his paper deals with the community structure and metabolism of the model grassy pond ecosystem and the possibility of its application to evaluate the effects of chemical contamina-tion on ecosystems,The model pond of ecosystems consisted of eight glass fiber tanks each inadimension of 3m × 1m ×1m(V=3m￣3). Each tank was filled with tap water,together with10cm thick river sediments containing seeds,cysts and eggs of aquatic organisms on its bot-tom, Some KNO_3 and NaH_2PO were added to keep water nutrients ...