夏季南海西北部海域由外海至近岸表层海水浮游植物群落结构的空间变化

依托2013年夏季科技基础专项南海珊瑚礁海域调查航次，主要研究了南海西北部海域由外海到近岸表层海水内浮游植物叶绿素（Chl a）质量浓度和群落结构，以及微微型浮游植物（聚球藻、微微型真核生物）丰度。研究结果显示：1）调查期间，从外海到近岸总Chl a质量浓度由0.024逐渐增至19.1 μg/L；同时，小型浮游植物（Micro-，＞20 μm）所占比例由6.0%增至81%，微型浮游植物（Nano-，3~20 μm）所占比例（9%~24%）的空间变化不明显，而微微型浮游植物（Pico-，＜3 μm）所占比例由85%降至5.1%。2）从外海到近岸聚球藻和微微型真核生物丰度分别由（2.58±0.21）×106和（1.62±0.91）×105 cells/L升高至（2.29±0.10）×108和（1.83±0.46）×107 cells/L，而且二者呈显著正相关关系（R2＝0.68，p＜0.05）。3）调查海域总浮游植物生物量空间变化主要受微微型浮游植物丰度空间变化的调控。

SpatialVariability inSummer Phytoplankton Community fromOffshore to Coastal Surface Waters of the Northwestern South China Sea

Results are mainly presented about the spatial changes in phytoplankton chlorophyll a (chl a) concentration, community structure and picoplankton abundance (i.e. Synechococcus and pico- eucaryotes) from offshore to coastal surface waters of the South China Sea in the summer period of 2013. Total chl a concentration increased from 0.024 to 19.1 μg·L-1 from offshore to coastal waters. Coinciding well with chl a, the proportion of microplankton (>20 μm) increased from 6.0%-81%, while that of picoplankton (<3 μm) decreased from 85% to 5.1%; and the proportion of nanoplankton (3-20 μm) ranged during 9%-24% and showed no clear spatial change. There was a positive correlation of Synechococcus and pico-eucaryote abundances that increased towards the coastal waters from (2.58±0.21)×106 to (2.29±0.10)×108 cells·L-1 and from (1.62±0.91)×105 to (1.83±0.46)×107 cells·L-1, respectively. In addition, our results indicated that the spatial variability of total surface phytoplankton biomass was mainly regulated by picoplankton abundance in the surveyed waters.