Contaminants in marine organisms

Photo: Trine Lise Sviggum Helgerud, NPI.

Human activity - data from 2020
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Levels of contaminants in fish and crustaceans from the Barents Sea are in general relatively low and below maximum levels set for food safety. For most substances, concentrations are stable or slightly decreasing.

Contaminantns in marine organisms

IMR conducts regular monitoring of chemical contaminants in biota through two different programs. 1) A three-year monitoring program designed to monitor the level of pollution in the Barents Sea, last updated with sampling in 2018.

2) An annual monitoring program with focus on seafood safety and pollution levels in indicator species, updated with new data from 2020.

In program 1, levels of certain organic contaminants (PCB, chlorinated pesticides and PBDEs) are analysed mainly in liver of fish. The exact species sampled varies from year to year, but some species have been sampled repeatedly in three year cycles and temporal data exist for Greenland halibut (Rheinhardtius hippoglossoides), long rough dab (Hippoglossoides platessoides), haddock (Melanogrammus aeglefinus), capelin (Mallotus villosus), polar cod (Boreogadus saida), saithe (Pollachius virens), herring (Clupea harengus), cod (Gadus morhua) and golden redfish (Sebastes norvegicus). The sampling programme is designed to monitor pollution levels over time. Samples are mainly taken on the ecosystem cruise in summer/early fall.

In program 2, levels of metals including As, Cd, Hg and Pb are analysed in fillet and liver of Atlantic cod, whole capelin and polar cod as well as whole and peeled boiled shrimp (Pandalus borealis). Levels of persistent organic pollutants (POPs) are analysed in liver of cod, whole capelin and polar cod and whole boiled shrimp, and a few samples of cod fillet have also been analysed. The POPs include dioxins and dioxin-like PCBs, non-dioxinlike PCBs (PCB6, PCB7), organochlorine pesticides, brominated flame retardants (PBDEs, HBCD and TBBP-A), per- and polyfluoralkyl substances (PFAS) and PAHs. The monitoring programme is designed to document levels of contaminants with regards to food safety, while also gaining information on pollution levels by analysing indicator organisms representing varying trophic levels and niches. Samples are mainly taken on the winter cruise in January-March.

In addition to these regular monitoring programmes, some species have been sampled and analysed as a part of special surveys (Nilsen et al. 2020; Frantzen and Maage 2016; Julshamn et al. 2015). Also, contaminants in saithe (Pollachius virens) and Greenland halibut are monitored annually.

In both program 1 and 2, where temporal data exist, samples are not taken at fixed positions or at fixed fish size, so temporal trends must be interpreted with caution.

Analyses are performed with accredited analytical methods according to ISO 17025.

Since 1986, scientists of the Polar Branch of VNIRO have been sampling fish annually for analysis of contaminants. Samples of some species were collected over a long period of time, whereas sampling of other species was carried out occasionally. Muscle and liver of different fish species are analyzed for metals including Hg, As, Cd, Pb, Cr, Ni, Co, polyaromatic hydrocarbons (PAH), alkanes and chlorinated pesticides including DDT, HCB, HCH and chlordane.

For fish species that are regularly monitored, there are available time series that describe variations in the content of pollutants over time. Among species monitored regularly are Atlantic cod, Greenland halibut and plaice (Pleuronectes platessa).

Levels of contaminants in muscle of fish and crustaceans

In general, levels of contaminants in fillet of fish and muscle of crustaceans from the Barents Sea are very low and below EU and Norway’s maximum levels for food safety for substances where these exist (Hg, Cd, Pb, sum dioxins and dioxin-like PCBs and sum PCB6) (Figure 3.10.9.1-4; EU, 2020).

Arsenic levels in some of the fish species and all crustaceans were relatively high (Figure 3.10.9.1A; Figure 3.10.9.2C). In Norway and EU, there is no maximum level for arsenic, but Russia has a maximum level of 5 mg/kg wet weight. For cod, Greenland halibut, Atlantic wolfish and spotted wolffish as well as shrimp, red king crab and snow crab, mean arsenic concentrations were above this limit. The levels of arsenic in the snow crab and shrimp were particularly high (Figure 3.10.9.2C).

