St. Nicholas/Volume 40/Number 5/Nature and Science/Sponges

by Harry B. Bradford

A diver’s boat, of the Greek type, off the coast of Florida.

The diver is down and the life-line, air-hose, and two oars may be seen over the side of the boat, as well as the hinged ladder used by the diver to climb aboard. The boat is rowed slowly, and keeps just above the diver, whose position is shown by bubbles coming up from below.

The culture of sponges

Most of us know little of the nature of the sponge, and while we may delight in its use as a
A diver at work under water.
When he has filled his bag with sponges, he gives a signal on the life-line attached to his waist, and is drawn up to the surface. toilet article, we are not aware that it is practically indispensable in many of the arts. Science has offered substitutes for it made of rubber, but nature’s product still remains far superior to anything that man has thus far manufactured. The sponge, as we know it, is merely the fibrous skeleton which supported the soft gelatinous tissue of the living animal. It is usually fixed to certain spots of the ocean’s floor and absorbs its nourishment from the currents of water which continually pass through its porous structure; but no one so far seems to know exactly of what that nourishment consists.

Like some other animals, the sponge may have its body cut up into small pieces, and from each section a new sponge may develop. Science has taken advantage of this remarkable quality in artificially cultivating the sponge.

The sponge family has a wide distribution in the warm waters of various seas. In points of abundance and quality, the Mediterranean ranks first in its wealth of sponges, and, at present, is given credit for producing more than half the value of the world’s supply. Other sponge fisheries are located in the Caribbean Sea and the Mexican Gulf.

Before describing the methods of cultivating the sponge, it may be interesting to learn how they are taken from their native grounds.

The earliest method of gathering them was by wading. They were detached by the toes and kicked within reach of the hands, as the wader stood shoulder deep in the water. Sponges at a greater depth are now taken by long pole-hooks operated from a small boat, a water-glass being used to find them on the bottom. This is simply a pane of glass fixed in the bottom of an ordinary wooden bucket. It cannot be successfully used when the water is turbid, or of a greater depth than about fifty feet.

Diving is another interesting method of procuring sponges. The depth to which professional divers wearing the diving-dress, or submarine armor, as it is called, usually descend does not
A piece of sponge attached to a cement disk by a spindle.
This is ready for placing on the bottom in shallow sea-water. exceed 150 feet, although they sometimes stay down for two hours. Air is pumped down to them through the air-hose, and keeps their suits puffed out, the oversupply escaping from their rubber wristbands, and rising in bubbles to the surface. To change the air within the head-piece, or helmet, the diver presses his head back against a valve, which allows the air within the helmet to escape and fresh air to enter.
Six matured sponges.
These are attached to spindles upon a cement triangle, where they have grown from small pieces.

In the cases where the divers do not use the armor, they carry with them a large, flat stone to aid them in their descent, and a string attached to this is held in the hand of an attendant in the boat above. When the bottom is reached, the diver drops the stone, but clings to the rope, by which he signals if help is needed. These divers usually remain under water for not more than two minutes, although experts have stayed under for four and even for five minutes.

Sponges growing on a wire under water.
The stakes project from the surface of the water, so that the line may be readily located.

Biscayne Bay, Sugarloaf Key, Anclote Keys, and Key West, on the Florida coast, are the principal places in this country where experiments in sponge culture have been made. The various methods are as follows: “seed” sponges are cut into small pieces, and, after having been attached by wiring or spindle to circular or triangular cement blocks, are dropped or lowered (depending upon the depth) to rest on the ocean bottom, where they remain for a year or two, until they reach a size proper for commercial purposes. They are then taken by the hook,
A sheepswool sponge.
This is thirty-one months old, and was grown on a wire as in the illustration at the bottom of the preceding page. when new cuttings are attached, and the cement blocks let down again.

Another method was to string them on a wire held horizontal by stakes driven in the bottom. In doing this, however, various difficulties arose. The sponges became loose and rotated on the wire, enlarging the hole made through them, and the action of the salt water corroded and destroyed the wires, until, after many trials and experiments, a lead wire with a copper core was successfully used.

When the sponge cuttings are thus suspended freely in the water, growth takes place about equally in all directions; but when attached to one of the cement triangles or disks, the growth is most rapid in the horizontal plane. Experiments at Key West show that the cuttings two and one half inches in diameter increase in bulk from four to six times in six months.

The “seed” sponges must be transported to the culture grounds with considerable care, by packing them in tubs of wet seaweed kept at a temperature of seventy or eighty degrees. Some have been successfully packed in wet eel-grass and gulfweed. They must be kept moist and cool, and away from the sun’s rays and from fresh water, or they will not live. Even when growing on the culture farms, a heavy rainfall may so weaken the saltness of the water as to cause a high death-rate among the sponges affected by it. Shifting sands, entangling weeds, and storms are other happenings which make havoc with the sponge crop.

A sheepswool sponge, thirty-one months old, which was grown on a wire, is shown in one of the illustrations. This variety is unequaled for bathing purposes, and for use in the various arts. The larger forms are even used for gun-swabs in the army and the navy. They grow to be eighteen inches or more in diameter, are soft, of good shape, and readily absorb water. The color of the living sponge is black, becoming brownish at the base. The plan of the sponge culturist is to grow sponges in quantities large enough to be of commercial value, and that this may be done economically, they must be grown in water shallow enough to leave them easily accessible, without the aid of diving apparatus, which is expensive to maintain. Harry B. Bradford.