Volume II - No. 3
NATURE TRAILS UNDER THE SEA
By H. S. Ladd,
Nature trails have become more and more in recent years a subject for study and planning by recreational technicians who seek to provide, for both professional hiker and casual stroller, the most direct contact possible with the eye-filling phenomena of the out-of-doors.
A good trail appears to wander carelessly through the woods and the visitor who follows it often is amazed at the ever-changing succession of objects of biologic and geologic interest past which he thus is led. Inclusion of most of these features is due to careful planning, but some of them -- such as unusual plants -- have been moved up a little perhaps so that they may be seen clearly from the trail. Various items are labeled or explained briefly by small lettered tags and he who walks slowly will find much to arrest him. He will learn the names of plants, see rock outcrops and learn how soil is formed, and he may even come upon four-footed animals in cages or a hawk moving freely except for a leather thong around its leg. Such is the conventional nature trail.
It is our purpose now to describe a somewhat less conventional trail, an unmarked path on the sea floor instead of on the land, a trail where careful planning is not necessary, where everything is new and strange, where tags and labels are not present, much as the visitor may need them. We are not old hands at walking on the sea floor for we have tried it only once. The experiences, therefore, are those that the reader would have should he allow someone to place a "Divinhood" over his head and man the pumps.
One of our jobs during a recent trip to Florida was to examine the coral reef area included within the boundaries proposed for Everglades National Park. We wished to determine whether it duplicated other reef areas already owned by the federal government in the Marquesas and Dry Tortugas. The area in question lies off Key Largo, 30-odd miles south of Miami. Through the courtesy of Captain C. C. von Paulson, of the United States Coast Guard, we were able to obtain an excellent general view from the air and on the next day we set out in a launch to make a closer inspection. We were equipped with a glass-bottomed bucket and with diving helmets lent by the Coast Guard and the University of Miami. Professor E. M. Miller of the University and two of his students, all of them familiar with the reefs of the area, accompained us. When we reached Turtle Reef, near the center of the proposed Everglades reef area, we used the glass-bottomed bucket to select a rich looking site, anchored in 12 to 15 feet of water, and prepared to go overside.
Clad in a bathing suit and tennis shoes, the diver climbs over the side of the launch and descends several rungs on a heavy chain ladder until his shoulders are level with the rail of the boat. The attendant lowers the helmet over the diver's head and, as he does this, the diver passes his right arm through a loop in the rubber air hose. The diver adjusts the helmet with its lead weights on his bare shoulders and descends another rung or two on the ladder. As the margin of the helmet approaches the water the attendant starts the pump and a stream of air pours into the helmet. The air keeps the water level down to the diver's chin as he continues his descent of the ladder.
The diver's first feeling as he "goes under" is one of mild surprise when he notes that the air stream does keep the water surface around his chin -- just as the instructor said it would. It is reassuring, too, to note that there is ample air to breathe. The diver's attention next is called to his legs which, on the flexible ladder, show a disturbing tendency to assume a horizontal attitude in front of him. Recalling the rope ladders of gymnasium days, he lets his arms take some of the weight off his feet and the ladder straightens downward. He now realizes that the bright sunlight is gone and that he has entered a new world wherein everything is greenish; even the squat hull of the launch rocking above him is tinged with green. His feet touch bottom and his body sways slightly as he releases his hold on the ladder. He stands on a smooth patch of white sand, but irregular, hummocky areas almost isolate it from similar patches some distance away. Rising from these irregular areas and scattered widely over the sands are brightly colored sea fans a foot or more high, and waving plume-like forms that he knows are animals in spite of their plant-like appearance. He has an urge to touch these things just to see how they feel. Catching the hand of his instructor, who has preceded him to the sea floor, he starts to walk toward the nearest clump. He discovers that, unaccountably, it is difficult to maintain his course. Some unseen force is gently carrying him off to the left. Despite his efforts he continues leftward in a graceful drift -- a type of motion experienced previously only in dreams or when slightly intoxicated. The instructor tightens the grip on his hand and there comes the realization that he is being influenced by surface currents. He decides he must learn to walk just as a child does and concentrates on putting one foot out past the other with slow deliberation.
His attention is distracted by a school of angel fish swimming directly toward him. At a distance of about 10 feet they turn to his right and, following directly behind, is a vividly colored queen angel fish. He releases the instructor's hand to watch. The school disappears and he suddenly realizes that he can see little or nothing. The windows in the helmet have been rendered opaque by a film of moisture from his breath. He considers tilting the helmet, a means of clearing the glass previously suggested by the instructor, but he decides on a simpler method. Gulping a mouthful of sea water he squirts it, first on one pane and then on the other. The windows clear miraculously and vision returns. This feat brings great confidence and, without assistance, he begins to plod toward the nearest clump of fans. Remembering that he must not bend over, he squats and feels of the surprisingly stiff and somewhat rough surface of a fan. Nearby is a waving purple plume, beyond it a massive hemispherical head of coral -- another -- and another. Near them are drab sponges and other forms whose branches reach upward-like hands fastened to the sea floor. Brightly colored fishes hover near the corals, their fins swaying gently, their mouths and gills opening. Completely at home now, the diver is amazed at the variety of growth that meets his eye. He begins to explore with firmer steps. He carefully avoids the long spines of a sea urchin that project -- slender and sharp -- from a crevice beneath an old coral block. He comes upon the instructor busily engaged in prying up a small coral head with the blade of a hatchet. The head is loosened and dropped into a wire basket that has been lowered from above. So he wanders in a submarine garden where living plants and animals grow on shells, rocks and coral sand. Finally, at a sign from the instructor, he heads for the ladder and begins to climb upward into a brighter but somewhat less interesting world.
