Anthropogenic Environmental Change Research Articles

Herbarium specimens reveal a cryptic invasion of polyploid Centaurea stoebe in Europe.

Numerous plant species are expanding their native ranges due to anthropogenic environmental change. Because cytotypes of polyploid complexes often show similar morphologies, there may be unnoticed range expansions (i.e. cryptic invasions) of one cytotype into regions where only the other cytotype is native. We critically revised herbarium specimens of diploid and tetraploid Centaurea stoebe, collected across Europe between 1790 and 2023. Based on their distribution in natural and relict habitats and phylogeographic data, we estimated the native ranges of both cytotypes. Diploids are native across their entire European range, whereas tetraploids are native only to South-Eastern Europe and have recently expanded their range toward Central Europe. The proportion of tetraploids has exponentially increased over time in their expanded but not in their native range. This cryptic invasion predominantly occurred in ruderal habitats and enlarged the climatic niche of tetraploids toward a more oceanic climate. We conclude that spatio-temporally explicit assessments of range shifts, habitat preferences and niche evolution can improve our understanding of cryptic invasions. We also emphasize the value of herbarium specimens for accurate estimation of species´ native ranges, with fundamental implications for the design of research studies and the assessment of biodiversity trends.

Anthropogenic noise and light pollution decrease the repeatability of activity patterns and dampen expression of chronotypes in a free-living songbird

Anthropogenic environmental change is introducing a suite of novel disturbance factors, which can have wide-ranging effects on mean behavior and behavioral repeatability. For example, exposure to sensory pollutants, such as anthropogenic noise and artificial light at night (ALAN), may affect consistent and repeatable individual-level timing of daily activity, which is referred to as chronotypes. Although chronotypes have been increasingly documented in wild animal populations and may affect fitness, evidence for long-term stability across life-history stages and seasons is notably lacking. Furthermore, how multiple anthropogenic stressors may interact to erode or magnify the expression of chronotypes remains unclear. We tested for existence of chronotypes across life-history stages and seasons in suburban female great tits (Parus major), using emergence time from nest boxes in the morning as a proxy for activity onset. We then examined joint effects of noise pollution and ALAN on expression of chronotypes, and tested for effects of noise, ALAN, and weather conditions on mean emergence time. We found repeatability of daily activity patterns (emergence times) across life-history stages and seasons, providing evidence of chronotypes, as well as interactive effects of anthropogenic disturbance factors and weather conditions on population mean behavior. Furthermore, across-season repeatability of emergence times was approximately double in magnitude in low light and low noise conditions, relative to in conditions with higher light and/or noise pollution. Thus, joint exposure to these sensory pollutants tends to erode expression of chronotypes. This effect was driven by higher among-individual variance in the relatively undisturbed environment and collapse of this variance in the more disturbed environments. Decreased repeatability in environments with high disturbance levels may reduce potential for behavioral traits, such as chronotype, to be the target of selection and limit adaptability.

Epigenetic responses of trees to environmental stress in the context of climate change.

In long-lived tree populations, when environmental change outpaces rates of evolutionary adaptation, plasticity in traits related to stress tolerance, dormancy, and dispersal may be vital for preventing extinction. While a population's genetic background partly determines its ability to adapt to a changing environment, so too do the many types of epigenetic modifications that occur within and among populations, which vary on timescales orders of magnitude faster than the emergence of new beneficial alleles. Consequently, phenotypic plasticity driven by epigenetic modification may be especially critical for sessile, long-lived organisms such as trees that must rely on this plasticity to keep pace with rapid anthropogenic environmental change. While studies have reported large effects of DNA methylation, histone modification, and non-coding RNAs on the expression of stress-tolerance genes and resulting phenotypic responses, little is known about the role of these effects in non-model plants and particularly in trees. Here, we review new findings in plant epigenetics with particular relevance to the ability of trees to adapt to or escape stressors associated with rapid climate change. Such findings include specific epigenetic influences over drought, heat, and salinity tolerance, as well as dormancy and dispersal traits. We also highlight promising findings concerning transgenerational inheritance of an epigenetic 'stress memory' in plants. As epigenetic information is becoming increasingly easy to obtain, we close by outlining ways in which ecologists can use epigenetic information better to inform population management and forecasting efforts. Understanding the molecular mechanisms behind phenotypic plasticity and stress memory in tree species offers a promising path towards a mechanistic understanding of trees' responses to climate change.

