As divers, we have the opportunity to see some truly amazing things, and while new advances in science are allowing us to dive deeper than ever, most of us will never visit deep reefs located about 125 meters beneath the surface. Now, a new remotely operated submersible has discovered some familiar reef corals living at amazing depths – corals we might recognize if we were to go about four times as deep as we normally do.
Leptoseris Corals and More
Since we know that corals thrive in clear, fairly shallow water, it is surprising that specimens of Leptoseris coral have been discovered at a mind-blowing depth of 125 meters. Those most recently discovered live in symbiosis with algae, so scientists are curious about how these light-deprived specimens are managing to thrive away from the sunlight that sustains the algae they depend on for life.
In addition to the Leptoseris coral sample recovered from the site, which is located just off Ribbon Reef along Australia’s Great Barrier Reef, an Acropora staghorn sample was recovered from a depth of about 73 meters. The Great Barrier Reef’s coral species are normally found living at depths of 100 meters and above; deeper than 100 meters, the corals are replaced by sea fans and sponges that don’t depend on sunlight for survival. It is important that we make a distinction here between these types of light-dependent coral and corals like non-light dependent Lophelia, which thrive at depths of 799 meters and beyond, and which have been discovered in the Gulf of Mexico.
To obtain these samples, scientists working to understand how climate change is affecting the planet’s oceans launched a remote operated vehicle from their research vessel, targeting a section of deep reef located off Australia’s continental shelf. The ROV was equipped with over 250 meters of cable to provide both communications and power, and was capable of conducting a thorough search without putting divers at risk.
According to Dr. Pim Bongaerts from Queensland University’s Global Change Institute, ”It’s intriguing. When we began our survey, we were amazed to see significant coral at depths of around sixty meters. However, it is truly mind-blowing to see reef coral at more than twice that depth.” Though the corals discovered are small in comparison with those living in shallower water, and though sea conditions presented a challenge to researchers, the discovery is an exciting one that shows coral may be finding a way to survive, even though global warming, ocean acidification, and many other problems threaten reefs around the world.
No matter what the cause, it is encouraging to see that new corals are being discovered. The Great Barrier Reef has been declining for decades, with fifty percent of it having vanished over the last 27 years. “These discoveries show just how little we really know about the reef and how much more is yet to be discovered,” says Dr. Bongaerts. “Now that we have these specimens, we’ll be able to analyze them much more closely and we expect our findings to reveal a far greater understanding of just what is going on to enable reef corals to survive at such extreme depths.”