Abundance of organic-walled dinoflagellate cysts in surface sediments from the Atlantic sector of the Southern Ocean (Appendix 2)

Thirty-two surface sediment samples from the Southern Ocean (eastern Atlantic sector), between the Subtropical Front and the Weddell Gyre, were investigated to provide information on the distribution of modern organic-walled dinoflagellate cysts in relation to the oceanic fronts of the Antarctic Circumpolar Current (ACC). A clearly distinguishable distribution pattern was observed in relation to the water masses and fronts of the ACC. The dinoflagellate cysts of species characteristic of open oceanic environments, such as Impagidinium species, are highly abundant around the Subtropical Front, whereas south of this front, cosmopolitan species such as Nematosphaeropsis labyrinthus and the cysts of Protoceratium reticulatum characterise the transition from subtropical to subantarctic surface waters. The subantarctic surface waters are dominated by the cysts of heterotrophic dinoflagellates, such as Protoperidinium spp. and Selenopemphix antarctica. The cysts of Protoperidinium spp. form the dominant part of the assemblages around the Antarctic Polar Front, whereas S. antarctica concentrations increase further to the south. The presence of S. antarctica in sediments of the Maud Rise, a region of seasonal sea-ice cover, reflects its tolerance for low temperatures and sea-ice cover. A previously undescribed species, Cryodinium meridianum gen. nov. sp. nov., has a restricted distribution pattern between the Antarctic Polar Front and the ACC-Weddell Gyre Boundary.本研究对南大洋大西洋东部海域——即亚热带锋面（Subtropical Front）与威德尔海环流（Weddell Gyre）之间的区域——采集的32个表层沉积物样品开展分析，旨在阐明现代有机壳甲藻孢囊（organic-walled dinoflagellate cysts）的分布特征，及其与南极绕极流（Antarctic Circumpolar Current, ACC）各海洋锋面的关联。研究观测到清晰可辨的分布格局，该格局与南极绕极流相关的水团及锋面分布高度对应。开放海洋环境特征种的有机壳甲藻孢囊（如铠甲藻属（Impagidinium）物种）在亚热带锋面附近丰度极高；而该锋面以南，广布种如迷宫丝囊藻（Nematosphaeropsis labyrinthus）与网状原角藻（Protoceratium reticulatum）的孢囊，共同表征了亚热带表层水向亚南极表层水的过渡过程。亚南极表层水中，异养型甲藻（heterotrophic dinoflagellates）的孢囊占据优势类群，包括原多甲藻属（Protoperidinium）物种与南极硒鞭藻（Selenopemphix antarctica）。在南极极地锋（Antarctic Polar Front）附近的孢囊组合中，原多甲藻属物种的孢囊为优势类群；而向南延伸区域中，南极硒鞭藻的丰度进一步升高。在季节性海冰覆盖的毛德海隆（Maud Rise）区域沉积物中检出南极硒鞭藻，反映了该物种对低温与海冰覆盖环境的耐受性。本次研究还发现了一个此前未被描述的新属新种Cryodinium meridianum gen. nov. sp. nov.，其分布范围局限于南极极地锋与南极绕极流-威德尔海环流边界之间的区域。