东北印度洋末次冰盛期以来放射虫的时空分布及其环境变化响应

Under the influence of typical monsoonal climate and several intermediate and deep watermasses, the northeastern Indian Ocean has unique surface salinity contrast and regional deep water environment. Siliceous radiolarians play an irreplaceable role in the deep-sea paleoceanography and paleoclimatology construction. This project is aimed to comprehensive analyze the radiolarians from upper water, surface sediment and down-core sediment, to reveal the regional distribution, living depth and interannual variation of modern radiolarians and their relations with upper ocean environmental change. By analyzing the degree of correlation of radiolarians in recent deposition with those in modern water, we will decipher radiolarian sedimentation and burial preservation and their controlling factors. We will reveal the temporal and spatial changes of radiolarians since the Last Glacial Maximum in the northeastern Indian Ocean and their responses to environmental variables (such as monsoon, temperature, salinity and watermass). Based on the comparison of down-core data among several regions, we try to construct the dynamic evolution characteristics of marine environment, especially watermasses since the Last Glacial Maximum. We will compare the differences and similarities between the northeastern Indian Ocean and the southern South China Sea, to verify and establish a set of alternative proxies for indicating special marine environment which has regional suitability in the tropical low-latitude ocean. Results from this project will fill the gaps and increase new knowledge of regional radiolarians, which will provide new evidence and new method for further recovering evolution histories of paleoenvironment and paleoclimate, and even give some important basically scientific data for further study the deep-sea sediment, regional environment and their responses on global change.

东北印度洋在典型季风气候和多个中深层水团影响下形成了独特的海表盐度变化和区域深水环境。硅质生物放射虫在深海古海洋和古气候研究中发挥着不可替代的作用。本课题拟通过东北印度洋上层水体、表层沉积物和钻孔柱状样的综合研究，揭示现代放射虫的区域分布、深度习性和年际变化，探讨其与上层海洋环境变化的关系；比较近代沉积放射虫与现代放射虫的关联程度，分析放射虫沉降与埋藏保存的影响控制因素；揭示末次冰盛期以来放射虫时空分布及其对海洋环境（如季风、温盐和水团等）变化响应的机制；比较不同区域的钻孔柱状样，尝试重建末次冰盛期以来海洋环境尤其是水团的动态演化特征；阐明东北印度洋与南海南部的区域差异与共性，核实并建立一套与热带低纬度海洋环境演化相适应的替代指标。研究成果不仅将填补空白、增进新认识，而且将为热带低纬度海域古环境和古气候研究提供新证据和新思路，为深海沉积、区域环境及其全球变化响应研究提供重要的基础科学资料。

东印度洋在特殊的地理位置和季风气候控制下形成了独特的环流结构和生物地球化学过程。放射虫因具有不易溶解硅酸盐骨骼而成为古海洋和古环境记录的良好载体。本项目围绕东北印度洋末次冰盛期以来放射虫的时空分布及其环境变化响应展开深入研究，取得一系列突破性的数据结果：首次揭示了东印度洋和跨洋盆之间现代放射虫的多样性、季节变化和生物地理分布格局及其对季风和区域环境的敏感响应；建立了pylonioid类放射虫鉴定的新方法，发现并命名了3个新属和20个新种；识别出东印度洋只生活在透光层的暖水种组合和只生活于中深层的冷水种组合；揭示了东印度洋表层沉积物中放射虫组合分布能够反映局地如活动大峡谷影响区、90ºE海岭、孟加拉湾南部和赤道区等的环境特征；将现代放射虫组合的水团指标应用于海底表层沉积放射虫分析，表明东印度洋近代沉积的放射虫组合对该区域的赤道潜流暖水和南极中层冷水的传播分布有很好的指示意义；研究了典型沉积区即海岭、海底平原、活动大峡谷近端和远端50 ka BP以来的放射虫组合沉积记录；重建了50 ka BP以来不同沉积区的古海洋环境演变特征、及其上层暖水和中深层冷水的可能变化过程。研究成果系统性地填补了东印度洋现代放射虫的多样性和生态学资料，提出新的适用于印度洋古海洋和古水团重建研究的放射虫环境替代性指标。. 目前，已在国内外研究领域主流期刊上发表学术论文6篇（含4篇SCI），另有3篇英文稿在评审中、和若干篇待投或正在撰写中的相关成果文章,更多现代放射虫和沉积放射虫组合所携带的环境信息正在被挖掘提取。培养或协助培养学生4名。项目执行期间参加学术交流活动超过27人次，进行成果交流、讨论合作，极大地拓展了研究视野和思考的维度。依据本项目研究发现的新问题、新方法和新思路，研究人员获得1项新的国家自然科学基金项目，所培养研究生在学术会议中获得优秀墙报三等奖2人次。