Community Structure Function Research Articles

Shifts in functional traits and interactions patterns of soil methane-cycling communities following forest-to-pasture conversion in the Amazon Basin.

Deforestation threatens the integrity of the Amazon biome and the ecosystem services it provides, including greenhouse gas mitigation. Forest-to-pasture conversion has been shown to alter the flux of methane gas (CH4 ) in Amazonian soils, driving a switch from acting as a sink to a source of atmospheric CH4 . This study aimed to better understand this phenomenon by investigating soil microbial metagenomes, focusing on the taxonomic and functional structure of methane-cycling communities. Metagenomic data from forest and pasture soils were combined with in situ CH4 fluxes and soil edaphic factors measurements and analysed using multivariate statistical approaches. We found a significantly higher abundance and diversity of methanogens in pasture soils. As inferred by co-occurrence networks, these microorganisms seem to be less interconnected within the soil microbiota in pasture soils. Metabolic traits were also different between land uses, with increased hydrogenotrophic and methylotrophic pathways of methanogenesis in pasture soils. Land-use change also induced shifts in taxonomic and functional traits of methanotrophs, with bacteria harboring genes encoding the soluble form of methane monooxygenase enzyme (sMMO) depleted in pasture soils. Redundancy analysis and multimodel inference revealed that the shift in methane-cycling communities was associated with high pH, organic matter, soil porosity, and micronutrients in pasture soils. These results comprehensively characterize the effect of forest-to-pasture conversion on the microbial communities driving the methane-cycling microorganisms in the Amazon rainforest, which will contribute to the efforts to preserve this important biome.

Functional structure and interactions within communities composed of cover crops and spontaneous species, along a cropping practices gradient

Inclusion of a cover crop is an interesting way to diversify cropping systems and support ecosystem functions and services impaired by intensified monocultures. However, pure covers are hard to obtain without substantial management, and mixed covers—wherein some spontaneous species coexist with sown cover crops—seem to be a good alternative. Greater insight into factors influencing the composition and density of the spontaneous plant community is needed to achieve relatively good control of the performances of this mixed cover. Here we addressed two questions: 1) How does the functional structure of communities with a highly competitive sown cover crop and/or high initial species diversity differ from the functional structure of communities with the opposite characteristics? 2) Can aboveground species traits explain interactions between cover crops and spontaneous species present in the same community? In a fallowed field in Guadeloupe (West French Indies), we studied communities composed of one sown cover crop species and spontaneous species growing simultaneously in the plot. The study was conducted along two unrelated experimentally-devised gradients resulting from cropping practices: a competitivity gradient of a sown cover crop species and an initial species diversity gradient resulting from an initial soil perturbation induced by the false seedbed technique. These factors (soil tillage modality before cover crop sowing and cover crop species identity) were combined in a split-plot design. Seven and twelve months after cover crop sowing, community species densities and biomasses were assessed. Leaf trait values of the 12 most present species were measured at flowering to describe the functional structure of the community using the community weighted trait means and variances, and a functional diversity index. Our results showed high functional divergence in communities with highly competitive cover crops, which suggests differentiation of functional niches between species, but no clear differences in communities with high and low initial species diversity. We also showed that the studied species were positioned along a gradient from acquisitive to conservative strategies of resource capture and use according to their leaf trait values, regardless of their type (cover crops or spontaneous species), and that cover crop species had higher trait values related to size than spontaneous species. Finally, we demonstrated that interactions between cover crops and spontaneous species could be better explained by the cover crop dynamic height or community biomasses than by the measured aboveground functional traits and that the plant growth habit had a central role. This study shed light on interactions between sown cover crops and spontaneous species, which are pivotal to the design of diversified cropping systems.

