Community Dynamics Research Articles

Structure and dynamics of mollusk communities from intermittent rivers in Brazilian semiarid region

Structure and dynamics of mollusk communities from intermittent rivers in Brazilian semiarid region

Transient hypoxia drives soil microbial community dynamics and biogeochemistry during human decomposition.

Human decomposition in terrestrial ecosystems is a dynamic process creating localized hot spots of soil microbial activity. Longer-term (beyond a few months) impacts on decomposer microbial communities are poorly characterized and do not typically connect microbial communities to biogeochemistry, limiting our understanding of decomposer communities and their functions. We performed separate year-long human decomposition trials, one starting in spring, another in winter, integrating bacterial and fungal community structure and abundances with soil physicochemistry and biogeochemistry to identify key drivers of microbial community change. In both trials, soil acidification, elevated microbial respiration, and reduced soil oxygen concentrations occurred. Changes in soil oxygen concentrations were the primary driver of microbial succession and nitrogen transformation patterns, while fungal community diversity and abundance was related to soil pH. Relative abundance of facultative anaerobic taxa (Firmicutes and Saccharomycetes) increased during the period of reduced soil oxygen. The magnitude and timing of the decomposition responses were amplified during the spring trial relative to the winter, even when corrected for thermal inputs (accumulated degree days). Further, soil chemical parameters, microbial community structure, and fungal gene abundances remained altered at the end of 1 year, suggesting longer-term impacts on soil ecosystems beyond the initial pulse of decomposition products.

Microbial dietary preference and interactions affect the export of lipids to the deep ocean.

Lipids comprise a significant fraction of sinking organic matter in the ocean and play a crucial role in the carbon cycle. Despite this, our understanding of the processes that control lipid degradation is limited. We combined nanolipidomics and imaging to study the bacterial degradation of diverse algal lipid droplets and found that bacteria isolated from marine particles exhibited distinct dietary preferences, ranging from selective to promiscuous degraders. Dietary preference was associated with a distinct set of lipid degradation genes rather than with taxonomic origin. Using synthetic communities composed of isolates with distinct dietary preferences, we showed that lipid degradation is modulated by microbial interactions. A particle export model incorporating these dynamics indicates that metabolic specialization and community dynamics may influence lipid transport efficiency in the ocean's mesopelagic zone.

Post-fire temporal dynamics of plant-pollinator communities in a tropical savanna.

Fire is a major ecological and evolutionary factor promoting biodiversity and maintaining functioning of naturally fire-prone ecosystems. In tropical savannas, plant communities show a set of fire-adapted traits and both flowering and pollination services have the potential to rapidly regenerate after fire, but fire-suppression policies may disrupt this adaptability following potential woody encroachment. Understanding the effects of fire on plant-pollinator interactions are required to advance conservation of biodiversity and ecosystem functioning. We evaluated the dynamics of plant community assemblage, flower availability, composition of flower functional traits associated with attractiveness to pollinators, and activity and diversity of insect pollinator guilds over ten post-fire stand ages along a 14-year chronosequence in a naturally burned region in the Cerrado, a megadiverse savanna in Brazil. We expect to find a high resilience of plant-pollinator communities and a steady decline in the successional recovery as time-since-fire proceeds. Along the post-fire chronosequence, vegetation was dominated by subshrubs with tubular, white, and nectar flowers arranged in inflorescences, while bees were the predominant pollinators. Plant assemblage and flower number showed an initial significant increase but monotonically declined after 7-9years after fire. Accordingly, pollinator richness and abundance significantly reached highest peaks in interim periods and a steady decline over time. In contrast, the frequency of community-wide plant-life form, flower functional traits, and pollinator diversity remained unaltered over the post-fire chronosequence. We added compelling evidence of a high post-fire resilience of plant-pollinator communities and further understanding of how fire-suppression policies may affect pollination in the Cerrado.

