Event Title

Assessing PCB and PBDE Biotransformation and trophic transfer Salish Sea food webs using stable carbon isotope analysis and enantiomeric fractionation

Streaming Media

Presentation Abstract

PCBs and PBDEs are ubiquitous contaminants that are biotransformed into hydroxylated (OH-) forms among other metabolites. OH-PCB/PBDEs are toxicologically important due to adverse effects on the thyroid system. Their environmental occurrence is complex because they are also formed through abiotic processes and for some OH-PBDEs, are marine natural products. Thus, the presence of PCB and PBDE congeners and their OH- derivatives in biota represent a mix of bioaccumulation and formation via biotransformation. We previously measured OH- PCB/PBDEs in shellfish and fish collected from Puget Sound (PS) and recently in blubber samples from Southern Resident Killer whales (SRKW). Comparison of shellfish and finfish results indicated finfish had higher levels of PCB/PBDEs but relatively low levels of the OH- derivatives. In contrast, bivalves had the highest levels of OH-PBDEs, while SRKW blubber contained high levels of naturally occurring PBDE derivatives but low levels of OH-PCB/PBDEs. Biotransformation can introduce carbon isotope effects causing a shift in the 13C/12C ratio (δ13C) of both the parent congener and OH- metabolites. In SRKW blubber, δ13C values for several PCB congeners, most notably PCB 18, were enriched in 13C relative to values in commercial Aroclor preparations. Select PCB congeners are chiral and industrially formed at racemic levels. Enantiomeric fractionation can occur during enzymatic OH-PCB formation. We observed the most pronounced fractionation with PCB-95 and PCB-149, with both Chinook salmon and SRKWs displaying preferential loss of the first eluting stereoisomer. Interestingly, the extent of enantiomeric fractionation was similar among individuals within a SRKW pod, but significantly differed between pods, with the fractionation order (highest to lowest) being L > K > J. These results suggest stable carbon isotope analysis and enantiomeric fractionation can provide valuable information on the extent of biotransformation and assist with understanding the importance of trophic transfer in determining OH-PCB/PBDEs levels in biota.

Session Title

Session 1.2B: Contaminants in the Salish Sea: Sources, Movement, and Fate

Conference Track

Contaminants, Plastics, Microplastics, Toxicology & Stormwater

Conference Name

Salish Sea Ecosystem Conference (2020 : Online)

Document Type

Event

SSEC Identifier

2020_abstractID_5794

Start Date

21-4-2020 12:30 PM

End Date

21-4-2020 2:00 PM

Geographic Coverage

Salish Sea (B.C. and Wash.)

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.

Language

English

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Apr 21st, 12:30 PM Apr 21st, 2:00 PM

Assessing PCB and PBDE Biotransformation and trophic transfer Salish Sea food webs using stable carbon isotope analysis and enantiomeric fractionation

PCBs and PBDEs are ubiquitous contaminants that are biotransformed into hydroxylated (OH-) forms among other metabolites. OH-PCB/PBDEs are toxicologically important due to adverse effects on the thyroid system. Their environmental occurrence is complex because they are also formed through abiotic processes and for some OH-PBDEs, are marine natural products. Thus, the presence of PCB and PBDE congeners and their OH- derivatives in biota represent a mix of bioaccumulation and formation via biotransformation. We previously measured OH- PCB/PBDEs in shellfish and fish collected from Puget Sound (PS) and recently in blubber samples from Southern Resident Killer whales (SRKW). Comparison of shellfish and finfish results indicated finfish had higher levels of PCB/PBDEs but relatively low levels of the OH- derivatives. In contrast, bivalves had the highest levels of OH-PBDEs, while SRKW blubber contained high levels of naturally occurring PBDE derivatives but low levels of OH-PCB/PBDEs. Biotransformation can introduce carbon isotope effects causing a shift in the 13C/12C ratio (δ13C) of both the parent congener and OH- metabolites. In SRKW blubber, δ13C values for several PCB congeners, most notably PCB 18, were enriched in 13C relative to values in commercial Aroclor preparations. Select PCB congeners are chiral and industrially formed at racemic levels. Enantiomeric fractionation can occur during enzymatic OH-PCB formation. We observed the most pronounced fractionation with PCB-95 and PCB-149, with both Chinook salmon and SRKWs displaying preferential loss of the first eluting stereoisomer. Interestingly, the extent of enantiomeric fractionation was similar among individuals within a SRKW pod, but significantly differed between pods, with the fractionation order (highest to lowest) being L > K > J. These results suggest stable carbon isotope analysis and enantiomeric fractionation can provide valuable information on the extent of biotransformation and assist with understanding the importance of trophic transfer in determining OH-PCB/PBDEs levels in biota.