蓝藻堆积和螺类牧食对苦草生长的影响

设计了双因素四组处理(对照组,加螺组,加藻组,螺藻组)的室外受控实验,模拟湖泊沿岸带水华蓝藻的堆积以及底栖螺类的牧食活动对沉水植物苦草生长的影响。结果表明:蓝藻堆积(水体叶绿素a浓度为220μg/L)对苦草的生长具有明显的抑制作用,和对照组以及加螺组相比,加藻组和螺藻组中苦草的相对生长率分别下降了40.9%和36.4%,分株数也分别下降了56.4%和64.1%,分析认为蓝藻在水体表层堆积所产生的遮光可能是抑制底层苦草生长的主要原因。然而,环棱螺能在一定程度上促进苦草的生长,加螺组和螺藻组中苦草的相对生长率和分株数分别要明显高于对照组和加藻组,这可能要归因于螺类的牧食去除了沉水植物表面附着生物。实验中蓝藻堆积和螺类牧食对苦草的各项生长指标均无显著的交互作用,但蓝藻对苦草生长的抑制作用要远大于螺类对植物生长的促进作用。研究证实了在富营养浅水湖泊中,水华蓝藻在湖泊沿岸带的堆积会严重胁迫沉水植物的生长,而底栖螺类的牧食活动则能在一定程度上提高植物在不良环境下的生存能力。

Effects of cyanobacterial accumulation and snail grazing on the growth of vallisneria natans

Cyanobacterial blooms is a common phenomenon in large shallow eutrophic lakes such as Lake Taihu, China. When it occurs, a dense algal mass may accumulate in the littoral zone under the action of wind and waves. This algal layer at the surface water can last for a few days and may pose negative influences on local aquatic plants, especially submerged macrophytes. However, there is a severe lack of studies to evaluate the impacts by the algal bloom formation. A great deal of studies showed that some benthic snails can promote the growth of submerged aquatic plants by their grazing activities in clear water lake ecosystems, but in turbid lakes with high concentrations of cyanobacteria, whether the snails still have positive impacts on the growth of submerged plants remains unclear. Here, we conduct a mecocosm experiment with a 15-day duration to explore the influence of cyanobacterial accumulation and snail grazing on the growth and reproduction of submerged aquatic plants. In this experiment, snail Bellamya aeruginosa, submerged macrophyte Vallisneria natans and cyanobacteria were selected from Meiliang Bay of Lake Taihu, China. Our experiment design included four treatments(control, snails only, cyanobacteria only and snails