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- Toxics in Aquatic Life
- Indicator
- Contaminants in Pacific herring
- Vital Sign Indicator
- Chemical Concentration Wet Weight (ng/g wet weight)
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By 2030, 95% of the samples gathered across Puget Sound habitats exhibit a declining trend of contaminant levels, or are below thresholds of concern for species or human health.
By 2050, 95% of the samples gathered across Puget Sound habitats exhibit contaminant levels below thresholds of concern for species or human health and show no increasing trends.
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Louisa Harding
- Contributing Partners
- Last Updated
- 05/23/2022 12:14:44
Pacific herring are small-bodied, schooling, pelagic (open water) fish that are important prey for virtually all large predatory fish and fish-eating seabirds, and most marine mammals in Puget Sound. They are a keystone species in the pelagic food web – without them Puget Sound’s ecosystem would look dramatically different. Persistent organic pollutants (POPs) build up in herring from the plankton they consume, and these contaminants are further magnified up the food chain in their predators.
It is difficult to measure contaminants directly in many larger pelagic predators higher up in the food chain, including seals, dolphins, killer whales, and fish-eating seabirds. Herring provide a more practical approach for measuring contaminants in the pelagic food web because they are abundant and relatively easy to capture and process in the laboratory. Moreover, they integrate contaminant conditions in the food web over a relatively short period of time (2-3 years), which means that management actions designed to reduce POP loadings to the ecosystem should be observed quickly.
- The contaminants in Pacific herring indicator failed to meet the recovery target (see target description) because PCBs continued to exceed an adverse fish health effects threshold in two of the five monitored stocks. For detailed results, see the Interpretation of Results section.
- PCBs remained high in the two stocks (Port Orchard/Madison and Squaxin Pass) from the more urbanized Central and South Basins of Puget Sound. Virtually all herring samples from those stocks have exceeded the fish health threshold over the past 20 years. These high PCB levels warrant continued concern for several reasons:
- PCBs impair herring health and can reduce their survival.
- Reduced herring survival can limit food supply to the numerous predators that rely on them.
- PCBs in herring are transferred up the food chain to their predators, including Chinook salmon, and ultimately to Southern Resident killer whales (SRKW) who feed on salmon. This results in PCBs levels in both SRKW and Chinook salmon high enough to impair their recovery.
- PCBs are low (with 95% of fish below the health effects threshold) in Quilcene Bay, Semiahmoo Bay and Cherry Point herring stocks. Virtually all herring have been below the fish health threshold from 2002-2018 in Semiahmoo Bay, and since 2014 in Quilcene Bay. Only a few samples of herring from the Cherry Point stock have exceeded the threshold since 2012.
- PBDEs are low (with 95% of fish below the health effects threshold) in all five herring stocks and they continue to decline or remain stable everywhere, suggesting remediation actions have been effective at mitigating these contaminants.
- Monitoring Program
Washington State Department of Fish and Wildlife, Toxics Biological Observation System
- Data Source
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Washington State Department of Fish and Wildlife, Toxics Biological Observation System (unpublished data)
This update presents the most current contaminant results for five herring stocks selected to cover a wide area of Puget Sound from its Southern Basin (Squaxin Pass), into its Central Basin (Port Orchard/Madison), northward to the Strait of Georgia (Semiahmoo Bay and Cherry Point), and westward to Hood Canal (Quilcene Bay). As used herein, the term “stock” refers to a biologically meaningful unit of herring population recognized by the Washington Department of Fish and Wildlife (WDFW). Stocks are defined by the herring’s predictable and consistent use of specific spawning habitats. WDFW currently recognizes 21 spawning stocks in Puget Sound and the Strait of Juan de Fuca. Herring are sampled during their spawning season (January to June, depending on stock) using either gill (tangle) nets targeting fish on nearshore spawning grounds, or midwater trawls targeting predictable pre-spawning aggregations offshore of spawning grounds.
