Study on the ecological characters of Chaetognatha in waters of southern Huanghai Sea and East China Sea Ⅱ. Community characteristics

On the basis of the investigation data of 12 cruises from December 1977 to November 1978 in water of southern Huanghai Sea and East China Sea(28°~34°N,120°30'~127°E),the features and structures of the Chaetognatha community and its relation to the environmental factors were discussed.It shows that there were little significant seasonal alternations of species composition in 28 species recorded,except for seasonal and regional differential in dominant species among the community.Diversity index (H') and evenness (J) of the Chaetognatha community was 1.68 and 0.64 (by annual average),respectively,with much diversified community in the open sea compared with that in the near sea region.Four ecological groups of Chaetognatha are identified,among which warm water neritic and warm water euryhaline are index species of the wane and wax of the Huanghia Seawater mass,coastal waters along Zhejiang and mixed waters from the continental East China Sea.Besides,the analyses show that the most import factor affecting the diversity (H') was temperature andsaline.In these communities,dominant species were mainly composted of warm water low saline neritic and warm water cosmopolitan in addition to some species of warm water neritic and warm water oceanic,which are characteristic of the structure of temperate-subtropical community.