Effects and management of Spartina alterniflora invasions on the diversity of Polychaeta of Dongtai salt marsh of Yancheng City.

Biological invasions as a significant component of global environmental change,can result in serious economic and ecological consequences.Assessing the ecological impacts of invasive plants is one of the most important issues in the study of environmental impact assessment.Three different sample sites(lake gate sites,salt marsh with Spartina alterniflora and salt marsh without S.alterniflora) of Polychaeta were studies from August,2005 to April,2006.The comparison of species richness,species diversity index and biomass shows the dominance of lake gate sites is highest and that of salt marsh is lowest;the amount of individuals in autumn is larger than those in other seasons;the species richness in summer is highest in different seasons.This paper analyses the ecological effects of Spartina alterniflora on the Polychaeta at the tidal flat of Dongtai City and discusses strategies for controlling their further range expansion.