Functional community structure modulates zooplankton production rates across boreal lakes

Abstract Although there is a general consensus in ecology that more diverse communities tend to be more productive, it is still unclear whether this holds for aquatic ecosystems, especially with indicators of productivity rates and not just standing biomass proxies. Furthermore, most evidence is based on the results of experimental studies in which biodiversity was assessed through taxonomic richness, although functional indicators could be more relevant. Consequently, we still have a poor understanding of how real community performance is linked to the various features of community structure in natural aquatic ecosystems. Here we explicitly assessed the effect of functional traits and diversity on crustacean zooplankton productivity rates measured across 84 boreal Canadian lakes spanning wide limnological gradients. Productivity was assessed using the chitobiase enzyme method. Redundancy analyses and structured equation modelling were used to assess the relationship between zooplankton production rates, community structure (diversity and functional composition), while accounting for standing biomass and environmental factors After controlling for the effect of environmental factors, zooplankton production rates were positively linked to dominance (lower functional evenness) by certain feeding traits (Daphnia filtration and Chydorus filtration), demonstrating an identity (selection) effect. Overall, the magnitude of the functional compositional effect on production was comparable to the aggregate effect of the environmental variables. Our study demonstrates that zooplankton functional community structure plays an important role in the regulation of a pivotal lake ecosystem function.

Effects of Chemical Fertilizer Reduction Substitute with Organic Fertilizer on Soil Functional Microbes and Lemon Yield and Quality

To clarify the effects of non-rhizosphere/rhizosphere soil functional microbes (nitrifiers, denitrifiers, and phosphorus-solubilizing microorganisms) on lemon yield and quality, the lemon fruit and non-rhizosphere/rhizosphere soil were selected as subjects. To explore the correlation between non-rhizosphere/rhizosphere soil functional microbes and lemon yield and quality under a chemical fertilizer reduction substitute with organic fertilizer, traditional fruit quality determination and multiple molecular techniques were used. The results showed that:① 30% chemical fertilizer reduction substitute with organic fertilizer increased the nitrification intensity and phosphatase activity but effectively controlled the denitrifying enzyme activity. ② The chemical fertilizer reduction substitute with organic fertilizer significantly decreased the abundances of nitrifiers and nirS/nirK-harboring denitrifiers and significantly increased the abundances of nosZ-harboring denitrifier and phoD-harboring microorganisms. However, the diversities of functional microbial community structure did not have clear regularity under chemical fertilizer reduction substitute with organic fertilizer. ③ Compared with that under the application of chemical fertilizer and organic fertilizer alone, lemon yield and quality were the highest under the 30% reduction of chemical fertilizer substitute with organic fertilizer. ④ Nitrogen and its related microbes significantly affected lemon yield through internal and external quality. Phosphorus and its related microbes affected lemon yield mainly through internal quality. In addition, the influence factors of non-rhizosphere soil and rhizosphere soil on lemon intrinsic quality were obviously different. Altogether, these results showed that the 30% reduction of chemical fertilizer substitute with organic fertilizer significantly affected soil nitrogen and phosphorus functional microorganisms and further improved lemon yield and quality.

Seven-decade forest succession reveals how species colonization and extinction drive long-term community structure dynamics

Abstract Understanding how community phylogenetic and functional structures change over succession has gained increasing attention during the last decades, but the lack of long-term time-series data has limited our understanding of the patterns and mechanisms of these changes. This is especially the case for forest communities. Here, we used an exceptionally long-term data over 68 years to analyze the secondary succession dynamics of a subtropical forest in Southeast China. We found that community phylogenetic and functional structures showed opposite temporal trends. The mean pairwise phylogenetic distance between species increased, but the mean nearest taxon distance decreased over succession, indicating both phylogenetically distantly related and sister species co-occurred in late-successional communities. In contrast, both the mean pairwise functional distance and mean nearest functional distance between species decreased over time, and community functional structure switched from overdispersion to clustering. We further distinguished the contributions of species colonization and extinction to community structural changes. We found that the new colonists were generally more distantly related to each other and to the residents than the local extinct species, resulting in increased phylogenetic overdispersion over succession. In contrast, from a functional perspective, we found that species with more similar traits to the resident species had a greater chance to colonize but a lower chance to go locally extinct, which shifted community functional structure toward clustering. Together, our study highlights the critical role of species colonization and extinction in disentangling assembly mechanisms underlying community phylogenetic and functional structures over long-term succession.