PCBs and PBDEs are measured directly in the herring's whole body (see West et al., 2017 for detailed analysis methods). The resulting values reflect the amount of contaminants in the herring themselves, and allows an assessment of how much toxic contaminants predators (or humans) may be exposed to when consuming herring.
PAHs are measured differently than PCBs and PBDEs. Unlike PCBs and PBDEs which build up in fish tissues over time, PAHs are metabolized, or broken down inside the body of the fish. Thus, the break-down products of PAHs (metabolites) in the herring are what is measured. A new method for analyzing these metabolites is underway. PAH results will be reported in the next Vital Sign indicator update.
To determine whether the contaminants are likely to harm fish, the contaminant concentrations in fish tissues are compared to adverse fish health effects thresholds. These thresholds are typically a numerical value established experimentally and published in the scientific literature (described below). They are an agreed-upon level, above which fish health would be predicted to be harmed by exposure to the chemicals.
The Toxics in Fish recovery targets are based on reducing contaminant levels to recover health in the majority of fish, defined as “95% of samples” for each indicator species and population. This statistic is calculated as the 95th percentile for chemical concentrations for each stock in each year. The target is met for these chemicals when the 95th percentile for chemical concentrations in the current year is below the adverse fish health effects threshold. Progress towards meeting recovery goals is measured with time trends analysis (when sufficient data exist) to evaluate whether levels are stable, increasing, or decreasing.
Summary statistics for each stock and year are presented graphically using box plots, which provide:
- the median persistent organic pollutant (POP) concentration, or the level where half of the concentrations were above, and half below, also called the 50th percentile. This is shown as a horizontal line inside the box.
- Box ends, also shown as horizontal lines, indicate the 25th (bottom line) and 75th (top line) percentiles.
- Diamonds indicate 95th (top) and 5th (bottom) percentiles.
- Bars are color-coded red or green to indicate whether the majority of the samples, as estimated by the 95th percentile (the upper diamond), fell below the fish health threshold (green) or above (red) for a particular year.
- The fish health threshold is shown in each plot as a horizontal dashed line. If herring contain either PCBs or PBDEs above this level, we predict health impairments in those fish that likely affect their health and survivability. Current levels are 2,400 ng/g lipid total PCBs for herring (Meador et al. 2002) and 470 ng/g lipid for PBDEs, (calculated as the sum of PBDE-47 and PBDE-99) based on interpretations of studies by Arkoosh et al. (2010, 2013 and 2018) described in O’Neill et al. (2015).
- PCB and PBDE levels are expressed on a lipid-basis, with a lipid concentration set to 3%. This adjustment normalizes highly variable lipid levels herring exhibit throughout the sampling period (January through June) to a uniformly low lipid level regardless of when they were sampled in the year. This lipid level was selected based on levels observed in herring towards the end of winter, which is meant to represent body conditions when POP toxicity is likely greatest.
Four of the five monitored herring stocks (Squaxin Pass, Port Orchard/Madison, Semiahmoo Bay, and Cherry Point) had sufficient data to evaluate time trends in PCBs and PBDEs.
Multiple linear quantile regression models (Cade and Noon 2003) were used to help interpret POP time trends. Trend analyses were focused on the upper boundary of the distribution of contaminant levels in each year (95th percentile), rather than an estimate of central tendency (e.g., the mean, or median). Using this method, we determined whether the highest values in each year were declining, increasing, or remaining unchanged. All regressions were conducted on log10-transformed POP data, which were then back-transformed for plotting.
The quantile regressions provide statistics to help determine whether the 95th percentile concentration of POPs is increasing (a positive slope) or decreasing (a negative slope), whether the modeled trend is statistically significant (i.e., how confidently it can be distinguished from random events), and how strong the trend is (the annual rate of change). Quantile regression models with slope coefficient probability values <0.05 were considered statistically significant, or distinguishable from random events. Plotted trend lines (solid black lines) predict fish-length-adjusted POP concentrations at the 95th percentile. The gray area around statistically significant trend lines represents the 95% confidence interval for the slope parameter calculated in the quantile regression. Confidence in a determination of whether a stock has fully reached its recovery target is greatest when the upper confidence boundary for the 95th percentile falls below the adverse fish health effects threshold.
