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Fish and Wildlife Health Effects
in the Canadian Great Lakes Areas of Concern
Early Findings for Wildlife in the Lower Great Lakes
In 2000, Health Canada compared the incidence of morbidity and
mortality in human populations in the 17 Areas of Concern (AOCs)
in Ontario to rates for the province as a whole. The Health Canada
reports were based primarily on hospital and census databases. For
each AOC, specific data were compiled on a variety of diseases and
disorders,
such as:
- cancer incidence;
- reproductive disorders; and,
- congenital deformities.
Different rates were reported across AOCs. A second, independent
analysis of the Health Canada data focused on two highly industrialized
AOCs, Windsor and Hamilton [see Environmental Health Perspectives
109 (6): 827-843 (2001)]. It hypothesized that the elevated rates
of mortality, morbidity (illness) and congenital (birth) anomalies
in the Windsor AOC might be related to ambient levels of pollution.
Historically, studies of wildlife have provided a useful early
warning of effects that might occur in human populations. Since
the early 1970s, there has been widespread interest in understanding
toxic contaminants and their effects on animals. Early concerns
stemmed from reproductive and developmental effects that were first
reported in the Great Lakes, particularly in colonial fish-eating
birds. However, research on fish and wildlife health effects has
not been extensive and no systematic monitoring of health effects
occurs in AOCs.
Programs to monitor levels of persistent toxic chemicals are well
established in the Great Lakes andshow significant reductions in
most traditionally measured chemicals. However, levels of some new
chemicals, such as PBDE flame retardants, commonly used in computer
components, automotive parts and upholstery, are increasing at high
rates and may be associated with health effects.
Environment Canada initiated the Fish and Wildlife Health Effects
and Exposure Study in 2001. The goal of this systematic assessment
in Canadian AOCs is to determine if there are fish and wildlife
health effects, similar to those reported for the human population,
that are associated with contaminants in the aquatic environment.
Phase I (2001-2005) of the study investigates conditions in the
Canadian AOCs of the lower Great Lakes. Upon completion, the need
for assessments at AOCs in the upper Great Lakes will be determined.
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Fish
and Wildlife Health Effects and Exposure Study
As a first step, a summary of existing water and sediment environmental
exposure data was compiled. Information on health effects and contaminant
levels in fish and wildlife throughout the Great Lakes was reviewed.
Systematic information on fish and wildlife health effects was generally
lacking, and exposure data for the biota in many of the AOCs were
out of date. As well, the potential effects of new contaminants
are poorly understood. The knowledge gaps pointed to the need for
an integrated study of exposure and health effects in fish and wildlife.
Objectives
- Document health effects in fish and wildlife by measuring specific
indicators: endpoints that are fundamental to the development,
growth and reproduction of individuals and population status.
Because effects can occur at community, population, individual
and subcellular levels, a range of indicators was chosen. Choice
of indicators was based on sensitivity to chemical exposure, tangible
results in previous studies, simplicity and cost effectiveness.
- Measure current environmental contaminant concentrations in
water, sediment, fish and wildlife in AOCs. Evaluate techniques
in analytical chemistry to measure less persistent chemicals in
water, sediment, fish and wildlife.
- Integrate and assess results in lake-by-lake reports, and make
recommendations for longterm monitoring strategies, if required.
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Preliminary
Results 2002: Effects in Wildlife
This fact sheet summarizes early results of wildlife health assessments
from initial field studies in the Detroit River AOC, St. Clair River
AOC, and western Lake Erie including Wheatley Harbour AOC.
1. Population Trends for Colonial Waterbirds
Populations of colonial waterbirds are surveyed binationally about
every 10 years. Trends from 1977 to 1999 showed dramatic increases
in the numbers of herring (4-fold) and ring-billed (5-fold) gulls,
great egrets (4-fold), and double-crested cormorants (223-fold),
but declines in the numbers of great blue herons (-16 percent),
black-crowned night-herons (-87 percent) and common terns (-26 percent).
Declining contaminant levels have been a major factor in the recovery
and increase of cormorants. Habitat destruction (by cormorants)
and habitat change have contributed to the declines in herons; declines
in terns are influenced by competition with ring-billed gulls.
2. Reproductive Health
The reproductive success of snapping turtles was lower at AOC sites
compared to reference sites, with hatching success being reduced
at the St. Clair AOC and near the Wheatley Harbour AOC. Within the
Wheatley Harbour AOC there were no signs of reproductive activity
by snapping turtles, which echoes findings from similar investigations
in the early 1990s. Growth and development of snapping turtles were
altered at study sites compared to reference (clean) sites, with
particularly poor growth seen in the juveniles from near the Wheatley
Harbour AOC.
Precloacal length, an estimator of penis length, was shorter in
male adult turtles from the Detroit River and in juvenile males
from St. Clair and Wheatley Harbour AOCs than from reference sites.
