Distributions of typical contaminant species in urban short-term storm runoff and their fates during rain events:A case of Xiamen City

The pollutants in urban storm runoff, which lead to an non-point source contamination of water environment around cities, are of great concems. The distributions of typical contaminants and the variations of their species in short term storm runoff from different land surfaces in Xiamen City were investigated. The concentrations of various contaminants, including organic matter, nutrients （i.e., N and P） and heavy metals, were significantly higher in parking lot and road runoff than those in roof and lawn runoff. The early runoff samples from traffic road and parking lot contained much high total nitrogen （TN 6-19 mg/L） and total phosphorus （TP 1-3 mg/L）. A large proportion （around 60%） of TN existed as total dissolved nitrogen （TDN） species in most runoff. The percentage of TDN and the percentage of total dissolved phosphorus remained relatively stable during the rain events and did not decrease as dramatically as TN and TP. In addition, only parking lot and road runoff were contaminated by heavy metals, and both Pb （25-120 μg/L） and Zn （0.1-1.2 mg/L） were major heavy metals contaminating both runoff. Soluble Pb and Zn were predominantly existed as labile complex species （50%-99%）, which may be adsorbed onto the surfaces of suspended particles and could be easily released out when pH decreased. This would have the great impact to the environment.

A New Carbon and Oxygen Balance Model Based on Ecological Service of Urban Vegetation

The application of human induced oxygen consumption and carbon emission theory in urban region was summed up and on this base a new model of urban carbon and oxygen balance (UCOB) was constructed by calculating the carbon and oxygen fluxes. The purpose was to highlight the role of vegetation in urban ecosystems and evaluate the effects of various human activities on urban annual oxygen consumption and carbon emission. Hopefully,the model would be helpful in theory to keep the regional balance of carbon and oxygen,and provide guidance and support for urban vegetation planning in the future. To test the UCOB model,the Jimei District of Xiamen City,Fujian Province,China,a very typical urban region,was selected as a case study. The results turn out that Jimei′s vegetation service in oxygen emission and carbon sequestration could not meet the demand of the urban population,and more than 31.49 times of vegetation area should be added to meet the whole oxygen consumption in Jimei while 9.60 times of vegetation area are needed to meet the carbon sequestration targets. The results show that the new UCOB model is of a great potential to be applied to quantitative planning of urban vegetation and regional eco-compensation mechanisms.

Migration of Selenium in Soil-rice-human System and Its Health Risk Assessment in Enshi

In order to to provide scientific reference for the management and development of selenium resources in Enshi,four soil samples and four relevant rice samples were collected from four regions of Enshi,and then selenium content in the soil and rice samples were measured by ICP-MS. Afterwards,the occurrence forms of selenium in the soil samples were detected by continuous extraction. At last,the bioavailability of selenium in rice was studied by the in vitro gastrointestinal model. The results showed that selenium content in soil was 0. 15-5. 42 mg/kg in Enshi. The proportion of water-soluble selenium in soil was the lowest,ranging from 1. 41% to 3. 80%; the proportion of residual selenium was the highest,reaching 36. 1%-41. 7%. Besides,selenium content in rice was 0. 07-1. 61 mg/kg,and the bioconcentration factor of selenium in rice was 0. 22-0. 48. The bioaccessibility of selenium in rice ranged from 45. 7% to 56. 4% in the stomach and from 58. 4% to68. 5% in the small intestine. In addition,the daily intake of selenium per capita( PDI) in Yutangba,Changping,Shadi,and Taiyanghe was490,26,132 and 57 μg/d,indicating that people in Yutangba had the risk of chronic selenium poisoning,and people's diet was rich in selenium in Shadi and Taiyanghe,while people's diet was deficient in selenium in Changping.

