybrid soybean varieties as green manure into the soil significantly improved soil nutrient levels and enzyme activity. The diversity and richness of soil bacterial communities increased significantly, accompanied by alterations in community structure and composition. These changes enhanced soil fertility and optimized the microbial community structure, promoting the growth of subsequent crops. Among all the treatments, S001 and S004 were particularly effective in enhancing the soil environment, indicating their potential as superior green manure resources for broader application.

Phage-induced disturbance of a marine sponge microbiome

BackgroundBacteriophages are known modulators of community composition and activity in environmental and host-associated microbiomes. However, the impact single phages have on bacterial community dynamics under viral predation, the extent and duration of their effect, are not completely understood. In this study, we combine morphological and genomic characterization of a novel marine phage, isolated from the Baltic sponge Halichondria panicea, and report on first attempts of controlled phage-manipulation of natural sponge-associated microbiomes.ResultsWe used culture-based and culture-independent (16S rRNA gene amplicon sequencing) methods to investigate bacterial community composition and dynamics in sponge microbiomes with and without the addition of phages. Upon application of a novel Maribacter specialist phage Panino under controlled conditions, we were able to detect community-wide shifts in the microbiome composition and load after 72 h. While bacterial community composition became more dissimilar over time in the presence of phages, species evenness and richness were maintained. Upon phage exposure, we observed the loss of several low-abundance constituent taxa of the resident microbiota, while other originally underrepresented taxa increased. Virulent phages likely induce community-wide disturbances, evident in changes in the total sponge microbial profile by specific elimination of constituent taxa, which leads to an increase in bacterial abundance of opportunistic taxa, such as the genera Vibrio, Pseudoalteromonas, and Photobacterium.ConclusionsOur findings suggest that sponge microbiome diversity and, by extension, its resilience depend on the maintenance of resident bacterial community members, irrespective of their abundance. Phage-induced disturbances can significantly alter community structure by promoting the growth of opportunistic bacteria like Vibrio and shifting the microbiome to a dysbiotic state. These insights highlight the role of bacteriophages in shaping microbiome dynamics and underscore the potential for phage application in managing bacterial community composition in marine host-associated environments.

Factors Contributing to Rotary International’s Stagnant Membership Growth

This paper explores the multifaceted reasons behind Rotary International’s stagnant membership growth over the last decades. A significant factor identified is the lack of outreach and marketing efforts, which has prevented the organization from effectively engaging with diverse communities and adapting to modern promotional strategies. This has resulted in a membership base that does not reflect the changing societal dynamics and fails to attract younger generations who prioritize different causes, such as environmental sustainability and social justice. Additionally, the challenges faced by smaller organizations, such as limited resources and niche appeal, are relevant to Rotary’s struggle to attract new members. External societal trends, including urban development and globalization, have altered community structures and priorities, further influencing membership dynamics. The paper highlights the importance of adapting to these changes by improving outreach efforts, addressing competition from other service organizations, and fostering strong leadership within Rotary International. The discussion emphasizes the potential strategies Rotary International can adopt to enhance membership growth, such as leveraging social networks, fostering organizational identification, and addressing diversity challenges. By integrating these strategies, Rotary can work towards increasing its membership and continuing its mission of positively impacting society.

Ecosystem damage by increasing tropical cyclones

Climate change is driving an ongoing increase in tropical cyclone (TC) activity. While global economic losses are projected to double by 2100, there are no comparable predictions for TC impacts to coastal ecosystems that protect and sustain human lives and livelihoods. Here, rising North Atlantic TC (NATC) activity from 1970 to 2019, influenced by anthropogenic and natural climate forcing, is used to study the ecosystem impacts of intensifying TCs, potentially indicative of broader future climate change scenarios. Analysis of 97 NATC landfalls revealed 891 immediate post-storm impacts on ecosystems, with particularly detrimental effects on mangrove forests. Specifically, NATCs reduced the performance of individual species. Additionally, they altered community structure and processes through impacts on foundation species and their associated organisms. The severity of impacts was directly correlated with NATC landfall intensity (wind speed) for mangroves, whereas changes to waves, surge, sediments, and salinity caused most impacts on coral reefs, salt marshes, seagrass meadows, and oyster reefs (respectively), indicating complex intensity-damage interactions for many ecosystems. The analyses also revealed a positive correlation between very intense NATC activity and ecosystem damages. The research highlights a concerning trend of escalating impacts on coastal ecosystems under rising storm intensities, with the potential to challenge ecosystem resilience.

