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Dramatic environmental changes and species invasions are increasingly threatening the diverse fish fauna of the Yellow River, China. This study examines temporal changes in the alpha and beta components of fish taxonomic, functional and phylogenetic diversity in relation to anthropogenic environmental changes over the past 50 years. We hypothesized that temporal trends in multifaceted components of diversity would be highly congruent, but that the relative importance of anthropogenic disturbances would differ in shaping spatial patterns of fish diversity. We found that all three components of alpha diversity increased over time but at different rates (19.1%, 21.3% and 15.3% for taxonomic, functional and phylogenetic diversity, respectively). Fish faunas of the Yellow River have also become homogenized over time, but this was much greater for functional and phylogenetic components of beta diversity than for taxonomic diversity (change in beta diversity = − 0.11, − 0.24 and − 0.02, respectively). Temporal changes in alpha and beta diversity were strongly related to invasion of non-native fish species and changes in temperature, sediment load, reservoir capacity and aquaculture area. Our results underscore the ongoing need for threat mitigation (particularly relating to dams and aquaculture) to conserve the unique biodiversity of one of the world's largest rivers. [ABSTRACT FROM AUTHOR]

Epilithic algal community structure and function are important indicators of stream ecosystem health and are sensitive to ambient environmental changes. In this study, we examined the impact of light and nutrients on epilithic algal community structure and function by an in situ nutrient addition and shaded canopy experiment in subtropical streams in China. Epilithic algae structure, dominated by diatoms, was significantly different with nutrient addition and light reduction. Nutrient addition increased the epilithic algae and diatom density, colonial life-forms, planktonic diatoms, and high-profile diatoms but decreased the low-profile diatoms. The shaded canopy increased the low-profile diatoms but decreased the adnate life-forms, planktonic diatoms, and high-profile diatoms. Epilithic metabolism, including gross primary production (GPP), net daily metabolism (NDM), and production/respiration (P/R) increased with nutrient addition, while respiration (R) only increased when the canopy was open with nutrient addition. Epilithic GPP had a significant positive correlation with diatom density (P < 0.01, R2 = 0.9425). Our results indicated that changes in epilithic algae structure due to changes in riparian canopy coverage and nutrients could affect epilithic algal community function. Quantifying the impacts of such drivers on community structure and function is vital to effective river management. [ABSTRACT FROM AUTHOR]

The river discontinuity caused by damming can modify both the availability of production sources and the energy flow in riverine food webs. We hypothesized the carbon source support food web would vary among the reaches in response to changing in hydrogeomorphic conditions, and this variability further caused food web structure changes. To test our hypothesis, three different river reaches in the lower Jinsha River, China, were selected and the stable isotope ratios of basal sources and dominant consumers were analyzed in three seasons 2015. The relative importance of basal sources showed temporal and spatial difference to varying degrees. Seston were the most important carbon sources in supporting all consumers and the contributions increased from upstream to downstream. Riparian C3 plants played an important supplementary role in both reaches above the dam or only in the high flow period. Dam-induced flow alteration changed the trophic basis and the composition of food webs, resulting in a difference in the food web structures, and widening but with lowest complexity food web occurred in the downstream reach. The results further confirm that the differences in the hydrogeomorphologic conditions caused by dam construction can exert potential influence on riverine food web structures. [ABSTRACT FROM AUTHOR]

Pachychilid snails are common and widespread in tropical Asian streams, and given their abundance, these heavy-shelled prosobranchs may serve as a 'trophic dead-end' preventing energy transfer to higher trophic levels. Sulcospira hainanensis (Bröt, 1872) is an abundant secondary consumer in Hong Kong streams, and tends to have higher standing biomass in less shaded sites. We predicted that S. hainanensis would be more productive in unshaded streams, where snails have a higher assimilation of more nutritious algal carbon. The production and population dynamics of S. hainanensis were studied along a gradient of shading in four Hong Kong streams. The increment-summation method was considered to most realistically represent snail production, which ranged from 1,612.8 to 6,123.9 mg ash-free dry mass m year; these estimates were among the upper range of values reported for stream prosobranchs. Production, turnover, and growth were higher in unshaded streams, where the combined effects of higher light input and nutrient concentrations likely enhanced the supply of algal food. Despite high standing biomass (26% of total benthic fauna), S. hainanensis had a relatively low (~16%) contribution to total production in one site, suggesting that it is not a major trophic dead-end in the food webs of tropical Hong Kong streams. [ABSTRACT FROM AUTHOR]

