Chesapeake (118 page)

Any sharp dislocation of the upper and lower levels of the bay would have disastrous consequences, for over the millennia marine life had learned to accommodate to the conditions as they existed, and there were many creatures living in the upper layer of warm, light water who could not survive if the cold, heavy water of the bottom suddenly engulfed them.

There was a final division, this one between the western half of the bay and the eastern. The former was fed by five substantial rivers—Patuxent, Potomac, Rappahannock, York, James—some of which drained large inland areas reaching westward to the Blue Ridge Mountains. The huge flow of fresh water contributed by these rivers made the western half of the bay much less saline than the eastern, more silty, more filled with accidental non-marine vegetation, and in general more active.

The so-called rivers of the Eastern Shore did not deserve that name. They were not rivers in the customary sense: they drained no large upland areas; they had no great length; they had no fall; they did not collect fresh water from large drainage areas; they were tidal for most of their reach; and they were notably salty for much of their distance and brackish the rest. They were really tidal inlets
—estuaries
was the proper name—probing arms of the bay, which curled inland, creating flats and marshes.

Since they deposited only a fraction of the water produced by the western rivers, the eastern half of the bay had to be saltier, more torpid, more given to marshes, and much more productive of those small saltwater plants that sustained marine life. Also, another natural phenomenon contributed to the saltiness of the eastern half; the whirling motion of the earth applied a constant force that pushed the heavier water to the east, so that if a scientist drew isohalines—lines connecting all points west to east that had identical percentages of salt water—they would tilt conspicuously from southwest up to northeast. This meant that a line drawn due west from Devon Island, with its fifteen parts of salt per thousand, would find water much less salty in the middle of the bay and notably less so on the western shore. In fact, to find water on the western shore with a salinity equal to Devon’s, one would have to drop twenty-five miles south.

Watermen skilled in reading the variations of the Chesapeake kept in mind that there were really three distinct segments: the moderately deep riverine western part; the very deep central channel followed by the steamers, which represented the course of the prehistoric and now
drowned Susquehanna; and the exciting estuaries of the eastern portion, where plankton and menhaden and crabs and oysters abounded.

An Episcopal clergyman in Patamoke with time on his hands and a fine Princeton education behind him, carried this analysis to its logical conclusion:

What happened in 1886 at Chesapeake Bay Number 4-8-9? The magnitude of this storm broke all existing records not by trivial percentages but by huge multipliers. For example, the greatest previous discharge of fresh water at the mouth of the Susquehanna had been something like 400,000 cubic feet per second, and that represented a devastating flood. Now the disgorgement was more than three times as great, an unheard of 1,210,000. This produced a volume of non-salt water so prodigious that it shifted the isohalines seventy-two miles southward, which meant that the waters about Devon Island had become practically salt-free.

When the storm broke, there existed on a small subterranean shelf at the western edge of Devon Island–point 4-8-9 by the clergyman’s calculation—a congregation of oysters which had fastened themselves securely to the solid bottom. Here some of the largest and tastiest oysters of the bay had produced their generations, while the minute spat drifted back and forth with the slow currents until they fastened to the bottom to develop the shells in which they would grow during the years of their existence.

Along this shelf, well known to watermen from Patamoke but kept by them as a secret, oysters had thrived during all the generations watermen had tonged the bay; no matter how many bushels of large oysters were lifted from this location, others replaced them. ‘This was the shelf that could be depended upon.

In its original stages the flood from the Susquehanna did not affect these oysters. True, the salinity of all the water dropped, but at the depth at which they lived the loss did not, in these first days, imperil them. But
there was another aspect of the flood which did. The Susquehanna, as it swept down from New York, picked up an astonishing burden of fine silt; for example, a house along the riverbank in Harrisburg might be inundated for only seven hours, but when the owners returned they would find in their second-floor bedrooms six inches of silt. How could it possibly have got there? Well, each cubic centimeter of seeping brown water carried its burden of almost invisible dust lifted from the farms of New York and Pennsylvania, and it was this dust, suspended in water, that was left behind.

The silt that fell in the bedroom of a butcher in Harrisburg could, when it dried, be swept away, but the silt which fell on a bed of oysters could not.

Down it came, silently, insidiously and very slowly. In four days more silt fell than in the previous sixty years. The entire Choptank as far east as Patamoke was chocolate-colored from the turbulent mud, but as soon as the waters began to calm themselves, their burden of silt was released and it fell persistently and inescapably onto the oysters.

At first it was no more than a film such as the propellers of the evening ferry might have deposited on any night. Such an amount caused no problem and might even bring with it plankton to feed the oysters. But this thin film was followed by a perceptible thickness, and then by more, until the oysters became agitated within their heavy shells. The spat, of course, were long since strangled. A whole oncoming generation of oysters had been suffocated.

Still the fine silt drifted down, an interminable rain of desolation. The bottom of the Choptank was covered with the gray-brown deposit; whole grains were so minute that the resulting mud seemed more like cement, except that it did not harden; it merely smothered everything on which it fell, pressing down with fingers so delicate, its weight could not be felt until the moment it had occupied every space with a subtle force more terrible than a tower of stone.

The oysters could have withstood a similar intrusion of sand; then the particles would have been so coarse that water could continue to circulate and plankton be obtained. Submersion of even a month was tolerable, for in time the sand would wash away, leaving the shellfish no worse for their experience. But the flood-swept silt was another matter, and on the tenth day after the flood, when the brown waters bore their heaviest burden of mud, even the mature oysters on the Devon shelf began to die. No lively water was reaching them, no plankton. They were entombed in a dreadful cascade of silt and they could not propel themselves either to a new location or to a new level. Secured to their shelf, they had to rely on passing tides that would wash the silt away. But none came.

