Search

Urbanization is one of the major drivers of biotic homogenization (i.e., decrease in beta diversity) in freshwater systems. However, only a few studies have simultaneously examined how urbanization affects multiple facets (i.e., taxonomic, functional and phylogenetic) of beta diversity and its underlying ecological drivers in urban river macroinvertebrates. Here, we distinguished the patterns and ecological mechanisms of multiple facets of macroinvertebrate beta diversity weighted by incidence and abundance data in a subtropical river system with a distinct urbanization gradient. We also investigated how total beta diversity patterns stem from replacement versus richness difference among sites. Our results showed that taxonomic and phylogenetic beta diversities weighted by incidence data were primarily driven by replacement of taxa, whereas the richness difference contributed more to multiple facets of beta diversity based on abundance data. Furthermore, multiple facets of beta diversity decreased with urbanization for both incidence-weighted and abundance-weighted data, but the former showed more substantial decreases. Both replacement and richness difference components contributed roughly equally to the decline of incidence-weighted beta diversity. In contrast, the losses of abundance-weighted beta diversity were mainly associated with replacement of taxa. Variation partitioning results revealed that all beta diversity measures based on incidence data were governed primarily by local and land-use variables, whereas spatial variables were more relevant in driving beta diversity weighted by abundance data. Overall, by comparing different facets and components of beta diversity weighted by incidence versus abundance data, we suggest that incidence-weighted data may be more sensitive in portraying the impacts of urbanization on macroinvertebrate diversity. This likely resulted from the fact that incidence-weighted data shows the importance of rare taxa in shaping homogenization induced by urbanization.

Littoral zones in oligotrophic lakes play an essential role in supporting animal consumers and in the exchange of matter between the water body and the terrestrial sources, but are easily altered by changes in water level. We studied Qinghai Lake, a deep oligotrophic lake in northwest China, where lake water level has increased rapidly in recent years, altering the character of the littoral zones. We sampled common organisms and used stable carbon and nitrogen isotope analyses to compare how contributions of different sources (allochthonous and autochthonous) to the diets of consumers differed between sand (original habitat, OH) and submerged grassland (new habitat, NH) substrate habitat conditions. Our results showed that allochthonous resources (i.e., terrestrial detritus) constituted the largest diet proportion of consumers in OH due to poor nutrient conditions, while consumers in NH utilized more autochthonous resources (i.e., Cladophora and phytoplankton). We also found that terrestrial nutrient subsidies from soil and decomposed grass led to increased biomasses of Cladophora, phytoplankton, zooplankton and zoobenthos in NH compared to those in OH, accounting for autochthonous replacement of part of the allochthonous resources in NH. Therefore, hydrological conditions may alter the trophic interactions within littoral food webs, contributing to a more complex and interconnected food web. Overall, our results suggest that the littoral food webs of Qinghai Lake are vulnerable to changes in hydrological conditions, which may be enhanced by climate change.

Abstract Background Disentangling the relative roles of environmental filtering and spatial processes in structuring ecological communities is a central topic in metacommunity ecology. Metacommunity ecology in the temperate river ecosystems has been well developed, while less attention has been paid to subtropical urban river networks. Here, we examined the ecological factors and seasonal difference in structuring macroinvertebrates metacommunity assembly in the subtropical urban river networks in Shenzhen, South China. Results Our results revealed that there was no significant distinction of macroinvertebrate community composition among seasons, with only the relative abundance of Mollusca and Odonata significantly differed in both wet and dry seasons. One possible explanation was that most macroinvertebrates are generally pollution-tolerant taxa characterized with nonseasonal life cycle. In addition, distance-based redundancy analysis and variation partitioning approach revealed that metacommunity was determined equally by the environmental and dispersal-related factors. Further, our results showed that, although a slight temporal variation of relative contribution, the identity and explanation power of ecological factors were different among seasons. Specifically, stronger environmental filtering structuring community dynamics was observed in the dry than wet seasons, which might be owing to higher environmental heterogeneity under a low water-flow condition. Moreover, we detected that the influence of spatial processes was stronger in the wet than dry seasons, indicating an obvious dispersal processes due to high connectivity among sites. Conclusion Overall, our results revealed that environmental and spatial factors equally explained variations of macroinvertebrate metacommunity, implying the necessity of considering dispersal-related processes structuring ecological communities in river bioassessment programs. Moreover, degraded habitat conditions and water quality were the predominant factors that affected macroinvertebrate communities, indicating the significance and feasibility of improving local abiotic conditions to sustain local biodiversity. Further, our findings revealed the importance of seasonal dynamics of these urban river networks in structuring macroinvertebrate metacommunity. Thereby, our study improves the understanding of ecological processes governing macroinvertebrate metacommunity and underlines the idea that community ecology studies should go beyond the single snapshot survey in river networks.

