【作者】 黄涛；

【导师】 孙立广；

【作者基本信息】 中国科学技术大学 ， 环境科学， 2010， 博士

【摘要】 了解过去是认识现在、预测未来的重要基础。阿德雷企鹅和南极毛皮海豹是南大洋食物链顶端捕食者,其种群生态表现与南大洋气候环境变化密切相关,是南大洋生态系统状态的指示计。研究历史时期企鹅、海豹的生态变化有助于更好地认识未来全球变化影响下的南大洋生态系统中上层生物种群的发展趋势。但是有关南极企鹅、海豹生态变化的研究一直以野外调查和卫星遥感观测为手段,缺乏其长期的生态变化资料。南极无冰区生态地质学是以生物粪土层为过去生态环境信息载体,应用第四纪地质学、元素和同位素地球化学、沉积学、矿物学、构造地质学等经典的地质学方法与生态学、古气候学、动植物学、微生物学、有机化学以及高新技术等多学科交叉的方法,运用微观的生物地球化学记录,结合海平面变化、构造变动等地形地貌典型特征的现场调查,来探索宏观的生态、气候与环境变化的科学问题。本文对东南极西福尔丘陵阿德雷企鹅粪土沉剖面(DG4和ZOL4)、阿曼达湾帝企鹅粪土沉积剖面(PI)和南极半岛西北部法尔兹半岛毛皮海豹粪土沉积剖面(HN1)开展生态地质学研究,探讨了全新世以来南极企鹅、海豹的种群生态变化及其对南极、南大洋气候环境变化的响应,为了解未来南极生态环境变化趋势提供科学依据,涉及到的主要内容摘要如下：1.企鹅粪指示计的选择及其区域对比对东南极西福尔丘陵阿德雷企鹅粪土沉积剖面DG4以及当地新鲜企鹅粪和风化母岩开展了元素地球化学分析,提取出该地区阿德雷企鹅粪的标型元素组合为：P、Se、F、S、As、Cu和Sr。对比分析了该地区与南极乔治王岛阿德雷岛两地新鲜企鹅粪和风化母岩中标型元素的浓度特征后发现,P和Se元素是东南极西福尔丘陵阿德雷企鹅粪更精确的指示计,而南极乔治王岛阿德雷岛企鹅粪的精确指示计为F、P和S。两地企鹅粪指示计的差异主要源于地球化学背景的差别和企鹅食谱的区域差异,阿德雷岛企鹅的食物以南极磷虾为主,所以其排泄物中F元素富集最高；东南极阿德雷企鹅的主要食物除磷虾外,鱼类占据了相当的比例,因此其排泄物中F元素的富集程度没有P和Se高。Se和S元素作为两地企鹅粪的精确指示计主要是由于它们受当地风化母岩背景影响很小。2.全新世东南极西福尔丘陵阿德雷企鹅的登陆及其种群数量演变对东南极西福尔丘陵阿德雷企鹅粪土沉积剖面中的企鹅残骨、羽毛进行了AMS14C定年,结果表明阿德雷企鹅在距今8500年前登陆该Gardner岛,对应于该地区南部陆地冰川的消退,在距今2900年前的晚全新世温暖期,企鹅登陆了Magnetic岛,在距今1800年的新冰期结束前后,阿德雷企鹅登陆Zolotov岛。对企鹅粪土沉积剖面DG4和ZOL4展开研究,利用指示计反演出沉积剖面中企鹅粪的相对含量,进而恢复了Gardner岛过去8500年和Zolotov岛过去1800年来阿德雷企鹅种群数量的变化记录。结果显示,Gardner岛阿德雷企鹅种群数量在距今4700-2400年间达到峰值,对应于晚全新世气候适宜期；而在距今约300年前的小冰期阶段,Zolotov岛的阿德雷企鹅种群数量显著下降。阿德雷企鹅在西福尔丘陵的登陆历史及其种群数量变化都显示其对气候环境变化的灵敏响应。3.东南极阿曼达湾帝企鹅种群数量的潜在记录对东南极阿曼达湾帝企鹅粪土沉积PI开展了生态地质学研究。对PI剖面的210Pb、137Cs定年表明其年龄约为240年；分析了沉积物中TC、TN、TS、TH、P、Hg、Se、Cu、Zn和Pb等元素的浓度剖面变化,发现TC、TN、TH、P、Hg、Se、Cu和Zn等生源元素之间具有显著的相关性且其浓度远高于其在当地基岩中的含量,而Pb与这些元素呈显著的负相关关系,表明前者很可能主要来源于帝企鹅粪的输入而Pb则来自于当地的母岩风化。