Traits of dominant plant species drive normalized difference vegetation index in grasslands globally

AbstractAimTheoretical, experimental and observational studies have shown that biodiversity–ecosystem functioning (BEF) relationships are influenced by functional community structure through two mutually non‐exclusive mechanisms: (1) the dominance effect (which relates to the traits of the dominant species); and (2) the niche partitioning effect [which relates to functional diversity (FD)]. Although both mechanisms have been studied in plant communities and experiments at small spatial extents, it remains unclear whether evidence from small‐extent case studies translates into a generalizable macroecological pattern. Here, we evaluate dominance and niche partitioning effects simultaneously in grassland systems world‐wide.LocationTwo thousand nine hundred and forty‐one grassland plots globally.Time period2000–2014.Major taxa studiedVascular plants.MethodsWe obtained plot‐based data on functional community structure from the global vegetation plot database “sPlot”, which combines species composition with plant trait data from the “TRY” database. We used data on the community‐weighted mean (CWM) and FD for 18 ecologically relevant plant traits. As an indicator of primary productivity, we extracted the satellite‐derived normalized difference vegetation index (NDVI) from MODIS. Using generalized additive models and deviation partitioning, we estimated the contributions of trait CWM and FD to the variation in annual maximum NDVI, while controlling for climatic variables and spatial structure.ResultsGrassland communities dominated by relatively tall species with acquisitive traits had higher NDVI values, suggesting the prevalence of dominance effects for BEF relationships. We found no support for niche partitioning for the functional traits analysed, because NDVI remained unaffected by FD. Most of the predictive power of traits was shared by climatic predictors and spatial coordinates. This highlights the importance of community assembly processes for BEF relationships in natural communities.Main conclusionsOur analysis provides empirical evidence that plant functional community structure and global patterns in primary productivity are linked through the resource economics and size traits of the dominant species. This is an important test of the hypotheses underlying BEF relationships at the global scale.

Seasonality in niche occupation revealed through bird community functional structure in the southern Atlantic rainforest

Seasonal variation in tropical and subtropical systems can have different effects on bird species depending on the resources they use and how they use them. However, despite recent research advances, knowledge of the drivers of the presence and abundance of species in different seasons is still limited for most tropical bird species. In these poorly understood systems, examining seasonal changes in species composition from the perspective of traits related to resource use can provide insight into what resources may be driving bird movements between areas throughout the year and what types of species are more subject to seasonality. Here, we explore bird community seasonality in three forest types (dense, semi‐deciduous and mixed rainforests) subjected to different climatic conditions in one of the world's biodiversity hotspots, the Atlantic Rainforest. We investigated differences between summer and winter in species richness and in the composition of resource‐related species traits (diet, foraging strata and substrates) obtained from the literature. The seasonal differences (summer and winter) between forest types were explored in terms of species and trait composition. We found that the main changes that occurred in bird composition between seasons in the southern Atlantic Rainforest were related to species traits such as diet and foraging strata. In general, the proportion of invertivores was higher in winter than in summer, and in the mixed forest, the forest type exposed to the coldest winters, the proportion of frugivores was lower in winter. Furthermore, species with a more varied diet were better represented in the summer. In general, more generalist species were better represented in the forest type subjected to higher seasonal variations in rainfall. Our results revealed seasonal changes in bird community structure that are related to niche occupation and that were more strongly apparent in the forest type subjected to colder winters.

The effect of biochar prepared at different pyrolysis temperatures on microbially driven conversion and retention of nitrogen during composting

