by Edith Widder
Descending farther, I encountered many of the same creatures I had seen from Wasp: krill, shrimp, and jellies. There was also a heavy concentration of the white, flocculent marine snow, an indication of the rich planktonic life at the surface. I tried flicking off the lights briefly and immediately saw streaks and swirls of bioluminescence skidding up and over the acrylic sphere. I was torn between wanting to revel in the light show and needing to see who lived here, but, with some difficulty, I chose data over aesthetics and left the lights on.
At seven hundred feet, I slowed my descent by releasing compressed air into the ballast tank. It proved easy to trim the sub out to neutral buoyancy. The depth gauge readout was too coarse to provide the precise feedback I needed but by observing my position relative to the marine snow in the water,*2 I could readily tell whether I was too heavy or too light. As soon as I was neither, I turned out the lights, prepared to count flashes per minute with the aid of my digital watch and its push-button microlight.
I waited and watched, expectantly peering in different directions, straining to see the tiniest flicker. Seemingly interminable minutes ticked by. Nothing. In front of me was just an enormous, absolute blackness as complete as in the deepest, darkest cave. In our world, where the night is awash in light from all manner of fluorescent bulbs, streetlights, car headlights and taillights, neon signs, cellphone screens, illuminated digital clocks, and 3D Terminator nightlights,*3 not to mention natural light from the moon and stars, such all-encompassing darkness is a rarity that few have experienced and many, I think, would find unsettling.
I didn’t find it scary, but it was disconcerting, because it was so at odds with what I had expected. After a few minutes I tried tapping the thrusters, and immediately geysers of sparkling specks and fragments of living light erupted out of the propellers. Smatterings of flashes and small puffs of lucent blue clouds blossomed around the sphere, creating a vibrant halo. It was startlingly bright, because my eyes were so thoroughly dark adapted.
As the flashes faded and I was once again swathed in darkness, I tried to think about the significance of what I was seeing. There were myriad luminescent sources; they were all around me. But there was no light unless I triggered it. And all it took was the tiniest movement. I was sitting in the middle of a bioluminescent minefield!
Somehow, animals must negotiate their way through a world in which any movement can trigger a flash that will reveal their presence to the eyes of hungry predators. Imagine you are trapped in a pitch-black Superdome. There is food in the form of yummy apples dangling from strings, if only you can find them before you starve to death. Trouble is, you’re sharing this space with a hungry black panther. You can’t see him, and, in the darkness, he can’t see you. You’re safe for now, but for how long? You need to find those apples, but when you try to move, you discover tiny LEDs, also dangling from strings throughout the arena, that light up on contact. Eventually, when your hunger becomes overpowering, your search for food will accidentally trigger a flash and, with a surge of adrenaline, you will realize that the panther’s head just snapped around, fixing your exact location.
How can you possibly survive in such a world? One line of defense might be to spew bioluminescence of your own into the face of your attacker, causing a distraction and temporary blindness while you beat a hasty retreat. The fact that many animals use this trick suggests that it is, in fact, effective. Some copepods can release clouds of bioluminescence out of glands on their tails, and there are shrimp that can spew intense streams of liquid light from their mouths, like fire-breathing dragons.*4 There are squid, like the aptly named fire shooter, that discharge photon torpedoes of blinding blue brilliance. There are even a few fish that can eject sparkling dust storms of light out of a tube on each shoulder, giving them their common name, shining tubeshoulder. These defensive strategies make perfect sense when you imagine trying to play hide-and-seek in a minefield where the slightest disturbance triggers an explosion of fireworks.
As I hung there in the darkness, observing nothing, I imagined predators straining, as I was, to see any hint of a flash. How patient must they be? How patient would I need to be to observe any spontaneous luminescence? I had no doubt that it occurred, but apparently it happened on much longer time scales than I had imagined.