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 MHW in the coastal water of southern China. After 8 days of the MHW (+3 °C) 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 °C 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.

Pb pollution altered bacterial community assembly and predicted functions in aggregate-size fractions of agricultural soil near a smelter

In order to investigate the impact of Pb smelter pollution on bacterial community structure, diversity and function at the microenvironment scale, the maize rhizosphere soils subjected to long-term (over 20 years) Pb smelter pollution were collected, and bacterial communities and putative functions in different aggregate-size fractions were identified by 16S rRNA sequencing, KEGG and FAPROTAX. The results showed that Pb pollution significantly diminished bacterial diversity, and prompted a shift in the bacterial communities toward more oligotrophic taxa, including Firmicutes, Chloroflexi, and Gemmatimonadetes. Furthermore, the functional subcategories related to cell motility and energy metabolism, as well as the functional groups involved in carbon (C), nitrogen (N), and sulfur (S) cycles, exhibited a marked decline under Pb pollution. At the aggregate scale, distinct differences were observed in the composition of bacterial communities across silt and clay (<250 μm), micro-aggregates (250–1000 μm), and macro-aggregates (1000–2000 μm and >2000 μm) in uncontaminated soils. However, Pb pollution disrupted these original distinctions among bacterial communities in various aggregate-size fractions, with a decreased abundance of dominant Proteobacteria and an increased abundance of Firmicutes in large aggregates. While the differences in bacterial functional groups in aggregate-size fractions were also detected. The functional groups associated with C and N cycles were significantly enriched in the macro-aggregates (1000–2000 μm) in uncontaminated soils. However, similar with the change of bacterial community structure, most functional groups (except for chemoheterotrophy) in aggregate-size fractions exhibited no significant differences under Pb exposure. Our results suggested that Pb pollution altered bacterial community structure and predicted functions at the aggregate level, and showed greater negative effects on bacterial functions in macro-aggregates (1000–2000 μm). This study can provide a new perspective for the influence of Pb smelter pollution on soil aggregate microenvironment.

Diffusive Phyllosphere Microbiome Potentially Regulates Harm and Defence Interactions Between Stephanitis nashi and Its Crabapple Host.

Pear lace bug (Stephanitis nashi) is a significant herbivorous pest, harbouring a diverse microbiome crucial for crabapple (Malus sp.) host adaptation. However, the mutual influence of S. nashi- and plant-associated microbiomes on plant responses to pest damage remains unclear. This study found that S. nashi damage significantly altered bacterial community structure and reduced bacterial evenness in the crabapple phyllosphere. Notably, bacterial diversity within S. nashi was significantly lower than that in the environment, potentially influenced by insect developmental stage, bacterial diffusion stage and endosymbiont species number and abundance. Extensive bacterial correlation and diffusion effect between S. nashi and adjacent plant environments were observed, evident in a gradual decrease in bacterial diversity and an increase in bacterial acquisition ratio from soil to phyllosphere to S. nashi. Correspondingly, S. nashi significantly impacted the metabolic response of crabapple leaves, altering pathways involved in vitamin, amino acid and lipid metabolism and so forth. Furthermore, association analysis linked these metabolic changes to phyllosphere bacterial alterations, emphasizing the important role of diffusive phyllosphere microbiome in regulating S. nashi-crabapple interactions. This study highlights bacterial diffusion effect between insect and plants and their potential role in regulating insect adaptability and plant defence responses, providing new insights into plant-insect-microbiome interactions.

Conversion to Greenhouse Cultivation from Continuous Corn Production Decreases Soil Bacterial Diversity and Alters Community Structure