We studied the effects of flow reduction on epibenthic algal assemblages by comparing up- and down-stream reaches of ten Hong Kong streams subject to different degrees of water abstraction during 2007-2008. Downstream discharge declined by 71 and 54% during the wet and dry seasons, respectively. Algal responses varied seasonally and according to morphological guild and reflecting reductions in discharge and current velocity, or changes in total nitrogen and phosphate, or their combined effects. Significant inter-reach assemblage differences were observed during the both seasons, but wet-season assemblage structure was not directly influenced by any flow-related variable. During the dry season, scouring-tolerant prostrate/adnate diatoms (especially Achnanthes, Cocconeis) were relatively abundant upstream, whereas intolerant stalked ( Eunotia, Gomphonema) and mobile diatoms were more numerous downstream. Both low- and high-profile (erect diatoms, Chamaesiphon, Calothrix) guilds were sensitive to changes in nutrients. Low-flow conditions downstream, surprisingly, enhanced algal diversity, and richness. Based on the linear response of Cocconeis (mainly C. placentula) to discharge reduction, we recommend that >65% of dry-season discharge should be maintained in downstream reaches in order to sustain near-natural algal assemblages; 32% of discharge is required to avoid substantial alterations in assemblage structure. [ABSTRACT FROM AUTHOR]

The impacts of watershed urbanization on streams have been studied worldwide, but are rare in China. We examined relationships among watershed land uses and stream physicochemical and biological attributes, impacts of urbanization on overall stream conditions, and the response pattern of macroinvertebrate assemblage metrics to the percent of impervious area (PIA) of watersheds in the middle section of the Qiantang River, Zhejiang Province, China. Environmental variables and benthic macroinvertebrates of 60 stream sites with varied levels of watershed urban land use were sampled in April, 2010. Spearman correlation analysis showed watershed urbanization levels significantly correlated with increased stream depth, width, and values of conductivity, total nitrogen, ammonia, phosphate, calcium, magnesium, and chemical oxygen demand for the study streams. There was significant difference in total taxa richness, Empheroptera, Plecoptera, and Trichoptera (EPT) taxa richness, and Diptera taxa richness, percentages of individual abundances of EPT, Chironomidae, shredders, filterers, and scrapers, and Shannon-Wiener diversity index between reference streams and urban impacted streams. In contrast, percentages of individual abundances for collectors, oligochaeta, and tolerant taxa, and biotic index were significantly higher in urban impacted than reference streams. All the above metrics were significantly correlated with PIA. The response patterns of total taxa richness, EPT taxa richness, and Shannon-Wiener diversity index followed a drastic decrease at thresholds of 3.6, 3.7, and 5.5% of PIA, respectively. Our findings indicate that stream benthic macroinvertebrate metrics are effective indicators of impacts of watershed urban development, and the PIA-imperviousness thresholds we identified could potentially be used for setting benchmarks for watershed development planning and for prioritizing high valued stream systems for protection and rehabilitation. [ABSTRACT FROM AUTHOR]

Taxonomic patterns of protozoan community structure for monitoring water quality were studied from May to September 2003 in Songhua River, northeast China. Protozoan communities were sampled monthly using PFU (polyurethane foam unit) method at the four stations with different pollution/eutrophication levels. Physical–chemical parameters (e.g., water temperature, dissolved oxygen (DO), pH, biological oxygen demand (BOD5), chemical oxygen demand (COD), ammonium nitrogen (NH4-N), and nitrate nitrogen (NO3-N) were measured synchronously for comparison with biotic parameters. A total of 53 protozoan taxa with nine common species were identified comprising 33 ciliates, 17 flagellates, 3 sarcodines. Multivariate analyses demonstrated that the spatial taxonomic patterns of protozoan communities significantly correlated with environmental conditions, especially related to the concentrations of COD, BOD5, NO3-N, and NH4-N, either alone or in combination with one another. Although species richness was found to be independent of physical–chemical parameters, the average taxonomic distinctness (Δ+) were positively significantly correlated with the concentration of dissolved oxygen and NO3-N, but negatively with COD and BOD5. It is suggested that spatial pattern of protozoan communities and taxonomic biodiversity can be used in assessing water quality of flowing river systems. [ABSTRACT FROM AUTHOR]

Six geographic samples of Cyclina sinensis were collected from the coast along China and analyzed to reveal morphological and genetic variation by using nine allozyme loci and 11 morphological variables. The discriminant function analysis (DFA) of morphology suggested a clear separation between the southern and northern populations. Polymorphism was detected at nine loci across all six populations. The mean allele number ranged from 2.44 to 2.78, and the mean observed heterozygosity ranged from 0.218 to 0.296. High level of genetic differentiation was found between three northern populations and three southern populations. The marked genetic differentiation can be explained by the upwelling of the Zhejiang province and the freshwater outflow of Yangtze River. The results obtained in this study indicate that the northern and southern populations of C. sinensis should be treated as separate units for conservation management. [ABSTRACT FROM AUTHOR]

