Effects of ocean acidification (pHtotal~7.8) on calcification, photosynthesis, carbon and nitrogen contents and carbon isotopic signatures on Halimeda opuntia grown at tropical carbon dioxide seeps (NERP TE 5.2, AIMS)

This dataset consists of one csv data file from field derived experiments at tropical carbon dioxide seeps in Papua New Guinea, measuring the response parameters: calcification, photosynthesis, carbon and nitrogen contents and carbon isotopic signatures on Halimeda opuntia grown under ocean acidification conditions. The aim of this study was to investigate the effects of ocean acidification on Halimeda opuntia grown under ocean acidification conditions at tropical carbon dioxide seeps. Therefore we tested several response parameters to try to understand how the calcareous alga is capable of growing under ocean acidification conditions.Method:At several locations in Milne Bay Province, Papua New Guinea, volcanic CO2 is seeping out of the seafloor (Fabricius et al. 2011). The seep sites are located at Dobu Island and Upa-Upasina (Normanby Island) close to the shore in shallow water of ~1–15 m depth and extend over an area of ~20 by 100 m with different intensities of bubble activity within this area. Control reefs were allocated several hundred meters away from the seep sites with no impact of the seep activity on their seawater carbonate system. The bubbles, which consist of pure CO2, ascend to the surface and mix with the ambient seawater, changing the carbonate chemistry. This study was confined to areas where seawater chemistry was altered to levels projected for a vast part of the globe for the end of this century (‘representative concentration pathway’ RCP6.0 to RCP8.5 scenarios) (Moss et al. 2010).Calcification rates in the light and dark, as well as net photosynthesis and respiration rates, were measured in-situ at control (pHtotal = 8.17) and seep sites (pHtotal = 7.77). Branches 5 – 8 cm in height and with ~20 phylloids of H. opuntia were collected and retained at the site of collection until incubations commenced. Light incubations were conducted in-situ at 5 m water depth at midday. Specimens were placed into 0.5 L clear Perspex chambers, simultaneously at control and seep sites, by two separate SCUBA diving teams. After ~3 h incubation under ambient light, incubation chambers were retrieved and a water subsample was directly analyzed for total alklinity. Oxygen concentration was determined in each incubation chamber including two blank incubations per treatment (to correct for seawater production/ respiration) with a hand-held dissolved oxygen meter (HQ30d, Hach, USA). Light intensities of incubation conditions were recorded by two light loggers (Odyssey, New Zealand) each at control and seep site. Photosynthetically available radiations (PAR) was dependent on weather conditions and averaged 259 and 281 µmol photons m-2 s-1 for H. opuntia incubations. Dark incubations were conducted on board the research vessel for ~3 h in the evening. The incubation chambers were filled with water from the site of origin of the plants (control vs. seep site). Chambers were placed in black plastic bins (45 L) with lids for darkening and flow-through seawater for temperature control. Rates of calcification were determined with the alkalinity anomaly technique (Chisholm and Gattuso 1991). Calcification rates (in µmol L-1 C h-1 gFW-1) and oxygen fluxes (in µg O2 h-1 gFW-1) were calculated in relation to blank incubations and standardized to the fresh weight (FW) of the plants. Daily net calcification rates were calculated by 12h of daylight and 12h of darkness.Apical phylloids of dried Halimeda spp. were crushed with mortar and pestle and the homogenate was analyzed for total carbon (Ctot) and total nitrogen (N) on a Flash EA 1112 elemental analyzer (Thermo Fisher Scientific, USA). In addition, organic carbon (Corg) contents were measured after acidifying the sample with 150µL concentrated HCl to drive out Cinorg. Inorganic carbon content was calculated by subtracting Corg from Ctot. Stable isotope signatures were measured in a subset of these samples using a Delta S mass spectrometer (Thermo Fisher Scientific, USA) coupled with the elemental analyzer.Further details can be found in the publication:Vogel, N., Fabricius, K. E., Strahl, J., Noonan, S. H. C., Wild, C. and Uthicke, S. (2015), Calcareous green alga Halimeda tolerates ocean acidification conditions at tropical carbon dioxide seeps. Limnology and Oceanography, 60: 263–275. doi: 10.1002/lno.10021Format:This dataset comprises a single csv file, Vogel_acid_opuntia.csv. Data Dictionary:The columns of the Vogel_acid_opuntia.csv are described below:- Species: Halimeda opuntia- Treatment: Site of collection/ measurement, seep site or control reef- Light calcification: calcification in light, given in µmol L-1 C h-1 gFW-1- Dark calcification: calcification in darkness, given in µmol L-1 C h-1 gFW-1- Net calcification: 12xlight+12xdark calcification, given in µmol L-1 C d-1 gFW-1- Net photosynthesis: oxygen production in light, given in µmol L-1 O2 h-1 gFW-1- Dark respiration: oxygen respiration in darkness, given in µmol L-1 O2 h-1 gFW-1- Gross photosynthesis: oxygen production – dark respiration, given in µmol L-1 O2 h-1 gFW-1- Ctot: total carbon content, given in molar %- Corg: organic carbon content, given in molar %- Cinorg: inorganic carbon content (Ctot-Corg), given in molar %- N: total nitrogen content, given in molar %References:Chisholm JRM, Gattuso JP (1991) Validation of the alkalinity anomaly technique for investigating calcification and photosynthesis in coral-reef communities. Limnol Oceanogr 36:1232-1239Fabricius KE, Langdon C, Uthicke S, Humphrey C, Noonan S, De'ath G, Okazaki R, Muehllehner N, Glas MS, Lough JM (2011) Losers and winners in coral reefs acclimatized to elevated carbon dioxide concentrations. Nature Climate Change 1:165 - 169Moss RH, Edmonds JA, Hibbard KA, Manning MR, Rose SK, van Vuuren DP, Carter TR, Emori S, Kainuma M, Kram T (2010) The next generation of scenarios for climate change research and assessment. Nature 463:747-756

