Hidden in the deep: Distinct benthic trajectories call for monitoring of mesophotic reefs

Abstract

Abstract Coral reef conservation management depends on long‐term monitoring efforts for a sound understanding of ecosystem structuring, functioning, and dynamics. However, ongoing monitoring programs are almost exclusively focused on shallow depths, and it remains unclear to what extent those represent the whole ecosystem. Here, we present a temporal comparison (2012–2017) of directly adjacent shallow and mesophotic benthic communities across seven sites from the Great Barrier Reef and the Western Coral Sea. We found a positive relationship initially between shallow and mesophotic coral cover, with higher cover at shallow depths. However, this relationship was no longer significant after multiple disturbances, with coral cover significantly declining only at shallow depths. Point‐based tracking revealed the dynamic nature of mesophotic communities, with their consistent coral cover reflecting a net balance between substantial growth and mortality. Overall, the divergent trajectories highlight the urgency to expand coral reef monitoring efforts into mesophotic depths to ensure their unique characteristics can be accounted for in conservation management strategies.

Keywords

• benthic communities
• coral bleaching
• coral reefs
• disturbances
• ecosystem recovery
• long‐term monitoring