Aerobic composting is one of the most economical ways to produce organic fertilizer from agricultural wastes. In this research, we independently developed a simple composting simulation reactor. The effects of biochar pyrolysised at different pyrolysis temperatures (B1-450 °C; B2-550 °C; and B3-650 °C) on nitrogen conversion (Total nitrogen (TN), ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3−-N), cumulative amount of ammonia (CEA) and nitrous oxide (CEN) emission, nitrogen loss rate (NLR), etc.) and functional microbial community (cbbL, cbbM and nifH) structure in the composting system were studied. Results showed that the addition of biochar significantly improved the efficiency of composting, increased the NO3−-N concentration and reduced the NLR (%) in the composting system (B3 (31.4 ± 2.73)<B2=B1 (41.7 ± 3.29)<B0 (54.5 ± 3.34), p ≤ 0.05), while the loss rate of nitrogen positively correlated with compost pH. Denitrifying bacterial genera such as Pseudomonas, Alcaligenes, Paracoccus, Bacillus, Citrobacter, Mesorhizobium, Thiobacillus and Rhodococcus in this study was an important reason for nitrogen loss during composting, and the abundance of autotrophic microorganisms (such as Sulfuritalea, Hydrogenophaga, Thiobacillus, Thiomonas and Candidatus_Thioglobus) in treatments with biochar (B1, B2 and B3) were higher than that in B0. Besides, the community structure in the treatments B2 and B3 was similar at the end of composting and clearly distinguished from that in B1. Moreover, the five functions predicted by OTUs in this study with the highest proportions were chemoheterotrophy, nitrate reduction, fermentation, aerobic chemoheterotrophy and nitrogen respiration. The study provided a theoretical basis for the application of biochar to improve the compost-related processes.

Non-native Douglas fir promotes epigeal spider density, but has a mixed effect on functional diversity

With climate change altering ecosystems worldwide, forest management in Europe is increasingly relying on more adaptable non-native tree species, such as Douglas fir (Pseudotsuga menziesii). However, the ecological consequences of the increased utilization of Douglas fir on arthropod diversity and ecosystem functioning are not fully known. Here we assessed how non-native Douglas fir as well as large- and small-scale differences in the environmental context, affect epigeal spider abundance, biomass, taxonomic and functional diversity, and community structure in Central European forests. Our study sites were divided into two regions with large differences in environmental conditions, with seven replicates of five stand types, including monocultures of native European beech (Fagus sylvatica), non-native Douglas fir and native Norway spruce (Picea abies), as well as two-species mixtures of European beech and each of the conifers. Contrary to our expectations, Douglas fir promoted small-scale spider diversity, and abundance and biomass (activity density). On the other hand, it decreased spider functional divergence and altered spider community structure. Microhabitat characteristics had opposing effects on spider diversity and activity density, with more open stands harboring a more diverse but less abundant spider community. Overall, our findings suggest that increasing Douglas fir utilization at the expense of Norway spruce does not necessarily decrease the diversity of epigeal arthropods and may even promote local spider diversity and activity density. However, care needs to be taken in terms of biodiversity conservation because typical forest spider species and their functional divergence were more strongly associated with native beech than with coniferous stands.

Impounding Impacts of the Three Gorges Reservoir on Phytoplankton Function Groups and Its Relationship with Resource Use Efficiency

In order to investigate the relationship between phytoplankton community functional group compositions and resource use efficiency in important tributaries of the Three Gorges Reservoir, phytoplankton and environment parameters were sampled from five tributaries, the Xiangxi River, Daning River, Meixi River, Pengxi River, and Huangjin River, in August and November, 2020. There were 119 species (variants) belonging to 62 genera and 7 phyla identified in summer, whereas 118 species (variants) belonging to 7 divisions of 58 genera were found in winter. According to Padisak's theory, all phytoplankton were divided into 25 functional groups, of which there were six important functional groups in both summer and winter:L0, H1, D, Y, MP, and P in summer and L0, H1, A, M, MP, and Y in winter. The α-diversity of the phytoplankton functional group in summer was higher than that in winter. Moreover, a higher α-diversity was also found in downstream samples relative to that in upstream samples, indicating that the community structure was more complex, and the community stability was relatively better in downstream regions of the rivers. Redundancy analysis (RDA) showed that the environment factors, i.e., ν, pH, permanganate index, WT, and RUETN, significantly affected phytoplankton functional groups (P<0.05). Variance partitioning analysis (VPA) indicated that environmental factors had a higher explanatory degree for the change in functional group composition in summer (45.23%); on the contrary, resource use efficiency had a higher explanatory degree in winter (42.33%). The linear fitted model showed that functional groups L0, H1, D, and Y showed a significant positive correlation relationship with RUETN and RUETP in summer, whereas only four functional groups (M, MP, Y, and A) had a linear relationship with RUETP, and all function groups had a good linear relationship with RUETN in winter. These results indicated that the functional groups belonging to cyanobacteria, dinoflagellates, and cryptophyta were more efficient at using limited resources in summer, whereas the diatoms had a good linear relationship with resource use efficiency and formed a dominant group in the low temperature environment of winter. These results suggest that the impounding of the Three Gorges Reservoir area can significantly change the resource use efficiency of phytoplankton, resulting in changes in the phytoplankton functional group composition and community structure.