Fish size (measured as standard length) was included in regressions as a statistical covariate to help account for variability in the size of sampled fish (length was excluded from the model if it was not a significant explanatory factor). The study design for herring targets a set fish size to sample three-year-old fish, one of the most abundant age classes of herring in Puget Sound. This is meant to minimize variability in age and trophic level, increasing the probability of identifying a significant time trend, if one exists.
- Critical Definitions
- Persistent Organic Pollutant (POP): a type of organic chemical that is toxic, and resistant to environmental and biological degradation, such that they persist in the environment longer than other types of contaminants. POPs typically accumulate in organisms and once in the food web, tend to remain there and increase in concentration (biomagnify) up the food chain from prey to predators.
- Polychlorinated biphenyls (PCBs): are a group of synthetic (man-made) chemicals consisting of 209 compounds, or congeners, each containing a unique number and position of chlorine atoms attached to two phenyl (aromatic) rings. These typically oily compounds were designed for various industrial and residential products and uses (transformers, cable insulation, caulking and plastics) and industrial products typically consist of complex mixtures of congeners. PCBs were largely banned in the US by 1979, but they are still found in materials produced before the ban, as unintentional byproducts of manufacturing, and in small amounts (<50 parts per million), still allowed in newly manufactured products. PCBs are classified as a Persistent Organic Pollutant (POP) because they are resistant to most forms of degradation, and once released to the environment, they can bioaccumulate in organisms and cause adverse health impacts in wildlife and humans.
- Polybrominated diphenyl ethers (PBDEs): are a group of synthetic (man-made) chemicals consisting of 209 compounds, or congeners (similar to PCBs), although each containing a unique number and position of bromine atoms surrounding two phenyl-ether rings. PBDEs were designed primarily as flame-retardants to prevent or slow the spread of fire in products ranging from electronics and furniture to clothing. In 2008, Washington state banned the sale of select PBDE mixtures, however they can still be found in materials produced before the ban. PBDEs are classified as a POP, because once released to the environment are resistant to degradation, bioaccumulate in organisms and have adverse health impacts in wildlife and humans.
The current status of this indicator is reported as “below 2020 target”, because at least one chemical (PCBs) continues to exceed fish health thresholds in two herring stocks, Squaxin Pass and Port Orchard/Madison (red box plots below). All stocks have reached the PBDE recovery target.
Evaluation of the long-term PCB and PBDE time trends in herring provides insight into progress towards reaching and maintaining recovery targets. The following graphs show contaminant concentrations in four herring stocks over the past 20 years, in the form of box plots through time (there is insufficient data to evaluate time trends in the Quilcene Bay stock). Each box plot shows several calculated summary values or statistics for PCBs or PBDEs, and additional elements described in the Methods section.
PCBs in herring from the Port Orchard/Madison and Squaxin Pass stocks remain high, with levels exceeding the fish health threshold in virtually all herring from both stocks in all years from 1999 to the present. Moreover, there is no statistically significant evidence of a declining PCB trend in the highest measured concentrations for these two stocks (no trend lines are shown here).
PCBs in both Squaxin Pass and Port Orchard/Port Madison stocks from the most recent sampling (2016 and 2018) were lower than previous years, possibly indicating some decline, however these low values were insufficient to conclude a statistically significant declining PCB trend overall. Herring stocks in the Central and South Basins were unusual in 2016/18 for other reasons as well. WDFW’s Forage Fish Team reported record low spawning biomass for the South and Central Basin stocks (including Squaxin Pass and Port Orchard/Port Madison) in these years. Because of this, it was difficult to find and sample these stocks in 2016/18. Thus, there is some uncertainty about whether the herring sampled in these years adequately represent the same populations of fish as in previous years.
