Eutrophic Chinese Lake Research Articles

The restoration of riparian wetlands and macrophytes in Lake Chao, an eutrophic Chinese lake : possibilities and effects

Experiments with replanting macrophytes in Lake Chao showed that the water quality inside an Alternathera philoxeroides Griseb.and a Phragmites australis community were better than outside. Transparency was significantly higher and the content of N and P decreased inside the communities, as did the rate of sedimentation of organic suspended matter in the Phragmites australis community. Modeling revealed that macrophyte restoration could decrease phytoplaniton biomass, increase fish biomass, exergy, structural exergy, zooplankton/phytoplankton ratio and transparency (Xu et al., 1999b). It is concluded that macrophyte restoration can purify lake water, regulate lake biological structure and control eutrophication.

Long-term changes in crustacean zooplankton and water quality in a shallow, eutrophic Chinese lake densely stocked with fish

From surveys made in 1962–1963, 1973–1974, 1979–1996 at two Stations in Lake Donghu, a shallow eutrophic water body near Wuhan, P. R. China, the authors, derive long-term changes in species composition, standing crop and body-size of planktonic crustaceans. The species number decreased from the 1960s to the 1990s. The cladocerans dropped from 46 (1960s) to 26 (1980s) to 13 (1990s); the copepods decreased from 14 (1960s) to 10 (1980s) to 7 (1990s). From the mid-1980s on, the dominant crustaceans also changed: Daphnia hyalina and D. carinata ssp. were replaced by Moina micrura and Diaphanosoma brachyurum at Stations 1 and 2, respectively; Cyclops vicinus replaced Mesocyclops leuckarti.

Seston and dissolved organic carbon dynamics duringMicrocystis bloom with special reference to the effects of three Chinese domestic fishes in experimental enclosures

TheMicrocystis bloom that once disappeared from Donghu Lake, a shallow, eutrophic Chinese lake, was successfully resumed with the use of the enclosure method. Seston and dissolved organic carbon (DOC) dynamics during theMicrocystis bloom were investigated with particular emphasis on the effect of three Chinese domestic fishes (silver carp, bighead carp and grass carp). The results showed that the change of chlorophyll a obviously related to the fish species and its stocking density. Due to the release of extracellular ogranic carbon and increased bacterial activity, DOC increased apparently after silver and bighead carps were introduced. POC/DOC dropped considerably in the enclosures containing silver and bighead carps and in the surrounding lake water, which implied that the bacterial activity was more pronounced in such ecosystems. Statistical analysis indicated that the linear relationship between POC and chlorophyll a could reflect the state of algal growth and nutrient metabolism. It was expected that this study would provide some information on biomanipulation in the shallow, eutrophic lakes.

Ecosystem health assessment of Lake Chao, a shallow eutrophic Chinese lake

AbstractEcosystem health is a newly proposed concept that sets new goals for environmental management. Its definition, index and assessment methods are still being perfected. Eutrophication is a serious disease of lakes and reservoirs around the world that has badly damaged lake ecosystem health, and resulted in disharmony of ecosystem structure, and a decrease in biodiversity and resilience. In this case study for Lake Chao, an attempt to apply trophic state index (TSI), diversity index (DI), exergy (Ex), structural exergy (Exst) and phytoplankton buffer capacity β(TP)(phyto) to the assessment of the Lake Chao ecosystem health is presented. The results reveal that these indicators can give appropriate information on the state of health of the Lake Chao ecosystem. From January to March 1988, Ex, Exst, and DI are highest, the TSI and β(TP)(Phyto) are lowest. The lake ecosystem is relatively healthy; however, there are still some problems such as the disharmony of biological structure (too much zooplankton biomass and too little phytoplankton biomass). From August to October and from April to May 1988, the TSI and Ex are higher; and DI, Exst and β(TP)(phyto) are lower. This implies that the lake ecosystem is a typical eutrophic system, and lake ecosystem health is poor, especially in September and May. A relative order of state of health for the Lake Chao ecosystem from good to bad can be derived: January to March 1988 > November to December 1987 > June to July 1987 > April to May 1987 > August to October 1987. The results are in accordance with actual situations.

Plankton and seston structure in a shallow, eutrophic subtropic Chinese lake

The seasonal dynamics in the nutrient concentrations, chlorophyll-a amount (Chl-a), total algal volume (CV), Chl-a/CV ratio, seston structure were studied at two sampling stations in a shallow, highly eutrophicated subtropic lake (the Guozheng Hu area of the East Lake) on the plain of the middle basin of the Chang Jiang (the Yangtze River) of China. The lake ecosystem of the Guozheng Hu area is dominated by two planktivorous fishes (silver carp and bighead carp), phytoplankton and zooplankton. Macrophytes are extremely scarce in this area. Concentrations of the total dissolved nitrogen and phosphorus in the Guozheng Hu area in 1990 were very high. Fish yield, of which, more than 90 % was composed of silver carp and bighead carp in the Guozheng Hu area was very high (ca. 1140 kg/ha or 45.6 g/m3 in 1990). Grazing pressure by the fishes on the plankton community is considered to be rather strong. The annual average biomass of zooplankton was ca. 1/3 - 1/2 that of phytoplankton. On the average, dry matter in the living plankton only constituted ca. 3-7 % of the total dry seston, and plankton carbon only constituted ca. 5 - 10 % of the seston carbon. The present results indicate that, in the Guozheng Hu area of the East Lake, of the organic part of the seston, detritus is quantitatively an important constituent, while living plankton is only a very small component.