Cost-efficient PCR based DNA barcoding of marine invertebrate specimens with NovaSeq amplicon sequencing.

The marine environment harbors high biodiversity; however, it is poorly understood. Nucleotide sequence data of all marine organisms should be accumulated before natural and/or anthropogenic environmental changes jeopardize the marine environment. In this study, we report a cost-effective and easy DNA barcoding method. This method can be readily adopted without using library preparation kits. It includes multiplex PCR of short targets, indexing PCR, and outsourcing to a sequencing service using the NovaSeq system. We targeted four mitochondrial genes [cytochrome c oxidase subunit I (COI), COIII, 16S rRNA (16S), and 12S rRNA (12S)] and three nuclear genes [18S rRNA (18S), 28S rRNA (28S), internal transcribed spacer 2 (ITS2)] in 95 marine invertebrate specimens, which were primarily annelids. The primers, including adapters and indices for NovaSeq sequencing, were newly designed. Two PCR runs were conducted. The 1st PCR amplified specific loci with universal primers and the 2nd added sequencing adapters and indices to the 1st PCR products. The gene sequences obtained from the FASTQ files were subjected to BLAST search and phylogenetic analyses. One run using 95 specimens yielded sequences averaging 2816bp per specimen for a total length of six loci. Nuclear genes were more successfully assembled compared with mitochondrial genes. A weak but significantly negative correlation was observed between the average length of each locus and success rate of the assembly. Some of the sequences were almost identical to the sequences obtained from specimens collected far from Japan, indicating the presence of potentially invasive species identified for the first time. We obtained gene sequences efficiently using next-generation sequencing rather than Sanger sequencing. Although this method requires further optimization to increase the success rate for some loci, it is used as a first step to select specimens for further analyses by determining the specific loci of the targets.

The Effects of Oxidative Stress on RNA Editing with Insight into the Relationship Between Air Pollution and Alzheimer's Disease

Human interactions with the environment today add pressure on the world’s resources and ecosystems, which in turn harm human health. Many anthropogenic environmental changes, including climate change, biodiversity loss, and pollution, have accelerated morbidity and mortality. Research across multiple countries have found correlations between anthropogenic air pollution exposure and neurological degeneration, particularly with Alzheimer’s disease (AD). RNA editing induced by oxidative stress is one possible mechanism in which air pollution increases the risk of AD. To study this further, RNA adenosine-to-inosine (A-to-I) alterations were analyzed to identify a mechanism linking air pollution to neurological degeneration. These alterations occur in RNA, most prevalently in the central nervous system (CNS). Adenosine deaminase acting on RNA (ADAR) enzymes mediate A-to-I alterations and are essential for mammalian development and survival. ADAR mediated alterations have been associated with AD and the A-to-I occurrence frequency may increase in polluted environments that trigger increased oxidative stress. To test this possibility, wildtype (WT) and ADAR knockout (adr-2(-) Caenorhabditis elegans in their first larval (L1) developmental stage were exposed to juglone solution for 0, 15, and 60 minute experimental settings. For the two worm strains, WT and adr-2(-), the 0 minute treatment was the control, the 15 minute treatment represented acute oxidative stress exposure, and the 60 minute treatment represented chronic exposure. RNA was extracted from both groups and quantitative Real Time PCR (qRT-PCR) was used to measure the expression of gst-4, an Alzheimer’s associated gene (sel-12), and adr-2 normalized to the expression of gpd-3, the housekeeping gene that corrected for systemic errors. The gst-4 gene expression confirmed that oxidative stress occurred. Lack of adr-2 gene significantly decreased sel-12 expression at acute exposure, but adr-2 gene expression in WT worms did not significantly change across treatments. It remains to be determined whether oxidative stress impacts RNA editing of target mRNAs. Future studies are needed to explore the role of adr-2 in promoting sel-12 expression.

Widespread cultural change in declining populations of Amazon parrots.

