Diatom valves for the Holocene sediment sequence retrieved from Lake Loitsana, Finland

This dataset provides counts of diatom valves for the Holocene sediment sequence retrieved from Lake Loitsana (Finland) in 2008. Counts per taxon are presented against both depth (m) and age (cal ka. BP); total sums for classes of diatoms (e.g. total benthic taxa) and all counts are presented as well. Two age/depths models are presented: the first model represents the original age/depth model applied to the records (Shala et al., 2014; 2017) and the second age/depth model, which is the author-preferred version, presents updated age-estimates derived using the r package 'Bacon' (Blaauw and Christensen, 2011). The diatom dataset provides information on Holocene lake ecosystem dynamics and was used to quantitatively reconstruct Total Phosphorous (TP) values of the lake water. A total of 124 samples were selected for diatom analysis. Diatoms were extracted from the sediment following the protocol presented by Battarbee (1986). First, organic matter was oxidized in H2O2 in a water bath (at c. 100 °C). Subsequently, carbonates were removed by 10% HCl treatment (no visible reaction). Clay particles were decanted from 100 ml beakers (2h intervals). Sand grains were removed after five seconds of sedimentation. The residue was mounted in Naphrax® and analysed under a light microscope with X1000 magnification using immersion oil. Flora used for species identification and information on ecological preferences are presented in Helmens et al. (2009). A minimum of 500 diatoms were identified from each sample with the exception of samples at 900-700 cm where diatom abundance was low. All analyses were performed in the laboratories Stockholm University, Sweden.

本数据集提供了2008年从芬兰洛伊察纳湖（Lake Loitsana）获取的全新世（Holocene）沉积序列中硅藻瓣的计数数据。每个分类单元（taxon）的计数数据均对应深度（米，m）和年代（校正千年BP，cal ka. BP）呈现；同时还提供了硅藻类群的总和（如底栖类群总数）及所有计数的汇总。
本数据集包含两种年代-深度模型：第一种为原始应用于该记录的年代-深度模型（Shala等，2014；2017）；第二种为作者偏好的版本，其呈现的更新年代估计值是通过R语言包‘Bacon’（Blaauw和Christensen，2011）推导得出。
该硅藻数据集提供了全新世湖泊生态系统动态的信息，并被用于定量重建湖水的总磷（Total Phosphorous，TP）含量。
共选取124个样本进行硅藻分析。硅藻提取遵循Battarbee（1986）提出的方案：首先，有机质在过氧化氢（H₂O₂）中于水浴（约100°C）条件下氧化；随后，通过10%盐酸（HCl）处理去除碳酸盐（无可见反应）；从100毫升烧杯中倾析去除黏土颗粒（间隔2小时）；沉降5秒后去除砂粒；残留物用Naphrax®封片，在配备浸油的光学显微镜下以1000倍放大率进行分析。
物种鉴定所用的硅藻图鉴及生态偏好信息详见Helmens等（2009）。除900-700厘米深度处硅藻丰度较低的样本外，每个样本至少鉴定出500个硅藻。所有分析均在瑞典斯德哥尔摩大学实验室完成。