On the twelfth day the waters of the Chesapeake reached their maximum muddiness; silt from midland Pennsylvania was coming down now,
in a final burst of destruction, and when it reached the relatively calm waters of the Choptank, it broke loose from its carrying waters and filtered slowly down to the bed of the river. This was the final blow. The oysters were already submerged under two inches of silt; now three more piled on, and one by one the infinitely rich beds of Devon Island were covered by an impenetrable mud. The oysters perished in their shells.

In time, say a year and a half, the currents of the Choptank would eat away the mud and once more reveal the shelf upon which untold generations of new oysters would flourish. The shells of the dead oysters would be there, gnarled and craggy and inviting to the young spat that would be looking for a ledge to grab hold of. The spat would find a home; the nourishing plankton would drift by; the oyster beds of Devon Island would exist once more, but for the meantime they were obliterated in the silt of the great storm.

Another resident of the Chesapeake was also intensely affected by the hurricane of 1886, but he was better able to cope with the disaster, for he could move, and by taking precautions, adjust to altered circumstances. He was Jimmy, the time-honored Chesapeake name for the male blue crab, that delicious crustacean upon which so much of the wealth of the bay depended.

While the storm still lay off Norfolk, gathering speed and water, Jimmy, resting in the grassy waters at the edge of Turlock Marsh, perceived that a radical change in the atmosphere was about to occur. And it would probably arrive at the worst possible moment for him. How could he know these two facts? He was exceedingly sensitive to changes in atmospheric pressure or to any other factors which affected the waters of the bay. If a storm of unusual force was developing, he would be made aware by the sharp drop in barometric pressure and would prepare to take those protective measures which had rescued him in the past. Also, he knew intuitively when he must climb painfully out of his old shell, which was made of inert matter that could not grow in size as he grew. He had to discard it and prepare himself for the construction of a new shell better fitted to his increased body size. The time for such a moult was at hand.

When the storm broke, and no great body of water fell on the Choptank, Jimmy felt no signals that a crisis was at hand, so he prepared to shed his old shell, an intricate process which might consume as long as four hours of painful wrestling and contortion. But before the moult could begin, he became aware of a frightening change in the bay. The water level was rising. The salinity was diminishing. And when these two phenomena continued, and indeed accelerated, he became uncomfortable.

During any moult, which might take place three or four times a year as he increased in size, he preferred some secure place like the Turlock

Marsh, but if it was going to be flooded with fresh water, it could prove a deathtrap rather than a refuge, so he began swimming strongly out toward the deep center of the bay.
A mature crab like Jimmy could swim at a speed of nearly a mile an hour, so he felt safe, but as he cleared Devon Island and was hit by the rush of saltless water, he felt driven to swim with frenetic energy to protect himself. He would not drop dead in the first flush of fresh water, and he could adjust to surprising variations in salinity for brief periods; but to exist in the way for which his body had been constructed, he needed water with a proper salt content.

But moving into the deeper water meant that he would lose the protection of the marsh for his critical moulting. He would have to go through this complex maneuvering out in the bay, where he would be largely defenseless. But he had no other option.

The silt posed no insurmountable problem. It obscured his vision, to be sure, but it did not settle on him or pin him to the bottom, as it did the oysters. He could flip his many legs and swim clear, so that he was not yet in danger at this stage of the flood, but he did sense that he had to swim down toward the ocean to find the salinity necessary to his survival.

These matters assumed little importance in view of the crucial one at hand. Swimming easily to the bottom of the bay, he found a sandy area, a place he would never have considered for a moult in normal times, and there began his gyrations. First he had to break the seal along the edge of his present shell, and he did this by contracting and expanding his body, forcing water through his system and building up a considerable hydraulic pressure that slowly forced the shell apart, not conspicuously, but far enough for the difficult part of the moult to proceed.

Now he began the slow and almost agonizing business of withdrawing his boneless legs from their protective coverings and manipulating them so that they protruded from the slight opening. With wrenching movements he dislodged the main portion of his body, thrusting it toward the opening, which now widened under pressure from the legs. He had no skeleton, of course, so that he could contort and compress his body into whatever shape was most effective, but he did continue to generate hydraulic pressures through various parts of his body so that the shell was forced apart.

Three hours and twenty minutes after he started this bizarre procedure, he swam free of the old shell and was now adrift in the deep waters of the bay, totally without protection. He had no bony structure in any part of his body, no covering thicker than the sheerest tissue paper, no capacity for self-defense except a much-slowed ability to swim. Any fish that chanced to come his way could gobble him at a gulp; if he had been in shallower water, any bird could have taken him. In these fateful hours all he could do was hide.

And yet, even at his most defenseless moment his new armor was beginning to form. Eighty minutes after the moult he would have a paper-thin covering. After three hours he would have the beginning of a solid shell. And in five hours he would be a hard-shelled crab once more, and would remain that way until his next moult.

But as he waited deep in the bay for his new life, the results of the storm continued to make themselves felt, and now the water was so lacking in salt that he felt he must move south. He swam forcefully and with undiverted purpose, keeping to the eastern edge of the bay where the nutritive grasses produced the best plankton, and after a day he sensed the balance of the water to be more nearly normal.