Late Holocene Adйlie Penguin Population Dynamics at Zolotov
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J Paleolimnol (2011) 45:273–285 DOI 10.1007/s10933-011-9497-x ORIGINAL PAPER Late Holocene Ade´lie penguin population dynamics at Zolotov Island, Vestfold Hills, Antarctica Tao Huang • Liguang Sun • Yuhong Wang • Deming Kong Received: 24 December 2009 / Accepted: 9 October 2010 / Published online: 14 January 2011 Ó Springer Science+Business Media B.V. 2011 Abstract We inferred late Holocene Ade´lie pen- ago, which we interpret as a response to the Little Ice guin occupation history and population dynamics on Age, or a neoglacial cooling event. Zolotov Island, Vestfold Hills, Antarctica, using geochemical data from a dated ornithogenic sediment Keywords Ade´lie penguin Á Antarctic climates Á Ice core (ZOL4). Radiocarbon dates on fossil penguin core Á Ornithogenic sediments Á Western Antarctic bones in the core indicate that Ade´lie penguins Peninsula Á Little Ice Age occupied the island as early as 1,800 years before present (yr BP), following the retreat of the SØrsdal glacier. This occupation began *1,200 years later than that observed at Ardley Island and King George Introduction Island, in the South Shetland Islands. Phosphorus was identified as the most indicative bio-element for Polar seabirds provide important linkages between penguin guano in core ZOL4, and was used to infer marine ecosystems and terrestrial environments. past penguin population dynamics. Around They transport marine-derived nutrients and contam- 1,800 years ago, the Ade´lie penguin populations at inants onto land via their guano and physical remains both Zolotov Island and Ardley Island increased (Sun and Xie 2001a; Blais et al. 2005, 2007; Xie and rapidly and reached their highest levels *1,000 yr Sun 2008; Yin et al. 2008; Brimble et al. 2009; BP. For the past *900 years, the penguin popula- Keatley et al. 2009; Michelutti et al. 2010). Lake tions at Zolotov Island have shown a general rising sediments in areas visited by seabirds can therefore trend, with fluctuations, while those at Ardley Island contain materials of both marine and lacustrine origin have shown a moderate decreasing trend. The Ade´lie (Sun and Xie 2001b). In Antarctica, chemical signa- penguin populations at both Ardley Island and tures from penguin droppings and physical signatures Zolotov Island showed a clear decline *300 years such as bones, feathers and hairs in lake sediments have been used to infer the past population dynamics of penguins and seals, as well as their responses to T. Huang Á L. Sun (&) Á Y. Wang Á D. Kong changing climate and human activities (Hodgson and Institute of Polar Environment, University of Science Johnston 1997; Sun et al. 2000, 2004a, b, 2005; Wang and Technology of China, 230026 Hefei, China et al. 2007; Huang et al. 2009a; Yang et al. 2010). For e-mail: [email protected] example, the penguin populations at Ardley Island Y. Wang and King George Island, South Shetland Islands, National Institutes of Health, Bethesda, MD 20892, USA showed a dramatic decline in the neoglacial period, 123 274 J Paleolimnol (2011) 45:273–285 2,300–1,800 yr BP (Sun et al. 2000), indicating the Many Ade´lie penguin colonies are present on its negative impacts of cooling climate on penguin western coastal islands. During the 1981/1982 sea- populations. sons, it was estimated that there were 196,592 pairs Ade´lie penguins (Pygoscelis adeliae) are the most of breeding Ade´lie penguins on these islands, of abundant seabirds in Antarctica and the bellwether of which 17,496 were on Zolotov Island (Whitehead and Antarctic climate change (Ainley 2002). Their pop- Johnstone 1990). In a previous study, we recon- ulation dynamics are influenced by climatic and structed an 8,500-year record of Ade´lie penguin environmental factors such as sea ice extent and population dynamics at Gardner Island, Vestfold duration, sea surface temperature, air temperature and Hills and examined associations with climate and snow cover (Fraser et al. 1992; Wilson et al. 2001; environmental changes (Huang et al. 2009a). Tem- Jenouvrier et al. 2006; Bricher et al. 2008), and thus poral resolution of the inferred penguin population they provide an integrated response to ecological and shifts at Gardner Island, however, was relatively low, climate changes (Croxall et al. 2002). In the past few and detailed penguin population changes over the decades, observational records of changing Ade´lie past 2,000 years were not resolved. In the present penguin populations have shown strikingly different study, we explore geochemical and chronological trends in the Antarctic Peninsula and East Antarctica data from sediment core ZOL4 taken in a lake on regions. The Ade´lie penguin populations in East Zolotov Island. We extracted the bio-elements and Antarctica have shown a sustained increase, while