本数据集包含一份来自巴布亚新几内亚热带二氧化碳渗漏区野外实验的CSV数据文件，测定了海洋酸化条件下生长的仙掌藻（Halimeda opuntia）的多项响应参数：钙化作用、光合作用、碳氮含量以及碳同位素特征。本研究旨在探究热带二氧化碳渗漏区海洋酸化条件下仙掌藻的生长响应效应，因此测定多项响应参数以阐明该钙化藻类在海洋酸化环境中的生存生长机制。

研究方法：在巴布亚新几内亚米尔恩湾省的多处海域，火山成因的二氧化碳从海底渗漏而出（Fabricius等，2011）。渗漏位点位于多布岛及乌帕-乌帕西纳（诺曼比岛）近岸浅水区，水深约1–15 m，渗漏区域面积约20×100 m，区域内气泡活动强度存在差异。对照礁设置于距离渗漏位点数百米处，不受渗漏活动对海水碳酸盐系统的影响。渗漏气泡为纯二氧化碳，上升至海面并与周围海水混合，改变了海水碳酸盐化学环境。本研究的试验区域海水化学条件已调整至本世纪末全球大部分海域预计达到的水平（即典型浓度路径RCP6.0至RCP8.5情景）（Moss等，2010）。

在对照位点（总pH=8.17）和渗漏位点（总pH=7.77）原位测定了光下与暗处的钙化速率、净光合速率及呼吸速率。采集高度5–8 cm、具有约20个叶状体（phylloid）的仙掌藻分枝，在采集地暂存直至培养实验开始。光培养于正午时分在5 m水深的原位环境中进行。两组水下潜水团队分别将样品置于0.5 L透明有机玻璃（Perspex）培养箱中，同步设置对照与渗漏位点的培养组。在自然光下培养约3 h后，取出培养箱并立即取水样进行总碱度分析。使用手持式溶解氧测定仪（HQ30d，Hach，美国）测定每个培养箱内的氧气浓度，每个处理组设置两个空白培养以校正海水本身的产氧/耗氧过程。光照强度由两台光照记录仪（Odyssey，新西兰）分别记录于对照与渗漏位点。光合有效辐射（Photosynthetically Available Radiation, PAR）受天气条件影响，仙掌藻培养实验的平均PAR分别为259和281 µmol photons m⁻² s⁻¹。

