Performance of innovative materials as recruitment substrates for coral restoration

Abstract

Artificial reefs and, more recently, ecoengineering are frequently advocated as possible tools to counteract the loss of tropical coral reefs worldwide. Despite increasing availability of novel materials, there is limited understanding of how different materials and their physical and chemical properties can influence coral recruitment success and early benthic community development. This study investigated the efficacy of several innovative materials as recruitment substrates for corals and other sessile benthic communities. Stacks of vertically oriented tiles made of eight innovative materials and two common (control) materials were deployed for 6 months during major coral spawning events on the forereef of Mo'orea, French Polynesia. Tiles were separated from their neighbors by 15 mm to mimic cryptic habitats that are sheltered from predation and typically favored by coral recruits. Six innovative materials, including 3D printed concrete, polyvinyl chloride (PVC) with chitosan coating, fiberglass polymer, and flax-based polylactic acid, produced similar coral recruitment to control materials (Portland concrete and PVC). Two materials (porous concrete and ceramic foam) produced lower recruitment. Porous concrete was characterized by a high abundance of non-coralline encrusting red algae, which negatively correlated with coral recruitment, while ceramic foam was prone to erosion. The results suggest the structural micro-complexity and durability of an artificial material and the composition of the benthic communities colonizing it can strongly influence coral recruitment. This study highlights several innovative materials as suitable recruitment substrates for coral restoration and provides a better understanding of the properties of artificial materials that are critical for coral recruitment success.

Coral recruitment: patterns and processes determining the dynamics of coral populations

“…1B), including acrylic, polyvinyl chloride plastic, unglazed terracotta, custom‐moulded cement or clay, tyres, and dead coral colonies cut into slabs (e.g. Fitzhardinge & Bailey‐Brock, 1989; Price, 2010; Harriott & Fisk, 1987; Doropoulos et al ., 2016; Leonard et al ., 2022), and it is well known that the type of material influences the corals that recruit to their surfaces (Harriott & Fisk, 1987; Leonard et al ., 2022).…”

Assessing the Attractive Effects of Floating Artificial Reefs and Combination Reefs on Six Local Marine Species

“…The ARs' configuration is the key factor in influencing the attraction effect. Studies have shown that artificial materials' microstructure complexity and durability can strongly influence attraction [3]. More complex structures attracted more species [45,46].…”

“…Marine fisheries are a critical global food supply element and are significant for many countries and regions [1]; however, many marine species, habitats, and ecosystems have suffered catastrophic declines [2][3][4] due to increased pollution, the development and hardening of coastlines, the extraction of resources, and the introduction of invasive species [5][6][7][8][9].…”

Underwater macrophotogrammetry to monitor in situ benthic communities at submillimetre scale

“…Proxies of recruitment have commonly been quantified using recruitment tiles made of diverse materials and shapes (e.g. Harriott & Fisk, 1987;Herbert & Hawkins, 2006;Leonard et al, 2022).…”

“…Proxies of recruitment have commonly been quantified using recruitment tiles made of diverse materials and shapes (e.g. Harriott & Fisk, 1987; Herbert & Hawkins, 2006; Leonard et al, 2022). However, the use of artificial substrata to quantify recruitment introduces some level of bias related to: tile materials, tile orientation, duration of conditioning timeframe (and associated fouling communities), handling, change of environmental conditions during laboratory work and/or following bleaching and drying treatments (e.g.…”