Microbial community composition and function in an urban waterway with combined sewer overflows before and after implementation of a stormwater storage pipe.

When the wastewater volume exceeds the sewer pipe capacity during extreme rainfall events, untreated sewage discharges directly into rivers as combined sewer overflow (CSO). To compare the impacts of CSOs and stormwater on urban waterways, we assessed physicochemical water quality, the 16S rRNA gene-based bacterial community structure, and EcoPlate-based microbial functions during rainfall periods in an urban waterway before and after a stormwater storage pipe was commissioned. A temporal variation analysis showed that CSOs have significant impacts on microbial function and bacterial community structure, while their contributions to physicochemical parameters, bacterial abundance, and chlorophyll a were not confirmed. Heat map analysis showed that the impact of CSO on the waterway bacterial community structure was temporal and the bacterial community composition in CSO is distinct from that in sewers. Hierarchical clustering analysis revealed that the waterway physicochemical water qualities, bacterial community composition, and microbial community function were distinguishable from the upper reach of the river, rather than between CSO and stormwater. Changes in the relative abundance of tetracycline resistance (tet) genes-especially tet(M)-were observed after CSOs but did not coincide with changes in the microbial community composition, suggesting that the parameters affecting the microbial community composition and relative abundance of tet genes differ. After pipe implementation, however, stormwater did not contribute to the abundance of tet genes in the waterway. These results indicate that CSO-induced acute microbial disturbances in the urban waterway were alleviated by the implementation of a stormwater storage pipe and will support the efficiency of storage pipe operation for waterway management in urban areas.

Dominant ecological processes and plant functional strategies change during the succession of a subtropical forest

Understanding community assembly process could enhance forest conservation and restoration, while which dominant ecological process drives the community assembly during forest succession is still controversial. In this study, the phylogeny-based and functional trait-based indicators were used to investigate the community assembly processes during forest succession in southern China. 30 dominant species and 33 functional trait indicators related to plant competition, reproduction, and defense strategies, 7 environmental factors related to light availability and soil nutrients, and species richness were selected to explore the dominant ecological processes during succession via Monte Carlo method, structural equation model, multiple linear regression, and one-way ANOVA analysis. Results showed that both the community phylogenetic and functional trait structures changed during succession. Phylogenetic structure clustering and functional trait clustering were evident in early succession. In middle succession, the phylogenetic structure and functional trait structure were randomly dispersed. In middle and later succession, the phylogenetic structure clustering, functional trait clustering, and functional trait evenly dispersed were found. The environmental factors, especially the soil P content, and species richness were found to have significant effects on the community assembly processes during succession. Dominant species in early succession always occupied acquisitive strategies and had high light-use ability and low investment in defense, but dominant species in later succession showed more conservative strategies and exhibited diverse defense strategy, reproductive strategy, and light and nutrient resource-use strategy, apparently in order to adapt changing and more complex environments. The results demonstrate that the relative importance of ecological processes changed during succession. Environmental filtering mainly dominated in early succession, and its strength gradually decreased as succession progressed. Both environmental filtering and competitive exclusion had important effects on community assembly in later succession. The assessment of the relative importance of ecological processes during succession could be biased if only based on one plant functional strategy.

The effect of precipitation timing on phylogenetic and functional community structure in a semi-arid steppe.