Species worldwide are experiencing anthropogenic environmental change, and the long-term impacts on animal cultural traditions such as vocal dialects are often unknown. Our prior studies of the yellow-naped amazon (Amazona auropalliata) revealed stable vocal dialects over an 11-year period (1994-2005), with modest shifts in geographic boundaries and acoustic structure of contact calls. Here, we examined whether yellow-naped amazons maintained stable dialects over the subsequent 11-year time span from 2005 to 2016, culminating in 22 years of study. Over this same period, this species suffered a dramatic decrease in population size that prompted two successive uplists in IUCN status, from vulnerable to critically endangered. In this most recent 11-year time span, we found evidence of geographic shifts in call types, manifesting in more bilingual sites and introgression across the formerly distinct North-South acoustic boundary. We also found greater evidence of acoustic drift, in the form of new emerging call types and greater acoustic variation overall. These results suggest cultural traditions such as dialects may change in response to demographic and environmental conditions, with broad implications for threatened species.

Insights Into the Evolution, Virulence and Speciation of Babesia MO1 and Babesia divergens Through Multiomics Analyses

Babesiosis, caused by protozoan parasites of the genus Babesia, is an emerging tick-borne disease of significance for both human and animal health. Babesia parasites infect erythrocytes of vertebrate hosts where they develop and multiply rapidly to cause the pathological symptoms associated with the disease. The identification of new Babesia species underscores the ongoing risk of zoonotic pathogens capable of infecting humans, a concern amplified by anthropogenic activities and environmental changes. One such pathogen, Babesia MO1, previously implicated in severe cases of human babesiosis in the United States, was initially considered a subspecies of B. divergens, the predominant agent of human babesiosis in Europe. Here we report comparative multiomics analyses of B. divergens and B. MO1 that offer insight into their biology and evolution. Our analysis shows that despite their highly similar genomic sequences, substantial genetic and genomic divergence occurred throughout their evolution resulting in major differences in gene functions, expression and regulation, replication rates and susceptibility to antiparasitic drugs. Furthermore, both pathogens have evolved distinct classes of multigene families, crucial for their pathogenicity and adaptation to specific mammalian hosts. Leveraging genomic information for B. MO1, B. divergens, and other members of the Babesiidae family within Apicomplexa provides valuable insights into the evolution, diversity, and virulence of these parasites. This knowledge serves as a critical tool in preemptively addressing the emergence and rapid transmission of more virulent strains.

Pushing the boundaries: actual and potential distribution of thrushes expanding their ranges in South America

The distribution of a species reflects its ecological adaptability and evolutionary history, which is shaped by the environment and represents a dynamic area subject to anthropogenic environmental change. We used the MaxEnt algorithm to construct ecological niche models for four thrush species within the Turdus genus; T. amaurochalinus, T. chiguanco, T. falcklandii and T. rufiventris. These models were used to predict the potential geographic distributions of these species that are expanding their ranges in South America. Using occurrence records, we estimated currently occupied areas for each species. We also identified suitable habitats and projected possible areas to be colonized by the four species at continental scale. Temperature annual range had the highest influence for T. falcklandii, while human modification was the main variable explaining the distribution of the other three species. The potential distribution area ranged from 2.5 million km2 for T. falcklandii to nearly seven million km2 for T. amaurochalinus. Large proportions of suitable area remain unoccupied by all four species, being 50% for T. amaurochalinus and T. rufiventris, and about 70% for T. chiguanco and T. falcklandii. Anthropogenic disturbances, such as habitat loss and ecosystem transformation, lead to non-random species extinction and biotic homogenization, highlighting the importance of predictive models as valuable tools for informing mitigation policies and conservation strategies. Thrushes are progressively expanding their ranges, and the colonization of new habitats could bring new challenges.

52,000 years of woolly rhinoceros population dynamics reveal extinction mechanisms

The extinction of the woolly rhinoceros (Coelodonta antiquitatis) at the onset of the Holocene remains an enigma, with conflicting evidence regarding its cause and spatiotemporal dynamics. This partly reflects challenges in determining demographic responses of late Quaternary megafauna to climatic and anthropogenic causal drivers with available genetic and paleontological techniques. Here, we show that elucidating mechanisms of ancient extinctions can benefit from a detailed understanding of fine-scale metapopulation dynamics, operating over many millennia. Using an abundant fossil record, ancient DNA, and high-resolution simulation models, we untangle the ecological mechanisms and causal drivers that are likely to have been integral in the decline and later extinction of the woolly rhinoceros. Our 52,000-y reconstruction of distribution-wide metapopulation dynamics supports a pathway to extinction that began long before the Holocene, when the combination of cooling temperatures and low but sustained hunting by humans trapped woolly rhinoceroses in suboptimal habitats along the southern edge of their range. Modeling indicates that this ecological trap intensified after the end of the last ice age, preventing colonization of newly formed suitable habitats, weakening stabilizing metapopulation processes, triggering the extinction of the woolly rhinoceros in the early Holocene. Our findings suggest that fragmentation and resultant metapopulation dynamics should be explicitly considered in explanations of late Quaternary megafauna extinctions, sending a clarion call to the fragility of the remaining large-bodied grazers restricted to disjunct fragments of poor-quality habitat due to anthropogenic environmental change.

