Barre de Portneuf (QC083)
Altitude 0 - 10m
The Barre de Portneuf is a sandbar extending southward, from the mouth of the Portneuf River, into the lower St. Lawrence River, Quebec. The sandbar originates from the southern side of the mouth of the Portneuf River. It extends southward and upstream into the St. Lawrence River, for a distance of 4.5 kilometres and a maximum width of 250 metres. A bay is created between the mainland and the sandbar which is inundated at high tide, and is mixture of one-third Spartina salt marsh and two-thirds mudflats at low tide. The middle portion of the sandbar is colonized by xeric plant species associated with sandy areas (mostly sea lyme-grass) while small stands of conifers and alders are established on higher parts.
This area is probably one of the most important fall migratory stopovers for shorebirds in the St. Lawrence River estuary. The sandbar is, accordingly, one of the favorite spots for birdwatchers interested in shorebirds in Quebec. Least Sandpipers peak during August, with up to 750 birds being seen daily.
Over 25 shorebird species have been seen at Barre de Portneuf. The highest one-day total of all shorebirds was 8,832 on August 21, 1995. If ‘bird days' are considered – an estimate of the season total, that assumes daily turnover – then 182,501 shorebird bird days were calculated for the 1995 season.
The highest one-day total of any one species was 7,000 Semipalmated Sandpipers on August 22 and 23, 1994 (116,925 bird days, 1995). White-rumped Sandpipers also feed at the site in large numbers, with up to 1,000 birds present daily (> 500 regularly) during their long peak period, which lasts from early August to mid-September. Black-bellied Plovers pass through here from early summer into October, with their peak numbers occurring in the second half of August. Up to 650 birds have been recorded, and between 500 and 600 per day seen regularly. Additional common migrants are Semipalmated Plover, Ruddy Turnstone, Red Knot, Greater and Lesser Yellowlegs, and Sanderling. Uncommon migrants include American Golden-Plover, Pectoral, Baird's and Least Sandpipers, Whimbrel, Hudsonian Godwit, Short-billed Dowitcher and Dunlin. Shorebirds that occur here rarely include Marbled Godwit, Western Sandpiper and Buff-breasted Sandpiper.
Large numbers of gulls and terns congregate on the sandbar, for both breeding and roosting purposes. The Portneuf sandbar, along with another sandbar located near Pointe-Lebel, are the only two sites where Parasitic Jaegers commonly come to shore, often to feed on shorebirds.
Off-road vehicles are the principal ongoing threat to the birds and vegetation of this site. Access to the sandbar is possible by foot, off-road vehicle or small boat. On a larger scale, hydro-electrical development agencies actually promote the diversion of one fifth of the discharge of the Portneuf River. Such a major diversion is likely to affect sand deposition and retention on the sandbar. So far, no conservation measures have been taken. However, some people from the Ste-Anne-de-Portneuf village are trying to promote the site as being an important recreational area for birdwatchers.
The landscape of the area is typified by salt marshes, intertidal rocky shore, mudflats, river's estuaries and long sandy beaches. The mixing of the cold and well-oxygenated waters with the warmer waters of the St. Lawrence favors an unusual marine biodiversity. Several marine species are commercially exploited, such as the common whelk, the soft-shell clam, the green sea urchins, the Stimpson's surf clams, the snow crab and the Atlantic herring. Moreover, the harvest of soft-shell clam at low tide is a popular recreational activity throughout the region of Lower North Shore. The north shore of the estuary is also hosting a variety of pelagic species occupying an important role in the food chain, such as the capelin and the rainbow smelt are also targeted by the sport fishermen.
The fish habitat is affected by coastal erosion, residential development, harnessing of rivers and the creation of resorts. In addition, the presence of industries discharging pollutants in the system does impacts the water quality. The Atlantic salmon is sensible to aluminum contamination through bioaccumulation of the residues present in the system.
Major species present:
Green sea urchin
Stimpson's surf clam
The salinity of the St. Lawrence water has a strong influence on the flora of the coastal habitats. Salt marshes are dominated by saltmeadow cordgrass, tall cordgrass, red fescue and chaffy paleacea. Present in a variable proportion, a variety of plants typical of estuarine environments: sea pea, Scotch lovage, American searocket, sea milkwort, etc. In areas submerged where substrate is thin, and water velocity is small, eelgrass grows. Eelgrass beds are home to an amazing biodiversity: shellfish, crustacean, fish, etc. which attract many predators. Several fish-eating birds such as the great blue heron come to take a meal. The Brant goose is closely linked with this habitat since the underground parts of the eelgrass are at the basis of its diet.
Potential or Ongoing Threats
Habitat loss, whether caused by human interventions (wetland drainage, road construction, urban spread, etc.) or through natural phenomena (coastal erosion) severely impact the flora. Similarly, water pollution and risks of oil spills are issues of special concern for the flora and fauna of these areas.
Major species present :
Sea pea / Beach pea