STATE OF THE GREAT LAKES 2005
WHAT ARE THE CURRENT PRESSURES IMPACTING LAKE ONTARIO?
The current pressures impacting Lake Ontario include non-native invasive species, contamination, lake level
regulation, habitat alteration, aquatic food web changes, and urbanization.
Pressures
Non-native invasive species
Zebra and quagga mussels have irreversibly
modified the physical, chemical, and biological
integrity of Lake Ontario. The filtering activity of the
mussels has reduced the amount of food available to
other organisms, causing populations of native
benthic organisms to decline and creating a ripple
effect that has impacted the health of the fishery.
These mussel colonies encrust many manmade
features of the lake, as well as clump over soft
substrates, altering the habitat for other organisms.
Recently introduced non-native species include the
round goby and the spiny and fishhook waterfleas.
Round gobies eat zebra and quagga mussels and in
turn are eaten by native and non-native fish species.
Unfortunately, zebra and quagga mussels and the
round goby are suspect in the growth and transfer of
Type E botulism, which has now been detected at a
few locations along the Lake Ontario shoreline.
Contaminants
As a result of actions taken by Canada and the
United States to ban and control contaminants such
as PCBs, DDT, mirex, dioxin/furans, mercury and
dieldrin entering the Great Lakes, levels of
contaminants in the Lake Ontario ecosystem have
decreased significantly over the past 20 - 25 years.
Despite this decline, levels of some contaminants
detected in fish still exceed consumption guidelines
for humans.
Contaminant levels in herring gull eggs have
decreased dramatically; successful reproduction is
occurring; and, bird populations have generally
increased. Many fish and wildlife populations once
on the verge of extinction have rebounded from the
effects of contaminants. Key indicator species such as
the bald eagle, river otter, and mink, are making a
comeback in the Lake Ontario ecosystem. Aquatic
Lake Superior
Lake Michigan
Lake Huron
Lake Ontario
Lake Erie
communities, however, are still under stress. It
appears that the most significant sources of critical
pollutants to Lake Ontario now arrive from upstream
inputs and via atmospheric deposition.
Lake level regulation
Lake level regulation has had serious and lasting
impacts on Lake Ontario's natural resources,
including fish and wildlife, shoreline habitat and
dune barrier systems, and numerous wetland
complexes along the shore. Reductions in the area,
quality, biodiversity, and functioning of Lake Ontario
nearshore wetlands are some of the inadvertent
consequences of artificial management of lake levels.
Habitat alteration
In addition to artificial lake level management and
the proliferation of non-native species, the physical
loss, modification, and destruction of habitats,
through deforestation or the damming of tributaries
are all threats to the success of fish and wildlife
populations. Wetlands are particularly vulnerable to
activities such as in-filling and dredging. It is
estimated that about 50 percent of Lake Ontario's
wetlands have been lost throughout the basin as a
result of habitat alteration.
-------
LAKE ONTARIO PRESSURES
Aquatic food web changes
The offshore lake ecosystem (greater than 15 meters
deep) heavily relies on stocked salmon and trout to
provide recreational fisheries and to control
populations of non-native alewife and smelt.
Chinook salmon, coho salmon, brown trout, and
rainbow trout continue to support recreational
fisheries and display variable rates of wild
reproduction. The current salmon and trout complex
remains reliant on alewife and smelt, and both of
these preyfish species are in mixed or deteriorating
states. In response, top predators, particularly
Chinook salmon, are showing signs of reduced
weight.
Other pressures on the Lake Ontario fishery include
increasing competition for food by invasive species
such as the round goby; consumption of fish by
cormorants; thiamine deficiencies resulting in
increased mortality of young fish; overfishing and
continued reliance on stocking; and the presence of
contaminants in many fish species including walleye
and trout.
Urbanization
Land use and population growth, particularly low-
density urban sprawl in the Golden Horseshoe
(Toronto area), are impacting Lake Ontario and the
stress is growing. By 2030, it is projected that an
additional three million people will live in the Lake
Ontario basin, with almost all of the growth
concentrated at the western end of the Lake, in
Ontario. Some consequences of urbanization include
increases in the amount of impervious land area,
stormwater runoff, and vehicular travel and
transportation-related emissions.
Current Actions
To help meet Great Lakes Water Quality Agreement
commitments, the governments of the United States
and Canada agreed to develop and implement
Lakewide Management Plans (LaMPs) for open lake
waters and Remedial Action Plans (RAPs) for specific
geographic Areas of Concern (AOCs). The Lake
Ontario LaMP works closely with the Great Lakes
Fishery Commission to identify priority projects and
develop appropriate aquatic habitat ecosystem
objectives and indicators.
Actions Needed
To protect the Lake Ontario ecosystem the following
actions are needed:
• Design communities that accommodate more
people without rampant urban sprawl and
destruction of habitats
• Prevent the introduction of non-native species
• Continue to monitor and control contaminants
• Inform lake level regulation managers of changes
in fish and wildlife populations
• Monitor the subtle but important changes
occurring in the Lake Ontario food web so that
appropriate actions may be taken
To Learn More
For further information related to the state of Lake
Ontario, 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. The Lake Ontario
Lakewide Management Plan 2004 can be accessed at
www.epa.gov/glnpo/lakeont/2004update/.
Lake Ontario shoreline, Oswego, New York. Photo:
U.S. EPA Great Lakes National Program Office.
02/06
EPA 905-F-06-912
IISG-06-05
------- |