Spatio-temporal Distributions Of Planktonic Ciliates In The China Seas

Marine planktonic ciliates are a major, ubiquitous and diverse group of protozoa.They range in size from10to200μm and are divided into tintinnids and aloricateciliates. As one of the main components of microzooplankton, planktonic ciliates aretrophic link between the microbial food web and traditional food chain, and playimportant roles in material cycles and energy flows in the marine planktonicecosystem.Until1990s, researches on ciliate ecology arised in China seas including theBohai Sea, Yellow Sea, East China Sea and South China Sea. Most studies of ciliatedistribution focused on the Northern Yellow Sea, the shelf of East China Sea andNorthern South China Sea, while studies in other sea areas are rare for now.In this study, we first studied seasonal patterns of ciliate abundance and biomassin the Northern Yellow Sea, Southern Yellow Sea, East China Sea and South ChinaSea; second, we discuss the coupling between ciliate distribution and physicalprocesses in the Yellow Sea, East China Sea and South China Sea; third, weperformed investigations in the coastal water near Dalian and Beibu Gulf which haveno ciliate data before.Distribution of ciliate abundance and biomass in the Northern Yellow SeaThe average abundance of ciliates near Zhangzi Island, the Northern Yellow Seawas3208±2828ind L^-1, and the average biomass was3.73±3.55μg C L^-1. Watercolumn ciliate abundance peaked in spring and autumn, and water column ciliatebiomass peaked in spring and summer. Larger aloricate ciliates were more prevalentin spring, while smaller increased the proportion in summer and autumn. Percentageof tintinnids in total ciliate abundance was higher in summer and lower in autumn.The average abundance of ciliates in the coastal water near Dalian, Northern Yellow Sea in July and August was5107±4451ind L^-1and7894±7212ind L^-1,respectively. The average biomass was10.17±9.06μg C L^-1and15.24±18.49μg C L^-1.We recorded the species Tintinnopsis corniger Hada,1964for the first time in Chinawaters.Seasonal cycle of ciliate abundance and biomass in the Southern Yellow SeaThe average abundance of ciliates in Sanggou Bay was7552±10979ind L^-1, andthe average biomass was4.79±5.77μg C L^-1. Ciliate abundance was highest in spring,while ciliate biomass was highest in summer. Larger aloricates were more prevalent insummer, while smaller increased the proportion in winter. Percentage of tintinnids intotal ciliate abundance was highest in summer and lowest in winter.The average abundance of ciliates in the Southern Yellow Sea was813±1233indL^-1, and the average biomass was0.73±1.02μg C L^-1. Ciliates showed clear seasonalcycle: there were two peaks of ciliate abundance （May and August） and only one peakof ciliate biomass （May）; larger ciliates were more prevalent in spring, while smallerciliates increased the proportion in summer. Percentage of tintinnids in total ciliateabundance was higher in spring and autumn and lower in winter.The abundance, biomass and composition of ciliates exhibited differences inassociated with water masses. High ciliate abundance mainly occurred around thethermal fronts from December to April; and occurred near the tidal fronts in Augustthrough October.Seasonal cycle of planktonic ciliates and influence of Changjiang diluted wateron ciliate distribution in the East China SeaCiliate abundance in the shelf of East China Sea was in average of1409±2048ind L^-1, and ciliate biomass was in average of1.97±3.64μg C L^-1. Ciliate abundanceand biomass were highest in summer. Larger ciliates were more prevalent in spring,while smaller ciliates increased the proportion in summer and autumn. Percentage oftintinnids in total ciliate abundance was higher in autumn and lower in summer.Ciliate abundance and biomass were higher in the Changjiang Diluted Water （CDW） than in the Oceanic Water （OW） in spring and summer, while ciliateabundance and biomass were much lower in the CDW than in the OW in autumn. Thecell size of the ciliate community decreased from the CDW to the OW in the threeseasons.Distribution of ciliate abundance and biomass in the South China SeaThe average abundance of ciliates in the Northern South China Sea in winter andsummer were486±484ind L^-1and809±1008ind L^-1, respectively. The averagebiomass in winter and summer were2.84±3.26μg C L^-1and1.96±3.80μg C L^-1,respectively. Percentage of tintinnids in total ciliate abundance was higher in summerand lower in winter.The depth-weighted average ciliate abundance and biomass decreased fromcoastal areas to off-shore areas in both seasons. Ciliates tended to accumulate in thesub-surface layers in winter. Ciliate abundance and biomass were usually higher in thesurface or middle layers in summer, although sometimes ciliates were located near thebottom layers in the off-shore stations.The average abundance of ciliates in the Beibu Gulf was521±369ind L^-1, andthe average biomass was0.63±0.54μg C L^-1. The depth-weighted average ciliateabundance and biomass were higher in the central gulf and coastal waters alongTransect A and B, respectively. Ciliate abundance and biomass were uniformlydistributed vertically in the water column along Transect A, while ciliates tended toaccumulate in the upper15m level along Transect B.