Proceedings of the 2007 Georgia Basin Puget Sound Research Conference
Panel 4E: PCBs and PBDEs in the Strait of Georgia Ecosystem
Chairs: Patrick Shaw and Peter Ross
Concerns about legacy contaminants in marine organisms in Puget Sound and the Strait of Georgia were focussed with the discovery of harmful levels of PCBs and elevated levels of PBDEs in resident killer whales. Since 2004 a multiagency effort has been underway, with funding from Environment Canada’s Georgia Basin Action Plan, to look at sources and fate of these contaminants in the Strait of Georgia, and making progress on modelling their movement in the environment.
Panel Members:
• Peter Ross, Fisheries and Oceans Canada
• Patrick Shaw, Environment, Canada
• Sophia Johannessen, Fisheries and Oceans Canada
• Robie Macdonald, Fisheries and Oceans Canada
• Mike Sanborne, UMA Engineering Ltd.
• Frank Gobas, Simon Fraser University
Towards an Understanding of Sources, Fate and Effects of PCBs and PBDEs in the Strait of Georgia Ecosystem
While PCB levels worldwide have declined with regulatory action and restriction in use, their legacy persists in biota within the Strait of Georgia and Puget Sound ecosystem. This was evident when it was discovered that the transboundary southern resident killer whales were “the most PCB-contaminated marine mammals in the world”. Subsequently, related studies have shown elevated levels of brominated flame retardants, polybrominated diphenyl ethers (PBDEs) in both local seals and killer whales. A 2004 SETAC workshop at Friday Harbor Marine Laboratory was convened to develop plans for a PCB modelling effort in Georgia basin and Puget Sound. Efforts since then have led to an increased understanding of PCBs and related contaminants in this region. Funding through the Georgia Basin Action Plan was made available in 2004 to study this issue in the Strait of Georgia. Partnering with multiple agencies, including Environment Canada, Fisheries and Oceans Canada, Simon Fraser University, Greater Vancouver Regional District and Capital Regional District, has generated new understanding of the loadings, history and fate of these contaminants in the Strait. This presentation will describe the genesis of the project and the activities presently underway.
The Long Reach of PCBs and PBDEs in the Georgia Basin: What are Blue Mussels Telling us?
Blue mussels (Mytilus sp.) are sessile, filter-feeding shellfish that sample the water column for environmental contaminants. We measured congener-specific PCBs and PBDEs in pooled mussel samples that were collected from 22 sites around the Georgia Basin. Sample sites were selected to 1) generate a spatial overview of contamination of the Georgia Basin by banned PCBs and by currently used PBDEs; and 2) comprise nearshore areas adjacent to major human use categories, including urban, agricultural, industrial, and remote locations. Total PCB concentrations in blue mussels range from 62 -- 5472 ng/g wet weight, and were dominated by the penta- and hexa- congeners. Total PBDE concentrations ranged from 32 -- 1234 ng/g wet weight, and were dominated by BDE-47 and BDE-99 (accounting for ~70% of the total PBDE concentrations). Principal components analysis (PCA) of the PCB and PBDE data revealed little inter-site variation, indicating that PCBs and PBDEs in the Georgia Basin may be largely influenced by broad regional signals rather than discreet point sources associated with particular activities. Deca-BDE was detected in 100% of tissue samples, indicating its bioavailability to the marine food web. Blue mussels are a keystone species in the marine foodweb of the Georgia Strait. Increasing concentrations in this organism of currently used Persistent Organic Pollutants (POPs), such as PBDEs, may be an important barometer of future trends in the contamination of higher trophic level organisms.
What are Harbour Seals Telling us About PCBs and PBDEs in the Georgia Basin Food Web?
As high trophic level, non-migratory mammals, harbour seals can provide an integrated measure of aquatic food web contamination by persistent organic pollutants (POPs) in coastal regions. Our spatial research indicates that Puget Sound harbour seals are highly contaminated with legacy’ PCBs compared to Georgia Basin seals. However, while the levels of unregulated PBDEs are higher in Puget Sound harbour seals compared to their Georgia Basin counterparts, differences are less pronounced than for the PCBs (2x higher for PBDEs compared to 7x higher for banned PCBs), likely reflecting widespread current use of PBDEs in both BC and Washington. Harbour seal food baskets’ indicate that PBDEs are now the 2nd and 3rd ranked POP by concentration in Puget Sound and Georgia Basin, respectively. Studies using stable carbon and nitrogen isotope ratios reveal that PBDEs are accumulating more slowly in the harbour seal food web, possibly reflecting current use, rapid contamination of shorter-lived organisms at the bottom of the food web, and/or the larger molecular size of PBDEs relative to PCBs, which may impede trophic transfer. However, the exponential increase of PBDEs in the region’s harbour seals over the past two decades underscores the emergence of a new conservation threat at the top of the coastal food web.
A Comparison of PCBs and PBDEs in Strait of Georgia Sediments
PCBs are relict contaminants in coastal British Columbia, while PBDEs are in increasing use. Both classes of chemical are highly particle active, so coastal sediments provide a useful archive of their historical and current deposition. In Strait of Georgia sediments, PBDE congeners 47, 99, 100 and 209 predominate, as has been observed in local biota. The concentration of BDE-209 is generally at least two orders of magnitude higher than that of the others. Using seven sediment cores collected in the Strait of Georgia, we demonstrate how local sediment accumulation and mixing rates affect the observed surface concentrations of these contaminants. We discuss local pathways of PCBs and PBDEs and compare their distribution, depositional history, and likely future trends.
Mass Balance Model of the Movement of Toxic Contaminants in the Georgia Basin Food-Web
As part of the Georgia Basin Modeling Initiative and related initiatives in BC to improve the management of toxic chemicals in Vancouver Harbour and the Straight of Georgia, we have conducted field studies and mass balance modeling studies to better understand the movement of potentially toxic contaminants in the Georgia Basin food-web. The need for the study arose as a result of observations that showed that concentrations of PCBs and other contaminants in Killer whales of the Georgia Basin are among the highest concentrations observed worldwide. It is expected that current concentrations of several contaminants are sufficiently high to cause adverse effects in certain upper-trophic level mammals. To address this problem and work towards solutions to reduce contaminant concentrations in the GB food-web we have developed a preliminary model of the food-web transfer of PCBs in the Georgia Basin food-web. The results show that current environmental quality criteria for the protection of aquatic life are not able to protect higher trophic level species from the adverse effects of PCBs and possibly other bioaccumulative contaminants. Model results are generally consistent with PCB measurements in free-ranging Harbour seals, although some variation in patterns and among sites is evident. A strategy for developing environmental quality criteria for bioaccumulative substances that are protective of upper trophic level species in the GB food-chain is proposed and the application of mass balance models to improve environmental quality of existing substances and chemicals of emerging concern are discussed.
A Preliminary Mass Balance for Selected PCB and PBDE Congeners in the Strait of Georgia
During the past several years, we have collected data for PCB and PBDE congeners from media in the Strait of Georgia including water, sediments and air. Additional measurements have been made of organochlorine composition in municipal effluent entering the Strait of Georgia. Using these data together with dated sediment core profiles, and building on a budget for sediment and organic carbon in the Strait of Georgia, we will present a first estimate of budgetary components for these contaminants with the intent of establishing the dominant regional controls for PCB/PBDE cycling within this system.