南海北部夏季浮游植物群落对中尺度涡物理过程的响应

Response of Phytoplankton Communities to the Physical Processes of Mesoscale Eddy in the Northern South China Sea in Summer

为了分析南海北部浮游植物群落对中尺度暖涡的响应,于2021年夏季在南海北部海域布设了19个大面站,采集浮游植物水样,并分析浮游植物丰度、群落特征指数,以及水体叶绿素极大值层和营养盐浓度分布等,结果表明:共鉴定出隶属于3门82属的307种浮游植物,其中甲藻和硅藻为该海域主要的浮游植物类群,分别有176种(33属)和129种(48属),优势种为菱形海线藻(Thalassionema nitzschioides)、菱形藻属(Nitzschia spp.)、环沟藻属(Gyrodinium spp.)、斯克里普藻属(Scrippsiella spp.);在中尺度暖涡中心,叶绿素极大值层(Deep Chlorophyll Maximum, DCM)相比边缘区域更深,营养盐浓度分布也呈现类似特点;中尺度涡的物理过程对浮游植物群落结构产生显著影响,表现为暖涡中心区域的浮游植物丰度低于边缘区域。斯皮尔曼相关性分析(Spearman Correlation Analysis)表明,在暖涡中心区域,随着温度升高,硅藻丰度开始降低,且硅藻在中心区域的丰度低于边缘区域;相比之下,甲藻在中心区域的丰度高于边缘区域。进一步分析硅甲藻优势种的分布特征可知,菱形海线藻,菱形藻在暖涡中心区域的丰度要小于边缘区域,而环沟藻、斯克里普藻则相反。通过对暖涡区域群落特征指数的分析发现,从边缘区域到中心区域,物种多样性显著降低,物种分布趋于均匀。本研究可为探索浮游植物对中尺度涡响应提供基础资料。

This paper aims to study the response of phytoplankton communities in the northern South China Sea to mesoscale warm eddies.Phytoplankton water samples were collected in the 19 stations during summer cruise in 2021,and a series of analyses were conducted on the phytoplankton abundance,diversity index,evenness index,etc.A total of 307 species of phytoplankton were identified in 3 phyla and 82 genera.The results show that dinoflagellates and diatoms are the main phytoplankton groups in this area,with 176 and 129 species respectively.The main dominant species are Thalassionema nitzschioides,Nitzschia spp.,Gyrodinium spp.and Scrippsiella spp..The depths of chlorophyll maximum in the eddy center are deeper than those in the edge region,and the nutrient concentrations show a similar distribution pattern.The abundance of phytoplankton in the central region is lower than that in the marginal region,suggesting a significant effect of the physical processes of mesoscale eddy on phytoplankton community structure.The Spearman correlation analysis showed that the diatom cell abundance began to decrease with the increase of temperature in the central region of the warm eddy,and the diatom abundance in the central region is lower than that in the marginal region.In contrast,dinoflagellates have a higher cell abundance in the central region than in the marginal region.The abundance of Thalassionema nitzschioides and Nitzschia spp.in the warm eddy center region is lower than that in the marginal region,whereas the abundance of Gyrodinium spp.and Scrippsiella spp.exhibits the opposite trend.The analysis of community characteristic index of warm eddy region suggested that species diversity decreased significantly from marginal region to central region,and species distribution tended to be uniform.This study provides basic data for future exploration of phytoplankton response to mesoscale eddy.