[Seasonal changes of fish species composition and diversity in mudflat wetlands of Hangzhou Bay].

In order to understand the spatiotemporal variation of fish species composition and biodiversity in the mudflat wetlands of Hangzhou Bay, thirty six surveys were conducted in the mudflat area, inning area, and aquaculture area in the south bank of the Bay in. March (early spring), May (spring), July (summer), and October (autumn), 2009. A total of 41 species belonging to 9 orders and 16 families were observed, among which, Cyprinid had the largest species number (14 species, 33.3% of the total), followed by Gobiidae (8 species, 19.1%). According to the lifestyle of fish, these 41 species could be divided into five ecological types, i.e., freshwater type (21 species), brackish-water type (16 species), inshore type (2 species), anadromous type (Coilia ectenes), and catadromios type (Anguilla japonica). The fish abundance was the highest (54. 5 fish per net) in summer, followed by in spring and autumn, and the lowest (17.7 fish per net) in early spring. In the three habitats, mudflat area and inning area had the similar seasonal change of fish abundance, i.e., the lowest in early spring, the highest in summer, and then decreased in autumn. Only two or three species were the dominant species in different seasons. In mudflat area, the dominant species were Mugil cephalus and Liza carinatus; while in inning and aquaculture areas, the dominant species were Carassius auratus, Hemiculter leucisculus, and Pseudorasbora parva. The values of Margalef's richness index (D), Pielou's evenness index (J), and Shannon index (H) were lower in March than in other months, but had no significant differences among May, July, and October (P > 0.05). The H value ranged in 0. 27-2. 13, being the lowest in March and higher in May and October (1.66 and 1.63, respectively). Overall, the fish abundance and biodiversity in the mudflat wetlands of Hangzhou Bay had apparent seasonal changes.

[Impacts of large hydropower station on benthic algal communities].

To investigate the impacts of large hydropower station in Gufu River on benthic algae, monthly samplings were conducted from September 2004 to June 2007 at the site GF04 which was impacted by the hydropower station, with the site GL03 in Gaolan River as reference. During sampling period, no significant differences were observed in the main physicochemical variables between GF04 and GL03, but the hydrodynamics differed significantly. GL03 was basically at a status of slow flow; while GF04, owing to the discharging from the reservoir, was at a riffle status during more than 60% of the sampling period. Such a difference in hydrodynamics induced significant differences in the community similarity of benthic algae and the relative abundance of unattached diatoms, erect diatoms, and stalked diatoms between GF04 and GL03, which could better reflect the impacts of irregular draw-off by large hydropower station on river eco-system.

[Seasonal dynamics of macrozoobenthos community structure in Xiangxi River].

To study the seasonal dynamics of macrozoobenthos community in Xiangxi River, the individuals of macrozoobenthos in the River were quantitatively monitored. A total of 197 taxa belonging to 6 class and 68 families were collected, among which, Baetis spp., Epeorus spp., and Nemoura spp. were the dominant groups, and their compositions varied with seasons. The macrozoobenthos community was most complicated in winter, followed by in spring and autumn, and the simplest in summer. Gather-collector was the main component of functional feeding groups in Xiangxi River system, followed by scraper, predator, and filter-collector, while shredder only accounted for a small part. Canonical correspondence analysis showed that the factors affecting the macrozoobenthos community were dissimilar among seasons. In summer and autumn, nutrients had greater effects; and in all seasons, water depth had definite effects.

[Spatiotemporal variation of epilithic algae in Xiangxi River system].

Xiangxi River system is the greatest branch in the Hubei reservoir area of the Three Gorges reservoir. In this paper, the epilithic algae in the River and its three major tributaries were investigated from July 2005 to June 2006. A total of 218 taxa were identified, including 183 species of Bacillariophyta, 24 species of Chlorophyta, 10 species of Cyanophyta, and one species of Xanthophyta. The diatom Achnanthes linearis was the most predominant species. The richness and Shannon-Wiener diversity indices varied significantly (or almost significantly) over time and space, and the total average values were 32 and 1.54, respectively. The total averages of annual epilithic algal density and chlorophyll a concentration were 8.75 x 10(9) cells x m(-2) and 14.62 mg x m(-2), respectively. There were significant differences in the algal density and chlorophyll a concentration among different sampling sites, and the maximum values were observed in Gufu River tributary, which were one order of magnitude higher than the minimum ones in Jiuchong River tributary. The algal density and chlorophyll a concentration tended to be higher in winter and spring than in summer and autumn, but no significant differences were observed in various seasons. Epilithic algal density and chlorophyll a concentration were significantly negatively correlated with elevation and water current, but positively correlated with the total nitrogen concentration in water.