Indoor intertidal flat mesocosm experiments were conducted to examine the effects of physical disturbance and seawater exchange on benthic communities over two years. 61 Statistical difference in biomass and species composition was analyzed between wave- and current-generated pool, and in water exchange regulated pools, respectively.
　There was no evidence for bacterial, algal, meiobenthic, and macrobenthic biomass had increase or decrease trend over time, nor clear seasonality.
　Standing stocks of these benthos came to dynamic equi-librium within eightmonths. Opportunistic species such as polychaete Capitella sp. or bivalve Muscu-lista senhousia were dominated in the pools.
　This indicates that experimental ecosystem in the meso-cosm was in a state of early succession.
　In the wave pool, bacterial and algal biomass were retained their lower abundance compared to the current pool.
　This is presumably because more intensive shear stresses were acting on wave pool sedi-ment, and the benthic algae were resuspended or were covered with the sediment.
　Close relationship between bacterial number and chlorophyll a content revealed that bacterial biomass appear to be affect-ed by dissolved organic carbon which is released by the algae.
　No significant difference of meiobenthic and macrobenthic biomass and their species richness were observed between the wave pool and current pool.