Bart Shepherd and Luiz Rocha were going the wrong way if they wanted to find a reef. Off the coast of Anilao in the Philippines, the biologists were diving---and diving, and diving---deep into the murky waters. Propelled by scooters, torpedo-like machines like the ones Sean Connery and Nicolas Cage used to infiltrate Alcatraz in The Rock, they dove 100 feet down. Then 200, then 300. It got darker and darker until they at last reached a reef clad in blackness, 400 feet below the surface, swarming with invertebrates and fishes illuminated by the divers' beams.
There was even coral, which shouldn't make a lick of sense. A coral reef is supposed to be a bright blue, glimmering world, with flashy fish and maybe a sea turtle or two. It's an ecosystem absolutely dependent on the sun: Corals have a symbiotic relationship with photosynthetic algae, which need sunlight to thrive and pump out nutrients for their hosts. But not deep reefs like this in the so-called "twilight zone," the waters between 150 and 500 feet deep. They operate with little light or, if waters grow murky, no light at all. Yet a reef still flourishes.
These deep reefs are some of the least explored ecosystems on Earth---as in, almost entirely unstudied. Shepherd and Rocha, who returned to their home base at the California Academy of Sciences late last month, are among a handful of scientists who have visited a reef like this, much less studied one. You see, these depths historically have been too shallow to justify the expense of sending a sub, yet too deep to pull off safely with scuba gear. That’s finally changing: New technology makes it safer for divers to stay submerged as long as seven hours, so now scientists with the requisite funding (and nerves) can explore the deep reefs and see what no human has ever set eyes on. Their findings are revealing a strange ecosystem, where fish prefer to dress in red and coral grows with little sunlight---a reef that, like its shallow-water counterparts, could be in serious trouble.
Your typical bright, shallow reef begins with the sun, which feeds algae, which feed the proliferating corals that in turn provide shelter for fish, which attract predators like sharks. The whole chain is dependent on the sun. But deep reefs clearly thrive in low light or even darkness, so how do their ecosystems still churn? Well, in a way, the sun still powers them.
“Those reefs that we went to in the Philippines, the surface water was so murky that at 400 feet, even diving at 11 in the morning it was like a night dive,” says Rocha. “There was no light whatsoever, and every coral we saw were ones that feed only on plankton.” Shallow-water corals will also feed on plankton, but are very much dependent on algae as a source of energy---in the absence of light and algae, the coral here have come to rely entirely on plankton.
But that doesn't mean they don't depend on the sun. It just takes a couple more steps for corals to gain access to its photonic energy. Plankton is made of tiny animals called zooplankton, which feed on their counterparts, plant-like organisms called phytoplankton. These phytoplankton typically float at the top of the water column to absorb sunlight.
This is a dangerous place for zooplankton during the day, what with their own predators about. So zooplankton hang out in the dark depths when the sun is up, then ascend at night to feed on the phytoplankton under cover of darkness. Sunlight makes its way into the phytoplankton, which make their way into the zooplankton, which in turn end up as coral food when they descend into the deep. The ecosystem gets its energy from the sun, however indirectly.
And it's thriving, packed with creatures specially adapted to life in the dark. Fish here, for instance, tend to have bigger eyes to gather the scant light, and “a lot of them have a sort of red, orange color,” says Shepherd, “because that spectrum of light doesn't exist where they are. And so they disappear, they turn grey, blue, black when they're that color.”
Shepherd and Rocha also stumbled across two gorgeous and peculiar invertebrates (one shown at left) known as ctenophores, or comb jellies, which aren’t really true jellyfish. Comb jellies typically wander casually through the water column, but these two had attached themselves to fishing line tangled in the reef (you may not have known this place exists, but fishermen certainly do). “They actually take their mouthparts and they have these folds around the oral end of their body and they wrap it around something and hold on to it,” says Shepherd. “And then they put these two sort of finger-like lobes into the water and there's tentacles that come out of them that they use to feed” on plankton. Shepherd and Rocha were even able to bring them back to the Academy of Sciences in San Francisco alive, along with 15 fish---the latter of which required the help of a very special device.
It’s not that it’s particularly bad for the human body to briefly be 400 feet below the ocean surface. Where it really gets dangerous is in the ascent. Do it too quickly and you'll get the bends---the excruciating formation of nitrogen bubbles in tissues and blood---so Shepherd and Rocha had to stop at predetermined depths as they ascended, beginning with short breaks that got progressively longer. “You've got one minute at 180 feet,” says Shepherd, “one minute at 140 feet, two minutes at 100 feet, four minutes at 80 feet, and then it just keeps building until you have this two hours at 35 feet.”
