| Understanding the past is the foundation for evaluate the present and predict the future. As the top predators of the Southern Ocean food webs, Adelie penguin and fur seal are sensitive to the Southern Ocean ecosystem variabilities, and thus they are indicators of the Southern Ocean status. Long-term ecological changes of Adelie penguin and fur seal are helpful in understanding their responses to the changing marine ecosystem in future. To date most of the ecological studies on penguins and seals are mainly through the field investigation and the remote sensing technology, long-term ecological records of penguins and seals, however, are scarce.The eco-geology of the Antarctic ice-free areas is focus on the past ecological and environmental changes in Antarctica, using animal excrements as the new indicators. It combines the applications of quaternary geology, elemental and isotope geochemistry, sedimentology, mineralogy, geotectonics, geomorphology and ecology, paleoclimatology, biology, organic chemistry as well as new technologies to study the macro ecological, climatic and environmental changes in Antarctica from the micro biogeochemical records, sea level change and the topography. In the present study, we perform eco-geological analyses on the Adelie penguin ornithogenic sediment cores (DG4 and ZOL4) in Vestfold Hills, East Antarctica, emperor penguin ornithogenic sediment core (PI) in Amanda Bay and fur seal excrement sediment core (HN1) in Fieldes Peninsula, study the Holocene ecological changes of Adelie penguins and fur seals and their biological responses to the past changes of climate and environment in Antarctica and the Southern Ocean, and thus to provide the foundation for understanding the penguin and seal performance in the changing Antarctic. The main contents are summarized as follows:1 Identification of indicators of penguin guano from ornithogenic sedimentsWe performed elemental concentration analyses on the ornithogenic sediments DG4, penguin guano and bedrock from Gardner Island, Vestfold Hills, extracted the bio-elements of penguin guano as P,Se,F,S,As,Cu and Sr. We compared the concentrations of guanos and bedrocks in this area and those of Ardley island and found that P and Se are optimal indicators of penguin guanos in Vestfold Hills while those in Ardley island are F, P and S, which are due to the different geochemical backgrounds and dietary compositions of penguins in above two areas.2 Holocene Adelie penguins occupation and population dynamics in Vestfold In order to reconstruct the occupation history of Adelie penguin in Vestfold Hills, we performed radiocarbon dating on the penguin fossil bones and feathers of the ornithogenic sediment cores (DG4, ZOL4, DM3 and RI) from west coastal islands in Vestfold Hills. The calibrated 14C dates of penguin remains in the bottom of the sediment cores indicate that in Vestfold Hills:Adelie penguin occupied Gardner Island in 8500 years before present, corresponding to a period of the land-ice retreat; during the late-Holocene climate optimum, penguin occupied Magnetic island in-2900 years before present and at the end of the neoglaciation around 1800 years before present, Adelie penguin occupied Zolotov island. We inferred the Adelie penguin population dynamics at Gardner island over the past 8500 years and Zolotov island over the past 1800 years, by using the penguin bio-elements to induce the relative abundance of penguin guano in the bulk sediments which correlate with the local penguin populations. The results show that Adelie penguin populations get their peak in 4700-2400 years before present, corresponding to the late-Holocene climate optimum; during the'Little Ice Age'period around 300 years before present, penguin populations at Zolotov island show dramatic decline. This study demonstrate that both the penguin occupations and population dynamics are sensitive to the climate changes.3 A potential record of emperor penguin populations in Amanda Bay, East AntarcticaDuring CHINARE-24 (December 2007-March 2008), we collected a 14 cm long sediment core PI from a shallow catchment near the emperor penguin colony in Amanda Bay, East Antarctica. The core consists of dark olive grey sediments, fine hairs and some bones, discharge a strong and unpleasant smell of penguin guano, and it is identified as a emperor penguin ornithogenic sediment. The date of PI was estimated as-240 year based on 210Pb and 137Cs dating on the sediments. We analyzed the concentrations of TC, TN, TS, TH, P, Hg, Se, Cu, Zn and Pb in the sediments of PI and local bedrock. TC, TN, TS, TH, P, Hg, Se, Cu and Zn show very high concentration levels in sediments than those in bedrock, and they have very similar vertical profiles, Pb have equivalent content in sediments and bedrock and show opposite pattern with the other 9 elements. Therefore, the high level of TC, TN, TS, TH, P, Hg, Se, Cu and Zn in PI are very likely associate with the penguin guano input and concentrations indicate the relative abundance of guano input in the bulk sediments and thus the juvenile emperor penguin populations, and the similar population dynamics of overall emperor penguins. The inferred emperor penguin populations decrease with fluctuations in the study period. This study indicate that biogeochemical method can be used to infer the past emperor penguin population dynamics in specific areas.4 Past dietary and trophic level changes of Adelie penguin and fur seal and their ecological implicationsAs the krill predators, Adelie penguin and fur seal's trophic level changes are tightly associated with the Southern Ocean food webs and thus indicators of the Southern Ocean ecosystems. We study the trophic level change of Adelie penguins over the past-8000 years and fur seals in the 20th century, by the analyzes of stable carbon and nitrogen isotopes on the penguin and seal remains extracted from lake sediments. The results show that modern bone and feather of Adelie penguin in Vestfold Hills have low nitrogen isotope ratios and thus low trophic levels, and it was due to Adelie penguin's dominant diet:Antarctic krill, which is expected to increase due to the recent removal of whale and seal in Southern Ocean. Adelie penguin trophic levels were high with fluctuation in the past (>150 years), they show relative high level in warm period and low in relative cold time, it could be explained by the climate-related impacts on Antarctic krill and thus penguin trophic levels. For the past-100 years, fur seal's trophic level shows a rising trend, indicating a decline of krill proportion in seal diets and thus a decline of krill density in local oceans. Our results are in excellent agreement with those from direct observation for the past-30 years, and they suggest that the recently documented decline in krill populations began in the early parts of the 20th century. This study indicates that long-term krill population changes can be inferred from long-term variation inδ15N of seal hair and other remnants of krill predators which are crucial for understanding the past and predicting the future of the Southern Ocean ecosystems.5 Circum-Antarctic comparisons of penguin ecological changes and their response to the changes of climate and environment in AntarcticaWe compared the Holocene Adelie penguin occupations and population changes in the circum-Antarctica and found that:Adelie penguins occupied land right after deglaciation and the formation of ice free areas; Adelie penguin populations get their peak in Antarctic Peninsula, Ross Sea and East Antarctica during the late-Holocene climate optimum, and the populations in East Antarctica and Antarctic Peninsula show obviously decline during the Neoglaciation and'Little Ice Age'. Climate affect Adelie populations mainly through two modes:prey availability and suitability of breeding and moulting habitats. During warm climates, island would be exposed adequately and thus provide more suitable breeding and moulting sites for penguins. Warm climates may also increase marine productivity and food supply to support the growth of penguin populations. And vice versa.
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