A Phenomenology of Authenticity in Prison Life: Kierkegaard and the Paradox of Freedom

This paper examines the lived experiences of selected inmates, some of whom have been released from the New Bilibid Prison in Muntinlupa City, Philippines, focusing on how incarceration has transformed their lives. Confronted with significant mental and emotional challenges, the inmates embraced a new life of faith amid the harsh realities of prison life. The researchers used the phenomenological method to collect narratives from these inmates and employ thematic analysis. The paper identifies underlying themes emerging from these narratives and, in its final section, reflects on them through the theoretical framework of existential philosopher Søren Kierkegaard. Kierkegaard's concepts of the paradoxical nature of despair and the three stages of life—the aesthetic, the ethical, and the religious—provide a lens for understanding the inmates' spiritual transformation through religious participation. By integrating these philosophical insights, the authors deepened the understanding of how prison experiences influence spiritual change. The inmates' journeys from despair to spiritual awakening illuminate the existential dynamics of human freedom, authenticity, and community, as articulated by Kierkegaard. Their narratives provide compelling evidence that even in a setting where freedom is ostensibly curtailed, individuals can achieve a profound sense of liberation by embracing their despair and taking a leap of faith.

Effect of nitrogen and phosphorus fertilization on the temporal dynamics of soil microbial community and multifunctionality in young and mature subtropical forests

Effect of nitrogen and phosphorus fertilization on the temporal dynamics of soil microbial community and multifunctionality in young and mature subtropical forests

Synergistic effects of biochar and laccase on nitrogen conversation and degradations of two artificial sweeteners during the sewage sludge composting

This study investigates the effects of biochar, laccase, and their combined application on nitrogen transformation, the degradation of sucralose (SUC) and acesulfame (ACE), and the dynamics of bacterial communities during sewage sludge composting. The results indicated that NH3 emissions were reduced by 41.2 %, 17.5%, and 40.8 % in the biochar, laccase, and biochar-laccase treatments, respectively, compared to the control. Meanwhile, N2O emissions decreased significantly by 26.8 % and 16.0 % for the biochar and biochar-laccase treatments, respectively, but increased by 8.1 % for the laccase treatment. Additionally, the biochar, laccase, and biochar-laccase treatments enhanced the degradation of SUC and ACE by 36.6–68.3 % and 49.2–69.8 %, relative to the control, respectively. Network analysis showed that the additive-treatment enhanced the cooperation within bacterial communities, and solidified artificial sweeteners degradation, especially under biochar-laccase application. Phylogenetic investigation of communities by reconstruction of unobserved states further indicated that biochar, laccase, biochar-laccase treatment increased enzymes associated with the degradations of organic matter and artificial sweeteners. In conclusion, it suggested that a combined addition of biochar and laccase was an effectively way to reduce nitrogen loss and promote artificial sweeteners degradations during sewage sludge composting.

Microbial community dynamics in different floc size aggregates during nitrogen removal process upgrading in a full-scale landfill leachate treatment plant

Upgrading processes to reduce biodegradable organic substance addition is crucial for treating landfill leachate with high pollutant concentrations, aiding carbon emission reduction. Aggregate size in activated sludge processes impacts pollutant removal and sludge/water separation. This study investigated microbial community succession and driving mechanisms in different floc-size aggregates during nitrogen removal progress upgrade from conventional to partial nitrification–denitrification in a full-scale landfill leachate treatment plant (LLTP) using 16S rRNA gene sequencing. The upgrade and floc sizes significantly influenced microbial diversity and composition. After upgrading, ammonia-oxidizing bacteria were enriched while nitrite-oxidizing bacteria suppressed in small flocs with homogeneity and high mass transfer efficiency. Larger flocs enriched Defluviicoccus, Thauera, and Truepera, while smaller flocs enriched Nitrosomonas, suggesting their potential as biomarkers. Multi-network analyses revealed microbial interactions. A deep learning model with convolutional neural networks predicted nitrogen removal efficiency. These findings guide optimizing LLTP processes and understanding microbial community dynamics based on floc size.

Seasonal Dynamics of Eukaryotic Microbial Communities in the Water-Receiving Reservoir of the Long-Distance Water Diversion Project, China.