Hemienchytraeus wuhanensis sp. nov. is described from hardwood forest soil in Wuhan, China. This moderately sized enchytraeid species of 6–9 mm body length is characterized by: (1) an oesophageal appendage with tertiary branches, (2) three pairs of secondary pharyngeal gland lobes in V, VI, VII, (3) five pairs preclitellar nephridia, from 5/6 to 9/10, (4) dorsal vessel originating in clitellar segments, (5) a girdle-shaped clitellum, (6) a relatively small male reproductive apparatus without seminal vesicle, and (7) spermathecae that extend to VI–VII. DNA barcodes of paratype specimens of the new species are provided. Previous species records of Hemienchytraeus from China are critically discussed.

Under a global change scenario, human-induced impacts alter multiple facets of river biodiversity (i.e., taxonomic, functional and phylogenetic). Hence, focusing on changes in community assembly and different diversity dimensions along anthropogenic impact gradients is of paramount importance for ecological research. Here, we classified stream sites into near-pristine (NP), moderately impacted (MI) and highly impacted (HI) categories based on a comprehensive anthropogenic impact score for the Hanjiang River Basin (China), and tested for differences in patterns of functional (FD) and phylogenetic diversity (PD). Our study suggests that NP sites showed higher FD and PD than impacted streams (MI and HI), with their communities being phylogenetically overdispersed and mostly shaped by random processes. Anthropogenically impacted sites mostly harbored closely related and functionally similar species, although the degree of clustering varied between NP, MI and HI streams, thereby confirming predictions that human activities contribute to the loss of evolutionary history and functional space in running waters. Importantly, we identified the influence of underlying deterministic mechanisms on the homogenization of both functional and phylogenetic facets of diversity. Similarly, NP sites exhibited the greatest proportion of evolutionarily distinct lineages, suggesting that anthropogenic impacts also threaten phylogenetically unique clades. Overall, this study contributed to a better understanding of multiple diversity patterns in aquatic insect communities by generating new empirical evidence of human-induced degradation of subtropical stream ecosystems in China.

To improve our understanding on the temporal aspects of metacommunity structure, we focused on benthic macroinvertebrates collected seasonally (i.e., wet, drying, dry and rewetting seasons) in Dongting Lake, a large subtropical floodplain lake in China. We employed the elements of metacommunity structure (EMS) framework and variation partitioning to examine whether metacommunity structure and its underlying mechanisms vary among seasons with distinct biotic and abiotic features. We found gradual shifts in the main assembly mechanisms throughout the year, from apparent spatial structuring (potentially indicative of mass effects) in the wet season to more environmental filtering dynamics in the dry season. When the degree of connectivity was high in the wet season, the benthic metacommunity was characterized by nested structure associated with clumped species loss, and was shaped mainly by spatial processes. However, quasi-Clemensian structure was assigned to metacommunities in the transitional seasons with intermediate connectivity, during which environmental variables were more important than spatial factors in describing community structure. When the degree of connectivity was low in the dry season, the benthic metacommunity displayed Clementsian structure, which was configured solely by environmental variables. The rapid shifts in metacommunity dynamics between seasons mainly result from the considerable changes in the hydrological conditions of Dongting Lake, as the studied system varies from lacustrine to fluvial phases within a single year. Taken together, our results revealed that taking temporal aspects into account gives a better insight into metacommunity organization, especially when the studied systems embrace remarkable variability in hydrological regimes.

