东海春夏季浮游植物群落生态特征及其影响因子分析

Ecological characteristics and influencing factors of phytoplankton community in spring and summer in the East China Sea

为了解近年东海浮游植物群落的生态学特征,通过2015—2017年5月(春季)和8月(夏季)对东海海域浮游植物和环境要素进行调查,分析了东海浮游植物群落结构特征及其与典型环境因子(水文、营养盐、COD_(Mn)、悬浮物浓度等)之间的关系。研究表明,春季浮游植物优势种主要由虹彩圆筛藻(Coscinodiscus oculus-iridis)、琼氏圆筛藻(Coscinodiscus jonesianus)和中肋骨条藻(Skeletonema costatum)组成,夏季的主要优势种为中肋骨条藻。受长江冲淡水、钱塘江、东海沿岸流等影响,东海近岸海域环境浮游植物数量明显高于东海大陆架海域。冗余度分析结果显示,2015—2017年春季,对调查海域浮游植物丰度影响较大的环境因子是活性磷酸盐;2015—2017年夏季,对研究海域浮游植物丰度影响较大的环境因子是无机氮、活性磷酸盐和化学需氧量。

In order to understand the ecological characteristics of phytoplankton community in the East China Sea in recent years,the structural characteristics of phytoplankton community in the East China Sea and its relationship with typical environmental factors(water temperature,nutrient content and structure,COD_(Mn) and suspended solids concentration)were analyzed by investigating the basic elements of phytoplankton and environment in the East China Sea in May and August from 2015 to 2017.Results showed that the nitrogen phosphorus ratio in the study area of the East China Sea in spring was 20-35.The dominant species of phytoplankton in spring were mainly composed of Coccinodiscus oculus-iridis,Coccinodiscus jonesianus and Skeletonema costatum.The ratio of nitrogen to phosphorus in summer was higher than that in spring and was much higher than 16∶1.The dominant species in summer was Skeletonema costatum.According to the investigation,the number of phytoplankton in the coastal waters was significantly higher than that in the continental shelf of the East China Sea.The redundancy analysis results showed that from spring of 2015 to 2017,the environmental factor that had a great impact on phytoplankton in the investigated sea area was active phosphate.From summer of 2015 to 2017,the environmental factors that had a great impact on phytoplankton in the investigated sea area were inorganic nitrogen,active phosphate and chemical oxygen demand.In S3 and S5 of the fishing ground in the Yangtze River Estuary,the transparency of the water body was high,and the content of inorganic nitrogen and active phosphate in the water body was relatively high,which provided a good nutritional condition for the large-scale propagation of phytoplankton.This phenomenon may be related to the thin layer distribution of phytoplankton in the Yangtze Estuary.According to the data from 2015 to 2017,the average abundance of phytoplankton in spring and summer was 3.0×10^(4) cell·L^(-1) and 2.7×10^(4) cell·L^(-1).Based on the data collected from the continental shelf survey network of the East China Sea from 1997 to 2000,the phytoplankton abundance in autumn was the highest(211.9×10~4 cell·m-3),followed by summer(50.4×10^(4) cell·m^(-3))and winter(11.4×10^(4) cell·m^(-3))and the lowest was in spring(2.0×10^(4) cell·m^(-3)).From 1997 to 2000,the average phytoplankton abundance of four seasons was 68.9×10^(4) cell·m^(-3).The coastal area of the East China Sea had a high abundance of phytoplankton due to the impact of the fresh water of the Yangtze Estuary,the Qiantang River and the coastal current of the East China Sea.The results of redundancy analysis(RDA)using Canoco software showed that in spring of 2015,the environmental factors that had a great impact on the distribution of phytoplankton in the study area were pH,DO and active phosphate.DO,pH and active phosphate environmental variables were positively correlated with RDA1.In summer,the environmental factors that had great influences on the distribution of phytoplankton in the study area were COD and active phosphate.Environmental variables such as COD,active phosphate,DO,inorganic nitrogen and pH were positively correlated with RDA1.In spring of 2016,the environmental factors that had great impacts on phytoplankton were water temperature,DO,inorganic nitrogen and COD.Environmental variables such as water temperature,DO,inorganic nitrogen and COD were positively correlated with RDA1.In summer,water temperature and inorganic nitrogen were the environmental factors that had great negative impacts on Skeletonema costatum.Environmental variables such as water temperature and inorganic nitrogen were negatively correlated with RDA1.In spring of 2017,the environmental factor that had a great negative impact on the dominant species of phytoplankton was active phosphate.The active phosphate environment variable was negatively correlated with RDA1.In summer,inorganic nitrogen was the most important environmental factor affecting Skeletonema costatum.Inorganic nitrogen environmental variables were positively correlated with RDA1.