低溶解氧对苦草生长的影响

针对太湖梅梁湾生态净化示范区内重建的沉水植物存在的腐烂死亡问题及伴随的底层水体溶解氧偏低现象，在室外模拟生态系统内进行了低氧对沉水植物（苦草）生长的影响试验。结果表明：无论沉积物类型如何，一个月的低氧处理（溶解氧平均值为1.6 mg/L）对苦草株重、株高、分蘖数及叶片数等指标的影响均不明显，对块茎的影响则较显著，表现为块茎数量与重量显著下降。对岸边沉积物处理组而言，低氧对苦草根系的影响显著，表现为根须变细且数量增加，根系活力明显下降，中心沉积物处理组则不显著。同时，低氧处理使岸边沉积物处理组的沉积物氧化还原电位显著下降、水体营养盐浓度上升，尤其是磷酸盐浓度显著增加，中心沉积物处理组的环境理化因子变幅则相对较小。分析认为，低氧对苦草生长的影响虽不明显，但对其种群扩张有潜在的不利作用；梅梁湾生态净化示范区内沉水植物的腐烂死亡，低氧的作用是次要或间接的。

EFFECT OF LOW DISSOLVED OXYGEN ON THE GROWTH OF VALLISNERIA SPIRALIS

In order to ameliorate the water quality of Taihu Lake, a eutrophic shallow lake, a special program was launched. One of the key tasks is to restore the submerged vegetation in the lake. Some of the submerged macrophyte species re-established in the region of Lake Taihu have decomposed and died off, and dissolved oxygen in bottom water was low(1~2 mg/L) at the same time. An outdoor experiment was conducted in artificial ecosystem to illuminate the relationship between the growth of Vallisneria spiralis and the low dissolved oxygen of water. The treatment included two dissolved oxygen concentrations (low oxygen and high contrast oxygen) and two kinds of sediments. It is revealed that using bank sediment or sediment from central lake, low dissolved oxygen had no prominent effect on the growth of V. spiralis, but on the number and weight of tuber of the submersed plant. In low dissolved oxygen water, the root of V. spiralis growing in bank sediment became thin and their activity became weak. But, the root of the plant growing in central-lake sediment was not susceptive. It was proposed that other factors such as light play the key role on the growth of submerged plants in the lake and the effect of dissolved oxygen on aquatic macrophytes be a long time one.