Abstract Identifying seasonal shifts in community assembly for multiple biological groups is important to help enhance our understanding of their ecological dynamics. However, such knowledge on lotic assemblages is still limited. In this study, we used biological traits and functional diversity indices in association with null model analyses to detect seasonal shifts in the community assembly mechanisms of lotic macroinvertebrates and diatoms in an unregulated subtropical river in China. We found that functional composition and functional diversity (FRic, FEve, FDis, MNN, and SDNN) showed seasonal variation for macroinvertebrate and diatom assemblages. Null models suggested that environmental filtering, competitive exclusion, and neutral process were all important community assembly mechanisms for both biological groups. However, environmental filtering had a stronger effect on spring macroinvertebrate assemblages than autumn assemblages, but the effect on diatom assemblages was the same in both seasons. Moreover, macroinvertebrate and diatom assemblages were shaped by different environmental factors. Macroinvertebrates were filtered mainly by substrate types, velocity, and CODMn, while diatoms were mainly shaped by altitude, substrate types, and water quality. Therefore, our study showed (a) that different biological assemblages in a river system presented similarities and differences in community assembly mechanisms, (b) that multiple processes play important roles in maintaining benthic community structure, and (c) that these patterns and underlying mechanisms are seasonally variable. Thus, we highlight the importance of exploring the community assembly mechanisms of multiple biological groups, especially in different seasons, as this is crucial to improve the understanding of river community changes and their responses to environmental degradation.

Abstract Deterministic and stochastic processes are two major factors shaping community dynamics, but their relative importance remains unknown for many aquatic systems, including those in the high‐elevation Qinghai–Tibet Plateau. Here, we explored the causes of multidimensional beta diversity patterns (i.e., taxonomic, functional, and phylogenetic) of a macroinvertebrate metacommunity in this large aquatic system by using multiple approaches (i.e., null models, phylogenetic signal testing, and ordination‐based approaches). To obtain insights into community assembly mechanisms, we also analyzed beta diversity in two deconstructed sub‐metacommunities (e.g., different tributaries and the main lake body). We found that most functional traits showed significant phylogenetic signals, indicating that the functional traits were profoundly influenced by evolutionary history. The null models showed randomness of functional and phylogenetic beta diversities for the whole basin and its tributaries, confirming the importance of stochasticity over deterministic processes in controlling community structure. However, both phylogenetic and functional community structures were clustered in the Qinghai Lake, probably reflecting the importance of environmental filtering. Ordination‐based approaches also revealed that both environmental factors and spatial processes accounted for variation in taxonomic, functional, and phylogenetic beta diversity. More specifically, environmental filtering was more important than spatial processes for the functional dimension, but the opposite was true for the taxonomic and phylogenetic dimensions. The paleogeographic history of the Qinghai Lake basin may have contributed substantially to the prevalence of stochastic processes. Overall, this study provides a better understanding of ecological patterns and assembly mechanisms of macroinvertebrate communities across this poorly known high‐elevation aquatic system that is highly sensitive to climate warming.

Abstract Environmental filtering and spatial structuring are important ecological processes for the generation and maintenance of biodiversity. However, the relative importance of these ecological drivers for multiple facets of diversity is still poorly understood in highland streams. Here, we examined the responses of three facets of stream macroinvertebrate alpha diversity to local environmental, landscape‐climate and spatial factors in a near‐pristine highland riverine ecosystem. Taxonomic (species richness, Shannon diversity, and evenness), functional (functional richness, evenness, divergence, and Rao's Quadratic entropy), and a proxy of phylogenetic alpha diversity (taxonomic distinctness and variation in taxonomic distinctness) were calculated for macroinvertebrate assemblages in 55 stream sites. Then Pearson correlation coefficient was used to explore congruence of indices within and across the three diversity facets. Finally, multiple linear regression models and variation partitioning were employed to identify the relative importance of different ecological drivers of biodiversity. We found most correlations between the diversity indices within the same facet, and between functional richness and species richness were relatively strong. The two phylogenetic diversity indices were quite independent from taxonomic diversity but correlated with functional diversity indices to some extent. Taxonomic and functional diversity were more strongly determined by environmental variables, while phylogenetic diversity was better explained by spatial factors. In terms of environmental variables, habitat‐scale variables describing habitat complexity and water physical features played the primary role in determining the diversity patterns of all three facets, whereas landscape factors appeared less influential. Our findings indicated that both environmental and spatial factors are important ecological drivers for biodiversity patterns of macroinvertebrates in Tibetan streams, although their relative importance was contingent on different facets of diversity. Such findings verified the complementary roles of taxonomic, functional and phylogenetic diversity, and highlighted the importance of comprehensively considering multiple ecological drivers for different facets of diversity in biodiversity assessment.

