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Wetlands as a complex ecosystem, with a variety of features and functions, which relate to hydrology, ecosystem services, self-healing, automatically adjust various aspects. In freshwater ecosystems is also a wetland ecosystem, but its habitat has discontinuities, leaving them vulnerable to the impact of invasive species, leading to damage or even loss of wetland function. For freshwater ecosystems, invasive alien species in the local habitat wantonly feeding can cause many aspects, but most of the research is limited to the direct impact of invasive species for large-scale plants, rarely involved in other aspects. Therefore, the study of invasive species of apple snails (Pomacea canaliculata) study, a small ecosystem design two simulation wild peripherals every experiment and a laboratory experiment, in addition to further prove that the apple snails large plants explored in water filamentous algae, zooplankton Wei algae and water nutrients in all aspects. Two field experiments were carried out in the Hong Kong Wetland Park. Enclosures (1 m 1 m 1 m) were randomly placed in selected waters, and then placed in a 500 g mesocosm plant: Myriophyllum (Myriophyllum aquaticum), Eichhornia crassipes (Eichhornia crassipes), and then put in a different number of (0,2,4,8), apple snails, regularly detection analysis parameters, each experiment lasted a month. Design, based on the results of field experiments, laboratory experiments with collected from experiments waters, filamentous algae (mainly Spirogyra Spirogyra sp) feeding apple snails, in order to determine the rate of apple snails ingestion of filamentous algae. The experimental results show that: the the apple snails feeding on two plants are very strong, snail density greater the plants are the greater the damage. For both, the the apple snails performance of feeding way is not the same in the Myriophyllum, apple snails mainly feed on its leaves and stems; Eichhornia crassipes, apple snails eat its roots. Further, found: from Ueno peripheral experiment compartment snails treatment groups, filamentous algae almost no growth; spiro-free control group, a large number of filamentous algae blooms, or even forming the the Chlorella batt (Pond Scum), its biomass up to 80.3 g m-(2 wet weight), this phenomenon shows that the the apple snails effective to control the growth of filamentous algae in water, filamentous algae carried out indoor experiments further confirmed this conclusion. In the laboratory experiments, apple snails daily feeding rate of filamentous algae up to 0.25 gg -1 of snail DW d -1 . Field experiment, the concentration of nitrogen and phosphorus were maintained at a low level, and Lo density. The chlorophyll a (Chlorophyll a, Chl a) concentration of phytoplankton community structure changes both in each experiment different: Myriophyllum experiments in, Chl a concentration increased with increasing snail density hidden alga (Cryptophyceae) gradually became the dominant algae group; Eichhornia crassipes experiment with increasing snail density, Chl a concentration exhibit erratic changes phytoplankton is gradually showing cryptalgal, green algae (Chlorophyceae) and silicon algae (Bacillariophyceae) the dominant structure. According to the results of this study shows that the apple snails have an impact on wetland biodiversity, wetland functions. Need to continually improve the control strategies in the treatment of invasive alien species. Apple snails invasion wetlands, on the one hand, to take effective strategy to completely remove the other hand, consider the reintroduction of local native snails, in order to control the massive growth of filamentous algae, avoid green algae floc layer outbreak led to water deterioration.
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