Deepwater coral studies reveal diversity and abundance

Shallow water coral reefs have long been the darlings of snorkelers, divers and marine biologists. Their brilliant colors and diversity of life are amazing spectacles of the bounty of the ocean. Less is known, however, about deepwater corals, aside from samples which have been brought up occasionally in fishing trawls, or from targeted oceanographic scoops of the ocean floor.

Dr. John Reed, a senior biologist at the Harbor Branch Oceanographic Institution in Fort Pierce, Fla., has been studying deepwater corals for the past 30 years and said that recent discoveries have changed all that was previously thought about these mysterious colonies. The reason: technological advances in deepwater exploration, including the use of a four-person submersible that can dive to 3,000 feet.

“All we know about deepwater colonies has come about in just the last few years; we had no idea how extensive deepwater reefs were,” Reed said in an interview the day after a deep dive in the Florida Straits. “We knew that there were deepwater reefs in various places around the world, from the waters off Norway to the Indo-Pacific, but we’re finding them everywhere now and discovering how huge and diverse they are as well.”

Reed’s passionate scientific explanations are inflected with the same effusive jubilance of many marine biologists when describing strange undersea creatures. He spends up to three hours at a time in the submersible, Johnson-Sealink, which is deployed from Harbor Branch’s ship Seaward Johnson. His work is mostly in the Florida Straits, where he has repeatedly discovered numerous previously-unknown pinnacles. After scanning the shape and location of the reefs by sonar, he explores the pinnacles in the sub, top to bottom, in total darkness, his only view of the reefs limited to the 40 or 50 feet captured in the sub’s spotlights. He studies coral growth rates (slower than shallow corals) and the myriad “critters” that inhabit the reefs.

The dives have revealed the full scale and abundance of the enormous cone-shaped mountains, rising from the depths to heights of several hundred feet. One recently-discovered pinnacle was found to be 400 feet tall. Along the slopes, which rise at a 30-40° angle, and atop the peaks, colonies of lophelia corals, the single deepwater coral species at these depths, are everywhere. Yet they play host to the same biodiversity of fish, eels, snails, shrimp, sponges, sharks and jellies – albeit vastly different species – as shallow reefs.

“We only knew bits and pieces before; now we are discovering that these deepwater reefs are as widespread and diverse as shallow reefs are,” Reed said.

By Ocean Navigator