HOE_Legacy2A-KM1513-Diazotroph Abundance_2021-05-01_v1.0

This dataset comes from sampling performed during the Hawaii Ocean Experiment - Legacy 2A cruise aboard the R/V Kilo Moana (cruise KM1513) in the north Pacific subtropical gyre. At select stations and depths (ranging from 5 to 45m), the entire volume of a Niskin bottle was drained directly into clean ~10L carboys fitted with spigots. Carboys were covered in dark cloth and the volume was gravity filtered through a 47-mm diameter, 10 micron pore size, black polycarbonate filter with a polyester drain disk as a backing filter. If the volume was not filtered after 2 hours, filtration was terminated and the remaining volume of the carboy was measured in order to calculate volume filtered. Following filtration, filter holders were fit with a short section of tubing and a syringe leur fitting on one side and a 2-way valve on the outflow side. For each filter, 5-ml of 2% glutaraldehyde was slowly injected onto the filter and samples were allowed to fix for 30 minutes. Fixative was drained after this time and 60ml of air was used to flush all filters. Polycarbonate filters were then mounted onto 3x2” glass slides with immersion oil, cover slides were added and the edges of each cover slip was sealed with quick dry nail polish. All slides were stored at -20°C and counted within 30 days. Enumeration of diazotrophic taxa was performed using epifluorescence microscopy. Random areas were counted until a minimum of 1000 cells were enumerated, generally this amounted to roughly 20% of the slide area for DDAs. The entire slide was counted for Trichodesimum abundance. Endosymbiont bearing diatoms of the following genus were enumerated: Rhizosolenia, Hemialus, Climacodium and Chaetoceras. Free Richelia intracellularis were also counted. Trichodesmium filaments were counted and the length of each filament was recorded. Trichodesmium cell number was then calculated by dividing the filament length by the mean cell length (12 micron ±2 micron).本数据集采集自北太平洋副热带环流区的夏威夷海洋实验-遗产2A航次，该航次由R/V基洛莫纳号（R/V Kilo Moana）执行，航次编号为KM1513。在选定的站位与5~45米的深度范围内，将尼斯金采水器（Niskin bottle）内的全部水样直接注入配备龙头的洁净10升储液坛（carboys）中。储液坛以遮光布包裹，水样经重力过滤通过直径47毫米、孔径10微米的黑色聚碳酸酯滤膜（polycarbonate filter），以聚酯引流盘作为背衬滤器。若水样在2小时内未完成过滤，则终止过滤流程并测量储液坛内剩余水样体积，以此计算已过滤水样体积。过滤完成后，滤器支架加装短管段：一侧连接注射器鲁尔接头（syringe leur fitting），另一侧流出端安装双向阀。向每张滤膜缓慢注入5毫升2%戊二醛（glutaraldehyde），静置固定30分钟。固定结束后倒出固定液，再以60毫升空气冲洗所有滤膜。随后将聚碳酸酯滤膜用浸油固定于3×2英寸载玻片上，加盖盖玻片后，以快干指甲油密封盖玻片边缘。所有玻片均保存于-20℃环境，并在30天内完成计数。固氮类群的计数采用落射荧光显微镜（epifluorescence microscopy）法。随机选取视野进行计数，直至累计统计至少1000个细胞；对于硅藻-固氮生物聚集体（Diatom-Diazotroph Assemblages，DDAs），该流程通常需覆盖约20%的玻片面积。束毛藻属（Trichodesmium）的丰度需对整张玻片进行计数。需枚举携带内共生体的下列硅藻属类：根链藻属（Rhizosolenia）、半管藻属（Hemialus）、帽形藻属（Climacodium）以及角毛藻属（Chaetoceras），同时计数游离的胞内里氏藻（Richelia intracellularis）。统计束毛藻属丝状体的数量并记录每根丝状体的长度，通过将丝状体总长度除以平均细胞长度（12微米±2微米），计算得到束毛藻属的细胞总数。