One hundred fifteen diatom taxa in thirty surface sediment samples collected from Osaka Bay were identified and listed They belong to the following fifty-six genera: Achnanthes (3 taxa)  Achnanthidium (3)  Actinocyclus (1)  Actinoptychus (1)  Amphora (3)  Aulacoseira (3)  Azpeitia (1)  Chaetoceros (1)  Cocconeis (4)  Coscinodiscus (3)  Ctenophora (1)  Cyclostephanos (1)  Cyclotella (5)  Cymatotheca (1)  Cymbella (3)  Delphineis (1)  Diadesmis (1)  Diploneis (6)  Epithemia (1)  Fallacia (4)  Fragilaria (2)  Fragilarioforma (1)  Gomphonema (7)  Gomphoneis ( 1)  Grammatophora (2)  Hantzschia (1)  Karayevia (1)  Luticola (1)  Melosira (1)  Navicula (5)  Neodelphineis (1)  Neofragilaria (1)  Nitzschia (7)  Paralia (1)  Placoneis (1)  Planotidium (2)  Pleurosigma (1)  Podosira (1)  Rhaphoneis (1)  Reimeria(1)  Rhoicosphenia (1)  Rhopalodia (2)  Sellaphora (2)  Seminavis (3)  Skeletonema (1)  Staurosira (1)  Staurosirella (2)  Stephanodiscus (1)  Surirella (3)  Synedra (1)  Tabularia (1)  Thalassionema (1)  Thalassiosira (6)  Trachyneis (1)  Trachysphenia (1)  Tryblionella (2)