Changes in crop types and long-term monoculture substantially impact soil microbial communities. Exploring these changes and their influencing factors is of great significance for addressing the challenges posed by continuous cropping. Soil surface layer samples from greenhouse tomatoes fields cultivated for 5 (Y5), 9 (Y9), 13 years (Y13), and a surrounding corn field (CK) as a control were analyzed. The Y13 sample showed a significant increase in the relative abundance of Pseudomonadota (43.1%) and a decrease in Actinobacteria (50.3%) compared to the CK sample. Soil bacterial alpha diversity generally declined from the CK to Y13 (0.1–22.2%) sample, with a small peak in Y9 for Chao1 and Observed_species. Significant differences in Chao1 and Observed_ species were observed between the CK and Y13 samples. Beta diversity analysis revealed a pronounced variation in soil bacterial community structure across planting years, with the divergence from the CK sample intensifying over time. In comparison to the Y5 vs. CK samples, Y9 and Y13 exhibited marked differences from the CK across the same and broader metabolic pathways, suggesting a potential convergence of microbial activities over time. The Y9 and Y13 samples showed significantly higher biosynthesis abundance (7.50% and 6.36%, respectively) than the CK. In terms of soil physicochemical indices, the carbon–nitrogen ratio was the primary factor influencing soil bacterial composition. In conclusion, we found that crop alteration and continued planting changed the soil’s bacterial composition and increasing planting years suppressed the soil’s bacterial diversity, leading to a stable bacterial ecology after nine years. Implementing appropriate measures during this critical period is vital for optimal soil utilization.

Parasites disrupt a keystone mutualism that underpins the structure, functioning, and resilience of a coastal ecosystem

AbstractParasites can alter the traits or densities of mutualistic partners, potentially destabilizing mutualistic associations that underpin the structure, functioning, and stability of entire ecosystems. Despite the potentially wide‐ranging consequences of such disruptions, no studies have directly manipulated parasite prevalence and/or intensity in a mutualistic partner, nor quantified the resulting community‐level effects. Here, we investigated the effects of a common trematode parasite (Cercaria opaca) on the strength of a keystone facultative mutualism in western Atlantic salt marshes between the foundational marsh cordgrass, Spartina alterniflora, and the ribbed mussel, Geukensia demissa. Cordgrass increases mussel survivorship and growth through shading, while mussels enhance cordgrass growth by producing nutrient‐rich biodeposits. This mutualistic association also creates conditions that enhance biodiversity and ecosystem functioning, and mediates the ability of foundational plants to resist and recover from extreme drought. We used lab and field assays to show how increasing infection with trematode metacercariae negatively influenced mussel biodeposit production, as well as the strength of mussel shells and byssal attachments. By conducting a field manipulation using experimentally infected mussels, we demonstrated that the mutualistic benefits of mussels to cordgrass growth decreased with increasing trematode infection intensity—a pattern likely generated by reduced mussel biodeposition and enhanced mortality. Additionally, increasing parasite loads in mussels led to predictable decreases in the abundances of benthic invertebrates, as well as in key ecosystem characteristics and process rates (i.e., redox potential and sediment accretion). Finally, a survey of five North Carolina salt marshes demonstrated that infection with C. opaca was most common in mussels in areas experiencing cordgrass die‐off due to drought, and that infection intensity decreased with distance from die‐off areas. Because the mussel–cordgrass mutualism underpins marsh ecosystem resilience to drought‐associated die‐off, our results suggest that parasitism may depress recovery from these disturbances. Although this is the first experimental demonstration of parasites indirectly altering community structure and functioning by undermining an ecologically influential mutualism, this type of relationship could be common in nature, given that parasites frequently infect influential mutualists.

Recovery of 1559 metagenome-assembled genomes from the East China Sea’s low-oxygen region

The Changjiang Estuary and adjacent East China Sea are well-known hypoxic aquatic environments. Eutrophication-driven hypoxia frequently occurs in coastal areas, posing a major threat to the ecological environment, including altering community structure and metabolic processes of marine organisms, and enhancing diversion of energy shunt into microbial communities. However, the responses of microbial communities and their metabolic pathways to coastal hypoxia remain poorly understood. Here, we studied the microbial communities collected from spatiotemporal samplings using metagenomic sequencing in the Changjiang Estuary and adjacent East China Sea. This generated 1.31 Tbp of metagenomics data, distributed across 103 samples corresponding to 8 vertical profiles. We further reported 1,559 metagenome-assembled genomes (MAGs), of which 508 were high-quality MAGs (Completeness > 90% and Contamination < 10%). Phylogenomic analysis classified them into 181 archaeal and 1,378 bacterial MAGs. These results provided a valuable metagenomic dataset available for further investigation of the effects of hypoxia on marine microorganisms.

Effects of Pre-Dehydration Treatments on Physicochemical Properties, Non-Volatile Flavor Characteristics, and Microbial Communities during Paocai Fermentation.