Genomic prediction of resistance to Hymenoscyphus fraxineus in common ash (Fraxinus excelsior L.) populations.

The increase in introduced insect pests and pathogens due to anthropogenic environmental changes has become a major concern for tree species worldwide. Common ash (Fraxinus excelsior L.) is one of such species facing a significant threat from the invasive fungal pathogen Hymenoscyphus fraxineus. Some studies have indicated that the susceptibility of ash to the pathogen is genetically determined, providing some hope for accelerated breeding programs that are aimed at increasing the resistance of ash populations. To address this challenge, we used a genomic selection strategy to identify potential genetic markers that are associated with resistance to the pathogen causing ash dieback. Through genome-wide association studies (GWAS) of 300 common ash individuals from 30 populations across Poland (ddRAD, dataset A), we identified six significant SNP loci with a p-value ≤1 × 10-4 associated with health status. To further evaluate the effectiveness of GWAS markers in predicting health status, we considered two genomic prediction scenarios. Firstly, we conducted cross-validation on dataset A. Secondly, we trained markers on dataset A and tested them on dataset B, which involved whole-genome sequencing of 20 individuals from two populations. Genomic prediction analysis revealed that the top SNPs identified via GWAS exhibited notably higher prediction accuracies compared to randomly selected SNPs, particularly with a larger number of SNPs. Cross-validation analyses using dataset A showcased high genomic prediction accuracy, predicting tree health status with over 90% accuracy across the top SNP sets ranging from 500 to 10,000 SNPs from the GWAS datasets. However, no significant results emerged for health status when the model trained on dataset A was tested on dataset B. Our findings illuminate potential genetic markers associated with resistance to ash dieback, offering support for future breeding programs in Poland aimed at combating ash dieback and bolstering conservation efforts for this invaluable tree species.

Seasonal species composition, abundance and public health importance of mosquito vectors (Diptera: Culicidae) in Huai Tha Khoei Reservoir, Ratchaburi, Thailand

Abstract. Chaiphongpachara T, Laojuna S. 2024. Seasonal species composition, abundance and public health importance of mosquito vectors (Diptera: Culicidae) in Huai Tha Khoei Reservoir, Ratchaburi, Thailand. Biodiversitas 25: 1264-1275. Mosquitoes are vectors for pathogens that cause life-threatening diseases in humans and animals. Significant mosquito-borne diseases include malaria, dengue, chikungunya, Zika, Japanese encephalitis, and filariasis. Anthropogenic environmental changes can significantly impact the dynamics of disease vector populations, which can lead to outbreaks of mosquito-borne diseases. This study investigated the seasonal variation in species composition and abundance of mosquito vectors around the Huai Tha Khoei Reservoir in Ratchaburi Province, Thailand, across cool, hot, and rainy seasons. A total of 1363 mosquitoes, representing 30 species from five genera, were collected. In particular, 25 of these species, accounting for 83.33% of the total, were identified as vectors of human pathogens. The most dominant species across all seasons was Culex tritaeniorhynchus Giles 1901, representing 39.47% (n=538) of the total, followed by Anopheles barbirostris Wulp 1884 s.l. (14.38%, n = 196) and Culex vishnui Theobald 1901 (9.02%, n=123). The Shannon diversity index was highest during the rainy season (H’= 2.144) and lowest in the hot season (H’=1.788). This is consistent with the results of the UPGMA tree based on beta diversity, indicating that mosquito diversity in the rainy season differs significantly from that in the cool and hot seasons. The findings enhance our understanding of the impact of seasonality on mosquito vectors in this region, which is crucial for developing effective disease control strategies. Additionally, this study serves as a valuable reference for understanding the diversity of mosquito vectors in other areas.

