Hongzhu Wang

Macrozoobenthic community of Poyang Lake, the largest freshwater lake of China, in the Yangtze floodplain

Poyang Lake (Poyang Hu) is located at the junction of the middle and lower reaches of the Yangtze (Changjiang) River, covering an area of 3283 km2. As one of the few lakes that are still freely connected with the river, it plays an important role in the maintenance of the unique biota of the Yangtze floodplain ecosystem. To promote the conservation of Poyang Lake, an investigation of the macrobenthos in the lake itself and adjoining Yangtze mainstream was conducted in 1997–1999. Altogether 58 benthic taxa, including 22 annelids, 8 mollusks, 26 arthropods, and 2 miscellaneous animals, were identified from quantitative samples. The benthic fauna shows a high diversity and a marine affinity. The standing crops of benthos in the lake were much higher than those in the river, being 659 individuals/m2 and 187.3 g/m2 (wet mass) in the main lake, and 549 individuals/m2 and 116.6 g/m2 in the lake outlet, but only 129 individuals/m2 and 0.4 g/m2 in the river. The dominant group in the lake was Mollusca, comprising 63.4% of the total in density and 99.5% in biomass. An analysis of the functional feeding structure indicated that collector-filterers and scrapers were predominant in the lake, up to 42.2% and 24.7% in density and 70.2% and 29.2% in biomass, respectively, while shredders and collector-gatherers were relatively common in the river. The present study was restricted to the northern outlet and the northeast part of Poyang Lake. A scrutiny is required for the remaining areas.

Macrozoobenthos in Yangtze floodplain lakes: patterns of density, biomass, and production in relation to river connectivity

Abstract A systematic investigation of macrozoobenthos was conducted in Yangtze floodplain waters to reveal patterns of density, biomass, and production in relation to river connectivity. In the Yangtze-connected lakes, 78 taxa belonging to 33 families and 62 genera were identified. Macrozoobenthos density was 327 individuals/m2, biomass was 1.40 g dry mass/m2, and production was 3.23 g dry mass m−2 y−1. The assemblages were characterized by high diversity, high production, and high bivalve-filterer abundance. The key factor determining the macrozoobenthic assemblages was river connectivity. As river connectivity increased, 3 types of response patterns were observed: 1) density, biomass, and production of collector-filterers (mainly Bivalvia), shredders (e.g., Stictochironomus), and predators (e.g., Dytiscidae) showed unimodal changes, i.e., first increased and then decreased; 2) density, biomass, and production of collector-gatherers (mainly Tubificidae and Chironomidae) decreased continuously; and 3) density of scrapers (mainly Gastropoda) decreased, whereas their biomass and production changed unimodally. At an intermediate level of river connectivity, biomass and production of total macrozoobenthos reached maxima, whereas density decreased with increasing river connectivity. Previous research showed that α diversity of zoobenthos also peaks at moderate connectivity with rivers. Therefore, to maintain high productivity as well as high biodiversity in the Yangtze floodplain, protecting the remnants of river-connected lakes and linking disconnected lakes freely with the mainstream are crucial.

A preliminary study of oligochaetes in Poyang Lake, the largest freshwater lake of China, and its vicinity, with description of a new species of Limnodrilus

The oligochaete fauna of the largest freshwater lake of China, Poyang Lake, has never been investigated before. On the basis of a preliminary survey in the lake and its vicinity in 1997–1999, 25 species belonging to 20 genera and 5 families are recorded. Among them, one genus, Cernosvitoviella (Enchytraeidae), and two species, Bratislavia unidentata (Naididae), Potamothrix bedoti (Tubificidae), are recorded from China for the first time. Another tubificid, Limnodrilus paramblysetus sp. nov., is new to science. It is similar to L. amblysetus Brinkhurst et al., 1990 in chaetal shape but differs in having short hooded penis sheaths.

Distributions of two ectosymbionts, branchiobdellidans (Annelida: Clitellata) and scutariellids (Platyhelminthes: "Turbellaria": Temnocephalida), on atyid shrimp (Arthropoda: Crustacea) in southeast China

Distribution of two ecologically similar but usually spatially separate ectosymbionts, branchiobdellidans (Annelida) and scutariellids (Platyhelminthes), on atyid shrimp (Neocaridina spp.) is reported from 18 localities in five Provinces of southeastern China. Prevalence was determined for the branchiobdellidan, Holtodrilus truncatus, found at seven locations, the scutariellid, Scutariella japonica, present at every site, and where cohabitation occurred. Both ectosymbionts showed a microhabitat predilection for the hosts branchial chambers and instances of cohabitation occurred at all seven locations where H. truncatus were collected, although not on every shrimp. On-site observations of live hosts supporting both ectosymbionts showed that neither H. truncatus nor S. japonica reacted aggressively or defensively towards the other when in close proximity. Instances of imported Chinese Neocaridina spp. into central Honshu Island, Japan, almost certainly came from areas in southeast China identified in this study. These imported populations are predicted to spread northwards into the area where endemic Japanese branchiobdellidans occur.