However, arsenic present in fish and crustacean muscle is usually arsenobetain, which has very low toxicity (EFSA 2009). The most toxic species of arsenic is inorganic arsenic. A large number of fish samples from Norwegian sea areas, including cod and Greenland halibut, were previously analysed for total and inorganic arsenic (Julshamn et al. 2012). Even samples with very high total arsenic concentrations had very low levels of inorganic arsenic (

Figure 3.10.9.1 Concentrations of A) Arsenic (As, mg/kg wet weight) and B) mercury (Hg, mg/kg wet weight) in muscle of cod (2019-2020, n = 100), saithe (2019-2020, n = 99), haddock (2014, n=40), tusk (2014, n=160), Greenland halibut (2019-2020, n= 249), golden redfish (2018, n = 50), beaked redfish (2018, n = 249), Atlantic wolffish (2014, n = 29), spotted wolffish (2014, n = 27) and jelly wolffish (2014, n = 12). Mean, minimum and maximum values are shown. Red lines indicate maximum allowable levels set for food safety. Figure 3.10.9.1 Concentrations of A) Arsenic (As, mg/kg wet weight) and B) mercury (Hg, mg/kg wet weight) in muscle of cod (2019-2020, n = 100), saithe (2019-2020, n = 99), haddock (2014, n=40), tusk (2014, n=160), Greenland halibut (2019-2020, n= 249), golden redfish (2018, n = 50), beaked redfish (2018, n = 249), Atlantic wolffish (2014, n = 29), spotted wolffish (2014, n = 27) and jelly wolffish (2014, n = 12). Mean, minimum and maximum values are shown. Red lines indicate maximum allowable levels set for food safety.

Figur 3.10.9.2 Concentrations of A) mercury (Hg, mg/kg wet weight), B) cadmium (Cd, mg/kg wet weight) and C) arsenic (As, mg/kg wet weight) in muscle of red king crab (Paralithodes camtchaticus, 2012), snow crab (Chionoecetes opilio, 2014 + 2016) and shrimp (Pandalus borealis, boiled, 2016-2020). Mean, minimum and maximum values are shown. Red lines indicate maximum allowable levels set for food safety. *Composite samples. Figur 3.10.9.2 Concentrations of A) mercury (Hg, mg/kg wet weight), B) cadmium (Cd, mg/kg wet weight) and C) arsenic (As, mg/kg wet weight) in muscle of red king crab (Paralithodes camtchaticus, 2012), snow crab (Chionoecetes opilio, 2014 + 2016) and shrimp (Pandalus borealis, boiled, 2016-2020). Mean, minimum and maximum values are shown. Red lines indicate maximum allowable levels set for food safety. *Composite samples.

The levels of mercury in muscle of fish from the Barents Sea (Figure 3.10.9.1B) are generally lower than in the same species sampled in the Norwegian Sea and the North Sea (Azad et al. 2019; miljostatus.no). Data from VNIRO also show low concentrations of mercury in muscle of Barents Sea fish, well below maximum levels set for food safety.

The level of cadmium was considerably higher in shrimp than in both crab species (Figure 3.10.9.2B). Cadmium levels in shrimp from the Barents Sea are higher than the levels in shrimp sampled in Norwegian sea areas further south. This corresponds well with findings from other studies of increasing cadmium levels in crustaceans from south to north (Wiech et al. 2020; Zauke et al. 1996, Zauke and Schmalenbach 2006). It likely has natural causes. However, a good explanation has so far not been found.

Concentrations of fat soluble organic contaminants, such as for instance dioxins and dioxin-like PCBs or non-dioxinlike PCBs (PCB6), are in general very low in muscle of fish and crustaceans from the Barents Sea (Figure 3.10.9.3; Figure 3.10.9.4). The concentrations are higher in fish species that store a larger portion of their lipids in the fillet, such as Greenland halibut, than in lean fish species that mainly store lipids in the liver. The concentration in boiled and peeled shrimp was on average similar as for cod muscle, and red king crab and snow crab had even lower levels of these substances.