Distributive Characteristics of Metallic Nano-particles in China's Urban Water Bodies and their Ecological Risks

Engineering nano-materials & their impact on human health or environmental security constitute a newly emerging R&D hot spot and a key problem now urgently waiting for its solution in supporting the sustainability of China's nano-science and related technology development. At present, water bodies in Chinese cities have been seriously polluted by metallic nano-particles (MNPs) while related monitoring data are found woefully lacking throughout the country. Based on the above understanding, this article gives a round-up explanation on distributive characteristics of MNPs in the river mouths or water bodies of Chinese cities, their ecological hazards as well as our research in this regard, providing some inspiring ideas and data for control over this scourge. In addition, our exploration probes the discharge traits of MNPs themselves and the mechanism underlying its impact on water pollution.

Monitoring Intra-annual Spatiotemporal Changes in Urban Heat Islands in 1449 Cities in China Based on Remote Sensing

This study aimed to accurately study the intra-annual spatiotemporal variation in the surface urban heat island intensities(SUHIIs) in 1449 cities in China.First, China was divided into five environmental regions.Then, the SUHIIs were accurately calculated based on the modified definitions of the city extents and their corresponding nearby rural areas.Finally, we explored the spatiotemporal variation of the mean, maximum, and minimum values, and ranges of SUHIIs from several aspects.The results showed that larger annual mean daytime SUHIIs occurred in hot-humid South China and cold-humid northeastern China, and the smallest occurred in arid and semiarid west China.The seasonal order of the SUHIIs was summer > spring > autumn > winter in all the temperate regions except west China.The SUHIIs were obviously larger during the rainy season than the dry season in the tropical region.Nevertheless, significant differences were not observed between the two seasons within the rainy or dry periods.During the daytime, the maximum SUHIIs mostly occurred in summer in each region, while the minimum occurred in winter.A few cold island phenomena existed during the nighttime.The maximum SUHIIs were generally significantly positively correlated with the minimum SUHIIs during the daytime, nighttime and all-day in all environmental regions throughout the year and the four seasons.Moreover, significant correlation scarcely existed between the daytime and nighttime ranges of the SUHIIs.In addition, the daytime SUHIIs were also insignificantly correlated with the nighttime SUHIIs in half of the cases.

Research on the effects of command-and-control and market-oriented policy tools on China's energy conservation and emissions reduction innovation

The impact of environmental regulation on technology innovation is a hot spot in current research where a large number of empirical studies are based on Porter Hypothesis(PH). However, there are still controversies in academia about the establishment of "weak" and "narrow" versions of PH. Based on the panel data of application for patent of energy conservation and emission reduction(ECER) technology of Chinese city scale during 2008-2014, comprehensive energy price, pollutant emission, etc., mixed regression model and systematic generalized method of moments method were adopted, respectively,to study the impact of market-oriented and command-and-control policy tool on China's ECER technology innovation. The results show that the environmental regulation hindered the technological innovation in the immediate phase; however, it turned out to be positive in the first-lag phase. Hence, the establishment of "weak" PH is time-bounded. The command-and-control policy tool played a more positive role in promoting technological innovation in the first-lag phase than market-oriented policy tool. Therefore, "narrow" PH is not tenable. The reason is that the main participants of China's ECER technology innovation are state-owned companies and public institutions. Regionally speaking, the impact which command-and-control policy tool has on technological innovation at sight was nonsignificant in the eastern, the central, and the western regions of China whilst market-oriented policy tool had a negative effect. And market-oriented policy tool in the central region had strongest negative effect, which would diminish in the eastern region and become weakest in the western region. This was related to regional energy consumption level and the market economic vitality.

