SER: An R package to characterize environmental regimes

Environmental regimes (or environmental legacy or historical legacy) are the dynamics of environmental characteristics over a given (either long or short) time period, such as frequency of mean or extreme events and rate of change, which might be absent by using only contemporary variables. We present SER, an R package for estimating environmental regimes for different environmental variables. Using the data included in the package, several examples are shown. SER is suitable for any type of environmental or biotic variables, including nutrient concentration, light, and dissolved oxygen. In addition, by changing the argument "days_bf," it is possible to compute environmental regimes over any time period, such as days, months, or years. Our case study showed that the inclusion of environmental regimes increased the explained variation of temporal β-diversity and its components. Environmental regimes are expected to advance the "environment-community" relationships in ecological studies. They can further be implemented in other subjects such as social science, socioeconomics, and epidemiology.

Dissolved Oxygen and Water Temperature Drive Vertical Spatiotemporal Variation of Phytoplankton Community: Evidence from the Largest Diversion Water Source Area

In order to study the vertical distribution characteristics of phytoplankton in the Danjiangkou Reservoir, the water source of the Middle Route Project of the South-North Water Diversion, seven sampling sites were set up in the Reservoir for quarterly sampling from 2017 to 2019, and water environment surveys were conducted simultaneously. The results showed that 157 species (including varieties) were identified, belonging to 9 phyla and 88 genera. In terms of species richness, Chlorophyta had the largest number of species, accounting for 39.49% of the total species. The Bacillariophyta and Cyanobacteria accounted for 28.03% and 13.38% of the total species, respectively. From the whole Danjiangkou Reservoir, the total phytoplankton abundance varied from 0.09 × 10² to 20.01 × 10⁶ cells/L. In the vertical distribution, phytoplankton were mainly observed in the surface-thermospheric layer (I-II layer) and the bottom layer, while the Shannon-Wiener index showed a trend of gradually decreasing from the I-V layer. The Surfer model analysis showed that there was no significant stratification in the Q site's water temperature (WT) and dissolved oxygen (DO) levels in the water diversion area during the dynamic water diversion process. A canonical correspondence analysis (CCA) showed that DO, WT, pH, electrical conductivity (Cond), chemical oxygen demand (COD_Mn), total phosphorus (TP), ammonia nitrogen (NH₄⁺-N), and total nitrogen (TN) had significant effects on the vertical distribution of phytoplankton (p < 0.05). A partial Mantel analysis showed that the vertical distribution of the phytoplankton community was related to WT, and the phytoplankton community structure at the other sites, except for Heijizui (H) and Langhekou (L), was affected by DO. This study has positive significance for exploring the vertical distribution characteristics of a phytoplankton community in a deep-water dynamic water diversion reservoir.

CircOMA1 modulates cabergoline resistance by downregulating ferroptosis in prolactinoma

PURPOSE

Prolactinomas are one of the most common pituitary neuroendocrine tumors (PitNETs), accounting for approximately 50% of all pituitary tumors. Dopamine agonists are the main treatment for prolactinoma, but a small number of patients are still resistant to pharmacotherapy. Recent discoveries have revealed that ferroptosis is involved in regulating tumor drug resistance. However, the role of ferroptosis in prolactinoma has not been reported. In this study, we aimed to explore the mechanism of a circRNA in ferroptosis in prolactinoma.

METHODS

The expression of circOMA1 in prolactinoma tissues was examined by quantitative reverse transcription PCR (qRT-PCR). The biological function of circOMA1 was evaluated in vitro and in vivo. To explore the role of ferroptosis in prolactinoma, we used qRT-PCR and western blotting. Glutamate-cysteine ligase, modifier subunit (GCLM) was predicted to be a direct target gene of miR-145-5p by bioinformatics analysis, which was confirmed by luciferase reporter assays.