Inter-basin water transfer projects, such as the Yellow River to Qingdao Water Diversion Project (YQWD), are essential for addressing water scarcity, but impact local aquatic ecosystems. This study investigates the seasonal characteristics of eukaryotic microbial communities in the Jihongtan Reservoir, the main water-receiving body of YQWD, over a one-year period using 18S rDNA amplicon sequencing. The results showed that the eukaryotic microbial diversity did not exhibit significant seasonal variation (p > 0.05), but there was a notable variance in the community structure (p < 0.05). Arthropoda and Paracyclopina, representing the most dominant phylum and the most dominant genus, respectively, both exhibited the lowest abundance during the winter. The Chlorophyta, as the second-dominant phylum, demonstrates its higher abundance in the spring and winter. The Mantel test and PLS-PM (Partial Least Squares Path Modeling) revealed that water temperature (WT), dissolved oxygen (DO), and pH influenced the seasonal dynamic of eukaryotic microbial communities significantly, of which WT was the primary driving factor. In addition to environmental factors, water diversion is likely to be an important influencing factor. The results of the co-occurrence network and robustness suggested that the spring network is the most complex and exhibits the highest stability. Moreover, keystone taxa within networks have been identified, revealing that these key groups encompass both abundant and rare species, with specificity to different seasons. These insights are vital for understanding the seasonal variation of microbial communities in the Jihongtan Reservoir during ongoing water diversions.

Maltese Coastline Never Sleeps: The Effects of Artificial Light at Night (ALAN) on the Local Infralittoral Assemblages—A Case Study

Aside from the most notorious threats, the Mediterranean Sea faces novel and poorly explored impacts from artificial light at night (ALAN), which influences natural light–dark cycles and affects marine ecosystems. This study investigates the impact of ALAN on coastal infralittoral assemblages in Malta, where such effects remain unexplored. Using Baited Remote Underwater Videos (BRUVs), we examined the influence of different light intensities on species assemblages and behaviour at two sites: a light-polluted harbour and a darker reef area. Our findings reveal significant differences in fish community composition between light treatments and habitats. Among the 23,955 individuals recorded across multiple taxa, Boops boops accounted for 80% of observations. From our results, light intensity had a more substantial impact on community structure than habitat type, with species-specific responses to light. Predatory species such as Trachurus trachurus displayed increased activity under high-intensity white light, while Apogon imberbis and Serranus scriba were more abundant under red light, irrespective of habitat. These results underscore the role of ALAN in altering marine community dynamics and emphasise the need for sustainable management strategies to mitigate its impact on the biodiversity of the Mediterranean. This study provides initial empirical evidence of ALAN’s effects in Maltese waters, contributing to broader efforts to understand and manage light pollution in marine ecosystems.

Comparing Developer Attraction and Turnover in OSS vs. OSS4SG Projects: An MSR Study

Open source for social good (OSS4SG) projects are projects whose overarching goal focuses on solving a societal issue and driving positive change. Despite the societal importance of such projects and their alignment with the open-source ideology at its very core, there is a clear lack of understanding of the unique characteristics and operational dynamics of OSS4SG projects. In this work, we use Mining Software Repository (MSR) techniques to empirically investigate the community dynamics and project characteristics of OSS4SG projects compared to OSS projects. We leveraged the GitHub API and GraphQL to mine a dataset of 290 projects (199 OSS4SG, 91 OSS) and answer our main research questions: RQ1: How stable are OSS4SG compared to OSS in terms of newcomers and leavers? RQ2: To what extent do turnover and retention of contributors change over time for OSS vs OSS4SG? Namely, we studied and compared the rates at which contributors joined and left OSS and OSS4SG projects at different stages of life (early, mid, late). We classified projects as attractive (high join rate and low leave rate), unattractive (low join rate and high leave rate), stable (low join rate and low leave rate), and unstable (high join rate and high leave rate). Our results show that the majority of OSS4SG projects (60%) are stable, while the majority of OSS projects (74%) are unstable. Our results also show that OSS4SG retains more of their contributors and has less turnover. Looking at the join and leave rates for projects across different life stages, we found that the difference is significant when all stages of life and considered together. However, the difference is far less significant in the late stage of the project's lifespan, indicating that, as they mature, OSS becomes more similar to OSS4SG in terms of community dynamics.

The Evolving Context of MAID-Related Communications for Registered Nurses in Canada.

