Contaminants in the environment, plants and animals in Antarctica
The levels of contaminants in Antarctica are, on the whole, lower than elsewhere in the world. This applies to those in the atmosphere, water, sediments and animals and plants.
Comparatively few studies of atmospheric contamination have been undertaken in Antarctica and the Southern Hemisphere. The studies that have been performed have largely focused on transport mechanisms and processes with a view to distinguishing local sources from far-transported contamination. It has been shown that aerosols (and, hence, atmospheric transport) are the most important medium for long-range transport of pollution to Antarctica.
In 2007, Norway set up a measuring station at Troll, in Dronning Maud Land in Antarctica. The Norwegian Institute for Air Research (NILU) is responsible for monitoring among others mercury, organic pollutants, hydrocarbons and CO2. Preliminary conclusions from this monitoring confirm that concentrations of a number of organic pollutants in the atmosphere are lower than background levels in the Arctic. The measurements at Troll also show that HCB (a herbicide) is the dominant pollutant, as it is in the Arctic, too. The pollutant levels fluctuate through the year, in line with when coastal air masses meet the continent.
A few isolated studies of contaminants in the waters around the Antarctic have been performed. A study from the Ross Sea showed that levels of organic pollutants were closely linked with the amounts of suspended material which, in turn, vary through the summer. This is related to melting of sea ice and liberation of particles which were frozen into the ice.
In the same area, a clear link has been observed between the amount of PCBs in the seawater and the melting of sea ice. The PCB level in surface water is initially low (130 pg/l), but rises by up to 30-40 % when the ice melts. This rise is due to liberation of PCBs originating from atmospheric fall-out through precipitation, for example, and which have been locked in the ice for a period after the sea froze.
Snow and ice
The ice in Antarctica acts as an archive for studies of earlier and present-day transport of contaminants to the Antarctic, and the ice cores can therefore be used as climate archives from which scientists can acquire information.
Time series analyses of lead in snow samples from Coats Land, Victoria Land and Law Dome showed that lead levels have varied from 1880 to the present day, but there has been an obvious decline following the ban on lead in fuel in the 1980s.
Analyses of ice and snow samples from other parts of Antarctica suggest that the continent has also received a significant supply of other metals from the atmosphere, including chromium, copper, zinc and arsenic.
Contaminants in the sediments have been investigated in connection with the research stations in the Antarctic. PAH levels in the sediments close to the Brazilian research station in Admiralty Bay were found to be three times higher than in uninhabited areas. Sediment samples from the vicinity of McMurdo, the American base in McMurdo Sound, and near the American Palmer Station, showed that the sediments were contaminated with both PCBs and PAHs. Recent studies at the McMurdo Station and New Zealand’s Scott Base have revealed brominated flame retardants in the inside air and wastewater.
Plants and animals
Organic pollutants in plankton have mostly been investigated near the research stations and their sewage systems. The results are therefore not especially representative for plankton in Antarctica. Studies of contaminants in krill, a key species in the Antarctic ecosystem, have shown that HCB is the most dominant contaminant. The studies have so far not found any biomagnification from plankton to krill.
Fish which live on the shelf, such as emerald rockcod, contain contaminants like DDT, PCBs and PAHs in levels corresponding to those in their most important food item, krill. The levels are lower than in fish in other waters. Bottom-living fish species have somewhat higher levels of contaminants because they feed on other nutrient sources than krill.
Marine mammals in Antarctic waters have far lower levels of contaminants than those in the Arctic. However, it has been found that levels of some herbicides rose in 1984-1994 in species living in the south, whereas they fell in the north. This means that the herbicides were still being used in the Southern Hemisphere, whereas they were banned in the north. Weddell seals at George V Land have the lowest values in the world of DDT and PCBs in their blubber, and they are also lower than in seals elsewhere in Antarctica. This shows that the variations may be great within Antarctica, too.