RESULTS

circOMA1 was overexpressed in drug-resistant prolactinoma tissues compared with sensitive prolactinoma samples. We further found that circOMA1 promoted MMQ cells growth in vivo and in vitro. In addition, GCLM was directly targeted by miR-145-5p and indirectly regulated by circOMA1. Importantly, circOMA1 induced ferroptosis resistance through the increased expression of Nrf2, GPX4, and xCT, and circOMA1 attenuated CAB-induced ferroptosis in MMQ cells in vivo and in vitro.

CONCLUSION

The present study demonstrates that circOMA1 attenuates CAB efficacy through ferroptosis resistance and may be a new therapeutic target for the individualized treatment of DA-resistant prolactinoma patients.

[Clinical and chest CT features of immune checkpoint inhibitor-related pneumonitis]

Objective: To explore the clinical and chest computed tomography (CT) features and the outcome of immune checkpoint inhibitor-related pneumonitis (CIP). Methods: Clinical and chest CT data of 38 CIP patients with malignant tumors from the Cancer Hospital, Chinese Academy of Medical Sciences between August 2017 and April 2021 were retrospectively reviewed, and the outcomes of pneumonitis were followed up. Results: The median time from the administration of immune checkpoint inhibitors (ICIs) to the onset of CIP was 72.5 days in 38 patients with CIP, and 22 patients developed CIP within 3 months after the administration of ICIs. The median occurrence time of CIP in 24 lung cancer patients was 54.5 days, earlier than 119.0 days of non-lung cancer patients (P=0.138), with no significant statistical difference. 34 patients (89.5%) were accompanied by symptoms when CIP occurred. The common clinical symptoms were cough (29 cases) and dyspnea (27 cases). The distribution of CIP on chest CT was asymmetric in 31 cases and symmetrical in 7 cases. Among the 24 lung cancer patients, inflammation was mainly distributed ipsilateral to the primary lung cancer site in 16 cases and diffusely distributed throughout the lung in 8 cases. Ground glass opacities (37 cases) and consolidation (30 cases) were the common imaging manifestations, and organizing pneumonia (OP) pattern (15 cases) was the most common pattern. In 30 CIP patients who were followed up for longer than one month, 17 cases had complete absorption (complete absorption group), and 13 cases had partial absorption or kept stable (incomplete absorption group). The median occurrence time of CIP in the complete absorption group was 55 days, shorter than 128 days of the incomplete absorption group (P=0.022). Compared with the incomplete absorption group, there were less consolidation(P=0.010) and CIP were all classified as hypersensitivity pneumonitis (HP) pattern (P=0.004) in the complete absorption group. Conclusions: CIP often occurs within 3 months after ICIs treatment, and the clinical and CT findings are lack of specificity. Radiologic features may have a profound value in predicting the outcome of CIP.

Lake morphological characteristics and climatic factors affect long-term trends of phytoplankton community in the Rotorua Te Arawa lakes, New Zealand during 23 years observation

Monitoring the long-term dynamics of lake phytoplankton can help understand their natural temporal variability, as well as assess potential impacts of interventions aimed at improving lake ecological condition. However, investigating long-term changes in lake ecosystems has received scant attention. In the present study, we analyzed a long-term dataset of phytoplankton communities collected from 1990 to 2013 from eleven of the 12 Rotorua Te Arawa lakes in New Zealand, to explore their responses to changing abiotic conditions. We used a sequential algorithm to examine the likelihood of regime shifts in abiotic and biotic factors during the study period that could be attributable to lake interventions. Our analysis suggests that lake interventions have improved the abiotic factors, whereas the response of biotic factors was less clear. Total phosphorus levels were implicated in the decline in lake condition, including in two lakes subject to lake interventions, and in four control lakes. Both abiotic and biotic factors showed diverse trends (e.g., increase, decrease or no change), and abiotic factors had more regime shifts than biotic factors. Shifts in biotic indices also displayed time lags to shifts in abiotic factors. Long-term responses of abiotic and biotic factors were also influenced by lake morphological characteristics and climatic variables. This latter finding underscores the importance of considering lake morphological characteristics and climate changes when planning management practices. A sound understanding of resilience and threshold of phytoplankton shifts to environmental changes are needed to assess the effectiveness of previous management strategies and prioritize the future conservation efforts toward water quality goals.

