中文摘要：

于2009年7月20日至8月16日（夏季）,2010年1月6日至30日（冬季）,2010年10月26日至11月24日（秋季）和2011年4月30日至2011年5月24日（春季）在南海北部调查了微型异养鞭毛虫的生态分布特点。结果表明：春、夏、秋、冬的微型异养鞭毛虫丰度分别为0.05×103～1.93×103,0.03×103～2.65×103,0.09×103～2.05×103和0.04×103～1.84×103 cells/mL,生物量（以碳计）分别为0.56～19.50,0.04～24.11,0.96～14.80和0.29～22.26μg/L。4个季节的微型异养鞭毛虫丰度均以2～5μm粒级的为主,其所占比例超过65%,10～20μm粒级所占比例通常低于10%。在水平分布上,微型异养鞭毛虫的丰度随离岸距离的增加逐渐降低;在垂直分布上,微型异养鞭毛虫的丰度随深度的增加逐渐降低,但夏季微型异养鞭毛虫丰度的高值多出现在次表层叶绿素a极大值层（DCM层）。微型异养鞭毛虫的丰度分布受到多重因素的交互影响,并且其所受调控模式在不同季节存在差异：春季和秋季微型异养鞭毛虫主要受下行调控;夏季微型异养鞭毛虫主要受上行调控;冬季上行和下行调控对微型异养鞭毛虫的影响相近。

英文摘要：

Abundance,biomass and size structrue of heterotrophic nanoflagellates（HNF）were investigated in the northern South China Sea（NSCS）during four cruises in summer（July 20-August 16,2009）,winter（January 6-30,2010）,autumn（October 26-November 24,2010）and spring（April 30-May 24,2011）,respectively.It was shown that the abundance and biomass of HNF in spring,summer,autumn,winter were（0.05-1.93）×103,（0.03-2.65）×103,（0.09-2.05）×103,（0.04-1.84）×103 cells/mL and 0.56-19.50,0.04-24.11,0.96-14.80,0.29-22.26μg/L,respectively.HNF in the 2-5μm size fraction dominated the HNF community,which accounted for more than 65% of total HNF abundance in the four seasons,while HNF in the 10-20μm size class constituted less than 10% of total HNF abundance.In horizontal distribution,the abundance of HNF decreased gradually with distance from the coast to the open sea.In vertical distribution,the abundance of HNF decreased gradually with the increasing water depth,however,the highest abundance of HNF was observed in DCM layer in summer.Distribution of HNF in NSCS was affected by multiple environmental factors.The seasonal patterns in regulatory regime（top-down vs bottom-up）of HNF were various：during spring and autumn HNF abundance was mainly controled by predator（top-down）factors;during summer HNF abundance was mainly controled by resources（bottom-up）;during winter the dominant pattern was undefined.