Downward vertical flux of size-fractionated Chlorophyll-a and phaeopigments in the northern Barents Sea during August 2019, Nansen Legacy cruise 2019706 Q3

Samples for sinking mass flux of size-fractionated (>0.7µm and >10µm) Chlorophyll-a and Phaeopigments were collected with short-term drifting sediment traps between 75° and 85°N in the northern Barents Sea with R/V Kronprins Haakon in August 2019 as part of the Nansen Legacy project (cruise 2019706, Q3). High-density bottom water was collected at the station and filtered (Whatman GF/F 0.7µm), and then filled into the trap cylinders (KC Denmark, aspect ratio >6) prior to their deployment. Afterwards, the sediment traps were deployed with 2 or 4 cylinders at each depth (30, 40, 60, 90, 120, 200m) for a duration between 18 to 25 hours. Depending on the sea ice conditions, the sediment traps were deployed in open water, anchored to a sea ice floe or within an ice lead. Upon retrieval, the content of the cylinders from each depth was pooled and stored at 4°C in dark until further analyses. Between 100-300ml were filtered onto 0.7µm GF/F filters (Whatman) for the analysis of Chla and Phaeopigments, depending on the amount of material in the traps. To quantify the contribution of larger cells, additional subsamples for Chla were filtered onto 10µm polycarbonate filters (Millipore). After filtration, both filters were immediately transferred to a tube with 100% methanol and stored between 12-24h at 4°C for pigment extraction. Size-fractionated Chla (0.7 and 10µm) was measured with a pre-calibrated Turner Design AU-10 fluorometer before and after acidification with 5% HCl. Chla and phaeopigments were calculated according to Holm-Hansen & Riemann, 1978.

Holm-Hansen, Osmund, and Bo Riemann. “Chlorophyll a Determination: Improvements in Methodology.” Oikos 30 (1978). https://doi.org/10.2307/3543338.

本数据集采集自2019年8月巴伦支海北部北纬75°至85°海域，随"哈康王储号"（R/V Kronprins Haakon）科考航次（隶属于"南森遗产"（Nansen Legacy）项目，航次编号2019706，航段Q3），采用短期漂移型沉积物捕集器获取粒径分级（>0.7μm及>10μm）的叶绿素a（Chlorophyll-a，Chla）与褐色素（Phaeopigments）沉降质量通量样品。在采样站位采集高密度底层海水，经Whatman GF/F 0.7μm滤膜过滤后注入沉积物捕集器的圆柱舱体（KC Denmark生产，长宽比>6），随后完成布设。沉积物捕集器于30、40、60、90、120、200m共6个深度层分别搭载2或4个圆柱舱体，布设时长为18至25小时。根据海冰条件，捕集器分别部署于开阔水域、固定于海冰浮冰或冰间水道内。回收捕集器后，将各深度层圆柱舱内的样品合并，于4℃避光保存以待后续分析。根据捕集器内样品的生物量丰度，取100~300mL样品经Whatman 0.7μm GF/F滤膜过滤，用于叶绿素a与褐色素的分析检测。为量化大型浮游植物细胞的贡献占比，另行采集叶绿素a分析的子样品，经10μm聚碳酸酯滤膜（Millipore）过滤。过滤完成后，两种滤膜均立即转移至装有100%甲醇的试管中，于4℃避光保存12~24小时以完成色素萃取。采用经预先校准的Turner Design AU-10型荧光光度计，在以5%盐酸酸化前后分别测定对应0.7μm和10μm截流粒径的分级叶绿素a含量。叶绿素a与褐色素的含量计算参照Holm-Hansen与Riemann于1978年发表的方法：Holm-Hansen O, Riemann B. "Chlorophyll a Determination: Improvements in Methodology"[J]. Oikos, 1978, 30: https://doi.org/10.2307/3543338。