报告时间：2019年9月4日（星期三）下午 15:00-16:00
报告地点：天津大学，第16教学楼221报告厅
报告题目：Application of biogenic calcium carbonate to assess ocean acidification
主讲嘉宾：Dr. Kentaro Tanaka (Atmosphere and Ocean Research Institute, The University of Tokyo)
嘉宾简介：Kentaro Tanaka 博士，目前担任东京大学大气与海洋研究所博士后研究员。2011年，毕业于日本琉球大学，获得理学博士学位。2011年-2014年，分别在日本琉球大学、澳大利亚西澳大学和日本北海道大学从事博士后研究；2014年-2017年，入选日本学术振兴会（JSPS）博士后特别研究员计划。Tanaka 博士的研究兴趣涵盖古海洋学、珊瑚礁生态学、气候变化以及地球化学等多个研究领域，擅长珊瑚礁钻孔样品采集、EPMA和NanoSIMS固体样品制备、生物碳酸盐矿物主量-微量元素和稳定同位素分析，在Coral Reefs、Chemical Geology、Applied Geochemistry、Rapid Communications in Mass Spectrometry、Geochemical Journal等期刊发表多篇学术论文。
报告摘要：
Hard tissues (e.g. skeletons and shells) produced by the marine calcifying organism (such as corals, bivalves, and foraminifera) are composed of calcium carbonate. Chemical compositions of these biogenic calcium carbonates reflect environmental variability of the oceans. Some of the biogenic calcium carbonates form growth banding patterns (like “tree rings”) with daily to annual resolution. Thus, the combined analyses of chemical compositions and the growth patterns can provide the broad information on the ocean environments (temperature, salinity, pH and pollution, etc.) with the detailed chorology, compensating for the lack of oceanographic observation.
In parallel with global warming, ocean acidification is in progress due to the increasing anthropogenic CO2 emission. Based on the theoretical relationship between boron isotopic ratios in CaCO3 and pH of the parent solution where the CaCO3 crystal is precipitated, boron isotopic ratios in coral skeletons were once thought to directly record seawater pH. Several studies estimated the seawater pH using the boron isotope ratio of long-lived coral skeletons to better understand the progress of ocean acidification after the 19th century. In this talk, seawater pH derived from the boron isotopes in the coral skeleton from the northern limit of their habitat will be presented.
Recent geochemical/biological studies revealed that corals produce their skeleton in the “calcifying fluid”, of which the pH value is inherently modified by biological processes. Thus, the boron isotopic ratio in the coral skeleton records the pH value in the calcifying fluid rather than ambient seawater pH, limiting the application of coral skeleton as an archive of paleo-pH. Considering such a biological bias related to coral metabolism, boron isotopic ratios of biogenic CaCO3 beside coral skeleton was also measured to seek a robust archive of paleo-pH in the ocean. The latest collaborative works on boron isotopic composition in other calcifying species will be also presented in this talk.
