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MISSION DISPATCH 5 July 24, 2009 Brian Cousin - @SEA Correspondent KIND PROVIDENCE 
After an 11 hour, 90 nautical mile transit we arrived at our second operations site in North-West Providence Channel. Some small islands are in sight; Burrows Cay is closest, just over a mile off our starboard bow. That wonderful turquoise/emerald water synonymous with everything beautiful about the Bahamas is clearly visible, marking where the bottom rises rapidly from over 2,000 feet below the surface to about 10 feet below, forming the Little Bahama Bank. Upon our arrival early this morning, mate Mike Schoeller and Dr. Tammy Frank conducted transects using the ship's fathometer to locate a flat spot on the deep bottom where Dr. Edie Widder's Eye-In-The-Sea camera could be safely deployed from the Johnson-Sea-Link II research submersible. After a suitable spot was found according to the fathometer, the sub was loaded up with Edie Widder in the sphere of the JSL with pilot Frank Lombardo, and Dr. Erika Raymond in the aft comparment with technician Jimmy Nelson. The EITS camera was attached to the sub's lower work platform. Just over twenty minutes after a smooth launch, JSL II arrived on the bottom at 2,225 feet. There was very little current in the water column so the sub made a descent almost straight down. On the bottom, the current measured less than a tenth of a knot. Sometimes a little current can be helpful, to clear a plume of silt that stirs when the sub touches down on a sediment bottom. After a short wait, the plume settled enough for Frank to set the Eye-In-The-Sea and lower the bait bar. The sub moved off in search of samples to collect, leaving the EITS alone to activate its low light video camera for one minute out of every five for the next two days, in the darkness of the deep sea. 
After the dive Edie reports that the site exhibited high biodiversity but low abundance of organisms, typical in the Bahamian waters. While there are many different species, there are not teeming numbers of any one. They bring back a few samples including bamboo coral and a sea cucumber that exhibit bioluminescence, but the crinoids they collected do not. Following another blue-water scuba dive, some of the divers were shuttled by small boat to shallow water on the Little Bahama Bank around Burrow's Cay to make further collections using snorkel gear only. Some plankton samples were collected that may prove useful to Dr. Steve Haddock work. THE FLUORESCENCE GUIDE TO BIOLUMINESCENCE 
Among the small planktonic organisms Steve Haddock is examining in his lab is what has been determined to be the larvae of a benthic zoanthid. Both the larvae and the adult exhibit bioluminescence. Under blue light, the larva revealed bright fluorescent spots. While the fluorescence is not bioluminescence, it can indicate the presence of bioluminescent structures that do combine different chemicals to generate light. The blue photons of the excitation light source can 'resonate' with those molecules and re-emit as fluorescence. The presence of fluorescent proteins can affect the color of emitted bioluminescence. An organism that produces blue bioluminescence in one part of its body may display a blue-green light in another part of its body where green fluorescent proteins occur along with the bioluminescent structures. 
The reasons for the bioluminescence in both stages of life may be very different. Steve suggests that bioluminescence may play a significant role as an anti-predation measure for countless larvae dispersed into the water column. Flashes of living light may startle a would-be predator allowing the tiny larvae to escape. The larval zoanthid in Steve's lab actually has a fin capable of moving it through the water. In its adult stage, it is a sessile organism and the function of its bioluminescence is more of a mystery. It cannot elude its predators by moving away. The zoanthid, in the golden coral group, may use bioluminescence as a 'burglar alarm' to attract a predator that would chase after whatever is trying to attack it. Perhaps some of the discoveries made as a result of this cruise will begin to unlock some of these secrets of living light in the deep sea. A big puzzle that Steve is trying to solve is how and why species became bioluminescent in the first place. In the evolutionary tree, bioluminescence occurs multiple times in the lineage of animals. He cites the phylum Cnidaria as a group that includes thousands of benthic (bottom-dwelling) and pelagic (mid-water) bioluminescent species. Some use the chemical luciferin and one of a number of species-specific luciferases to generate light while others use photoproteins. Studies show there are several independent instances when different species of cnidarians became bioluminescent, and the phenomenon is not traceable to a single evolutionary event. 
Tissue from samples Steve and the science team collect on this mission will be preserved for genetic studies back in his lab at MBARI. A genetic tree of proteins involved in bioluminescence may emerge to answer some of the many questions about this fascinating phenomenon. |
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