The Southern Ocean is warming faster than the average global ocean and is particularly vulnerable to ocean acidification due to its low temperatures and moderate alkalinity. Coccolithophores are the most productive calcifying phytoplankton and an important component of Southern Ocean ecosystems. Laboratory observations on the most abundant coccolithophore, Emiliania huxleyi, suggest that this species is susceptible to variations in seawater carbonate chemistry, with consequent impacts in the carbon cycle. Whether anthropogenic environmental change during the industrial era has modified coccolithophore populations in the Southern Ocean, however, remains uncertain. This study analysed the coccolithophore assemblage composition and morphometric parameters of E. huxleyi coccoliths of a suite of Holocene-aged sediment samples from south of Tasmania. The analysis suggests that dissolution diminished the mass and length of E. huxleyi coccoliths in the sediments, but the thickness of the coccoliths was decoupled from dissolution allowing direct comparison of samples with different degree of preservation. The latitudinal distribution pattern of coccolith thickness mirrors the latitudinal environmental gradient in the surface layer, highlighting the importance of the geographic distribution of E. huxleyi morphotypes on the control of coccolith morphometrics. Additionally, comparison of the E. huxleyi coccolith assemblages in the sediments with those of annual subantarctic sediment trap records found that modern E. huxleyi coccoliths are ∼2% thinner than those from the pre-industrial era. The subtle variation in coccolith thickness contrasts sharply with earlier work that documented a pronounced reduction in shell calcification and consequent shell-weight decrease of ∼30-35% on the planktonic foraminifera Globigerina bulloides induced by ocean acidification. Results of this study underscore the varying sensitivity of different marine calcifying plankton groups to ongoing environmental change.

南部海洋的变暖速度快于全球平均海洋，并且由于其低温和适度的碱度，特别容易受到海洋酸化的影响。球隐藻是生产力最高的钙化浮游植物，是南部海洋生态系统的重要组成部分。对最丰富的球石藻，Emililiia huxleyi的实验室观察表明，该物种易受海水碳酸盐化学变化的影响，从而影响了碳循环。然而，在工业时代的人为环境变化是否已经改变了南大洋中的球石藻种群，尚不确定。本研究分析了赫氏大肠杆菌的球囊石组合组成和形态计量学参数。塔斯马尼亚南部的一套全新世时代沉积物样本的球石。分析表明，溶解减少了沉积物中E. huxleyi球藻的质量和长度，但球藻的厚度与溶解分离，因此可以直接比较具有不同保存度的样品。球藻厚度的纬度分布模式反映了表层中的纬度环境梯度，突出了霍克斯利氏菌形态型的地理分布对控制球藻形态学的重要性。此外，通过比较沉积物中E. huxleyi球藻组合物和年度南极沉积物陷阱记录的结果，发现现代赫克斯利肠球菌比工业化前时代的骨膜薄约2％。球藻厚度的细微变化与早期的研究形成鲜明对比，早期的研究表明，由于海洋酸化引起的浮游有孔虫Globigerina Bulloides的壳钙化明显减少，其壳重减少了约30-35％。这项研究的结果强调了不同的海洋钙化浮游生物对不断变化的环境的敏感性。