Mesophotic Coral Ecosystems

Chapter 3.

Mesophotic coral ecosystems examined

3.1. Introduction

MCEs are found worldwide in tropical and subtropical waters. The existence of corals at mesophotic depths has been known since at least 1889, when Darwin reported the discovery of corals at depths of 128 m (Darwin 1889). However, it was not until the 1960s and 1970s that direct observation of MCEs began in earnest (Starck and Starck 1972, Wells 1973). As deep-diving technologies have advanced and been adopted by scientists, so has our ability to access and study MCEs. This chapter takes an in-depth look at some of the MCEs that have been studied to date (Figure 3.1) and demonstrates that while there are commonalities among MCEs, there are also differences; just as the shallow coral reefs of the Great Barrier Reef are similar but different from those found in the Florida Keys.

The MCEs discussed have a wide variety of geomorphologies. They include MCEs found on the edges of continental shelves and far from land, such as the Great Barrier Reef and Pulley Ridge in the Gulf of Mexico off the southwest Florida shelf; submerged fringing reefs and banks, such as in theUnited States Virgin Islands, the Main Palau Island group, Okinwa and the Gulf of Carpentaria in Northern Australia; canyon walls, such as Eilat in the Red Sea; and insular island shelves and submerged karst topography found in the Hawaiian Islands. Each MCE described below provides a snapshot of what is known about it, the dominant species present, any known limiting factors (e.g. sedimentation, temperature and terrigenous input) and any known impacts (e.g. hurricanes and El Niño Southern Oscillation), as well as whether there is a management regime in place. These case studies show the influences on MCEs and that there is still a lot to learn about them.

Mesophotic coral ecosystem case studies

Hawaiian Archipelago

Pulley Ridge, Gulf of Mexico

Ryukyu Archipelago, Japan

U.S. Virgin Islands

Palau Island Group

Great Barrier Reef

La Parguera, Puerto Rico

Eilat, Red Sea

Gulf of Carpentaria

Figure 3.1. Location of MCE case studies.

MESOPHOTIC CORAL ECOSYSTEMS – A LIFEBOAT FOR CORAL REEFS? 20