STATE OF THE GREAT LAKES 2005
WHAT ARE THE MAJOR PRESSURES IMPACTING THE ST. LAWRENCE RIVER?
Low and stabilized water levels, non-native invasive species, declining fish stocks, contaminants, and restricted
use of beaches are among the major pressures impacting the St. Lawrence River.
Pressures
Low and stabilized water levels
The construction of the seaway and dams in the St.
Lawrence River considerably modified the river's
hydrodynamics and resulted in the loss and
alteration of natural habitats. As an example, in the
Boucherville Islands, near Montreal, low-lying
marshes have been transformed into higher and
drier marshes, a phenomenon due in part to the
dredging of the shipping channel and exacerbated
by low water levels. An increase in the frequency of
low water levels could influence fish abundance,
diversity, and health significantly. Low water levels
could also have harmful repercussions on diversity
of wetlands, which are important habitats for birds,
fish, amphibians, reptiles, molluscs, and many small
mammals.
Non-native invasive species
The St. Lawrence River is the primary navigational
access route for trade and commerce in the Great
Lakes basin. Not surprisingly, ballast water
discharge from ships is the largest single source of
entry for non-native aquatic invasive species .
Although not all invasive species or their ecological
and economic impacts are yet known, the zebra
Hydrographic divisions of the St. Lawrence River. Source: Environment Canada.
mussel alone is estimated to have caused billions of
dollars of damage in North America since its
introduction. Dense beds of zebra mussels also
hinder the establishment and growth of naturally
occurring vegetation, and may threaten local
invertebrate, bird, and fish populations. The invasive
Chinese mitten crab has been identified recently near
Quebec City.
Non-native invasive plant species comprise an
estimated 43 percent of wetland plant cover from
Lake Saint-Louis to Contrecoeur. A European variety
of the common reed is now expanding in some areas
including the Boucherville Islands. Other invasive
plant species in the St. Lawrence River area include
purple loosestrife, flowering rush, reed canary grass,
and water chestnut.
Declining fish stocks
Structural changes to the St. Lawrence River and
contaminants such as PCBs, mercury, and DDE,
contribute to the degradation of fish and wildlife
habitat. The decline of yellow perch and lake
sturgeon stocks in Lake Saint-Pierre is caused by
habitat degradation and overfishing. Construction of
dams and overfishing similarly
have resulted in the decline of
fish populations in Lake Saint-
Francis.
High levels of contaminants in
fish tissue
Contaminants are introduced
into the St. Lawrence River
through municipal, industrial,
and agricultural point sources
and through atmospheric
deposition. These contaminants
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ST. LAWRENCE RIVER PRESSURES
increasingly accumulate in organisms higher in the
chain, such as top predator fish. New York state, the
provinces of Ontario and Quebec, First Nations, and
tribal councils have developed fish contaminant
monitoring programs and issue fish consumption
advice to their residents. This advice ranges from
recommendations limiting consumption of specific
sizes of fish, fish species, and/or fish from particular
water bodies to unrestricted consumption of fish
from various locations in the St. Lawrence River.
Restricted recreational use of beaches
Although most communities along the St. Lawrence
River now treat their wastewater, lack of disinfection
is responsible for high coliform counts and results in
restriction of recreational water use in some regions
of the river.
Purple loosestrife (left). Photo: C. Savage, St. Lawrence
Centre. Zebra mussel (right). Photo: B. Cusson and D.
Labonte, St. Lawrence Centre.
Current Actions
The IJC-sponsored Lake Ontario - St. Lawrence River
Study will propose management options for water
level regulation that consider environmental
impacts. Environmental indicators have been
developed to evaluate impacts related to different
water level regulation plans. These indicators have
also been integrated into a St. Lawrence River
hydrodynamic model.
Cleanup of contaminated sediments is an ongoing
process for all contaminated aquatic areas, including
Dock 103 (Port of Montreal), Saint-Louis River, and
Sandy Beach (Port of Gaspe). The federal and
provincial governments of Canada, in partnership
with industry and NGOs, are involved in several
habitat restoration, conservation, and monitoring
projects, as part of the ZIP (Zone d'intervention
prioritaire) program, the Canadian Wildlife Service
supporting local actions, and ecosystem monitoring
through the State of St. Lawrence River program.
Canada and Quebec are partners in the St. Lawrence
Action Plan, which aims to eliminate chemical
pollution by major manufacturing plants. A recent
initiative under the plan, the Sustainable Navigation
Strategy for the St. Lawrence River, contributes to the
development of navigation while respecting the
environmental conditions of the St. Lawrence River.
Studies have also been undertaken to determine the
impacts of urban wastewater on river biodiversity.
The Canadian Framework for Invasive Species will
provide guidance in managing the urgent threat of
invasive species.
Needed Actions
Improved water quality and sediment quality are
needed to maintain ecosystem health and ensure
continued use of the St. Lawrence River ecosystem for
recreational use. Assessment of coastal and island
erosion is needed to protect the physical integrity of
the river banks. The spread of invasive plant species
such as common reed, water chestnut (now present in
the Richelieu River Basin), and the Chinese mitten
crab requires prompt attention.
To Learn More
For further information related to the state of the St.
Lawrence River, refer to the State of the Great Lakes
2005 report which, along with other Great Lakes
references, can be accessed at
www.epa.gov/glnpo/solec. To learn more about the
St. Lawrence River monitoring program and to access
the St. Lawrence Centre's Great Lakes-St. Lawrence
fact sheets, visit www.slv2000.qc.ca and
www.qc.ec.gc.ca/csl.
02/06
EPA905-F-06-913
IISG-06-06
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