ABANDONED PENGUIN ROOKERIES AS HOLOCENE PALEOCLIMATIC INDICATORS IN ANTARCTICA

Penguins are sensitive indicators of the Antarctic climate and of the environmental parameters that limit their presence and distribution. Paleoenvironmental data, obtained from the study of abandoned penguin rookeries (Pygoscelis adeliae) along the Victoria Land coast in Antarctica, indicate a C-14 date of 11-13 ka for the oldest abandoned rookery and supply new information about the timing of glacier retreat in southern Victoria Land after the last glacial maximum. The continuous presence of the Adelie penguins is documented from 7 ka. According to our data, the limiting factors that control the presence of penguins along the coast of Victoria Land changed during the Holocene. Whereas several colonies were occupied for very long periods, other sites were used for more or less extended periods and then abandoned. The greatest diffusion of rookeries occurred between 3 and 4 ka, a period of particularly favorable environmental conditions that has never been repeated. It was followed by a sudden decrease in the number of penguin rookeries shortly after 3 ka. This event has been attributed to an increase of the sea-ice extension and may have been correlated to a worldwide phase of climate change near the Subboreal-Subatlantic boundary. A minor phase of penguin reoccupation occurred locally in the eighth to fourteenth centuries (A.D.). Because the presence and number of penguins reflect the state of health of the Antarctic marine ecosystem, it is important to evaluate the variations in their distribution in the past, in the absence of human-induced changes.