Effects of water level fluctuations on lakeshore vegetation of three subtropical floodplain lakes, China

Vegetation communities in floodplain lakes are adapted to natural water regimes. Construction of sluices or dams between rivers and their floodplain lakes will inevitably lead to great changes in plant communities. In order to evaluate the effects of water level fluctuations (WLFs) on lakeshore vegetation in floodplain lakes of the Yangtze River, a field investigation was conducted in two river-disconnected lakes (Wuchang Lake and Shengjin Lake) and one river-connected lake (Shimen Lake). The results showed that plant species richness was highest in the disconnected Shengjin Lake with intermediate amplitude of WLFs, and lowest in the connected Shimen Lake. Species composition differed among the three lakes and the two disconnected lakes with more similar WLFs exhibiting the greatest similarity. Six plant communities were classified using TWINSPAN. Multivariate analyses showed that the amplitude of WLFs was the most important factor in determining the distribution of lakeshore plants, followed by relative elevation and duration of submergence. Our results provide an eco-hydrological basis for plant restoration in the Yangtze floodplain lakes. We suggest that fluctuating amplitude should be increased in lakes with small WLFs, and small habitats with various hydrological regimes should be created in lakes with large WLFs.

Food web of benthic macroinvertebrates in a large Yangtze River-connected lake: the role of flood disturbance

This Study was conducted in Lake Dongtinghu, a large river-connected lake on the Yangtze River flood-plain, China. Our goal was to determine trophic relationships among benthic macroinvertebrates, as well as the effects of flood disturbance on the benthic food web of a river-connected lake. Macroinvertebrates in the lake fed mainly on detritus and plankton (both zooplankton and phytoplankton). Food web Structure in Lake Dongtinghu was characterized by molluscs as the dominant group, low connectance, high level of omnivory. based oil detritus and primary production, and most ingestion concentrating on a few links. Our analyses showed that flood disturbance is an important factor affecting the benthic food web in Lake Dongtinghu. The numbers of species and functional feeding groups (FFGs), and the density and biomass of macroinvertebrates decreased significantly during flooding. Connectance was higher during the flood season than in other seasons, indicating that floods have a strong effect on connectance in this Yangtze River-connected lake. Flood effects on the benthic web were also evident in the decrease of niche overlaps within and anion, FFGs. Our results provide useful information regarding biodiversity conservation on the Yangtze floodplain. Reconstructing and maintaining natural and regular flow regimes between Yangtze lakes and the river is essential for restoration of macroinvertebrates on the floodplain.

Records of enchytraeidae (Clitellata) from the People's Republic of China

Eleven species of terrestrial and aquatic Enchytraeidae are reported from southeastern China. Fridericia multisegmentata and Enchytraeus athecatus are new to science, while most of the others are recorded from the country for the first time.

Macrozoobenthic assemblages in relation to environments of the Yangtze-isolated lakes

Eutrophication can shift lakes from a clear, macrophyte-dominated state to a turbid, algae-dominated state, and different habitat condition supports different fauna. Macrozoobenthos are good indicators of water environment, and studies on macrozoobenthic assemblage characteristics can help us to know which state a lake is in, thus provide the basis for its eutrophication control. In this study, a systematic investigation on macrozoobenthos was conducted in 17 Yangtze-isolated lakes to explore the macroecological laws of macrozoobenthic assemblages. Detrended correspondence analysis (DCA) revealed that variance of benthic assemblage structure occurred in two types of lakes. In macrophytic lakes, altogether 51 taxa of macrozoobenthos were identified. The average density and biomass of total macrozoobenthos were 2231 individuals·m−2 and 1.69 g dry weight·m−2, respectively. Macrozoobenthic assemblage was characterized by dominance of scrapers (i.e. gastropods). In algal lakes, altogether 20 taxa of macrozoobenthos were identified. The average density and biomass of total macrozoobenthos were 2814 individuals·m−2 and 1.38 g dry weight·m−2, respectively. Macrozoobenthic assemblage was characterized by dominance of collector-gatherers (i.e. oligochaetes). Wet biomass of submersed macrophytes (BMac) and phytoplankton chlorophyll a concentration (Chl a) were demonstrated as the key factor structuring macrozoobenthic assemblages in macrophytic and algal lakes, respectively.

Limnodrilus simplex sp. nov. (Oligochaeta: Naididae: Tubificinae) from Changjiang River, China

Limnodrilus simplex sp. nov. (Oligochaeta: Naididae: Tubificinae) is described based on a single specimen from the mainstream of the Changjiang River near Anqing City, Anhui Province, China. The new species is assigned to Limnodrilus by the presence of long vasa deferentia, spindle-shaped atria with long ejaculatory ducts, large prostate glands, and thick cylindrical penial sheaths. It differs from its congeners in having simple-pointed chaetae and cuticularized penial sheaths without hoods. Limnodrilus simplex is closer to L. paramblysetus and L. amblysetus in possessing penial sheaths with relatively low length/maximum width ratio.

Potamothrix scleropenis sp. nov. (Oligochaeta: Tubificidae) from Fuxian Lake, the Deepest Lake in Southwest China

Abstract Potamothrix scleropenis sp. nov. (Tubificidae: Tubificinae) is described from the profundal zone (74 m) of Fuxian Lake, the deepest lake (up to 155 m) on the Yunnan-Guizhou Plateau in China. The new species is assigned to Potamothrix because of its short vasa deferentia and its tubular atria without ejaculatory ducts and prostate glands. It differs from congeners by its cuticularized penis sheaths; bifurcated, strongly curved spermathecal chaetae; bifurcated lower prongs of bifids; and feathered hairs. P. scleropenis appears closely related to P. cekanovskajae Finogenova, 1972 and P. tudoranceai Sporka, 1994, since all the three species have homogeneous atria without prostate glands.