Kristin J. Orians
University of British Columbia
In collaboration with:
Alyssa Shiel, Dominique Weis
Anka Lekhi, David Cassis,
Maite Maldonado
University of British Columbia
Chris Pearce
Pacific Biological Station, DFO, Nanaimo
•  Dissolved vs. Particulate
•  Natural
–  Upwelling
–  Local mineralogy
•  Anthropogenic
–
–
–
–
–
–
Mine drainage
Incinerators
Metal smelters
Phosphate fertilizers
Sewage treatment plants
Pulp mills
Logging near Effingham Inlet,
Barkley Sound (Kruzynski, 2004)
•  Oysters and mussels from B.C.,
Mexico, California, and
Washington (1)
•  Oysters of Oman (2)
•  Scallops of the Ross Sea,
Antarctica (3)
•  Mussels of the Kuril Islands
(Russia) (4)
Diss. Cd (nmol/kg)
Temp (oC)
High
Cd!
Merrin & Orians
Upwelling
locations
Three distinct upwelling locations,
each with low T and high Cd!
(Cd from 0.2 to 0.5 nmol/kg)
upwelling
Cadmium elevated during
upwelling events
(Cd: 0.7 to 1.0 nmol/kg)
Mussel Cd followed
(Amphitrite Point - West
coast Vancouver Island)
(Lares and Orians, 1997)
Dissolved Cd
Particulate Cd
Oyster
But…
•  Annual / seasonal cycles
•  Effect of environment (Sal., Temp., etc.)
•  Not all particulate matter is the same!
Sampling sites
Deep Bay
Lemmen’s Inlet Priyanka Lekhi, D. Cassis, C.M. Pearce, N. Ebell, M.T. Maldonado, K.J. Orians, 2008. Role of
dissolved and particulate cadmium in the accumulation of cadmium in cultured oysters
(Crassostrea gigas). Science of the Total Environment, 393, 309-325.
•  Annual cycle: Oyster Cd high in winter, low in
summer
•  Dissolved Cd: main source for oysters in Deep Bay
•  Particulate Cd: a sink, not a source
•  Growth: dilutes oyster Cd concentrations in summer
•  Environment: temperature, salinity, etc. - strong
seasonal effect
•  Phytoplankton/particulate Cd: a sink, not a source
of Cd for oysters!
•  Phytoplankton lowers dissolved Cd
(makes Cd less available to the oysters)
•  Phytoplankton abundance AND composition
important
(some species are not oyster food)
•  Many phytoplankton not eaten by oysters
(harmful, big, spiny algae)
•  Phytoplankton and Cd removed by sedimentation
Harmful algal bloom
(HAB)
Phytoplankton
Dissolved Cd
Oyster
Arrow width: 2 x natural logarithm
of p-value of correlations
Sedimentation rates from GarciaHernandez et al, 2005
Sediment
Spring
Summer
Fall
Winter
Phytoplankton
Diatom blooms, high
sedimentation
HA Blooms, very
high sedimentation
Diatom blooms, low
sedimentation
Very low
Dissolved Cd and
nutrients
High: winter renewal
Low: strong
phytoplankton
uptake and removal
Medium
High
Oyster Cd
High: winter
Low: growth and
reduced exposure
Starts increasing
due to exposure
High
Strong water mixing
begins
Strong water mixing
Decreasing
Decreasing
Increasing
Decreasing
Oceanography
Strong water mixing
Thermo/halo
stratification
•  Models under
development:
use variables easy to
measure in field (temp.,
salinity, oyster age,
dissolved nutrients) to
predict oyster Cd.
•  Need validation with
other datasets! (only for
Deep Bay now)
•  Potentially very useful
for oyster growers!
Seasons
Phytoplankton
HAB
Growth
Reproduction
Oceanographic
processes
Sediment
Dissolved Cd
West side of Vancouver Is.
Isotopes: same atomic number (same chemistry)
different mass (different reaction rates)
(‰)
Also reported as δCd/amu, e.g. δ114Cd/amu = δ114Cd / (114-110)
Cd isotope variations relative to High Purity Cd standard
(similar to most terrestrial rocks - the “natural” signature)
“Light” = more negative = less 114Cd
Desolation
Sound
Barkley Sound
North
Brittany
Gironde
estuary
Light
Heavy
Gulf of Lion,
Mediterranean
Cd isotopes “lighter” in some oysters than others.
Why?
Note: Total oyster Cd (concentration) is not
correlated with Cd isotopes!
• Biological Fractionation?
- by oysters?
- from their food?
• Anthropogenic Sources?
• How do values compare to local seawater?
Phytoplankton
preferentially
take up “light”
Cd!
Oysters may also
fractionate Cd?
Oysters may
assimilate light
Cd from
phytoplankton?
Edmonton
Calgary
Vancouver
Teck Trail operations
light
heavy
heavy
End
product
Source material
Effluent
Fumes
light
Cd isotopes
fractionated
during
smelting and
refining
Cd isotopes in BC
oysters: a bit lighter
than North Pacific
seawater.
?
Smelter emissions
could contribute to
lighter isotopes in
oysters.
Pollution source?
light
heavy
light
heavy