Beyond the visual: using metabarcoding to characterize the hidden reef cryptobiome.

Area of Science:

• Marine Biology
• Ecology
• Biodiversity Research

Background:

• Current understanding of coral reef ecosystems is biased towards large, visible organisms.
• The majority of reef biodiversity resides in small, cryptic spaces, forming the 'reef cryptobiome'.
• Coral reefs face significant degradation globally.

Purpose of the Study:

• To assess the biodiversity of the reef cryptobiome.
• To identify environmental drivers shaping cryptobiome communities.
• To understand the distribution patterns and rarity of reef cryptobiome organisms.

Main Methods:

• Deployment of 87 autonomous reef monitoring structures (ARMS) across 22 Red Sea reefs.
• Metabarcoding analysis of the mitochondrial cytochrome oxidase I (COI) gene.
• Community analysis of mobile and sessile subsets and their relationship with environmental factors.

Main Results:

• Identification of 14 metazoan phyla and 10,416 operational taxonomic units (OTUs).
• Distinct environmental drivers (particulate organic matter, sea surface temperature) influenced mobile and sessile communities, respectively.
• High heterogeneity observed, with only 1.5% of OTUs found on all reefs and over half unique to a single reef; most OTUs were rare.

Conclusions:

• The reef cryptobiome harbors rich and highly heterogeneous biodiversity.
• Understanding cryptobiome patterns is crucial for effective coral reef conservation and predicting responses to anthropogenic impacts.
• Conservation strategies must consider the biodiversity within cryptic reef habitats.