Low connectivity between shallow, mesophotic and rariphotic zone benthos

Area of Science:

• Marine Biology
• Ecology
• Oceanography

Background:

• Coral reefs face global threats from human activities.
• Understanding deep-reef ecosystems is crucial for conservation.
• Connectivity between shallow and deep reefs is poorly understood.

Purpose of the Study:

• To investigate benthic community structure across varying depths (15-300 m) around Bermuda.
• To determine if deeper coral reefs host distinct floral and faunal assemblages.
• To assess the connectivity between shallow and deep reef ecosystems.

Main Methods:

• Utilized technical divers and submersibles for data collection.
• Surveyed benthic community structure across a depth gradient from 15 to 300 meters.
• Analyzed floral and faunal differentiation and community turnover patterns.

Main Results:

• Observed significant floral and faunal differentiation across surveyed depths.
• Identified distinct benthic assemblages at different depths, with exceptions in the lower rariphotic zone (200-300 m).
• Found highest community turnover at the boundaries of mesophotic coral ecosystems (30-150 m), driven by taxonomic turnover and nested species loss.

Conclusions:

• Mesophotic and rariphotic zones harbor biologically unique benthic communities.
• Deeper reefs exhibit limited connectivity to shallow reef systems.
• Management and protection strategies should consider deeper reefs as distinct ecological entities.