新安江水库(千岛湖)湖泊区夏季热分层期间垂向理化及浮游植物特征

Vertical distribution of phytoplankton and physico-chemical characteristics in the lacustrine zone of Xin'anjiang Reservoir(Lake Qiandao) in subtropic China during summer stratification

2010年7月对亚热带特大型水库——新安江水库湖泊区水体的垂向物理、化学参数以及浮游植物群落进行了观测研究,并应用Water-PAM对水体浮游植物垂向光合作用参数进行了测定.研究结果表明:夏季该水库湖泊区在水下10～20 m处形成明显的温跃层,垂向pH值、溶解氧及浊度的变化同叶绿素a浓度呈现高度一致;夏季浮游植物群落以硅藻占绝对优势,水体表层以梅尼小环藻(Cyclotella meneghiniana)为主,表层以下其它各层均以巴豆叶脆杆藻(Fragilaria cro-tonensis)为绝对优势种,垂向分布表现为5～10 m区间为浮游植物高密度区域,温跃层以下浮游植物密度显著下降,水温分层可能是决定浮游植物垂向分布的重要因素之一.浮游植物最大光合效率从表层向下层逐步降低,实际光合效率最大值出现在垂向10 m区域.

The investigation on vertical distribution of phytoplankton and physical-chemical characteristics was conducted in the lacustrine zone during summer stratification in Xin＇anjiang Reservoir（ Lake Qiandao）. The Water-PAM Chlorophyll Fluorometer was used to obtain vertical profiles of phytoplankton photosynthesis. The results showed that depth of thermocline appeared between 10 -- 20 m. Besides, the vertical profiles of pH, dissolved oxygen and turbidity were in agreement with chlorophyll-a. In summer, the phytoplankton was dominated by Bacillariophyta, C. meneghiniana was dominant in surface layer, while F. crotonensis was abso- lutely dominant below the surface layer. High-density of phytoplankton was found around 5-- 10 m below the water surface. Howev- er, a sharp decline was observed for phytoplankton density below thermocline layer. Therefore, the thermal stratification might af- fect the vertical distribution of phytoplankton population. Phytoplankton maximum photosynthetic efficiency had a negative relation- ship with water depth and the actual maximum value of photosynthetic efficiency was determined at 10 m depth.