黄海水母旺发区浮游鞭毛虫和纤毛虫群落结构分布及其与水母发生关系初探

鞭毛虫和纤毛虫在海洋微食物环和经典食物链间的能量流动中起着重要的枢纽作用,但其在水母暴发过程中的作用仍然不明。本研究基于2011年春季以及水母旺发的夏季黄海专项航次,通过荧光染色技术和定量蛋白银法研究了南黄海水母频发海域3个断面(E:33°N,G:34°N,I:35°N)的鞭毛虫和纤毛虫的群落结构和时空分布特点,对其与水母的发生关系进行了初步探讨。结果表明,春夏两季的微型鞭毛虫丰度均以近岸水域为最高,向外海递减,高值区大多出现在水体表层及底层附近。夏季总微型鞭毛虫的丰度和生物量较春季略高,且异养微型鞭毛虫比例升高。纤毛虫丰度的水平分布与鞭毛虫正相反,以近岸较低,向外海递增,主要分布在表层及10m水层。在水母出现的E和G断面,夏季纤毛虫数量显著降低,丰度仅为春季的30%—40%;而未见水母的I断面夏季较春季的数量升高了一个数量级。推测夏季水母发生的E、G断面纤毛虫丰度明显降低系因水母的捕食压力所致,纤毛虫数量的减少导致对鞭毛虫的摄食压力降低,鞭毛虫数量增加;而未见水母的I断面纤毛虫则维持较高的丰度值。本研究表明,水母作为浮游生态系统的顶级捕食者,可通过营养级联效应对微小型浮游动物群落产生影响。

COMMUNITY STRUCTURE AND DISTRIBUTION OF PELAGIC NANOFLAGELLATES AND CILIATES AND THEIR RELATIONSHIPWITH JELLYFISH OCCURRENCE IN SOUTHERN YELLOW SEA

The role of nanoflagellates and ciliates during jellyfish bloom remains unexplored.We investigated the changes of the community structure and distribution of planktonic nanoflagellates and ciliates collected from the transects E,G and I in the southern Yellow Sea in April and August of 2011.The nanoflagellates and ciliates were studied using DAPI epifluorescence microscopy and the quantitative protargol stain.The abundance of total nanoflagellates was high in the coastal area and decreased towards the offshore area.Vertically,nanoflagellates mainly distributed in the surface and near the bottom layers in water.Compared with those in spring,the total abundance and biomass of nanoflagellates increased in summer.The abundance of ciliates increased from inshore to offshore area.This was different from that of nanoflagellates.Ciliates in the surface layer contributed up to 80% of total abundance and abruptly decreased below the 30 m depth.Compared with those in spring,the overall ciliate abundance and biomass decreased by about 50% in summer when jellyfish appeared.The ciliate abundance in summer was only 30%—40% of that in spring at transects E and G,while the ciliate abundance at the transect I,where there was no jellyfish observed,highly increased in summer.Jellyfish can cause direct and indirect changes to nano-and microzooplankton through cascading effects.The sharp decreases of ciliates at transects E and G were likely attributed to the predation pressure from increasing jellyfish,and consequently resulted in the increase of nanoflagellates.In contrast,ciliates increased at transect I without the impact of jellyfish.