Latitude is the main factor which determines the organic pollutant concentration in Antarctic giant petrels -emblematic species in the Antarctic and sub-Antarctic regions-, according to an article from the journal Environmental Research in which Professor Jacob González Solís, from the Department of Evolutionary Biology, Ecology and Environmental Sciences and the Biodiversity Research Institute of the University of Barcelona (IRBio) takes part.

The research, directed by experts of the Institute of General Organic Chemistry (IQOG-CSIC), analyses the impact by persistent organic pollutants (COP) -toxic compounds with a high permanency on the environment which bio-accumulate in organisms- on oceanic birds present in areas of different latitudes in the Antarctic Ocean.

Northern giant petrels (Macronectes halli) and southern ones (M. giganteus) are the great scavengers in sub-Antarctic and Antarctic environments, and they have an extreme life strategy based on a long longevity and low fecundity (an only egg per each reproductive period). They are widely distributed in the southern ocean and can cover thousands of kilometres to feed themselves, but their population are highly vulnerable to any threat affecting their adult survival.

High latitudes, less pollutants

"In general, the further south you go, the lower the levels of organic pollutants are in marine birds. These pollutants, created by human activity, reach all places on earth via atmospheric transport, mainly. They reach the Antarctic too but in less quantity," said Professor Jacob González Solís, author of several genetic and marine bird population studies in the Mediterranean, Atlantic and Antarctic oceans.

"Unfortunately -he continues- we still don't know the effects these compounds could have on ocean birds. Now the detected levels are low, therefore if there is any negative effect it is light so it would be hard to detect. However, we need to do more research in order to discover the effects of chemical pollution on wild fauna."

A chemical footprint for the entire planet

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According to the experts, the organic pollutant levels are similar in Arctic and Antarctic birds. "These chemical compounds, widely used in the past, have probably reached both poles. The organic compounds with a more recent use, such as flame retardants, are now more common in the Arctic than the Antarctic, probably because emission sources are more abundant and closer to the poles in the northern hemisphere rather than in the south. Someday, however, they will get everywhere," warned González Solís.

When mercury gets to Antarctic latitudes

Albatross and giant petrels are the ocean birds with more exposure to mercury pollution in Antarctic and sub-Antarctic environments, according to another study by González Solís (Environmental Pollution, 2016).

"This fact is probably related to the increase of mercury emission in emerging countries," says González Solís. "In general, diet is the main entrance of pollutants in marine birds -continues the expert-. Lots of pollutants (such as COP and mercury) are biomagnified through the trophic network. This makes the most vulnerable species to be found in higher trophic levels (albatross and petrels), since they feed from fish or squids, or in the case of giant petrels, from penguin and seal carrion." Most of the average sized Antarctic penguins, however, feed from krill and therefore their pollution levels are lower.

This other study analyses mercury concentration on feathers, an efficient methodology to control pollution levels of this metal in birds around the world. "With age -says the researcher- these animals can bio-accumulate some of these pollutants in organs such as the liver; but in general they have excretion ways that prevent pollutants from reaching toxic concentrations."

"In the case of mercury, one of the most important excretion ways is the feather changing. To confront the feather wear, most of the birds change them once a year and this process is a mercury excretion mechanism that reduces the levels of this pollutant on the organism," says González Solís. Another excretion way is the creation of the egg, and thus after the egg laying, females use to show lower pollutant levels compared to males.

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Is it possible to lower pollutant emissions?

The effects of pollutants (COP, mercury) vary among the different Antarctic ecosystem organisms. Migrating to lower latitudes and northern hemisphere polluted areas and occupying a higher level in the trophic level are facts that increase the effects of pollutants in ocean birds. Although the toxicity of these products is well documented, its real impact on wild fauna population is still unknown for the scientists.

"These aspects are, in particular, the ones we study with the research in the University of Barcelona, focusing on analysing ecology and preservation of this group of birds" said the author. In this sense, understanding the environment pollution levels is done by studying the ecology of each species, since it is the key factor in final pollution levels. According to the UB-IRBio researcher, "the best way to fight environmental pollution is by reducing its emission sources; but to do so we need international agreements which are hard to get."