Sinking rates, orientation and behaviour of pennates diatoms in coastal waters

Phytoplankton cells can no longer be considered as passive particles and they can modulate impacts of selection factors (light, turbidity and mixing) through a wide range of adaptations . Cell shape and/or chain length modulation is one of these processes, but it still mainly studied as an adaptation or an acclimatation to a specific stress (light, nutrients, predation, etc.). This study showed that cell shape and size may have a greater role than previously known in phytoplankton ecology and species adaptation by permitting synchronous processes to be set up. Through microscale biophysical interactions leading to specific cell reorientation processes, we show that cell geometry not only modulates their sinking rate but can also provide a fast sensor response for their environment. Gyrotaxis has already been described in detail for motile phytoplankton cells, but the reorientation process described here can occur in the environment without motile capacity. An additional consistent behaviour was also recently described for a diatom species (Pseudo- nitzschia delicatessima) and with this study, and we extend this observation to Pseudo-nitzschia Pungens and Pseudo-nitzschia Fraudulenta. Our observation emphasizes the generality of this process which adds a new level of complexity with regards to cellular interactions and their network of sensors. Data : Data set is divided in three parts. 1- Labels per strain are provided in the ods file. 2- Flowcytometer raw files (.cyz) and exported files (.csv) for 19 phytoplankton strains are provided in the zip files. Three replicates were made over the time (three subdirectories). Flowcytometer analyses were made with and without images acquisition as indicated in each filename. Clusters available in the exported files were made manually and according to the number of cell per particle. Mean abundances per cluster are provided in the csv files. 3- Processed LISST data. Temporal evolution of cell’s aspect ratio R, defined as the ratio between the cross-sectional (r1) and the transapical cell axis (r2) of Pseudo-nitzschia fraudulenta strains in ligth and dark conditions.

浮游植物细胞已不再能被视作被动颗粒，它们可通过多样的适应策略调控选择因子（光照、浊度与混合作用）的影响效应。细胞形态和/或链长调控正是这类过程之一，但目前该领域的研究仍主要将其视为针对特定胁迫（光照、营养限制、捕食作用等）的适应或驯化机制。本研究表明，细胞形态与尺寸可通过促成同步化过程的建立，在浮游植物生态学及物种适应中发挥比以往认知更为关键的作用。
通过触发特定细胞重定向过程的微尺度生物物理相互作用，本研究证实细胞几何形态不仅可调控其沉降速率，还能为其环境感知提供快速响应通路。趋旋运动（Gyrotaxis）在运动型浮游植物细胞中已有详尽研究，但本研究描述的重定向过程可在不具备运动能力的环境中发生。近期还有研究针对一种硅藻物种（细弱拟菱形藻（Pseudo-nitzschia delicatessima））报道了这一一致行为，本研究则将该观测结果拓展至尖刺拟菱形藻（Pseudo-nitzschia pungens）与佛氏拟菱形藻（Pseudo-nitzschia fraudulenta）。本研究的观测结果凸显了该过程的普遍性，其为细胞相互作用及其感知网络增添了全新的复杂性维度。
数据集分为三部分：
1. 各藻株的分类标签存储于ods文件中。
2. 19株浮游植物的流式细胞仪（Flowcytometer）原始文件（.cyz）与导出文件（.csv）存储于压缩包中。实验设置了三次重复实验，对应三个子目录。流式细胞仪分析分别开展了图像采集与未采集两种模式，具体信息可从各文件名中获取。导出文件中的细胞簇是根据每个颗粒所含的细胞数量手动划定的，csv文件中提供了每个细胞簇的平均丰度。
3. 经处理的激光原位散射透射粒度分析仪（LISST）数据：记录了佛氏拟菱形藻（Pseudo-nitzschia fraudulenta）藻株在光照与黑暗条件下，细胞长宽比R的时间演化过程。其中长宽比R定义为细胞横截面轴（r1）与顶轴（transapical cell axis，r2）的比值。