Figure 3.10.9.3 Concentrations of A) Sum of dioxins and dioxin-like (dl-) PCBs (ng TEQ/kg weight) and B) sum PCB6 (µg/kg wet weight) in muscle of cod (2019-2020, n = 25), saithe (2019-2020, n = 16), haddock (2014, n = 7*), tusk (2014+2016; n = 10*), Greenland halibut (2019, n = 100), golden redfish (2018, n = 49), beaked redfish (2018, n = 347), Atlantic wolffish (2014, n = 6*), spotted wolffish (2014, n = 4*) and jelly wolffish (2014, n = 2*). Mean, minimum and maximum values are shown. Red lines indicate maximum allowable levels set for food safety in EU and Norway. For non-dioxinlike PCBs, maximum level in EU and Norway applies to the sum PCB6. *Composite samples analysed. Figure 3.10.9.3 Concentrations of A) Sum of dioxins and dioxin-like (dl-) PCBs (ng TEQ/kg weight) and B) sum PCB6 (µg/kg wet weight) in muscle of cod (2019-2020, n = 25), saithe (2019-2020, n = 16), haddock (2014, n = 7*), tusk (2014+2016; n = 10*), Greenland halibut (2019, n = 100), golden redfish (2018, n = 49), beaked redfish (2018, n = 347), Atlantic wolffish (2014, n = 6*), spotted wolffish (2014, n = 4*) and jelly wolffish (2014, n = 2*). Mean, minimum and maximum values are shown. Red lines indicate maximum allowable levels set for food safety in EU and Norway. For non-dioxinlike PCBs, maximum level in EU and Norway applies to the sum PCB6. *Composite samples analysed.

Figure 3.10.9.4 Concentrations of A) sum of dioxins and dioxin-like (dl-) PCBs (ng TEQ/kg weight) and B) sum PCB6 (µg/kg wet weight) in composite muscle samples of red king crab (2012, n = 29), snow crab (2014, n = 9*) and shrimp (2016-2020, n = 15* cooked and peeled). Mean, minimum and maximum values are shown. *Composite samples analysed. Figure 3.10.9.4 Concentrations of A) sum of dioxins and dioxin-like (dl-) PCBs (ng TEQ/kg weight) and B) sum PCB6 (µg/kg wet weight) in composite muscle samples of red king crab (2012, n = 29), snow crab (2014, n = 9*) and shrimp (2016-2020, n = 15* cooked and peeled). Mean, minimum and maximum values are shown. *Composite samples analysed.

Temporal trends of contaminant levels in fish muscle

Over the last decade, the levels of some pollutants in fish have decreased, while the levels of others remain relatively stable. Studies on the concentrations of metals in 2009-2020 by the Polar Branch of VNIRO indicate a stable long-term decreasing trend in the contents of chromium and nickel in muscle of Greenland halibut, with correlation coefficients of 0.77 (R2 = 0.60) and 0.82 (R2 = 0.67), respectively (Figure 3.10.9.5). A similar trend was observed in respect to the contents of these metals in muscle of cod (Figure 3.10.9.6), plaice (Figure 3.10.9.7) and haddock (not shown). A decreasing trend, albeit less pronounced, also occurred for other examined metals such as cobalt, copper and lead (Figure 3.10.9.5-7). This was not caused by the age (length) of the fish, because fish of commercial size predominated in analyzed samples; however, the examined specimens were not overly large. No similar trend occurred in fish liver, probably because the contents of chromium and nickel in the liver of examined fish was 3-5 times higher than in their muscles, being little subject to fluctuations in the course of their lifetimes as the liver is an uptake organ.

The decreasing levels of some metals in fish muscle may indicate a decrease in the overall pollution of the Barents Sea by some heavy metals in the last decade. This conclusion is in agreement with the data on the pollution of the Barents Sea waters in the same period (Novikov and Draganov 2017, 2018). Additionally, the presented trend for cod may also be caused by shifts of its feeding areas northwards to the Arctic where the Barents Sea waters are cleaner than the Atlantic waters that are impacted by the North Cape Current.

Figure 3.10.9.5 Content of heavy metals in the muscles of Greenland halibut in the Barents Sea (n = 99) from VNIRO’s monitoring from 2009 to 2020. Figure 3.10.9.5 Content of heavy metals in the muscles of Greenland halibut in the Barents Sea (n = 99) from VNIRO’s monitoring from 2009 to 2020.