The paocai industry faces challenges related to the production of large volumes of high-salinity and acidic brine by-products. Maintaining paocai quality while reducing brine production is crucial. This study utilized high-throughput sequencing technology to analyze microbial changes throughout the fermentation process, along with the non-volatile flavor compounds and physicochemical properties, to assess the impact of hot-air and salt-pressing pre-dehydration treatments on paocai quality. The findings indicate that pre-dehydration of raw material slowed the fermentation process but enhanced the concentration of non-volatile flavor substances, including free amino acids and organic acids. Hot-air pre-dehydration effectively reduced initial salinity to levels comparable to those in high-salinity fermentation of fresh vegetables. Furthermore, pre-dehydration altered microbial community structures and simplified inter-microbial relationships during fermentation. However, the key microorganisms such as Lactobacillus, Weissella, Enterobacter, Wallemia, Aspergillus, and Kazachstania remained consistent across all groups. Additionally, this study found that biomarkers influenced non-volatile flavor formation differently depending on the treatment, but these substances had minimal impact on the biomarkers and showed no clear correlation with high-abundance microorganisms. Overall, fermenting pre-dehydrated raw materials presents an environmentally friendly alternative to traditional paocai production.

The Response of Rhizosphere Microbial C and N-Cycling Gene Abundance of Sand-Fixing Shrub to Stand Age Following Desert Restoration.

Rhizosphere microorganisms play a pivotal role in biogeochemical cycles, particularly in relation to carbon (C) and nitrogen (N) cycles. However, the impact of stand age on the composition of rhizosphere microbial communities and the abundance involved in C and N cycling remains largely unexplored in restoration ecosystems dominated by shrubs of temperate deserts. This study focuses on revealing changes in microbial composition and functional genes in the rhizosphere soil of Caragana korshinskii after revegetation, as well as their response mechanisms to changes in environmental factors. The alpha diversity of bacteria tended to increase with stand age, whereas that of fungi decreased. The abundance of denitrification; dissimilatory nitrate reduction to ammonium, nitrification, and ammonium assimilation; and C fixation-related gene levels increased with stand age, whereas those related to the degradation of starch, pectin, hemicellulose, cellulose, and aromatics decreased. The parameters MBC, MBN, and TC were the key factors affecting the bacterial community, whereas the fungal community was regulated by TN, EC, pH, and MBC. Stand age indirectly regulated C and N cycling functions of genes through altered soil properties and microbial community structures. This study presents a novel approach to accurately evaluate the C and N cycling dynamics within ecosystems at various stages of restoration.

DHA-enriched phosphatidylserine ameliorates cyclophosphamide-induced liver injury via regulating the gut-liver axis

ObjectiveThis study explores the therapeutic effects and mechanisms of DHA-enriched phosphatidylserine (DHA-PS) on liver injury induced by cyclophosphamide (CTX) in mice, focusing on the gut-liver axis. MethodsA mouse model was established by administering CTX (80 mg/kg) intraperitoneally for 5 days. DHA-PS (50 or 100 mg/kg) was administered for the next 7 days to assess its reparative impact on liver damage. ResultsThe findings revealed significant improvements in liver biochemical indices, inflammatory markers, and oxidative stress levels in the mice treated with DHA-PS. Through non-targeted metabolomics analysis, DHA-PS mitigated CTX-induced metabolic disruptions by modulating lipid, amino acid, and pyrimidine metabolism. Immunofluorescence analysis further confirmed that DHA-PS reduced the expression of liver-associated inflammatory proteins by inhibiting the TLR4/NF-κB pathway. Additionally, DHA-PS restored the intestinal barrier, evidenced by adjustments in the levels of intestinal lipopolysaccharide (LPS), secretory immunoglobulin A (sIgA), and tight junction proteins (Claudin-1, Occludin, and ZO-1). It also improved gut microbiota balance by enhancing microbial diversity, increasing beneficial bacteria, and altering community structures. ConclusionThese results suggest that DHA-PS could be a potential therapeutic agent or functional food for CTX-induced liver injury through its regulation of the gut-liver axis.