Emperor and Adélie penguins are good indicator species for the marine food chain because they breed on the continent itself. Adélie penguins have a low transfer rate for PCBs and DDE from mother to chick, only 4 %. In general, the concentrations of organic pollutants in penguins are lower than known threshold values for toxicological effects. However, as no research has been performed on threshold values for penguins, no conclusions can be drawn about this. Studies from Palmer Station show that levels of DDE (a breakdown product of the herbicide, DDT) have not changed in Adélie penguins on the Antarctic Peninsula for 30 years, in contrast to DDT levels, which fell significantly in 1975-2003 in seabird eggs in Antarctica as a whole.
A baseline survey carried out in 1997 on the Antarctic Peninsula focused on levels of heavy metals in Antarctic organisms (34 species of algae, filtering animals, invertebrates and vertebrates). Mercury was only found in elephant seals and seabirds in low levels, whereas cadmium was found in low levels in the majority of organisms, except fish. Some invertebrates had very high contents of zinc, whereas the highest copper levels were found in a snail.
Organiske miljøgifter i plankton er stort sett undersøkt i nærheten av forskningsstasjonene og deres avløpssystemer. Resultatene er derfor ikke spesielt representative for plankton i Antarktis. Studier av miljøgifter i krill, en nøkkelart i det antarktiske økosystemet, har vist at HCB er den mest dominerende miljøgiften. Studiene så langt har ikke påvist biomagnifisering fra plankton til krill.
Fisk som lever på sokkelen, som Trematomus bernacchi (engelsk «rock cod») inneholder miljøgifter (som DDT, PCB og PAH) i tilsvarende nivåer som sitt viktigste næringsemne, krill. Nivåene er lavere enn fisk i andre havområder. Bunnlevende fiskearter har noe høyere nivåer av miljøgifter, noe som skyldes at de ernærer seg av andre næringskilder enn krill.
Sjøpattedyr i antarktiske farvann har mye lavere nivåer av miljøgifter enn sjøpattedyr i Arktis. Imidlertid er det funnet at nivåer av enkelte plantevernmidler økte i perioden 1984–1994 i arter med tilhold i sør, mens de sank i nord. Dette betyr at plantevernmidlene fortsatt var i bruk på sørlige halvkule mens de var forbudt i nord. Weddellseler på Kong Georges Land har de laveste verdiene av DDT og PCB i spekket på verdensbasis, og også lavere enn seler andre steder i Antarktis. Dette viser at variasjonene kan være store også innenfor Antarktis.
Keiserpingviner og Adéliepingviner er gode indikatorarter for den marine næringskjeden siden de hekker på selve kontinentet. Adéliepingviner har en lav overføringsrate av PCB og DDE fra mor til unge, kun 4 %. Generelt er konsentrasjonene av organiske miljøgifter i pingviner lavere enn kjente terskelverdier for toksikologiske effekter. Imidlertid er det ikke forsket på terskelverdier for pingviner, så en kan ikke konkludere på dette feltet. Studier fra Palmerstasjonen viser at nivåene av DDE (et nedbrytningsprodukt av plantevernmidlet DDT) ikke har endret seg i Adéliepingviner på den antarktiske halvøya på 30 år. Dette står i motsetning til nivåene av DDT, som ble sank betraktelig i perioden 1975–2003 i sjøfuglegg i Antarktis generelt.
En grunnlagsundersøkelse gjennomført i 1997 på den antarktiske halvøya fokuserte på nivåer av tungmetaller i antarktiske organismer (34 arter av alger, filtrerende dyr, virvelløse dyr (evertebrater) og virveldyr (vertebrater)). Kvikksølv ble kun funnet i elefantsel og sjøfugl i lave nivåer, mens kadmium ble funnet i lave nivåer i flertallet av organismene, unntatt fisk. En del evertebrater hadde svært høyt innhold av sink, mens de høyeste nivåene av kobber ble funnet i en snegle.
- J.L. Carroll, A. Evenset., K. Borgå, G.W. Gabrielsen, H. Kylin and S. Corsolino. NARE PROGRAMME PROJECT. Flux of organic contaminants through lower trophic levels of the Antarctic food web. Final report. Norges forskningsråd.
- R. Kallenborn et.al. 2013. Long-term monitoring of persistent organic pollutants (POPs) at the Norwegian Troll station in Dronning Maud Land, Antarctica. Atmos. Chem. Phys. Discuss., 13, 6219-6246. DOI: 10.5194/acpd-13-6219-2013