The Puerto Rico Trench and Denizens of the Deep

(Public domain - from U.S. Geological Survey)
Puerto Rico Trench. (Click once or twice for full image) U.S. Geological Survey

The Puerto Rico Trench is the deepest part of the Atlantic Ocean, and is only surpassed in its depth by the Marianas Trench in the Pacific Ocean. It is 500 miles long, and at its deepest plummets 28,232 feet down.

After receiving my doctorate with a special interest in deep-sea physiology, I was invited on board the oceanographic Research Vessel (RV) Gilliss for an expedition to the Puerto Rico Trench. I was accompanied on that research cruise by Dr. Robert Y. George, a deep-sea biological oceanographer from Florida State University.

I had been studying the effect of very high pressure on invertebrate hearts. As luck would have it, the largest population of deep-sea creatures indigenous to the deepest places in the ocean are invertebrates (animals lacking  vertebrae, backbones.) But on the way down to the deepest reaches of the trench, you encounter some very strange creatures indeed, such as the Humpback Angler Fish.

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These bizarre and frightening looking fish inhabit the abyssal pelagic zone (or the Abyss) between 13,000 and 20,000 feet. But below the water containing these abyssal fish lies the zone of the deep trenches, the hadalpelagic zone between 20,000 and 36,000 feet, the deepest point in any ocean.

“Denizens of the Deep” are known in merfolk tradition as the beasts that swallow up the sun at the end of the day, which is somewhat ironic since sunlight never reaches down to the abyssal and hadal zones. Whatever light is there, is produced by bioluminescence. Down there, light means either a meal, or a trap. And since meals are uncommon in the sparsely populated ocean depths, predators seem designed to ensure they miss no opportunities to feed. Their jaws, fangs, and other anatomical structures seem especially designed to snag a hapless passer-by, and provide no chance of escape for those caught.  Fortunately for us, animals adapted to the high pressure, low oxygen environment of the deep ocean cannot survive in shallow waters.

But imagine for a moment that something perturbed that natural order. Time has separated us from man-eating dinosaurs, but the only thing separating us from deep-sea monsters, ferocious predators that make piranhas look playful, is something as simple as pressure and oxygen.  Could things change?

Well, not to scare you, but until 1983 or so, the Puerto Rico Trench was a huge pharmaceutical dumping ground. Massive quantities of steroids and antibiotics, and chemicals capable of causing genetic mutations, came to rest on the sea floor, or were dispersed in the waters above and around the trench.

Read more about that here:

You don’t need to take just one person’s word for it. Professor R.Y. George himself commented on the issue in his resumé.

July 5 – July 30, 1977. Revisited Puerto Rico Trench (now Pharmaceutical Dump Site) aboard R/V GILLISS of the University of Miami to study Barophylic (pressure-loving)bacteria (Dr. Jody Demming’s Ph. D. work from Dr. Rita Colwell’s Lab. in the University of Maryland), and to study meiofauna, macrofauna and megafauna (in collaboration with Dr. Robert Higgins of the Smithsonian Institution).

Frankly, if I was visiting Puerto Rico, and signed up for a deep-sea fishing trip, I’d ask the boat captain just how deep we’d be fishing. I really wouldn’t want to bring up a Humpback Angler Fish large enough to eat the boat. After all, Angler Fish are fishermen too.

For a NOAA sponsored animated tour of the Trench, play the following high resolution video.


Those Curious Manganese Nodules: from Intelligence History to Science Mystery

Shortly before Howard Hughes’ massive ship, the Glomar Explorer, conducted a secret mission to recover a sunken Soviet submarine in the Pacific, under the guise of collecting manganese nodules, a much smaller Research Vessel was collecting the real thing, on the Blake Plateau about 150 miles southeast of the Georgia-Florida Coast .

Duke University's R. V. Eastward

In 1970 I was the only biologist on board the Duke University’s Research Vessel, the R.V. Eastward. Also present were geologists from the Lamont Geological Observatory, and a geologist, Dr. J. Helmut Reuter, from Georgia Tech where I was in graduate school.

There is a wealth of information on the association between bacteria and ferromanganese nodules, with some scientists convinced that bacteria precipitate manganese out of solution in seawater, thus leading to nodule creation. Arguably, the best reference on this subject is the book Geomicrobiology by H.L. Ehrlich and D.K. Newman (5th ed. 2009)


Nodules fresh off the dredge
Shipboard laboratory with decontaminated nodules

My mentors at Georgia Tech and I knew bacteria would be found coating the outside of the nodules, but we wanted to know if viable bacteria remained inside the nodules once surface contamination had been removed. My mission onboard the R.V. Eastward was to setup a small bacteriological laboratory and then search for that evidence.

Ultimately, our search was not successful. No viable bacteria were cultured.

But that is the nature of science — you don’t know until you try.

Success or not, how do scientists celebrate the end of a cruise to the Blake Plateau? Well in Nassau celebration involves fine German Beer and even finer Cuban Matasulem Rum. Yes, at the time Matasulem Rum still bearing its Cuban label could be found in the Bahamas.

Factoid for the day: Since Helmut Reuter was a geologist, he taught me that the sand around Nassau, unbelievably soft on your feet, was called oolitic sand.

Bahamas Oolitic Sand, photo credit Mark A. Wilson

 Forty years later what do we know about these curious nodules? For one thing, they are extremely slow growing, growing about a centimeter over several million years. That means the nodules in my possession are on the order of 12 million years old.

Secondly, although scientists are stimulated by the competition to discover the one correct theory among numerous hypotheses for the origin of something mysterious, such as manganese nodules, in this a case it looks like virtually everyone was correct. Nodules seem to form from precipitation of metals from seawater, especially from volcanic thermal vents, the decomposition of basalt by seawater and the precipitation of metal hydroxides through the activity of various manganese fixing bacteria. For any given nodule field, these chemical and biological processes may have been working simultaneously, or sequentially.  For any one nodule, it is presently impossible to tell which processes affected its formation.

Nodules on the Blake Plateau. Photo credit, Lamont Geological Observatory.

We should realize as we hold a 12 million year old rock in our hand, that it is far too much to expect to know details of its history over eons of time.

Manganese nodule like one in the author's collection. Photo credit, Walter Kolle.