Concrete coastal infrastructures are typically designed with a primary focus on functionality and structural integrity and often lack the structural complexity that provides suitable habitats for various marine organisms. Recently, ecological engineering aimed at boosting biodiversity and ecosystem functions has gained attention and has been extensively studied. In this study, artificial seaweeds (ASs) imitating Sargassum were introduced on a seawall of a fishing port located in Hokkaido, Japan, to examine their impact on epifauna and macroalgae from December 2022 to December 2023 to assess AS's potential for the future enhancement of biodiversity and ecosystem functions.
Epifaunal abundances on ASs and the seawall ranged from 131±16 to 3518±1027 ind. m−2 and from 92±350 to 1191±172 ind. m−2, respectively, and both showed a peak in June 2023. Percentage cover of macroalgae also peaked in June, with AS hosting different dominant species than the seawall. Despite Amphipoda's dominance on both ASs and the seawall, ASs had 2.7–18.1 times higher Amphipoda abundance, except for the sampling conducted right after the AS deployment. This study indicated that utilizing AS can improve biodiversity and biomass in urbanized coastal waters compared to concrete seawalls alone.