PCBs remain low in the two stocks from the Strait of Georgia and although a slight decline is suggested from the box plots, the trends were not statistically significant, with probability values for the time factor just exceeding the 0.05 cutoff (0.057 and 0.069 for Cherry Point and Semiahmoo Bay). PCBs in herring from these two Strait of Georgia stocks have only occasionally exceeded the fish adverse health effects threshold over the past 20 years. PCBs can be considered low enough to pose low health risks in the majority of fish in these stocks (using the current adverse health effects threshold), and relatively stable.
PBDEs in herring showed a similar geographic distribution pattern as PCBs, with greatest levels in herring from the South and Central basins. Although there is some uncertainty regarding the comparability of 2016 and 2018 herring samples with previous years (see PCB discussion above), the most current PBDE status (2018) indicates greater than 95% of samples from all stocks fell below the PBDE fish health threshold (shown in green). This achieves the recovery target for this chemical group in this species. Moreover, the highest PBDE levels (i.e., 95th percentile) appear to be declining consistently and steadily in fish from at least three of these four stocks with long-term data, even with the uncertain 2016 and 2018 data removed. Hence, unlike PCBs, PBDEs appear to be declining steadily in most herring stocks, and most stocks have met the recovery target for this chemical group.
Although the PBDE results illustrate ongoing recovery regarding declines in those chemicals, the PCB results point to long term, high PCB contamination of Puget Sound’s pelagic food web. This is especially true for the more densely populated Central and South Basins and raises a red flag for focusing attentions there to resolve this problem. Because PCB levels in the Strait of Georgia stocks have never substantially exceeded the threshold, and recent levels remain low there, actions to mitigate PCB sources in these areas are less urgently needed than in the Central and South basins.
An evaluation of the pathways of PCBs from their terrestrial sources to aquatic habitats may help to focus or prioritize remediation efforts. Osterberg and Pelletier (2015) reported stormwater (“surface runoff" in their Table 3) as the greatest loading pathway for PCBs to the Central and South Basins, with lesser amounts attributable to wastewater from publicly-owned treatment works (POTWs) and to atmospheric deposition. Stormwater was the dominant loading pathway for PCBs in Elliott Bay and Commencement Bay, two highly urbanized embayments in the Central Basin, both containing PCB Superfund sites. With stormwater loading of PCBs 13 to 20 times greater than either atmospheric deposition or POTWs in these PCB-contaminated bays, a focus on stormwater pathway overall, and Superfund sites in particular, seems appropriate.
Pacific herring provide a long-term and Sound-wide perspective on PCBs in Puget Sound’s pelagic food web. Extensive reporting of PCBs in other pelagic species provides an even broader context, especially regarding how PCBs move through the pelagic food web to apex predators. West et al. (2011a) reported high levels of PCBs in Pacific krill from Elliott Bay, sampled near the Lower Duwamish Waterway Superfund site. Krill and similar species are a primary prey for herring, and the biomagnification of PCBs from krill to herring is likely a primary pathway for PCBs entering the pelagic food web via plankton. PCB distribution patterns in Chinook salmon (O’Neill and West 2009) and adult gadoid codfishes (Pacific hake and walleye pollock; West et al., 2011b), all herring predators, provide a weight of evidence pointing to the Central and South Basins as hot spots for PCBs in the pelagic food web.
The pelagic food web in the Central and South Basins of Puget Sound continues to be contaminated at levels of concern for both herring health, and for transfer of these persistent chemicals up the food chain to Chinook salmon, fish-eating seabirds, and marine mammals including Southern Resident killer whales. Washington State’s Department of Health recommends meal limits of Chinook salmon and other species in Puget Sound to protect seafood consumers’ health from these chemicals. PCB contamination also raises concerns regarding inequitable impacts of these chemicals on local communities who consume more fish from these contaminated areas than other communities, especially including indigenous communities (Donatuto et al. 2011), and Asian Americans and Pacific Islanders (Sechena et al., 2003). These concepts are central to several indicators of Vibrant Human Quality of Life Vital Signs, including Cultural Wellbeing, Sense of Place, and Economic Vitality.
