Geoscience Reference
In-Depth Information
But perhaps the most impressive gathering of waterfowl occurs off Cape May Point in February and March,
when tens of thousands of scoters—all three species: surf, black, and white-winged—gather to feed on the rich
invertebrate offerings in these offshore waters. The flocks, whose whistling enlivens the spring soundscape
around Delaware Bay, are mostly males and include a very high percentage of the black and surf scoter popu-
lation of the Atlantic Ocean. They are often joined by large flocks of long-tailed, or old-squaw, ducks. Gener-
ally speaking, Delaware Bay and the waters surrounding the mouth are recognized as having the largest winter
waterfowl populations in the Mid-Atlantic region. These same estuarine-enriched waters are thought to be the
main wintering area for common loons, which feed on small flounders, sculpins, and crabs. They are joined by
red-throated loons, which also stage there in spring, before moving northward.
Where Freshwaters and Salt Waters Mix
Captain John Smith was the first European to record the riches of Chesapeake Bay, in the journal of his 1608
voyage. Returning from a trip up the Potomac, where he had investigated a supposed silver mine that “proved
of no value,” he marveled at the natural capital of the Bay:
. . . a few Bevers, Otters, Beares, Martins and minkes we found, and in divers places that aboundance of
fish, lying so thicke with their heads above the water, as for want of nets (our barge driving amongst
them) we attempted to catch them with a frying pan; but we found it a bad instrument to catch fish with:
neither better fish, more plenty, nor more variety for smal[l] fish, had any of us ever seene in any place so
swimming in the water, but they are not to be caught with frying pans . . .
Although Chesapeake's natural capital has been much depleted in the last four hundred years, the bay is still
renowned for its historical productivity and present potential.
Chesapeake Bay is the largest estuary in the United States, stretching for 333 kilometers (200 miles) from
Havre de Grace, Maryland, to Norfolk, Virginia, varying in width from a mere 5.7 kilometers (3.5 miles) near
Aberdeen, Maryland, to 58.3 kilometers (36 miles) at its widest point, near the mouth of the Potomac River.
More impressive than the dimensions of the bay itself is the size of the drainage basin, at 166,512 square kilo-
meters (64,000 square miles). More than fifty rivers and thousands of streams fan out to form the bay's water-
shed, which includes parts of New York, Pennsylvania, West Virginia, Delaware, Maryland, and Virginia.
Arising in the Appalachian Mountains, farther west, these freshwaters tumble from the fall line that forms the
boundary between the Piedmont Plateau and the Atlantic Coastal Plain. The three main tributaries of the bay
are the Susquehanna, Potomac, and James Rivers, with the great Susquehanna accounting for fully half of the
freshwater input Altogether, the three rivers account for 70 to 80 percent of the bay's freshwater budget. They
carry with them sediments and nutrients which, in part, are responsible for the historical productivity of the
bay. Increasingly, they also carry a cocktail of contaminants from the industrialized and highly urbanized areas
along their extensive reaches, where an estimated 16 million people work and live.
The Susquehanna has been called the mother river of the bay. During the last glaciation, the ancestral
Susquehanna carved a valley through the coastal plain and onto the continental shelf, which, with so much wa-
ter tied up in the glaciers, was exposed at the time. As the glaciers receded and began to give up their waters,
the sea level rose and began rapidly drowning the river valleys. Seawater reached the area of Baltimore by
nine thousand years ago and by three thousand years ago, the Chesapeake as we know it today had been cre-
ated.
In addition to its impressive size—the most notable notch in the eastern seaboard of the United States—and
the even more impressive area of its drainage basin, a three-dimensional view of the bay reveals another distin-
guishing if surprising feature: it is very shallow, averaging only 7 meters (23 feet) deep. This has profound im-
plications for its legendary productivity. Estuaries are normally five times as productive as the open ocean, but