Responses of Soil Bacterial Diversity to Fertilization are Driven by Local Environmental Context Across China

Soil microbial diversity is extremely vulnerable to fertilization,which is one of the main anthropogenic activities associated with global changes.Yet we know little about how and why soil microbial diversity responds to fertilization across contrasting local ecological contexts.This knowledge is fundamental for predicting changes in soil microbial diversity in response to ongoing global changes.We analyzed soils from ten 20-year field fertilization(organic and/or inorganic)experiments across China and found that the national-scale responses of soil bacterial diversity to fertilization are dependent on ecological context.In acidic soils from regions with high precipitation and soil fertility,inorganic fertilization can result in further acidification,resulting in negative impacts on soil bacterial diversity.In comparison,organic fer-tilization causes a smaller disturbance to soil bacterial diversity.Despite the overall role of environmental contexts in driving soil microbial diversity,a small group of bacterial taxa were found to respond to fer-tilization in a consistent way across contrasting regions throughout China.Taxa such as Nitrosospira and Nitrososphaera,which benefit from nitrogen fertilizer addition,as well as Chitinophagaceae,Bacilli,and phototrophic bacteria,which respond positively to organic fertilization,could be used as bioindicators for soil fertility in response to fertilization at the national scale.Overall,our work provides new insights into the importance of local environmental context in determining the responses of soil microbial diver-sity to fertilization,and identifies regions with acidic soils wherein soil microbial diversity is more vul-nerable to fertilization at the national scale.

Microbial Community and Urban Water Quality

Urbanization of China is substantial and growing, and water resources are crucial for both economic and social sustainable development. Unfortunately, the frequency and intensity of water contamination events are increasing at an unprecedented rate and often accompanied by increased pollutant loading due to human activities such as irreversible industrialization and urbanization. The impacts of human pollution are most evident and of greatest concern at the microbial level. The research of the Aquatic Ecohealth Group, Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, has been focusing mainly on aquatic microorganisms in the urban environment, from drinking water and landscape water to waste water. Its projects fall into three categories: biomonitoring and bioassessment, microbial ecology and diversity, ecotoxicology and environmental microbiology. Its scientif ic topics include the aquatic ecological safety and microbial food web.

Identifying influencing factors and characterizing key issues in urban sustainable development capacity through machine learning

In response to the United Nations Sustainable Development Goals and China’s“Dual Carbon”Goals(DCGs means the goals of“Carbon Peak and carbon neutrality”),this paper from the perspective of the construction of China’s Innovation Demonstration Zones for Sustainable Development Agenda(IDZSDAs),combines carbon emission-related metrics to construct a comprehensive assessment system for Urban Sustainable Development Capacity(USDC).After obtaining USDC assessment results through the assessment system,an approach combining Least Absolute Shrinkage and Selection Operator(LASSO)regression and Random Forest(RF)based on machine learning is proposed for identifying influencing factors and characterizing key issues.Combining Coupling Coordination Degree(CCD)analysis,the study further summarizes the systemic patterns and future directions of urban sustainable development.A case study on the IDZSDAs from 2015 to 2022 reveals that:(1)the combined identification method based on machine learning and CCD models effectively quantifies influencing factors and key issues in the urban sustainable development process;(2)the correspondence between influencing factors and key subsystems identified by the LASSO-RF combination model is generally consistent with the development situations in various cities;and(3)the machine learning-based combined recognition method is scalable and dynamic.It enables decision-makers to accurately identify influencing factors and characterize key issues based on actual urban development needs.

