伊乐藻(Elodea nuttallii)对高浓度氮磷营养盐的耐受性

Endurance of Elodea nuttallii to high concentration of nitrogen and phosphorus

通过5个相对恒定的TN、TP浓度梯度下伊乐藻(Elodea nuttallii)的生长实验,探讨了伊乐藻对高浓度氮磷营养盐的耐受性,比较了各营养盐浓度下水体的pH值、DO、浮游藻类叶绿素a和附着藻类叶绿素a以及伊乐藻的株高、湿质量、干质量和叶绿素a含量。结果表明:在实验条件下,伊乐藻能耐受TN=10mg·mL-1,TP=0.4mg·mL-1的胁迫,且在该营养盐水平下水体中没有出现大量的浮游藻类;而在TN=50mg·mL-1、TP=2mg·mL-1和TN=100mg·mL-1、TP=4mg·mL-1的高营养盐条件下,伊乐藻的生长受到了明显的抑制,同时水体中的浮游藻类明显增多,而附着藻类则明显减少;在高营养盐水平下,一方面水体中的某些营养盐可能对伊乐藻产生了直接伤害,另一方面水体中浮游藻类的增多,所导致的遮光作用也可能限制了其生长;对水体中营养盐的平均水平低于TN=10mg·mL-1,TP=0.4mg·mL-1的太湖而言,沉水植被的消亡可能不是由于氮磷营养盐所产生的直接伤害和胁迫。

In a growth experiment,five relatively constant gradients of total nitrogen（TN）and phosphorous（TP）concentrations were installed to study the endurance of Elodea nuttallii to high concentrations of nitrogen and phosphorus.The pH value,DO,planktonic chlorophyll a,and periphytic chlorophyll a in the culture solutions as well as the height,wet and dry weights,and chlorophyll a concentration of E.nuttallii were compared among the treatments.Elodea nuttallii could endure the stress of TN=10 mg·L-1 and TP=0.4 mg·L-1,and no abundant phytoplankton occurred under this stress.However,under the stress of TN=50 mg·L-1 and TP=2 mg·L-1 and of TN=100 mg·L-1 and TP=4 mg·L-1,E.nuttallii growth was obviously limited,and plankton increased but periphyton decreased markedly,which suggested that the high concentration TN and TP in water body could have direct damage to E.nuttallii,and the shading caused by phytoplankton multiplication could partly limited the growth of E.nuttallii.As for Taihu Lake,in which,the average concentrations of TN and TP were lower than 10 mg·L-1 and 0.4 mg·L-1,respectively,the decline of submerged aquatic macrophytes could not be caused by the direct harm and stress of nitrogen and phosphorus.