The deep ocean floor beyond the reach of sunlight provides one of nature's most impressive light shows.
Scientists from Harbor Branch Oceanographic Institute at Florida Atlantic University, Duke University, the Ocean Research & Conservation Association (ORCA), the Monterey Bay Aquarium Research Institute (MBARI), and Nova Southeastern University Oceanographic Center are using their combined expertise in bioluminescence, taxonomy, visual ecology, imaging and molecular biology to explore the environment of the deep-sea bottom to search for undiscovered "living lights" off the Bahamas.
This research expedition is taking place from July 20-31, 2009, and is funded by the National Oceanic and Atmospheric Administration (NOAA) Office of Ocean Exploration and Research. These scientists are using sensitive low-light cameras and Harbor Branch's Johnson-Sea-Link submersible to photograph bioluminescence of animals in their natural environment.
"Bioluminescence is a fascinating phenomenon that is found only in a few species on land, but is common in all the world's oceans," said Dr. Tamara Frank, research scientist at Harbor Branch's Center for Ocean Exploration and Deep-Sea Research and principal investigator and lead scientist on the expedition. "If you have ever seen a firefly, then you have witnessed the same process in action."
Animals have evolved to deal with the darkness of the deep sea through the process of bioluminescence and have developed the ability to use chemicals within their bodies to produce light. Bioluminescence occurs when certain chemicals are mixed together; the effect is similar to the soft green glow produced by green light sticks when the seal in the stick is broken.
Scientists estimate that about 90 percent of the animals living in the open waters above the sea floor are bioluminescent. However, information on living light among deep-dwelling creatures is very sparse because they are so inaccessible. Furthermore, most bioluminescent animals do not glow constantly, but rather, only light up in response to mechanical or visual stimuli. They may use bioluminescence for a number of possible reasons including camouflage, attracting prey, mating and communication. Based on the few but varied deep-sea attached animals, such as corals or sea anemones, that are known to produce light, and the adaptations in the large eyes of the some of the mobile predators discovered on previous NOAA-OER funded Harbor Branch explorations, it is likely that bioluminescence is abundant and plays a significant role in animal interactions on the deep-sea floor.
"An intriguing, and as of yet unverified idea, is that when marine animals die and accumulate on the ocean floor they are covered with luminous bacteria, which unlike other bioluminescent organisms, glow continuously," said Frank. "Bioluminescent bacteria occur throughout the marine environment, and these bacteria are known to colonize shrimp and fish carcasses, suggesting that the resulting background glow may be used as a cue by deep-sea scavengers to find carcasses."
Previous expeditions by Frank and her colleagues have explored the vision of some of these scavengers, which are crustaceans called isopods. They have demonstrated that the isopod's eyes work like a camera with a very slow shutter speed which makes them extremely sensitive to light. Frank and her colleagues have also discovered several species of deep-sea crabs that have an ultraviolet (UV)-sensitive visual pigment in addition to blue-sensitive ones. This suggests that UV sensitivity plays an important role in their ecology, and this sensitivity may also permit them to see as-yet undiscovered short wavelength bioluminescence from other bottom-dwelling organisms. UV bioluminescence on the deep ocean floor may be a novel, private channel of communication, allowing these animals to find their preferred habitat.
"Without damaging or endangering these fascinating creatures, we will be photographing them from the Johnson-Sea-Link with all of the lights off using a special camera with a very wide aperture, as well as with ORCA's Eye-in-the-Sea camera system that uses a very low light sensitive video camera. This should allow us to record bioluminescence which we are unable to see with the naked eye," said Frank.
Frank is joined by her colleagues Drs. Sönke Johnsen, Duke University; Edith Widder, ORCA; Charles Messing, Nova Southeastern University Oceanographic Center; and Steve Haddock, MBARI, on this research expedition.
The two selected locations for this expedition include the western margin of the Little Bahama Bank and a location in the Northwest Providence Channel that was last studied in 1978.