Mesophotic Coral Ecosystems

Chapter 2.

What are mesophotic coral ecosystems?

Elaine Baker , GRID-Arendal at the University of Sydney, Australia Kimberly A. Puglise , National Centers for Coastal Ocean Science, U.S. National Oceanic and Atmospheric Administration (NOAA), USA Patrick L. Colin , Coral Reef Research Foundation, Palau Peter T. Harris , GRID-Arendal, Norway Samuel E. Kahng , Hawai‘i Pacific University, USA John J. Rooney , Joint Institute for Marine and Atmospheric Research, University of Hawai‘i at Mānoa and NOAA Pacific Islands Fisheries Science Center, USA Clark Sherman , University of Puerto Rico at Mayagüez, USA Marc Slattery , University of Mississippi, USA Heather L. Spalding , University of Hawai‘i at Mānoa, USA

2.1. Introduction

MCEs are dominated by light-dependent coral, sponge and/ or algal communities that live in the middle light (‘meso’ = middle and ‘photic’ = light) zone. MCEs have often been

referred to as the coral reef ‘twilight zone’ because they represent the transition between the brightly lit surface waters and the perpetually dark deeper depths. They are

Depth in metres The mesophotic coral ecosystem

Shallow surface reefs

Approx. limit of most recreational scuba diving Shallow reefs dominated by scleractinian corals

30 m

“Upper”mesophotic coral ecosystems

60 m

90 m

Decrease in light intensity

120 m

“Lower”mesophotic coral ecosystems

Lower range for most research diving with mixed-gas equipment Upper range for most research using deep-diving vehicles

150 m

180 m

Source: Richard Pyle, unpublished data.

Figure 2.1. MCEs can form on high-angle continental and insular slopes as illustrated here, or on low-angle outer insular shelves and on the tops of submerged banks. Decreased light penetration rather than reduced temperature appears to be the primary limiting factor controlling the depth distribution of MCEs at most locations (Kahng et al. 2010).

MESOPHOTIC CORAL ECOSYSTEMS – A LIFEBOAT FOR CORAL REEFS? 11