Drought has is becoming increasingly serious abiotic stress that influences plant growth. Endophytes are non-pathogenic plant-associated bacteria that can play an important role in conferring plant resistance to drought stress. In this study, drought stress resulted in the evident breakdown of the chloroplast membrane system in leaf cells, whereas Bacillus pumilus inoculation improved the integrity of chloroplast and mitochondria cell structure. Thus chlorophyll content, photosynthetic parameters and water use efficiency increased. The inoculation of endophytes alleviated the inhibitory effect of drought stress on Glycyrrhiza uralensis growth. We concluded that B. pumilus inoculation enhanced the growth and drought tolerance of G. uralensis through the protection of chloroplast submicroscopic structure, and thus increased chlorophyll content, efficient photosynthetic rate, and improved water state.

Metacommunity ecology highlights the importance of integrating simultaneously environmental filtering and spatial processes, such as mass effects and dispersal limitation, into investigation of community assembly. However, few studies to date have tried to examine mass effects and dispersal limitation as independent ecological mechanisms along with environmental filtering in shaping biological communities in river networks. We examined the relative importance of three factor groups, i.e., environmental variables, within-river spatial factors (indicative of mass effects) and basin identity (referring to dispersal limitation) on a macroinvertebrate metacommunity and nine trait-based deconstructed sub-metacommunities from seven subtropical rivers. We applied redundancy analysis and variance partitioning to reveal the pure and shared effects of the three groups of factors on community variation. Environmental filtering, mass effects and dispersal limitation were all significant mechanisms affecting variation in macroinvertebrate communities, but their relative importance depended on biological traits. Environmental filtering explained more of the variation in the whole metacommunity, tolerant taxa and macroinvertebrate groups with weak dispersal ability (i.e., aquatic dispersal, aerial passive dispersal and large body size). In contrast, mass effects accounted for more variation in the communities of intolerant taxa and macroinvertebrate groups with strong dispersal ability (i.e., aerial active dispersal mode and medium body size). Dispersal limitation was more influential for sub-communities of moderately tolerant taxa and large-sized taxa. Our study highlights that simultaneously accounting for different spatial processes and using a trait-based approach are essential to improve our understanding of community assembly in river networks.

Hitherto, 24 species of the Glyphiulus javanicus group have been recorded, all endemic to Southeast Asia, including 14 in China. Nevertheless, this species group needs further exploration. In this context, four new species of this group are described, all collected from limestone caves in Southern China: G. calceus sp. n., G. foetidus sp. n., G. guangnanensis sp. n., and G. impletus sp. n. They can be separated easily from each other and other congeners by their carinotaxic formulae, the structures of male legs I, and the gonopods. Due to the absence of any troglomorphic traits in our specimens, they may be troglophilic only.

Benthic algae, especially diatoms, are commonly used to assess water quality in rivers. However, algal-based assessments are challenging at the river system scale because longitudinal variation in physical habitat conditions may obscure algal responses to changes in water quality. In the present study, we surveyed benthic diatoms and environmental variables from a mountainous Chinese river system. Hierarchical clustering, discrimination analysis, and indicator species analysis were used together to explore associations between distribution patterns of diatom assemblages and water quality variables. Study sites were clustered into five groups based on their diatom community composition, with sites grouped by the sampling months. Chemical oxygen demand (COD), elevation, and total nitrogen (TN) were the most important predictors for site classification. Site groups with higher elevations had higher TN concentrations; however, COD concentrations were higher in lower elevation groups. Moreover, COD concentrations significantly differed between temporally separated groups. In total, 49 indicator species were identified for individual groups, with most taxa indicating the eutrophic condition. Additionally, we found that European diatom indices are not closely associated with water quality variables. We conclude that the identification of algal patterns and their driving forces can provide valuable information to aid bioassessment at the river system scale.