暗培养于晚间在研究船上进行，时长约3 h。培养箱使用采集自样品原生位点的海水（对照位点与渗漏位点分别对应）填充。将培养箱置于带盖的45 L黑色塑料箱中以避光，同时通入流动海水以控制温度。钙化速率采用碱度异常法测定（Chisholm和Gattuso，1991）。钙化速率（单位：µmol L⁻¹ C h⁻¹ gFW⁻¹）与氧气通量（单位：µg O₂ h⁻¹ gFW⁻¹）均以空白培养为基准进行计算，并以样品鲜重（Fresh Weight, FW）进行标准化。每日净钙化速率按12 h光照与12 h黑暗周期计算。

将干燥仙掌藻的顶端叶状体用研钵和研杵粉碎，匀浆后使用Flash EA 1112元素分析仪（Thermo Fisher Scientific，美国）测定总碳（Ctot）与总氮（N）含量。此外，将样品用150 µL浓盐酸酸化以去除无机碳（Cinorg）后，测定有机碳（Corg）含量；无机碳含量由总碳含量减去有机碳含量计算得到。选取部分样品使用Delta S质谱仪（Thermo Fisher Scientific，美国）与元素分析仪联用，测定其稳定同位素特征。

更多细节可参阅以下文献：
Vogel, N., Fabricius, K. E., Strahl, J., Noonan, S. H. C., Wild, C. and Uthicke, S. (2015), 钙化绿藻仙掌藻可耐受热带二氧化碳渗漏区的海洋酸化条件. 湖沼学与海洋学, 60: 263–275. doi: 10.1002/lno.10021

数据集格式：本数据集仅包含一个CSV文件，命名为Vogel_acid_opuntia.csv。

数据字典：Vogel_acid_opuntia.csv的各列说明如下：
- 物种：Halimeda opuntia（仙掌藻）
- 处理组：采集/测量位点，分为渗漏位点或对照礁
- 光下钙化：光下钙化速率，单位为µmol L⁻¹ C h⁻¹ gFW⁻¹
- 暗处钙化：暗处钙化速率，单位为µmol L⁻¹ C h⁻¹ gFW⁻¹
- 净钙化：12h光照+12h暗处的总钙化速率，单位为µmol L⁻¹ C d⁻¹ gFW⁻¹
- 净光合速率：光下产氧速率，单位为µmol L⁻¹ O₂ h⁻¹ gFW⁻¹
- 暗处呼吸：暗处耗氧速率，单位为µmol L⁻¹ O₂ h⁻¹ gFW⁻¹
- 总光合速率：光下产氧速率减去暗处呼吸速率，单位为µmol L⁻¹ O₂ h⁻¹ gFW⁻¹
- 总碳（Ctot）：总碳含量，单位为摩尔百分比
- 有机碳（Corg）：有机碳含量，单位为摩尔百分比
- 无机碳（Cinorg）：无机碳含量（Ctot - Corg），单位为摩尔百分比
- 总氮（N）：总氮含量，单位为摩尔百分比

参考文献：
1. Chisholm JRM, Gattuso JP (1991) 碱度异常法在珊瑚礁群落钙化与光合作用研究中的验证. Limnol Oceanogr 36:1232-1239
2. Fabricius KE, Langdon C, Uthicke S, Humphrey C, Noonan S, De'ath G, Okazaki R, Muehllehner N, Glas MS, Lough JM (2011) 适应高二氧化碳浓度的珊瑚礁群落中的赢家与输家. Nature Climate Change 1:165-169
3. Moss RH, Edmonds JA, Hibbard KA, Manning MR, Rose SK, van Vuuren DP, Carter TR, Emori S, Kainuma M, Kram T (2010) 气候变化研究与评估的新一代情景. Nature 463:747-756