南亚热带磷限制水库中浮游植物群落对氮磷比变化的响应

Responses of Phytoplankton Communities to N/P Ratio Changes in Phosphorus-limited Subtropical Reservoir in Southern China

摘要:

为了解P限制水体中浮游植物群落对N、P营养盐的响应，通过添加N、P营养盐设置N/P梯度，对广东省流溪河水库中的浮游植物群落进行了研究。结果表明，添加N、P显著促进浮游植物的生长，浮游植物群落受P盐的影响比N盐显著；藻类的种属特异性导致浮游植物群落对氮磷营养盐的响应不一致，浮游植物总丰度与N/P比值不相关，其中隐球藻（Aphanocapsa sp.）、拟柱胞藻（Cylindrospermopsis raciborskii）和假鱼腥藻（Pseudanabaena sp.）等蓝藻适合在高N高P条件下生长，双对栅藻（Scenedesmus bijuga）等绿藻优势种偏好中N高P环境，而曲壳藻（Achnanthes sp.）、小环藻（Cyclotella sp.）等硅藻在低N低P的环境下占据优势；P浓度为0.8~2.0 μmol/L时存在诱导浮游植物碱性磷酸酶活性的阈值，当P浓度大于2.0 μmol/L时则抑制酶活性；P浓度为2.0 μmol/L可能是浮游植物维持生长的最适浓度，浮游植物N/P维持动态平衡；藻细胞N/P、C/P与水体P浓度、N/P呈显著正相关，而藻细胞C/N受N影响更明显（P<0.05）。这为热带亚热带水库的水质管理提供了理论参考。

关键词:浮游植物群落;氮磷比;碱性磷酸酶;藻;元素

Abstract:

In order to understand the response of phytoplankton community in P-restricted water from Liuxihe Reservoir in Guangdong Province to different N/P ratios, the structure of phytoplankton community was studied by adding N and P to create a gradient of N/P. The results showed that the growth of phytoplankton had been promoted significantly with the addition of N and P, and the effects of P was greater than that of N. The species specificity of phytoplankton led to the inconsistent response of phytoplankton community to nitrogen and phosphorus nutrients, phytoplankton abundance was not correlated with N/P ratio. Cyanobacteria, such as Aphanocapsa sp., Cylindrospermopsis raciborskii and Pseudanabaena sp., was more favored in conditions with high level of N and P. Dominant species of green algae, Scenedesmus bijuga preferred medium N and high P. Bacillariophyceae, such as Achnanthes sp. and Cyclotella sp. had advantages in environment with low N and low P. The threshold of P concentration for alkaline phosphatase activity (APA) ranged from 0.8 to 2.0 μmol/L. When P concentration was above 2.0 μmol/L, APA was inhibited, and the optimal P concentration for phytoplankton to maintain growth may be around 2.0 μmol/L, and the ratio of cellular N/P reached equilibrium. The cellular N/P and C/P were significantly positively correlated with supplied P concentration and supplied N/P ratio, while cellular C/N was more correlated with supplied N (P<0.05). So, these would provide a theoretical reference for water quality management in tropical and subtropical reservoirs.

Key words:Phytoplankton community;N/P ratio;Alkaline phosphatase;Phytoplankton;Element