The sex ratio of herring gull chicks at hatch may be influenced
by contaminants in the egg. More males than females hatched at the
AOCs in 2001, particularly on Fighting Island in the Detroit River.
Balanced numbers, as expected, were seen at the reference sites.
Contaminant-induced early embryonic mortality was an important factor
contributing to the low reproductive success observed in Great Lakes
herring gulls during the 1970s. This study found more dead herring
gull embryos in the Detroit River AOC and western Lake Erie compared
to reference sites.
Morphological abnormalities are seldom seen in adults. However,
one adult male herring gull, nesting downstream from the Detroit
AOC in 2001 had a significantly feminized reproductive tract.
3. Status of Endocrine Systems
The endocrine system helps control physiological functions under
normal conditions and during periods of stress. Pollutants are known
to interfere with these processes and therefore have an impact on
health, development and reproduction.
The egg yolk protein, vitellogenin, is normally produced only by
breeding females. Production of this protein in males is a form
of endocrine disruption. Three of thirty adult male snapping turtles
near the Wheatley Harbour AOC and two of fifteen adult male herring
gulls in the Detroit River AOC had detectable levels of vitellogenin
in their blood.
A hormone, corticosterone, is measured to indicate an animal’s
ability to respond to stress. Levels in herring gulls at AOCs were
suppressed, indicating a reduced stress response.
Thyroids of adult gulls were enlarged (goiter) but produced smaller
amounts of hormone, suggesting that thyroid function was disrupted.
Thyroid function was also impaired in juvenile snapping turtles
at all three AOCs in 2001.
4. Organ Function
Results for several diagnostic tests for organ function were significantly
altered in adult snapping turtles and/or adult herring gulls, particularlyfrom
the Detroit River AOC, indicating changes in key processes important
in the production of enzymes, hormones and energy. The liver enzyme,
EROD, is produced in greater amounts if an animal is exposed to
increased levels of dioxin-like pollutants. Once changes in EROD
activity are detected, more specific endpoints are then measured.
Liver EROD activity was increased in juvenile snapping turtles and
adult herring gulls from the Detroit River AOC, which indicates
activation of an important toxicological response system.
5. Immune Function
Immune systems are important to ward off and fight infection. They
are known to be sensitive to pollutants. One indicator of immune
function, the PHA skin test, was significantly suppressed in young
herring gulls from the Detroit River and young herring gulls and
young black-crowned nightherons from western Lake Erie. This immunosuppression
suggests increased susceptibility to infectious diseases, reduced
ability to grow, compete for food, and to withstand the rigors of
weather and migration, thus reducing their fitness and potential
survival to adulthood.
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Wrap-up
What have we learned so far?
Annual monitoring of contaminant concentrations in herring gull
eggs across the lakes shows that levels of most contaminants continue
to decline. Both obvious and subtle health effects, however, were
observed in fish-eating birds and other wildlife.
The occurrence of specific toxic chemicals in other wildlife is
also of concern. For example, current levels of PCBs in trapper-caught
mink from Lake Erie show increases from 1979 when they were last
sampled. In western Lake Erie, 24 percent of the animals trapped
in 1979 had PCB levels that exceeded the lowest observable effect
level for reproductive impacts, compared to 78 percent of the animals
trapped in 2000. In eastern Lake Erie, results were mixed: exceedences
decreased from 33 percent to 11 percent over the same 20-year interval,
although at Long Point they increased from nil to 11 percent.
To date, this study has consistently documented health effects
in wildlife, indicating that these endpoints are suitable for consideration
in a long-term monitoring program. It is apparent that some of the
subcomponents of the study require two years to ensure adequate
data upon which to base conclusions and recommendations for future
longterm monitoring. Measuring health effects in the field requires
complex methods and study designs. The sampling ‘window’
is very narrow because of the need to measure at specific developmental
stages. Timing of nesting and development can be highly weather
dependant. One of the many factors that may confound the sampling
effort is weather.
Future efforts will build from these findings, resulting in a fuller
understanding and a better-integrated assessment of fish and wildlife
health effects.
What’s next?
The study is moving around the lower Great Lakes and the St. Lawrence
River. Further fact sheets will include health effects in fish and
information on current contaminant concentrations in the environment.
More detailed reports by lake basin are planned, beginning with
Lake Erie in 2004 and Lake Ontario in 2006.
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Great Lakes Fact Sheets |
To order printed copies of this or
any other Great Lakes Fact Sheet, contact:
Environment Canada
Canadian Wildlife Service
4905 Dufferin Street
Downsview, ON M3H 5T4
Tel: 416 739-5830 Fax: 416-739-5845
E-mail: Wildlife.Ontario@ec.gc.ca |
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