Also, I began to wonder, how unobtrusive was I, really, sitting here in the darkness? I had brazenly blundered into this space, with spotlights blazing and thrusters shattering the peace. Even with my thrusters off, I wondered what kind of impact the whirring of my scrubber fans might have and what kind of electrical fields might surround the sub. And, although I had made every effort to cover all the indicator lights on the control panel with a black cloth, now that I was dark adapted, I could detect tiny hints of light peeking out here and there. To creatures that have evolved to survive in such a world, I was probably about as unobtrusive as an elephant tiptoeing through a picnic.
I repeated the same observations of complete and total blackness at eight different depths. It was simultaneously intellectually intriguing and incredibly boring. Given the significant cost of this expedition, it was hard not to envision the dollar signs rolling over in my head every minute that I sat there, waiting and watching. This certainly did not seem like an effective use of my all-too-limited dive time. Also, if I was going to report zero spontaneous bioluminescence, I realized that an obvious response might be that there were just no bioluminescent animals in the vicinity. This wasn’t true, as I saw when I jabbed the thrusters. Still, just to say there was “lots of flashing whenever I moved” wasn’t going to pass muster for a science publication. I needed to figure out how to quantify the nature of the minefield.
The intensified camera might provide a solution if it could record the bioluminescence. I turned it on, aimed it out in front of the sub, and then backed up, creating a swirling light storm. The camera registered bright streaks of light, but they were out of focus and too chaotic to count. To record the bioluminescence, I needed to have the lens wide open, which meant the depth of focus was very limited. I had to figure out a more controlled method of stimulation, one that would occur in the constrained plane of focus of the camera.
Back on dry land, I conferred with Robi and his technician Kim Reisenbichler about how to meet this challenge. Robi had brought along a one-meter transect hoop—sort of a metal hula hoop—that he had been planning to secure in front of the sub in order to count the number of jellies passing through it while he motored along. If we knew the forward speed of the sub and the area of the hoop, we’d be able to estimate the number of jellies per cubic meter within a horizontal tube of ocean at this particular location. We reasoned that the same could be done for bioluminescence by stretching some fine-mesh netting across the hoop. If I focused my camera on that screen, then anything that bumped into it and was stimulated to flash would do so in focus. Kim found some five-millimeter (0.2-inch) mesh fishing net, secured it to the hoop with tie wraps, and mounted the hoop on the front of the sub.
The first time I got to try out the screen was a week later, on my sixth dive. It was a clear night under a half-moon, and the seas were calm. I kept my lights on during my descent to observe the distribution of animals in the water column. In the top two hundred feet, there were krill, small fish, and jellies. Just below them were sergestids—the shrimp on skis—and lots of the ruby octopus. I watched intently as one octopus came into contact with the sub’s dome and then squirted a stream of reddish-brown ink as it swam away. This was a different kind of tactic for distracting a visual predator, one that would seem to have no purpose in the dark but made perfect sense if it allowed the octopus to cover its tracks through a bioluminescent minefield.
As I proceeded into deeper waters, below eight hundred feet, there were large numbers of fish, especially hake, a splendid silver fish related to cod and haddock. About the size of a small scuba tank, but with a streamlined fusiform shape sporting triangular
fins, large eyes, and outsized mouths, they acted curious, cruising in close to the sub with no apparent apprehension. Just to be contrary, some animals seemed attracted to my lights instead of repelled by them.
I continued down, descending through the fish layer until I was 100 feet above the bottom in that spot, at 1,840 feet, where I trimmed the sub to neutral. This time I had brought some black electrical tape with me, and I spent some time covering indicator lights so as to make the sub pitch-black when I turned out the floodlights. I focused the intensified camera on the netting stretched across the transect hoop, shut off all the lights, and turned on the video recorder. Still no luminescence. I recorded a minute and a half of blackness until I couldn’t stand to wait any longer, and then activated the forward thrusters. Instantly, bioluminescence was stimulated as it came into contact with the screen. There were transient discrete flashes that passed through the net like blue sparks, small secretions that looked like puffs of neon blue smoke, and fragile amorphous mucous blobs that fragmented and glowed. There were a few creatures larger than the mesh size that were too slow to outswim it. Instead, they stuck to the screen and glowed, in some cases revealing their shapes, such as the long gelatinous chain of a siphonophore or the clear circular outline of a medusa.
