Biogeographic differentiation between two morphotypes of the Southern Ocean diatom Fragilariopsis kerguelensis
Biogeographic differentiation between two morphotypes of the Southern Ocean diatom Fragilariopsis kerguelensis
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DOI：
10.1007/s00300-019-02525-0
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发表时间：
2019-07-01
期刊：
影响因子：
1.7
通讯作者：
Beszteri, Bank
中科院分区：
文献类型：
--
作者：
Glemser, Barbara;Kloster, Michael;Beszteri, Bank
易碎棘猴（O' Meara）是南大洋中普遍存在的硅藻。它的厚截体是覆盖海底大部分的硅质沉积层的主要组成部分。该硅藻体的形态变异对古环境重建具有重要意义。最近，在南大洋沉积物岩心中描述了两种由形态测量描述符矩形区分的形态型，其相对丰度与重建的古温度有关。在本研究中，我们使用半自动显微镜和图像分析方法来回答这些形态是否也出现在最近的组合中，如果是，它们的分布是否反映了地理位置或环境因素。我们分析了沿格林尼治子午线用手网取样的三个水柱样带和南太平洋的一个沉积物表面样带。在每个样带中都检测到这两种形态，并且发现年平均海面温度（SST）是它们相对丰度的一个很好的预测因子。在南极极锋和南极环极流南边界之间，大致出现了一种或另一种形态优势的转变。虽然需要更广泛的环极地采样来证实我们结论的普遍性，但观察到的形态测量跃变是该物种生物学的一个新方面，未来可能用于进一步开发古代用物，特别是在南大洋中以f.k erguelensis为主的沉积物。
Fragilariopsiskerguelensis (O' Meara) Hust. is a ubiquitous diatom of the Southern Ocean. Its thick frustules are the numerically dominant component of the siliceous sediment layer covering large parts of the seafloor beneath. Morphometric variability of frustules of this diatom has been of interest for paleoenvironmental reconstructions. Recently, two morphotypes differentiated by the morphometric descriptor rectangularity were described from a Southern Ocean sediment core, the relative abundance of which correlated with reconstructed paleotemperatures. In the present study, we use semi-automated microscopic and image analysis methods to answer whether these morphotypes also appear in recent assemblages, and if yes, do their distributions reflect geographic location or environmental factors. Three transects from the water column, sampled along the Greenwich meridian with hand nets, and one sediment surface transect from the South Pacific, were analyzed. In each of these transects, both morphotypes were detected, and annual mean sea surface temperatures (SST) were found to be a good predictor of their relative abundances. The transition between dominance of one or the other morphotype appeared roughly between the Antarctic Polar Front and the Southern Boundary of the Antarctic Circumpolar Current. Although more extensive circumpolar sampling will be needed to confirm the generality of our conclusions, the observed morphometric cline is a novel aspect of the biology of this species and can in the future potentially be used for further developing paleoproxies especially for highly F.kerguelensis-dominated sediment in the Southern Ocean.