罗非鱼对富营养型水体中沉水植物苦草的影响

通过室外模拟实验,分别设置罗非鱼组和无鱼对照组的两组处理,研究了尼罗罗非鱼（Oreochromis niloticus）对富营养型水体中沉水植物苦草（Vallisneria spiralis）的影响。结果表明：罗非鱼显著地增加了水中总氮和总磷的质量浓度,同时浮游植物的生物量（叶绿素a）也明显增加;罗非鱼组中的附着藻类的生物量却显著低于无鱼的对照组;罗非鱼组中苦草的相对生长率为-10mg·g-1·d-1,显著低于对照组中苦草的相对生长率7mg·g-1·d-1。罗非鱼的直接牧食可能是苦草生物量降低的主要原因。研究说明,过高的罗非鱼密度会导致沉水植被退化,要保持沉水植被为优势的湖泊清水态,必须控制罗非鱼密度。

Effects of tilapia on submerged macrophyte Vallisneria spiralis in eutrophic waters

An outdoor experiment was conducted to investigate effects of tilapia（Oreochromis niloticus）on the growth of submerged macrophyte Vallisneria spiralis.There were two treatments,including tilapia group（with tilapia）and control group（without tilapia）. Results showed that tilapia significantly increased TN,TP and phytoplankton biomass（Chl a）in the water,reduced the biomass of periphyton;The relative growth rate of Vallisneria spiralis in tilapia group was-10 mg·g-1·d-1which was significantly lower than that in the control group 7 mg·g-1·d-1.Grazing by tilapia on macrophytes likely contribute to the reduced biomass of Vallisneria spiralis. Current study suggests that high density of tilapia can lead to the loss of macrophytes and may need to be controlled in order to maintain submersed macrophytes dominated clear water states of shallow lakes.