Species distribution and diversity of Appendicularia in the East China Sea

Based on seasonal investigation at 23°30′-33°00′N and 118°30′-128°00′E of the East China Sea during 1997-2000,the species composition,seasonal variation and horizontal distribution of species number and diversity value(H′) and geographical distribution of Appendicularia in the East China Sea were discussed by ecological indices.The result showed that totally six species appeared at the areas in four seasons,among which Oikopleura dioica,O.longicauda and O.rufescens were common species.Since emerged in 4 zones,O.intermedia was subordinate species.O.fusiformis and Oikopleura.spp were rare species.Except for Oikopleura.spp,all the other species appeared in all seasons in the East China Sea so that seasonal alternation was not obvious.O.dioica showed a broad adaptability to environmental factors because it distributed in almost the whole area of the sea with high occurrence frequency.O.longicauda also showed wide geographical distribution though its occurrence frequency was significantly lower than the former.Compared with the former,the latter showed more features of warm-water species.O.rufescens emerged in the zones with high temperature and salinity,which also can be classed as warm water species.The Appendicularians in the East China Sea mostly distributed at the offshore area controlled by warm current forces,thus indicated the warm water species characteristics. The diversity value(H′) of Appendicularians was relatively low caused by the aggregation of some individual dominant species.