Living coccolith assemblages of surface sediment samples from the Pacific sector of the Southern Ocean

This study examined recent coccolith surface sediment assemblages across the Pacific sector of the Southern Ocean (from Punta Arenas, Chile toWellington, New Zealand). Twenty five stations located within 44.4°S to 65.4°S and 80.1°W to 174.5°E were selected in order to assess if and how the surface sediment assemblages reflect the present-day coccolithophore community and surface-water oceanographic conditions. The highest numbers of coccoliths in the surface sediments are reached near the East Pacific Rise and close to the Subtropical Front, at the New Zealand Margin (>6x109 coccoliths/g of sediment). The dominant taxa are Emiliania huxleyi (including types A, B, B/C and C), Calcidiscus leptoporus, Gephyrocapsa spp. (including G. muellerae, G. oceanica and G. ericsonii), Umbellosphaera tenuis and Coccolithus braarudii. Despite the recognition of species morphotypes being hampered by carbonate dissolution at some locations, we observed that numbers generally decrease southward until almost a monospecific and sporadic record of E. huxleyi (types B/C and C) and C. leptoporus south of the Polar Front occurs. The recent coccolithophore distribution was compared to already published living coccolithophore distributions (i.e., water column samples collected at the same specific locations) showing a fairly similar pattern. Combining the numbers of cells/l and coccoliths/g of sediment, different coccolithophore assemblages were established coincidentwith areas bounded by the major surface oceanographic fronts, i.e. the Subantarctic Zone and the Polar Front Zone.

本研究针对南大洋太平洋扇区（智利蓬塔阿雷纳斯至新西兰惠灵顿一线）的表层沉积物中的现代颗石组合开展了系统调查。
本研究选取了分布于南纬44.4°至65.4°、西经80.1°至东经174.5°范围内的25个采样站位，旨在评估表层沉积物中的颗石组合能否反映现代颗石藻（coccolithophore）群落结构与表层海水海洋环境状况，以及其反映的具体机制。
表层沉积物中颗石丰度最高值出现于东太平洋海隆附近以及新西兰陆架边缘的亚热带锋面区域，最高可达6×10^9颗石/克沉积物。
优势类群包括赫氏颗石藻（Emiliania huxleyi，包含A、B、B/C及C型）、细薄钙盘球藻（Calcidiscus leptoporus）、桥石藻属（Gephyrocapsa spp.，包含G. muellerae、G. oceanica及G. ericsonii）、细伞球藻（Umbellosphaera tenuis）以及布氏颗石藻（Coccolithus braarudii）。
尽管部分区域的碳酸盐溶解作用会干扰物种形态型的识别，但整体而言，颗石丰度整体呈现向南递减的趋势，在极锋以南区域仅零星出现以赫氏颗石藻B/C型、C型以及细薄钙盘球藻为优势的单优种组合。
本研究将现代表层沉积物颗石组合的分布数据与已发表的同站位水体样品中的现生颗石藻分布数据进行比对，发现二者分布模式高度相似。
结合活体颗石藻细胞浓度（个/升）与沉积物颗石丰度（颗石/克沉积物），本研究建立了与主要表层海洋锋面（即亚南极带与极锋带）所划定区域相匹配的不同颗石组合类型。