Biodiversity Patterns on an Inshore to Offshore Gradient Using Metabarcoding and Barcoding Molecular Tools

It has been estimated that coral reefs shelter 830 000 species. Well-studied biodiversity patterns provide tools for better representation of species in marine protected areas. A cross-shelf gradient in biodiversity exists for fishes, corals, and macroalgae. Here, an inshore to offshore gradient in biodiversity on the Saudi Arabian coast of the Red Sea was sampled using Autonomous Reef Monitoring Structures (ARMS) with barcoding and metabarcoding techniques. It was hypothesized that differences in community structure would be driven by an increase in habitat area. The difference was attributed to the greater accumulation of sediments close to shore that increases the area habitable for sediment dwelling organisms and favors macroalgal cover. Macroalgae are inhabited by a greater number of species than live coral. Only 10% of the sequences of the barcoded fraction and <1% of the metabarcoded fraction had a BLAST hit on the NCBI database with a previously identified species sequence. In addition, the rarefaction curves for all fractions did not plateau. The ARMS community composition changed from inshore to offshore and was significantly correlated with the percentage of algal and bryozoan plate cover. The differences in community composition were related to changes in habitat but not to sediments retrieved from the ARMS.