长江口浮游植物群落特征及影响因素分析

Analysis of phytoplankton community characteristics and influencing factors in the Yangtze River Estuary

为了解长江口浮游植物的群落组成、结构特征、时空分布及关键影响驱动因子,基于2018—2020年8月(夏季)、11月(秋季)长江口浮游植物调查数据,运用群落多样性分析指标及广义加性模型(generalized additive models, GAM)探究了长江口浮游植物群落特征及与各影响因子间的关系。结果表明:本次调查共采集浮游植物8门99属185种,其中,硅藻门(Bacillariophyta)、蓝藻门(Cyanophyta)和绿藻门(Chlorophyta)是主要的浮游植物类群,优势种主要包括中肋骨条藻(Skeletonema costatum)、颗粒直链藻(Aulacoseira granulata)、具槽直链藻(Melosira sulcata)、小环藻(Cyclotella sp.)和衣藻(Chlamydomonas sp.)等,其中中肋骨条藻长期占绝对优势;在时间上,夏季浮游植物丰度和种类数显著高于秋季(P<0.05),但秋季浮游植物群落多样性指数和丰富度指数更高,分布更均匀;在空间上,浮游植物平均丰度整体上呈现东滩>南支>北支的分布格局;GAM分析显示,在夏季,水温(Tem)、酸碱度(pH)和氮磷比(TN/TP)是显著影响长江口浮游植物丰度分布的环境因子(P<0.05),其中TN/TP的贡献率最高(71.86%),在秋季,盐度(Sal)、溶解氧(DO)和化学需氧量(CODMn)是显著影响长江口浮游植物丰度分布的环境因子(P<0.05),其中DO的贡献率最大(48.48%)。研究表明,长江口浮游植物群落的组成、结构、时空分布及影响因素存在季节差异,本研究结果可为掌握长江口浮游植物资源动态提供参考依据。

In order to understand the composition and structural characteristics,spatiotemporal distribution pattern and key impact drivers of phytoplankton communities in the Yangtze River Estuary,the characteristics of phyto-plankton communities and the relationship between the characteristics of phytoplankton communities and influencing factors were explored based on the survey data of phytoplankton in the Yangtze River Estuary in August(summer)and November(autumn)from 2018 to 2020 by community diversity analysis indicators and generalized additive model(GAM).The results showed that a total of 185 species of phytoplankton were collected in 8 phyla,99 gene-ra,with the dominant species mainly including Skeletonema costatum,Aulacoseira granulata,Melosira sulcata,Cy-clotella sp.and Chlamydomonas sp.,and the main phytoplankton groups including Bacillariophyta,Cyanophyta and Chlophyta,in which Skeletonema costatum had long been overwhelming.There were significantly higher abun-dance and species of phytoplankton in summer than those in autumn(P<0.05).In autumn,however,phytoplank-ton communities showed higher diversity index and richness index and more evenly distributed.Spatially,the aver-age phytoplankton abundance showed the distribution pattern of East Beach>South Branch>North Branch as a whole.The GAM analysis indicated that water temperature(Tem),pH and total nitrogen to total phosphorus ratio(TN/TP)were the environmental factors(P<0.05)significantly affecting the abundance distribution of phyto-plankton in the Yangtze River Estuary in summer,with the maximal contribution rate of 71.86%from TN/TP.Sa-linity(Sal),dissolved oxygen(DO)and chemical oxygen demand(CODMn)were found to be the environmental factors(P<0.05)significantly affecting the abundance distribution of phytoplankton in the Yangtze River Estuary in autumn,especially the DO contribution up to 48.48%.The findings indicate that there are seasonal differences in the community composition,structure,pattern and influencing factors of phytoplankton in the Yangtze River Es-tuary,which provides references for understanding of the dynamics of phytoplankton resources in the Yangtze River Estuary.