东海春季水华期浮游植物生长与微型浮游动物摄食

2005年4～6月在东海有害水华频发区14个站位采样,通过现场稀释法实验对春季东海水域浮游植物比生长率和微型浮游动物比摄食率进行了研究.结果表明东海有害水华频发区浮游植物群落以甲藻为优势.浮游植物比生长率在水华爆发前相对较低,平均为1.18 d~(-1);进入水华期后比生长率明显升高,但在水华站位随现存量增加而降低;非水华区比生长率近岸高、远岸低.微型浮游动物主要以急游虫和桡足类幼体为主,而种类上以砂壳纤毛虫居多.微型浮游动物比摄食率在水华爆发前波动较大,介于0.53～1.73 d~(-1),平均为0.90 d~(-1);在水华区比摄食率较为稳定,浮游植物比生长率的降低导致群落净生长率持续下降;在非水华区,比摄食率整体较高,近岸低而远岸高.微型浮游动物的摄食对浮游植物群落的生长有一定的控制作用,但在水华爆发后这种控制作用将减弱.

Phytoplankton growth and micro-zooplankton herbivory during the spring phytoplankton bloom period in the East China Sea

From 27th April to 17th June 2005, phytoplankton growth and feeding by microzooplankton were studied in waters frequently subject to harmful algal blooms (HABs) in the East China Sea. Ship-board dilution incubation experiments were carried out at 14 stations to calculate the phytoplankton specific growth rate and the specific rates of grazing by microzooplankton on phytoplankton. Dinoflagellates dominated in the phytoplankton community at typical stations. In the microzooplankton, Strombidium and copepod nauplii were dominant, and tintinnids were important. Phytoplankton specific growth rates, with the average 1.18 d-1, were comparatively low before HABs, but increased significantly during the period of frequent HAB occurrence. Phytoplankton specific growth rate showed positive correlation with the standing stock of phytoplankton. The microzooplankton grazing rate ranged from 0.53 d-1 to 1.73 d-1 before HABs, and converged to 0.90 d-1 at HAB stations despite the decreased specific growth rate of phytoplankton. During the HAB period, the microzooplankton grazing rate at non-HAB stations was lower in coastal areas, but higher in the open sea. The results indicate that grazing by microzooplankton is a key process controlling the growth of phytoplankton. The effect, however, appears to have been be weaker in HAB zones.