Kansai International Airport is located in the waters of the eastern part of Osaka Bay. The airport consists of two artificial islands. This is the first airport in Japan where gradually sloped seawalls, which are suitable for algae growth, are employed on a large scale. The ecosystem services of seaweed beds have been evaluated to some extent. However, the actual conditions of benthic communities have not been identified. Against this backdrop, we investigated the standing stock in nitrogen equivalent and characteristics of feeding habits of benthic communities on each seawall. The average standing stock in nitrogen equivalent per seawall of the airport islands was found to be 222 gN/m, with suspension feeders accounting for 55.2%, feeders primarily of subsurface deposit 23.0%, other carnivores 13.5%, herbivores 6.1%, and fish 2.1%. The component ratio differs depending on the seawall. The standing stock in nitrogen equivalent in waters where the flow field is stagnant was the smallest, and this was attributed to the low percentage of suspension feeders. The component ratio differs depending on the seawall. The percentage of suspension feeders was high on gradually sloped seawalls facing the outer waters. This tendency was strong on seawalls subject to strong wave flows. The standing stock distribution in nitrogen equivalent in benthic communities on each seawall is similar to the standing stock distribution of algae. The standing stock of seaweed beds was found to highly correlate with the standing stock of fish and macrobenthos in nitrogen equivalent (the standing stock of fish in nitrogen equivalent in particular). It was found that seawalls that are suited for algae to grow serve as a suitable growth environment for benthic communities.
