Bay of Fundy Tides, Mudflats and Estuaries
Twice daily, one hundred billion tons of water from the Atlantic Ocean swirls its way up the shores of the Bay of Fundy. This water volume is estimated to nearly equal the 24-hour flow of all the rivers in the world.
The Petitcodiac River and the Shepody Bay estuary are important tidal systems influenced by the phenomenal Bay of Fundy tides. The tides reach upwards of 9 m in height on the Petitcodiac River and some 14 m in the Shepody Bay area (Hopewell Rocks), uncovering kilometres of mudflats at low tide, and nourishing some of the world’s greatest estuaries. On the Atlantic coast, estuaries are among the most important coastal features, both ecologically and with respect to human settlement and use.
Estuaries rank with tropical rainforests and coral reefs as the world’s most productive ecosystems, more productive than both the rivers and the ocean that influence them from either side. Strong tides reaching speeds of 13 km/hour and carrying huge volumes of water and suspended sediment flow up the Petitcodiac River twice a day, depositing sediment particles on the banks as the tide rises and only returning them into suspension as the tide recedes or as rain events occur.
The combination of these features makes the natural concentration of suspended sediment in the river among the highest in North America and gives the Petitcodiac River its nickname ‘The Chocolate River’. The underlying rock of the Petitcodiac River system, made up of sandstone, is the possible source of high concentrations of suspended sediment.
The Petitcodiac River Tidal Bore
The Petitcodiac River’s claim to fame is its tidal bore, forming twice a day as the tides from the Bay of Fundy push upriver towards Moncton. A tidal bore occurs in areas of the world where tidal amplitudes are strong, as is the case with the Bay of Fundy region. The phenomenon is created and influenced by a number of factors including river slope, downstream flow, river basin morphometry, moon phases, seasons and winds.
The accompanying wave or vertical front moves upriver on the incoming tide, channelling itself into a narrower body of water such as the Petitcodiac River. Depending on the amplitude of the phenomenon, the wave in the Petitcodiac River varies today from a few cm in height to as much as 75 cm (formerly as high as 2 m), and at speeds ranging from a few to 13 km/hour.
For more info, visit our section on the Petitcodiac Tidal Bore.
Located on Shepody Bay, the Hopewell Rocks are New Brunswick’s best known and one of Atlantic Canada’s most impressive natural attraction. At low tide, visitors walk the ocean floor surrounded by four-story-high flowerpot sea stacks, gouged out of the cliffs by the force of the Fundy tides. As the 14-meter tides return, these magnificent sandstone columns turn into tiny islands, observed from the nearby cliffs of the park or up close from a sea kayak.
The Sandpipers of Fundy
Every summer the upper Bay of Fundy plays host to massive flocks of migrating shorebirds. From late July to early August, the peak of the fall migration, up to 2 million shorebirds converge on Fundy’s nutrient-rich mudflats. Two of the most important sites are located at Johnson’s Mills and at Mary’s Point, on Shepody Bay.
The shorebird flocks are comprised of many species including the Semipalmated Sandpiper, 95% of whose world population depends on the Bay of Fundy mudflats for their survival. From their breeding grounds in Canada’s Low Arctic, the shorebirds fly non-stop to the Bay of Fundy. Individual sandpipers remain in the Bay of Fundy staging area for 10 to 20 days, doubling their weight to about 40 grams.
When the arrival of a cold front brings strong tailwinds, the sandpipers orient themselves south-southeast in huge flocks, finally taking wing when high tide coincides with the end of the day. Their flight pattern takes them well out to sea over the North Atlantic where they catch the trade winds that carry them to landfall on the northern coast of South America : 4,000 km in two to four days. The majority winter in Suriname, foraging on expansive mudflats, and roosting on beaches, in rice fields, and in mangrove swamps.
Fundy’s Mud Shrimp
The tidal flats left by the receding waters in Shepody Bay and on the Petitcodiac River are the habitat of Corophium volutator, the mud shrimp. About 5 mm long, the shrimp feed on diatoms and detritus churned up by the tides. As the tide goes out, the shrimp scurry along the surface of the mud, seeking mating opportunities and leaving themselves vulnerable to foraging birds.
In North America, these mud shrimp occur only in the Bay of Fundy and the Gulf of Maine. The mud contains exactly the right combination of coarse sand and fine silt and clay particles to allow the shrimp to excavate burrows. Under the right conditions, a square metre of mud may contain as many as 60,000 shrimp; the average is 10,000 20,000. Because these shrimp are rich in energy and abundant, they are the prey most sought by sandpipers. Within a short amount of time, the birds can build up the fat reserves necessary to fuel the exhausting flight to their wintering grounds in South America.
International Habitat Sanctuaries
In 1971, the international community adopted the Ramsar Convention (Convention on the Conservation of Wetlands of International Importance), enabling wetlands of international importance to wildlife to be recognized on a global level. Canada signed this convention in 1981. Mary’s Point in Shepody Bay was designated as a Ramsar Site in 1982, whilst Shepody Bay and the Minas Basin area were added to this designation in 1987. The designated site in Shepody Bay includes 13,400 ha of intertidal area.
The Western Hemispheric Shorebird Reserve Network is similar in nature to the Ramsar Convention but applies to the recognition of shorebird areas specifically. In 1987, Mary’s Point and Shepody Bay were designated as the first Western Hemisphere Shorebird Reserve Network in Canada. The next year, the southern portion of Minas Basin, in Nova Scotia, was added to this reserve.
The Fundy reserve (Shepody Bay and Minas Bassin) is the most important shorebird sanctuary in Atlantic Canada. To gain status as a hemispheric reserve, the site has to host at least 500,000 shorebirds or 30% of the flyaway population annually. Mary’s Point is part of the Shepody National Wildlife Area, which is owned and administered by the Canadian Wildlife Service.
The American Shad
In the l970′s and 1980′s, research emerged about the phenomenal richness in nutrients of the inner Bay of Fundy, especially Shepody Bay, and its direct effect on the migrating patterns of the entire American shad fish population. Dr. Mike Dadswell, a scientist from Acadia University, tagged American shad along the Atlantic coast.
He discovered that their summer migrating patterns brought the shad from the tip of the Florida peninsula to the Gulf of St-Laurence to Shepody Bay, in order to live off some of the world’s richest feeding grounds. The Petitcodiac River and its tributaries significantly contribute to the estuarine nutrient supply of this waterway.
The Petitcodiac River Valley was formed during the Mississippi era over 250 million years ago. A number of eruptions occurring during the last glacial period are believed to have had spectacular consequences on the topography of the region. This is attested by the extreme variety of mineral deposits found in the southeastern region of New Brunswick known as Albert County, on the western shore of the Petitcodiac River.In 1849, the famous scientist Abraham Gesner, inventor of kerosene, discovered a bituminous mineral named Albertite in Albert County. During the course of a 30-year period, over 200,000 tonnes of Albertite were shipped to Boston. Some 8 km from these Albert mines also lay a deposit rich in gypsum. From the old factory, once situated on the banks of the Petitcodiac River in Hillsborough, ships exported cargoes filled with gypsum extracted from these mines to the four corners of the world.
The Petitcodiac River Mastodon
In 1937, workers discovered the skeleton of an almost perfectly preserved mastodon (prehistoric elephant) near Hillsborough on the Petitcodiac River. The skeleton, believed to be over 37,000 years old, was transported to and has since been displayed at the New Brunswick Museum situated in Saint John.