Lecture 12 Flashcards
(21 cards)
what is the relationship between organic carbon and contaminants?
- total organic carbon influences the bioavailability of the organic contaminants
- high organic carbon sediments = more binding sites for PCBs = lower PCBs in the interstitial waters, which means a potential for lower toxicity for organisms whose exposure route is mainly through suspension feeding
- low organic carbon sediments = few binding sites for PCBs = higher PCBs in interstitial waters = increase toxicity for suspension feeders
what are the characterizations of ringed seals?
- top of the local web
- valued food for inuits
- dominant prey for polar bears
- vulnerable for POP accumulation (high in marine food chain, large fat reserves, long lived)
- exposed to many stressors (contaminants, changing sea ice conditions, disease, industrial activity)
what are the ways that ringed seals come in contact with contaminants?
- local sources
- long range transport
what was the research objective for contaminants in ringed seals?
assess whether the local source at saglek bay is contributing to the elevated PCB levels in ringed seals from the northern labrador coast
were ringed seals impacted by PCBs?
yes, PCBs dominated the POPs in ringed seals in the saglek fjord (68% of the total POP concentration)
- two fold greater than observed elsewhere in the canadian arctic
what did principal components analysis reveal?
some seals have heavier PCB patterns, consistent with exposure to a local PCB source
what did the physico-chemical properties (Log kow) of PCB congeners suggest?
that there are two groups: local vs. long range
- PCB concentrations in ringed seals are higher in ‘local’ ringed seals compared to ‘long range’ seals
what was the second objective of observing contaminants in ringed seals?
can we use satellite telemetry to evaluate whether contaminant profiles can indeed be used to assign seals to either ‘local’ or ‘long range’ categories
- it is hypothesized that satellite telemetry and Carbon 13 and nitrogen 15 can be used as measures of habitat use that will validate the PCB signature
how did seal tagging work?
- 13 ringed seals were captured from various locations in saglek fjord during august and september
- PTTs were programmed to send up to 250 transmissions per day
- PTTs record locations and depth
what were the results of the tagging and analysis?
- the geometric means PCB concentrations in ‘local’ ringed seals were 4 fold higher than ‘long-range’ seals, suggesting that 75% of the PCB burden of ringed seals sampled originated from the local PCB source at saglek bay
- OCP concentrations did not differ
what were the study’s finding?
- reduced size of home range and core area as well as increased time in coastal inlets were important determinants of increased PCB concentrations
- a link was highlighted between feeding ecology and exposure to PCBs
Contaminant levels and patterns among prey species can differ due to differences in
trophic positions, foraging strategies, and metabolic transformations along with other
biological factors.
Thus, two mechanisms could explain the divergent PCB pattern and increased PCB
concentrations in locally versus long-range contaminated ringed seals:
1) differences in prey selection between the two groups
2) feeding on similar prey items that are more contaminated in saglek bay
what was the 3rd objective of the study on ringed seal PCB contamination?
Can we use fatty acid and PCB signature analysis in ringed seals and
their prey to determine which mechanism may be involved?
what are the results of the combined approaches?
- up to 60% of ringed seals frequenting the labrador coast have been influenced by a military radar station PCB spill at saglek bay
- local source explains ~50% of the PCB burden
- seals with higher PCB levels and heavier PCB patterns have smaller home ranges, consistent with local contamination
- ringed seals appeared to feed predominantly on zooplankton, followed by dusky snailfish, arctic cod, and shorthorn sculpin
- locally contaminated prey had PCB levels that were 2- to 544-fold higher than prey contaminated by long range sources
- results strongly suggest that habitat use rather than differences in prey selection is the primary mechanism explaining the divergent PCB patterns
- affected adult males may be at risk for adverse health effects
how were PCB health effects in ringed seals tested?
- liver mRNA abundance levels of 8 gene transcripts involved in endocrine/immune function and xenobiotic detoxification were measured
- five gene transcripts correlated with PCBs
- best fit models confirmed that PCBs best explained the variation
- no relationship between the five genes transcripts and PCBs for sub adults and adult females
- 3 of the 5 gene transcripts correlated with PCBs for adult males
what is the summary of the research done on PCBs in ringed seals?
- PCBs are adversely affecting molecular endpoints in ringed seals, the consequences at the population level are unclear
- a PCB effects threshold was established for ringed seals, which can serve as a practical tool for mitigation and monitoring efforts in the north
- results provide guidance for monitoring, management, and remediation of contaminated sites
how do we rank/prioritize the contaminants of concern for chinook and resident killer whales?
Chinook
1) risk quotients = chinook / effects threshold for fish
2) exposure activity ratios = chinook / bioactivity effect
Resident killer whales
1) risk characterization ratio = chinook / tissue residue guideline
2) risk quotients = killer whale blubber / PCB marine mammal threshold
what are exposure activity ratios (EAR)?
- defined as the ratio of a measured concentration and a concentration that was determined to cause some activity in a specified ToxCast assay (‘endpoint’ concentration)
- and EAR > 1.0 would indicate that the measured concentration is greater than the endpoint concentration
- best applied to water contaminant concentration data
- tissue concentration data = BCF correction can be applied
what are in vitro cell line approaches?
- the intent to reduce, refine, and in some instances, replace the use of animals in
toxicity testing has spurred the development of high-throughput screening (HTS) assays that eventually may be used for chemical risk assessment - HTS assay data from the ToxCast and Tox21 programs are efforts aimed at providing methods for ranking chemicals by various metrics
what is ToxCast?
- in vitro medium and HTS assay data that is publicly available for prioritization and hazard characterization of thousands of chemicals
- the assays employ a variety of technologies to evaluate the effects of chemical exposure on diverse biological targets
- data aggregated from 20+ assay sources
- chemical exposure to 10,000 analytes
what are the calculations related to harbour seal contaminants?
- comparative risk quotient (CRQ):
CRQ = [POP]/TRV where TRV is the daily intake rate related to a defined effect in rodents (in mg kg^-1 day^-1) - corrected for body weight:
TRVseal = TRVrodent x (BWrodent/BWseal)^1-b