Two hours in one spot. To fend off insanity on these kinds of dives, Shepherd and Rocha practice catching fish or swimming backward or testing a waterproof iPad case by playing Angry Birds. It takes so long that they’re afforded no longer than 20 minutes---and sometimes as few as 10---exploring the deep reef before they must ascend and decompress. (Spending this much time underwater is only possible because of technology known as a rebreather, which takes exhaled air, scrubs the carbon dioxide, and cycles the air back through.)
Things get even more complicated when divers try to bring live fish back up with them, because fish don’t respond to the same decompression schedule that a human does. They have an air-filled organ called a swim bladder, which helps them control their buoyancy so they don’t have to waste energy correcting their position up and down in the water column. “The swim bladder is an analog to our lungs, but it doesn't have a connection to the environment, so it's just a bubble inside the fish,” says Rocha. “And as they come up it increases in size unless the gases get diffused back through the bloodstream, or unless you use a needle” to pierce the swim bladder. If you don’t, the fish’s eyes bulge out as the swim bladder shoves its stomach out of its mouth. As you can imagine, this is somewhat traumatic for the fish.
Academy scientists came up with a clever solution: a portable decompression chamber that biologist Matt Wandell cobbled together with off-the-shelf parts. It’s pretty simple, really. Rocha and Shepherd carried a tube with them---actually your run-of-the-mill water filter canister you’d have at home. When they found a fish they wanted alive, they’d net it, jam it in the tube, and seal the thing up. As they ascended, the pressure in the water-tight chamber remained as it was at-depth, sparing the fish inside all that nasty eye-bulging and stomach-regurgitating.
Back on land, one of their no-doubt-sleep-deprived colleagues would check on the fish every two hours for around 24 hours, slowly releasing the pressure until it matched that at sea level. This allows the gas in the fish's swim bladder to diffuse gradually, with far less trauma. Thus acclimated to the pressure, 15 deep-reef fish now swim in an open tank backstage at the Academy of Sciences in San Francisco, where they’ll be featured in a twilight-zone exhibit opening summer 2016.
Back in December, I did a series of stories exploring the cavernous collections at the California Academy of Sciences: millions of specimens gathered in the field, now kept in jars and pinned to boards. This did not make some readers happy. They couldn’t understand how killing creatures could possibly further the cause of science. But the fact of the matter is collecting and cataloging animals---or, better yet, keeping them alive to observe them---is indispensable to science, especially in this age of human-induced mass extinction.
Coral reefs in particular are in serious trouble, and when it comes to understanding an ecosystem like this, there’s simply no substitute for collecting fish. On this trip, Academy scientists collected nearly 100 specimens in addition to the 15 live ones. This way, they can at any time in the future pull the specimens from the collections to compare them to other species. That information is invaluable. These reefs are so rarely studied that science could well be in danger of losing the deep reefs before it can fully understand them.
While a lot of these deep reefs are washed over with cool upwelling waters, perhaps staving off the harm that warming waters will do to the shallower reefs (bleaching, for instance, and more outbreaks of disease), the big problem will be acidification, which spares no coral. The staggering amount of carbon dioxide we’re pumping into the atmosphere is absorbed in part by the oceans, acidifying them. Indeed, since the Industrial Revolution, Earth’s seas have grown 30 percent more acidic. This monkeys with a developing coral’s ability to build its skeleton, which is made of calcium carbonate, and can even erode existing corals. And the prognosis doesn’t look good: Within the next three or four decades, coral reefs could begin eroding faster than they’re able to grow.
Then again, any number of other extinction events in Earth’s 3.5-billion-year history of life show that where some species perish, others flourish. Ideally, humanity could check its carbon output---but if that's impossible, perhaps all is not lost. “I like to think corals have been around for a really, really long time," says Shepherd. "They're amazingly resilient, plastic animals. And things will probably change, communities will change, species will go extinct, other species will thrive. It's hard to say in the long term what that will look like.”
Things will undoubtedly be different on the deep reefs a century from now, which is all the more reason for scientists to study them now in their more-or-less pristine state. So here’s to revealing the secrets of the deep reefs---20 minutes at a time.
