Nutrient data collected during the iMAR 2021/Eurofleets+ research cruise in Mid Atlantic Ridge (Azores EEZ)

this dataset was produced during the imar cruise “the integrated assessment of the distribution of vulnerable marine ecosystem along the mid-atlantic ridge (mar) in the azores region”, that took place aboard the research vessel pelagia of the royal netherlands institute for sea research between may 18th and june 2nd 2021. the imar cruise aimed to evaluate the role of the mar in shaping latitudinal and trans-atlantic patterns in deep-sea biogeography, connectivity and assemblages of deep-sea megafauna. this expedition was funded by the sea oceans program of eurofleets+ and the h2020 european project iatlantic, and was led by the university of the azores (portugal) in collaboration with the hydrographic institute and university of porto (portugal), the university of aarhus (denmark), the national oceanography center (united kingdom), geomar (germany), the university museum of bergen (norway), the pp shirshov institute of oceanology (russia), and the university of vale do itajaí (brazil).nutrient analysis was performed according to grasshoff et al, adopted for a 5 channel continues flow analyzer (skalar san plus, skalar analytical b. v., breda, the netherlands). nitrite and nitrate+nitrite was measured using an ammonia buffer and sulfanilamide/alpha-naphthylethylene diamine dihydrochloride colour reagent in phosphoric acid, with reduction of nitrate to nitrite by cadmium column of at least 80% measured reduction capacity (90-100% achieved), followed by quantification with spectrophotometric determination of the nitrite-azo dye at 540 nm. nitrate was determined as the difference between nitrate+nitrite and nitrite measurements. ammonia was measured using a citrate/tartrate buffer and phenol color reagent, catalyzed by hypochlorite and nitroprusside , followed by quantification with spectrophotometric determination of the phenol-ammonia complex at 630 nm. phosphate samples reacted with antimo nytartrate and ammonium molybdate solution in sulfuric acidified solution, the resulting complex wasreduced by ascorbic acid to a deep blue dye, followed by quantification with spectrophotometric determination of the reduced antimony-phospho-molybdate complex at 880 nm. silicate samples was acidified with sulfuric acid and reacted with ammonium molybdate solution, reduced by ascorbic acid to a blue dye with oxalic acid to remove phosphate interference , followed by quantification with spectrophotometric determination of the reduced molybdo-silicate complex at 810 nm.methods used are accredited with expected detection limit of 0,04 µm for nitrite, 0,1 µm for nitrate, 0,3 µm for ammonia, 0,06 µm for phosphate and 0,2 µm for silicate, with expected rsd between 4 and 7%for the individual nutrients.certified reference materials (vki type qc rw1 for ammonia, phosphate and nitrate) and internal reference materials for nitrite and silicate was spiked at two levels to natural low nutrient seawater sample for quality assurance, recovering 91-109% of the spike for nitrite, nitrate, phosphate and silicate at with rsd% of 1 to 5%, and recovery of 84-91% for ammonia, with rsds up to 15%. no corrections was performed on data the recoveries. except for ammonia, all results was within the acceptance limits for accredited analysis. analysis was performed over two runs, one with triplicates and then a fourth spare sample was included to investigate the ammonia instability, but it could not be determined if this was due to storage/transport or instrumentthe “.csv” files of fully processed data contain data collected mainly in the north portion of the mar in the exclusive economic zone around the azores.

本数据集是在“对中大西洋脊（MAR）沿线亚速尔群岛海域易受损害的海洋生态系统分布的综合评估”（IMAR巡航）期间生成的，该巡航于2021年5月18日至6月2日在荷兰皇家海洋研究所的科研船“Pelagia”上实施。IMAR巡航旨在评估MAR在塑造深海生物地理学纬向和跨大西洋模式、深海巨型生物群落连通性中所扮演的角色。此次远征由Eurofleets+海洋计划以及H2020欧洲项目iAtlantic资助，由亚速尔大学（葡萄牙）牵头，与葡萄牙水文研究所和波尔图大学、奥尔胡斯大学（丹麦）、英国国家海洋研究中心、德国geomar、挪威卑尔根大学博物馆、俄罗斯PP Shirshov海洋研究所以及巴西瓦莱杜伊塔雅伊大学合作进行。营养分析依照Grasshoff等人的方法进行，适用于5通道连续流动分析仪（Skalar San Plus，Skalar Analytical B. V.，布雷达，荷兰）。亚硝酸盐和亚硝酸盐+硝酸盐的测量采用氨缓冲液和磺胺/α-萘乙二胺二氢氯酸盐染料试剂在磷酸中的方法，通过镉柱至少80%的还原能力（达到90-100%），随后通过540 nm处的亚硝酸盐-偶氮染料的光谱测定进行定量。硝酸盐通过硝酸盐+亚硝酸盐与亚硝酸盐测量的差值确定。氨的测量使用柠檬酸/酒石酸盐缓冲液和苯酚染料试剂，在次氯酸盐和亚硝酸盐的存在下催化，随后通过630 nm处的苯酚-氨复合物的光谱测定进行定量。磷酸样品与草酸抗坏血酸和硫酸酸化溶液中的铵钼酸盐溶液反应，生成的络合物被抗坏血酸还原成深蓝色染料，随后通过880 nm处的还原型锑-磷-钼酸盐络合物的光谱测定进行定量。硅酸盐样品用硫酸酸化，与铵钼酸盐溶液反应，通过抗坏血酸还原成蓝色染料，并用草酸去除磷酸干扰，随后通过810 nm处的还原型钼硅酸盐络合物的光谱测定进行定量。所采用的方法经过认证，对亚硝酸盐的预期检测限为0.04 µm，对硝酸盐为0.1 µm，对氨为0.3 µm，对磷酸为0.06 µm，对硅酸盐为0.2 µm，单个营养素的预期相对标准偏差在4%至7%之间。认证参考材料（VKI类型QC RW1，用于氨、磷酸和硝酸盐）以及内部参考材料（用于亚硝酸盐和硅酸盐）在两个水平上添加到自然低营养盐海水中，以进行质量保证，亚硝酸盐、硝酸盐、磷酸和硅酸盐的添加回收率为91-109%，相对标准偏差为1%至5%，氨的回收率为84-91%，相对标准偏差高达15%。对数据恢复未进行任何校正。除氨外，所有结果均在认证分析的接受范围内。分析在两次运行中进行，一次为三重，然后添加一个额外的样品以研究氨的不稳定性，但无法确定这是由于储存/运输还是仪器引起的。“.csv”格式的完整处理数据文件主要包含在MAR北部专属经济区收集的数据。