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The wide-ranging nature of herring, combined with PCB contamination of other similar pelagic fishes, their prey and their predators illustrate significant, pervasive PCB contamination of Puget Sound's pelagic food web, which has not declined significantly over the past 20 years. This is likely related to not only the persistent nature of these chemicals, but also continued PCB inputs to Puget Sound waters from external sources.
The manufacture and sale of PCBs in the US and many other countries was largely banned in 1979 and a number of aquatic ecosystems world-wide have exhibited some PCB declines in biota since that time. Although PCB trends in Puget Sound biota are unknown during the first twenty years after the ban (1979 through 1999, prior to monitoring), it seems likely that if sources were truly controlled in Puget Sound’s Central Basin, levels in Pacific herring should have declined in the most recent twenty years. The absence of an observable decline in high PCBs in herring over the past 20 years, and the significant and far-reaching consequences of this contamination raise a red flag for focusing attention on reducing PCB inputs to the Puget Sound ecosystem. Scientists from WDFW, the University of Washington, and Batelle’s Pacific Northwest National Laboratory are currently investigating potential PCB routes to the pelagic food web, focusing on plankton near urban areas and Superfund sites, with field sampling scheduled for the fall of 2021.
Conversely, the steady decline of the highest PBDE levels in most monitored herring stocks in marine waters in both urbanized and less urbanized basins suggests management actions to reduce inputs of these chemicals to Puget Sound have been effective. This not only highlights the value of effectiveness monitoring for evaluating the efficacy of pollution mitigation actions, but also prompts questions about which actions have been responsible for the recovery.
Targeted PBDE actions in the past 20 years include both statutory and voluntary PBDE controls on production and use of these chemicals in Washington State. These may have resulted in reducing PBDEs at their source, thereby reducing PBDEs in their primary pathways to Puget Sound. Changes in PBDE pathways may have also occurred during this period. Using data gathered in the early 2000s, Osterberg and Pelletier (2015) identified publicly-owned treatment works (POTWs) as the primary pathway through which PBDEs move from their terrestrial sources to Puget Sound waters. Kim et al. (2013) reported a strong correlation between PBDEs and total suspended solids (TSS) from a review of 20 Canadian POTWs, which prompts questions about whether changes in treated wastewater effluent in Puget Sound during this period (reducing TSS, for example) may have helped to reduce the mass of PBDEs entering Puget Sound.
Although PBDEs have declined broadly in Puget Sound’s pelagic marine food web over the past two decades, PBDE contamination at levels of concern has been reported in seaward-migrating juvenile Chinook salmon in lower-river estuarine habitats of the Snohomish and Nisqually Rivers (see the contaminants in juvenile Chinook salmon Vital Sign indicator). O’Neill et al. (2020) identified POTW discharges in the Snohomish river as the likely source of PBDEs to juvenile Chinook in that system. These results suggest that timing and proximity of discharges with salmon migration in a restricted water body (river) may be key factors in the exposure of fish to chemicals discharged by POTWs.
The disparate PBDE results between herring in marine waters and juvenile Chinook salmon in river estuaries exemplify the importance of a diversity of indicator species covering different habitats to fully understand the impact of chemical contamination in the Puget Sound ecosystem.
Arkoosh, M. R., D. Boylen, J. Dietrich, B. F. Anulacion, G. M. Ylitalo, C. F. Bravo, L. L. Johnson, F. J. Loge and T. K. Collier. 2010. Disease susceptibility of salmon exposed to polybrominated diphenyl ethers (PBDEs). Aquatic Toxicology 98(1): 51-9. https://doi.org/10.1016/j.aquatox.2010.01.013
Arkoosh, M. R., J. Dietrich, G. M. Ylitalo, L. L. Johnson, and S. M. O’Neill. 2013. Polybrominated diphenyl ethers (PBDEs) and Chinook salmon health. U.S. Department of Commerce. National Oceanic and Atmospheric Association, National Marine Fisheries Service, Northwest Fisheries Science Center, Newport, Oregon. 49 pp. plus Appendices.
