Grazing Pressure by Ciliates on the Nanoflagellate Community in a Subtropical Pelagic Continental Shelf Ecosystem: Small Ciliates (of < 45 mu m) are Major Consumers of the Nanoflagellate Community

摘要

Trophic relations between nanoflagellates and ciliates in the southern East China Sea (ECS) were studied along a cross-shelf transect in Aug. 2010. Short-term experiments with 4-mu m fluorescently labeled beads (FLBs) were used to estimate ingestion rates of the ciliate community at 6 stations. There were 3 zones along the transect: inner-shelf, mid-shelf, and upwelling zones. At all sites, ciliates of < 45 mu m in equivalent spherical diameter (ESD), including Strombidium spp., Strobilidium spp., Laboea spp., Tontonia spp., and tintinnids, were the most abundant group (79%-95%) of the ciliate community. Strombidium spp. ingestion rates ranged 59374 flagellates/ciliate/d, Strobilidium spp. ranged 26-268 flagellates/ciliate/d, Laboea spp. and Tontonia spp. ranged 18-289 flagellates/ciliate/d, and tintinnids ranged 58-249 flagellates/ciliate/d. Ciliate of < 45 mu m in ESD were the most important nanoplankton grazers, consuming nearly 100% of nanoflagellate production in inner-shelf and 43% in offshore oceanic waters. In summer, ciliates are one of the main trophic level consumers of nanoflagellates, especially in inner-shelf waters.