长江口浮游植物群落特征及其与环境的响应关系

根据2009年4月、8月、11月对长江口30个站位的调查,分析了浮游植物群落结构的时空变化及其与环境因子的响应特征. 共鉴定出浮游植物8门95属330种,主要优势种是硅藻和甲藻,其中中肋骨条藻占绝对优势. 浮游植物细胞丰度呈单周期季节性变化,夏季为高峰期,长江口近海区为高值区. 浮游植物群落多样性11月最高,主要分布在长江口过渡水域. 浮游植物群落可分为四大类群,各区域不同季节种类组成具有显著差异. CCA(典范对应分析)显示,浮游植物群落与环境因子密切相关,并且其响应机制存在季节性差异.硅藻细胞丰度4月与ρ(NO₃--N)、ρ(COD_Mn),8月与ρ(SiO₄4--Si)、ρ(NO₃--N)、ρ(PO₄3--P),11月与透明度呈显著正相关(P<0.01)；11月与ρ(PO₄3--P)、ρ(SiO₄4--Si)呈显著负相关(P<0.01). 甲藻细胞丰度4月与ρ(NH₄+-N),8月与ρ(COD_Mn),11月与透明度、ρ(NO₃--N)呈显著正相关(P<0.05). 长江口环境因子的改变影响浮游植物群落结构的时空变化,各季节引起浮游植物群落结构变异的驱动因素存在差异. 

Phytoplankton Community Structure in the Yangtze River Estuary and Its Relation to Environmental Factors

Three cruises were conducted in the Yangtze River estuary from April to November in 2009. The density and composition of phytoplankton were determined in water samples collected at thirty sampling sites. Totally 8phyla, 95genera and 330species were identified in these samples. Diatoms and dinoflagellates, especially Skeletonema costatum, were the dominant species at most sites. The abundance of phytoplankton in seawater decreased with the increase of distance from Yangtze River and a bloom was observed in the summer of 2009. By calculating the diversity index (H), Yangtze River transition water has the largest phytoplankton diversity. The maximum value of H in the sampling area occurred in November. Phytoplankton in the estuary of Yangtze River could be divided into four groups and a significant difference of phytoplankton composition was observed in three sampling seasons. CCA ordination analysis indicated that environmental factors play important roles in controlling the phytoplankton community structure, while the controlling factors vary with seasons. The primary factors affecting the structure of diatom community were identified to be COD_Mn and NO₃--N content in April, to be SiO₄4--Si, NO₃--N and PO₄3--P content in August, and to be PO₄3--P and SiO₄4--Si in November. Contents of NH₄+-N, COD_Mn, and NO₃--N and the transparency were the main factors affecting the structure of dinoflagellates in April, August and November, respectively. These results indicated that environmental factors play important roles in the seasonal and spatial variations of phytoplankton community structure in Yangtze River estuary, and the major driving factors changed with seasonal changes.