2023年夏季从珠江口(PRE)到南海北部西沙群岛(NSCS)附近海域进行了巡航,调查分布情况,群落结构,以及使用高通量测序(HTS)和显微镜观察真核和原核浮游植物的组装模式。Dinophyta是基于HTS的真核浮游植物群落中最丰富的门,占总扩增子序列变异体(ASV)的92.17%。Syndiniales是真核浮游植物中最丰富的,而绿藻是蓝细菌中最丰富的属。α多样性在PRE区域显示最低值,并随深度逐渐降低,而蓝细菌在PRE和75m至750m的深度范围内表现出更高的α多样性指数。形态学结果与基于HTS的数据不同。硅藻(37种)主导了浮游植物群落,平均丰度为3.01×104个细胞L-1,但仅观察到6种鞭毛藻。Spearman相关分析和冗余分析(RDA)表明,浮游植物的分布和群落结构在很大程度上受NSCS中地理位置和环境参数的影响。中性群落模型(NCM)和零模型表明,确定性过程在真核浮游植物的组装中起着重要作用,异质选择和同质选择占47.27和29.95%,分别。然而,随机过程(超过60%)主导了蓝藻的组装,非主导过程占63.44%。总之,真核浮游植物的形成主要受环境因素和地理位置的影响,但是蓝细菌的集合是由两个随机过程形成的,占60%以上,和NSCS中的环境选择。
A cruise was conducted in the summer of 2023 from the Pearl River Estuary (PRE) to the adjacent waters of the Xisha Islands in the northern South
China Sea (NSCS) to investigate the distribution, community structure, and assembly patterns of eukaryotic and prokaryotic phytoplankton using high-throughput sequencing (HTS) and microscopic observation. Dinophyta were the most abundant phylum in the eukaryotic phytoplankton community based on HTS, accounting for 92.17% of the total amplicon sequence variants (ASVs). Syndiniales was the most abundant order among eukaryotic phytoplankton, whereas Prochlorococcus was the most abundant genus within
cyanobacteria. The alpha diversity showed the lowest values in the PRE area and decreased gradually with depth, while
cyanobacteria exhibited higher alpha diversity indices in the PRE and at depths ranging from 75 m to 750 m. The morphological results were different from the data based on HTS. Diatoms (37 species) dominated the phytoplankton community, with an average abundance of 3.01 × 104 cells L-1, but only six species of dinoflagellate were observed. Spearman correlation analysis and redundancy analysis (RDA) showed that the distribution and community structure of phytoplankton were largely influenced by geographical location and environmental parameters in the NSCS. The neutral community model (NCM) and null model indicated that deterministic processes played a significant role in the assembly of eukaryotic phytoplankton, with heterogeneous selection and homogeneous selection accounting for 47.27 and 29.95%, respectively. However, stochastic processes (over 60%) dominated the assembly of
cyanobacteria and undominated processes accounted for 63.44%. In summary, the formation of eukaryotic phytoplankton was mainly influenced by environmental factors and geographic location, but the assembly of
cyanobacteria was shaped by both stochastic processes, which accounted for over 60%, and environmental selection in the NSCS.