Since legalization of Medical Assistance in Dying in Canada in 2016, nurses are increasingly faced with new and evolving communication challenges as patients in a diversity of settings and contexts contemplate their end-of-life options. The purposes of this study were: 1) to develop an understanding of the nuances and challenges associated with MAID-related communication from the perspective of registered nurses, and 2) to draw on the insights arising from this analysis to reflect on the evolution of MAID communication for nurses over time. This study represented a secondary analysis of two primary qualitative data sets, including: 74 interviews of Canadian registered nurses self-identifying as having some exposure to MAID in their clinical practice; and 47 narrative reflections volunteered by respondents to questions posed in an online MAID reflective guide for nurses. Nurses described evolving complexities associated with introducing and engaging with the topic of MAID with their patients, helping patients navigate access to MAID assessment, managing family and community dynamics associated with opinions and beliefs surrounding MAID, supporting patients in their planning toward a MAID death, and being there for patients and their families in the moment of MAID. MAID communication is highly complex, individualized, and context-specific. It is apparent that many nurses have developed an impressive degree of comfort and skill around navigating its nuances within a rapidly evolving legislative context. It is also apparent that dedicated basic and continuing MAID communication education will warranted for registered nurses in all health care settings.

Arbuscular mycorrhizal fungi equalize differences in plant fitness and facilitate plant species coexistence through niche differentiation.

Mycorrhizal fungi are essential to the establishment of the vast majority of plant species but are often conceptualized with contradictory roles in plant community assembly. On the one hand, host-specific mycorrhizal fungi may allow a plant to be competitively dominant by enhancing growth. On the other hand, host-specific mycorrhizal fungi with different functional capabilities may increase nutrient niche partitioning, allowing plant species to coexist. Here, to resolve the balance of these two contradictory forces, we used a controlled greenhouse study to manipulate the presence of two main types of mycorrhizal fungus, ectomycorrhizal fungi and arbuscular mycorrhizal fungi, and used a range of conspecific and heterospecific competitor densities to investigate the role of mycorrhizal fungi in plant competition and coexistence. We find that the presence of arbuscular mycorrhizal fungi equalizes fitness differences between plants and stabilizes competition to create conditions for host species coexistence. Our results show how below-ground mutualisms can shift outcomes of plant competition and that a holistic view of plant communities that incorporates their mycorrhizal partners is important in predicting plant community dynamics.

Epidemiological Consequences of Individual Centrality on Wild Chimpanzees.

Disease outbreaks are one of the key threats to great apes and other wildlife. Because the spread of some pathogens (e.g., respiratory viruses, sexually transmitted diseases, ectoparasites) are mediated by social interactions, there is a growing interest in understanding how social networks predict the chain of pathogen transmission. In this study, we built a party network from wild chimpanzees (Pan troglodytes), and used agent-based modeling to test: (i) whether individual attributes (sex, age) predict individual centrality (i.e., whether it is more or less socially connected); (ii) whether individual centrality affects an individual's role in the chain of pathogen transmission; and, (iii) whether the basic reproduction number (R0) and infectious period modulate the influence of centrality on pathogen transmission. We show that sex and age predict individual centrality, with older males presenting many (degree centrality) and strong (strength centrality) relationships. As expected, males are more central than females within their network, and their centrality determines their probability of getting infected during simulated outbreaks. We then demonstrate that direct measures of social interaction (strength centrality), as well as eigenvector centrality, strongly predict disease dynamics in the chimpanzee community. Finally, we show that this predictive power depends on the pathogen's R0 and infectious period: individual centrality was most predictive in simulations with the most transmissible pathogens and long-lasting diseases. These findings highlight the importance of considering animal social networks when investigating disease outbreaks.

