Xiaodong Qu

Benthic algae of the Xiangxi River, China

ABSTRACT 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 vulgare 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 winterlspring (1.4x109 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.

Distribution of the Macroinvertebrate Communities in the Xiangxi River System and Relationships with Environmental Factors

ABSTRACT 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.

Spatial distribution of benthic algae in the Gangqu River, Shangrila, China

This study consisted of sampling benthic algae at 32 sites in the Gangqu River, an important upstream tributary of the Yangtze River. Our aims were to characterize the benthic algae communities and relationships with environmental variables. Among the 162 taxa observed, Achnanthes linearis and Achnanthes lanceolata var. elliptica were the dominant species (17.10% and 14.30% of the total relative abundance, respectively). Major gradients and principal patterns of variation within the environmental variables were detected by principal component analysis (PCA). Then non-metric multidimensional scaling (NMS) divided all the sites into three groups, which were validated by multi-response permutation procedures (MRPP). Canonical correspondence analysis (CCA) indicated that three environmental variables (TN, TDS, and TP) significantly affected the distribution of benthic algae. Weighted averaging regression and cross-calibration produced strong models for predicting TN and TDS concentration, which enabled selection of algae taxa as potentially sensitive indicators of certain TN and TDS levels: for TN, Achnanthes lanceolata, Achnanthes lanceolata var. elliptica, and Cymbella ventricosa var. semicircularis; for TDS, Cocconeis placentula, Cymbella alpina var. minuta, and Fragilaria virescens. The present study represents an early step in establishing baseline conditions. Further monitoring is suggested to gain a better understanding of this region.

Macroinvertebrate relationships with water temperature and water flow in subtropical monsoon streams of Central China: implications for climate change

Effects of global climate change on freshwaters are still poorly known, particularly in systems where they interact with other environmental variables. Using data from a subtropical monsoon stream in Central China, we assessed the relationships between a macroinvertebrate community and variations in temperature and water flow. We then used these data to assess potential changes under different climate change scenarios. Winter macroinvertebrate abundance and richness decreased with increasing water temperature during the last six years. However, effects of climate on biotic metrics in summer were less clear. Partially constrained ordination revealed that variations in community composition could not be explained clearly by individual climatic variables, but total dissolved solids and total nitrogen were more important. Over the period 1978-2008, average annual air temperature in the study area increased by 0.6 degrees C, whereas total annual water flow declined. Projections suggest that further winter warming of 1 degrees C could decrease the macroinvertebrate abundance and richness by 11.1 % and 6.0 %, respectively. One unit increase in the smoothed sea surface temperature (SSST) during winter could increase the abundance and richness by 38.2 % and 21.1 %, respectively. With further global change effects likely in future, our data highlight the importance of the conservation of mountainous streams in the upper Yangtze River.

Influence of Environmental Variables on Macroinvertebrates in a Macrophyte-Dominated Chinese Lake, with Emphasis on the Relationships between Macrophyte Heterogeneity and Macroinvertebrate Patterns

ABSTRACT The benthic community structure in Baoan Lake was examined in relation to lake water physicochemical characteristics and biological parameters. Seventy macroinvertebrate taxa were identified, and mollusks constituted the dominant group and accounted for more than 80% of the total abundance. Assemblages were composed mainly of scrapers (81.5%) and collector-gatherers (roughly 10%). Three plant variables (richness, total cover, and total biomass) were strongly correlated with the faunal gradient (p<0.05). Other predicator variables were C1−, SiO2, and chemical oxygen demand. Because of the importance of macrophytes in structuring benthic assemblage in this lentic system, the spatial heterogeneity of macrophytes also influenced the pattern of macroinvertebrates. Seven lake regions were uniquely characterized according to primary macrophyte composition and biomass. There were significant differences for macroinvertebrate taxa richness, abundance, and biodiversity among the seven macrophyte regions.

Inter-annual patterns in the stability and persistence of stream macroinvertebrate communities: relationship with water physicochemical parameters

The relationships between temporal patterns of macroinvertebrate community and water physicochemical parameters were investigated in the Xiangxi River, which is the largest tributary to the Three Gorges Reservoir (TGR) in Hubei province, China. The construction of the TGR has strongly impacted the Xiangxi River watershed, but inter-annual patterns in stream macroinvertebrate communities have not been examined. We sampled water and macroinvertebrates monthly from 2004 to 2006. We assessed the persistence (similarity between years of species assemblage) and stability (similarity between years with respect to relative abundance of species in the community) of the macroinvertebrate community by the Bray–Curtis distance. The relationship between changes in water physicochemical conditions and changes in community structure were assessed with linear regression. The results showed that both the physical and chemical conditions of the water differed significantly among years. Similarly, the macroinvertebrate community structure and composition were significantly different among years. The compositional persistence was positively and significantly related to the physical condition, supporting the Habitat Templet Theory and indicating the importance of physical habitat protection. This study provides information for environmental assessment, which can be used to develop sustainable management strategies.

Benthic Algae of the Gangqu River, Shangrila, China

ABSTRACT We surveyed the benthic algae at 32 sites in the Gangqu River system during May 2005. Among the 162 different taxa observed, 88.8% were diatoms. Achnanthes linearis and Achnanthes lanceolata var. elliptica were the dominant species, comprising 17.1% and 14.3% of the total relative abundance, respectively.