For cadmium and mercury in muscle, no decreasing trend was observed in the Russian monitoring. Also, in IMR’s long term monitoring of cod, very stable mercury levels are observed (Figure 3.10.9.8). However, the contents of these metals in muscle of commercial fish in the Barents Sea are initially very low: tens and hundreds of times lower than that of for other examined metals. In the Norwegian monitoring, cadmium concentrations were lower than the analytical limit of quantification (LOQ,

Figure 3.10.9.6 Contents of heavy metals in the muscles of cod in the Barents Sea (n = 267) from VNIRO’s monitoring from 2009 to 2020. Figure 3.10.9.6 Contents of heavy metals in the muscles of cod in the Barents Sea (n = 267) from VNIRO’s monitoring from 2009 to 2020.

Figure 3.10.9.7 Content of heavy metals in the muscles of plaice in the Barents Sea (n = 161) from VNIRO’s monitoring from 2009 to 2020. Figure 3.10.9.7 Content of heavy metals in the muscles of plaice in the Barents Sea (n = 161) from VNIRO’s monitoring from 2009 to 2020.

Also analyses of whole capelin show stable levels of mercury in the Barents Sea (Figure 3.10.9.9). There was, however, a weak, but significantly decreasing trend for the level of mercury in polar cod after 2010 (Figure 3.10.9.9). The trend for polar cod was not related to sampling latitude, yet it cannot entirely be ruled out that the decreasing trend is caused by polar cod making longer northwards migrations in later years.

Figure 3.10.9.8 Annual concentrations of mercury in fillet of cod sampled in Norwegian monitoring from 1994 to 2020. For each year, mean, minimum and maximum values are shown. Figure 3.10.9.8 Annual concentrations of mercury in fillet of cod sampled in Norwegian monitoring from 1994 to 2020. For each year, mean, minimum and maximum values are shown.

Figure 3.10.9.9 Temporal variation in mercury concentration (Hg, mg/kg wet weight) in composite samples of whole capelin and polar cod. Top: For each year (2006-2020) and species, mean, minimum and maximum values are given. Bottom: Temporal trend from of log-transformed mercury concentrations from 2011 to 2020. Result of Pearson’s one-way correlation between log10-transformed mercury concentration (LogHg) and year is shown. Figure 3.10.9.9 Temporal variation in mercury concentration (Hg, mg/kg wet weight) in composite samples of whole capelin and polar cod. Top: For each year (2006-2020) and species, mean, minimum and maximum values are given. Bottom: Temporal trend from of log-transformed mercury concentrations from 2011 to 2020. Result of Pearson’s one-way correlation between log10-transformed mercury concentration (LogHg) and year is shown.

Status and temporal trends of organic contaminant levels in fish liver or whole fish

Concentrations of organic contaminants are found in fish and crustaceans in the Barents Sea at significant and measurable levels, and the concentrations are higher in liver than in fillet of most fish species. The levels of the analysed substances are, however, relatively low in the Barents Sea compared to areas further south, except for the level HCB, which seems to be higher in the Barents Sea. The persistent organic pollutants PCBs and PBDEs are generally above environmental quality standard (EQS) values, which may indicate potentially harmful effects for animals at high trophic level such as for instance polar bears. It is not known, however, whether the levels of these substances in top predators and fish eaters such as marine mammals and seabirds in the Barents Sea actually have harmful effects.

In order to evaluate time trends for levels of persistent organic pollutants in the Barents Sea biota, data from analyses of liver of cod and whole capelin and polar cod have been assessed (Figure 3.10.9.10-16).

Figure 3.10.9.10 Temporal trend for dioxins and dioxin-like PCBs in cod liver, including fish with lengths between 50 and 70 cm. Top: Concentrations per year of Sum dioxins and furans (dioxin), sum dioxin-like PCBs (dl-PCB) and sum dioxins and dl-PCB, given as mean values and non-outlier range. Bottom: Correlation between log10-transformed concentration of the sum dioxins and dl-PCB and year, categorized by latitude south and north of 73°N. Results of Pearson’s correlation with log10 transformed concentrations are shown for each category. Figure 3.10.9.10 Temporal trend for dioxins and dioxin-like PCBs in cod liver, including fish with lengths between 50 and 70 cm. Top: Concentrations per year of Sum dioxins and furans (dioxin), sum dioxin-like PCBs (dl-PCB) and sum dioxins and dl-PCB, given as mean values and non-outlier range. Bottom: Correlation between log10-transformed concentration of the sum dioxins and dl-PCB and year, categorized by latitude south and north of 73°N. Results of Pearson’s correlation with log10 transformed concentrations are shown for each category.

