We traced diatom composition and diversity through time using diatom derived sedimentary ancient DNA (sedaDNA) from eastern continental slope sediments off Kamchatka (North Pacific) by applying a short, diatom‐specific marker on 63 samples in a DNA metabarcoding approach. The sequences were assigned to diatoms that are common in the area and characteristic of cold water. SedaDNA allowed us to observe shifts of potential lineages from species of the genus Chaetoceros that can be related to different climatic phases, suggesting that pre‐adapted ecotypes might have played a role in the long‐term success of species in areas of changing environmental conditions. These sedaDNA results complement our understanding of the long‐term history of diatom assemblages and their general relationship to environmental conditions of the past. Sea‐ice diatoms (Pauliella taeniata (Grunow) Round & Basson, Attheya septentrionalis (Østrup) R.M.Crawford and Nitzschia frigida (Grunow)) detected during the late glacial and Younger Dryas are in agreement with previous sea‐ice reconstructions. A positive correlation between pennate diatom richness and the sea‐ice proxy IP₂₅ suggests that sea ice fosters pennate diatom richness, whereas a negative correlation with June insolation and temperature points to unfavorable conditions during the Holocene. A sharp increase in proportions of freshwater diatoms at ∼11.1 cal kyr BP implies the influence of terrestrial runoff and coincides with the loss of 42% of diatom sequence variants. We assume that reduced salinity at this time stabilized vertical stratification which limited the replenishment of nutrients in the euphotic zone.

中文翻译：

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北极亚太平洋北部沉积古DNA：过去20,000年以来海冰，盐度和日射动力学如何塑造硅藻的组成和丰富度

我们使用来自硅藻土的堪察加半岛（北太平洋）东部大陆斜坡沉积物中的硅藻衍生的古代沉积DNA（sed aDNA），通过对DNA分子条形码技术在63个样品上应用了一种短的，硅藻特异性的标记，追踪了硅藻的组成和多样性随时间的变化。这些序列被分配给在冷水区域和特征中常见的硅藻。Sed aDNA使我们能够观察到Chaetoceros属物种潜在谱系的变化，这些谱系可能与不同的气候阶段有关，这表明在环境条件不断变化的地区，预先适应的生态型可能在物种的长期成功中发挥了作用。这些sedaDNA结果补充了我们对硅藻集合体的长期历史及其与过去环境条件的一般关系的理解。在冰河晚期和较年轻的树蛙中发现的海冰硅藻（Pauliella taeniata（Grunow）Round＆Basson，Attheya septentrionalis（Østrup）RMCrawford和Nitzschia frigida（Grunow））与先前的海冰重建一致。羽状硅藻的丰富度与海冰代理IP ₂₅之间呈正相关这表明海冰促进了戊二烯硅藻的丰富，而与六月的日照和温度的负相关表明全新世期间的不利条件。在约11.1千卡BP时，淡水硅藻的比例急剧增加，这暗示了地表径流的影响，并且与42％的硅藻序列变体的损失相吻合。我们假设盐度的降低此时稳定了垂直分层，从而限制了富营养区内养分的补充。