广西洪潮江水库浮游植物功能类群及其对环境因子响应

Phytoplankton Functional Groups and Their Response to Water Physiochemical Factors in Hongchaojiang Reservoir in Guangxi Province

研究洪潮江水库浮游藻类的功能类群及其与环境因子的关系,了解水库生态系统的结构和功能,为水库环境状况的评价及管理提供理论依据。于2018年夏(6月)和2019年冬(1月)对洪潮江水库9个采样点的理化因子和浮游植物功能类群进行研究。洪潮江水库在夏冬2个季节中共检测出浮游植物7门59属,分别归属于17个功能类群。Sn功能类群包含拟柱孢藻,是洪潮江水库的主要优势种,洪潮江水库较高的温度、磷限制环境以及较高的浊度是拟柱孢藻占据优势并在夏季产生水华的主要原因。功能类群L_(m)主要包含微囊藻,在部分采样点与拟柱孢藻共同占据优势,表明拟柱孢藻和微囊藻之间存在较大种间竞争。其他优势功能类群包括Lo(以多甲藻为主)、H(以鱼腥藻为主)、P(直链藻)、Y(隐藻属),均属于中-富营养到富营养型的种类。环境监测表明,洪潮江水库磷含量较低,氮磷比高达200,该水体可能为磷限制。水库夏季均温为30.5℃,冬季均温为13.6℃,夏季硝态氮、氨氮、溶氧含量和透明度显著低于冬季。皮尔森相关系数和RDA分析表明,浊度、高锰酸钾指数、TN、氨氮、DO、透明度等是影响大部分功能类群的主要环境因子,而上述环境参数中高锰酸钾指数、浊度与大部分功能类群呈正相关,TN、氨氮、透明度以及DO与功能群呈负相关。根据浮游植物功能类群的组成可以判断洪潮江水库为中、富营养化,而拟柱孢藻和微囊藻为优势的具有产毒潜力的蓝藻将会对水库水质安全产生威胁。

Hongchaojiang reservoir, in southern Guangxi Province, provides flood protection, hydropower, irrigation, fishery resources and recreation. In this study, we explored the characteristics of phytoplankton functional groups as well as their relationship with the physiochemical factors of the water in Hongchaojiang reservoir. The objectives were to understand the structure and function of the reservoir ecosystem and provide theoretical support for evaluating and managing water quality in Hongchaojiang reservoir. In June 2018(summer) and January 2019(winter), a field investigation of phytoplankton functional groups and physiochemical parameters of the water was conducted at 9 sampling sites representing the upper,middle and lower reaches of Hongchaojiang reservoir. Total phosphorus(TP) levels were low and the N/P ratio was as high as 200, indicating that P is the limiting nutrient. The average water temperature was30.5℃ in summer and 13.6℃ in winter. Levels of nitrate nitrogen(NO3-N),ammonium nitrogen(NH-N), dissolved oxygen(DO) and Secchi depth(SD) in summer were significantly lower than in winter. A total of 59 phytoplankton genera from 7 classes and 17 functional groups were identified during the investigation. The dominant functional groups were Sn, P, Lm, Lo, Y and H, and Cylindrospermopsis raciborskii(aka Raphidiopsis raciborskii) in the Sn functional group was the most dominant species in the reservoir. High temperature, high turbidity and a P-limited environment were the primary factors resulting in the dominance, and for summer blooms of C. raciborskii. Microcystis sp. of Lm functional group was co-dominant with C. raciborskii at S3 and S9, indicating the presence of intense competition between the two cyanobacteria species. Other dominant species, including Peridinium(Lo), Cryptomonas(Y),Anabeana(H) and Melosira sp.(P) indicate a mesotrophic to eutrophic environment and their percentages of total biomass were higher in winter than in summer. Pearson correlation and redundancy analysis show that turbidity, CODMn, TN, NH-N, DO and transparency were the primary environmental parameters affecting the distribution of most functional groups. Among these parameters, turbidity and CODMnwere positively correlated with functional group density, while TN,NH-N, DO and transparency were negatively correlated with the density of most functional groups. According to the composition of phytoplankton functional groups in Hongchaojiang reservoir, we concluded that the trophic status of Hongchaojiang reservoir was mesotrophic-eutrophic, and the potentially toxic C. raciborskii and Microcystis,with absolute dominance, threaten water quality safety.