千岛湖冬季浮游植物光合活性

The photosynthetic activity of phytoplankton in Qiandao Lake in winter

千岛湖是我国十大水库之一，也是长三角地区最重要的战略饮用水源地。于2010年1月份对其水质及浮游植物群落进行调查，并对浮游植物的光合作用活性进行测定。千岛湖冬季水质指标除总氮外均达到水环境功能区要求，冬季水体存在明显的水温分层及水体物理、化学指标分层现象，不同点位水温分层的水深有所不同，温跃层基本在25～40m。千岛湖冬季浮游植物种类较多，检测到有硅藻、蓝藻、绿藻、隐藻、甲藻、金藻，丰度上以硅藻为主，优势类群为直链藻属和小环藻属，硅藻约占浮游植物总密度的60％以上；叶绿素a含量较低在1．4～5．7μg·L^-1。根据Water-PAM和Phyto-PAM测定的结果，千岛湖冬季浮游植物具有较强的光合作用活性，硅／甲藻的光合作用活性最大，其次为蓝藻，绿藻最低；浮游植物光合作用活性存在空间差异，街口区域的浮游植物光合活性最高，三潭岛最低；浮游植物的光合活性在垂向上也存在差异，大坝处Fv／Fm在20m左右达到最大，小金山和三潭岛在30m处达到最大值，街口Fv／Fm比其他3处高，且水深较浅垂向变化不明显。千岛湖浮游植物光饱和强度在700～1000μmol·s^-1·m^-2，光照适应幅度较宽。

Qiandao Lake is one of China＇ s ten major reservoirs and the most important strategic source of drinking water in the Yangtze River Delta region. An investigation was conducted on the water quality and the community structure of phytoplankton at 8 sampling sites in Qiandao Lake of Southeast China in January 2010. The photosynthetic activity of phytoplankton was measured by Phyto-PAM （Pulse Amplitude Modulation） and Water-PAM. The water quality indicators were in accordance with the requirements of the water environmental function zones except TN. There was a stratification of water temperature, physical and chemical indicators in winter. The thermocline depth was between 25 - 40 m. Diatoms, cyanobacteria, green algae, cryptophyta, dinoflagel- lates, and golden algae were observed in winter. Dominant phytoplankton groups were Diatoms （Melosira and Cyclotella）. They accounted for 60% of the total density. Chlorophyll a concen- tration varied from 1.4 to 5.7μg·L^-1. The results suggested that the photosynthetic activity of phytoplankton was active in winter. Diatoms had the maximum photosynthetic activity, secondly cyanobaeteria, and finally green algae. There were significant horizontal and vertical spatial differences in photosynthetic activity. The light saturation intensity of phytoplankton in Qiandao Lake ranged between 700-1000μmol · s-1 · m-2. The results also suggested that the high photo- synthetic activity of diatoms relate to the outbreak of diatom bloom in Qiandao Lake in spring.