Impact of rapid anthropogenic environmental change on water security in a tropical Andean basin

Rapid anthropogenic environmental change significantly impacts water security (WS) in the Andean highlands, limiting water availability and use. Amidst swift human-induced environmental transformations, discernible trends emerge in increased water demand and heightened ecosystem service valuation. This study examines water usage conflicts in an Andean basin and operationalizes WS using historical analysis for future applications. We focused on WS changes in the Upper Chicamocha River Basin (UCRB), encompassing rural and urban areas. An integrated water security (IWS) framework, with a composite indicator and eight dimensions, is employed to analyze the implications of observed changes over 40 years (1981–2020). Results show a “fair” IWS score 85 % of the time, with 15 % classified as “good”. Evaluation of demand coverage for water usage reveals users benefiting from sufficient water provision (mining, thermoelectric, services, environment, aquaculture, and agriculture), while the industrial and domestic sectors suffer from frequent shortages. Findings emphasize the need for trade-offs in addressing diverse water security outcomes for all users in a changing climate.

The coral microbiome in sickness, in health and in a changing world.

Stony corals, the engines and engineers of reef ecosystems, face unprecedented threats from anthropogenic environmental change. Corals are holobionts that comprise the cnidarian animal host and a diverse community of bacteria, archaea, viruses and eukaryotic microorganisms. Recent research shows that the bacterial microbiome has a pivotal role in coral biology. A healthy bacterial assemblage contributes to nutrient cycling and stress resilience, but pollution, overfishing and climate change can break down these symbiotic relationships, which results in disease, bleaching and, ultimately, coral death. Although progress has been made in characterizing the spatial-temporal diversity of bacteria, we are only beginning to appreciate their functional contribution. In this Review, we summarize the ecological and metabolic interactions between bacteria and other holobiont members, highlight the biotic and abiotic factors influencing the structure of bacterial communities and discuss the impact of climate change on these communities and their coral hosts. We emphasize how microbiome-based interventions can help to decipher key mechanisms underpinning coral health and promote reef resilience. Finally, we explore how recent technological developments may be harnessed to address some of the most pressing challenges in coral microbiology, providing a road map for future research in this field.

Mapping and assessing supply–demand matching of recreational ecosystem services in Shandong province, China

Globally, natural landscapes and their recreational ecosystem services (RES) are both under threat from anthropogenic activities and environmental changes. But the demand for RES increases with the development of human living standards. Therefore, mapping and assessing the supply–demand relationships of RES is crucial for landscape planning, management, and human well-being. This study aimed to study the relationships between supply and demand of RES in Shandong province, China, quantify the supply, demand, and supporting capacity of RES, analyze the degree of matching and coupling between the supply and demand of RES, and explore the effect of terrain gradient to RES. The results indicated that the average value of coupling coordination (CCD) between supply–demand of RES in Shandong province was 0.45, which is a mild balance. According to the supply–demand matching types, areas with low supply-high demand accounted for 6.62%, indicating a serious shortage matching of supply and demand. Using hotel quantity and roads as indicators of the supporting capacity of RES, the overall coordination between landscape aesthetic quality (LAQ) and regional hotel quantity shows a mild imbalance (0.38), while that with the regional road density shows a good balance (0.60). Furthermore, the scenery spots density, RES supply, RES supply–demand CCD and support capacity CCD shows an upward trend with the increase of elevation and slope, an “increased-decreased-increased” trend with the increase of terrain niche index. This study provides spatial matching of RES supply and demand in Shandong province. Optimizing land-use structures and improving natural resource allocation were proposed to boost coordination of RES supply and demand.

Effects of Reduced Seawater pH and Oil Contamination on Bacterial Communities and Biochemical Markers of Estuarine Animal Hosts

