Pollutants in glaucous gulls (Larus hyperboreus)
The glaucous gull is at the top of the food chain and exposed to excessively high amounts of persistent organic pollutants. It is the most abundant of the large gulls in the Arctic, and its important food items are benthic fauna, fish, carrion, and eggs and chicks of other seabirds.
What is being monitored?
Individual blood samples from glaucous gulls are analysed. The blood is centrifuged and the light-coloured part (the blood plasma) is analysed for pollutants.
The glaucous gull is listed as Near Threatened on the Svalbard Red List. Consequently, it has been decided to use blood samples for the monitoring rather than killing the birds. The samples are taken in connection with other Norwegian Polar Institute fieldwork.
The samples are processed in the laboratory using various techniques so that several groups of pollutants can be analysed. The following is done to analyse for organic, fat-soluble chemical sprays, PCBs and some brominated flame retardants (BFRs):
- 1ml of plasma is weighed and an internal standard for sprays, PCBs and BFRs is added.
- 2ml superclean (milliQ) water saturated with ammonium sulphate and 2ml of ethanol are added, and the solution is vigorously mixed (vortex).
- Pollutants, fat and proteins are then extracted from the mixture twice using 6ml of n-hexane as the solvent.
- The extract is concentrated to 200μl by vacuum evaporation (RapidVap).
- It is further cleansed with activated Florisil (magnesium silica) in a RapidTrace SPE machine.
The samples are analysed in an interlinked gas chromatograph – mass spectrometer (GC-MS). The sample is injected and separated on a 30-metre column. The initial temperature is 60–70 °C, and this is raised by steps using pre-determined programmes depending on which substances are being analysed. Helium is used as the carrier gas in the machine.
The concentrations are calculated by quantifying internal standards with known concentration and comparing these with the response (chromatogram) from the samples.
The analysis is quality assured using the methods described in the accreditation. To avoid sample contamination, only superclean equipment is used in the laboratory. A blank and a standard reference sample are analysed for every 10th sample. The laboratory regularly takes part in international proficiency testing schemes.
Since the data are only collected every 3rd year, the analysis will fail to give information on the variation in pollutant concentrations from year to year. When analysing time series, allowance must therefore be made for the possibility that year-to-year variations are not being detected. It will therefore take a long time to demonstrate changes in the time series since it is difficult to determine whether a difference between two measured points is due to an actual change or a random variation.
The lower Level of Detection (LOD) is calculated for each sample and is usually better than 0.1ng/g. For PCB-153 and p,p’-DDE, this is approximately 1000 times lower than the measured value in the sample. For oxychlordane, this is approximately 500 times lower than the measured value in the sample. For HCB, this is approximately 20 times lower than the measured value in the sample. The uncertainty is around 25–30%. Particularly LOD, but also the measurement uncertainty, has improved in recent years. In time series, there will therefore always be greater uncertainty attached to older measurements in the series.
The analysis is quality assured in accordance with the methods described in the accreditation. To avoid sample contamination, only superclean equipment is used in the laboratory. A blank and a standard reference sample are analysed for every 10th sample. The laboratory regularly takes part in international proficiency testing schemes.
Reference level and action level
As POPs are manufactured pollutants that are not found in a natural state, the reference value for an unaffected state will be zero (really the detection limit).
As the glaucous gull is a protected species, it is not used as human food. Hence, no limits have been set for the content of PCB or other pollutants in glaucous gulls. However, dietary advice has been given regarding gull’s eggs in Norway. This will also apply to glaucous gull eggs. The advice is to limit their consumption, and children and women of fertile age should not eat gull’s eggs.
Stringent measures have been applied to limit the spread of persistent organic pollutants. The Stockholm Convention regulates an international ban on the manufacture and use of PCBs and most western nations introduced strict regulations of PCBs around 1980. Furthermore, the Stockholm Convention regulates an international ban on the manufacture and use of DDT, and most western nations introduced strict regulations of DDT at the end of the 1960s and the beginning of the 1970s. The Stockholm Convention regulates an international ban on the manufacture and use of chlordanes and most western countries introduced strict regulations of chlordanes in 1970–1990. Chlordanes have been little used in Europe.The Stockholm Convention regulates an international ban on the manufacture and use of HCB as a fungicide and verifies that the chemical industry has reduced its emissions.
Status and trend
The levels of organic spray chemicals like HCB and chlordane (oxychlordane) have dropped during the 18 years the glaucous gulls have been monitored. However, there are substantial variations from year to year. These variations mean that it is too early to draw ultimate conclusions regarding the trends, but since the trends coincide with the ban on the use and discharge of the pollutants, it is most likely that the average reduction is real.
