Abstract: Alien species invasion is generally regarded as the second serious threat following habitat destruction to marine ecosystem. This paper elaborated the biological and ecological characters of marine alien species in the South China Sea and the impacts of these species invasion on the South China Sea ecosystem, and put forward the corresponding control strategies. There were totally 35 alien species in the South China Sea, most of which were accidentally introduced species. Among the alien species, alien algae were dominant (16 species, 45.7% of the total), followed by fouling animals (11 species, 31.4%), alien microorganisms (5 species, 14.3%), and intertidal plants (3 species, 8.6%). The alien species invasion weakened the community structure and reduced the biodiversity, altered the genetic diversity and decreased the genetic variation, caused diseases outbreak, and aggravated the marine ecological disasters of the South China Sea ecosystem. The above-mentioned analyses on the characters of marine alien species in the South China Sea and on the impacts of these species invasion on the South China Sea ecosystem could provide basic data for the further research of alien species invasion in the South China Sea, whereas the suggested control strategies could help the regional administrations to better protect the marine ecosystem of the South China Sea.

Key words: drying-rewetting, litter decomposition, nutrient release, Horqin Sandy Land., semi-arid region