Geoscience Reference
In-Depth Information
Using these criteria, the Northwest Atlantic can be divided into five ecoregions. The Mid-Atlantic Bight,
between Cape Hatteras and the south shore of Cape Cod, is a marine region guarded by a bastion of barrier is-
lands and penetrated by large estuaries such as the Chesapeake and Delaware Bays. The Gulf of Maine and
Bay of Fundy together form a single oceanographic unit that stretches north from Cape Cod along the low,
rocky, irregular coast of Maine to the expansive salt marshes and mudflats at the head of the Bay of Fundy.
The Scotian Shelf lies off the Atlantic coast of Nova Scotia, where the long reaches of the ocean curls ashore
onto beaches of white sand. Sometimes considered together with the Grand Banks of Newfoundland, this area
of the continental shelf is described separately on pages 20 and 21. At the heart of North Atlantic coast lies the
Gulf of St. Lawrence, a sea within a sea with a shoreline of great topographical contrasts. The North Shore of
the gulf presents an “ironbound” aspect of Canadian Shield rocks—a place reviled by its first European ex-
plorer, Jacques Cartier, as “the land God gave to Cain”— whereas the southern portion is carved from softer
sandstone, creating a welcoming shoreline of wide beaches, barrier islands, coastal dunes, and spits. And fi-
nally, in the far north, we come to the dramatic headlands and cliffs of Newfoundland—“the Rock” to its
proud inhabitants—and to the forbidding and majestic coastline of Labrador and its iceberg-studded sea. Off-
shore are the famous Grand Banks, once the greatest cod-producing region on the planet.
Given its size and complexity, it is hardly surprising that the Atlantic is a region of great biological diversity.
Offshore, productivity peaks on the shallow fishing banks, where life-giving light penetrates the water column
and nutrients are near the surface. The combination of light and nutrients fuels the growth of phytoplankton,
the single-celled plants that are the foundation of the marine food web. In turn, the phytoplankton feed the zo-
oplankton, the animal constituent of marine plankton, which include small, shrimplike crustaceans and fish lar-
vae. At the edge of the continental shelf, where waters plunge into the abyssal depths, oceanic fronts concen-
trate an abundance of zooplankton, which in turn attracts fishes, seabirds, and cetaceans. Inshore, waterfowl
and shorebirds exploit the mosaic of mudflats, salt marshes, and rocky shores for their riches. The many is-
lands and towering cliffs that guard the deeply indented northern coastline provide safe nesting grounds for
seabird nations, and the barrier islands and lagoons in the south harbor breeding and overwintering populations
of shorebirds, waterfowl, and waders. Anad-romous species such as Atlantic salmon, alewives, smelt, and
American shad run up its rivers, great and small, to spawn, connecting the sea to the hinterland behind the
coast.
Located roughly midway between the equator and the North Pole, the coastline of Atlantic Canada in partic-
ular serves as a way station for many migratory birds: neotropical land birds making their way to their boreal
forest breeding grounds in spring and on their return in late summer, shorebirds migrating between their Arctic
nesting grounds and the Southern Hemisphere, southern seabirds escaping the austral winter, and waterfowl
moving north and south with the changing seasons in search of open water and food.
The waters and shoreline habitats of the northwest Atlantic are critical to the survival of a number of spe-
cies. Delaware Bay is a vital staging area for the rufa species of red knots, which fly from Patagonia in spring
to banquet on the eggs laid by horseshoe crabs that come ashore around the full moon in May, in a wondrous
example of the alacrity and fecundity of nature. The outer Bay of Fundy is a critical nursery area for the
world's most endangered great whale, the North Atlantic right whale—perhaps only saved from the rapacious
whalers of the 19th century by the bay's frequent fogs and treacherous tide-rips. At the other end of the bay,
vast mudflats are the feeding grounds for three-quarters of the world population of semipalmated sandpipers
before they embark on a nonstop three-day journey over open water to their South American wintering
grounds. The estuary of the great St. Lawrence River, coursing out of the interior of the continent, supports the
white-winged migration of greater snow geese and the most southerly population of the endangered white
whale, the beluga.
But few places, if any, can match the bounteous waters of Newfoundland and Labrador, once home to the
greatest feedstock of fish—the Atlantic cod— in the history of human civilization. And despite the modern-