On the camera, the scene looked like nighttime news footage of anti-aircraft fire, with streams of tracer rounds and bomb flashes exploding all over the screen. This was what my college professor meant when he described the wonder and exhilaration of discovery. Something no one had ever seen before. Finally, I was able to quantify a phenomenon never before observed in such multidimensional detail—I was actually able to say how many bioluminescent sources there were per cubic meter. But this wasn’t just about numbers; it was also breathtakingly beautiful.
I ran horizontal transects, recording the stimulated bioluminescence at different depths throughout the water column. Everywhere I looked—from surface to bottom—there was a bioluminescent minefield waiting to explode. But the nature of the minefield wasn’t always the same. Densities varied, as did the intensities and types of the light emitters. I wondered if animals had to adjust their swimming patterns based on the kind of bioluminescent obstacle course they needed to negotiate. Would an animal swim differently amid a dense array of dim dinoflagellates having a lower threshold for mechanical stimulation than it would through less abundant but much brighter copepods with a higher stimulus threshold? Or might they actively avoid certain kinds of minefields entirely? Light is the most important environmental variable in so many of our planet’s ecosystems. Down here, below the penetration of sunlight, did that supremacy still hold true?
With subsequent dives, I continued to run transects at various depths, but I also began trying to figure out who was making which displays. The classic comment of those observing bioluminescence from submersibles that “when you turn on the lights there is nothing there,” was as true as ever. Even when there was a large source stuck to the screen and glowing, if I tried to illuminate it with the floodlights, I couldn’t see anything. This was because almost all of these larger sources were transparent jellies. At first, when I observed such a display, I tried flipping on the lights and then backing up the sub to try to dislodge it from the screen so I could see it and maybe capture it with the suction sampler, but when that proved ineffectual, I adopted a different strategy—one that I think would make a good arcade game to train future submersible pilots.
Since jellies were prevalent throughout the water column and almost universally bioluminescent, I decided to focus on them. To determine what kind of display a particular jelly produced, I would steer the sub until I had the jelly lined up between the acrylic sphere and the screen. Then came the tricky bit. I would try to simultaneously turn out the lights and back up the sub, while attempting to bull’s-eye the jelly in the middle of the screen, where I had zoomed in the camera. If I got a decent recording, I would then maneuver the sub to get the jelly off the screen and in front of the suction sampler, to collect it for species identification and further study at the surface. It took some practice, but eventually I got pretty good at it and was rewarded with some unexpectedly elaborate displays.
Some firm-bodied round jellies emitted a perfect necklace of light when they hit the screen. By contrast, an exquisite crystalline jelly that looked like the top half of a hot cross bun fringed by hundreds of threadlike tentacles did something very unexpected. Whenever I lined it up to strike the screen, it would react to the water currents by contracting its margin into sharp folds, so when it made contact, it was recognizable by its un-jelly-like shape, sometimes forming a near-perfect square of light. Even more remarkable than some of the odd shapes were the incredibly elaborate flash patterns. There were comb jellies generating bands of light that propagated along their comb rows, creating a delicate tracing of a figure eight. More stunning and unexpected were the siphonophore chains that produced dissimilar displays from different parts of their bodies. The common siphonophore (Nanomia bijuga) gave a steady glow from its corncob of swimming bells, while the light emitted from its ropy, tentacled lower half scintillated. Another siphonophore, known as Apolemia, delivered brightly glowing sources from its lower half and propagated bands of light that danced along the inner stem to which its swimming bells were attached. Many of these creatures are so fragile that they had never been captured intact and no one had ever observed their bioluminescent displays before. I was witnessing a mysterious, sparkling pageant performed just for me.