Changes in the amount and timing of precipitation may affect plant species coexistence. However, little is known about how these changes in precipitation structure plant communities. Here, we conducted a 6-year field precipitation manipulation experiment in the semi-arid steppe of Inner Mongolia, China, to assess the importance of species extinction and colonization in community assembly by incorporating information on phylogenetic and functional relatedness. Our results demonstrated that the decline in plant species richness under decreasing precipitation in the late and entire growing season could be attributed to a decrease in species colonization and an increase in species loss, respectively. The increase in species richness under increasing precipitation in the late growing season was mainly caused by increases in colonizing species. The loss of species that were more closely related to other residents under decreasing precipitation in the late growing season did not alter patterns of phylogenetic overdispersion, and the colonization of species that were more distantly related to residents under increasing precipitation in the late growing season shifted functional relatedness from clustering to randomness. Increasing precipitation may weaken the strength of environmental filtering induced by water stress in this semi-arid steppe and thus increase the probability of successful colonization of functionally dissimilar species relative to residents. Our study suggests that incorporating information on the functional and phylogenetic relatedness of locally lost resident species and the colonization of new species into analyses of community assembly processes can provide new insights into the general responses of plant communities to global change.

Ecological landscape explains aquifers microbial structure

Aquifers have significant social, economic, and ecological importance. They supply 30 % of the freshwater for human consumption worldwide, including agricultural and industrial use. Despite aquifers' importance, the relationships between aquifer categories and their inhabiting microbial communities are still unknown. Characterizing variations within microbial communities' function and taxonomy structure at different aquifers could give a panoramic view of patterns that may enable the detection and prediction of environmental impact caused by multiple sources. Using publicly available shotgun metagenomic datasets, we examined whether soil properties, land use, and climate variables would have a more significant influence on the taxonomy and functional structure of the microbial communities than the ecological landscapes of the aquifer (i.e., Karst, Porous, Saline, Geyser, and Porous Contaminated). We found that these categories are stronger predictors of microbial communities' structure than geographical localization. In addition, our results show that microbial richness and dominance patterns are the opposite of those found in multicellular life, where extreme habitats harbour richer functional and taxonomic microbial communities. We found that low-abundant and recently described candidate taxa, such as the chemolithoautotrophic genus Candidatus Altiarcheum and the Candidate phylum Parcubacteria, are the main contributors to aquifer microbial communities' dissimilarities. Genes related to gram-negative bacteria proteins, cell wall structures, and phage activity were the primary contributors to aquifer microbial communities' dissimilarities among the aquifers' ecological landscapes. The results reported in the present study highlight the utility of using ecological landscapes for investigating aquifer microbial communities. In addition, we suggest that functions played by recently described and low abundant bacterial groups need further investigation once they might affect water quality, geochemical cycles, and the effects of anthropogenic disturbances such as pollution and climatic events on aquifers.

Self-assembly of ammonium assimilation microbiomes regulated by COD/N ratio

Marine microorganisms have an inherent advantage in the treatment of saline wastewater due to their halophilic properties. Ammonium assimilation is the most important and common nitrogen conversion pathway in the ocean, which means that it may be a suitable nitrogen removal strategy under high salinity conditions. However, the targeted construction of engineering microbiomes with ammonium assimilation function for nitrogen recovery has not been realized. Here, we constructed four halophilic ammonium assimilation microbiomes from marine microbial community under varying chemical oxygen demand (COD) to nitrogen (COD/N) ratios. The regulation of COD/N ratio on microbial self-assembly was explored at the phenotypic, genetic, and microbial levels. The results of nitrogen balance tests, functional genes abundance and microbial community structure confirmed that the microbiomes regulated by different COD/N ratios all performed obligate ammonium assimilation functions. >93% of ammonium, 90% of TN, 98% of COD, and 82% of phosphorus were simultaneously removed by microbial assimilation under the COD/N ratio of 20. COD/N ratios significantly affected the self-assembly of microbiomes by selectively enriching heterotrophic microorganisms with different preference for organic carbon load. Additionally, the increase of COD/N ratio intensified the competition among species within the microbiome (the proportion of negative connections of microbial network increased from 5.0% to 24.4%), which may enhance the stability of community structure. Taken together, these findings can provide theoretical guidance for the construction and optimization of engineering microbiomes for synergistic nitrogen removal and recovery.

Characterizing a subtropical hypereutrophic lake: From physicochemical variables to shotgun metagenomic data.

