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The overarching objective of the NB Coastal Case Study is to identify the fate of Hg in coastal
ecosystems of the Bay of Fundy, and the susceptibility of this coastal region to local and longrange sources of atmospheric Hg contamination. Specific objectives refer to:
1. Identification of the principal inputs of Hg in coastal regions
2. Characterization of the cycling of Hg in coastal subcatchments
3. Determination of the susceptibility of benthic organisms, fish and seabirds to Hg
deposition and local sources of contamination.
4. Integration of results to develop whole-ecosystem model of Hg dynamics in coastal
regions to forecast Hg levels in predatory fish and seabirds from inputs of Hg to the
system.
5. Installation of a local resource link to the COMERN study of Hg food web effects on
human health.
6. Synthesize results to analyze the management and policy implications for regulations of
transboundary Hg contamination on the Maine-New Brunswick border and managing
ecosystem impacts of Hg in the Bay of Fundy.
1. We undertook an extensive sampling efforts to establish geo-spatial and ecological patterns
that deal with Hg accumulations in various bio-sphere strata: forests canopy, forest floor, forest
soils, bedrock, forest streams, tidal marshes, beaches, coastal waters, marine and freshwater
sediments, aquatic biofilms on rocks, sediments and macrophytes, various organisms from low to
highest trophic levels, including hair samples from people. We found:
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a strong geo-spatial gradient, showing elevated Hg levels in most matrices including human
hair on Grand Manan, and least levels inland. Diet questionnaires revealed a direct link
between Hg in hair (mainly MeHg) and fish consumption.
highest Hg levels in aqueous solutions occur in forest soils, brooks, ponds, seeps; with
increased canopy opening, and moving from freshwater to salt water, Hg levels drop sharply
in coastal waters, highest Hg levels are associated with brown waters, i.e., waters with high
levels of dissolved organic carbon (DOC)
high levels of Hg were found in freshwater biofilms
levels of Hg in snow are highest in freshly falling snow; Hg levels drop thereafter, within
hours or days, even underneath closed forest canopies
an empirical model was established to predict levels of DOC and Hg in coastal waters
depending on source of water, as affected by terrain
Hg levels in freshwater fish increased with amount of DOC in water, for fish of same size
Hg levels in marine fish followed the expected bioaccumulation patters from low in low
trophic levels to high as in sea birds and sea mammals
Store-bought fish did not to exceed recommended Hg levels, this includes cans of solid tuna;
Hg levels in marine sediments were generally low compared to, e.g., St. Lawrence
sediments; hotspots were found at select locations, esp. Seal Cove, Grand Manan, and fish
waste underneath aquaculture cages.
We developed an inexpensive way to catch fog water for Hg analysis: 24 units are now
available to establish insight in terms of Hg loadings due to fog, at select high-fog locations
at the coasts, e.g. Mace’s Bay, Seal Cove.
2. We are in the process of modelling Hg transfers into, through and from coastal catchments. For
this purpose, we have developed the following:
a) a hydrological model to simulate all major water and heat flows through forest (and nonforested) coastal catchments, summer through winter, with and without snow
b) a forest biomass model to determine biomass and Hg build-up in the various above and
below-ground biomass and Hg compartment of coastal forests
c) an empirical model between DOC in water and Hg associated with DOC; we note that the
ration of Hg in DOC is similar to the ration of Hg in soil organic matter
d) and empirical model that releases DOC from coastal catchments based on local topography
and other catchment features
e) a fog interception model designed to capture transfer of fog water and fog Hg into coastal
catchments
3. In terms of process studies, we still need to focus attention on where and when MeHg is
produced within the coastal catchments. We already know that MeHg levels in coastal fresh
waters are highest in late summer, and we need to conduct rate determining experiments in
wetlands such as bogs, swamps, and other poorly drained forest areas, as well as tidal pools, to
make specific observations of the Hg methylization process. In this, we need to follow up with
Hg transference study in brown versus clear water streams, to determine extent of Hg in biofilm,
transference from biofilm to benthic organisms, and from benthic organisms into fish. These
studies are coupled with isotopic C and N analysis to affirm sequence of transference from one
trophic level to the next.
4. The next stage is to integrate these models and related process formulations into a coastal Hg
transfer model that is driven by weather, and our knowledge of within-forest Hg retention and
release, and to extent this model to forest streams, tidal marshes, and coastal waters, to assess
extent of Hg evasion back into the atmosphere.
5. Through the environmental education program, we intend to install a community-based
resource link to the COMERN study of Hg food web effects on human health.
6. Through invitations, we are now participating with local regional government and industry
associations to analyze management and policy implications of the Coastal Case Study.