Cai Qinghua

Dynamics of main nutrient input to Xiangxi Bay of the Three-Gorges Reservoir

Abstract Based on routine monitoring data in Xiangxi River and its main tributary Gaolan River from September 2000 to June 2005, this paper estimates the contribution of riverine nutrients, and analyzes the monthly dynamics of concentrations and fluxes of nutrients. The results show that Xiangxi Bay annually receives 1623.49 tons of total nitrogen (TN) and 331.85 tons of total phosphorus; Xiangxi River alone accounts for 68.50% of the total nitrogen fluxes and 91.74% of the total phosphorus fluxes. In these two rivers, dissolved inorganic nitrogen (DIN) is the dominating form of nitrogen; fluxes of DIN and TN are high during summer (July), mid-spring and autumn, and relatively low in winter; non-point source pollutants that flow into rivers are the most important pathway of nitrogen. Orthophosphate is the dominating form of phosphorus in Xiangxi River, relatively low in Gaolan River; fluxes of phosphorus are high during summer and late spring, relatively low during winter and late autumn in Gaolan River, but fluctuate irregularly in Xiangxi River; phosphorus in Gaolan River is mainly caused by non-point source pollutants, while point source pollutants of phosphorus play an important role in Xiangxi River. Soil erosion probably represents the major way of non-point source pollutants, while the drainages of phosphorus diggings and factory discharges play the most important role in the point source pollutants of phosphorus. This research suggests that measures must be taken to control the point source pollutants of phosphorus in Xiangxi River in order to protect Xiangxi Bay of the Three-Gorges Reservoir.

Impacts of small hydropower plants on macroinvertebrate communities

Abstract The influence of small hydropower plants (SHPs) on the spatial distribution of macroinvertebrate assemblages was investigated in 5 cascade SHPs along the Xiangxi River in October 2005. 5 sites were sampled at each SHP. A total of 4656 macroinvertebrates belonging to 69 genera were collected. The characteristics of macroinvertebrate community structures were analyzed by using richness, abundance, dominant species and functional feeding groups. The results suggested that construction of SHPs had no significant impact on water chemistry, but on physical variables (such as current velocity and water depth) which varied significantly among the 5 sites. All the characteristics of the macroinvertebrate community were more or less affected by the construction, especially by the abundance, filter-collector percentage, predator percentage, and the stations. The results also suggested that the sites beneath the dam had the most different community structures, indicating that diverting the water current completely is harmful to the protection of macroinvertebrate diversity of the river.

Monthly change of community structure of zoobenthos in Xiangxi Bay after impoundment of the Three Gorges Teservoir, China

Xiangxi Bay, a typical bay of the Three Gorges Reservoir (TGR) in China, was formed in June 2003 after the impoundment of the TGR. We investigated the community structure of zoobenthos in Xiangxi Bay from August 2003 to August 2004. Benthic abundance and biomass were calculated per unit area of sediment. A total of 26 taxa were identified. They included two families of Lamellibranchia (7.7% of the total taxa number), two families of Oligochaeta (50%), Chironomidae (38.5%), and one other animal (3.8%). The average density and biomass were 276 ind./m2 and 0.301 g/m2, respectively. Oligochaetes and chironomids constituted the major groups, and Limnodrilus hoffmeisteri, Procladius sp., Branchiura sowerbyi, Tubificidae sp1. and Polypedilum scalaenum group sp. were the common taxa in this reservoir system. Among them, L. hoffmeisteri and Procladius sp. were the dominant species, and contributed 37.0% and 28.3% of the total density, respectively. The standing crop of zoobenthos in Xiangxi Bay was relative low, compared with other similar reservoirs. Our studies demonstrate that the standing crop increased gradually with time. The total density and biomass in August 2004 were 8.8 and 14.3 times those of the initial impoundment, separately. Oligochaetes did not become the sole dominant group, indicating that the sediment loading in Xiangxi Bay may be not serious.

Spacial distributional pattern of macrozoobenthos and pollution evaluation in East Lake Dongting Reserve

Investigation of macrozoobenthos was carried out in East Lake Dongting Reserves in September, 2001. All total, 51 taxa were identified from thirty-two sampling sites, of which, 48 oligchaetes, 15 mollusks, 14 insects and 4 other forms. Mollusks constituted the most dominant group and accounted for more than 70% of the total abundance. Among which, four gastropods, Alocinma longicornis, Bellamya aeraginosa, Parafossarulus sinensis, P. striatulus and one oligochaete Branchiura sowerbyi were the dominant species. The richness and three biodiversity index values ((Margalef, Simpson and Shannon) per site were 6.3, 1.38, 4.05 and 1.47, respectively. Assemblages were composed mainly of scrapers (66.7%) and collector-gatherers (19.9%). and to a lesser extent to other functional feeding groups.The investigation data were compiled and a GIS database of macrozoobenthos was established. A vector boundary map of the lake was digitized and georeferenced, then used to introduce sampling sites. Under the support of GIS software Areview 3.2 and the relative extension modules (Spatial Analyst Extension 2.0 and Kringing Interpolator Extension 3.22 SA), the GIS database was employed to simulate spacial distribution patterns of parameters of macrozoobenthos and Hilsenhoff biotic index (BI). The simulation process was based on the principle of Kringing interpolation technique. The simulated results were stored as Areview Grid format with a grid precision of 20 m. The higher distributional pattern of main groups and five dominated species were overlapped based on the 2-4 times as mean abundance, and the 16 physical-chemical parameters were collected in these higher distributional regions.The simulated patterns of macrozoobenthos showed that these patterns were relatively high spatial heterogeneity, and distributions of most parameters of macrozoobenthos had usually 2-4 high value distributed zones in the whole lake. The oligochaete pattern showed basically no overlapping with two other groups, and mainly distributed in deeper region. ANOVA detected water depth was the key factor influencing the distribution patterns of macrozoobenthos, and SO42- mainly controlling the pattern of oligochaete, and hardness the maim factor affecting mollusks. The average of BI (8.18) revealed the Reserves endured higher organic pollution.

