太湖环棱螺牧食活动对苦草生长的影响

2006年9—10月在太湖“863"项目试验基地进行环棱螺(Bellamya sp.)对苦草生长影响的实验研究. 结果表明:经过5周的生长，对照中苦草生物量增加得不多；而各螺处理中苦草生物量的增长非常明显，且与所投放的环棱螺的密度呈正相关关系，放养20，40和80个螺的处理中苦草生物量的增长率分别为对照的4.5，5.3和6.2倍. 另外，环棱螺对苦草根系的影响，表现为各螺处理中苦草根状茎生物量均大于对照，而根须生物量和根须数均小于对照. 与以上现象相反的是，放养20，40和80个螺的处理中苦草表面附着生物的生物量明显低于对照，分别低于对照的33.3%，54.8%和53.7%. 说明螺与沉水植物共存时，对沉水植物生长及繁殖均有一定的促进作用，在浅水湖泊中放养适当密度的环棱螺能在一定程度上加快沉水植被的恢复. 

Effects of Bellamya sp. on the Growth of Vallisneria atans in Lake Taihu

The effects of Bellamya sp. on Vallisneria atans was studied in the test base in Lake Taihu during Sept. to Oct. 2006. Results showed that there was no obvious change in plant biomass in control treatment, otherwise, the plant biomass increased significantly in other treatments, and showed positive response to an increase of density of snails. The growth ratio of plant biomass in 20, 40and 80 snails treatment are 4.5, 5.3 and 6.2 times higher than in control treatment respectively. Besides, rhizome biomass of Vallisneria atans in treatments with snails notably higher than that in treatment without snail, while it was reverse for the fibre. Contrarily, periphyton biomass in treatment with 20, 40 and 80 snails were significantly lower 33.3%, 54.8% and 53.7% than in treatment without snail. It can be concluded that when coexisting with submerged macrophytes, snails can promote both growth and reproduce of plants. So raising some Bellamya sp. in shallow lake will help to resume submerged aquatic vegetation.