Aim: Disentangling the drivers of community assembly and species diversity in space and time is critical to elucidating metacommunity theory. However, our understanding of how metacommunity structuring will change over time remains insufficient, especially in rivers in the monsoon climate zone. We examined whether (1) the idealized metacommunity structure is different among seasons and (2) the relative importance of underlying mechanisms on community assembly varies within and across tributaries as well as among seasons. Location: Five tributaries in the Hanjiang River Basin. Taxon: Macroinvertebrates. Methods: Benthic macroinvertebrates and environmental data were collected seasonally (i.e. spring, summer, autumn and winter) from the same 70 sampling sites. The elements of metacommunity structure (EMS) framework was employed to identify which idealized topology best characterizes the actual metacommunity. Redundancy analysis and variance partitioning procedures were applied to determine key environmental and spatial factors and to examine their relative contributions to variation in community structure in different seasons. Results: The best-fit metacommunity typologies were consistent over time, with metacommunity structure in each season displaying Clementsian gradients, characterized by high degrees of coherence and turnover, and positive boundary clumping. Environmental control prevailed over spatial processes in structuring macroinvertebrate communities, but their relative influence on community variation was context-dependent. Particularly, environmental filtering was the predominant mechanism at the intermediate spatial scale. However, spatial processes had gradually stronger effects at smaller and larger extents. Main conclusions: Both EMS analysis and the variance partitioning approach suggested environmental filtering was the principal structuring processes for macroinvertebrate assemblages throughout the year, although mass effects and dispersal limitation also played significant roles at smaller and larger spatial extents respectively. Considering that the most influential environmental factors shaping macroinvertebrate communities were variable across seasons, we argue that spatio-temporal investigations would provide more information on community assembly than single snapshot studies. [ABSTRACT FROM AUTHOR]

Understanding how environmental changes affect life-history traits is important for predicting population dynamics of a species. As one of the most pervasive forms of environmental changes in freshwater systems, eutrophication can change life-history traits of freshwater animals through density-dependent/independent processes. However, empirical evidence remains scarce regarding the mechanisms by which eutrophication influences life-history traits. We conducted a field study linking eutrophication, life-history traits and population density in a population of Margarya melanioides in Lake Dianchi, the largest lake of the Yun-Gui plateau in China and the most eutrophicated by humans, over 14 months in 2009-2010. We estimated key life-history traits (growth and reproduction) of M. melanioides in 2009-2010. Then, by comparing some life-history traits with those recorded in 1931-1933 (when the extent of eutrophication was comparatively low), we found that this snail had increased its fecundity (from 1.07 to 4.24 offspring/brood-bearing female) and the proportion of females with broods (23.6 to 77.4%), decreased its body size (54.2 to 47.6mm) and the threshold size for reproduction (46 to 35mm), and distorted its female/male sex ratio (1.6:1 to 0.97:1). These findings suggest that M. melanioides has adapted some life-history traits in response to intensified eutrophication. A structural equation model indicated that eutrophication influenced the reproduction of this snail through two related but opposing pathways: primarily by decreasing its population size to reduce its reproduction and secondarily by directly promoting its reproduction. Our results not only support the significance of eutrophication in determination of life-history traits of freshwater animals, but also suggest that density-dependent effects on reproduction may be stronger than direct environmental influences when population size is small. [ABSTRACT FROM AUTHOR]

A new enchytraeid species, Mesenchytraeus asymmetriauritus sp. nov., collected from terrestrial habitats of Changbai Mountain in the northeast China, is described. It is characterized by the dorsal vessel originating in XV–XVII, four pairs of preclitellar nephridia in 6/7–9/10, spermathecae attached to oesophagus in segment V and each possessing three or four ear-shaped diverticula of different size, one pair of asymmetrical sperm sacs occupying X–XVII and containing bulk of naked sperm bundles, atrium cylindrical with 4 prostate-like glands and distinct from vas deferens, and well-developed egg sac extending to XVI–XVII. [ABSTRACT FROM AUTHOR]

Mesenchytraeus monodiverticulus, new species, (Clitellata: Enchytraeidae) is described based on live and preserved specimens from Changbai Mountain. It is diagnosed by possessing enlarged ventral chaetae in V-VI (4--5 per bundle), nephridium holding solid unlobed postseptale, spermathecae possessing only one diverticulum and attached entally to esophagus in VII, atria cylindrical without prostate glands, and the presence of regular spermatozoal bundles in seminal vesicle (XI-XIII) with the heads of spermatozoa arranged in both ends orderly. The major differences between M. monodiverticulus and its congeners are discussed. A key to species of Mesenchytraeus that possess enlarged chaetae is provided. [ABSTRACT FROM AUTHOR]