Distribution pattern of rare plants along riparian zone in Shennongjia Area

Due to the importance of riparian zone in maintaining and protecting regional biodiversity, increasingly more ecologists paid their attentions to riparian zone and had been aware of the important effects of riparian zone in basic study and practical management. In this study, 42 sampling belts (10 m×100m) parallel to the bank of Xiangxi River at different elevations in Shennongjia Area were selected to investigate the riparian vegetation and rare plants. 14 species of rare plants were found distributing in riparian zone, accounting for 42.4% of the total rare plant species in Shennongjia Area. The main distribution range of the 14 rare plant species was the evergreen and deciduous mixed broadleaved forest at elevation of 1200–1800 m, where, species diversity of plant community was the maximum at the moderate elevation. The analysis of TWINSPAN divided the 14 rare species into 3 groups against the elevation, namely low elevation species group, moderate elevation species group, and high elevation species group. The analysis of DCA ordination showed similar results to that of TWINSPAN. In the paper, the authors discussed the reasons forming the distribution pattern of rare plant species, and pointed out that the important function of riparian zone on rare plant species protection.

Water environment and aquatic ecosystem of Three Gorges Reservoir,China:progress and prospects

As the final completion of the world-famous Three Gorges Project,the Three Gorges Reservoir(TGR) came into a normal operation stage since the year 2010,with an annual water level fluctuation of 30m.Reservoir limnology can provide a scientific basis for environment-friendly dam construction and reservoir sustainable management.On the basis of long-term monitoring and investigation on the TGR ecosystem for 8a,this paper described the current status of aquatic environment in the reservoir,and elaborated the spatial-temporal heterogeneity of water environmental dynamics,longitudinal zonation and biological community structure,vertical distribution,and forming and tendency of algal bloom of the TGR.The early warning of algal bloom and eco-hydrological regulation mechanism were also analyzed.Two perspectives of ecological research on TGR were finally pointed out in the paper: 1) Limnological observation and research in the large reservoir should have a long-term strategy;2) Research in near future should focus on the quantification of hydrodynamics mechanism on algal bloom,and the coupling of early warning models of algal bloom and eco-hydraulic regulation platform.

Community structure characteristics of phytoplankton along a cascade of reservoirs in Xiangxi River Basin, Three Gorges Reservior

Xiangxi River originates from the Shennongjia Forest region and is the largest tributary in Hubei Province of Three Gorges Reservoir.Three reservoirs(Gudongkou Reservoir 1,Gudongkou Reservoir 2 and Xiangxi Bay of Three Gorges Reservoir) in Xiangxi River Basin were selected to investigate phytoplankton ecology in such a reservoir cascade system.In this study,phytoplankton composition,dominant species,community structure,abundance and biodiversity index were investigated and analyzed from October 2005 to July 2006.A total of 121 species,belonging to 58 genera in 7 phyla were identified,among which Chlorophyta(49 species of 26 genera) is the most important compontent,accounting for 40.50% of the total;followed by Bacillariophyta(41 species of 14 genera) for 33.88%,and Pyrrophyta(11 species of 3 genera) for 9.09%,Cyanophyta(7 species of 5 genera) for 5.79%,Cryptophyta(7 species of 3 genera) for 5.79% and other species for 4.96%.31 species of 25 genera,40 species of 29 genera and 81 species of 46 genera were found in Gudongkou Reservoir 1,2,and Xiangxi Bay,respectively.The dominant species in Gudongkou Reservoir 1 belonged to Bacillariophyta,Chlorophyta,while Bacillariophyta,Cryptophyta and Pyrrophyta dominated in Gudongkou Reservoir 2.Chlorophyta,Bacillariophyta,Pyrrophyta,Cryptophyta also played an important role in Xiangxi Bay.The annual abundance of phytoplankton community in the three reservoirs was 1.110×106,4.837×105 and 1.734×106 cells/L,respectively.It had highest density in Xiangxi Bay(4.87×106 cells/L) and lowest density in Gudongkou Reservoir 2(5.76×105 cells/L).Principal Component Analysis was applied to analyze the water quality of the three reservoirs.The result implies that the water quality was degrading along the cascade of reservoirs.There were no significant differences in diversity index(H) and evenness(J) among the three reservoirs,while the Margalef index of Xiangxi Bay was significantly larger than that of Gudongkou Reservoir 1 and Gudongkou Reservoir 2.The valuation results by the first two indices and dominant phytoplankton species showed that the cascade reservoirs in Xiangxi River Basin were of intermediate pollution state.

Characteristics, classification and ordination of riparian plant communities in the Three-Gorges areas

Sixteen different vegetation types of grassland and shrubland were selected to study the component and diversity of plant species of riparian plant communities along main channel in the Three-Gorges areas. Species richness (s), Simpson index (D), and Shannon-Weiner index (H) were used to study the biodiversity and the hierarchical classification was carried out by the methods of TWINSPAN and DCA ordination. The results showed that the components of flora were complex and dominated by the temperate type in the riparian plant communities. Species diversity was not different between the communities, but Shannon-Weiner indexes of different layers in some grassland were significantly different. TWINSPAN and DCA indicated that riparlan plant communities distributed along the gradient of moisture.