When most people think of “coral reefs”, they imagine vast expanses of stony (scleractinian) corals on brightly-lit shallow reefs in tropical seas. Indeed, such corals and the reefs they help build have garnered enormous amounts of scientific and popular attention — and with good reason. Coral reefs provide food for millions of people, protection of coastlines from storms and large waves, and harbor tremendous biodiversity. Moreover, corals are under tremendous threats, including ocean acidification (impacting the ability of corals to produce their stony skeletons), ocean warming (leading to coral bleaching, which is happening at unprecedented rates around all tropical seas), pollution, overfishing, and sediment run-off from shore-based activities.
However, this perspective of coral-reef ecosystems is based on the shallowest 100 feet (30 meters) of coral-reef environments, which is where the vast majority of exploration and research has historically occurred. The main reason so much scientific effort has focused on these shallow reefs is largely a result of the limitations of conventional SCUBA gear, the primary tool used by coral-reef biologists. To access deeper depths, researchers have relied on other technologies, such as deep-see submersibles, remotely operated vehicles (ROVs), and remote sampling methods such as traps and trawls. Unfortunately, traps and trawls are not particularly effective on rocky coral-reef environments, ROVs are extremely limited in their ability to collect specimens, and submersibles are extremely expensive to operate. As a result, these technologies have focused almost entirely on habitats well below the lower depth limit of coral-reefs.
Starting in the late 1960’s, scientists began to realize that coral-reef environments extended much deeper than previously thought. A few scattered studies, mostly involving submersibles, conducted in a few specific areas (parts of the Caribbean, Hawaii, Marshall Islands and Red Sea) provided initial glimpses of these deeper reef habitats; however, for the most part they were largely ignored. Beginning in the late 1980’s Bishop Museum scientists embarked on a pioneering effort to explore deep coral-reef habitats throughout the tropical Indo-Pacific, using advanced mixed-gas diving technology that allowed safe access to the deepest coral reefs. In the decades since, we have documented rich and complex reef-associated communities at dozens of locations, and have discovered more than a hundred species new to science. In recent years, thanks in large part to the discovery of extensive deep coral reefs in both Hawaii and the Gulf of Mexico in the mid 2000’s, there has been a dramatic increase in scientific attention focused on what are now called “Mesophotic Coral Ecosystems” (MCEs), defined as coral-associated communities at depths of approximately 100-500 feet (30-150 meters).
Bishop Museum’s efforts to explore and document these MCEs, also known as the Coral-Reef “Twilight Zone”, are ongoing and expanding, and we are proud to have played such an important role in bringing these diverse and mysterious ecosystems into the scientific spotlight.
Dr. Richard L. Pyle
One of Dr. Pyle’s current research interests involves using advanced diving technology to explore and documenting coral-reef ecosystems at depths below 100 feet (30 meters), down to the lower boundary of so-called “Mesophotic Coral Ecosystems” (MCEs), also known as the Coral-Reef Twilight Zone. He is a pioneer in this field, with over thirty years of experience leading expeditions to explore deep coral reefs throughout the vast tropical Indo-Pacific region, discovering hundreds of species new to science.