Urban water system theory and its model development and application

The urban water system theory is an extension of the basin water system science on an urban scale, providing a new systematic solution for the unbalanced human-water relationship and severe water challenges, such as waterlogging, black and odorous water, and ecological degradation caused by urbanization. Most existing studies on urban water systems have focused on individual water cycle processes linked with water supply and sewage treatment plants, but mutual feedback between the water cycle and its associated material circulation and water ecology, as well as human processes, still needs further exploration. In this paper, the concept, theory, and technical methodology of the urban water system were developed based on the water cycle and basin water system science. The Urban Water System 5.0(UWS 5.0) model was developed by integrating the Time Variant Gain rainfall-runoff Model with Urban water system(TVGM_Urban) in different underlying surface conditions for analyzing the natural-social water cycle processes and their associated water environmental and ecological processes and the influence of multiscale sponge measures. Herein, five major simulation functions were realized: rainfall-runoff-nonpoint source pollutant load,water and pollutant transportations through the drainage network system, terminal regulation and purification, socioeconomic water cycle, and water system assessment and regulation. The location for the case study used in this paper was Wuhan City. The findings showed that the entire urban water system should consider the built-up area and its associated rivers and lakes as the research object and explore the integrations among the urban natural-social water cycle and river regulations inside and outside of the city as well as the effects of socioeconomic development and sponge measures on the water quantity-quality-ecology processes. The UWS 5.0 model efficiently simulated the urban rainfall-runoff process, total nitrogen(TN) and total phosphorus(TP) concentrations in water bodies, and characteristic indicators of socioeconomic development. For the rainfall-runoff simulations, the correlation coefficient and Nash-Sutcliffe efficiency(NSE) fall under the excellent and good classes, respectively. For the TN and TP concentration simulations, results exhibited good bias and the correlation coefficients exceeded 0.90 for 78.1% of the sampled sites. The simulation of 18 socioeconomic indicators provided excellent bias, correlation coefficient, and NSE values of 100%, 83.3%, and 69.4% to total indicators, respectively. Based on the well-calibrated UWS 5.0 model, the source sponge,artificial enhancement, and source reduction-path interception-terminal treatment measures were optimized, which considerably mitigated waterlogging, black and odorous water, and lake eutrophication, respectively. The mitigation performance revealed that the maximum inundated area for a once-in-10-year rainfall event was reduced by 32.6%, the removal ratio of the black and odorous water area was 65%, the comprehensive trophic state index of water bodies was reduced by 37%, and the green development level of Wuhan City in 2020 increased from 0.56 to 0.67. This study is expected to advance the intersection and development of multidisciplinary fields(e.g., urban hydrology, environmental science, and ecology) and offer an important theoretical and technical basis for solving urban complex water issues and promoting green development of cities.

A novel strategy of tannery sludge disposal–converting into biochar and reusing for Cr(Ⅵ)removal from tannery wastewater

Tannery sludge with high chromium content has been identified as hazardous solid waste due to its potential toxic effects.The safety disposal and valorization of the tannery sludge remains a challenge.In this study,the chromium stabilization mechanism was systematically investigated during chromium-rich tannery sludge was converted to biochar and the removal performance of the sludge biochar(SBC)for Cr(Ⅵ)from tannery wastewater was also investigated.The results showed that increase in pyrolysis temperature was conductive to the stabilization of Cr and significant reduction of the proportion of Cr(Ⅵ)in SBC.It was confirmed that the stabilization of chromium mainly was attributed to the embedding of chromium in the C matrix and the transformation of the chromium-containing substances from the amorphous Cr(OH)_(3)to the crystalline state,such as(FeMg)Cr_(2)O_(5).The biochar presented high adsorption capacity of Cr(Ⅵ)at low pH and the maximal theoretical adsorption capacity of SBC produced at 800°C can reach 352 mg Cr(Ⅵ)/g,the process of which can be well expressed by Langmuir adsorption isotherm and pseudo second order model.The electrostatic effect and reduction reaction were dominantly responsible for the Cr(Ⅵ)adsorption by SBC800.Overall,this study provided a novel strategy for the harmless disposal and resource utilization for the solid waste containing chromium in leather industry.

Fundamentals and application in phytoremediation of an efficient arsenate reducing bacterium Pseudomonas putida ARS1

