Environmental DNA in a global biodiversity hotspot: Lessons from coral reef fish diversity across the Indonesian archipelago

Abstract

Abstract Indonesia is the heart of the Coral Triangle, the world’s most diverse marine ecosystem. Preserving the biological and economic value of this marine biodiversity requires efficient and economical ecosystem monitoring, yet our understanding of marine biodiversity in this region remains limited. This study uses environmental DNA (eDNA) to survey fish communities across a well‐documented biodiversity gradient in Indonesia. A total of 6,608,693 sequence reads of MiFish 12S rRNA from 39 sites spanning seven regions of Indonesia revealed 1099 fish amplified sequence variants (ASVs), 80.4% of which could be identified to species. Regional fish diversity broadly conformed to expectations, with the highest fish biodiversity in Raja Ampat and lowest in Western Indonesia. Similarly, zeta diversity analysis showed greater community turnover in higher diversity reefs of Eastern Indonesia and greater community similarity in low diversity regions of Western Indonesia. However, despite a twofold difference in fish diversity between Eastern and Western Indonesia, mean ASVs recovered per 1‐L seawater was relatively similar across all regions. Moreover, although ASV recovery from individual seawater samples saturated, ASV recovery did not saturate at the site or region level, indicating that sampling/sequencing efforts employed in lower diversity ecosystems are insufficient for biodiversity hotspots like the Coral Triangle. Despite these limitations, eDNA substantially increased (36.3%–84.1%; mean 57.1%) the number of fish species recorded during intensive visual surveys, adding pelagic (tuna, jacks, scads, mackerels), nocturnal (soldierfish, lanternfish), and crevice‐dwelling species (eels, blennies, gobies) that are difficult to document in visual surveys. Results demonstrate the added value of eDNA in biodiversity hotspots like the Coral Triangle and highlight the need for research to understand how best to sample eDNA in high diversity regions to deliver on the promise of eDNA as a tool to monitor marine biodiversity effectively and efficiently.

Keywords

• biodiversity
• biomonitoring
• Coral Triangle
• eDNA
• fish
• marine