Phytoplankton growth and micro-zooplankton herbivory during the spring phytoplankton bloom period in the East China Sea
东海春季水华期浮游植物生长与微型浮游动物摄食

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.