October 9, 2011 | 20
For years, ripples at the surface of the Dead Sea hinted there was something mysterious going on beneath its salt-laden waters. But in a lake where accidentally swallowing the water while diving could lead to near-instant asphyxiation, no one was in a hurry to find out what it might be.
This year, some intrepid divers changed that, stumbling onto a geological and biological treasure and capturing it on video. We’ll get to that in just a moment.
This is the Dead Sea. As you can see, it appears quite dead. There are no plants, fish, or any other visible life in the sea. Its salt concentration is a staggering 33.7%, 8.6 times saltier than ocean water, which is only about 3.5% salt. The stones at the water’s edge encrusted in salt are a good clue in that department. As a result, the Sea is famous for its body buoyancy properties, as people who take an exploratory dip generally find themselves riding high on its waters.
The Dead Sea is also the lowest point on earth, and getting lower every year, as water that would ordinarily fill it by flowing in from the Jordan River has been diverted to quench the thirst of Israel, Jordan, and Palestine. Every year, the lake drops over a meter per year. If this goes on long enough, the Sea could face Owens Lake’s and the Aral Sea’s fate: becoming a wind-swept salt flat. Yet, for now, life goes on.
Biologists have known since the 1930s the lake is “not dead yet”. Instead, it’s full of microbes that get along quite happily in the salty soup, for it keeps out competitors that would take over in a more hospital aqueous environment. In general, the water contains 1,000 to 10,000 archaea* per ml, a much lower concentration of life than in seawater, but quite respectable, all in all, for a place where one molecule in three is not water. Occasionally, when conditions are right, the sea blooms red with life. This happened in 1980 and 1992.
In any case, divers from Israel and Germany finally braved the waters this year to see what might have been causing the aforementioned concentric-ringed ripples observed near shore. They were not disappointed. This is what they found (hit the button at the bottom right corner of the youtube player to watch it in uber-super-cool full screen mode):
These are freshwater springs, jetting into the bottom of the Dead Sea from inside craters. Found as deep as 100 feet from the surface, the springs lie at the base of craters as large as 50 feet wide and 65 feet deep. As can be seen, a variety of interesting geological formations surround them.
The springs roil the waters they flow into in a phantasmal slipstream. Starting at about 2:00, you can see it coiling and mixing like it’s hundreds of degrees hotter or more sugary than the surrounding water. But no, it’s just that much less salty (and dense). (There’s a famous scene in the “Caves” episode of Planet Earth that vividly illustrates salinity gradients (haloclines) in the cenotes of Mexico too — go track down a copy if you can).
What makes this place biologically amazing was the life they found near the plumes.
The top of the springs’ rocks are covered with green biofilms, which use both sunlight and sulfide—naturally occurring chemicals from the springs—to survive. Exclusively sulfide-eating bacteria coat the bottoms of the rocks in a white biofilm.
Bacterial mats or biofilms have never been found in the Dead Sea before. You can see the films of green photosynthetic bacteria on top of a rock and a film of white sulfide-oxidizing bacteria underneath it in the very last scene of the movie. Go have a peek.
Not only have the organisms evolved in such a harsh environment, Ionescu speculates that the bacteria can somehow cope with sudden fluxes in fresh water and saltwater that naturally occur as water currents shift around the springs.
Ionescu further pointed out that all known hard-core halophiles, or salt-loving microbes, die if you put them in freshwater, and vice versa. How these microbes are able to withstand what must be wicked shifts in salinity on an ongoing basis is anyone’s guess. This reminds me of the creatures at deep sea vents that must withstand massive fluctuations in temperature as ventwater hundreds of degrees hotter than the surrounding seawater shifts back and forth. I’ll say it along with Jeff Goldblum once more: “Life finds a way.”
Whatever they are — and scientists are planning to go back to find out more — they are not like the microbes found in the rest of the sea nor like the organisms that cause the sea to occasionally bloom red. And they are very diverse — much more so than their halophilic neighbors.
The article also notes that the Dead Sea’s waters are particularly caustic and difficult for divers, which, as a new diver myself, I found particularly interesting/horrifying. In addition to having to weight yourself down incredibly — on the order of 90 pounds; when I dove in Hawaii last year, I used about 12 pounds — Dead Sea water is not something you want coming into contact with your face. Ever.
Divers will also need to wear full face masks to protect their eyes and mouths. That’s because accidentally swallowing Dead Sea salt water would cause the larynx to inflate, resulting in immediate choking and suffocation.
Likewise, the intensely salty water would instantly burn and likely blind the eyes—both reasons why Dead Sea swimmers rarely fully submerge their bodies, Ionescu noted.
I well recall practicing losing, replacing, and clearing my mask of water at depth when I was getting certified. I guess in the Dead Sea, that’s more of the nuclear option in case of leak or “wardrobe malfunction”.
*Archaea are a fascinating and huge group of bacteria-like organisms that were only discovered in the 1970s by biologist Carl Woese (“Woes”). If you don’t know about archaea, you should learn more. Trust me.
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