Using a Nested Sampling Design Across Spatial Scales to Gain Insights Into Distribution Patterns of Fishes, Mussels and Macroinvertebrates in a Riverine System

ABSTRACTAimThe goal of our study was to use a nested sampling design to compare the distribution of different groups of organisms with different dispersal modes and examine their responses in community composition to environmental heterogeneity at different spatial scales (local pool vs. riffle habitat, sections within a river and between rivers).LocationUpper Colorado River basin, Texas, USA.TaxonFishes, mussels and macroinvertebrates.MethodsWe sampled 100 sites using a nested sampling design across five rivers (four tributaries and the mainstem), with four river sections and five sampling sites per section, each consisting of a pool and riffle habitat. Collected data on species abundances, local and landscape environmental variables and spatial variables were analysed using a combination of dissimilarity, redundancy and variation partitioning analysis.ResultsAt the river scale, environmental heterogeneity explained 28% and 34% of the variation in mussel and fish communities, respectively, and 15% for macroinvertebrates. Community changes between sections in the tributaries were highest for fishes, but similarly high for fishes and macroinvertebrates in the mainstem. Significant patterns for mussels were only detected in rivers with higher abundances. No significant differences in dissimilarity were found between mesohabitats, but a small significant effect of mesohabitat was detected for mussels with RDA after removing the river effect.Main ConclusionsAlthough the depauperate mussel communities made it more difficult to draw any conclusions, there were some indications that their distribution was driven by environmental heterogeneity across scales. Section and river scales were relevant for fish, whereas macroinvertebrates showed a weaker response to environmental heterogeneity at these scales. The combination of approaches detected more ecologically meaningful patterns than one analysis alone would have. This study highlights the complexity of riverine community dynamics and underscores the need for a multiscale approach to identify their distribution patterns.

Identifying Patterns among Tourism-Oriented Online Communities on Facebook

The proliferation of social media has transformed how people engage in communication and community building, with platforms like Facebook becoming central to connecting individuals with shared interests. Despite the extensive formation of tourism-oriented online communities on these platforms, there is a notable lack of comprehensive studies examining their structural and managerial dynamics. This study addresses this gap by systematically analyzing fifty international tourism-focused Facebook communities to develop a novel typology based on the nature and type of information shared. The research identifies significant variations in community sizes, engagement levels, and management structures, highlighting that only 6% of these communities qualify as large, with membership exceeding one million. Contrary to common assumptions, a direct link between community size and engagement was not found, with qualitative factors like community purpose and content type being more influential. A notable correlation was observed between the number of administrators and moderators and the member count, emphasizing the importance of effective community governance. The study’s findings contribute to a deeper theoretical understanding of online community dynamics and offer practical implications for tourism marketers and community managers aiming to optimize engagement strategies on social media platforms. The research sets a foundation for future exploration of the interplay between virtual community management and tourism-related discourse.

Composition and temporal dynamics of the phytoplankton community in Laizhou Bay revealed by microscopic observation and rbcL gene sequencing

Laizhou Bay, a major breeding ground for economic marine organisms in the northern waters of China, is facing rapid environmental degradation. In this study, field surveys in this area were conducted in the spring, summer, and autumn of 2020. Microscopic observation and RuBisCO large subunit (rbcL) gene analysis were employed to understand the community structure and temporal dynamics of phytoplankton. The phytoplankton community structures detected by the two methods showed significant differences. Microscopic observation revealed the dominance of dinoflagellates in spring that shifted to the dominance of diatoms in summer and autumn. However, rbcL gene sequencing consistently identified diatoms as dominant throughout all three seasons, with their relative abundance showing an increasing trend. Conversely, the relative abundance of the second- and third-most abundant taxa, namely, haptophytes and ochrophytes, decreased as the seasons transitioned. rbcL gene sequencing annotated more species than microscopy. It could detect haptophytes and cryptophytes, which were overlooked by microscopy. In addition, rbcL gene sequencing detected a remarkable amount of Thalassiosira profunda, which was previously unidentified in this sea area. However, it appeared to underestimate the contribution of dinoflagellates considerably, with most taxa being only identified through microscopic identification. The two methods jointly identified 28 harmful algal bloom taxa with similar detection quantities but substantial differences in species composition. Phytoplankton communities were influenced by temperature, salinity, and nutrients. The results of this work suggest that a combination of multiple techniques is necessary for a comprehensive understanding of phytoplankton.