inferred late Holocene Ade´lie penguin occupation those in the Antarctic Peninsula region have and population dynamics. We also compared the decreased (Woehler et al. 2001). These opposite penguin population changes at Zolotov Island with population trends are likely associated with differ- records from Ardley Island in the South Shetland ences in regional climate and environment, such as Islands over the past 1,800 years, and examined sea ice extent and related changes in prey abundance associations with regional climate changes. (Fraser and Hofmann 2003; Forcada et al. 2006). Records of penguin population changes over larger spatial and temporal scales are required to provide a Materials and methods long-term record of natural variability and to under- stand the population responses of Adelie penguins to Study site and sample collection changes in climate and marine ecosystems. The Vestfold Hills is one of the larger East Zolotov Island is located about 10 km southwest of Antarctic oases (Fig. 1), located east of Prydz Bay. the Australian Antarctic Davis Station in Vestfold South Shetla nd Isla nds N 2 km Vestfold Hills 62º10'S Antarctica Fildes Peninsula 68º30'S Ross Sea East Antarctic ice sheet Ardley Island Davis Station 62º12'S DG4 Y2 Grea t Wa ll Sta tion N ZOL4 Sorsdal glacier 5 km 58º59'W 58º56'W 78ºE Fig. 1 Map of the Vestfold Hills and South Shetland Islands, including the sampling sites on Zolotov Island (ZOL4) and Ardley Island (Y2) 123 J Paleolimnol (2011) 45:273–285 275 Hills, East Antarctica (68°390S, 77°520E; Fig. 1). The USA). Standard sediment reference materials were island is about 2 km long and 1.5 km wide, and has a included with every batch of samples. The analytical maximum altitude of 28 m above sea level. It values for major elements and trace elements are possesses a large number of breeding Ade´lie pen- within ±0.5% and ±5% of the certified standards, guins. Sediment core ZOL4 was retrieved from a lake respectively. TC, TN and S were measured by vario near a large Ade´lie penguin colony. The catchment is EL III (Elementar, Germany) with a relative error of located in a low-lying basin at the center of this 0.1%. island, and is about 120 m long and 55 m wide. It lies We ran R-mode clustering analysis, Principal at an altitute of *7 m. During field investigations, Component Analysis (PCA) and Pearson correlation the lake was very shallow. A 12-cm-diameter PVC analysis on these data using SPSS16.0, to examine pipe was pushed vertically into the deepest part of the the relationship between element concentrations in lake to collect the sediment core. After the PVC pipe the sediments and their controlling factors. The was retrieved, its bottom and top were sealed. In the concentration data of fresh penguin guano and laboratory, the 40-cm core was opened and sectioned bedrock at nearby Gardner Island were also included at 1-cm intervals. Penguin remains such as bones, in this study to help discern the bedrock signature feathers and eggshell fragments were found in the from that of penguin guano. upper 17 cm, and hand picked. The 40 subsamples were stored frozen prior to analysis. Before chemical analyses, each subsample was air-dried in a clean Results laboratory and homogenized. Sedimentology and chronology Radiocarbon dating and geochemical analyses Sediment core ZOL4 is 40 cm long. Two sedimen- We dated four fossil penguin bones (collagen) and tary units were identified from macroscopic descrip- two bulk sediment samples (organic carbon) by tion, color, smell and sedimentology (Fig. 2). Unit 1 Accelerator Mass Spectrometry (AMS) 14C to estab- extends from the base to 17 cm, and is characterized lish the depth/age profile for core ZOL4. Dates on by dominance of greyish deposits consisting of fossil bone were corrected for the marine carbon mainly sand, a moderate amount of silt, and some reservoir effect using the dataset of Marine04 (Hug- small gravels. Unit 2 spans from 17 cm to the hen et al. 2004) to give a DR 880 ± 15 years, the age surface and consists of olive to dark olive grey of local modern penguin bone (Huang et al. 2009b), sediment, which compared with Unit 1, has more and calibrated using the CALIB 5.1.0 program silt and clay. Unit 2 also contains many physical (Stuiver et al. 2005). In this study, the calibrated penguin remains such as bones, feathers and 14C dates were reported in calendar years before eggshells, and has a strong smell of penguin guano, present (cal yr BP). and is identified here as a penguin ornithogenic All air-dried subsamples were measured to sediment layer, i.e. sediments that contain penguin determine the concentrations of 16 major and trace guano and body remains. Unit 1 has a distinct elements (P (P2O5), S, Cu, Zn, Ni, Cd, Pb, K (K2O), sedimentology compared with Unit 2, and it is Na (Na2O), Ca (CaO), Mg (MgO), Fe (Fe2O3), Al unlikely amended by penguin guano.