南海东北部浮游植物对氮、磷加富的响应及与不同水团的关系

2014年5月搭载"实验3"号科考船对南海东北部海区进行氮、磷营养盐现场加富培养实验。水团分析的结果表明,南海东北部海区的环境参数随着空间的变化大体可以分成3个区域:近岸海区、陆架海区和陆坡、海盆海区。加富培养过程中近岸海区和陆坡、海盆海区浮游植物未发生显著变化。陆架海区浮游植物出现显著增长,该海区浮游植物加富氮、磷以后在48h出现反应,同时添加氮、磷显著促进了浮游植物的生长。各培养站位均检测到大量束毛藻,加富培养后迅速减少。营养盐的添加改变了海区浮游植物原有的硅甲藻比例与各粒级叶绿素比例,陆架海区培养后的改变最为明显,同时添加氮磷培养72h后,由甲藻为主的优势种如卡氏前沟藻(Amphidinium carterae)、光亮鳍藻(Dinophysis argus)、原甲藻(Prorocentrumsp.)转变成了以硅藻为主如绕孢角毛藻(Chaetoceros cinctus)、旋链角毛藻(Chaetoceros curvisetus)、放射角毛藻(Chaetoceros radicans)和丹麦细柱藻(Leptocylindrus danicus)。同时,加富实验表明磷酸盐的添加促进了陆架海区微微型浮游植物聚球藻的生长。

Phytoplankton responses to nitrogen and phosphorus enrichment in relation to different water masses

In situ survey of northeastern South China Sea (20°~24°N,114°~121°E),combined with nutrient (Nitrogen and Phosphorus) enrichment experiments were conducted during a cruise of Shiyan Ⅲ in May 2014. Based on the analysis of environmental variables and water masses,the northeastern South China Sea were divided into three areas: near shore regions,continental shelf regions and deep sea basins. The incubation results showed that phytoplankton did not response significantly to enrichment during incubation in near shore and sea basin stations,whereas increased after 48 h in the area of continental shelf,especially in the group which added both nitrite and phosphate. Trichodesmium were abundant in all experiment stations,while died away quickly during incubation. The phytoplankton species composition and proportion of size fractioned Chl a also changed notably with nutrient enrichment,and the variation was more significant in shelf regions. The results of shelf regions showed that the dominant species shifted from dinoflagellates such as Amphidinium carterae,Dinophysis argus,Prorocentrum sp. to diatoms such as Chaetoceros cinctus,C. curvisetus,C. radicans and Leptocylindrus danicus after incubation. Besides,the results also revealed that phosphate stimulated the growth of picophytoplankton synechococcus in the area of continental shelf significantly.