浅水富营养化湖泊浮游植物对沉积物再悬浮作用的响应机理研究

The significant characteristics of large shallow lake is frequent sediment resusepension, which has been recognized as an important factor regulating the structure and function of lake ecosystems. The resuspension of sediment changed nutrients content in water and under water light climate. Although light and nutrient factors influence the phytoplankton growth and biomass in large shallow lake, little is known about the mechanism of the effects of sediment resuspension on the physiology characteristics（fluorescent characteristic，photosynthetic efficiency esterase activity）and the biomass of phytoplankton. In this project, Phyto-pam and 14C will be applied to determine the fluorescent characteristic and the photosynthetic efficiency of the phytoplankton during sediment resuspension. The field observation in situ, the field mesocosms observation and two lab experiments will be carried on to study the effects of sediment resuspension on the phytoplankton physiology characteristics and to evaluate the net phytoplankton biomass increment under the different intensity of resuspension. And the effects of algae in sediment involved into water column on the phytoplankton will be discussed. This research makes much sense to further understand the mechanism of sediment resuspension influence on phytoplankton and reveal the relationship between sediment resuspension and the cyanobacterial blooms in shallow eutrophic lake.

沉积物再悬浮频繁发生是大型浅水湖泊的重要特征，能调节湖泊生态系统的结构和功能。沉积物再悬浮改变了水体中营养盐和水下光场条件，而营养盐和光两因素对水体浮游植物生理特征和生物量的影响机理目前研究涉及较少。本项目通过野外原位观测、半原位观测和室内模拟实验，利用藻类叶绿素荧光仪和14C测定初级光合效率的先进方法，研究浅水富营养化湖泊沉积物再悬浮对浮游植物微观特征（生理特征、荧光特性、光合效率、酯酶活性等）的影响，评估不同强度沉积物再悬浮对浮游植物生物量的净增量，探讨沉积物再悬浮过程中沉积物中藻体对水体浮游植物的影响机理。研究结果有助于深入了解沉积物再悬浮对浮游植物的影响机理，为揭示浅水富营养化湖泊中沉积物再悬浮与蓝藻水华之间的关系提供理论依据。

沉积物是湖泊重要的营养盐库藏。太湖由于湖大水浅，频发蓝藻水华，因此沉积物再悬浮对湖泊水华的影响机理研究显得尤为迫切。本项目通过野外原位观测和室内模拟实验，利用藻类叶绿素荧光仪和14C测定初级光合效率的方法，研究了沉积物的再悬浮特征，以及沉积物再悬浮对浮游植物生长的影响，进而评估了再悬浮过程中底栖藻对上覆水体浮游植物生物量的贡献，进而探讨沉积物再悬浮对浮游植物的影响机制。研究发现：（1）太湖中波浪是沉积物再悬浮的主要动力，波切应力越大，沉积物发生再悬浮的强度越大，水体中悬浮颗粒物的浓度越高，沉积物的扰动深度越深。（2）间歇性地动力扰动能脉冲式大量地向上覆水体补给营养盐，以颗粒态为主。根据水体中碱性磷酸酶的特性，结合太湖营养盐限制性研究，可发现水体浮游植物生长所需的氮供给充足，而磷缺乏。浮游植物的初级生产力和比光合速率的结果表明，动力扰动环境能缓解了水体浮游植物生长磷受限的状态，并能维持水体一定的浮游植物生物量。动力扰动环境不利于浮游植物的光合作用。（3）沉积物再悬浮对底栖藻的影响研究发现，沉积物再悬浮将底栖藻或者沉积物中藻细胞带入上覆水体，进入上覆水的底栖藻，在水体中无浮游植物或者浮游植物生物量极低的情况下，能迅速增加并形成一定的规模。底栖藻对上覆水体的贡献，生物量以硅藻为主，而浮游植物的细胞丰度则以蓝藻的数量最多。研究结果为揭示浅水富营养化湖泊中沉积物再悬浮与蓝藻水华之间的关系提供理论依据。