The level of dioxins and dioxin-like PCBs and non-dioxinlike PCBs in liver of cod appears to have decreased since 2007 (Figure 3.10.9.10 top, Figure 3.10.9.11 top). In 2007, the mean concentration of the sum of dioxin and dioxinlike PCBs was slightly above the special maximum level of 20 ng TEQ/kg wet weight applying to fish liver in Norway and EU, while in the years 2017-2020 mean concentrations were below 10 ng TEQ/kg. However, because sampling area and fish size may affect the results, an analysis of the trend has been done separately for samples taken south and north of 73°N and including only fish between 50 and 70 cm length. For the sum of dioxins and dioxin-like PCBs there then was a significant, but very weak, decline in the level of dioxins and dl-PCB south of 73°N and no decline north of 73°N (Figure 3.10.9.10 bottom). The top panel of Figure 3.10.9.10 also shows that the dioxin-like PCBs dominate the sum of dioxins and dioxin-like PCBs and that the dioxins and furans initially had very low concentrations and changed much less over the years than the dioxin-like PCBs.

Figure 3.10.9.11 Temporal trend for non-dioxinlike PCBs in liver of cod. Top: Annual concentrations of sum PCB7 (sum of PCB-28, 52, 101, 118, 138, 153, 180; µg/kg wet weight, Program 1, P-1) and sum PCB6 (PCB7 minus PCB-118; µg/kg wet weight; Program 2, P-2) in liver of cod from 1992 to 2020. For each year, mean, minimum and maximum values are shown. Bottom: Correlation between concentrations of PCB7 in fish from P-2 between 50 and 70 cm, categorized by latitude south and north of 73°N. Results of Pearson’s correlation are shown for each category. Figure 3.10.9.11 Temporal trend for non-dioxinlike PCBs in liver of cod. Top: Annual concentrations of sum PCB7 (sum of PCB-28, 52, 101, 118, 138, 153, 180; µg/kg wet weight, Program 1, P-1) and sum PCB6 (PCB7 minus PCB-118; µg/kg wet weight; Program 2, P-2) in liver of cod from 1992 to 2020. For each year, mean, minimum and maximum values are shown. Bottom: Correlation between concentrations of PCB7 in fish from P-2 between 50 and 70 cm, categorized by latitude south and north of 73°N. Results of Pearson’s correlation are shown for each category.

The non-dioxinlike PCBs (given as PCB7 or PCB6) are often used as a proxy for total PCB contamination. The non-dioxinlike PCBs in cod liver have been analysed in program 1 since 1992 and in program 2 since 2006, during which time their levels seem to have decreased (Figure 3.10.9.11 top). Between 1992 and 2008, mean concentration more than halved from almost 300 to around 100 µg/kg, and in 2020 the mean concentration was only around 50 µg/kg. When including only cod between 50 and 70 cm from program 2 and categorizing between fish sampled south and north of 73°N, there was still significant, although weak, decrease in the PCB7 concentration for both geographical areas (Figure 3.10.9.11 bottom).

Figure 3.10.9.12 Temporal trends for concentrations of PCB7 (sum of PCB-28, 52, 101, 118, 138, 153, 180; µg/kg wet weight) in composite samples of whole capelin and polar cod  in composite samples of whole capelin and polar cod from 2006 to 2020. Top: For each year from 2006 to 2020, mean, minimum and maximum values are shown. Bottom: Correlation between lipid weight concentrations of PCB7 (µg/kg lipid weight) in A) Capelin, categorized by latitude south and north of 75°N, and B) polar cod, categorized by latitude south of 75°N (correlation not shown), between 75 and 78°N and north of 78°N. Results of Pearson’s correlation are shown for each category. Figure 3.10.9.12 Temporal trends for concentrations of PCB7 (sum of PCB-28, 52, 101, 118, 138, 153, 180; µg/kg wet weight) in composite samples of whole capelin and polar cod in composite samples of whole capelin and polar cod from 2006 to 2020. Top: For each year from 2006 to 2020, mean, minimum and maximum values are shown. Bottom: Correlation between lipid weight concentrations of PCB7 (µg/kg lipid weight) in A) Capelin, categorized by latitude south and north of 75°N, and B) polar cod, categorized by latitude south of 75°N (correlation not shown), between 75 and 78°N and north of 78°N. Results of Pearson’s correlation are shown for each category.

