Coccolithophore ecology and biogeography in the Southern Indian Ocean was studied during the austral summer of 2009 (SOE09; late austral summer), 2010 (SOE10; mid-austral summer), and 2012 (ISEA12; early austral summer). During the SOE09 and SOE10, surface water samples (55 and 54 water samples, respectively) were collected from two different transects between Mauritius and Antarctica (~48°E; ~57.3°E); whereas during the ISEA12, 22 sea surface water samples were collected between Cape-Town and Prydz Bay. Highest coccolithophore diversity was during SOE10 (36 taxa), followed by SOE09 and ISEA12 (12 and 7 taxa, respectively) whereas, highest coccolithophore abundance was reported during the ISEA12 (up to 2203 × 10³ coccospheres/l) followed by SOE10 (up to 742 × 10³ coccospheres/l) and SOE09 (up to 217 × 10³ coccospheres/l). During each expedition, elevated coccolithophore diversity was documented at the Subtropical zone whereas the highest abundance was recorded at the Subantarctic zone, which was dominated by Emiliania huxleyi. Differences in the occurrence and southward expanse of coccolithophores were documented during each expedition, i.e. maximum southward expanse during the SOE10 and lowest during the ISEA12. We show that, biogeographic boundaries of coccolithophores are highly variable in the Southern Indian Ocean which is controlled by environmental factors in the early and mid-austral summer, and grazing pressure in the late austral summer. In addition, the physical forcing also may play a key role in transport of coccoliths and coccospheres in the high latitudes. We indicate that, southward expanse of coccolithophores is significant and may occur for short periods during austral summer.

在2009年南半球夏季（SOE09；南半球夏季），2010年（SOE10；南半球夏季）和2012年（ISEA12；南半球夏季）进行了南印度洋的球石藻生态学和生物地理学研究。在SOE09和SOE10期间，从毛里求斯和南极洲（〜48°E；〜57.3°E）的两个不同样点收集了地表水样品（分别为55和54个水样）。而在ISEA12期间，在开普敦和普兹湾之间采集了22个海面水样。最高的球石藻多样性在SOE10期间（36个分类单元），其次是SOE09和ISEA12（分别是12和7个分类单元），而在ISEA12期间报道的最高的球石藻丰度（最高为2203×10 ³球囊/升），其次是SOE10（上升至742×10 ³coccospheres / l）和SOE09（最高217×10 ³ coccospheres / l）。在每次探险中，在亚热带地区都记录到球藻石藻的多样性升高，而在亚南极地区则记录了最高的丰度，其中以Emiliaania huxleyi为主。每次探险期间都记录了球石珊瑚的发生和向南扩展的差异，即SOE10期间最大的向南扩展，而ISEA12期间的最小。我们表明，在南印度洋，球墨石生物的生物地理边界是高度可变的，这在南澳大利亚初夏和夏季受到环境因素的控制，而在南澳大利亚夏末则受到放牧的压力。此外，物理强迫在高纬度的球石和球壳的运输中也可能起关键作用。我们表明，球果藻向南扩展很明显，并且可能在南方夏季短时间内发生。