Lake Cajititlán is a subtropical and endorheic lake, which is heavily impacted by nutrient pollution. Agricultural runoff and poorly treated wastewater have entered this reservoir at alarming rates during past rainy seasons, causing the cultural eutrophication of this body of water and resulting in several massive fish kill events. In this study, shotgun metagenomic sequencing was used to examine the taxonomic and functional structure of microbial communities in Lake Cajititlán during the rainy season. Several water quality features and their interactions with microbial communities were also assessed to identify the major factors affecting the water quality and biota, specifically fish species. According to current water quality regulations, most of the physicochemical variables analyzed (dissolved oxygen, pH, Secchi disk, NH4 +, NO3 -, blue-green algae, total phosphorus, and chlorophyll-a) were outside of the permissible limits. Planktothrix agardhii and Microcystis aeruginosa were the most abundant phytoplankton species, and the dominant bacterial genera were Pseudomonas, Streptomyces, and Flavobacterium, with Pseudomonas fluorescens, Stenotrophomonas maltophilia, and Aeromonas veronii representing the most abundant bacterial species. All of these microorganisms have been reported to be potentially harmful to fish, and the latter three (P. fluorescens, S. maltophilia, A. veronii) also contain genes associated with pathogenicity in fish mortality (fur, luxS, aer, act, aha, exu, lip, ser). Genetic evidence from the microbial communities analyzed herein reveals that anthropogenic sources of nutrients in the lake altered genes involved in nitrogen, phosphorus, sulfur, and carbon metabolism, mainly at the beginning of the rainy season. These findings suggest that abiotic factors influence the structure of the microbial communities, along with the major biogeochemical cycles of Lake Cajititlán, resulting in temporal variations and an excess of microorganisms that can thrive in high-nutrient and low-oxygen environments. After reviewing the literature, this appears to be the first study that focuses on characterizing the water quality of a subtropical hypereutrophic lake through associations between physicochemical variables and shotgun metagenomic data. In addition, there are few studies that have coupled the metabolism of aquatic ecosystems with nutrient cycles.

In situ differences in nitrogen cycling related to presence of submerged aquatic vegetation in a Gulf of Mexico estuary.

Estuaries provide a suite of ecosystem services to people but are also under heavy stress from human development including excess nutrient loading and alterations in benthic habitat that affect nutrient cycling. Here we examine the interaction of two important and common ecosystem management priorities in estuaries: limiting eutrophication and restoration of submerged aquatic vegetation (SAV). Rates of benthic nitrogen processing can vary by habitat type and there is need for more complete data on the contribution of SAV to overall nitrogen cycling in estuaries, as well as a need to examine nitrogen cycling in situ to better characterize the role of SAV areal coverage in mediating estuarine eutrophication. We compare nitrogen cycling between two common and adjacent habitat types (SAV and adjacent bare sediment [BS]) in an index coastal estuary using an in situ chamber-based approach to better capture realized habitat differences. We also examined genomic community structure of sediment bacteria and archaea to identify biological indicators of nitrogen exchange. Both mean sediment-water exchange of dissolved N2 and microbial functional community structure differed between SAV and BS. Habitat differences were more consistent with lower variability at locations with low salinity and when sediment organic content was highest, which aligns with findings in other studies. Habitat types differed significantly in microbial composition, including functional groups and genes, like nifH, that may contribute to observed differences in nitrogen cycling. Overall, habitat type appeared most important to nitrogen cycling near the river mouth where sediment nitrogen was higher, and this information has implications for integrated management of habitat restoration/conservation and nutrient loading.

