The diatom Thalassiosira pseudonana grown in mesocosms at contemporary and elevated CO2 over the diel cycle

To test whether elevated CO2 , which drives seawater below pH 7.9, would shift the dynamical expression patterns diatoms in a more natural environment, we designed a controlled mesocosm study at Friday Harbor Laboratories (FHL) Ocean Acidification Environmental Laboratory (OAEL). Briefly, four independent mesocosm tanks were set up with continuous flow (10-12 mL/min) of filtered seawater from the Puget Sound to simulate mid-century (pH 7.9) and acidified oceanic conditions (pH 7.6) in duplicate. Mesocosm reservoirs were supplemented with nutrients and inoculated with T. pseudonana acclimated in FHL seawater. Mesocosms were outfitted with custom enclosures to simulate a 12:12 light:dark diel cycle. Cells for RNA extraction were sampled in the middle of the light and dark cycle and sequenced on Illumina NextSeq 500 platform. Overall design: Duplicate mesocosms at mid-century (pH 7.9) and acidified oceanic conditions (pH 7.6) were inoculated with T. pseudonana and grown over a 12:12 diel cycle (275 µM photons/m2/s). Cells were collected for gene expression analysis in the middle of the light and dark cycle over 2 days. Result: 16 total transcriptomes (n=4 at pH 7.9 in the light, n=4 at pH 7.9 in the dark, n=4 at pH 7.6 in the light, and n=4 at pH 7.6 in the dark).

为探究会使海水pH降至7.9以下的升高浓度二氧化碳，是否会在更贴近自然的环境中改变硅藻的动态表达模式，我们在星期五港实验室（Friday Harbor Laboratories, FHL）海洋酸化环境实验室（Ocean Acidification Environmental Laboratory, OAEL）开展了一项受控中宇宙（mesocosm）研究。简言之，我们设置4个独立的中宇宙培养罐，以10-12 mL/min的流速持续通入取自普吉特湾的过滤海水，设置两个生物学重复组分别模拟本世纪中期（pH 7.9）与酸化海洋环境（pH 7.6）。中宇宙培养池补充了营养盐，并接种了在FHL海水中驯化的假微型海链藻（T. pseudonana）。培养装置配备定制遮光装置，以模拟12:12的光暗昼夜循环。在光周期与暗周期的中间时段取样用于RNA提取，并通过Illumina NextSeq 500平台完成测序。实验总体设计：设置两个生物学重复的本世纪中期pH 7.9与酸化海洋pH 7.6的中宇宙培养体系，接种假微型海链藻（T. pseudonana），在12:12的昼夜循环（275 μmol光子/平方米/秒）下进行培养。在连续2天的光周期与暗周期中间时段收集细胞，用于基因表达分析。实验结果：共获得16套转录组数据（光周期pH 7.9组n=4，暗周期pH 7.9组n=4，光周期pH 7.6组n=4，暗周期pH 7.6组n=4）。