东江三角洲河网浮游植物粒径特征研究

Study on particle size characteristics of phytoplankton in the Dongjiang Delta River network

于2021-2022年春夏秋冬四个季节对东江三角洲河网的浮游植物叶绿素a浓度及粒径结构(小型Micro,微型Nano,微微型Pico)进行了季节性调查研究。结果显示夏季浮游植物叶绿素a浓度均值明显高于其他季节。粒径组成结果显示,小型和微型浮游植物叶绿素a浓度占比较高,二者浓度占比之和的年平均值为97.25%。粒径结构的季节特征显示,Micro浓度占比季节差异显著,Nano和Pico浓度占比季节差异不显著。空间特征显示,靠近珠江口的站位一般呈现出Nano浓度占比大于Micro浓度占比的规律。冗余分析(Redundancy analysis,RDA)显示,Micro浓度占比与水温、pH和河宽呈正相关关系,Nano浓度占比与透明度呈正相关关系。聚类分析结果显示,调查站位被明显分成了上游和下游两大类群,两大类群间浮游植物粒径组成差异显著,其中两类群中Micro、Nano叶绿素a浓度占比差异显著,Pico叶绿素a浓度占比差异极显著。另外,研究发现,两类群间差异显著的物理因子主要为盐度,差异显著的化学因子主要为pH和TP。结合RDA分析结果,推测盐度和pH是影响东江三角洲浮游植物粒径组成空间分布的关键环境因子。

Phytoplankton of different particle sizes have different growth rates,nutrient uptake rates,sedimentation characteristics,and the next step of energy flow in the food web,and each occupies an essential position in the ecosystem food chainMost studies on phytoplankton particle size structure are related to marine ecosystems,and relatively few studies on phytoplankton particle size structure in freshwater ecosystems have been reported We used a field survey to investigate the phytoplankton chlorophyll-a concentration and particle size structure(Micro-phytoplankton,Nano-phytoplankton,Pico-phytoplankton)in the Dongjiang Delta in four seasons from 2021 to 2022 to understand the particle size structure of primary producers in the Dongjiang Delta waters,and to lay the foundation for the water environmental protection and restoration of the typical deltaic river network in the Great Bay Area Our study demonstrated that chlorophyll-a concentration was significantly higher in summer than in the other three seasons Micro-and nano-phytoplankton chlorophyll-a as dominant components accounted for 97.25%of total chlorophyll-a Micro-phytoplankton chlorophyll-a exhibited a clear seasonal pattern,while the proportion of Nano-and Pico-phytoplankton chlorophyll-a did not differ significantly across seasonsSpatially,stations adjacent to the Pearl River Estuary having a higher proportion of Nano-phytoplankton chlorophyll-a than Micro-phytoplanktonRDA(Redundancy analysis)manifested that the proportion of micro-phytoplankton chlorophyll-a was positively correlated with water temperature,pH,and river widthIn contrast,the proportion of Nano-phytoplankton chlorophyll-a was positively correlated with transparencyInvestigation stations were divided into two groups upstream and downstream by cluster analysis.The particle size structure of phytoplankton varied remarkably between the two groups,reflected by the significant difference in the proportion of Micro-,Nano-and Pico-phytoplankton chlorophyll-a between groupsIn addition,physical factors,including conductivity,salinity,and total dissolved solids,were significantly different between the two groups,and the chemical factors with significant differences were pH,TP and PO 3-4 Combined with RDA analysis,it was speculated that salinity and pH might be critical environmental factors affecting the spatial distribution of phytoplankton particle size structure in the Dongjiang DeltaThis study screens the critical ecological factors affecting the spatial distribution of phytoplankton size composition in the Dongjiang Delta,providing a theoretical basis for anthropogenic regulation of phytoplankton community composition in the water.