A tale of three ?cities?: variations by site and ages in isotopic composition and mercury concentrations of Magellanic penguin during the pre-molt stage in three colonies of Tierra del Fuego.

DODINO, SAMANTA; L RICCIALDELLI; K PÜTZ; M POLITO; A RAYA REY

Congreso; international penguin conference; 2019

Penguins are good indicators of environmental changes and respond to oceanographic conditions within their foraging grounds. We studied adult and juveniles Magellanic penguin (Spheniscus magellanicus) trophic niche through 13C and 15N values and determined their mercury concentrations ([Hg]). We sampled feathers during the pre-molt stage from three colonies of Tierra del Fuego with different oceanographic conditions and population size: Franklin Bay (Le Maire Strait, 1,000 pairs), Martillo Island (Beagle Channel, 5,000 pairs) and Observatorio Island (South Atlantic Ocean, 70,000 pairs). Adults had higher δ15N and δ13C values compared with juveniles for the three colonies (p< 0.05), and occupied a higher trophic level (TL) that was reflected in higher [Hg]. Adults did not differ in δ15N values, while δ13C values differed significantly only between Franklin and Martillo. Despite that adults had similar TL estimated we found significantly higher [Hg] and the widest isotopic niche in Observatorio compared with Franklin and Martillo. Meanwhile, juveniles from Martillo had significantly higher δ13C and δ15N values respect to the other colonies that did not differ between them. Juveniles also had similar TL estimated but they differed in [Hg], with the lowest concentration measured in individuals from Martillo and the highest in Observatorio. The exploitation of specific foraging areas by each colony may explain the differences found in [Hg] and in their isotopic niche. This demonstrate the plasticity of these penguins according to the oceanographic variability in their prefer foraging grounds and demography with positive implications in terms of conservation under a climate change scenario. In addition, we highlighted the [Hg] measured with their negative consequences for the future of the species.