Abstract
In order to understand thc rQle of tidal flat sand seaweed beds in biologica lproductio nin the southern area of Hiroshim aBay ，Japan， seasonal variations in the prinlar yproductie nrates of tidal flats alld seaweed beds wcre es 亡imated 吼uantitatively using
ecosystem model analysis， The amual average primary productio nrates per しmil area of tidal flat sand seaweed beds were 1，514and 2，680 mg C m−2 day一と， respectively ． The pnmary productiQn rates Df tidal flats and seaweed bcds were hlgh in May （2，100mg C m
−2 day −1）and in August and September （5，130 mg C In−2 day l！， rcspectively ， From April to OctDber， these ra しcswere higher than thc nutrient supply by river discharge
