Gradients4_TN397_15N13C_2022-03-15

Cruise Name: Gradients 4 , TN397 Vessel: R/V Thompson Funding: Simons Collaboration on Ocean Processes and Ecology (SCOPE) Dataset description: Standard protocols were used to measure in vitro primary productivity via the 13C radiotracer method [Lengendre et al., 1996] and N2-fixation rate measurements via 15N2 isotopic gas method described by Montoya et al., 1996. Briefly, water samples were collected before dawn in ~4.3L polycarbonate bottles, a total of 4ml of enriched 15N2 gas was added via syringe. Bottles were then injected with 1 ml of 47mM 13C bicarbonate stock and gently mixed by inversion. Bottles were incubated either on deck in incubators screened to 48% of surface irradiance and plumbed with flow through surface seawater for temperature regulation or on drifting arrays that allowed for incubations to happen at original light levels. All bottles were incubated for ~ 24hr. Time zero bottles were also collected and sacrificed for each station/depth. Following dawn to dawn incubations, each sample was filtered onto a combusted 25mm glass fiber filter, filters were folded in half and placed in combusted aluminum foil and stored at -20°C for later analysis. Post-cruise, all filters were thawed and dried overnight at 60°C. Samples were then balled into Sn boats and plated for analysis. The carbon and nitrogen isotopic composition (13C and 15N, respectively) were analyzed by continuous-flow isotope ratio mass spectrometry by the Biogeochemical Stable Isotope Facility at University of Hawaii (https://www.soest.hawaii.edu/GG/isotope_biogeochem/index_files/Page532.htm).航次名称：Gradients 4，TN397；考察船：汤普森号科考船（R/V Thompson）；资助方：西蒙斯海洋过程与生态合作项目（Simons Collaboration on Ocean Processes and Ecology, SCOPE）。数据集说明：本数据集采用标准实验方法，通过13C放射性示踪法（Lengendre等，1996）测定离体初级生产力，并采用Montoya等1996年提出的15N2同位素气体法测定固氮速率。实验流程简述如下：于黎明前采集水样至约4.3L聚碳酸酯瓶中，通过注射器注入总计4mL的富集15N2气体；随后加入1mL 47mM的13C碳酸氢盐储备液，轻柔倒置混匀。培养瓶分为两组进行培养：其一置于遮光至表层辐照度48%的甲板培养箱内，通过流通表层海水调控温度；其二放置于漂移阵列中，以维持原位光照水平开展培养。所有培养瓶均培养约24小时，同时在每个站位/深度采集零时刻培养瓶并进行预处理。完成跨黎明的培养后，将每个样品过滤至经高温灼烧处理的25mm玻璃纤维滤膜上，将滤膜对折后放入灼烧过的铝箔中，置于-20℃低温保存以待后续分析。航次结束后，将所有滤膜解冻并在60℃下烘干过夜，随后将样品封装入锡舟中制备待分析样品。碳、氮同位素组成（分别为13C和15N）由夏威夷大学（University of Hawaii）生物地球化学稳定同位素实验室采用连续流同位素比值质谱法完成测定，相关实验室网址为https://www.soest.hawaii.edu/GG/isotope_biogeochem/index_files/Page532.htm。