夏季长江口—东海陆架大中型浮游生物分布特征及影响因素

Distribution and Factors Influencing Macro- and Meso-Plankton in the Yangtze River Estuary- East China Sea Continental Shelf in Summer

摘要:

根据2019年夏季长江口及邻近海域17个站位的大中型浮游生物与水质参数分析，研究了大中型浮游生物的空间分布特征及其主要影响因素。在长江口咸淡水混合影响下，长江口-东海陆架断面浮游生物物种数及生物多样性指数均随盐度增加而增大，且淡水及低盐度站位与高盐度站位的优势物种存在显著差异。长江口-东海陆架关键断面13个站位的大中型浮游生物密度及生物量与叶绿素a无显著相关性，与营养盐含量呈显著负相关，表明上行效应并非控制该断面浮游生物分布特征的主要因素。在咸淡水混合所致多因素变化的复杂影响下，该断面大中型浮游生物分布的主要影响因素呈现出盐度相关的区域性差异。首次利用浮游生物在线成像和分类设备（CPICS）在多个高盐度站位开展原位观测，获得了多种大中型浮游生物的原位影像，可对夜光藻、双生水母等大型浮游动物鉴定至种，对桡足类鉴定至亚纲。CPICS垂直布放原位观测与野外垂直拖网采样分析结果所反映的物种数变化趋势具有一致性。

Abstract:

Based on the analysis of meso- and macro-plankton and water quality parameters from 17 stations in the Yangtze River estuary and adjacent regions in the summer of 2019， the present study investigated the spatial distribution patterns and major factors influencing meso- and macro-plankton. Under the influence of freshwater - seawater mixing in the Yangtze River estuary region， the species number and biodiversity indexes increased with increasing salinity in this transect， and the dominant species significantly differed among freshwater sites and low- and high- salinity sites. The density and biomass of meso- and macro-plankton in 13 stations of the typical transect along the Yangtze River estuary - East China Sea continental shelf showed no significant relationship with Chl-a， and significantly negatively correlated with the concentrations of nutrients， indicating that bottom-up effect was not the main controlling factor for the plankton distribution in this transect. Under the influence of multifactor changes derived by freshwater - seawater mixing， the main controlling factors on the distribution of meso- and macro-plankton exhibited regional differences related with salinity. The present study for the first time conducted in situ observation of plankton using a continuous particle imaging and classification system （CPICS） in some of the high salinity sites， and obtained in situ photographs of meso- and macro-plankton， which could support the species identification of macro-plankton （such as Noctiluca scientillans， Diphyopsis chamissonis）， and could support the identification of copepods to subclass. The results of in situ observation by CPICS （vertically moving） and laboratory analysis of field samples （obtained via vertical tows） showed a similar tendency on the changes of species numbers. In the future， with the help of long-term in situ observation in the whole water column and intelligent analysis of mega-data， CPICS would provide important real-time data for the species composition and evolution of plankton in the East China Sea.