Laser ablation data of benthic foraminifera from surface sediments collected from the muddy intertidal flats near Dorum, Northwestern Germany in Autumn 2008

Biological activity introduces variability in element incorporation during calcification and thereby decreases the precision and accuracy when using foraminifera as geochemical proxies in paleoceanography. This so-called 'vital effect' consists of organismal and environmental components. Whereas organismal effects include uptake of ions from seawater and subsequent processing upon calcification, environmental effects include migration- and seasonality-induced differences. Triggering asexual reproduction and culturing juveniles of the benthic foraminifer Ammonia tepida under constant, controlled conditions allow environmental and genetic variability to be removed and the effect of cell-physiological controls on element incorporation to be quantified. Three groups of clones were cultured under constant conditions while determining their growth rates, size-normalized weights and single-chamber Mg/Ca and Sr/Ca using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Results show no detectable ontogenetic control on the incorporation of these elements in the species studied here. Despite constant culturing conditions, Mg/Ca varies by a factor of similar to 4 within an individual foraminifer while intra-individual Sr/Ca varies by only a factor of 1.6. Differences between clone groups were similar to the intra-clone group variability in element composition, suggesting that any genetic differences between the clone-groups studied here do not affect trace element partitioning. Instead, variability in Mg/Ca appears to be inherent to the process of bio-calcification itself. The variability in Mg/Ca between chambers shows that measurements of at least 6 different chambers are required to determine the mean Mg/Ca value for a cultured foraminiferal test with a precision of <= 10%

生物活动在钙化过程中会引入元素摄入的变异性，从而降低了将有孔虫（foraminifera）用作古海洋学地球化学代用指标时的分析精度与准确性。这种被称为“生命效应（vital effect）”的现象包含生物组分与环境组分两大组成部分。其中生物组分效应涵盖从海水中摄取离子以及钙化过程中的后续离子处理环节，而环境组分效应则包括由迁移活动和季节周期性所引发的差异。通过诱导无性繁殖，并在恒定可控的培养条件下培育底栖有孔虫钝顶卷转虫（Ammonia tepida）的幼体，可消除环境与遗传变异，进而量化细胞生理调控对元素摄入的影响。研究人员设置三组克隆株系，在恒定培养条件下开展培育，同时采用激光剥蚀-电感耦合等离子体质谱法（LA-ICP-MS）测定其生长速率、规格标准化后的壳体重量，以及单个房室的镁钙比（Mg/Ca）与锶钙比（Sr/Ca）。实验结果显示，在本次研究的物种中，未检测到个体发育阶段对这两种元素摄入的调控作用。尽管培养条件恒定，但单个有孔虫个体内的Mg/Ca变异幅度可达约4倍，而个体内Sr/Ca的变异幅度仅为1.6倍左右。不同克隆株系之间的元素组成差异，与同一克隆株系内部的变异程度相当，表明本次研究中各克隆株系间的遗传差异并不会影响微量元素的分配过程。由此可见，Mg/Ca的变异性似乎是生物钙化（bio-calcification）过程本身所固有的。不同房室间的Mg/Ca变异特征表明，若要以精度≤10%的要求测定人工培养的有孔虫壳体的平均Mg/Ca值，至少需要对6个不同的房室开展测量。