Mesenchytraeus megachaetus, new species, is described from northeast China. It is characterized by possessing enlarged ventral chaetae in segments V-VI (3-4 per bundle); nephridia with solid unlobed postseptale, relatively developed interstitial tissue and near-septal origin of the efferent duct; nephridia occurring in 5 pairs in preclitellar region; seminal vesicle absent, replaced by 5-8 naked "spermatozeugmata" in dorsal region of XI; spermathecae without diverticula and attached entally to esophagus in segment VI; atria tubular (indistinct from vasa deferentia) and without prostate glands; egg sac much developed (extending to XVII- XVIII). [ABSTRACT FROM AUTHOR]

We describe one new enchytraeid species, Fridericia liangi sp. nov., from Mt. Changbaishan, Jilin Province, northeastern China. It was collected from soils at the foot of Changbaishan Mountain and is distinguished from all known congeners by the following combination of characters: 1) no lateral chaetae, only ventral chaetae throughout, 2) a maximum of four chaetae in ventral preclitellar bundles, 3) one chaeta in ventral postclitellar bundles, 4) dorsal pores from VII on, 5) esophageal appendages unbranched, 6) coelomocytes without refractile vesicles, 7) clitellum girdle shaped, well developed, 8) no subneural glands, and 9) spermathecae simple. [ABSTRACT FROM AUTHOR]

Piguetiella denticulata Liang & Xie, 1997 is redescribed based on the type series collected from the type locality, Songtao River, and streams of the Zhangjiajie Mountain in southwestern China, and specimens from several tributaries of the Yangtze River. This species is characterized by a large body size, the absence of eyespots and dorsal hair chaetae, the same size and shape of dorsal and ventral chaetae, the presence of 3-4 intermediate teeth on both ventral and dorsal chaetae, and an intestinal dilation in IX-X segments. The essential characteristics used to diagnose the genus are discussed and a key to the genus is provided. [ABSTRACT FROM AUTHOR]

Fridericia dianchiensis, a new enchytraeid species collected from Yunnan Province, is described here. It is characterized by a combination of the following characters: 1) lateral bundles containing maximum 3 chaetae; 2) esophageal appendages with 3-4 simple, terminal branches; 3) dorsal vessel originating in XX-XXIII; 4) subneural glands absent; 5) seminal vesicle large, occupying two segments; 6) clitellum girdle-shaped or gland cells absent between bursal slits and pre-middle ventrally; 7) coelomocytes without refractile vesicles; 8) spermatheca without diverticula and both ampullae broadly united; and 9) long spermathecal ectal duct without gland at the orifice. [ABSTRACT FROM AUTHOR]

The assemblage of oligochaetes in the Liangzi Lake District, located in middle reaches of the Changjiang River, was studied from May to August, 2001. To establish species composition, richness, and abundance and detect the influence of environmental variables on oligochaete distributional patterns, 45 localities were sampled. All total, 20 species belonging to the families Naididae (eight species), Tubificidae (11 species), and Lumbriculidae (one species) were found. Branchiura sowerbyi, Tubifex sp. I, and Aulodrilus pluriseta were the dominant species and contributed nearly 70% of the total abundance. The 45 sampling sites were separated into three groups based on composition and relative abundance of benthic oligochaete communities using two-way indictor species analysis associated with detrended correspondence analysis. Canonical correspondence analysis indicated that two plant variables (total plant cover and total submersed macrophyte biomass) were strongly correlated with the faunal gradient (p<0.05). Other predicator variables were water depth and total nitrogen. [ABSTRACT FROM AUTHOR]

Sedimentation variables and benthic community data were collected at seven stations during four seasons in Xiangxi Bay of the Three Gorges Reservoir, China. Summer, the season of highest discharge into the reservoir, was characterized by the extreme sediment loading. The benthic macroinvertebrate community was dominated by oligochaetes across all seasons at most stations. In winter/spring, macroinvertebrate density and richness increased. Correspondence analysis showed that community structure differed among stations at the two ends of the bay in winter and among almost all stations in spring. However, no variable associated with sedimentation appeared to be associated with differences in the community. [ABSTRACT FROM AUTHOR]

Nais inflata Liang 1963 is redescribed on the basis of fully mature specimens collected from several localities of the Yangtze River and Yellow River. The observations and redescription resulting from the study of mature specimens supports N. inflata as a valid species. This species is characterized by a thickened body, the ventral crotchets all of the same type with distal tooth usually longer than proximal one, a greater number of dorsal chaetae per bundle, stout dorsal needles with equal minute bifid teeth (<1 µm), presence of penial chaetae, and prostate glands on vasa deferentia instead of atria. The species is most closely related to N. communis Piguet, 1906 and N. variabilis Piguet, 1906. A table comparing allied species is provided. [ABSTRACT FROM AUTHOR]

