Material type and origin influences the abundances of key taxa on artificial structures

Coastal and marine urbanization have caused the sprawl of a variety of marine infrastructures, primarily built with artificial materials. We conducted a systematic review and a meta-analysis of 76 studies to determine how material type affects the ecological performance of artificial structures for possible eco-engineering applications. We compared three rocky-type materials, specifically autochthonous natural rocks, allochthonous natural rocks and concrete (i.e., the most abundant novel rock type of the Anthropocene) to each other and to other non-rocky materials commonly used to build infrastructures: metal, plastic, ceramic, rubber and wood. We tested the effects on diversity, abundance, or biomass of epibiota, as well as on key functional groups of epibenthic organisms (algae, sessile and vagile invertebrates). Studies were mostly short term (<7 months duration), with variable outcomes among experiments and functional groups. Overall rocky substrates (including concrete) performed better (more diverse and abundant epibenthic communities) than other non-rocky construction materials (such as metal, plastic, or rubber), and autochthonous rocks performed better than any allochthonous (rocky and non-rocky) material. We did not detect a better ecological performance of eco-friendly concretes over traditional (gray) Portland concrete in terms of species growth, but eco-materials could still provide significant benefits by lowering raw materials demand, energy costs and/or CO2 emissions or enhancing the structure aesthetic. We suggest that material type as well as its origin (autochthonous vs allochthonous) are important but still largely overlooked properties of marine artificial structures that should be considered in combination with other types of substrate eco-engineering manipulations to reduce the impacts on native biota.