摘要
通过连续对菹草生长过程的观测 ,用指数方程拟合了菹草从 10月中旬至第 2年 5月底的整个生长过程 (p<0 .0 0 2 ) ,设K=2 .5 kg/ m2时 ,用 L ogistic方程拟合了从 3月到 5月底的生长过程 (p<0 .0 0 0 )。通过 7月底至 8月初、10月、翌年 3月和 5月份对一个菹草型水库和无或有不同规模水草的 5座水库水生生物的周年调查发现 :(1)菹草型水库 TP最高峰的月份比其它水库的推迟 ,其它水库 10月份 TP最高 ,而菹草型水库 3月份最高 ;(2 )菹草型水库浮游植物最高峰的月份比无水草水库的推迟 ,无水草水库出现在夏季 (7～ 8月份 ) ,草型水库的出现在秋季 (10月份 ) ;(3)菹草型水库 3月份浮游植物生物量明显高于其它水库的 ,其硅藻占据更高的优势度 ;(4 )菹草型水库和其它水库之间的总磷和浮游植物数量的年平均值无明显差别 ;(5 )不同水库藻类数量年平均值与 TP年平均值相关极显著 (p<0 .0 0 5 ) ,而 TP又与氯化物 (Cl)相关极显著 (p<0 .0 0 5 ) ;(6 )水草的存在使p H略有提高 。
Several studies have demonstrated the influence of submerged macrophytes on eutrophication or water quality with different results. To assess the effect of a submerged macrophyte, one should evaluate the ecosystem throughout a year in combination with the growth curve of the plant. The growth curve of Potamogeton crispus was determined from seven investigations from October 2002 to May 2003 in a reservoir with 70% of area covered by P. crispus. The effects of the grass on water quality were assessed by analyses of fluctuations in total phosphorus (TP), phytoplankton, and pH in the reservoir and in five other reservoirs with 0～30% of areas covered by P. crispus, Myriophyllum spicatum or a combination of both in July and October 2002, and March and May 2003. All six reservoirs are located in the Yellow River Delta (38° N, 118° E). The grass growth equation from October to May was regressed as GB=34.1×e^(0.018t) (p<0.002), where GB refers to the wet weight of grass per m^2, and t refers to days after germination. The equation from March to May was GB=25001+e^(14.97-0.08338t)(p<0.000). The fluctuations of TP, phytoplankton, and pH in six reservoirs exhibited (1) maximum TP in the reservoir dominated by P. crispus (RDP) occurred in March rather than October; (2) maximum cell abundance and maximum biomass of phytoplankton in RDP and the reservoirs with more than 25% of area covered by macrophytes occurred in October rather than in July; (3) of the values of phytoplankton in March, the RDP contained the highest biomass, dominated by diatoms; (4) annual average TP and cell abundance of phytoplankton in RDP did not differ significantly from the other five reservoirs; (5) annual average cell abundance of phytoplankton correlated significantly positive with TP (p<0.005) in all reservoirs, and annual average TP correlated significantly positive with chloride concentration (Cl) (p<0.005); (6) submerged macrophytes could stabilize pH and appreciably increased annual average pH; (7) in reservoirs except for the grassless and shallow one, phytoplankton cell abundance correlated significantly with zooplankton abundance. The result indicates that the submerged macrophyte P. crispus grows mainly from March to May when the temperature ranges from 7 to 25℃, with a maximum biomass of 2.5kg/m^2. Two species of submerged macrophytes in these reservoirs can only delay the platforms in the yearly curves of TP and abundance of phytoplankton while buffering the effect of eutrophication; they cannot control eutrophication because their decay or germination may increase pelagic nutrients in late autumn and early spring during diatom blooms. The trophic state is regulated by the concentration of TP. Excessive seasonal blooms of the grass can decrease the circulation of nutrients and reduce ecosystem productivity. Moreover, there is a risk that flourishing submerged macrophytes could increase pH so much that it might cause a change in ecosystem structure. To reduce the coverage of P. crispus in a reservoir by fish predation, both herbivorous fish and omnivorous fish should be used because of the high growth rate of the grass in spring.
出处
《生态学报》
CAS
CSCD
北大核心
2004年第5期888-894,共7页
Acta Ecologica Sinica
基金
胜利石油管理局滨河供水公司资助项目
关键词
菹草
生长方程
浮游植物
总磷
Potamogeton crispus
growth equation
phytoplankton
total phosphorus (TP)
