Succession of macroalgae on seashell based porous panels fixed on cubic artificial reef in Beppu Bay, southern Japan

Abstract

The artificial reefs (ARs) deployed on a sandy-muddy bottom at depths of 10 to 16 m in Beppu Bay, southern Japan were investigated using ROV (Remotely Operated Vehicle) and scuba diving from 2008 to 2017. The ARs were made of cubic concrete blocks overlaid by two porous panels consisting of seashells on top side. Young thalli of Sargassum sp. appeared on the panels in the first year. The dominant macroalgal communities changed from Sargassum sp. to Ecklonia kurome after several years. Macroalgae were more abundant on the porous panel than on the other sides of the concrete blocks after ten years. The biomass of the benthos (shell fish, barnacles and bristle worms) on the surveyed blocks in March 2017 was 455.12 g/m² on the porous panel part and 366.25 g/m² on the smooth part of the concrete blocks. The installation of porous panel material facilitated more attachment of seaweeds than on the smoother part of the ARs making it more advantageous in creating seaweed beds.