PBDE, contaminants of emerging concern accumulating in St. Lawrence food network
Based on recent results from joint research carried out by Environment and Climate Change Canada, the ministère de l’Environnement et de la Lutte contre les changements climatiques du Québec, and the ministère des Forêts, de la Faune et des Parcs du Québec, industrial chemicals, specifically, polybrominated diphenyl ethers (PBDEs), are accumulating in aquatic organisms in the St. Lawrence River.
PBDEs are a group of 209 chemical compounds (congeners) that are grouped in 10 bromination levels (from mono to deca) based on the number of bromine atoms they contain. These compounds were used as flame retardants in the manufacture of a wide variety of plastics and textiles. In Canada, the Prohibition of Certain Toxic Substances Regulations 2012 prohibits the import, manufacture, use, sale and offer for sale of PBDEs, and products containing them, with a limited number of exemptions. This prohibition has been in effect since December 23rd, 2016.
PBDEs have been detected in the environment and are persisting in aquatic ecosystems to the point that they are accumulating in the food web. These chemical substances are recognized as endocrine disruptors which act like hormones and can cause malformations and reproductive system problems in certain aquatic species. For more information on PBDEs, visit the website of Environment and Climate Change Canada.
The purpose of this fact sheet is to describe the bioaccumulation and biomagnification of PBDEs in the St. Lawrence food web. This document focuses solely on pentaBDE, for which 96% of the concentrations measured in Lake Saint-Pierre sediments in 2013 exceeded the Environment Canada quality guidelines. The other BDEs rarely exceed the corresponding guidelines.
PBDEs are hydrophobic and persistent chemicals that bind to suspended particles and are absorbed by living organisms primarily through their food.
Due to their chemical and physical properties, PBDEs bind strongly to suspended particles in the water originating from bank and bed erosion in the St. Lawrence and its tributaries, as well as from urban and industrial discharges. Some benthic organisms living in close contact with sediments, along with organisms that filter suspended sediments, are known to bioaccumulate toxic substances, including PBDEs.
Did you know?
Fine suspended particles that are present in the upper part of the water column near the surface are called suspended matter. This suspended material is generally captured by large filters during water filtration. Coarser suspended particles that concentrate in the lower part of the water column near the bottom sediment may also be called suspended sediment; they are usually captured by sediment traps placed on the bottom.
PBDEs are detected at all levels of the St. Lawrence food web
Since urban effluents are recognized as one of the main sources of PBDEs in the environment, samples of sediment, suspended sediment and suspended matter were collected both upstream and downstream from the discharge point of Montreal urban effluents in 2010, 2011 and 2012.
Prey fish (Yellow Perch, White Sucker and Round Goby), macroinvertebrates including Chironomids, Oligochaetes and Gammarids, Zebra Mussels and Crayfish, as well as bird's egg (Herring Gull, Ring-billed Gull and Great Blue Heron), were collected near the sediment sampling sites. The samples were analyzed in order to detect the presence of PBDEs (28 congeners) in the food web and to determine whether the wastewater discharges from Montreal City had an effect on the concentrations measured.
Figure 1. Location of the sampling sites in relation with ecosystem’s components
This map shows the sampling sites between Montreal and Contrecoeur. Seven red dots represent the sites where suspended matter, suspended sediment and surficial sediment have been sampled; thirteen orange dots represent where surficial sediment, fish and macroinvertebrates have been sampled; five blue dots represent where fish has been sampled, and one green dot represents where seagull eggs have been sampled. One star indicates the location of City of Montreal effluent.
Higher concentrations of pentaBDE in particles and suspended sediment of the St. Lawrence River
Based on the analysis results, the median concentrations of pentaBDE (BDE85, BDE99, BDE100, BDE119 and BDE126) were about three to four times higher in the suspended matter and suspended sediment samples collected downstream from the City of Montreal effluent discharge point than in the corresponding samples collected from upstream sites. The highest concentrations, reaching over 70 ng/g, were found in samples of suspended matter, whereas very low concentrations were found in bottom sediments, even near the effluent discharge point, because of the presence of currents that prevented sediment deposition. The difference between upstream and downstream concentrations of urban effluent and the decrease in concentrations with increasing distance from the discharge point indicates that wastewater discharges represent a significant local source of pentaBDE in the St. Lawrence River and that the river has a fairly strong dilution capacity.
Figure 2. Concentrations of pentaPBDE in suspended matter and sediments according to an upstream-downstream gradient
This graph illustrates the concentrations of pentaPBDE in the abiotic compartments, namely suspended matter, suspended sediment and sediment upstream and downstream of the City of Montreal’s wastewater outlet. The distance in kilometers relative to the City’s outlet appears from left to right on the X axis, and the concentrations of pentaPBDE in nanograms per gram dry weight are shown on the Y axis.