The levels of PCB7 in capelin and polar cod also seem to have decreased somewhat since 2006, and perhaps more steeply in capelin than in polar cod (Figure 3.10.9.12 top). For capelin there was a significant decrease in concentrations with increasing latitude, and since the samples tended to be taken further north in later years, separating the effects of latitude and year is challenging. Also, fat contents of the fish may affect the concentrations. However, when capelin data were categorised by sampling latitude south and north of 75°N (Figure 3.10.9.12A), lipid normalised concentrations of PCB7 (µg/kg lipid weight) in capelin still showed a significant decreasing trend in both areas. For polar cod there was no decreasing trend for lipid normalised PCB7 concentrations neither north of 78°N nor between 75 and 78°N (Figure 3.10.9.12B). Among chlorinated pesticides, there has been a clear decrease in concentrations of DDT in cod liver since 1992, while HCB levels have remained very stable (Figure 3.10.9.13). For polar cod, the level of HCB seems to be almost increasing in later years (Figure 3.10.9.14). The trends have not been analysed with regard to sampling latitude.

Figure 3.10.9.13 Annual concentrations of sum DDT and hexachlorobenzene (HCB) in liver of cod from 1992 to 2020. Results from program 1 (P-1) and program 2 (P-2) are given separately. For each year, mean, minimum and maximum values are shown. Figure 3.10.9.13 Annual concentrations of sum DDT and hexachlorobenzene (HCB) in liver of cod from 1992 to 2020. Results from program 1 (P-1) and program 2 (P-2) are given separately. For each year, mean, minimum and maximum values are shown.

Figure 3.10.9.14 Annual concentrations of hexachlorobenzene (HCB) in composite samples of whole capelin and polar cod from 2006/2007 to 2019. For each year, mean, minimum and maximum values are shown. Figure 3.10.9.14 Annual concentrations of hexachlorobenzene (HCB) in composite samples of whole capelin and polar cod from 2006/2007 to 2019. For each year, mean, minimum and maximum values are shown.

The level of brominated flame retardants, PBDEs, appears to have decreased since 2006/2007, both in cod liver, capelin and polar cod (Figure 3.10.9.15 and 16). For cod liver, the decreasing trend was significant (here shown for the concentration of PBDE-47 the most dominating congener) in livers of cod sampled both south and north of 73°N (Figure 3.10.9.15 bottom). For capelin, PBDE decreased significantly (PBDE7, µg/kg lipid weight) for samples taken both south and north of 75°N (Figure 3.10.9.16A). For polar cod, there was no significantly decreasing trend when categorising between samples taken at different latitudes (Figure 3.10.9.16B).

Figure 3.10.9.15 Temporal trend for polybrominated diphenyl ethers (PBDEs, µg/kg wet weight) in liver of cod from 2006 to 2020. Top: Results from program 1 (P1) and program 2 (P2) are given as  mean, minimum and maximum values per year. In P1, PBDE15 is the sum of 15 PBDE congeners and for P2, PBDE6 is the sum of 6PBDE congeners (PBDE 28, 47, 99, 100, 153, 154). Bottom: Correlation between log10 transformed concentration of PBDE-47 and year, categorized by latitude south and north of 73°N. Only individuals between 50 and 70 cm sampled in program 2 are included, and results of Pearson’s correlation are shown for each category. Figure 3.10.9.15 Temporal trend for polybrominated diphenyl ethers (PBDEs, µg/kg wet weight) in liver of cod from 2006 to 2020. Top: Results from program 1 (P1) and program 2 (P2) are given as mean, minimum and maximum values per year. In P1, PBDE15 is the sum of 15 PBDE congeners and for P2, PBDE6 is the sum of 6PBDE congeners (PBDE 28, 47, 99, 100, 153, 154). Bottom: Correlation between log10 transformed concentration of PBDE-47 and year, categorized by latitude south and north of 73°N. Only individuals between 50 and 70 cm sampled in program 2 are included, and results of Pearson’s correlation are shown for each category.