Arsenic is a ubiquitous environmental pollutant.Microbe-mediated arsenic biotransformations significantly infuence arsenic mobility and toxicity.Arsenic transformations by soil and aquatic organisms have been well documented,while little is known regarding effects due to endophytic bacteria.An endophyte Pseudomonas putida ARS1 was isolated from rice grown in arsenic contaminated soil.P.putida ARS1 shows high tolerance to arsenite(As(Ⅲ))and arsenate(As(V)),and exhibits efficient As(V)reduction and As(Ⅲ)effux activities.When exposed to 0.6 mg/L As(V),As(V)in the medium was completely converted to As(Ⅲ)by P.putida ARS1 within 4 hr.Genome sequencing showed that P.putida ARS1 has two chromosomal arsenic resistance gene clusters(arsRCBH)that contribute to efficient As(V)reduction and As(Ⅲ)effux,and result in high resistance to arsenicals.Wolffia globosa is a strong arsenic accumulator with high potential for arsenic phytoremediation,which takes up As(Ⅲ)more efficiently than As(V).Co-culture of P.putida ARS1 and W.globosa enhanced arsenic accumulation in W.globosa by 69%,and resulted in 91%removal of arsenic(at initial concentration of 0.6 mg/L As(V))from water within 3 days.This study provides a promising strategy for in situ arsenic phytoremediation through the cooperation of plant and endophytic bacterium.

Green batch prepared a novel C/P co-doping urchin-like TiO_(2)for enhanced photocatalytic degradation and mineralization of trimethoprim

In advancing the practical application of photocatalytic degradation for pollutant removal,batch preparation of environmentally friendly photocatalysts plays a crucial role.Herein,we prepared C/P co-doped urchin-like TiO_(2)(C/PeTiO_(2))through a straightforward room temperature impregnation and atmospheric annealing process.Phytic acid served as the dopant precursor for introducing C and P onto the TiO_(2)surface.This doping process was verified through energy dispersive X-ray spectroscopy(EDX),electron spin resonance(ESR),and X-ray photoelectron spectroscopy(XPS)analysis.The C/PeTiO_(2)photocatalyst exhibited exceptional efficiency in degrading the target compound trimethoprim(TMP),achieving a degradation of 98%TMP within 60 min and a mineralization of 40%TMP within 120 min,which were respectively 2.4 and 1.6 times higher than that of pristine TiO_(2).The intermediate products of TMP were detected,and a plausible degradation pathway was proposed.Photoelectric characterization results also confirmed that C/P co-doping could effectively enhance the carrier separation efficiency of C/PeTiO_(2).The catalysts prepared using the scaled-up impregnation system and reusing the phytic acid solution consistently demonstrated stable catalytic performance,which confirmed the viability of the method for green and batch preparation of C/P co-doped TiO_(2).Notably,the obtained catalyst consistently exhibited high degradation efficacy in various real water bodies,highlighting its substantial potential for practical application.The green and batch preparation method of C/PeTiO_(2)introduces a novel approach to the practical application of photocatalysis technology in treatment of water contaminants.

Different responses of soil fauna gut and plant rhizosphere microbiomes to manure applications

Microbial attributes were compared between soil fauna gut and plant rhizosphere.•Manure applications decreased or increased gut or rhizosphere bacterial diversity.•Stochastic or deterministic processes drove gut or rhizosphere bacterial assembly.•Manure applications increased bacterial network complexity of gut and rhizosphere.Diverse microbes inhabit animals and plants,helping their hosts perform multiple functions in agricultural ecosystems.However,the responses of soil fauna gut and plant rhizosphere microbiomes to livestock manure applications are still not well understood.Here we fed Protaetia brevitarsis larvae(PBL)with chicken manure and collected their frass.The frass and manure were applied as fertilizers to lettuce pots.We then compared the changes of microbial diversity,community assembly,and potential functions between the gut group(i.e.,all PBL gut and frass samples)and the rhizosphere group(i.e.,all rhizosphere soil samples).We revealed that manure applications(i.e.,feeding or fertilization)decreased bacterial diversity in the gut group but increased that in the rhizosphere group.Particularly,the proportions of Bacilli in the gut group and Gammaproteobacteria in the rhizosphere group were increased(up to a maximum of 33.8%and 20.4%,respectively)after manure applications.Stochastic and deterministic processes dominated community assembly in the gut and rhizosphere microbiomes,respectively.Manure applications increased the microbial co-occurrence network complexity of both the gut and rhizosphere groups.Moreover,the proportions of functional taxa associated with human/animal pathogens in the gut group and carbon/nitrogen cycling in the rhizosphere group were enhanced(up to 2.6-fold and 24.6-fold,respectively).Our findings illustrate the different responses of microbial diversity,community assembly,and potential functions in soil fauna gut and plant rhizosphere to manure applications.The results could enhance our knowledge on the reasonable utilization of animal and plant microbiomes in agricultural management.

