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The Dry Tortugas: The Coral Reefs

Harper's New Monthly Magazine

1868

A most singular and beautiful feature of the waters of the reef is seen at times when the whole ground is visible for miles around. Rich shades of green and purple mark distinctly where the shoal beds of coral are separated from the dark indigo of the deeper channels. Every thing is mapped out as plainly as in a colored drawing. The great heads of meandrina or brain corals, and the sea fans and feathers, brown and purple, are plainly seen. Frequently some large dark spot, darker than the rest, moves away, and as it approaches you see the form of the great Whip Ray sauntering along, dipping his nose in the mud, and sending terror to the sardines and little fry upon the surface.

A cursory or general view of the Tortugas Reefs presents many interesting scenes. We will take views from the parapet, from the breakwater, or as we float slowly over the reef and channels, and on other occasions stop to examine more closely the curious forms of animal and vegetable life that abound here.

Over certain dark spots, rods in extent, made dark by millions of sardines and other small fish, the brown pelican is ever seen. Patiently, from early morn until the last ray of daylight has passed, he fishes for his own and his family's subsistence. With his great dipnet bill one would think that he might easily and quickly gather a sufficiency; but he is blessed with a large appetite and little skill. Occasionally at mid-day these birds sit dozing on the broken coral of the reef where the water is shallow; and every stake or piece of wreck is sure to have an occupant. A species of gull seems to depend for its subsistence on stealing from the pelican. Nearly every one is accompanied by one of these gulls (never by two), and immediately when Pelican dives, if he catches any thing not without Gull settles upon Pelican's great round head or neck, and snatches a morsel from his pouch. Pelican has to toss his fish and turn it so as to adjust it properly for swallowing, and Gull takes advantage of his clumsy catering to help himself. Poor Pelican never seems to mind it; but flaps his great wings until he has risen a few feet, poises himself for an instant, and drops again head first with a heavy splash, to hit or miss as is his wont.

How exactly opposite is the activity of the little Tern that is fishing near by, darting here and there like a swallow, its long forked tail arrow-like in its passage, now suddenly checked, pausing and quickly plunging half its length straight into the sea; and quickly up again, nervously peeping downward, chirping like a sparrow, the busiest little body around. Then there are the Laughing Gulls; how they chatter and ha-ha among themselves; they are very sociable fellows, and are very pretty; the Monk's-head, and the Black-cap, and Red-bill; and then the great dray Gull comes soaring over, to see if there is any thing worth picking up. Lazy fellow, and stupid, for he will not dive or hunt. Away over on the shoals, near Bush Key, are several great White Herons or Cranes, that stand or mope about and watch for some luckless shell-fish. In the small mangroves near are nests of the Pelican, made of coarse sticks, and, in the season, adorned with two chalky, white eggs.

When the trade-wind blows stiffly from the eastward numbers of long, slender, swallowtail birds Frigate-birds hover over the fort, and although the wind may amount to a gale these birds remain over the same spot, swaying gently from side to side, but never, apparently, moving their wings. In moonlight nights, and in dark nights, as well as in the day, these birds are seen in the air. It has occurred to me that these birds are represented by a kite gravity operating to prevent their going off before the wind. They tilt gently as on a pivot, presenting the least surface to the wind, which buoys them up, and ever keep the body so poised that the tendency is to go downward and forward. How else can we explain this marvelous phenomenon? This bird is called among the wreckers "Man-o'-War Hawk;" its systematic name is Tachypetes aquilus.

During the winter months the weather is much like the pleasant dry days of our Northern summer; Little or no rain falls, and the charming, bright, sunny weather is only interrupted by an occasional "norther," when the mercury drops slowly down from its usual point at 75° nearly to 60°. There are days when, after weeks of steady trade-wind from the east, when boating has been indulged in joyously, the ensign veers round gradually to the southward, and then droops inactive by the staff. The quicksilver has risen to a point marked by Fahrenheit 85°. The sea is like a lake of glass. No sound is heard but the light plash of the ocean border as it flaps upon the outer reef; or an occasional dash of the clumsy pelican. The deep channels are dark with their characteristic blue, and the reefs give purple and lilac to the shoal water above them. Zigzag ripples are formed here and there behind the great sickle-fin of the shark, as his huge form sculls slowly along just under the surface. The setting sun is enthroned in gorgeous colors. Ermined clouds float in the back-ground, upon which are lighter fabrics, fringed with gold and gloriously tinted with purple and scarlet. The purest vermilion and lake, brilliant and gem-like, shine forth almost to scintillation; and rays of azure and gold spread quite to the zenith, and lend reflected coloring to the ascending cumuli. The Gulf water is lighted up to exceeding beauty. Around the throne of the great orb all is moving, changing, dissolving, culminating in a scene of most exquisite brilliancy and beauty as the view closes behind the great curtain of the sea. Serene and beautiful is all this, and very enjoyable in this delightful climate. Then, at night—

"'Twas a lovely evening, fit to close
A lovely day, and brilliant in repose"—

Mars beams brilliantly from the east, and Canopus of the south is up in full splendor. The Southern Cross is just visible above the dark line of waters, while the Great Dipper lies half hidden by the northern horizon. Nearly overhead, and streaming from the west, are the curious phosphorescent pencils of the zodiacal light.

