COMERN Project Description
16/02/16
PROJECT DESCRIPTION
1. Identification:
Project Manager: Dr. Asit Mazumder
Department of Biology, University of
Victoria, Victoria, BC
Research Title: Ecosystem and watershed-level dynamics of mercury in aquatic food webs
of Coastal and Inland lakes and reservoirs in British Columbia
Research Theme: Aquatic food web and wildlife contamination
Theme Leader: Dr. Mike Paterson
Collaborators:
Dr. Kevin Telmer
School of Earth & Ocean Sciences, University of
Victoria, Victoria, BC
Dr. Rick Nordin
BC Ministry of Air, Land and Water Protection, Victoria,
BC
Dr. Max Bothwell
National Water Research Institute, PBS, Nanaimo, BC
Dr. John Richardson
Department of Forest Sciences, Univ. of British
Columbia.
2. Project summary
Climatological and geomorphological characteristics may be important in producing distinct
water quality and plankton community patterns in coastal lakes of British Columbia (BC) as
compared to those in Canadian Shield lakes. Unlike the dimictic and cold temperate lakes of the
rest of Canada, a large number of the lakes in coastal BC do not freeze and they mix once a year
(monomictic). While an extensive amount of research has been done on the patterns of mercury
(Hg) accumulation in plankton and fish communities of lake ecosystems in central and eastern
Canada, very little systematic Hg research has been done on BC lakes. Within this project, there
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COMERN Project Description
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are several regional and general components. One regional component seeks to understand and
document the regional Hg cycle in BC lakes and the other seeks to identify and understand the
critical transport pathways for Hg in these systems. Questions being addressed are: How is Hg
distributed in west coast ecosystems? Are sources and pathways similar to boreal watersheds?
What is the impact of glacial rock floor? How significant are disturbances such as logging and
other land-use practices? To accomplish this, 14 lakes and reservoirs in Vancouver Island, the
Gulf Islands and Vancouver are being sampled and analyzed for a variety of media including the
dissolved load and suspended load of waters, the solids and pore waters of lake sediments, and
plankton and fish communities of several size-categories. In terms of Hg transport and uptake,
we examine the role of natural organic acids on mercury binding, transportation, methylation,
and biological uptake in BC ecosystems. Questions being addressed are: which dissolved organic
substances dominate Hg mobilization? Is the presence/absence of these substances good
predictors of Hg bioaccumulation? How is pH related? As they co-vary with dissolved organic
carbon (DOC), are both pH and DOC equally important predictors of Hg bioaccumulation? What
are the processes regulating Hg accumulation in zooplankton. Could fatty acids be used as tracers
for the sources and pathways of Hg in zooplankton?
The results of these investigations will be combined with our nutrient-food web research to better
understand the pathway of Hg into fish. We have already been establishing the patterns of
nutrient dynamics and food web structure of 14 BC lakes to develop water quality models. This
database will allow us to link nutrient-food web dynamics with Hg dynamics in plankton and fish
communities. During the last 10 years of research, we have shown that patterns of nutrient and
contaminant fluxes along aquatic food webs are strongly correlated with the concentration of
nutrients and the structure of aquatic food web. It has also been shown that the biomass of algae
and bacteria increase with increasing concentrations of nutrients, but the impact of nutrients are
dependent on the structure of consumer communities, or in other words, on the patterns of
aquatic food webs. Among temperate lakes, the densities and size-distribution of both predatory
and zooplanktivorous fish vary substantially. When the density of large predatory fish is low
either due to over-exploitation of fisheries or due to loss of suitable habitat, the density of small
zooplanktivorous fish seem to be high, which reduce the density of large zooplankton grazers of
algae and bacteria. Overall impact of changes in nutrients and predatory fish are often reflected
by the size-distribution of plankton and fish. Thus, we will test if the concentration of MeHg in
fish could be a function of size-distribution and community structure of plankton communities,
as we have found it for the transfer and accumulation of nutrients and organochlorine compounds
in plankton and fish. We also know that the growth rates of fish are quite variable among lakes.
We will use juvenile sockeye salmon as an example to test the hypothesis of the dilution of Hg in
fish tissue as a function of growth rates. This hypothesis will tested using fish from 12 sockeye
salmon lakes in BC and Alaska.
3. Research objectives
COMERN Head Office: Université du Québec à Montréal, President-Kennedy Bldg – Suite PK-7150 C.P.8888,
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COMERN Project Description
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•
Develop models linking DOC-nutrient-food web characteristics with the concentrations of
Hg in plankton and fish of streams, lakes and reservoirs in BC
•
Characterize and quantify the processes regulating the cycling and mobilization of Hg in
lakes and reservoirs.
•
Model the patterns of Hg bioaccumulation in fish as a function of growth rates.
Details
Actually, it is not known yet whether the Hg pollution of aquatic ecosystems and their fisheries is
as intense in BC as it has been observed for other regions of Canada exposed to enhanced
atmospheric Hg loadings. The proposed study sites in Greater Victoria falls within a belt of semiarid climate with very little rainfall during summer months and is characterized by very little or
no snowfall and sub-zero temperature during winter months. The lake and reservoir ecosystems
support several species of salmonidae species. They offer a wide spectrum for the aspects of land
and water-use activities and ecological characteristics which may have significant implications
for mobilization and food web accumulation of MeHg i.e. i) a large gradient of nutrients (N and
P), size-distribution and concentration of algal and microbial communities, ii) a large gradient in
the size-distribution and composition of zooplankton communities, especially in the grazers of
algae and bacteria, iii) a set of reservoirs fully protected from any human activities but having
similar salmonid communities, thus possibly used as reference ecosystems, iv) a significant
amount of forest harvesting activities in six of these ecosystems, responsible for significant
erosion and sediment loading. The largest watershed we intent to study is the Victoria Water
Supply Area (70 km2), protected since 1913. It includes 5 reservoirs, created over the last 60
years, including the Sooke Reservoir, which will be raised by 5m in 2002. The later intervention
will provide an excellent opportunity to address several objectives related to the dynamics of Hg
remobilization following inundation, and this, for the first time in BC.
