Chemical signatures in the calcite of shells of polar and subpolar planktonic foraminifera have been frequently used to trace and quantify past meltwater discharge events. This approach assumes that the foraminifera can tolerate low salinity under extended periods. To obtain a first experimental constraint on salinity tolerance of Subarctic foraminifera, we carried out a culturing experiment with specimens of the subpolar species Neogloboquadrina incompta collected in the northern Norwegian Sea off Tromso in October 2018. The foraminifera were exposed to a gradient of salinities between 35 and 25 PSU. Survival was monitored over 26 days by measuring the extent of the rhizopodial network. Although chamber growth only occurred in one of the observed specimens, likely due to the largely unknown dietary preference of the species, we observed a strong differential rhizopodial activity pattern along the gradient. The highest rhizopodial activity occurred at salinity between 35 and 31 PSU. The species is clearly able to survive long-term exposure to salinities as low as 28, but no rhizopodial activity and signs of cytoplasm degradation were observed in all specimens exposed to 25 PSU. These preliminary observations provide the first direct evidence for the salinity tolerance of N. incompta, indicating a range of salinity that could be plausibly expected to be recorded in the chemistry of fossil shells of the species.

中文翻译：

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实验性降低盐度对亚北极浮游有孔虫 Neogloboquadrina incompta 生存能力的影响

极地和亚极地浮游有孔虫壳方解石中的化学特征经常被用来追踪和量化过去的融水排放事件。这种方法假设有孔虫可以长时间耐受低盐度。为了获得亚北极有孔虫耐盐性的第一个实验约束，我们对 2018 年 10 月在特罗姆瑟附近挪威海北部收集的亚极地物种 Neogloboquadrina incompta 的标本进行了培养实验。有孔虫暴露于 35 之间的盐度梯度和 25 电源。通过测量根足网络的范围，监测了 26 天的存活率。虽然房间生长只发生在一个观察到的标本中，可能是由于该物种在很大程度上未知的饮食偏好，我们观察到沿梯度存在强烈的差异性根足活动模式。最高的根足类活动发生在 35 到 31 PSU 之间的盐度。该物种显然能够长期暴露于低至 28 的盐度，但在暴露于 25 PSU 的所有标本中均未观察到根足类活动和细胞质降解迹象。这些初步观察为 N. incompta 的盐度耐受性提供了第一个直接证据，表明可以合理地预期在该物种的化石壳的化学中记录的一系列盐度。但在暴露于 25 PSU 的所有标本中均未观察到根足类活动和细胞质降解迹象。这些初步观察为 N. incompta 的盐度耐受性提供了第一个直接证据，表明可以合理地预期在该物种的化石壳的化学中记录的一系列盐度。但在暴露于 25 PSU 的所有标本中均未观察到根足类活动和细胞质降解迹象。这些初步观察为 N. incompta 的盐度耐受性提供了第一个直接证据，表明可以合理地预期在该物种的化石壳的化学中记录的一系列盐度。