Bull. Jpn. Soc. Fish. Oceanogr. 77(4), Page 252-258, 2013   Food web structure of animal communities formed on seawalls of artificial islands in Osaka Bay as determined by analyses of carbon and nitrogen stable isotope ratios Yoshihiro Yoneda1†, Kenji Kaneko2,*, Koichi Matsui3, Teruaki Suzuki4 and Teruhiro Takabe5 1 Fisheries Division, Department of Environment, Agriculture, Forestry and Fisheries, Osaka Prefectural Government, 1-14-16 Nankokita, Suminoe-ku, Osaka, Osaka 559-8555, Japan 2 Marine Biological Research Institute of Japan Co., Ltd., 3-9-2 Kobai-cho, Showa-ku, Nagoya, Aichi 466-0031, Japan 3 New Kansai International Airport Engineering Co., Ltd., 1 Senshu-kuko kita, Izumisano, Osaka 549-0001, Japan 4 Graduate School of Environmental and Human Sciences, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya, Aichi 468-8502, Japan 5 Research Institute of Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya, Aichi 468-8502, Japan * Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiya, Aoba-ku, Sendai, Miyagi 981-8555, Japan † E-mail: YonedaYo@mbox.pref.osaka.lg.jp Coastal artificial structures are demanded for a consideration of environmental protection in recent years. Although gradually sloped seawalls were adopted in various parts of Japan, little is known on the food web of the community around such structures. In the present study, the food web and food source were estimated on the seawalls of artificial islands in Osaka Bay as determined by analyses of carbon and nitrogen stable isotopes. Clustering of δ13C and δ15N values of animals on the seawalls showed five feeding groups: fish, suspended feeders, suspended and surface deposit feeders, carnivores and herbivores. The dual isotope plot of δ13C and δ15N showed that the three food sources (phytoplankton, microbenthic algae and macrobenthic algae) were eaten by herbivores, suspended feeders, surface deposit feeders, and that these animals were ingested by carnivores and fish, both occupying the highest trophic levels. Key words: food web, food source, stable isotope, coastal artificial structures, Osaka Bay