The sea floor upon which we walked is part of a shelf that fringes the keys on the seaward side. This shelf has been described as a submerged coral reef and it is probable that reef corals played an important part in its formation. Today, however, the role of the corals is relatively unimportant. Heads of reef corals -- some of which are several feet in diameter -- occur on the surface of the shelf but they are widely scattered. They are somewhat more numerous near the seaward edge than elsewhere but even in this area they cover but a small part of the surface and add but little to the sediments that are accumulating. Flourishing coral reefs, such as that shown on the opposite page, are wave-resisting structures whose seaward margins bear a more or less distinct rim ("Lithothamnion Ridge") that is literally covered with a growth of corals and calcareous algae. In reefs of this type the corals add bulk and the algae bind the heads together. The shelf that we examined is not bordered by a rim of this kind. The important organisms at Key Largo are the gorgonians -- the sea fans, sea whips and sea feathers. Those pink, yellow, brown, and purple near-relatives of the stony reef corals are sometimes called the "flexible corals". In our opinion they make a far more beautiful sight than do the true corals of the open-sea reefs. In many areas the true coral reefs are laid bare at low tide. One may walk with crunching steps over acres and acres of living corals. On exposed reefs, however, the retreating tide leaves everything limp and contracted. Except in tide pools the coral polyps and anemones become slimy masses of formless jelly; the fish are gone, the mollusks hidden under stones. When one walks under a diving helmet all the organisms are expanded and waving. The submerged reef is superior to the exposed reef just as the latter is superior to a collection of dried specimens in a museum.
Reefs of all kinds are structures of great interest to biologists and geologists. The biologist is concerned primarily with the living organisms that veneer the surface of the reef, the geologist in the contributions that each type makes to the reef mass. The geologist is interested also in the organisms for it is his task to identify the fossils found in ancient elevated reefs and to try to determine how such reefs were formed. It seems clear that at Key Largo at present the gorgonians are adding more to the reef than are the true corals. Such is certainly the case in the Dry Tortugas where it has been estimated that the tiny stony spicules from the tissues of the living gorgonians aver age at least 5.28 tons to the acre. (1). The author who made this estimate stated that in many parts of the Dry Tortugas at depths of 15 to 30 feet the reefs were covered with a shrub-like growth three feet or more in height, compared almost entirely of gorgonians.
Since returning from Florida we have described our submarine jaunt to a number of friends. Almost without exception they have expressed some amazement at what they considered our daring. "Suppose", said several, "you had met a shark or a barracuda?" "Suppose," said another, "your hose had become twisted -- or something happened to the man at the pump." One even asked if we were not worried about contracting a case of "the bends!" We hasten modestly to deny the accusation that we are brave men and to insist that the hazards of crossing the street in peaceful Richmond are at least as great as the dangers of walking among the gorgonians. So far as we know, neither shark nor barracuda has ever stolen a meal from beneath a "Divinhood."
To attempt to deny the theoretical possibility would be useless but let us consider some facts. One of us has witnessed the attack of a barracuda and, at the risk of frightening the more timid, we shall describe the experience. It is well known that the big fish lurk near passages through the reefs. In the South Seas when a launch or cutter enters a lagoon with a fisherman on board he almost invariably puts out a line in the hope of a strike. On the occasion that we are telling about the fisherman hooked a four-foot shark which proceeded to put up a strenuous fight. Suddenly, at the end of a magnificent surge, he leaped clear of the water and thereafter all fight departed. He was hauled aboard the launch and the reason became clearly evident. In spite of the toughness of his rasping hide, he had been neatly -- and completely -- disemboweled by a barracuda. The teeth marks were truly impressive. This event occurred at the entrance to the lagoon of Fulanga, a small horseshoe-shaped island in eastern Fiji. The central lagoon of this elevated atoll is several miles in diameter and is entirely safe for bathing. Ladd swam in it nearly every day for three weeks and his native friends there have been doing the same thing all their lives. They swim all over the lagoon yet no one has ever been attacked by shark or barracuda.
As to the other objections: (1) if anything goes wrong with the hose the pump or the pumper one can easily duck out from under the helmet and head for the surface. The helmets are easy to handle for they are not heavy in the water. (2) There is no danger from pressure as no one attempts to use a helmet below a depth of 30 feet. If a slight effect on the eardrum is noticed in ascending or descending one can obtain instant relief by waggling the jaws and swallowing.
If the proposed Everglades Park becomes a reality, the coral reef will undoubtly prove one of its chief attractions. Many of its features can be seen clearly through a glass-bottomed bucket or a glass-bottomed boat but neither of these methods can compare with the diving helmet. Students of zoology at the University of Miami make numerous trips to the bottom as a part of their regular work. Nature trails of this kind would offer an added attraction at Fort Jefferson in the Dry Tortugas. It is true that there are barracuda there -- we caught a fine one during our visit! -- but they will not bother divers in shallow water. As proof of this we should like to point out that the Carnegie Laboratory on Loggerhead Key first used diving hoods around Fort Jefferson more than 20 years ago. (2).
(1) Cary, L. R., The Gorgonaceae as a Factor in the Formation of Coral Reefs, Papers from the Department of Marine Biology, Carnegie Institute, Washington, Vol. 9, pp 341-362, 1918.
(2) Cary, op. cit. p. 352.
|<<< Previous||> Contents <||Next >>>|