太原汾河蓄水区浮游植物细胞密度及其与营养元素的关系

水体营养元素是影响水体生态系统的重要因素,决定着水体中不同的浮游生物群落结构,也是评价水质和水体营养状态的重要指标。对太原汾河蓄水区9个样点浮游植物和各项水环境及营养元素进行了调查与分析,调查期间发现(1)该流域蓝藻和绿藻为主要优势类群,即构成了以蓝-绿藻门为主要的浮游群落。平水期与丰水期优势种均以蓝藻门的微小色球藻(Chroococcus minutus)、微小平裂藻(Merismopedia tenuissima)、小颤藻(Oscillatoria tenuis)、铜绿微囊藻(Microcystis aeruginosa)为主,其丰度分别占平水期和丰水期藻细胞总数的42.95%和59.24%。叶绿素a含量随地理位置变化明显,中下游显著高于上游。(2)太原汾河蓄水区水质均达到富营养状态。由于太原汾河蓄水区沿途的生活垃圾、污水的不合理排放,导致汾河中总氮、总磷等指标偏高,最终导致整个水体处于轻度富营养状态或中度富营养状态。(3)叶绿素a含量与水温、总氮、总磷呈显著正相关,与有机物含量呈极显著正相关,总磷的影响最为明显,说明磷可能是该地区浮游植物生长的限制因子。

Relationship between the growth of phytoplankton and the distribution of nutrients in the Fenhe water storage area of Taiyuan

Physicochemical factors and nutrients are important factors affecting aquatic ecosystems. Differences in physicochemical and nutrimental factors determine variation in phytoplankton community structure. Therefore, evaluation of water quality and nutrient status is necessary. Since 2015, we have studied the phytoplankton, and the physicochemical and nutrimental factors of the Fenhe water storage area. The results showed that (1) Cyanophyta and Chorophyta constituted the majority of the plankton community in the regions studied. Throughout the year, Cyanophyta was the most abundant phylum of planktonic algae. The dominant species, including Chroococcus minutus, Merismopedia tenuissima, Oscillatoria tenuis, and Microcystis aeruginosa, all of accounted for 42.95% and 59.24% of the algal community during the wet season and the dry season, respectively. Simultaneously, the concentration of chlorophyll-a revealed strong temporal and spatial variation in the Fenhe water storage area of Taiyuan, (annual mean:38.13mg/L; range:17.04-84.60mg/L). The chlorophyll-a concentration during the wet season was significantly higher than that in the dry season. During the wet season and the dry season, the spatial distribution patterns of chlorophyll-a were similar, increasing from upstream to downstream. (2) The water quality indicated eutrophication in the studied area. With rapid socio-economic development, increase in population and industrial enterprises, and urban-scale expansion, multiple test sites near the city center revealed that high levels of household-generated garbage, sewage, and industrial waste discharge into the Fenhe water storage area, owing to the lack of strict control measures. Total phosphorus and the other indicators were on the higher side, indicating that the water body is in mild or moderate eutrophic state (Chaicun Bridge, Shengli Bridge, Yingze Bridge, and Changfeng Bridge areas). In addition, at one point, some sites reached a severe eutrophic state (Nanneihuan Bridge, Jifen Bridge, Nanzhonghuan Bridge, and Jiuyuanshahe Bridge), which resulted the destruction of the ecological environment. (3) Chlorophyll is essential for photosynthesis. Measuring chlorophyll-a concentration could reflect the phytoplankton biomass and water quality status. The species composition of the phytoplankton community was closely correlated with chlorophyll-a content, dynamic variation of the physical and chemical index, and comprehensive index of water body. The correlation and principal components analyses revealed significant positive correlation of chlorophyll-a concentration with temperature, total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD), and permanganate index (COD_Mn). Further, phosphorous might be a limiting factor, as indicated by its strong effect on phytoplankton abundance.