因此,TC、TN、TH、P、Hg、Se、Cu和Zn的浓度剖面变化指示了PI中帝企鹅粪的相对含量进而指示了在该集水区活动的幼年帝企鹅数量,同时也反映了该地区帝企鹅种群数量的总体情况。过去240年来该区帝企鹅数量总体呈波动下降的趋势,有趣的是监测数据显示随着南印度洋不断变暖,东南极过去50年来帝企鹅种群数量也是不断降低的。本研究表明东南极阿曼达湾帝企鹅数量在240年来发生了较大的波动,而生态地质学方法在一些特定的区域可以用于重建历史时期帝企鹅种群数量变化。4.历史时期阿德雷企鹅、毛皮海豹食谱营养级的变化记录及其生态意义现代南极阿德雷企鹅和毛皮海豹的主要食物是南大洋关键种南极磷虾,因此它们的食谱营养级变化与南大洋磷虾丰度密切相关。研究历史时期阿德雷企鹅、毛皮海豹的食谱营养级变化有助于理解过去南大洋食物链的动态变化。以粪土沉积物及其中的企鹅残骨、羽毛和海豹毛为载体,利用稳定C、N同位素指标研究了东南极阿德雷企鹅过去8000年来,南极法尔兹半岛毛皮海豹20世纪以来食谱营养级变化。结果表明：现代阿德雷企鹅羽毛、骨骼的N同位素值与历史值存在着显著的差别,历史时期阿德雷企鹅营养水平较现代要高,同时历史时期同位素值也存在着明显的变化,气候温暖时期企鹅营养级较高,相对冷期时营养级较低,现代(约200年前)阿德雷企鹅较低的营养级源自于其捕食大量磷虾,这可能主要是由于人类大量的猎杀海豹和捕鲸活动造成了磷虾的相对丰盛,而历史时期阿德雷企鹅营养级的变化可能主要与受气候、海冰变化影响显著的磷虾种群动态变化有关；20世纪以来南极法尔兹半岛毛皮海豹的营养级呈显著上升趋势,对应着此时间段显著变暖的南大洋,而监测数据显示,过去30年来南极半岛附近海域海冰面积和磷虾种群密度不断减少,与海豹营养级呈显著负相关关系,表明不断变暖的南大洋和减弱的海冰密集度极有可能造成了南极磷虾种群密度的下降,降低了其在毛皮海豹食谱中的比例,导致海豹营养水平不断上升。本研究表明,南极磷虾的种群动态是阿德雷企鹅和毛皮海豹食谱营养级变化的主要因素,因此可以通过对阿德雷企鹅和毛皮海豹等krill predator的长期营养级变化研究来探讨过去南极磷虾的种群动态及其对气候和环境变化的响应,这对深入理解历史时期南大洋生态系统变化至关重要。5.阿德雷企鹅种群生态的环南极对比及其对气候环境变化的响应对比分析了全新世以来阿德雷企鹅在环南极地区的登陆历史及其种群数量演变,发现在气候温暖、冰川消退、无冰区出露时期往往伴随的阿德雷企鹅的登陆,在晚全新世气候适宜时期东南极、南极半岛和罗斯海湾地区阿德雷企鹅种群数量都处于峰值,而在新冰期和小冰期时段东西南极岛屿企鹅数量均明显下降。前人的研究表明阿德雷企鹅对南极气候变化的响应机制主要体现在两个方面：气候变化引起的企鹅繁殖、脱毛和取食地物理环境的改变；气候环境影响下的食物丰度。综合本文及前人的研究成果和现代阿德雷企鹅种群、气候环境的监测数据表明：极端冷暖气候均不利于企鹅种群的发展,在气候适宜期时有更多的无冰区出露供企鹅繁殖、脱毛,适宜期较高海洋生产力也能提供丰富的食物资源,企鹅种群数量增加；冰期时,企鹅原来的繁殖、脱毛的巢穴可能被陆地冰和积雪覆盖,失去繁殖的机会,同时冰期时海冰面积增大,企鹅捕食更加困难,企鹅种群数量减少；近年来南极半岛阿德雷企鹅数量的减少主要是由于气候显著变暖,影响了其捕食环境(海冰大面积减少不利于企鹅捕食)和食物种群丰度(磷虾种群密度下降)。更多还原

【Abstract】 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.更多还原