Pore water chemistry and sediment temperature for cores COAST_C-2 and BK-2, central Laptev Sea shelf

Submarine permafrost is more vulnerable to thawing than permafrost on land. Besides increased heat transfer from the ocean water, the penetration of salt lowers the freezing temperature and accelerates permafrost degradation. This data set provides sediment temperatures and pore water chemistry from two submarine permafrost cores from the Laptev Sea on the East Siberian Arctic Shelf which inundated about 540 and 2500 years ago. These data are published in partnership with a paper by Magritz et al., that traces how bacterial communities develop depending on duration of the marine influence and pore water chemistry. Magritz et al. (2017) show that submarine permafrost is a source of microbial life deep below the seafloor where it forms an unusual, non-steady state habitat. Pore water chemistry revealed different pore water units that reflected stages of permafrost thaw. Millennia after inundation by sea water, bacteria stratify into communities in permafrost, marine-affected permafrost, and seabed sediments. In contrast to pore water chemistry, the development of bacterial community structure, diversity and abundance in submarine permafrost appear site-specific, suggesting that both sedimentation and permafrost thaw histories strongly affect bacteria. Finally, highest total cell counts, DNA concentrations and bacterial gene copy numbers were observed in the ice-bonded unaffected permafrost unit of the longer inundated core, suggesting that permafrost bacterial communities exposed to submarine conditions proliferate millennia after warming.

海底永久冻土（submarine permafrost）相较于陆地永久冻土更易发生融化。除海水热传递增强之外，盐分渗透还会降低冻土的冻结温度，加速永久冻土的退化过程。本数据集包含取自东西伯利亚北极大陆架拉普捷夫海的两份海底永久冻土岩芯的沉积物温度与孔隙水化学（pore water chemistry）数据，这两处岩芯分别在约540年前和2500年前被海水淹没。本数据集与Magritz等人的研究论文联合发表，该论文阐明了细菌群落如何随海洋影响时长与孔隙水化学特征的变化而发展演替。Magritz等人（2017年）的研究表明，海底永久冻土是海床下方深层微生物生命的生存来源，此处形成了一种独特的非稳态生境。孔隙水化学特征可区分出不同的孔隙水单元，这些单元对应了永久冻土融化的不同阶段。在被海水淹没数千年后，细菌群落出现分层，分别存在于永久冻土、受海洋影响的永久冻土以及海床沉积物中。与孔隙水化学特征不同，海底永久冻土中细菌群落结构、多样性与丰度的演化呈现出位点特异性，这表明沉积作用与永久冻土融化历史均会对细菌群落产生强烈影响。最终，在被淹没更久的那份岩芯的未受影响冰胶结永久冻土单元中，观测到了最高的总细胞计数、DNA浓度与细菌基因拷贝数，这表明暴露于海底环境的永久冻土细菌群落在变暖数千年后仍能实现增殖。