Windthrow Impact on Alpine Forest Humipedon: Soil Microarthropod Communities and Humus Dynamics Five Years after an Extreme Windstorm Event

The ecological impact of windthrow disturbance on humipedons and soil microarthropod communities is examined in two areas of the Italian Alps (Val di Fassa and Cansiglio) five years after the Vaia Storm. The following soil coverage conditions were identified: herbaceous vegetation (G), decaying wood (W), no vegetation (B) in windthrow areas; and these were compared with conditions in adjacent undisturbed intact forests (IF) and, only in Val di Fassa, with permanent meadows (M). Soil pH, soil organic matter content (SOM), humus systems and microarthropod communities were analyzed. In Val di Fassa, SOM loss was observed in windthrow areas vs. IF, moving toward a Mull humus system, while G evolved toward M-like conditions, W maintained a thicker O horizon and lower pH and B exhibited severe soil erosion and the lowest SOM. In Cansiglio, windthrow areas showed a slower transition to a Mull system, with a trend toward increasing pH and decreasing SOM. A clear relationship between microarthropod communities and humus systems could not be established because the consistency and biological origins of the humus diagnostic horizons were not considered. Microarthropod communities under different conditions exhibited significant dissimilarity, with varying responses across groups; Shannon and QBS-ar indices remained stable except for a significant decrease in B. Community dissimilarity thus appears to be enhanced by post-windthrow disturbance, suggesting that destructive windstorms may also present an opportunity for enriched microarthropod diversity.

Soil Microbial Properties of Durum Grown after Camelina, Carinata, Cover Crops, and Fallow

Novel crop rotation is an important factor influencing the composition of soil microorganisms. However, the effect of introducing oilseed and cover crops (CCs) into monoculture durum rotations on soil microbial communities is not clear in the Northern Great Plains. The objective of this study was to evaluate the effects of 2-year durum (Triticum durum D.) rotations with Ethiopian mustard (Brassica carinata A.) or camelina (Camelina sativa L.) or a 10-species forage/CC mix planted to replace fallow rotations with wheat on soil microorganisms. This study was designed as a randomized complete block with three replications in a no-tillage system. The results showed that total bacterial proportion was significantly higher in durum following fallow and camelina compared to durum following CC and carinata. Total fungal proportion was significantly higher in durum following CC compared to durum following oilseed crops and fallow. The fungal-to-bacterial ratio was significantly higher in durum following CC compared to durum following camelina and fallow. The crop species, soil pH and highly variable rainfall influenced the microbial community dynamics. The abundance of specific microbial groups due to crop-related changes might play a key role in the yield of subsequent crops and soil biological health. This study provides valuable insights into the use of CC mix and oilseeds as an alternative crop for fallow in a wheat–fallow system under dryland farming conditions. Future work is required to elucidate the biological mechanisms and functions of the soil microbial communities in the preceding and subsequent crop relative to soil health and crop productivity.

Exploring microbial diversity in the rhizosphere: a comprehensive review of metagenomic approaches and their applications.

The rhizosphere, the soil region influenced by plant roots, represents a dynamic microenvironment where intricate interactions between plants and microorganisms shape soil health, nutrient cycling, and plant growth. Soil microorganisms are integral players in the transformation of materials, the dynamics of energy flows, and the intricate cycles of biogeochemistry. Considerable research has been dedicated to investigating the abundance, diversity, and intricacies of interactions among different microbes, as well as the relationships between plants and microbes present in the rhizosphere. Metagenomics, a powerful suite of techniques, has emerged as a transformative tool for dissecting the genetic repertoire of complex microbial communities inhabiting the rhizosphere. The review systematically navigates through various metagenomic approaches, ranging from shotgun metagenomics, enabling unbiased analysis of entire microbial genomes, to targeted sequencing of the 16S rRNA gene for taxonomic profiling. Each approach's strengths and limitations are critically evaluated, providing researchers with a nuanced understanding of their applicability in different research contexts. A central focus of the review lies in the practical applications of rhizosphere metagenomics in various fields including agriculture. By decoding the genomic content of rhizospheric microbes, researchers gain insights into their functional roles in nutrient acquisition, disease suppression, and overall plant health. The review also addresses the broader implications of metagenomic studies in advancing our understanding of microbial diversity and community dynamics in the rhizosphere. It serves as a comprehensive guide for researchers, agronomists, and policymakers, offering a roadmap for harnessing metagenomic approaches to unlock the full potential of the rhizosphere microbiome in promoting sustainable agriculture.