Figure 3.10.9.16 Temporal trend of concentrations of sum PBDE7 (sum of PBDE 28, 47, 99, 100, 153, 154, 180; µg/kg wet weight) in composite samples of whole capelin and polar cod from 2006 to 2020. Top: For each year, mean, minimum and maximum values are shown. Bottom: Correlation between lipid weight concentrations of PBDE7 (sum of PBDE 28, 47, 99, 100, 153, 154, 180; µg/kg lipid weight) and year in A) Capelin, categorized by latitude south and north of 75°N, and B) Polar cod, categorized by latitude south of 75°N (correlation not shown), between 75 and 78°N and north of 78°N. Result of Pearson’s correlation is shown. Figure 3.10.9.16 Temporal trend of concentrations of sum PBDE7 (sum of PBDE 28, 47, 99, 100, 153, 154, 180; µg/kg wet weight) in composite samples of whole capelin and polar cod from 2006 to 2020. Top: For each year, mean, minimum and maximum values are shown. Bottom: Correlation between lipid weight concentrations of PBDE7 (sum of PBDE 28, 47, 99, 100, 153, 154, 180; µg/kg lipid weight) and year in A) Capelin, categorized by latitude south and north of 75°N, and B) Polar cod, categorized by latitude south of 75°N (correlation not shown), between 75 and 78°N and north of 78°N. Result of Pearson’s correlation is shown.

There are thus indications that the levels of persistent organic contaminants such as dioxins, PCBs and DDTs have been decreasing and are still slowly decreasing in the Barents Sea. This pattern seems to be the clearest for PBDEs, which were banned around 2005. HCB seems not to decrease at all. The latter may be because HCB can be breakdown product from other pesticides still in use. The mercury level in cod fillet has remained very stable since 1994, while concentrations may be decreasing in polar cod.

Pollutants in polar bears (Ursus maritimus)

By Heli Routti (NPI), Louise Kiel Jensen (NPI) and Hanne Johnsen (NPI)

The contaminant load in polar bears from Svalbard is dominated by fat-soluble organic pollutants, their degradation products (metabolites) and perfluorinated compounds, while levels of new commercial chemicals are low. Pollutants in polar bears have been monitored by the Norwegian Polar Institute for several decades and is presented through MOSJ (environmental monitoring of Svalbard and Jan Mayen, www.mosj.no) as well as in research literature (e.g. the review by Routti et al. (2019)).

Many Arctic organisms including polar bears store energy as fat in periods of rich food supply, which can be utilized during periods of low food supply. Periods of fasting and utilization of body fat are natural for Arctic biota but can be critical when a large pool of contaminants stored in adipose tissue become more concentrated and/or are released into the blood when fat is burned. This makes contaminants available for uptake into organs such as the liver and brain.

As a top predator, the polar bear is particularly exposed to contaminants. Many contaminants biomagnify, meaning that their concentrations increase toward the top of a food chain and the organisms at the top thus have a high intake of contaminants. At the same time, persistent contaminants are not easily metabolized and excreted and therefore accumulate over time.

Samples from polar bears in Svalbard are collected every year in the spring season. Polar bears are immobilized from a helicopter, and blood samples, fat biopsies and hair samples are taken for analyzes of contaminants and dietary sources (measurement of stable isotopes). Female bears are also weighed and measured to determine body condition, and a tooth is taken out for age estimation. Habitat use for some females is monitored using satellite collars. Body condition, age, number of cubs, eating habits or area are included in the statistical analyzes to test whether these affect the levels of contaminants in polar bears. Only female polar bears are included in the time trend studies to eliminate any gender differences.