The concentration of the insecticide DDT also varies considerably from year to year. It is not possible to say whether the DDT levels in glaucous gulls are rising or falling. This is actually surprising because the use of DDT was banned in most western countries already in the 1970s. However, some DDT is being used to combat the malaria mosquito in southern parts of Africa following a recommendation from the World Health Organisation (WHO), but it is uncertain whether any of this can be found in the Arctic. Another possible reason may be that the levels had already declined before the measurements began and the speed of the reduction has flattened out. The proportion of DDT is still high compared with the other pollutants known to be present in glaucous gulls.
The PCB level is presented in MOSJ as the concentration of PCB-153, the most stable variant of the 209 theoretically possible PCBs. There is a very good link between PCB-153 and the other PCBs. The concentration of PCB-153 therefore gives a correct picture of the development of the PCB levels in the glaucous gull.
There was some variation in the concentration of PCB during 1997–2009, but on the whole the levels halved during this period due to the regulations that were introduced. New uses for PCB were banned in most western countries in the early-1980s. Many countries also put emphasis on dealing with PCB in rubbish during the phasing-out period, which was probably important since very large quantities of PCB were used in many products.
The high levels of "old" organic pollutants like PCB, DDT, chlordane and HCB, and partially high values of "new" pollutants like brominated flame retardants (Ʃ13PBDE) and fluorine compounds (Ʃ3PFS and Ʃ10PFCA) are mainly caused by 2 factors.
- The glaucous gull is at the top of the food chain. These pollutants are stable and are slowly broken down in nature. The pollutants entering the food chain therefore become more concentrated as the animals eat (bioaccumulation). When these animals are eaten by the next ones in the food chain, further accumulation takes place. Hence, the levels of stable pollutants increase up the food chain. The difference in the concentration at each level in the chain varies considerably from one pollutant to another, and in the food chain in the Barents Sea it is from around one to more than 2000. This is due to the physico-chemical properties of the compounds.
- Glaucous gulls have limited ability to convert and rid themselves of them through their faeces.
The high levels of pollutants recorded in glaucous gulls from 1972 to 2006 have had considerable consequences for the health of the glaucous gulls on Bjørnøya in the Barents Sea.
Some of these glaucous gulls eat large numbers of seabird eggs and chicks during the breeding period and these individuals are particularly likely to have the highest levels of pollutants. The most pronounced effects have been found in these birds, but negative effects have also been seen in birds away from Bjørnøya.
Effects have been found on the enzyme, immune and hormone systems, reproduction and survival. The significance of these effects is, nevertheless, still uncertain, but as so many negative effects have been found in the same population there is little reason to assume that this does not have a negative impact on the health of the glaucous gulls. Modelling has also shown that pollutants probably have negative effects on the glaucous gull population on Bjørnøya.
Glaucous gulls which have been found sick, dying and dead on Bjørnøya have had extremely high levels of pollutants.
There are probably several natural causes for the death of glaucous gulls at their breeding sites, including old age. However, studies show that the ability to find food may be reduced with rising pollutant levels. This means that individuals with a high level of pollutants may starve and thus decline in weight. A drop in weight means that fat is consumed which, in turn, raises the concentration of pollutants since they are in the fat. Consequently, pollutants may contribute to a negative "spiral effect", whereby poor availability of food gives raised pollutant concentrations which, in turn, make the individual less able to find food, ultimately resulting in it dying due to shortage of food and poisoning.
As the glaucous gull is a top predator in the arctic system and is exposed to high levels of pollutants, it is important to follow the trend in pollutant concentrations over time to assess the health of the glaucous gulls and verify that the international regulations concerning pollutants are working.
Samples from glaucous gulls are also often used to seek possible new pollutants.
About the monitoring
The glaucous gull is the most important, large gull in the Arctic. It has a circumpolar distribution, which means that it lives in Arctic areas in Russia, Alaska, Canada, Greenland and Svalbard. The glaucous gull migrates southwards in winter, but not out of the Arctic. The majority of glaucous gulls from Svalbard migrate to the waters off Iceland and the southern tip of Greenland in winter. In summer, glaucous gulls are found in the northern part of the Barents Sea, from Bjørnøya (Bear Island) in the south to Franz Josef land in the northeast.
Knowledge about pollutant levels in glaucous gulls provides knowledge about how pollutants become increasingly concentrated up the food chain and on possible effects in the top predators. The substances included in the monitoring are organic pollutants that are found everywhere in the environment even though many are no longer in use.
Research on glaucous gulls has uncovered effects of pollutants on the behaviour and the immune, enzyme, hormone and vitamin systems of the gulls. Individuals with the highest levels of pollutants have impaired reproductive ability and the survival of adults is lower. A general decline in the levels of phased-out pollutants is therefore positive for the glaucous gulls and the environment. Research to reveal whether known effects disappear with the decline in the "old" pollutants remains to be performed.
Places and areas
Relations to other monitoring
- Monitoring programme
- International environmental agreements
- Voluntary international cooperation
- Related monitoring