Ecosystem functioning depends on complex interactions between microorganisms, hosts, and the environment. Changes in environmental conditions (e.g., ocean acidification) in combination with anthropogenic pollution have been shown to affect the composition and function of free-living microbial communities, but little is known about the effects these stressors on host-associated communities. This study aims to characterize the response of host-associated bacterial communities of the bottom-dwelling polychaete Hediste diversicolor and the epibenthic gastropod Peringia ulvae to oil contamination and reduced seawater pH. The independent and interactive effects of both stressors were simulated under controlled conditions. The response of host-associated bacterial communities was assessed using the high-throughput sequencing of the 16S rRNA gene and several biochemical markers related to host metabolic pathways, e.g., neurotransmission, anaerobic metabolism, biotransformation, oxidative stress, and energy consumption. In H. diversicolor, reduced seawater pH was associated with a high relative abundance of Cyanobacteria, while in P. ulvae oil contamination was associated with a reduction in the relative abundance of Chitinophagales. In P. ulvae, enrichment with oil hydrocarbon-degrading bacteria suggests a possible role of these organisms in the dispersion of oil hydrocarbon degraders. Furthermore, oil supplementation shifted some specific biochemical markers of gastropods related to oxidative stress and energy consumption, which suggests host stress. In general, the bacterial communities and biochemical markers of the gastropod were more affected by stressors than those of the polychaete. Overall, this study contributes to a better understanding of the response of host-associated bacterial communities of benthic macrofauna to anthropogenic contamination and environmental change.

Rushing for "burned" food: Why and how does a group of patas monkeys (Erythrocebus patas) reach freshly burned areas?

Recently, considerable attention has been paid to animal adaptations to anthropogenic environments, such as foraging in burned areas where plants are promoted to regenerate by anthropogenic burning. However, among primates, reports on the utilization of resources that are available immediately after burning have been limited to a few primate species. In this study, we investigated and compared the activity budgets and food categories of a group of patas monkeys (Erythrocebus patas) in freshly burned areas by comparing them with those in previously burned areas and unburned areas. We also assessed the proportion of time spent in the freshly burned area before and after the fire: GPS collars were fitted to five of the six adults in the group, and their patterns when they traveled toward freshly burned and unburned feeding areas were compared. Patas monkeys spent more time in freshly burned areas after the fire, and they visited such areas mostly for feeding, particularly on roasted seeds of Cissus populnea. Furthermore, patas monkeys traveled faster and in a more synchronized way toward freshly burned areas. This "apparent goal-directed" travel began at least 1h before arriving. Results indicate that the group recognized freshly burned areas as valuable, and the monkeys were able to travel in a goal-directed manner to them despite their variable locations. We suggest that smoke from freshly burned areas provides a visual cue with which to orient to the burned areas. Our results also support the notion that some primates are flexible enough to adapt to and benefit from anthropogenic environmental changes.

Impacts of anthropogenic eutrophication on the carbon transfers in lacustrine food webs: A paleolimnological assessment in four mountain lakes

Over the last decades, the intensification of anthropogenic activities and associated disturbances on lake watersheds have led to major changes in lakes trophic functioning through accelerated eutrophication. In many lakes, these changes are characterized by an unprecedented increase in organic carbon fluxes, potentially leading to a shift in biogeochemical cycles and in the balance between carbon sequestration and greenhouse gas emissions. Understanding the response of the carbon cycle to natural and anthropogenic environmental changes is becoming a crucial challenge in the context of increasing global pressures. In this study, we reconstructed the changes in the trophic functioning of the benthic and pelagic food web, in response to accelerated eutrophication in four lakes over the last millenium. Changes in carbon pathways in food webs were assessed using stable carbon isotope analysis of chitinous subfossil remains of Daphnia, Bosmina, and Chironomini archived in sedimentary records. Changes in the trophic state were inferred from sedimentary geochemical analysis, including carbon accumulation rates, Chl a accumulation rates and carbon-to-nitrogen ratios. Agro-pastoral activities were tracked by analysis of coprophilous ascospores. Results provided by this multi-proxy approach highlight recent disruptions in carbon sources and transfer pathways in lakes food webs. In particular, changes in the carbon isotopic signature of pelagic consumers suggest a recent increase in the use of 13C-depleted carbon sources such as methanogenic or respiration-derived carbon linked to recent changes in trophic state under the intensification of anthropogenic pressures.

Temperature and nutrients alter the relative importance of stochastic and deterministic processes in the coastal macroinvertebrates biodiversity assembly on long-time scales.