How do multidimensional traits of dominant diatom Aulacoseira respond to abiotic and biotic factors in a river delta system?

Trait-based approaches are being increasingly applied in ecology, and the influence of individual-level trait variation on communities and species has been demonstrated. However, the responses of individual trait variation to environmental changes remain to be explored. To examine the indicating functions of multidimensional traits, individual-level measurements of the dominant diatom genus Aulacoseira Thwaites in the Pearl River Delta were performed, and corresponding responses of three trait indices (trait richness, trait evenness, and trait dispersion) to abiotic and biotic factors were examined. Our results indicated that the three individual trait diversity indices were regulated by different factors. Trait richness was only significantly affected by abiotic factors (temperature), while trait evenness and trait dispersion were regulated by both abiotic and biotic factors. In addition, the direct influence of abiotic factors was more significant than that of biotic factors, implying that the multidimensional trait variation of Aulacoseira was more responsive to environmental changes than to interspecific interactions. Therefore, the multidimensional trait variation of Aulacoseira could be used as an effective indicator to track environmental changes. Our study elucidated the mechanisms relating individual-level trait variation to phytoplankton community dynamics; this could improve our ability to forecast changes in ecosystem properties across environmental gradients.

Exploring the Associations between Alzheimer's Disease and GBM Mediated by Microglia Based on Network Analysis

Previous studies have revealed that there existed epidemic associations between Alzheimer's disease (AD) and many types of tumors, however, the inner biological mechanism connecting these diseases was not clear currently. In this study, we explored the transcriptome associations between AD and glioblastoma multiforme (GBM) that both originate in the brain, using microglia as a bridge, from gene and network levels. Firstly, we extracted human scRNA sequencing datasets from Gene Expression Omnibus (GEO) database, and identified differentially expressed genes within microglia after cell annotation. It was observed that there were 11 common genes shared by AD and GBM dys-regulated genes. Next, we utilized DIAMOnD and Flow Centrality algorithms to identify microglia modules and mediating pathways connecting these two diseases based on global network topology. Among these candidate pathways, the mediating genes FURIN and BACE1 (from SPIKN5 to CSNK1A1) were not only related to the formation of amyloid beta plaques that accumulate in the brain of AD patients, but also involved in cancer biology. Furthermore, the biological explorations of mediating pathways connecting AD and GBM modules reveal inflammatory response, lipid metabolism disorder, and cell proliferation terms. Finally, novel signatures for early AD detection as well as risk models for glioma prognosis were identified based on mediating genes involved in these pathways. In conclusion, this study provided a novel network-based strategy for exploring microglia mediation between AD and GBM and identified candidate signatures for disease detection and prognosis.

Distinct indicators of land use and hydrology characterize different aspects of riverine phytoplankton communities

Given the many threats to freshwater biodiversity, we need to be able to resolve which of the multiple stressors present in rivers are most important in driving change. Phytoplankton are a key component of the aquatic ecosystem, their abundance, species richness and functional richness are important indicators of ecosystem health. In this study, spatial variables, physiochemical conditions, water flow alterations and land use patterns were considered as the joint stressors from a lowland rural catchment. A modeling approach combining an ecohydrological model with machine learning was applied. The results implied that land use and flow regime, rather than nutrients, were most important in explaining differences in the phytoplankton community. In particular, the percentage of water body area and medium level residential urban area were key to driving the rising phytoplankton abundance in this rural catchment. The proportion of forest and pasture area were the leading factors controlling the variations of species richness. In this case deciduous forest cover affected the species richness in a positive way, while, pasture share had a negative effect. Indicators of hydrological alteration were found to be the best predictors for the differences in functional richness. This integrated model framework was found to be suitable for analysis of complex environmental conditions in river basin management. A key message would be the significance of forest area preservation and ecohydrological restoration in maintaining both phytoplankton richness and their functional role in river ecosystems.

