Impact of Local Iron Enrichment on the Small Benthic Biota in the deep Arctic Ocean

Impact of Local Iron Enrichment on the Small Benthic Biota in the deep Arctic Ocean The study assesses the impact of local iron enrichment on the small benthic biota (bacteria, meiofauna) together with environmental parameters indicating the input of food at the deep seafloor. To evaluate the hypothesis that abundance, distribution, and diversity of the small benthic biota varies in relation to a local input of structural steel at the seabed, we analyzed sediment samples and the associated infauna along a short transect with increasing distance to an iron source, i.e., corroding steel weights (plates) of a free-falling observational platform (bottom-lander), lying on the seafloor for approximately seven years. Iron-enriched surface sediments in the vicinity of the bottom-weight left in summer 2008 after a short-term deployment of a bottom-lander in 2433 m water depth at the LTER (Long-Term Ecological Research) observation HAUSGARTEN in eastern parts of the Fram Strait were sampled on 28th July 2015 using push-corer (PC) handled by the Remotely Operated Vehicle (ROV) QUEST 4000 (MARUM Center for Marine Environmental Sciences, Germany) during Dive 369 from board RV Polarstern. During sampling in 2015, the plates were largely corroded. Surface sediments around the plates had an orange-red color with a gradient of decreasing color intensity with increasing distance from the source, i.e., the bottom weight. A total of eight push-corer samples (PC1-8) were taken at approx. regular distances (on average every 18 cm) along a short transect (about 1.5 m) crossing the iron gradient. Push-corers PC1-4 retrieved sediment from heavily impacted sediments, while samples taken from push-corers PC5-8 were visually indistinguishable from background sediments in the wider area. After recovery of the ROV, sediment cores (8 cm in diameter, and 20-25 cm in height) were sub-sampled using plastic syringes with cut-off anterior ends for meiofauna and nematode communities as well as for environmental parameters. The position specified in the data sets (longitude / latitude) refers to the position of the ROV. The uploaded datasets contain meiofauna (major taxonomic groups) abundances (ind. / 10 cm²) (Meiofauna.xlsx), for the nematodes (genera) abundance (ind. / 10 cm²) and biomass (µg dry weight / 10 cm²) are given (Nematoda.xlsx). Data on environmental parameters are given for FE content (iron content in the sediments), H2O (water content in sediments as parameter for porosity), AFDW (ash free dry weight of sediment as parameter for total organic matter content in sediments), Chloroplastic pigments (chlorophyll a) and its degradation products (phaeopigments) as parameter for the input from phytodetritus sedimentation. The bulk of pigments, defined as chloroplastic pigment equivalents, CPE (Environmental parameters.xlsx). All data are given for the top 5 sediment centimeters (sediment cores were sectioned in 1-cm layers down to 5 cm sediment depth).

《北冰洋深海局部铁富集对小型底栖生物的影响》 本研究评估了局部铁富集对小型底栖生物群落（细菌、小型底栖动物（meiofauna））以及指示深海海底食物输入的环境参数的影响。为验证“小型底栖生物的丰度、分布与多样性会随海底钢结构输入物质的不同而变化”这一假说，我们沿着一条距铁源——即一处已锈蚀的自由沉降式观测平台（海底着陆器）的配重钢块（钢板）——距离递增的短断面，分析了沉积物样本及相关联的底内生物。该配重钢板已在海底放置约7年。

2008年夏季，一台海底着陆器在弗拉姆海峡东部LTER（Long-Term Ecological Research，长期生态研究）观测站HAUSGARTEN的2433米水深海域短期布放后，其海底配重于同年夏季被遗留。2015年7月28日，依托德国海洋环境科学中心（MARUM Center for Marine Environmental Sciences）的远程操作潜器（Remotely Operated Vehicle，ROV）QUEST 4000，随“北极星号”（RV Polarstern）科考船执行第369次下潜任务，使用推杆式采泥器（push-corer，PC）对该区域的铁富集表层沉积物进行了采样。

2015年采样时，钢板已基本锈蚀。钢板周边的表层沉积物呈橙红色，且距配重越远，颜色强度越弱，呈现出明显的浓度梯度。我们沿着一条长约1.5米、横穿铁浓度梯度的短断面，以约18厘米的平均间隔，共采集了8个推杆式采泥器样本（PC1-8）。其中PC1-4采自受铁富集严重影响的沉积物，而PC5-8的沉积物在视觉上与周边区域的背景沉积物无明显差异。

回收远程操作潜器后，我们使用截去前端的塑料注射器，对直径8厘米、高度20-25厘米的沉积物岩心进行分样，以用于小型底栖动物、线虫群落及环境参数的分析。数据集中标注的位置（经度/纬度）指的是远程操作潜器的作业位置。

本次上传的数据集包含：1. 小型底栖生物（主要分类类群）丰度数据（单位：个体/10 cm²）（"Meiofauna.xlsx"）；2. 线虫（属级分类单元）的丰度（单位：个体/10 cm²）与生物量（单位：微克干重/10 cm²）数据（"Nematoda.xlsx"）；3. 环境参数数据，包括沉积物铁含量（FE）、沉积物含水率（作为孔隙度的表征参数）、无灰干重（AFDW，用于表征沉积物总有机质含量）、叶绿素类色素（叶绿素a）及其降解产物褐藻素（作为植物碎屑沉降输入的表征参数），以及叶绿素类色素等效物（CPE）（"Environmental parameters.xlsx"）。所有数据均对应沉积物顶部5厘米层位（沉积物岩心被切割为1厘米厚的分层，直至5厘米沉积物深度）。