Thriving 'middle light' reefs found in Puerto Rico

05 Jan 2011
Bright blue ascidians, known as sea squirts, are found thriving at 50m (164ft) among corals, light green algae (Lobophora), and red, orange, and brown sponges

Bright blue ascidians, known as sea squirts, are found thriving at 50m (164ft) among corals, light green algae (Lobophora), and red, orange, and brown sponges. Credit: H. Ruíz

NOAA-funded scientists have found extensive and biologically diverse coral ecosystems occurring at depths between 100-500ft within a 12 mile span off the southwestern coast of Puerto Rico.

With the overall health of shallow coral reefs and the abundance of reef fish in Puerto Rico in decline, NOAA says this finding brings hope that deeper fish stocks may help to replenish stocks on shallower reefs.

These mesophotic ecosystems (‘meso’ for middle and ‘photic’ for light) are the deepest of the light-dependent coral reefs. Too deep for exploration with traditional scuba gear, these reefs have until recently remained largely unexplored because of the cost and technical difficulty of reaching them. Advances in diving techniques allowed scientists to safely dive and conduct this pioneering survey. 

“At mesophotic depths in Puerto Rico, scientists are seeing fish species that were once common inhabitants of shallow reefs such as groupers, snappers, and reef sharks,” said Kimberly Puglise with NOAA’s Center for Sponsored Coastal Ocean Research, which funded the study. “These reefs stand in stark contrast to declining shallow water reefs in the same area.”

Because of the potential of mesophotic reefs to restore depleted fish stocks, local managers are looking carefully at adding protections for these coral ecosystems.

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