Understanding the relative roles of local environmental, geo-climatic and spatial factors for taxonomic, functional and phylogenetic β-diversity of stream fishes in a large basin, Northeast China

The primary objective of this study was to determine the relative roles of local environmental (Local), geo-climatic (Geo), and spatial (Spatial) factors to taxonomic, functional, and phylogenetic β-diversity of stream fish in a large basin in Northeast China. We quantified the current biodiversity patterns of fish communities in the Hun-Tai River using β-diversity. We assessed (i) corresponding contributions of turnover and nestedness within the taxonomic, functional, and phylogenetic β-diversity of fishes; (ii) correlations among β-diversity facets (i.e., taxonomic, functional, and phylogenetic facets); (iii) relative contributions of Local, Geo, and Spatial factors to β-diversity. We collected fish communities from 171 sampling sites. Mantel tests were used to examine the correlation of three facets of β-diversity and their components (i.e., total, nestedness, and turnover). Distance-based redundancy analysis and variation partitioning assess the relative contributions of Local, Geo, and Spatial factors to β-diversity. We found that turnover is the main driving mechanism for β-diversity in fish. Among the facets of β-diversity, taxonomic and phylogenetic facets have strong ecological information association. Spatial factors have a general contribution to various facets of β-diversity and its components. From aspects of fish β-diversity conservation, connectivity and habitat heterogeneity need to be maintained in the entire aquatic environment. In addition, protecting taxonomic β-diversity is helpful for maintaining phylogenetic β-diversity.

[Prevalence and risk factors of coronary artery calcification on lung cancer screening with low-dose CT]

Objective: To investigate the prevalence and risk factors of coronary artery calcification (CAC) on lung cancer screening with low-dose computed tomography (LDCT). Methods: A total of 4 989 asymptomatic subjects (2 542 males and 2 447 females) who underwent LDCT lung cancer screening were recruited at Cancer Hospital, Chinese Academy of Medical Sciences from 2014 to 2017. The visual scoring method was used to assess coronary artery calcification score. χ(2) test or independent t-test was used to compare the difference of CAC positive rate among different groups. Multivariate logistic regression was used to analyze risk factors associated with CAC in the study. Results: Of the 4 989 asymptomatic subjects, CAC occurred in 1 018 cases. The positive rate was 20.4%, of which mild, moderate and severe calcification accounted for 86.3%, 11.4% and 2.3%, respectively. Gender, age, BMI, education level, occupation, smoking history, diabetes, hypertension and hyperlipidemia had statistically significant differences in CAC positive rates among groups. Multivariate logistic regression analysis showed that gender, age, diabetes, hypertension, hyperlipidemia and smoking history were risk factors for CAC. Age, diabetes, hypertension and smoking history were statistically significant risk factors between the mild and moderate CAC group. A total of 1 730 coronary arteries in 1 018 CAC positive cases had calcification, CAC positive rate of left anterior descending was the highest(51.3%); 568 cases (55.8%) were single vessel calcification, 450 cases (44.2%) were multiple vessel calcification. Conclusions: LDCT can be used for the 'one-stop' early detection of lung cancer and coronary atherosclerosis. Gender, age, diabetes, hypertension, hyperlipidemia and smoking are related risk factors for coronary atherosclerosis.

Spatial Factors Outperform Local Environmental and Geo-Climatic Variables in Structuring Multiple Facets of Stream Macroinvertebrates' β-Diversity

Simple Summary

One of the key targets of community ecology and biogeography concerns revealing the variability and underlying drivers of biodiversity. Most current studies understand biodiversity based on taxonomic information alone. Our study was based on macroinvertebrates from 179 stream sampling sites in the Hun-Tai River Basin in Northeastern China. The correlation of different facets of β-diversity was compared while revealing the relative contribution of multiple abiotic factors (i.e., local environmental, geo-climatic, and spatial factors) to shaping β-diversity based on taxonomic, functional, and phylogenetic information. The results showed that functional β-diversity provides important complementary information to taxonomic and phylogenetic β-diversity. Moreover, spatial factors outperform local environmental and geo-climatic variables in structuring multiple facets of stream macroinvertebrates’ β-diversity. Our study provides guidance for future conservation studies of watershed biodiversity, as well as implications for future studies of β-diversity.