Upstream, concentrations of pentaPBDE range between 1 and 3 nanograms per gram dry weight. From 1 to 10 km downstream of the outlet, the median values are 8 and 5 nanograms per gram dry weight, respectively, for suspended matter and suspended sediment. In the sediment, the value reaches 1 nanogram of pentaPBDE per gram dry weight. The highest values were measured at 73 nanograms of pentaPBDE per gram dry weight in suspended matter. At 10 km and greater, the median values are 9 and 4 nanograms of pentaPBDE per gram dry weight, respectively, in suspended matter and suspended sediment.
Transfer of Contaminants in the Food Web
When persistent contaminants enter the aquatic environment, organisms that are exposed to them are likely to absorb and accumulate these contaminants through the process of bioaccumulation. The increase in the concentrations of a contaminant in organisms at successively higher tropic levels is called biomagnification. Benthic organisms— insects, worms and filter-feeding molluscs that live in or on sediment—bioaccumulate contaminants that are present in suspended sediments or in other invertebrates on which they feed. In turn, these benthic organisms are consumed by a variety of predators and so the contaminants are transferred to the next trophic level.
Higher concentrations of pentaBDE in fish collected near the effluent discharge point
The same observation can be made for the pentaBDE concentrations in fish: higher concentrations were found downstream from, compared to upstream from, the Montreal's effluent, and the concentrations decreased with increasing distance from the discharge point. The highest concentrations, about 20 ng/g, were found in Round Goby and Yellow Perch near the outfall. These two species showed the highest level of bioaccumulation, with a bioaccumulation level nearly five times higher than that for White Sucker near the effluent discharge point and extending over a distance of more than 10 km downstream. The median pentaBDE concentrations exceeded the quality guideline of 1 ng/g, which represents the probable adverse effects threshold for fish, over a distance extending more than 10 km downstream from the discharge point (EC, 2011 ; figure 3). Some of the differences in concentration of pentaBDE could be attributed to the respective composition of their food diet.
Figure 3. Concentrations of pentaPBDE in fish according to an upstream-downstream gradient
This graph illustrates the concentrations of pentaPBDE in three fish species , namely white sucker, yellow perch and round goby, from upstream to downstream of the City of Montreal’s wastewater outlet. The distance in kilometers relative to the City’s outlet appears from left to right on the X axis, and the concentrations of pentaPBDE in nanograms per gram dry weight are shown on the Y axis.
Upstream, median concentrations of pentaPBDE are lower than 1 for white sucker, and lower than 2 nanograms per gram dry weight for round goby and yellow perch. From 1 to 10 km downstream of the outlet, the median values are 2.5 for white sucker, 16 for round goby and 12.5 nanograms per gram dry weight for yellow perch. At 10 km and greater downstream of the outlet, the median values are 1 for white sucker, and 3.8 nanograms per gram dry weight for round goby and yellow perch.
Bioaccumulation and biomagnification of pentaBDE in the St. Lawrence food web
The pentaBDE concentrations measured in the St. Lawrence food web downstream from the Montreal effluent outfall showed that macroinvertebrates contained concentrations that were nearly double those found in bottom sediments. Some fish species such as Round Goby and Yellow Perch had pentaBDE levels that were more than 10 times higher than those found in macroinvertebrates. Predators such as gulls and the Great Blue Heron displayed pentaBDE concentrations 10 to 100 times greater than those found in macroinvertebrates. This rapid increase in pentaBDE concentrations from lower trophic levels to higher trophic levels is a good example of biomagnification.
Figure 4. Comparison of the levels of pentaPBDE in the various compartments of the environment
Note: pentaBDE concentrations are expressed in ng/g dry weight for the abiotic elements and in ng/g wet weight for biota.
This figure enables the comparison of pentaPBDE concentrations in different environmental compartments, namely suspended matter, suspended sediment, sediment, macroinvertebrates, fish and birds. The concentrations of pentaPBDE in nanograms per gram dry weight are shown on the Y axis.
Concentrations of pentaPBDE were 9 in suspended matter, 5 in suspended sediment, and 0.4 nanograms per gram dry weight in sediment. In invertebrates, concentrations of pentaPBDE were 2 for the benthos, 0.9 in zebra mussels, and 0.5 nanograms per gram dry weight in crayfish. In fish, concentrations were 0.9 in small white suckers, 8 in round goby, 7 in yellow perch, and 11 nanograms per gram dry weight in large white suckers. In birds, concentrations of pentaPBDE were 90 in great blue heron, 88 in ring-billed gull, and 500 nanograms per gram dry weigh in herring gull.
The concentrations measured in sediments occasionally exceeded the quality guideline (0.4 ng/g dry weight) established for the protection of aquatic organisms. However, owing to biomagnification the concentrations found in Round Goby and Yellow Perch were much higher than the guideline of 1 ng/g wet weight, which is the probable adverse effects threshold for fish. Similarly, the pentaBDE levels measured in gull eggs and Great Blue Heron eggs greatly exceeded the guideline value of 29 ng/g wet weight established for bird’s eggs (EC, 2011). A distinction must be made for the Ring-billed Gull. In urban areas, this opportunistic bird species may feed in locations away from the St. Lawrence, for example, at landfill sites, which are recognized as a significant source of PBDEs (figure 4).