Changes in the total phenolics, condensed tannins (CT), protein-precipitable phenolics content and protein precipitation capacity were determined on mangrove leaves representing a range of maturation and senescence in the Jiulong River Estuary, Fujian, China. The results showed that the total phenolics, extractable condensed tannins, total condensed tannins, protein-precipitable phenolics content and protein precipitation capacity in young leaves were higher than those in mature and senescent leaves. With leaf maturation and senescence, total pehnolics decreased. The rapid loss of phenolics observed following senescence and abscission can be ascribed to leaching and degradation. Protein-bound CT and fibre-bound CT tended to increase with leaf maturity, and decreased with senescence. Protein-bound CT and fibre-bound CT increased with leaf decomposition, with CT binding more strongly to protein than to fibre. The increases in nitrogen contents and ash free caloric values, and declines in total phenolics and total condensed tannins of mangrove leaf litter suggests that partially decomposed mangrove detritus is a palatable heterotrophic substrate, and thus may be an important source of matter and energy for the estuarine food web. [ABSTRACT FROM AUTHOR]

The occurrences of harmful algal blooms (HABs), in terms of frequency and area in the Chinese coastal waters, have been increasing since 1980s and caused considerable economic losses. In the present study, we have analyzed spatial and seasonal characteristics of HAB events in the southern Yellow Sea and East China Sea along Chinese coast from 1933 to 2004. With a total 435 HAB records, the most frequent HAB occurrence area (FHA) is off the Yangtze River mouth and another two FHA areas are located south of the Yangtze River estuary along about isobaths of 30–60 m coastal water in the East China Sea. The time of HAB occurrence shifted during our study period: from autumn (August–October) before 1980s to July–August in 1980s, during May–July in 1990s, and May–June for the period of 2000–2004. Causative species were found to be different: Noctiluca scintillans and Skeletonema costatum were dominant causative species prior to 2000; and Prorocentrum donghaiense Lu was dominant from 2000 to 2004 and also caused large blooms in May. Trichodesmium sp. caused many HABs in autumn (August–October) prior to 1980s with only one HAB between 1980 and 2004. The changes of the dominant HAB species may have affected the timings of HAB occurrence, as well as the increasing HAB-affected areas in recent years. [ABSTRACT FROM AUTHOR]

Six polymorphic microsatellites (eight loci) were used to study the genetic diversity and population structure of common carp from Dongting Lake (DTC), Poyang Lake (PYC), and the Yangtze River (YZC) in China. The gene diversity was high among populations with values close to 1. The number of alleles per locus ranged from 2 to 11, and the average number of alleles among 3 populations ranged from 6.5 to 7.9. The mean observed ( H O) and expected ( H E) heterozygosity ranged from 0.4888 to 0.5162 and from 0.7679 to 0.7708, respectively. Significant deviations from Hardy–Weinberg Equilibrium expectation were found at majority of the loci and in all three populations in which heterozygote deficits were apparent. The analysis of molecular variance (AMOVA) indicated that the percent of variance among populations and within populations were 3.03 and 96.97, respectively. The Fst values between populations indicated that there were significant genetic differentiations for the common carp populations from the Yangtze River and two largest Chinese freshwater lakes. The factors that may result in genetic divergence and significant reduction of the observed heterozygosity were discussed. [ABSTRACT FROM AUTHOR]

Rhinogobiois a cyprinid genus restricted to the river drainages of China. Sequences of the mitochondrial DNA control region were determined for fourRhinogobiospecies and one outgroup species,Coreius heterodon, to investigate the phylogenetic relationships within the genus. The control region of theRhinogobiospecies ranges from 922 to 930 base pairs and comprises 930 base pairs inCoreius. Our phylogenetic analysis indicates two distinct lineages in the genusRhinogobio. The first includes onlyRR.ventralis. In the second lineage there are three species, two closely related speciesR.cylindricusandR.hunanensis, and their sister speciesR.typus. An analysis of character adaptations suggests an evolutionary trend in this genus towards a relatively lower body and caudal peduncle depth, a shorter dorsal fin, and a more anterior anus. In addition, there is a trend towards shorter barbels and relatively larger eyes. Some or all of these traits may be associated with a habitat shift from fast-flowing turbid rivers to slower-flowing clear river habitats. [ABSTRACT FROM AUTHOR]

Describes the species of Eumonhystera huruii and Monhystera somerini from Li River in China. Morphological and morphometrical characteristics of E. huruii; Description of the female reproductive system of M. somerini; Composition of the buccal cavity of Monhystera.