Abstract

One of the key targets of community ecology and biogeography concerns revealing the variability and underlying drivers of biodiversity. Most current studies understand biodiversity based on taxonomic information alone, but few studies have shown the relative contributions of multiple abiotic factors in shaping biodiversity based on taxonomic, functional, and phylogenetic information. We collected 179 samples of macroinvertebrates in the Hun-Tai River Basin. We validated the complementarity between the three facets and components of β-diversity using the Mantel test. Distance-based redundancy analysis and variance partitioning were applied to explore the comparative importance of local environmental, geo-climatic, and spatial factors on each facet and component of β-diversity. Our study found that taxonomic and phylogenetic total β-diversity was mainly forced by turnover, while functional total β-diversity was largely contributed by nestedness. There is a strong correlation between taxonomic and phylogenetic β-diversity. However, the correlations of functional with both taxonomic and phylogenetic β-diversity were relatively weak. The findings of variation partitioning suggested that distinct facets and components of macroinvertebrates’ β-diversity were impacted by abiotic factors to varying degrees. The contribution of spatial factors was greater than that of the local environment and geo-climatic factors for taxonomic, functional, and phylogenetic β-diversity. Thus, studying different facets and components of β-diversity allows a clearer comprehension of the influence of abiotic factors on diversity patterns. Therefore, future research should investigate patterns and mechanisms of β-diversity from taxonomic, functional, and phylogenetic perspectives.

[The influence of CT acquisition and reconstruction parameters on the stability of radiomic features of pure ground-glass nodules]

Objective: To investigate the influence of CT reconstruction algorithm, radiation dose, and contrast agent on the stability of radiomic features of pure ground-glass density pulmonary nodules. Methods: A total of 50 pure ground-glass density pulmonary nodules in 35 patients were prospectively selected from Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College in 2018. After reconstructing the original image of the same patient's pulmonary nodules, six sequences of different parameters were obtained. ITK-SNAP software was used to segment different sequences of pure ground-glass density pulmonary nodules. All scanning data were extracted by A. K. software. The radiomic features with good retest reliability were selected by the intraclass correlation coefficient. The statistical software of R language was used to analyze the characteristic parameters. All the radiomic feature values of different sequences were paired and compared. The number of radiomic features changed by acquisition and reconstruction parameters was counted. The influence of different parameters on the reproducibility of pure ground-glass density pulmonary nodules was compared. Results: A total of 391 radiomic features were extracted from 50 cases of pure ground-glass density pulmonary nodules. 320 features with an intraclass correlation coefficient greater than 0.75 were selected for further analysis. By changing the three parameters of CT reconstruction algorithm, radiation dose, and contrast agent simultaneously, the changed radiomic features of the pure ground-glass density pulmonary nodules reach 60.9% (195/320), including 6.7% (1/15) morphological feature, 100.0% (40/40) histogram features, and 58.1% (154/265) texture features. When only one parameter was changed (keeping the other two parameters unchanged), changing the CT reconstruction algorithm, radiation dose, and contrast agent respectively, the changed radiomic features of pure ground-glass density pulmonary nodules were 10.6% (34/320), 30.9% (99/320) and 50.6% (162/320), the difference was statistically significant (P<0.05). When the radiation dose and contrast agent were changed, the radiomic features obtained by the FBP reconstruction algorithm had smaller changes than the features obtained by the 50% ASiR-V algorithm (P=0.001). Conclusions: CT reconstruction algorithm, radiation dose, and contrast agent will affect the radiomic features of pure ground-glass density pulmonary nodules. The contrast agent has the most significant influence on the radiomic features, followed by radiation dose and CT reconstruction algorithm minimum. Compared with morphological features, histogram features and texture features are more likely to be affected by CT reconstruction algorithms, radiation doses, and contrast agents. Compared with the 50% ASiR-V algorithm, the radiomic features obtained by the FBP reconstruction algorithm are less affected by the radiation dose and contrast agent. The influence of these parameters should be fully considered in the radiomic analysis.

