Assessing the mineral accretion technique (MAT) for marine benthic restoration: a scoping review highlighting procedural weaknesses and evidence gaps.

Background: Marine ecosystems are undergoing rapid degradation, highlighting the need for conservation and active restoration measures to halt and potentially reverse biodiversity and functional losses. The Mineral Accretion Technique (MAT), which combines artificial reef construction with seawater electrolysis, has recently gained interest as a restoration tool to enhance benthic recovery. However, the scientific evidence supporting its effectiveness remains limited and inconclusive. With the present scoping review, we aim to: (i) consolidate the existing scientific literature on MATs; (ii) analyze and evaluate experimental application of MATs as a benthic restoration tool; and (iii) synthesize current knowledge on it effects on benthic organisms' health and recovery potential. Thereby, this scoping review serves as a pathway to popularize MATs among restoration academics and practitioners, as well as interdisciplinary professionals working in climate change mitigation, biodiversity loss or nature-based solutions. Methodology: This scoping review assessed the state of knowledge on MAT by conducting a structured bibliographic search using the PRISMA and Standards for Evidence Synthesis in Environmental Management guidelines on Scopus and Web of Science. The screening of the sources and their posterior data extraction were conducted in duplicate. The research landscape and patterns related to MAT terminology were analyzed using RStudio. Additionally, a quality assessment framework was developed and applied to evaluate the methodological robustness of the retrieved studies. Results: Of the 325 publications retrieved, only 33 were relevant. The majority of the body of scientific literature (82%) has been published in the last fifteen years. Nonetheless, the lack of consistent terminology has prevented MATs from being established as a benthic restoration technique. Despite 75.8% of studies claiming biological benefits, 90.1% of studies lacked adequate control groups, and over half failed to adequately report the results. Conclusions: We recommend the standardization of terminology, proposing "Mineral Accretion Technique (MAT)", improved experimental design, and clearer reporting protocols. This review identifies key evidence gaps and provides a roadmap for establishing a robust and replicable research strategy for MAT. By addressing these crucial weaknesses, future research can effectively examine the ecological validity and restoration potential of MAT, enabling its integration into marine restoration strategies.