利用大型围隔研究沉水植被对水体富营养化的影响

在严重富营养化的东湖设置大型围隔（20×29m）两个，并在其中引种沉水植物—菹草（PotamogetoncrispusL．），探讨了菹草的恢复对水体富营养化的影响。菹草的恢复，使两个大型围隔中的各种营养盐水平都显著地低于围隔外围的湖水（P＜0．01），溶解氧和透明度显著升高，电导率明显下降，即水质得到了明显的改善。又将其中一个围隔中已恢复的菹草全部收割并移出，在一个多月的期间，未被收割的围隔内水体中各种营养盐浓度比已收割围隔稍低，但未能达到统计学上的显著差异（P＞0．6），对水体浮游植物叶绿素a浓度也没有显著影响。即在短期（一个月左右）未使水质明显恶化。

EXPERIMENTAL STUDIES ON THE EFFECTS OF SUBMERSED MACROPHYTES ON THE EUTROPHICATION OF LAKE WATER USING LARGE-SIZED ENCLOSURES

Two large-sized enclosures (each 20 x 29m) were set up in the Shuiguo Hu Bay near the west end of the hypereutrophic Lake Donghu. At the beginning of the experiment (October 1995),no macrophytes were present in the enclosures and a submersed macrophyte, Potamogeton crispus, was introduced into both enclosures. In April 1996, P. crisp us became very abundant in both enclosures (The maximum 214-381gD. W / m2). Compared with lake water outside the enclosures, the reestablishment of P. crispus significantly decreased the concentrations of various nitrogen and phosphorus compounds and conduchvity, and increased significantly dissolved oxygen and transparency of the water in the enclosures (p<0.001). In April 7, P. crispus were removed from Encl. B. One month later, the concentrations of nutrients and chlorophyll a were only slightly higher in Encl. B than in Encl. A, and there was no statistically significant difference between them, i.e., the removal of P. crispus did not cause a significant deterioration of water quality within such a short period of time.