湖泊科学   2017, Vol. 29 Issue (3): 625-636. 0

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LI Yimiao, LI Maotian, AI Wei, LUO Zhang, HU Jin, HOU Lijun. Distribution, relationship and significance of phytoplankton, chlorophyll-a and environment variables in spring season of the Zhelin Reservoir, Jiangxi Province. Journal of Lake Sciences, 2017, 29(3): 625-636. DOI: .
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2016-05-11 收稿
2016-09-05 收修改稿

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(华东师范大学河口海岸学国家重点实验室 上海 200062)

Distribution, relationship and significance of phytoplankton, chlorophyll-a and environment variables in spring season of the Zhelin Reservoir, Jiangxi Province
LI Yimiao , LI Maotian , AI Wei , LUO Zhang , HU Jin , HOU Lijun
(State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, P.R.China)
Abstract: Zhelin Reservoir is a large canyon-reservoir in the midstream of the Yangtze River, and the storage capacity is 79.2×108 m3 and length is 115 km. Through measurements on a moving vessel and at fixed-point sites in the Zhelin Reservoir in April, 2015, the distribution of phytoplankton, chlorophyll-a (Chl.a) concentration and main environment variables (including dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), dissolved silicon (DSi), water temperature, turbidity, dissolved oxygen (DO)) were analyzed. The redundancy relationship of phytoplankton taxa and environmental variables was analyzed using the software CANOCO 4.5. The results showed that, 1) the reservoir water was categorized as a middle-status in nutrients. There were 34 main phytoplankton species in the surface (the cell density of which exceeding 1000 cells/L), and the average biomass of reservoir was 0.41 mg/L. The dominant algae (dominance be equal or greater than 0.02) were the diatoms and cyanobacteria. DIN, DIP, DSi and water temperature can impact on the structure of algae, and the four factors were explained for more than 60% variation of the algal structure. 2) The reservoir had a significant phenomenon of subsurface chlorophyll maximum (SCM). The depth of SCM appears at the water depth from 3 to 8 m, and the thickness is about 2-7 m. The Chl.a in the SCM layer is 25.2%-74.1% among the total in the vertical. The algae in the SCM layer absorbed the nutrients, resulting in decreased concentrations of DIN, DIP and DSi and the increased DO concentration. 3) The reservoir had significant biological and biochemical filtering effect for the DSi. About 11% to 12% DSi were absorbed by organisms in the middle and upper area of in the reservoir, and accumulating about 21% DSi was absorbed by algae from upstream to downstream. 4) Nitrogen and phosphorus emissions by human activities have a serious impact on the ecology and water quality of the reservoir and the adjacent county region. The concentrations of Chl.a and DIP in the region is about 2.9 times and 3 times higher than that in the natural region of the reservoir, respectively.
Keywords: Phytoplankton    chlorophyll-a    subsurface chlorophyll maximum    biological and biochemical filtering    Zhelin Reservoir

1 样品与方法 1.1 样品采集与分析

 图 1 柘林水库位置、采样航线和采样点位分布 Fig.1 Sampling route and sites in the Zhelin Reservoir

 $Y = {f_i}({n_i}/N)$ (1)

 $TLI\left( \sum \right) = \sum\limits_{j = 1}^m {{W_j}} \cdot TLI(j)$ (2)

1.2 藻类、Chl.a与环境因子的冗余分析

2 结果与分析 2.1 浮游藻类的组成与空间分布

 图 2 柘林水库4个采样点的细胞丰度和生物量 Fig.2 Cell density and biomass of four sampling sites in the Zhelin Reservoir
2.2 Chl.a浓度的空间分布

 图 3 柘林水库水体Chl.a浓度的纵向分布 Fig.3 Longitudinal distribution of chlorophyll-a concentration in the water of Zhelin Reservoir

 图 4 柘林水库水体Chl.a浓度与环境因子的垂向分布 Fig.4 Vertical distribution of chlorophyll-a concentration and environment variables in the water of Zhelin Reservoir
2.3 环境因子的空间分布 2.3.1 生源要素的空间分布及其与Chl.a浓度的相关关系

 图 5 柘林水库水体Chl.a浓度与营养盐浓度的相关关系 Fig.5 Interrelation of chlorophyll-a concentration and nutrition concentrations in the water of Zhelin Reservoir
2.3.2 环境要素的空间分布

2.4 水库营养状态

3 讨论 3.1 藻类与环境因子的冗余分析

 图 6 浮游藻类(细胞丰度)与环境因子的RDA排序图 Fig.6 Correlation plots of RDA on the relationship between the environment variables and cell density of phytoplankton taxa
3.2 Chl.a浓度与环境因子的相关分析 3.2.1 人类排放对Chl.a和营养盐浓度的影响

3.2.2 Chl.a浓度的SCM特征及与营养盐浓度垂向分布的关系

3.2.3 Chl.a浓度与WT、DO浓度和TD的垂向分布关系

3.2.4 柘林水库水体Chl.a浓度的SCM层发育机理

Chl.a浓度的SCM现象早在1935年就有报道[38]，1958年Sverdrup用真光层深度(Zeu，表面光强减到1 %的深度)与混合层深度(Zmix，水体温度或密度沿深度变化很小的垂直混合充分的水层)的比值变化描述湖泊SCM的产生机理，提出比值的临界值理论，当水体Zeu/Zmix高于临界值(混合层深度浅于临界层深度)，藻类迅速生长，反之则抑制其生长[39].该理论广泛用于探讨水库SCM的机理[40-41].该理论的本质是浮游植物初级生产力与水体垂向层化稳定度的关系，而水体垂向层化稳定度的核心是温跃层的存在与否[42-43]，水库中SCM形成首先有赖于温跃层的存在与否，温跃层阻碍水体的上下混合交换，在层内形成相对静止稳定的环境[44]；其次浮游植物对弱光的适应原理导致大部分种类的藻类在位于水体表面光强1 % ~12 %的水下层(光饱和层)光合作用最强[45-47]；另外温跃层内营养盐自底部向上的输送及营养盐沉降累积，导致温跃层内尤其是下部区域营养盐的富集，为藻类生长提供了充足的营养来源[48].上述温跃层、藻类对弱光的适应原理及营养盐富集机制相互作用，致使海洋、湖泊与水库中普遍存在Chl.a浓度的SCM现象.从上述讨论可以看出，对于柘林水库而言，柘林水库温跃层的存在也是与Chl.a浓度的SCM层发育密切相关，温跃层的存在造成层内稳定静止的环境，同时也阻碍了营养盐的上下交换，致使营养盐在沉降作用下在层内出现富集(图 4).另外，由于水库光衰减系数远比海洋(0.04~0.2)要高，如果假定水库光衰减系数为0.6，水表面光强(调查时为晴天)为100000 lux，根据光衰公式(Lambert-Beer Law)[49]Id=I0·ekd(Id为深度d处的光强，I0为水表层晴天光照，k为光衰系数)，则光强衰减到10 %的深度约为4.6 m.因此，根据浮游植物对弱光的适应原理，柘林水库浮游藻类在水下4.6 m左右光合作用最强.因此，本研究表明，温跃层是水库SCM发育的前提，藻类对弱光的适应性是SCM发育的生态学基础，而温跃层内营养盐富集机制是SCM发育的物质基础，三者相互作用，形成SCM现象.

3.3 水库的自净能力及营养盐的过滤器效应

3.4 水库富营养化水平

4 参考文献