Meiofauna communities from iron-enriched sediments at LTER HAUSGARTEN during POLARSTERN cruise PS93

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 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. The block-shaped steel bottom-weights (30 x 30 x 6 cm) were sitting about half of the height sunken into the seafloor and thus, almost not affecting near-bottom currents. 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.

北极深海局部铁富集对小型底栖生物的影响
本研究评估了北极深海局部铁富集对小型底栖生物（细菌、小型底栖动物（meiofauna））的影响，同时结合指示深海海底食物输入的环境参数开展分析。为验证“小型底栖生物的丰度、分布及多样性会随海底结构钢的局部输入发生变化”这一假说，我们沿一条距铁源（即一处已在海底放置约7年的自由降落式观测平台（bottom-lander）的锈蚀钢配重）距离递增的短断面，对沉积物样品及相关底内动物开展了分析。
2008年夏季，一台海底着陆器在弗拉姆海峡东部长期生态研究（Long-Term Ecological Research, LTER）站点HAUSGARTEN的2433米水深区域进行短期布放后撤离，其遗留的锈蚀钢配重周边的铁富集表层沉积物，于2015年7月28日通过由德国海洋环境科学中心（MARUM Center for Marine Environmental Sciences）的遥控无人潜水器（Remotely Operated Vehicle, ROV）QUEST 4000操作的活塞式采泥器（push-corer，简称PC）采集，本次采样为极星号科考船（RV Polarstern）第369次下潜任务。
该块状钢制海底配重尺寸为30×30×6 cm，约一半高度沉入海底，因此几乎不会影响近底流场。2015年采样时，配重钢板已发生大面积锈蚀，其周边表层沉积物呈橙红色，且颜色强度随距铁源（配重）距离的增加而逐渐减弱。
本次研究共沿一条长约1.5米的短断面，以约18厘米的平均间隔采集了8个活塞式采泥器样品（PC1~PC8），覆盖该铁浓度梯度断面。其中PC1~PC4采自受铁富集严重影响的沉积物，而PC5~PC8的沉积物在外观上与周边区域的背景沉积物无明显差异。
回收遥控无人潜水器后，我们使用前端裁切的塑料注射器，对直径8 cm、高度20~25 cm的沉积物岩心进行分样，分别用于小型底栖动物及线虫群落分析，以及环境参数测定。本数据集所标注的经纬度位置，均对应遥控无人潜水器的作业位置。