Organic Geochemical Researches On Ecology Of Penguin And Seal In Circum Antarctica

Adélie penguin and fur seal are the top predators in the food chains of Southern Ocean and they are sensitive to the environmental changes. Therefore they are indicators of the Southern Ocean status. Rearches on the historical changes of ecosystems of penguins and seals contribute to a better understanding of the influences of global changes to the ecosystem of Sounthern Ocean. And the current methods of researching on the Antarctic penguins, seals ecological responses are field survey, satellite remote sensing methods, biogeochemical records and the istopes of N and Sr. But the works which are using organic geochemistry method are few.In the present study, we perform organic geochemic analyses on the Adélie penguin ornithogenic sediment core DG2 and MB4 in Vestfold Hills and Ross Island, East Antarctica separately, and fur seal excrement sediment core HN1 in Fieldes Peninsula, combine with geology and ancient climate, ecology, animal and plant science and other interdisciplinary approach, study the organic geochemistry and ecological history of the three regions around the Antarctica. By combine with changes of climate and development of human civilization, we can explore the problems between climate and environmental changes, biological responses to environmental and sea birds, sea animals on the colonies by using micro-ecological biogeochemistry. And these researches provide the scientific basises for future ecological researches and the researches of climate of the Antarctic ring. The main contents are summarized as follows:1. The evolution of penguin colony on Vestfold Hills, East AntarcticaWe collected an ornithogenic sediment core DG2 from Gardner Island in Vestfold Hills, East Antarctica, and reconstructed an 8,500 years variation history of penguin population and vegetation abundance on this island, and examined the evolution of the penguin colony. The results showed that the aliphatic hydrocarbons were mainly consisted of short-chain n-alkanes which likely derived from freshwater algae and bacteria. Meanwhile, the even-carbon fatty acids, such as n-C₁₆, n-C₁₈ and n-C₂₄, dominated alkenoic acids and they principally originated from bacteria, freshwater moss or zooplankton. However, unsaturated fatty acids were predominated by C_18:1 acid from freshwater algae to show good preservation and simple sourses of the sediments but trace amount in it. Furthermore, the concentrations of cholestanol, cholesterol and phytol which came from penguin excrements and vegetation were high in the alcohols and the fluctuations of them in the lake core might respond to the historical changes of penguin populations and vegetations. We used the levels of two molecular markers cholesterol and cholestanol as the proxy indicators of penguin population size. Other molecular markers, including C_24:0 alkenoic acids, C₁₈ n-alkanol and phytol were used as the proxy indicators of aquatic moss, algae, and general vegetation respectively. It's shown that the growth of algae was mainly affected by the nutritional supply from penguin droppings, so their abundance was positively linked with penguin population. The growth of aquatic moss, however, was controlled more by the degree of water body transparency than by nutrient availability. Because the pollution of water body increased as penguin population grew, aquatic moss abundance showed a seesaw-like relationship with penguin population. These results suggested that penguins played a dominant role in this simple ecosystem in the Antarctic environment. The reconstructed relationship between penguin population and vegetation abundance may offer new insights to understand ancient Antarctic environment and ecology.2. The evolution of seal colony on Fieldes Peninsula, West AntarcticaWe collected a sediment core HN1 from the Fieldes Peninsula of West Antarctica, and performed organic geochemical analysis on it. Short-chain n-alkanes were the main components of aliphatic hydrocarbons, and they were likely derived from algae and bacteria; n-C₂₃ was likely from moss. Fecal sterols and phytol respectively came from seal feces and vegetation, they were dominant in the alcohol compositions, and their fluctuations likely responded to historical changes of the ecosystem near the sediment. The even-carbon fatty acids, such as n-C₁₆, n-C₁₈ and n-C₂₄, dominated the alkenoic acid compositions, and they mainly originated from bacteria, moss and zooplankton. The concentrations of unsaturated fatty acids were low and predominated by C_16:1 and C_18:1 unsaturated acids, and this showed that the sediment was well preserved and had a simple and stable source of organic materials. We used cholesterol, cholestanol, epicoprostanol, coprostanol, and seal hair numbers as the proxy indicators of seal population size and phytol as of general vegetation, and we reconstructed the 20^th century history of variation of the seal population and vegetation abundance on this island. In this study, The sealing industry in the early 20^th century caused the dramatic decline of seal population, and the ban of seal hunting since the 1960s led to its recovery of seal population. The seal population during the past century was primarily controlled by human activities and krill density. The reconstructed relation between seal population and vegetation abundance may offer new insights into Antarctic environment and ecology.3. The evolution of penguin colony on Ross Island, East AntarcticaWe collected an ornithogenic sediment core MB4 from Cape Bird in Ross Island, East Antarctica, and reconstructed an 1,120 years variation history of penguin population and vegetation abundance on this island, and examined the evolution of the penguin colony. The results showed that the aliphatic hydrocarbons were mainly consisted of long-chain n-alkanes which likely derived from mosses. Meanwhile, the even-carbon fatty acids, such as n-C₁₆ and n-C₂₄, dominated alkenoic acids and they principally originated from bacteria, freshwater moss or zooplankton. Furthermore, the concentrations of cholestanol, cholesterol and phytol which came from penguin excrements and vegetation were high in the alcohols and the fluctuations of them in the lake core might respond to the historical changes of penguin populations and vegetations. We used the levels of cholesterol and cholestanol, phytol, nC₁₆-ol, nC₂₂-ol and nC₂₈-ol as the proxy indicators of penguin population size, vegetable, algae, moss and lichen respectively. These results suggested that penguins played a dominant role in this simple ecosystem in the Antarctic environment. The reconstructed relationship between penguin population and vegetation abundance may offer new insights to understand ancient Antarctic environment and ecology.4. The contrast and analysis of biomarkers in different fields on AntarcticaWe analyzed three sediment profiles around Antarctica by using biomarkers: Adélie penguin ornithogenic sediment core DG2 and MB4 in Vestfold Hills and Ross Island, East Antarctica separately, and fur seal excrement sediment core HN1 in Fieldes Peninsula. By analyzing the distribution of biomarkers in the three sediments, we could research on the differents of plants around the research areas and the distribution of differents biomarkers. Hydrocarbons, alcohols and acids are more impacted by the environment and the input of plants. Sterols are impacted by the origines of differental animals'fecals. Therefore sterols can distinguish differental animals and reconstruct the changes of population in history. By comparison, the sedimentary biomarkers provide more comprehensive informations, improve the understanding of sediments, deepen the understanding of the evolutions of regional ecologic and environment.