CO2-induced changes in Antarctic phytoplankton communities using pigments

The data reports the pigment concentrations and results of CHEMTAX analysis for 2 summer seasons in Antarctic. In 2008/09 three experiments in which 6 x 650 l minicosms (polythene tanks) were used to incubate natural microbial communities (less than 200 um diameter) at a range of CO2 concentrations while maintained at constant light, temperature and mixing. The communities were pumped from ice-free water ~60 m offshore on 30/12/08, 20/01/09 and 09/02/09. These experiments received no acclimation to CO2 treatment. A further experiment was performed in 2014/15 using water helicoptered from ~ 1 km offshore amongst decomposing fast ice on 19/11/14. This experiment included a 5 day period during which the community was exposed top low light and the CO2 was gradually raised to the target value for each tank, followed by a two day period when the light was raised to an irradiance that was saturating but not inhibitory for photosynthesis.
A range of coincident measurements were performed to quantify the structure and function of the microbial community (see Davidson et al. 2016 Mar Ecol Prog Ser 552: 93–113, doi: 10.3354/meps11742 and Thomson et al 2016 Mar Ecol Prog Ser 554: 51–69, 2016, doi: 10.3354/meps11803).
The data provides a matrix of samples against component pigment concentration and the output from CHEMTAX that best explained the phytoplankton composition of the community based on the ratios of the component pigments.
For the 2008/09 experiments, samples were obtained every 2 days for 10, 12 and 10 days in experiments 1, 2 and 3 respectively. In 2014/15 samples were obtained from each incubation tank on days 1,3, 5, and 8 during th acclimation period and every 2 days until day 18 thereafter. For each sample a measured volume was filtered through 13 mm Whatman GF/F filters for 20 mins. Filters were folded in half, blotted dry, and immediately frozen in liquid nitrogen for analysis in Australia. Pigments were extracted, analysed by HPLC, and quantified following the methods of Wright et al. (2010). Pigments (including Chl a) were extracted from filters with 300 micro l dimethylformamide plus 50 micro l methanol, containing 140 ng apo-8'-carotenal (Fluka) internal standard, followed by bead beating and centrifugation to separate the extract from particulate matter. Extracts (125 micro l) were diluted to 80% with water and analysed on a Waters HPLC using a Waters Symmetry C8 column and a Waters 996 photodiode array detector. Pigments were identified by comparing retention times and spectra to a mixed standard sample from known cultures (Jeffrey and Wright, 1997), run daily before samples. Peak integrations were performed using Waters Empower software, checked manually for corrections, and quantified using the internal standard method (Mantoura and Repeta, 1997).

本数据集记录了南极两个夏季的色素浓度及CHEMTAX (CHEMTAX)分析结果。2008/09年度开展了三组实验，每组均使用6个650升微型生态箱（聚乙烯容器），将粒径小于200微米的自然微生物群落置于不同二氧化碳浓度环境中培养，同时维持恒定的光照、温度与混合条件。微生物群落于2008年12月30日、2009年1月20日及2009年2月9日从离岸约60米的无冰水域抽取，且未经过二氧化碳预处理驯化。2014/15年度开展了另一组实验：2014年11月19日，从离岸约1公里的降解中固定冰区域通过直升机取水开展实验。该实验包含5天的驯化阶段：群落先处于低光照环境，逐步将各容器内的二氧化碳浓度提升至目标值；随后进入2天的高光照阶段，光照强度设置为光合饱和且不产生抑制作用的水平。
为量化微生物群落的结构与功能，本研究开展了一系列同步测量（详见Davidson等人2016年发表于《Marine Ecology Progress Series》的论文，卷552，第93-113页，DOI: 10.3354/meps11742，以及Thomson等人2016年发表于同刊卷554，第51-69页，DOI: 10.3354/meps11803）。
本数据集包含样本与各组分色素浓度的对应矩阵，以及基于组分色素比例、最能解释群落浮游植物组成的CHEMTAX分析输出结果。
针对2008/09年度的三组实验，分别连续采样10、12、10天，每2天取样一次。2014/15年度的实验中，在驯化阶段的第1、3、5、8天从每个培养容器取样，之后每2天取样一次直至第18天。每份样本取定量体积，经13毫米Whatman GF/F滤膜过滤20分钟。滤膜对折后吸干水分，立即置于液氮中冷冻，运回澳大利亚进行后续分析。
色素提取与高效液相色谱 (HPLC)分析方法参考Wright等人2010年的研究。具体步骤为：将滤膜置于含140纳克内标apo-8'-胡萝卜素醛（Fluka品牌）的300微升二甲基甲酰胺与50微升甲醇混合液中，通过珠磨破碎后离心分离提取液与颗粒物。取125微升提取液，加水稀释至80%浓度，使用配备Waters Symmetry C8色谱柱与Waters 996光电二极管阵列检测器的Waters高效液相色谱仪进行分析。色素鉴定通过保留时间与光谱特征对比已知培养物混合标准品完成（Jeffrey & Wright, 1997），标准品每日在样品分析前运行。峰积分使用Waters Empower软件完成，人工复核并修正积分结果，采用内标法进行定量（Mantoura & Repeta, 1997）。