Abstract:

The concept of functional groups, which categorizes phytoplankton species based on their similar morphological, physiological, and ecological characteristics, has been widely adopted to assess and predict changes in aquatic environments. The functional grouping methods have been wildly applied in lakes and reservoirs, while their application in tidal river networks has been limited due to the complex hydrodynamic processes and mass transport involved. Herein, systematic surveys on water quality and phytoplankton were carried out, and the effects of tidal action were studied in the hinterland of the Pearl River Delta during the low and high water periods in 2022. As a result, a total of 127 phytoplankton species belonging to 25 functional groups were identified. The average density of the low water period (January) and high water period (July) was 24.0×10⁵ ind?L^?1 and 52.7×10⁵ ind?L^?1, respectively. The predominant functional groups were P, J and MP in the low water period and shifted to J, P and S1 in the high water period which demonstrated obvious seasonal dynamics (q= ?12.636, P=0.000) but no significant difference between the tidal process (q= ?0.858, P=0.545). According to the results of redundancy analysis, the dominant functional groups were positively correlated with permanganate index, total phosphorus, total nitrogen, turbidity and channelization degree, and negatively correlated with dissolved oxygen, transparency and vegetation coverage. The similarity of phytoplankton structure among sampling sites was affected by distance and tide during the low water period, while the influence of dams became more prominent during the high water period due to increased upstream runoff. The results of cluster analysis based on phytoplankton functional groups were basically consistent with eutrophic evaluation using a logarithmic power function. The Shannon-Wiener index showed similar variations with Margalef index (r=0.933, P=0.000), although no significant correlation was found with the Pielou index (r=0.203, P=0.187). The overall assessment indicated that the water bodies in the tidal river network were in the meso-eutrophic state, with slightly better water quality during the high water period compared to the low water period. This study provides valuable insights into understanding the response of phytoplankton functional groups to water ecosystems and offers a scientific foundation for water ecological management and protection in tidal river networks.

Key words: tidal river network, phytoplankton, community structure, functional groups, spatio-temporal variation

摘要：

将形态、生理和生态特征相似的浮游藻类归为一组提出的功能群理论，可以从物种功能性的角度评价，更好预测水生态系统的变化。然而，目前该理论多应用于湖泊和水库，在复杂且受潮汐影响的感潮河网，浮游藻类功能群的研究相对不足。以中国大型感潮河网区珠江三角洲河网的腹地为研究区域，分析不同水期和涨退潮对该区域浮游藻类功能群的影响，探讨其时空变化特征及指示作用。结果显示，研究区域水体中共鉴定出浮游藻类127种，隶属于25个功能群，对应枯水期（1月）和丰水期（7月）的平均丰度分别为24.0×10⁵ ind?L^?1和52.7×10⁵ ind?L^?1。枯水期的优势功能群为P、J、MP，而丰水期的优势功能群为J、P、S1。浮游藻类的群落结构在不同水期有显著差异，但在涨退潮无显著差异，优势功能群组成一致。冗余分析结果表明，优势功能群与高锰酸盐指数、总磷、总氮、浊度、渠道化程度呈正相关，与溶解氧、透明度、植被覆盖度呈负相关。各样点浮游藻类功能群组成的相似性在枯水期主要受样点间的距离和潮汐的影响较大，而在丰水期受闸坝阻隔的影响更显著。基于功能群组成的聚类分析结果与基于水质指标的富营养评价结果一致。浮游藻类的Shannon-Wiener指数与Margalef指数表现出相似的变化趋势（r=0.933，P=0.000），但与Pielou指数的相关性不显著（r=0.203，P=0.187）。综上，研究区域水体现正处于中-富营养型，丰水期水质稍好于枯水期。该研究可为了解感潮河网区浮游藻类功能群对水生态系统变化的响应提供参考，为感潮河网水生态管理和保护提供科学依据。

关键词: 感潮河网, 浮游藻类, 群落结构, 功能群, 时空变化