Adélie penguin dietary remains reveal Holocene environmental changes in the western Ross Sea (Antarctica) Sandra Lorenzini a, ⁎, Carlo Baroni a,b , Ilaria Baneschi b , Maria Cristina Salvatore a , Anthony E. Fallick c , Brenda L. Hall d a Dipartimento di Scienze della Terra, Università degli Studi di Pisa, Via S. Maria 53, 56126 Pisa, Italy b Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche, Via G. Moruzzi 1, 56124 Pisa, Italy c Scottish Universities Environmental Research Centre, East Kilbride G75 0QF, Scotland, UK d School of Earth and Climate Sciences and the Climate Change Institute, University of Maine, Orono, ME 04469 USA abstract article info Article history: Received 8 June 2013 Received in revised form 28 November 2013 Accepted 8 December 2013 Available online 18 December 2013 Keywords: Adélie penguin Ornithogenic soil Stable isotope Paleoenvironment Paleoceanography Carbon and nitrogen stable isotope analyses were performed on modern and Holocene Adélie penguin guano samples collected from ornithogenic soils along the Scott Coast (Southern Victoria Land, Antarctica), from Cape Irizar to Dunlop Island, and at Cape Bird (Ross Island). Guano samples also were sieved and sorted under stereo- microscope in order to select penguin dietary remains, such as fish bones and otoliths. Carbon and nitrogen stable isotope composition, coupled with the taxonomic identification of fish otoliths from Scott Coast Holocene sam- ples, indicated a mainly fish-based diet for this area, with Pleuragramma antarcticum as the most eaten prey throughout the investigated period (from 390 cal BP to ca 7300 cal BP). The isotopic values of Ross Island sam- ples (from modern to 3850 cal BP) showed a krill consumption increase in the samples younger than 2000 cal BP, with the maximum in modern samples. Scott Coast and Ross Island Holocene samples showed δ 13 C and δ 15 N trends similar to those previously published from Terra Nova Bay (northern Victoria Land), whereas modern samples from Ross Island have similar δ 15 N composition but different δ 13 C values. This δ 13 C divergence started at ca 2000 BP and follows the abandonment of the Scott Coast colonies. The δ 13 C trend observed in Ross Island and Terra Nova Bay samples and the abandonment of the Scott Coast colonies could suggest the stability and the persistence of the previous oceanographic conditions (i.e. polynya) for the Terra Nova Bay area and the establishment of new conditions for water circulation in the Southern Ross Sea since ~2000 BP when persistent sea-ice sealed the Scott Coast. © 2013 Elsevier B.V. All rights reserved. 1. Introduction A fundamental idea in biology is that climatic and environmental changes are the driving force behind biodiversity adaptation through ecological and evolutionary responses (Walther et al., 2002; Parmesan, 2006; Lambert et al., 2010). This assumption is especially true for Adélie penguins (Pygoscelis adeliae) which, because of their extraordinary envi- ronmental sensitivity, have become well known as a ‘bellwether’ of Ant- arctic climate change (Ainley, 2002). Given the significant role that this species plays in the understanding of how the Antarctic environment is changing, Adélie penguins represent one of the best-studied animal spe- cies in the world. Moreover, since the description of ornithogenic soils in the Ross Sea area (multi-millennia penguin-guano deposits, Ugolini, 1972), Adélie penguins have also provided valuable new insights into the late Pleistocene and Holocene glaciological history of Antarctica. In fact, the pristine cold and dry Antarctic environment have led to a high concentration of well-preserved penguin remains (bones, eggshells, guano and dietary remains) in the ornithogenic soils dated back to the late Pleistocene and underlying both existing and abandoned colonies (Ugolini, 1972; Baroni and Orombelli, 1994). These remains represent a unique paleoecological heritage in the context of Antarctic paleoclimatic and paleoenvironmental research. Therefore, since the 1990s, multidisci- plinary studies have intensively investigated Adélie penguin paleoecolo- gy and their colonization history, contributing important information for understanding the Holocene history of key areas of Antarctica (Baroni and Orombelli, 1994; Lambert et al., 2002; Baroni and Hall, 2004; Hall et al., 2004, 2006; Emslie and Woehler, 2005; De Bruyn et al., 2009; Hall, 2009). Moreover, investigation has demonstrated that over at least the last 55,000 yr, local and regional environmental conditions fre- quently changed and Adélie penguins have survived by adapting both their ecological behavior (i.e. foraging and feeding behavior) and the geographic distribution of their colonies (Baroni and Orombelli, 1994; Lambert et al., 2002; Baroni and Hall, 2004; Hall et al., 2004, 2006; Emslie and Woehler, 2005; De Bruyn et al., 2009; Hall, 2009; Lorenzini et al., 2010). The Adélie penguin colonization history of the Southern Victoria Land Coast indicates that abrupt environmental changes occurred during the Late Holocene when the persistence of year-round fast ice caused abandonment of the Scott Coast's colonies, which have not been reoccupied since. This abandonment occurred almost Palaeogeography, Palaeoclimatology, Palaeoecology 395 (2014) 21–28 ⁎ Corresponding author. Tel.: +39 0502215738, fax: +39 0502215800. E-mail address: lorenzini@dst.unipi.it (S. Lorenzini). 0031-0182/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.palaeo.2013.12.014 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo