The canopies of coral forests, an hydrodynamic perspective

Arborescent benthic organisms are ecosystem engineers which provide three-dimensional complexity to the substrate.

When multiple organisms cluster in dense aggregations, they form a forest-like seascape, called marine animal forest.

Each organism is a physical obstacle to the flow and transport is expected to be attenuated in the canopies of those forests in proportion of the canopy obstruction. Flow measurements were carried out in mesophotic coral forest-like seascapes in the Atlantic (Canary Islands, Caribbean islands) and the Mediterranean Sea (Eastern and Western). The flow velocity was recorded at high frequency (2Hz-8Hz) over 3 m above the bottom with acoustic Doppler profilers, simultaneously inside and outside aggregation patches of various species exposed to various flow types (tide, wind-driven). This comparative study evidences that significant flow attenuation in the canopy of mesophotic coral forests is a common feature.

Flow attenuation in marine animal forests generates local conditions suitable for small size species and stages, explaining the higher biomass and diversity in marine animal forests. Local flow attenuation may also enhance the resilience of the forest itself, increasing the retention of canopy forming species’ larvae and food.