We examined the effect of different plant architecture types on epiphytic macroinvertebrates of a shallow macrophyte-dominated lake in China. Macroinvertebrates were sampled from four dominant submersed macrophytes in the lake - two dissected plants (Myriophyllum spicatum L. and Ceratophyllum demersum L.) and two undissected plants (Potamogeton maackianus A. Benn. and Vallisneria spiralis L.). Macroinvertebrate richness showed significant differences among four submersed macrophyte habitats, and higher density per g of dry plant were associated with dissected plants than undissected plants. The average abundance in dissected plants was as three-six times as in undissected plants. The biodiversity of epiphytic macroinvertebrates was higher in dissected plants than undissected plants. Our results suggest that dissected plants provide different habitat for macroinvertebrates than dissected plant, and this concurs with the hypothesis that the former could support more epiphytic macroinvertebrates than the latter. [ABSTRACT FROM AUTHOR]

Surveys of macroinvertebrates were carried out in the Xiangxi River system during July of 2001. Among the 121 taxa collected, Ephemeroptera, Trichoptera, and Diptera dominated (41.7, 26.0, and 24.5% of the total relative abundance, respectively). Two-way indictor species analysis and detrended correspondence analysis divided the 49 sites into four groups based on species composition and relative abundance. Canonical correspondence analysis indicated that elevation, SiO2, pH, conductivity, hardness, and NO2-N were significant environmental factors affecting the distribution of macroinvertebrates. [ABSTRACT FROM AUTHOR]

From June 2000 to June 2002, four sites on the mainstem of the Xiangxi River and one site on each of its major tributaries were sampled 16 times each for benthic algae. All total, 223 taxa (most to species and variety levels) were found (193 Bacillariophyta, 20 Chlorophyta, nine Cyanophyta and one Xanthophyta). The diatoms Cocconeis placentula, Achnanthes linearis, and Diatoma vulgate dominated the system, with relative abundance of 33.3%, 18.8%, and 6.4%, respectively. The abundances of all the other taxa were under 5%, and 210 taxa collectively contributed less than 1% of the total abundance. Taxa diversity peaked in winter and reached a minimum in summer. Species richness varied considerably but was not significantly different over time. Maximum algal density occurred in later winter/spring (1.4 x 109 ind./m²) but was not significantly different from the minimum density, which occurred in August. Chlorophyll a showed similar seasonal fluctuation but also was not significantly different over time. Canonical correspondence analysis demonstrated that water hardness, depth, conductivity, and alkalinity had important influences on variation of epilithic algae in the Xiangxi River system. [ABSTRACT FROM AUTHOR]

Identifies the structure of marozoobenthos of the East Dongting Nature Reserve system in China. Relationships between the macrozoobenthos and environmental factors using multivariate analyses; Differences in macrozoobenthos abundance; Percentage of environmental factors that is accounted for the total variance of the macrozoobenthos data set in the reserve system.

Presents a study that investigated the spatial pattern of epilithic algae in Xiangxi River, China. Information on the number and kinds of algae taxa observed in the study; List of environmental factors affecting the distribution of algae communities; Effect of the dominance of diatoms in the river.

Investigates species of terrestrial and aquatic Enchytraeidae collected from southeastern China. Information about several species investigated by scientists.

Benthic macroinvertebrates were assessed monthly in Xiangxi Bay of the Three Gorges Reservoir for two years after the initial closure of the dam. Mean total density of macroinvertebrates varied from 275 ind./m2 during the first year to 5,094 ind./m2 during the second year, and the community of 50 taxa was overwhelmingly dominated by oligochaetes and chironomids (44 and 48% of the total taxa, respectively). As sediment accumulated in the substrate of the bay, the species composition changed dramatically, with oligochaetes comprising 91.3-99.3% of the total abundance during the second year. The dominant oligochaetes were Limnodrilus hoffmeisteri and Nais inflata. The chironomids Procladius sp., and Polypedilum scalaenum group sp. were similarly abundant in both years. [ABSTRACT FROM AUTHOR]