Differential uptake of nitrogen forms by two herbs in the Gurbantunggut desert, Central Asia

Understanding how plants adjust their requirements for different N forms can help elucidate plant coexistence strategies in N-limited desert ecosystems. To understand the mechanisms involved, we investigated whether two desert herbs can directly absorb dissolved organic nitrogen (N) and tested whether the patterns changed over different growth stages. Two dominant herbaceous species, Astragalus arpilobus and Arnebia decumbens, from the southern edge of the Gurbantunggut desert, China, were selected. Short-term (24 h) ¹⁵ N-labelled tracer (¹⁵ N-NO₃ , ¹⁵ N-NH₄ , 2-¹³ C-¹⁵ N-Glycine) treatments were conducted at two soil depths (0-5 cm and 5-15 cm) in the season of rapid growth (June) and in the peak biomass season (July). Enrichment in ¹³ C and ¹⁵ N was assessed in the two species receiving glycine. The ratio ¹³ C:¹⁵ N was 0.21-1.39 at the 24-h harvest, suggesting that approximately 10.5-69.5% of glycine had been absorbed. The amount of absorbed ¹⁵ N was significantly affected by species, month, soil depth and N form. The two species absorbed most ¹⁵ N from the 0-5 cm soil layer, and the absorption rate in July was higher than that in June. The absorption of ¹⁵ N-NO₃ and ¹⁵ N-NH₄ was significantly higher than that of 2-¹³ C-¹⁵ N-Glycine. The results indicate that these herbs could use amino acids in the N-deficient desert ecosystem. The two co-existing species used different forms of inorganic N for their requirements and maintained a specific preference throughout various growth stages.

Visible imaging system with changeable field of view on the HL-2A tokamak

A new visible imaging system characterizing a flexible optical design and delivering high resolution frames is established on the HL-2A tokamak. It features a modular configuration, consisting of a front-end imaging lens, a set of bilateral telecentric relay lenses, and a camera. To avoid the effects of plasma radiation (x and gamma-rays) and magnetic field variation on the camera, it should be away from the coils. Therefore, the length of the relay lenses determines the total size of the imaging system. The main feature of this imaging system is to realize the variation of field of view (FOV) by interchanging the front-end prime lenses or by using a zoom lens directly rather than designing the optical system afresh, which lowers the cost drastically. The primary purpose of varying FOV is to enrich the versatility of this system, i.e., focusing on a narrow FOV such as gas puff imaging or a wide FOV such as the plasma cross sections. During the HL-2A experiments, this visible imaging system is used to provide high quality pictures of the plasma-wall interaction, divertor detachment, pellet injections, and so on. The frames confirmed that a strong radiation close to the X point is correlated with the completely detached inner target.

[Clinical features and follow-up outcomes of optic nerve injury induced by acute methanol poisoning]

Acute methanol poisoning harms the optic nerve and central nervous system, can cause irreversible damage, even coma or death in severe cases. This article reported four cases of methanol poisoning. 3 patients mistakenly ingested industrial alcohol containing methanol, the most serious patient suffered from coma, vision loss and other symptoms, the blood methanol concentration was 869.3 μg/ml. Another patient was poisoning caused by inhalation of methanol, with symptoms such as total blindness in the right eye and decreased visual acuity in the left eye. After active supportive treatment, 2 patients had partial recovery of visual acuity, and 2 patients had no sequelae. This article discussed the clinical features, treatment and prognosis of optic nerve damage caused by methanol poisoning, in order to raise awareness of this disease.

