| Summary: | Dissertação de Mestrado em Química apresentada à Faculdade de Ciências e Tecnologia The Antarctica and Southern Ocean ecosystems have been suffering changes through the last 30 years, in particular raising of the ocean temperature. These changes occur in a non-circumpolar distribution, for which there are more affected zones than others and, consequently more species in particular regions. It is necessary to understand how these species deal with the environmental changes that are influencing its habitat and how these changes will alter the global marine ecosystems. As Antarctica is the habitat of numerous endemic species, such studies are urgently needed. Due to climate impacts, it is possible to observe evidence of change in the Antarctic food web, where Antarctic krill (Euphausia superba) has decreased its important role in some regions, allowing other zooplankton species to have that role. It is of extreme importance to study the lower trophic levels of this food web, so it is possible to verify the effects of climate change in the species that live in these waters that may help higher trophic levels. Fatty acid analysis allows to assess the response of species to environmental stressors and identify potential food sources, in a trophic ecology context. The zooplankton species of Euphausia superba, Euphausia triacantha, Themisto gaudichaudii, Thysanoessa spp were collected between December 2016 and January 2017, in three locations with distinct characteristics: Antarctic waters, Intermediate and Sub-Antarctic waters. After GC-MS analysis, it was possible to verify that the species E. triacantha, T. gaudichaudii and Thysanoessa spp. presented a better body condition than E. superba. Besides, it was also possible to observe that these three species all revealed better conditions in waters with a higher temperature (Sub-Antarctic waters) than in waters with lower temperatures, closer to the ones found in the Southern Ocean. However, E. superba exhibited a different fatty acid profile (characterized by the ...
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