In detail, we will concentrate on the following environments:
- Five reservoirs of the Victoria Water Supply Area, containing large communities of land-locked
salmonidae species.
- Three lakes in Greater Victoria area (Shawnigan, Elk, Beaver) of importance for sport fishery
(kokanee, cutthroat, lake trout and bass communities).
- Nanaimo Reservoir within the watershed supplying water to the City of Nanaimo. Fertilization
of the watershed is being practiced by the local lumber company to enhance forest productivity
and effect on the aquatic food web and on the mobilization and bioaccumulation of MeHg is
unknown.
- Two reservoirs and two lakes in Cranbrook and Kimberly in the Eastern Kootenay region,
famous for sport fishing of Kokanee salmon, and facing harvesting activities. Two of these
ecosystems can be considered as high altitude lakes (4000m ASL).
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COMERN Project Description
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- Two lakes on the Salt Spring Island facing extensive land-use activities from forest practices
and residential development.
- In near future, addition of Kootenay Lake and Arrow Lake systems is planned. These large lake
systems are extremely important for both commercial and sport fisheries and have been going
through significant changes in water quality and food web structure.
1. Nutrient-food web dynamics of Hg bioaccumulation in plankton and fish.
We will characterize, quantify and model the patterns of MeHg bioaccumulation in salmonidae
species under a gradient of nutrient and food web structure. 10 years of research permit us to
assert that patterns of nutrient and contaminant fluxes along aquatic food webs are strongly
determined by nutrient and food web structure. Accumulation of MeHg in fish could be a
function of size-distribution and community structure of plankton communities, as for the
transfer and accumulation of nutrients and organochlorine compounds. To address the hypothesis
of MeHg bioaccumulation right from the base of the food chain, we will analyze MeHg and total
Hg in four different size-categories of plankton communities (pico- 0.2-2 µm, nano- 2-20µm,
micro- 20-200µm and meso- 200-2000µm), using a large fabricated filtration device to collect
sufficient quantities of materials for the analysis of Hg in each size-category.
2. Factors and processes regulating the cycling and mobilization of Hg.
We intend to study and assess the factors and processes influencing the dynamics of Hg cycling,
using radioisotopes and enriched stable isotope tracers and/or complementary analytical
techniques. The role of natural organic acids on Hg binding, transportation, net uptake rates and
possibly net methylation rates will be evaluated by tracing these processes with isotope enriched
Hg and inductively coupled plasma mass spectrometry (ICP-MS) technology. The correlation
between DOC and Hg in waters is well documented. Organic acids might react with Hg residing
in or emitted from different sources such as soils, natural degassing, forest fires, fuel combustion,
gold mining activities, etc. to form soluble Hg-organic complexes. The formation of these
complexes is believed to greatly enhance Hg transport and be an important preliminary step in
the formation of MeHg and biological uptake. The rates of these reactions and the key organic
compounds involved in Hg binding will be determined by reacting isotope enriched Hg with
samples containing a variety of concentrations and types of organic acids, and subsequently, by
analyzing both reactants and organisms exposed to the reactants (bioassays) for Hg isotopes by
ICP-MS. The Hg spike will allow us to determine the rates of uptake and the most active agents
in that process. Initially, the method will be used to examine total Hg uptake and distribution but
if technological limitations are overcome, this same approach can be used to determine net rates
of methylation and net MeHg uptake. Ultimately, this research should contribute to an
understanding of Hg mobilization, transport and bio-concentration mechanisms, and provide a
basis for developing management strategies to minimize biological uptake of Hg – for example
in drinking water and hydro-electric reservoirs. Emphasis will be on the Hg bioaccumulation
processes occurring in high DOC ecosystems.
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COMERN Project Description
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3. Temporal patterns of Hg bioaccumulation using fish otoliths in a newly flooded reservoir
as a function of growth rate.
We will determine the patterns of Hg accumulation in fish following the raising of the level of
Sooke Reservoir in 2002. Hg analyses in the salmonidae species otoliths will be performed using
ICP-MS with Laser Ablation Technique. The 3 reservoirs in the same watershed and the nearby
Shawnigan Lake, at the same altitude and of very similar morphometry, will be used as reference
lakes. Fish otoliths of different age-classes will be analyzed for 2 years prior to flooding (2001
and 2002) and for 2 years following inundation (2003 and 2004). The same otolith technique will
be used in 12 lakes and reservoirs, providing gradients in nutrients and food web structure, to
address the relationship between growth rate of fish (based on the width in growth rings and
using back calculation method for growth) and Hg bioaccumulation.
COMERN Head Office: Université du Québec à Montréal, President-Kennedy Bldg – Suite PK-7150 C.P.8888,
Downtown STA (Qc) H3C 3P8. Phone: (514) 987-3601, Fax : (514) 987-3635
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