Lecture 8

Question 1

what is toxicokinetics?

Answer 1

both what rate a chemical will enter the body and what occurs to excrete and metabolize the compound once it is in the body

Question 2

why might harbour seals be used as a surrogate species for killer whales?

Answer 2

• similar trophic level
• more resident behaviour
• captured more readily
• no conservation listing
• well understood

Question 3

what are the dominant drivers of PCBs and PBDEs in chinook salmon?

Answer 3

marine distribution and diet

Question 4

what are carbon and nitrogen stable isotope ratios and what are they used to measure?

Answer 4

Carbon (δ13C): used to distinguish between marine (or pelagic) versus coastal (or benthic) carbon food sources
Nitrogen (δ15N): used to provide an indication of trophic level

Question 5

what are chinook salmon individuals with heavier PCB congeners associated with?

Answer 5

nearshore feeding behaviour and feeding at a higher trophic level

Question 6

why is the difference between contaminants in nearshore vs. offshore salmon important?

Answer 6

• offshore salmon are typically more lipid rich and are a critical component of SRKW diet
• with the dramatic decline of these fish, SRKW may be more compelled to shift their prey base to the lipid-poor shelf/nearshore salmon which have higher contaminant levels
• efforts to increase the abundance of offshore stocks should be prioritized

Question 7

what are the physical chemical characteristics that affect bioaccumulation pathways/processes?

Answer 7

• log Kow
• molecular size
• molecular structure that makes molecules more or less prone to biotransformation enzymes (eg. location of H atoms on PCB molecules)

Question 8

what are the biological factors that affect bioaccumulation pathways/processes?

Answer 8

• energy/food requirements
• reproduction

Question 9

what are individual based models?

Answer 9

• puts all the processes together into math equations that can be solved repeatedly to simulate the lifetime exposure, assimilation, and loss of chemicals
• these equations consider the animals’ life history, growth, energy requirements and food intake, chemical intake/absorption and elimination
• for females, a submodel can be added for fetal growth, followed by a nursing calf that gets its food energy from milk, which in turn requires greater maternal food intake

Question 10

what is contaminant transfer by lactation?

Answer 10

chemical mass transfer is a function of:
- length of lactation, milk volume and fat content
- chemical partitioning to milk (milk:blubber ratio)
- maternal blubber dynamics
- maternal contaminant burden and change over time

Question 11

what are killer whale biomagnification factors?

Answer 11

• biomagnification factors vary with sex, age, and reproductive activity
• adult male BMF = 30-60
• adult female BMF = ~20
• juvenile BMF values are highly variable depending on: birth order and interval, duration of nursing, age and growth

Question 12

what population dynamics affect contamination concentration?

Answer 12

• mortality/predation
• immigration/emigration
• maturation - males vs. females
• juveniles - biodilution (switch from feeding on milk to prey)

Question 13

what are population based bioaccumulation models?

Answer 13

• adds annual summaries of contaminant fluxes to a population dynamics model
• can track changes in contaminant burdens in a population across generations
• output matrix for 2 sexes x 50 age classes x 60+ years
• potential to add effects of contaminant burdens on mortality and reproduction from dose-response relationships