Geoscience Reference
In-Depth Information
The salt and fresh waters of the gulf perform a kind of oceanic pas de deux. The fresher, lighter water from
the river moves on the surface toward the sea, while the heavier, saltier ocean water moves, at depth, toward
the river. These two masses are on a collision course and begin to mix just downriver from Quebec City, but
the major mixing occurs where the Saguenay River empties into the St. Lawrence. Between Quebec City and
Tadoussac, the water is brackish—a mixture of fresh and salt—and also turbid, since intense mixing brings the
sediments into the water column. This area is defined as the Upper Estuary, and the Lower Estuary extends
seaward from Tadoussac to Pointe-des-Montes on Quebec's North Shore.
Waterfowl and White Whales
Each spring and fall, cacophonous flocks of greater snow geese descend on the Upper Estuary. In the shadow
of the glacial-scoured granite mass of Cap Tourmente, the marshes along the North Shore of the St. Lawrence
are turned white as if by a premature snowfall by the massing of greater snow geese during their migration
from their breeding grounds in the Canadian Arctic to their wintering areas along the Mid-Atlantic coast. Dur-
ing the fall, the entire world population of the birds fatten on the rhizomes of American bulrush, which flour-
ishes in the vast expanses of tidal marshes between Quebec City and Montmagny. As many as 800,000 geese
gather at the Cap Tourmente National Wildlife Area alone. (The protected areas along the river have been crit-
ical to the revival of this species, whose numbers were reduced to three thousand at the turn of the century).
The birds begin arriving when the first frosts in the Arctic force them south. While foraging, the geese fol-
low the tide to take advantage of the softer sediment, using their strong bills to dig into the marsh muds. They
strip the tidal marshes bare of the bulrush before their departure in October. This feeding activity may help the
growth of wild rice, which in turn enhances the attractiveness of the marshes for other waterfowl, such as dab-
bling ducks. The Montmagny area is a traditional fall staging area for northern pintails, and Cap Tourmente at-
tracts pintails, green-winged teal, and American black ducks.
On the fat reserves acquired here, some snow geese fly the 900 kilometers (560 miles) nonstop to marsh-
lands along the eastern seaboard from New Jersey to South Carolina. They concentrate on coastal salt marshes,
where they feed on smooth cordgrass and salt marsh hay. The rapidly expanding population of snow geese has
caused “eat-outs” of the southern marshes, which have had a number of detrimental effects on coastal salt
marsh ecosystems, including increased erosion and decreased primary productivity. Grazed marshes in New
Jersey have also experienced a decline in the number of clapper rails as a result of damage to their nesting
sites. Other typical salt marsh invertebrates, such as salt marsh snail, ribbed mussel, and fiddler crab have also
declined, and black duck populations may have been affected as a result.
