Lake Melville

Biological measurements in Lake Melville
We collected fish from a variety of habitats in the Lake
Melville ecosystem and analyzed them for total and
methylmercury concentrations. We also analyzed the
amounts of carbon, nitrogen and mercury isotopes
in their tissues that can be used as an indicator of
their trophic positions, food webs, terrestrial vs.
marine habitat and the environmental sources of
methylmercury that are accumulated in the fish.
Environment Canada provided us with concentrations
of mercury in birds and eggs commonly harvested
in the Lake Melville region. A variety of seals were
also harvested and analyzed for mercury and various
isotopes in collaboration with Environment Canada.
These data were used to estimate biomagnification
factors between water and fish/seal, baseline
exposures of Inuit, and how much time each organism
consumed by Inuit spent in the Churchill River, Lake
Melville estuary and the open ocean regions. The
time spent in each environment was used to link
the impacts of Muskrat Falls flooding to changes in
biological concentrations.
Dietary survey and biomarker analysis
We assessed current methylmercury exposures for Inuit
in the communities of Rigolet, Happy Valley-Goose
Bay, and North West River by collecting dietary recall
data on country food consumption and measuring
concentrations of mercury in hair. Hair mercury levels
are a good indicator of methylmercury exposure. Prior
to our study, there were only a few measurements of
mercury concentrations in Inuit hair from the Lake
Melville region. In addition, data on the types and
amounts of food consumed were limited.
We designed a food frequency questionnaire, which
is a commonly used method for assessing the diet
composition of different individuals, to characterize
the amounts of aquatic foods consumed by Inuit in the
Lake Melville region. After training, research assistants
distributed the survey in the communities of Happy-
Valley Goose Bay (including the community of Mud
Lake), North West River and Rigolet in March, June and
September 2014 (see Section 10.3 in the Appendix for
additional survey methods). Our goal was to collect
information from approximately 10% of the total
Inuit population in March and June and as many Inuit
community members as possible in September. Total
participation in our survey was 231 in March, 294 in
June and 1,057 in September. Of these participants, 157
in June and 499 in September provided hair samples
from the occipital region of the scalp (back of the
head) in sufficient quantity for mercury exposures to
be directly measured. The survey collected information
on consumption of 65 local foods and 24 store-bought
seafood items. Participants were asked to recall their
consumption (meals per day) over the previous 24
hours, one-month and three months. They were also
asked to identify their typical meal sizes by choosing
among clay serving models for each reported food.
We measured total mercury in the two-centimetre
proximal end of all hair samples (hair close to the
root). Total mercury concentrations were quantified
by thermal decomposition, amalgamation, and atomic
absorption spectrophotometry [EPA method 7473 (U.S.
EPA, 2007)] using a Nippon Direct Mercury Analyzer.
The instrument was calibrated with a liquid inorganic
mercury standard, with daily verification across a
range of mercury masses using two certified reference
materials (MESS-4 and TORT-3, National Research
Council Canada). Precision, estimated by replicate
analysis of the reference materials and duplicate
hair samples, was better than 4% and 9% (RSD),
respectively.
Methylmercury exposures can be assessed indirectly
by multiplying the concentration in different foods by
the amounts consumed or directly by the measured
levels of mercury in hair. We used both approaches in
our study. Methylmercury concentrations in different
food items were obtained from direct measurements of
mercury content for some local foods and an extensive
literature review for others.
The research design prioritized local involvement
and capacity building. Survey and hair sampling
work was carried out by a total of 28 local (26 Inuit)
Research Assistants, who completed two days of
training, and worked an approximate total of 1,566
person-hours. Project communications included
community information sessions, pamphlets, direct
mail-outs to participants, posters and social media
updates. Focus group sessions were conducted with
Community Research Advisory Committees in all Upper
Lake Melville communities and Rigolet, to improve
the food frequency survey during its development.
Changes to survey and hair sampling dates and sample
sizes were made based on knowledge and advice
provided. Likewise, the addition of local terms to the
initial survey, and the assistance that the Community
Research Advisors provided the study team in
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