Effects of Acid Mine Drainage Leakage on Bacterial Communities in Desert Grassland Soil Profiles

Acid mine drainage （AMD） is of great concern owing to its safety hazards and environmental risks. However, little is known about the effects of AMD leakage on soil physicochemical properties and bacterial communities in ecologically fragile desert steppe soils, especially in the soil profile. Therefore, an AMD-contaminated profile and clean profile were used as research objects respectively to investigate the effects of AMD on soil physicochemical properties and bacterial community composition, structure, and interactions in soil layers at different depths of desert grassland and, based on this, to analyze the driving factors of bacterial community changes. The results showed that AMD significantly decreased the pH and increased electrical conductivity （EC） and heavy metal content in the upper （0-40 cm） soil layer of the profile. The AMD-contaminated profile bacteria were dominated by Proteobacteria, Firmicutes, and Actinobacterota, whereas clean profile bacteria were dominated by Firmicutes and Bacteroidota, with Thermithiobacillus and Alloprevotella being the biomarkers for the contaminated and clean profiles, respectively. AMD contamination significantly reduced bacterial diversity and significantly altered bacterial community structure in the upper soil layers of the profile. The results of redundancy analysis showed that soil physicochemical properties explained 57.21% of the variation in bacterial community changes, with EC, TP, TN, As, Zn, and Pb being the main drivers of bacterial community changes. Network analyses showed that AMD contamination increased profile complexity, modularity, and intra-community competition, thereby improving bacterial community stability and resilience. In conclusion, the study provided useful information on the effects of AMD pollution on soil physicochemical properties and bacterial communities in desert steppe soils, which may help to improve the understanding of the ecological hazards of AMD pollution on soils in extreme habitats.

Microplastics predominantly affect gut microbiota by altering community structure rather than richness and diversity: A meta-analysis of aquatic animals

The impacts of microplastics on the gut microbiota, a crucial component of the health of aquatic animals, remain inadequately understood. This phylogenetically controlled meta-analysis aims to identify general patterns of microplastic effects on the alpha diversity (richness and Shannon index), beta diversity, and community structure of gut microbiota in aquatic animals. Data from 63 peer-reviewed articles on the Web of Science were synthesized, encompassing 424 observations across 31 aquatic species. The analysis showed that microplastics significantly altered the community structure of gut microbiota, with between-group distances being 87.75% higher than within-group distances. This effect was significant even at environmentally relevant concentrations (≤1 mg L−1). However, their effects on richness, Shannon index, and beta diversity (community variation) were found to be insignificant. The study also indicated that the effects of microplastics were primarily dependent on their concentration and size, while the phylogeny of tested species explained limited heterogeneity. Furthermore, variations in gut microbiota alpha diversity, beta diversity, and community structure were correlated with changes in antioxidant enzyme activities from the liver and hepatopancreas. This implies that gut microbiota attributes of aquatic animals may provide insights into host antioxidant levels. In summary, this study illuminates the impacts of microplastics on the gut microbiota of aquatic animals and examines the implications of these effects for host health. It emphasizes that microplastics mainly alter the community structure of gut microbiota rather than significantly affecting richness and diversity.

Phloem-feeding insects create parasitoid-free space for caterpillars

Seemingly small ecological changes can have large, ramifying effects that defy expectations. Such are keystone effects in ecosystems. Phloem-feeding insect herbivores can act as keystone species by altering community structure and species interactions via plant-mediated or ant-mediated mechanisms. Plant responses triggered by phloem feeders can disrupt tri-trophic interactions induced by leaf-chewing herbivores, while ants that tend phloem feeders can deter or prey on other arthropods. Here, we investigate how phloem-feeding herbivores change caterpillar-parasitoid interactions on Quercus alba (white oak) trees in natural forests. We factorially manipulated the presence of phloem-feeding insects as well as ant access on Q.alba branches over multiple years and sites and measured parasitism rates of co-occurring caterpillars. While 19.3% of caterpillars were parasitized when phloem feeders were removed, the presence of phloem feeders completely suppressed parasitism of caterpillars (0%). This stark pattern was consistent across the diverse community of phloem feeders and caterpillars. Our manipulation of ant access had no effect on parasitism of caterpillars, implicating a plant-mediated mechanism. We further assessed the mechanistic hypothesis that phloem feeders suppress plant emission of caterpillar-induced volatile compounds, which could disrupt host-location behavior by parasitoids of caterpillars. Phloem feeders indeed reduced concentrations of four volatile compounds, consistent with the putative plant volatile-mediated mechanism. Given the important role of parasitoids in controlling herbivore populations, this keystone effect of phloem feeders offers novel insight into community dynamics in forests and potentially other terrestrial ecosystems.