Barents Sea polar bears may be divided into two subgroups according to their space-use. Pelagic polar bears follow the ice to the east when the ice around Svalbard melts in the summer while coastal polar bears stay in Svalbard throughout the year. The pelagic polar bears have a higher intake of organic pollutants compared to the coastal polar bear (Blévin et al. 2020). There are several reasons for these differences. For example, pelagic polar bears eat a higher proportion of marine prey, and at a higher trophic level than coastal bears. They also have higher energy requirements and thus a higher intake of prey. In addition, pelagic polar bears eat a higher proportion of prey caught in the marginal ice zone and prey that are closer to the sources of pollution/ transport routes. Despite higher energy consumption, pelagic polar bears were fatter compared to coastal bears. This is most likely due to high intake of seals throughout the year. Although the intake of pollutants is higher in pelagic polar bears than in coastal bears, they have equal concentrations of fat-soluble contaminants in plasma. This is because pelagic individuals have a greater amount of fat where fat-soluble compounds are stored.

Overall, monitoring of polar bears shows that concentrations of fat-soluble organic contaminants (PCBs and oxychlordane) have decreased between 1997 and 2017 (Figure 3.10.10.1). This is in line with the trends seen in several other Arctic animals and is a confirmation that international regulations on these substances have been successful.

Figure 3.10.10.1 Geometric mean of PCB-153 and oxychlordane in plasma from polar bear, lipid weight, from 1991-2017. Data from Norwegian Polar institute. Figure 3.10.10.1 Geometric mean of PCB-153 and oxychlordane in plasma from polar bear, lipid weight, from 1991-2017. Data from Norwegian Polar institute.

The concentrations of DDE and HCB decreased until 2010, and then the concentrations increased until 2017 (21% per year for DDE and 11% per year for HCB) (Figure 3.10.10.2). The level of PFOS, the perfluorinated substance which was phased out in 2001 by the major producer 3M, decreased by 14% per year in the period 2003-2009, but has been stable since then. In contrast, the levels of newer perfluorinated substances increased by around two per cent per year in the period 2000-2014 (Figure 3.10.10.3). These trends show that a reduction in worldwide use of the contaminants can be traced in Arctic areas, but also that there is still a continuous supply to the Arctic. The diet of polar bears has changed over time; they eat less marine prey high up the food chain today than they tended to do in the past. These changes did not affect the observed time trends of organic pollutants in polar bears.

Figure 3.10.10.2 Geometric mean of HCB, DDE and HCH in plasma from polar bear, lipid weight, from 1991-2017. Data from Norwegian Polar institute. Figure 3.10.10.2 Geometric mean of HCB, DDE and HCH in plasma from polar bear, lipid weight, from 1991-2017. Data from Norwegian Polar institute.

Figure 3.10.10.3 Geometric mean of PFOS, PFUnDA and PFNA in plasma from polar bear, lipid weight, from 1991-2017. Data from Norwegian Polar institute. Figure 3.10.10.3 Geometric mean of PFOS, PFUnDA and PFNA in plasma from polar bear, lipid weight, from 1991-2017. Data from Norwegian Polar institute.

Measurements of mercury in hair of adult polar bear females from Svalbard in the period 1995-2016 show that mercury levels (total mercury) increased over time, especially in the last half of the study period (Figure 3.10.10.4). Mercury levels were lower in polar bears with a more terrestrial diet compared with polar bears with a more marine diet. When mercury levels were adjusted for temporal changes in diet, the increase was somewhat faster, but the difference between the trends was not significant. Mercury is of both natural and man-made origin. Man-made sources are estimated to account for about 90% of mercury exposure in polar bears. Compared with polar bears from Greenland and North America the levels of mercury in polar bears from Svalbard are low (Routti et al. 2019).

Figure 3.10.10.4 Geometric mean of mercury in polar bear hair, from 1991-2017. Data from Norwegian Polar institute. Figure 3.10.10.4 Geometric mean of mercury in polar bear hair, from 1991-2017. Data from Norwegian Polar institute.

Overall, compared to other Arctic biota, the levels of contaminants are high in polar bears. Further, polar bear cubs have been shown to have more than twice as high levels of fat-soluble contaminants compared to female polar bears (Bytingsvik et al. 2012). Studies on pollutant effects in polar bears suggest that the contaminant load may affect the activity of important molecules in the brain, the immune system and hormones that are important for developmental processes and energy metabolism (Routti et al. 2019). Contaminants may also interfere with fat storage and fat burning processes in polar bears (Routti et al. 2019). Furthermore, the high levels of contaminants in polar bears may make them more susceptible to infection and disease, and for polar bear cubs, the substances have a potential to affect development (Jenssen et al. 2015).

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