The Inhibitory Effects Of Nelumbo Nucifera,Nymphaea Tetragona And Snails On The Growth Of Algae In Eutrophicated Water Body

The problem of eutrophication of lakes and reservoirs and its rate of appearance is becoming larger all over the world. It's also one of the primary problems of water environment in China (YU De-hui, 2000). Blue algae especially Microcystis species is the primary species which is easy to bloom, so how to control the abnormal growth of Microcystis is always one of the most important article of the research of eutrophication of lakes (He Z R., 1997), many researchers investigated blue algae bloom from different points of view (Satoshi N, et al., 1999; Takamura N T, et al., 1985; Lu Yuan, et al., 2001). However in China, Microcystis aeruginosa is the primary alga which causes eutrophication of water bodies. It can compose and excrete cell toxins, affect directly safety of both fish faming and the Nation's drinking water supply. Besides, Microcystis toxins is also an important factor that can induce diseases including liver cancer in people (LI Xiao-yu, 1999; Jochimsen E M, et al., 1998). So, protection against eutrophication , especially the control of Microcystis aeruginosa growth has become an important environment problem desiderated to be solved.The article used Microcystis aeruginosa which often appeared in water bloom as research object, in order to study the inhibitory effects of liquor cultured with Nelumbo nucifera and Nymphaea tetragona and extracts from them, and Lymnaeidae Radix auricularia and Austropeplea ollula on the growth of Microcystis aeruginosa. We hoped that it could study the contribution of ornamental aquatic plants and snails in mollusca to the self-purification ability of water and provide value research data for constituting steady aquatic ecosystems. The results showed that:The results showed that the inhibitory effects on the growth of Microcystis aeruginosa with different concentration of the liquor cultured with Nelumbo nucifera and Nymphaea tetragona were dissimilar by measuring the cells number and the content of chlorophyll a of Microcystis aeruginosa, and appeared an evident phenomenon that low concentration could promote the growth of Microcystis aeruginosa. However, the inhibitory effects on the growth of Microcystis aeruginosa with continuous liquor cultured with Nelumbo nucifera and Nymphaea tetragona were obvious, which made the algal cell almost lose the capability of photosynthesis, and the inhibitory effects of liquor cultured with Nymphaea tetragona were better than the effects of Nelumbo nucifera. The scale-up experiment demonstrated that the algal cell received menace and damage by measuring the activities of peroxidase (SOD) and the accumulated contents of malondialdehyde (MDA) of Microcystis aeruginosa in the co-culture. Sterilization methods influenced the algal growth inhibition experiment so that high temperature couldn't replace micropore filter, which explained that the matter which was excreted by Nelumbo nucifera and Nymphaea tetragona may contain thermally-instabe matter .The inhibitory effects of extracts from Nelumbo nucifera and Nymphaea tetragona on the growth of Microcystis aeruginosa have been investigated. The inhibitory ratio of extracts from the two plants on the growth of Microcystis aeruginosa was higher with injecting more extracts. The inhibitory effects of extracts from Nymphaea tetragona on the growth of Microcystis aeruginosa were better than extracts from Nelumbo nucifera. When extracts from Nelumbo nucifera and Nymphaea tetragona were injected about 25g/L, the best inhibitory ratio of extracts from Nelumbo nucifera and Nymphaea tetragona on the growth of Microcystis aeruginosa could achieve respectively 91.2% and 96.4%. At the same time, the algae nearly stopped growing, extracts from the two aquatic macrophytes made the algal cell almost lose the capability of growth, and and the chlorophyll a content of Microcystis aeruginosa also had a drop.The results showed that Radix auricularia had definite effects on the biomass and the chlorophyll a content of Microcystis aeruginosa in the 250mL liquor culture. The more number of snail, the more marked inhibitory effects could receive. And three Radix auricularias made the algal cell almost lose the capability of growth. The inhibitory effects of Radix auricularia on the growth of Microcystis aeruginosa is better than the effects of Austropeplea ollula. The scale-up experiment demonstrated that the standard of 6.0g/L for Radix auricularia could receive obvious inhibitory effects on the growth of Microcystis aeruginosa and the cell of Microcystis aeruginosa stopped normal growing.