The elaborateness of the displays was perplexing, especially when you consider that these creatures lack image-forming eyes. So at whose eyes were these showy pyrotechnics directed? I decided to resurrect the light wand and try again. It couldn’t imitate displays as elaborate as those I was recording, but I wondered if I might be able to see different responses to a glowing source than what I got with a flashing one. I wanted to test the theory*5 that glowing sources serve as attractants, while flashing sources act as repellents. We secured the light wand to Deep Rover for my ninth dive, which was scheduled to launch midmorning. This dive did not proceed as planned.
* * *
—
Diving submersibles, of course, does not come without risk. The four key areas of concern are the submersible itself, the launch-and-recovery system, the dive site, and the sub crew. We were pushing the envelope on all four fronts. Deep Rover was a prototype without much of a track record. The launch-and-recovery system was a kludge that depended on dangling 3.6 tons of sub from the crane hook while trying to keep it from turning into a wrecking ball by using just rope tag lines and muscle. The dive site was unexplored and the depth profile erratic, which meant it was difficult to keep from drifting outside our safe operating range. Exceeding the range is frowned upon, because if the ballast control malfunctioned, the sub could sink below what was ominously referred to as its “crush depth.” And finally, there was the sub crew.
Over many years of diving in submersibles, I have come to recognize that the sub crew is the secret sauce—the absolutely essential part of any recipe for a safe diving experience. The key ingredient for that sauce is the submersible operations coordinator, sometimes called the SOC—and sometimes “Big Daddy.” Charlie had been the SOC for my Wasp dives in 1984. For the first Wasp expedition, in 1982, where I wasn’t a pilot, the SOC was Steve Etchemendy, a.k.a. Etch. Both Charlie and Etch had many years of experience as divers and supervisors and had all the attributes that are crucial to the job description. These include strong team leadership, great problem-solving skills, especially under stress, a good sense of humor, extreme attention to detail, and a high degree of what’s known as situational awareness, preferably including eyes in the back of the head.
Peter, the SOC that Can-Dive Services (the company from which we were leasing Deep Rover) assigned to our expedition, had some of these traits, but not all. Mostly he had trouble multitasking and was deemed weak on “attention to detail” and
“situational awareness.” I was blithely unaware of his deficits, but others were not, which is why Etch had been brought in as part of the team. The original intent was for him to be with us for just the first few days, but as he became increasingly aware of Peter’s deficiencies, he kept extending his stay. He pushed it as much as he could, but he had other obligations and eventually he was called to shore. It was the day after he left that my little misadventure occurred.
With Deep Rover, we performed pre-dive checks just as we had with Wasp, to make sure everything was operational and properly secured. For this dive, José ran me through the process. He called out equipment items and control systems and ticked off the boxes on his clipboard each time I said “Check.” With the pre-dive complete, I reemerged for the last order of business, a trip to the head. There are no bathroom facilities*6 in a submersible, so this is de rigueur, whether you think you need to go or not. While I was in the head, Peter made an adjustment to the sub that nearly cost me my life.
The way it was relayed to me later was that there was a discussion in which Robi pointed out a potential problem with one of the emergency procedures. If the sub ever became entangled in something like a ghost net*7 or cables on a wreck, it would be possible to jettison the battery, frame, thrusters, and manipulators to lighten the load enough to hopefully break free. This “hull rollout” was an entirely theoretical maneuver. Nobody had ever tried it, because the risk factors were too great. With all that weight removed, the buoyancy on the sphere was such that it would rocket to the surface with enough momentum to blast through the interface and go airborne. There was no restraining harness, and not so much as a seatbelt on the pilot’s seat, so it seemed pretty clear that this “safety” system hadn’t really been thought through. However, it wasn’t the lack of a harness that Robi was pointing out; it was the fact that the hand lever we were supposed to pump to actuate the jettison would physically bang into the seawater inlet valve.