Terrestrial invertebrate hosts of human pathogens in urban ecosystems

Terrestrial invertebrates in urban ecosystems are extremely species-rich,have many important roles in material flow and energy circulation,and are host to many human pathogens that pose threats to human health.These invertebrates are widely distributed in urban areas,including both out-and in-door environments.Consequently,humans are frequently in contact with them,which provides many opportunities for them to pose human health risks.However,comprehensive knowledge on human pathogen transfer via invertebrates is lacking,with research to date primarily focused on dipterans(e.g.,mosquitoes,flies).Here,we take a broad taxonomic approach and review terrestrial invertebrate hosts(incl.mosquitoes,flies,termites,cockroaches,mites,ticks,earthworms,collembola,fleas,snails,and beetles)of human pathogens,with a focus on transmission pathways.We also discuss how urbanization and global warming are likely to influence the communities of invertebrate hosts and have flow-on risks to human health.Finally,we identify current research gaps and provide perspectives on future directions.

Main environmental drivers of abundance,diversity and community structure of comammox Nitrospira in paddy soils

The recently discovered complete ammonia oxidizers comammox Nitrospira contain clades A and B that can establish an independent one-step nitrification process;however,little is known about their environmental drivers or habitat distributions in agricultural soils.Previous studies on comammox Nitrospira in paddy soils have mainly focused on small-scale samples,and there is a lack of multisite research on comammox Nitrospira in paddy soils.In this study,we conducted a survey of 36 paddy soils to understand the community structure,abundance,and diversity of comammox Nitrospira and the degree to which they are affected by environmental factors at a large scale.Comammox Nitrospira were found to be widely distributed among the paddy soils.The abundance of comammox Nitrospira clade A was mostly lower than that of clade B,whereas its diversity was mostly higher than that of clade B.Correlation analysis showed that multiple factors affected(P<0.05)the abundance of comammox Nitrospira,including soil pH,organic matter,total carbon,and total nitrogen,latitude,mean annual temperature,and mean annual precipitation.Moreover,there was a clear relationship between the comammox Nitrospira community and habitat,indicating that some amplicon sequence variants(ASVs)had a unique dominant position in specific habitats.Phylogenetic analysis showed that the ASVs of comammox Nitrospira clade A clustered with the known sequences in the paddy soils and were significantly different from the known sequences in other habitats,which may be related to the unique paddy field habitat.In contrast,comammox Nitrospira clade B showed no clear habitat dependence.These results support the wide distribution and high abundance of comammox Nitrospira in paddy soils and provide novel insights into nitrogen cycling and nutrient management in agricultural ecosystems.

Ecology and risks of the global plastisphere as a newly expanding microbial habitat

Plastic offers a new niche for microorganisms,the plastisphere.The everincreasing emission of plastic waste makes it critical to understand the microbial ecology of the plastisphere and associated effects.Here,we present a global fingerprint of the plastisphere,analyzing samples collected from freshwater,seawater,and terrestrial ecosystems.The plastisphere assembles a distinct microbial community that has a clearly higher heterogeneity and a more deterministically dominated assembly compared to natural habitats.New coexistence patterns—loose and fragile networks with mostly specialist linkages among microorganisms that are rarely found in natural habitats—are seen in the plastisphere.Plastisphere microbiomes generally have a great potential to metabolize organic compounds,which could accelerate carbon turnover.Microorganisms involved in the nitrogen cycle are also altered in the plastisphere,especially in freshwater plastispheres,where a high abundance of denitrifiers may increase the release of nitrite(aquatic toxicant)and nitrous oxide(greenhouse gas).Enrichment of animal,plant,and human pathogens means that the plastisphere could become an increasingly mobile reservoir of harmful microorganisms.Our findings highlight that if the trajectory of plastic emissions is not reversed,the expanding plastisphere could pose critical planetary health challenges.