Arkoosh, Mary R., Ahna L. Van Gaest, Stacy A. Strickland, Greg P. Hutchinson, Alex B. Krupkin, Mary Beth Rew Hicks and Joseph P. Dietrich. 2018. Dietary exposure to a binary mixture of polybrominated diphenyl ethers alters innate immunity and disease susceptibility in juvenile Chinook salmon (Oncorhynchus tshawytscha). Ecotoxicology and Environmental Safety 163: 96-103. https://doi.org/10.1016/j.ecoenv.2018.07.052
Cade, B. S. and B. R. Noon. 2003. A gentle introduction to quantile regression for ecologists. Frontiers in Ecology and the Environment. 1(8): 412-420.
Donatuto, J. L., T.A. Satterfield, and R. Gregory. 2011. Poisoning the body to nourish the soul: Prioritising health risks and impacts in a Native American community. Health, Risk & Society 13(2): 103-127.
Kim, M., et al. 2013. Parameters affecting the occurrence and removal of polybrominated diphenyl ethers in twenty Canadian wastewater treatment plants. Water Research 47(7): 2213-2221.
Meador, J. P., T. K. Collier and J. E. Stein. 2002. Use of tissue and sediment-based threshold concentrations of polychlorinated biphenyls (PCBs) to protect juvenile salmonids listed under the U.S. endangered species act. Aquatic Conservation: Marine and Freshwater Ecosystems 12: 493-516. https://doi.org/10.1002/aqc.523
O'Neill, S. M. and J. E. West. 2009. Marine distribution, life history traits, and the accumulation of polychlorinated biphenyls in Chinook salmon from Puget Sound, Washington. Transactions of the American Fisheries Society 138(3): 616-632.
O'Neill, S. M., A. J. Carey, J. A. Lanksbury, L. A. Niewolny, G. Ylitalo, L. Johnson and J. E. West. 2015. Toxic contaminants in juvenile chinook salmon (Oncorhynchus tshawytscha) migrating through estuary, nearshore and offshore habitats of Puget Sound. Olympia, WA. Washington Department of Fish and Wildlife. Technical Report FPT 16-02. 132 pp.
O'Neill, S.M., A.J. Carey, L.B. Harding, J.E. West, G.M. Ylitalo and J.W. Chamberlin 2020. Chemical tracers guide identification of the location and source of persistent organic pollutants in juvenile Chinook salmon (Oncorhynchus tshawytscha), migrating seaward through an estuary with multiple contaminant inputs. Science of The Total Environment 712: 135516.
Osterberg, D. J. and G. Pelletier. 2015. Puget Sound Regional Toxics Model: Evaluation of PCBs, PBDEs, PAHs, Copper, Lead and Zinc. Washington Department of Ecology, Publication No. 15-03-025.
Sechena, R., S. Liao, R. Lorenzana, C. Nakano, N. Polissar, and R. Fenske. 2003. Asian American and Pacific Islander seafood consumption — a community-based study in King County, Washington. Journal of Exposure Science & Environmental Epidemiology 13(4): 256-266.
West, J.E., J.A. Lanksbury, and S.M. O’Neill. 2011a. Persistent organic pollutants in marine plankton from Puget Sound, Washington Department of Ecology Publication 11-10-002. 70 pp.
West, J.E., J.A. Lanksbury, S.M. O’Neill, and A. Marshall. 2011b. Persistent, bioaccumulative and toxic contaminants in pelagic marine fish species from Puget Sound. Olympia Washington, Washington Department of Ecology Publication 11-10-00.. 59 pp.
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