But how quickly, after this day of beauties, comes a change. The north wind has put forth its brief but earnest warning. The low banks of clouds that so lately played passively their part in the quiet scene now grow dark, and crowd the northern horizon; rapidly they lift, and the dark shadows and ripples on the water usher the howling blast. The Gulf; lately so placid, is lifted into white-caps, and a white belt of foam rises upon the borders of the reef where the sea rolls in tumultuously. This is the usual course of a "norther." In three days, without a drop of rain, and frequently with a clear sky, it is expended, and the steady trade-wind assumes its sway.

During these calm days, when the water is still, objects can be seen at great depth; and at such times every thing turns out for a sunning. The sea then shows forth its best. It is pleasant to float leisurely with the tide and lounge over the gunwale of the boat as she passes over the coral hills and groves. Myriads of jelly-fishes float or paddle with their iridescent oars; richly colored fishes dart away; and the Barracuda and flying-fish shoot out from near the bows. The great nurse-shark is frequently encountered in droves like hogs, and they are in such shallow water and so numerous that the boat nearly runs over them, stirring the mud from the bottom. They are eight or nine feet in length, but have very small mouths, and are consequently harmless, feeding on the shell-fish of the muddy shoals.

How different all this land, reef, and shoals is from our own hills and valleys. Unlike the rocky coast of the North with its sandy beaches, or the alluvial lands of other parts of the country. All this great reef, as it is called, and the islands or keys, have been piled up here in the deep Gulf by a great variety of sea creatures. Some of these sea creatures are flower-like animals that live in lime-tubes which are joined together in colonies, and form great bunches, and rock-like, boulder-like masses. And these masses of tubes are the skeletons or shells of the flower-shaped animals, which they are attached to just as a clam is attached to its shell. The beautiful white branches and leaflike forms, and feather and fan shaped objects, are the dried skeletons or shells of these little creatures that agree so well to build houses in blocks. They don't build as the bee builds its comb, for they are not insects; but they grow with their shells around them, as the little shellfish develop into big shells, from the soft eggs or spawn. You can't get them off their tubes without cutting them, or boiling them, or rotting them, as you would the soft parts of a shellfish.

The coral animals are very much more simple than the shell-fish, for they have not much more than a stomach and a few threads of nerves. They even increase by buds, like plants. These buds, soft and pulpy, attach themselves to any object they may touch, grow to their full size with the lime-tube around them; and then you have a single young coral, perfect in his one-room house, which he fully occupies. Soon other tubes begin to grow out, just as city people build houses against their neighbors'. So great blocks are formed, each house having one tenant. The coral people are very exclusive, and don't admit any other folk to live with them if they can help it; although they have their struggle to keep away stragglers as well as others. As they grow and multiply many forms are seen; many styles of architecture. Some are like trees, some like shrubs, and some are beautiful hemispheres that look like brain, with their curious winding openings. One is like a kidney, and another is strangely like the antlers of a stag. At one time, long, long ago, none of this coral reef was here. The great rock-like masses of coralAstreasa single house and tenant of which is not larger than my pencil, and not nearly as long, have grown upon the bottom of the sea, on some elevated, favorable spot, where the little, soft young corals first touched as they floated off from the parent stock; here, multiplying, spreading, until a great ledge-like, solid mass is formed.

These ledges of living coral then offer tempting bites to greedy fishes and worms, and snug retreat for many other marine creatures. The Parrot-fish, which has a bill exactly like a parrot, and is painted gaudily like them too, crushes some kinds with its bill to feed upon the meat. Great bristled wormsAphroditaceansthat look like monster hairy caterpillars, lie coiled upon the branches of the delicate kinds, and suck their tapering ends. Boring shellfish like the date-clam, and the various serpulae, penetrate all parts of these ledges. Holothurians—curious, cucumber like animals feed upon and crush them.

Now, do you see, it will surely result that these parts of coral that have had the meat sucked out will be brittle and will break easily, and crumble down into dead fragments; then, with the vast amount of fine coral that is thrown from the stomachs of the great worms and fishes that feed thereon, we have a collection of white mud and sand. Some parts of the ledge, and after a time the whole, is in this way covered. When this happens the little coral tenants die. Eggs of the coral are floating about, however, and ready to make fast to any dead, broken piece of coral or shell that may lie over this once living block. These grow, and in turn die and become buried. And so on does this great reef get piled up until it reaches the surface air. There they must stop, for they can't live out of water.