This study shows that bioaccumulation and biomagnification of pentaBDE is occurring in part of the food web downstream from the Montreal urban effluent outfall. In that area, a rapid transfer can be seen in the concentrations of this contaminant at increasingly higher trophic concentrations, as represented by macroinvertebrates, fish and bird’s eggs, reaching concentrations that are markedly higher than the guidelines established for the protection of aquatic fauna.
In addition, this research shows that Round Goby, a species newly introduced into the St. Lawrence, tends to bioaccumulate as much pentaBDE as does Yellow Perch, a native species. This suggests that predatory fish that have switched to consuming Round Goby as a prey item instead of yellow perch may not cause changes in the level of transfer of pentaBDE within the food web.
Finally, the higher concentrations found in suspended matter and suspended sediments compared to bottom sediments suggest that the most heavily contamined fine particles are transported considerable distances and eventually settle out in calmer areas of the river such as Lake Saint-Pierre or the St. Lawrence estuary. It should be noted that pentaBDE concentrations in the water and sediments increased rapidly between 1990 and the mid-2000s (Pelletier and Rondeau, 2013), whereas the pentaBDE concentrations in Lake Saint-Pierre sediments decreased by about 30% (M. Pelletier, 2018).
Round Goby, a New Prey Species in the St. Lawrence
References and relevant links
Brodeur, P., Y. Reyjol, M. Mingelbier, T. Rivière and P. Dumont (2011). Prédation du gobie à taches noires par les poissons du Saint-Laurent : contrôle potentiel d’une espèce exotique ? Le naturaliste canadien, 135 (2): 4-11
Environment Canada. Polybrominated Diphenyl Ethers Regulations (SOR/2008-218)
Environment Canada. Polybrominated Diphenyl Ethers (PBDEs)
Environment Canada. Tracking Polybrominated Diphenyl Ethers (PBDE): New Chemical Contaminants in the Environment
Environment Canada (2011). Polybrominated Diphenyl Ethers in the Canadian Environment. Environmental Monitoring and Surveillance in Support of the Chemicals Management Plan. ISBN 978-1-100-19526-1. 10 p. http://publications.gc.ca/collections/collection_2012/ec/En14-53-2011-eng.pdf
Government of Canada. Chemical Substances, Polybrominated Diphenyl Ethers (PBDE) http://www.chemicalsubstanceschimiques.gc.ca/fact-fait/pbde-eng.php
Paradis, Y. 2018. Les espèces aquatiques envahissantes du fleuve Saint-Laurent : bilan de la situation en eau douce. Fiche d’information de la collection « Suivi de l’état du Saint-Laurent », Plan d’action Saint-Laurent, ISBN : 978-2-550-80012-5. 9 p. <media 3238>http://planstlaurent.qc.ca/fileadmin/publications/fiches_indicateurs/Francais/2018_Especes_aquatiques_envahissantes_fleuve_Saint-Laurent_bilan_situation_eau_douce.pdf</media>
Pelletier, M. 2018. État de la qualité des sédiments du lac Saint-Pierre en 2013. Fiche d’information de la collection « Suivi de l’état du Saint-Laurent », Plan d’action Saint-Laurent, ISBN : 978-0-660-25235-3. 8 p. <media 3460>http://planstlaurent.qc.ca/fileadmin/publications/fiches_indicateurs/Francais/2018_Etat_qualite_sediments_LSP_En2013_Final.pdf</media>
Pelletier, M. and M. Rondeau (2013). Polybrominated diphenyl ethers in the suspended matter and sediments of the St. Lawrence River. Fiche d’information de la collection « Suivi de l’état du Saint-Laurent », Plan d’action Saint-Laurent, ISBN 978-1-100-20752-0. 12 p. Read document
Reyjol, Y, P. Brodeur, Y. Mailhot, M. Mingelbier and P. Dumont (2010). Do native predators feed on non-native prey? The case of round goby in a fluvial piscivorous fish assemblage. Journal of Great Lakes Research Vol 36 (4): 618–624
Alain Armellin, Magella Pelletier et Louise Champoux
Environment and Climate Change Canada
Centre d’expertise en analyse environnementale du Québec, ministère de l’Environnement et de la Lutte contre les changements climatiques
Ministère des Forêts, de la Faune et des Parcs du Québec
We would like to acknowledge the financial contributions received from the Chemicals Management Plan, the Canadian Aquatic Biomonitoring Network and the St. Lawrence Action Plan 2011–2016. We would also like to extend our thanks to Nathalie Gratton of Environment and Climate Change Canada for her assistance with the preparation of this fact sheet.