Response-effect trait overlap and correlation in riparian plant communities suggests sensitivity of ecosystem functioning and services to environmental change

Environmental changes and biodiversity loss have emphasized the need to understand how communities affect ecosystem functioning and services. In riparian ecosystems, integrative, generalizable, broad-scale models of ecosystem functioning are still required to fulfill this need. However, few studies have explored the links between functional traits, ecosystem functions, and the services of riparian vegetation. Here we adapt the response-effect trait framework to link drivers, traits, ecosystem functions, and services in riparian ecosystems and assess ecosystem functioning sensitivity to environmental changes. The response-effect trait framework distinguishes between traits related to responses to the environment (response traits) and effects on ecosystem functioning (effect traits). The framework predicts that if response and effect traits are tightly linked, shifts in environmental drivers may alter communities' traits and ecosystem functioning.We adapted the response-effect trait framework for riparian plant communities and used it to assess the overlap between response and effect traits. We tested for correlation among traits identified in the framework and for community functional responses to climatic, topographic, soil, and land cover factors using riparian plant communities along a Temperate-Mediterranean climate gradient in North Portugal.We found a high overlap between response and effect traits, with seven out of thirteen traits identified as both response and effect. Additionally, we found trait linkages in four groups of positively correlated community mean traits. Precipitation and aridity were the most predictive drivers of community functional structure, and life form and leaf area were the most responsive traits.Overall, our findings suggest riparian plant communities are likely to propagate the effects of environmental changes to ecosystem functioning and services, affecting several regulation ecosystem services.This work highlights the sensitivity of riparian ecosystems to environmental changes and how it can affect ecosystem services. Similar functional approaches can be useful for adaptive ecosystem management to sustain biodiversity and ecosystem services.

Taxonomic and functional structure of macrobenthic invertebrate communities and their response to environmental variables along the subbranches of the Nile River (rayahs), Egypt

Macrobenthic invertebrate communities serve as markers of anthropogenic stress in freshwater ecosystems. In this study, 17 sampling sites were selected from two Nile river subbranches (El-Rayah El-Behery and El-Rayah El-Nassery) and subjected to different anthropogenic influences to explore the ecological environment and characteristics of macrobenthos communities. Macrobenthos were studied using taxonomic diversity and biological trait analysis to investigate how human activity and variation in water quality affect their structure and function. A total of 37 taxa represented by 43,389 individuals were recognized. The communities are composed chiefly of Oligochaeta and aquatic insects. Multivariate statistical analyses found that the most influential environmental variables in the structural and functional community were sodium, dissolved oxygen, silicate, pH, calcium, and cadmium. At high levels of pollution, notably sewage and industrial pollution in the northern part of El-Rayah El-Behery, characteristics such as larger body size, detritus feeders, burrowers, and high tolerance to pollution predominated, whereas at low levels of pollution, features such as small body sizes, scraper and predator feeders, intolerant and fairly tolerant of pollution, and climber and swimmer mobility are predominant. The results confirm our prediction that the distribution of macroinvertebrate traits varies spatially in response to environmental changes. The diversity-based method distinguished impacted sewage and industrial sites from thermal effluent sites, while the trait-based approach illustrated an apparent variance between the ecological status of contaminated regions. Therefore, the biological features should be employed in addition to structural aspects for assessing the biodiversity of macroinvertebrate communities under environmental stressors.

The microbial community and functional indicators response to flow restoration in gradient in a simulated water flume.

Flow reduction has greatly affected the river ecological systems, and it has attracted much attention. However, less attention has been paid to response to flow restoration, especially flow restoration in gradient. Flow regime of rivers may affect river functional indicators and microbial community structure. This study simulated the ecological restoration of the flow-reduced river reach by gradiently controlling the water flow and explores the ecological response of environmental functional indicators and microbial community structure to the water flow. The results showed that gross primary productivity (GPP), ecosystem respiration rate (ER) and some water quality indices such as chemical oxygen demand, total nitrogen, and total phosphorus (TP), exhibited positive ecological responses to flow restoration in gradient. GPP and ER increased by 600.1% and 500.2%, respectively. The alpha diversity indices of the microbial community increased significantly with a flow gradient restoration. Thereinto, Shannon, Simpson, Chao1, and Ace indices, respectively, increased by 16.4%, 5.6%, 8.6%, and 6.2%. Canonical correspondence analysis indicated that water flow, Dissolved oxygen and TP were the main influencing factors for changes in bacterial community structure. Microbial community structure and composition present a positive ecological response to flow restoration in gradient. This study reveals that the main variable in the restoration of the flow-reduced river reach is the flow discharge, and it provides a feasible scheme for its ecological restoration.