[Characteristics of the white matter involvement sites on MRI in patients with multiple gliomas]

The retrospective study included 122 cases of multiple glioma and 183 cases of single glioma. Of these, there were 74 males and 48 female with multiple gliomas, aged 18 to 83 (53±13) years, and 104 males and 79 females with single gliomas, aged 10 to 84 (51±14) years. A standard spatial-based lesion analysis method was used for constructing a spatially distributed frequency heatmap of multiple gliomas, to observe the characteristics of their white matter invasion sites. The spatial distribution was more frequent in the subventricular zone, corpus callosum and cingulate gyrus in the multiple glioma group compared to the single glioma group (P<0.001).The white matter areas of multiple gliomas were more extensively involved, with more frequent involvement of the conjoined fibers (corpus callosum, P<0.05) and contact fibers (cingulate, dome, 0.05<P<0.10) areas.The spatial distribution of the brain and the white matter invasion of multiple gliomas have certain site specificity.

Microeukaryotic Community Shifting Along a Lentic-Lotic Continuum

As an important regulator of ecosystem functions in river systems, microeukaryotes play an important role in energy and material conversion, yet little is known about the shift along a lentic-lotic continuum. In this study, the 18S rRNA genes sequencing was used to identify the microeukaryotic communities at 82 sites along a lentic-lotic continuum with the aim of understanding the impact of upstream inlet river on microeukaryotic communities in Baiyang Lake (BYD) and its downstream. Our results showed that the upstream inlet river affected the diversity and community composition of microeukaryotes in BYD and downstream rivers, and environmental variables greatly affected the composition of microeukaryotic community. The community composition in BYD had lower variabilities. Co-occurrence network analysis revealed that the network was non-random and clearly parsed into three modules, and different modules were relatively more abundant to a particular area. As keystone taxa, some nodes of the upstream microeukaryotic network played an important role in structuring network and maintaining the stability of the ecosystem. In BYD and downstream, the microeukaryotic network was highly fragmented, and the loss of keystone taxa would have an adverse impact on the integrity and function of the microeukaryotic community. Microeukaryotes had strong tendencies to co-occur, which may contribute to the stability and resilience of microeukaryotic communities. Overall, these findings extend the current understanding of the diversity and community composition of microeukaryotic along a lentic-lotic continuum.

Small Run-of-River Dams Affect Taxonomic and Functional β-Diversity, Community Assembly Process of Benthic Diatoms

Being increasingly constructed worldwide, dams are a main driver of flow regime change and biodiversity decline. Although small run-of-river dams have exceeded the number of large dams, their impacts on taxonomic and functional β-diversity as well as community assembly process of aquatic organisms have been largely neglected. Ninety sites within twenty three small run-of-river dams in the Xiangxi River were selected, and the hydrological and physicochemical variables for each site were measured. We analyzed the traits and β-diversity of benthic diatoms, and explored the key driving mechanism of benthic diatom community assembly. Our results indicated that the construction of small run-of-river dams could affect the β-diversity of benthic diatoms and the mechanism of community assembly. Specifically, we found that small run-of-river dams could change the relative contribution of nestedness components to the trait-based β-diversity of benthic diatoms, but generally the taxonomy-based β-diversity was relatively higher than the trait-based β-diversity. Furthermore, the community assembly process of benthic diatoms was also affected. In areas affected directly by small run-of-river dams, dispersal assembly was the key mechanism for community assembly. Compared to unregulated habitats, the dispersal assembly process between the impacted and the unregulated habitats has been enhanced. We advocate that this study can be expanded to other organisms (such as macroinvertebrates, phytoplankton, fish) in future to fully understand impacts of small run-of-river dams on biodiversity from a multi-trophic level aspect. Based on our results, we suggest that maintaining genetic and ecological connectivity based on an effective impact assessment in dry seasons is a potential solution to mitigate the impacts of such dams, as key to adaptive management and sustainability.