Urban agriculture as nature-based solutions:Three key strategies to tackle emerging issues on food security in Chinese cities under climatic and non-climatic challenges

1Introduction Achieving food and water security,according to the United Nations Sustainable Development Goals(SDGs),only requires a minimal environmental cost(Batalini de Macedo et al.,2022).However,in terms of agriculture,blindly devoting efforts to offset low-productivity farming or production techniques and industries,without systematic water,fertiliser,farm residue,tillage,and fallow management,will eventually interrupt the carbon sink under the soil and escalate greenhouse gas emissions,which is not helpful to meeting global climate targets.Thus,sciencebased land management practices are essential to decouple agricultural productivity from greenhouse gas emissions(Buscardo et al.,2021).

A commentary review on the use of normalized diff erence vegetation index(NDVI)in the era of popular remote sensing

The Normalized Diff erence Vegetation Index(NDVI),one of the earliest remote sensing analytical products used to simplify the complexities of multi-spectral imagery,is now the most popular index used for vegetation assessment.This popularity and widespread use relate to how an NDVI can be calculated with any multispectral sensor with a visible and a near-IR band.Increasingly low costs and weights of multispectral sensors mean they can be mounted on satellite,aerial,and increasingly—Unmanned Aerial Systems(UAS).While studies have found that the NDVI is effective for expressing vegetation status andquantified vegetation attributes,its widespread use and popularity,especially in UAS applications,carry inherent risks of misuse with end users who received little to no remote sensing education.This article summarizes the progress of NDVI acquisition,highlights the areas of NDVI application,and addresses the critical problems and considerations in using NDVI.Detailed discussion mainly covers three aspects:atmospheric eff ect,saturation phenomenon,and sensor factors.The use of NDVI can be highly eff ective as long as its limitations and capabilities are understood.This consideration is particularly important to the UAS user community.

Urbanization reduces resource use efficiency of phytoplankton community by altering the environment and decreasing biodiversity

Urbanization often exerts multiple effects on aquatic and terrestrial organisms,including changes in biodiversity,species composition and ecosystem functions.However,the impacts of urbanization on river phytoplankton in subtropical urbanizing watersheds remain largely unknown.Here,we explored the effects of urbanization on phytoplankton community structure(i.e.,biomass,community composition and diversity)and function(i.e.,resource use efficiency)in a subtropical river at watershed scale in southeast China over 6 years.A total of 318 phytoplankton species belonging into 120 genera and 7 phyla were identified from 108 samples.Bacillariophyta biomass showed an increasing trend with increasing urbanization level.The phytoplankton community shifted from Chlorophyta dominance in rural upstream waters to Bacillariophyta dominance in urbanized downstream waters.Furthermore,phytoplankton diversity and resource use efficiency(RUE=phytoplankton biomass/total phosphorus)were significantly decreased with increasing urbanization level from upstream to downstream.Phytoplankton RUE exhibited a significant positive correlation with species richness,but a negative correlation with phytoplankton evenness.The variation in environmental factors(turbidity,total nitrogen,NH_(4)^(+)-N,total phosphorus,PO_(4)^(3-)-P and percentage urbanized area)was significantly correlated with phytoplankton diversity and RUE.Overall,our results revealed the influence of urbanization on phytoplankton community structure and ecosystem function was due to its altering the environmental conditions.Therefore,human-driven urbanization may play crucial roles in shaping the structure and function of phytoplankton communities in subtropical rivers,and the mechanism of this process can provide important information for freshwater sustainable uses,watershed management and conservation.