The Effects Of Different Lake Uses On Zoobenthic Community

To examine the effects of different lake uses on lacustrine zoobenthic community, zoobenthos were sampled in 1998-1999 from four shallow lakes of middle and lower basins of Changjiang River, viz. fish stocking and touring lake, East Tangsun Lake; fish-stocking-lake, Niushan Lake; natural-fishing-lake, Longgan Lake and crab-overstocking-lake, Huang Lake. Species composition, standing crops, functional feeding groups of benthic animals in every lake were studied. The differences of species number, meansize, standing crop, production and fishery capacity of zoobenthos in four lakes were compared. In combination to physico-chemical and other biological factors, the effect of different lake uses on zoobenthic community was analyzed.The species number of zoobenthos in East Tangsun Lake, Niushan Lake, Longgan Lake and Huang Lake were 36, 24, 33, and 18, respectively. The differences in species richness and species diversity in the four lakes were obvious.In the four lakes, oligochaete density in Longgan Lake was maximal while that in Niushan Lake was minimal and the difference in two lakes was distinct (p 0.05). Gastropod density was substantially higher in Niushan Lake than other three lakes (p 0.05). Bivalve density in East Tangsun Lake was maximal while that in Niushan Lake and Longgan Lake were minimal. Insect density in East Tangsun Lake was maximal but that in Huang Lake was minimal, and the differences of them among three lakes were distinct (p 0.05). Zoobenthic density in East Tangsun Lake was maximal but that in Huang Lake was minimal, and the difference in two lakes was distinct (p<0.05). The biomass of zoobenthos in four lakes existed differences but the differences were not distinct statistically (p>0.05).There were few reports about zoobenthic functional feeding groups in China so far, a detailed study of functional feeding groups species numbers, species percentages and standing crops in four lakes was done. Results showed that functional feeding groups in the four lakes had their own characteristics. Shredder percentage was highest in Longgan Lake than other three lakes. Collector percentage in Huang Lake was highest. Scraper percentage in Niushan Lake was highest. Predator percentage was highest in East Tangsun Lake.Production (kg/hm2/yr) of zoobenthos in four lakes ranging from high to low was Niushan Lake (1082.1), Longgan Lake (767.4), East Tangsun Lake (564.2) and Huang Lake (329.6), while fishery capacity (kg/hm2/yr) ofzoobenthos was East Tangsun Lake (16), Longgan Lake (15.8), Huang Lake (14.3) and Niushan Lake (10.4).For the relationships between zoobenthos and environmental factors, results showed that zoobenthic standing crops were positively correlated with submersed aquatic macrophytes, total phosphorus and total nitrogen contents but were negatively correlated with depths and Secchi disk transparencies. Taxonomic groups of zoobenthos were significantly correlated with biomass of submersed aquatic macrophytes, depths, Secchi disk transparencies, total phosphorus and total nitrogen contents.The effect of different lake uses ways on zoobenthic community is great in general. The effect of touring and food supplying in East Tangsun Lake caused organic pollution and algal eutrophic lake. Fish stocking in Niushan Lake eliminated submersed macrophytes and gave indirect effect on biomass in Niushan Lake to an extent that gastropod was only 1/5 as much of a typical macrophytic lakes such as Hong Lake. Longgan Lake represents natural fishing lake, having little effect on zoobenthos. Mitten crabs (Eriocheir sinensis Edwards) have been cultured since many years ago in Huang Lake, where zoobenthos were very sparse. Under stocking density of about 1 kg/hm of crab larvae or juveniles, zoobenthic density and production were reduced by more than 60%. Zoobenthos were affected by mitten crabs in two ways: direct feeding on benthos and indirect effect through damage of submerged macrophytes. At present the submersed macrophytes in the lake are almost absent but floating plant...