Artificial Reef Based Ecosystem Design and Monitoring (2025-08)¶

Black and white slags are common by-products of the metallurgical industry, with white slags having limited recycling applications. In this study, different circular artificial reef (AR) designs were compared using AR Ecosystem Index Transformation (AREIT) metrics and structural stability tests. The three-layer “Puzzle Reef” demonstrated the highest structural integrity and was selected for deployment, which was performed on July 18^th, 2023 at the OBSEA. Although extreme current conditions during October–November 2023 caused minor displacement of components, the structure remained intact overall. The reef’s influence on the local fish community was evaluated through high-frequency photo monitoring (one image per min) from July 18^th, 2023, to October 24^th, 2024, using an AI-automated procedure for fish classification and counting. In parallel, colonizing assemblages were analysed in the laboratory from two reef components retrieved on December 16^th, 2024. The visual census recorded 18 bony fish species and one cartilaginous fish family, totalling 1,228,915 individuals (ind.). Fish biodiversity and abundance increased over time, as did AR Multimeric Indices, indicating a positive ecological trend following AR deployment. These indices, together with AREIT, are proposed as valuable tools to inform global marine habitat policies. Biofouling analysis revealed a colonizing assemblage of 2930 ind.⋅m2 across 59 species, with a total dry biomass of 23.23 mg⋅m2. The assemblage, largely dominated by balanids, crustaceans, polychaetes, gastropods, and bivalves, was mostly composed of small-sized individuals with a mean biomass of 4.6 μg. Nevertheless, the Abundance-Biomass Comparisons curve indicated a stable and relatively mature community, characteristic of relatively low-disturbance conditions.