During the cooler part of the year, when the tides are not so low, the coral branches grow so near the surface that when the summer low tides come several inches are exposed and die. And as they are then brittle, and break easily when the sea beats over them, we have here another element in reef building.

In the wisdom of Nature the mangrove-tree puts forth curious root-like fruit, which is not only capable of floating unharmed in the salt sea, but will take root wherever it can find mud enough to hold to. This fruit looks so much like a cigar that you would at first think they were Cuba cheroots that had floated across the Gulf Stream from Havana. Numerous rootlets sprout from the larger end while the fruit is in the water, and this end being a little the heaviest the rootlets touch bottom where the water is only a few inches deep. In this way hundreds of these in favorable situations take root, and grow to be large, elegant, evergreen trees. Curious knees or flying buttresses are thrown out at different points, above and below water, and these strengthen and brace the young trees until the floating debris of the ocean accumulates in such quantities as to form a more solid foothold above the surface. One of the Tortugas islands has been made up in this way, and others have been formed above water by the action of the sea and winds, which force the mud and sand into ridges. Once fairly above water the sand gives footing for seeds of grass, and those of various shrubs and trees that birds may bring to them. The Keys of the Florida Reef have thus been built up through the agency of many kinds of sea creatures. Professor Agassiz tells us that nearly the whole of the main land of Florida has been made up in a similar manner.

But how difficult to convey an idea of the wonderful beauty and singularity of the scene beneath the wave. Spread over acres, miles of reef; in shoal water and deep, on hill-side and plain, in forest-like groups and garden-like beds, in choice single clusters, in circles, in hedges, in chevaux de frise. Domes like the round-topped mosque of the Orient; spongeforms that mock the Turkish minaret; Laplandish huts, and the Gothic minster; cups, vases, and the classic urns; antlers of deer, of moose, of elk; blossoms of rose, of jasmine, of daisy; clusters of pinks, lilacs, coxcombs, and amaranths; dandelions, golden-rods, anemones, and clovers; vines of michella and cypress; ferns, brakes, and mosses. All these forms come before you as you drift slowly with the tide, and look down as from a balloon upon this vast ocean garden. And they look so much like these forms, do the corals and sponges, sea anemones and sea-weeds; and this ocean garden looks so much as if it had been laid out in the "landscape style." The large round heads of meandrina look like artificial structures placed, for artistic effect, at certain points; while the more picturesque astreas are like "rock-work," around which grow delicate moss vines and richly-colored algae. You wonder at the strange similarity between the corals, sponges, and the familiar forms of the land gardens; but the forms, the coloring, the sculptured beauty of the Serpulte, Tubularias, Ser tularias, Actinarias, Alcyonarias, Gorgonias, and Acalephs, startle you with surprise.

In the white mud, among the green moss fronds, the weird-looking passion-flower is wonderfully well represented; carved and painted, in bass-relief, much of curious penciling is there; but lo! the flower instantly closes and disappears from sight; the shadow of the boat has driven to his hole one of the fairest forms of the "sea-anemone." And this creature, so flowerlike in its form and color, lives nearly buried in the sand, and spreads only its fair face to the sunbeams.

We have drifted over the reef with the tide, and now, three miles to the westward of the fort, we are just on the outer margin. In a moment more we will lose sight of the great branch or tree corals, which grow on the steep banks as low down as our eye can follow. And then we are near the deep Gulf Stream. I am afraid to guess how far down these steep banks Charley and the Fat One have been for specimens; but overboard they dived whenever any uncommon specimen appeared, and the water seemed fearfully deep, and they seemed fearfully long in coming up again. Many rare shells and curious . forms were found in this way that do not grow in shallower water.

The garrison flag is lowered, the bugle-notes of Retreat are in the air, and the sunset gun has just boomed forth its warning; so, as the evening breeze has sprung up, we will get under way and sail in.

"Unbrail y'r foresail there!"

"Ay, ay, Sir," says Busby.

"That's well; get y'r anchor aboard."

"All right, Sir."

"Unbrail the main-sail, and take the foresheets, then."

"Ay, ay, Sir."

"Ready?"

"Ready, Sir."

"Ease off the fore-sheet a trifle."

"Ease it is, Sir."

"Steady."

"Steady, Sir."

"Ready about!"

"Ready, Sir."

"Hard-a-lee, then!"

"All right, Sir."

And the Rosetta goes against the pleasant trade-wind that comes so steadily from the east and cools so pleasantly the hot air of these tropical islands.

Source:
Excerpt from: Holden, J.B., "The Dry Tortugas."
Harper's New Monthly Magazine, July 1868, Vol.37, No.218., pp. 264-267

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