Environmental DNA Metabarcoding in Marine Ecosystems: Global Advances, Methodological Challenges, and Applications in the MENA Region.

Environmental DNA (eDNA) metabarcoding has transformed marine biodiversity monitoring by allowing non-invasive, cost-effective detection of species with high resolution across diverse marine habitats. A systematic literature search was conducted using Google Scholar, Scopus, and the Qatar University Library databases. Relevant peer-reviewed publications were screened and selected based on predefined inclusion criteria to ensure comprehensive coverage of studies. This review synthesizes advances in global and regional eDNA applications, emphasizing the Middle East and North Africa (MENA) region, which faces unique environmental extremes, high endemism, and significant data gaps. eDNA metabarcoding often outperforms traditional methods under comparable sampling effort to traditional surveys in detecting rare, cryptic, and invasive taxa, but technical challenges like incomplete reference databases, primer biases, PCR inhibitors, and inconsistent methodologies limit their effectiveness, particularly in understudied areas such as MENA. Recent developments, including multi-marker approaches, autonomous samplers, and next-generation sequencing, are enhancing detection precision and enabling broader, real-time monitoring. In the MENA region, early studies have revealed eDNA's potential for habitat distinction, biogeographic research, pollution assessment, and the early discovery of non-indigenous species, although progress is hindered by gaps in reference libraries, infrastructure, and regulation. This review underscores the urgent need for regional collaboration, standardized protocols, and capacity-building. By integrating eDNA with traditional methods and leveraging emerging technologies, the MENA region can establish itself as a leader in marine biomonitoring under extreme environmental conditions, providing actionable insights for conservation and sustainable management of its unique marine ecosystems.