Data from: Exploring photosymbiotic ecology of planktic foraminifers from chamber-by-chamber isotopic history of individual foraminifers

Abstract.-Evolution of photosymbiotic ecology is an important adaptation for planktic foraminifers that enhances the ecological advantage of living in oligotrophic oceans. Therefore, detecting photosymbiotic ecology in fossil species is one of the keys to understanding the paleobiodiversity dynamics of planktic foraminifers. Because foraminiferal tests record the ontogenetic history of ecological information in geochemical signatures, analyzing individual geochemical profiles with growth can reveal a species' ecology. This study examined chamber-by-chamber stable isotopes (δ13C and δ18O) of foraminiferal individuals to identify photosymbiotic signals. We observed an ontogenetic δ13C increase of up to 2.4‰, accompanied by relatively stable, negative δ18O, in the symbiotic species Globigerinoides conglobatus and Globigerinoides sacculifer. In contrast, δ13C and δ18O showed significant positive correlation during ontogeny in the asymbiotic species Globorotalia truncatulinoides. These two ecological groups produce contrasting isotopic profiles, thereby allowing us to use our ontogenetic isotopic analyses of individual specimens to identify algal photosymbiosis in fossil foraminifers. The chamber-by-chamber isotope analyses with individual ontogeny have great advantages in analyzing rare species because only one individual is required to describe ontogenetic isotopic history. In addition to photosymbiotic identification, our methods hold great potential to provide new insight into species paleoecological studies such as the ontogenetic history of calcification depth.

摘要：光合共生生态（photosymbiotic ecology）的演化是浮游有孔虫（planktic foraminifers）的一项重要适应性特征，可增强其在贫营养海洋中生存的生态优势。因此，在化石物种中检测光合共生生态特征，是理解浮游有孔虫古生物多样性动态的关键之一。
由于有孔虫壳体（foraminiferal tests）会将生态信息的个体发育历史记录于地球化学特征中，通过分析伴随生长过程的单一个体地球化学剖面，可揭示物种的生态类型。本研究针对有孔虫个体开展逐房室稳定同位素（stable isotopes，δ¹³C与δ¹⁸O）分析，以识别光合共生信号。
研究观察到，共生种球室球旋虫（Globigerinoides conglobatus）与泡抱球虫（Globigerinoides sacculifer）在个体发育过程中，δ¹³C最高可升高2.4‰，同时伴随相对稳定的负δ¹⁸O值。与之相反，非共生种截圆拟抱球虫（Globorotalia truncatulinoides）的δ¹³C与δ¹⁸O在个体发育阶段呈现显著正相关。
这两类生态类群呈现出截然不同的同位素剖面特征，因此可通过对单个标本的个体发育同位素分析，识别化石有孔虫中的藻类光合共生现象。逐房室结合个体发育的同位素分析方法在珍稀物种研究中具备显著优势，因为仅需单个个体即可描述其个体发育同位素历史。
除光合共生识别外，该方法还有望为物种古生态学研究提供新视角，例如钙化深度（calcification depth）的个体发育历史。