Macroinvertebrates play a vital role in coastal ecosystems and are an important indicator of ecosystem quality. Both anthropogenic activity and environmental changes may lead to significant changes in the marine macroinvertebrate community. However, the assembly process of benthic biodiversity and its mechanism driven by environmental factors at large scales remains unclear. Here, using the benthic field survey data of 15 years at large spatial and temporal scales from the Yellow Sea Large Marine Ecosystem, we investigated the relative importance of environmental selection, dispersal processes, random-deterministic processes of macroinvertebrates community diversity assembly, and the responses of this relative importance driven by temperature and nutrients. Results showed that the macroinvertebrates community diversity is mainly affected by dispersal. Nitrogen and phosphorus are the most important negative factors among environmental variables, while geographical distance is the main limiting factor of β diversity. Within the range of 0.35-0.70 mg/L of nutrients, increasing nutrient concentration can significantly facilitate the contribution of the decay effect to β diversity. Within the temperature range studied (15.0-18.0°C), both warming and cooling can lead to a greater tendency for species diversity assembly processes to be dominated by deterministic processes. The analysis contributes to a better understanding of the assembly process of the diversity of coastal marine macroinvertebrates communities and how they adapt to global biogeochemical processes.

Sea-ice melt determines seasonal phytoplankton dynamics and delimits the habitat of temperate Atlantic taxa as the Arctic Ocean atlantifies.

The Arctic Ocean is one of the regions where anthropogenic environmental change is progressing most rapidly and drastically. The impact of rising temperatures and decreasing sea ice on Arctic marine microbial communities is yet not well understood. Microbes form the basis of food webs in the Arctic Ocean, providing energy for larger organisms. Previous studies have shown that Atlantic taxa associated with low light are robust to more polar conditions. We compared to which extent sea ice melt influences light-associated phytoplankton dynamics and biodiversity over two years at two mooring locations in the Fram Strait. One mooring is deployed in pure Atlantic water, and the second in the intermittently ice-covered Marginal Ice Zone. Time-series analysis of amplicon sequence variants abundance over a 2-year period, allowed us to identify communities of co-occurring taxa that exhibit similar patterns throughout the annual cycle. We then examined how alterations in environmental conditions affect the prevalence of species. During high abundance periods of diatoms, polar phytoplankton populations dominated, while temperate taxa were weakly represented. Furthermore, we found that polar pelagic and ice-associated taxa, such as Fragilariopsis cylindrus and Melosira arctica, were more common in Atlantic conditions, while temperate taxa, such as Odontella aurita and Proboscia alata, were less abundant under polar conditions. This suggests that sea ice melt may act as a barrier to the northward expansion of temperate phytoplankton, preventing their dominance in regions still strongly influenced by polar conditions. Our findings highlight the complex interactions between sea ice melt, phytoplankton dynamics, and biodiversity in the Arctic.

Nitrogen deposition mediates more stochastic processes in structuring plant community than soil microbial community in the Eurasian steppe.

Anthropogenic environmental changes may affect community assembly through mediating both deterministic (e.g., competitive exclusion and environmental filtering) and stochastic processes (e.g., birth/death and dispersal/colonization). It is traditionally thought that environmental changes have a larger mediation effect on stochastic processes in structuring soil microbial community than aboveground plant community; however, this hypothesis remains largely untested. Here we report an unexpected pattern that nitrogen (N) deposition has a larger mediation effect on stochastic processes in structuring plant community than soil microbial community (those <2 mm in diameter, including archaea, bacteria, fungi, and protists) in the Eurasian steppe. We performed a ten-year nitrogen deposition experiment in a semiarid grassland ecosystem in Inner Mongolia, manipulating nine rates (0-50 g N m-2 per year) at two frequencies (nitrogen added twice or 12 times per year) under two grassland management strategies (fencing or mowing). We separated the compositional variation of plant and soil microbial communities caused by each treatment into the deterministic and stochastic components with a recently-developed method. As nitrogen addition rate increased, the relative importance of stochastic component of plant community first increased and then decreased, while that of soil microbial community first decreased and then increased. On the whole, the relative importance of stochastic component was significantly larger in plant community (0.552±0.035; mean±standard error) than in microbial community (0.427±0.035). Consistently, the proportion of compositional variation explained by the deterministic soil and community indices was smaller for plant community (0.172-0.186) than microbial community (0.240-0.767). Meanwhile, as nitrogen addition rate increased, the linkage between plant and microbial community composition first became weaker and then became stronger. The larger stochasticity in plant community relative to microbial community assembly suggested that more stochastic strategies (e.g., seeds addition) should be adopted to maintain above- than below-ground biodiversity under the pressure of nitrogen deposition.