Under-ice fauna, sea-ice concentration, sea-ice thickness and under-ice water parameters from the Eurasian central Arctic Ocean during POLARSTERN cruise ARK-XXVII/3 (PS80) in August-September 2012@en

Arctic sea-ice decline is expected to have a significant impact on Arctic marine ecosystems. Ice-associated fauna play a key role in this context because they constitute a unique part of Arctic biodiversity and transmit carbon from sea-ice algae into pelagic and benthic food webs. Our study presents the first regional-scale record of under-ice faunal distribution and the environmental characteristics of under-ice habitats throughout the Eurasian Basin. Sampling was conducted with a Surface and Under-Ice Trawl, equipped with a sensor array recording ice thickness and other physical parameters during trawling. We identified 2 environmental regimes, broadly coherent with the Nansen and Amundsen Basins. The Nansen Basin regime was distinguished from the Amundsen Basin regime by heavier sea-ice conditions, higher surface salinities and higher nitrate + nitrite concentrations. We found a diverse (28 species) under-ice community throughout the Eurasian Basin. Change in community structure reflected differences in the relative contribution of abundant species. Copepods (Calanus hyperboreus and C. glacialis) dominated in the Nansen Basin regime. In the Amundsen Basin regime, amphipods (Apherusa glacialis, Themisto libellula) dominated. Polar cod Boreogadus saida was present throughout the sampling area. Abrupt changes from a dominance of ice-associated amphipods at ice-covered stations to a dominance of pelagic amphipods (T. libellula) at nearby ice-free stations emphasised the decisive influence of sea ice on small-scale patterns in the surface-layer community. The observed response in community composition to different environmental regimes indicates potential long-term alterations in Arctic marine ecosystems as the Arctic Ocean continues to change.北极海冰消退预计将对北极海洋生态系统造成显著影响。在此背景下，与冰共生的动物群发挥着关键作用：它们既是北极生物多样性的独特组成部分，还能将海冰藻类中的碳源传递至水层与底栖食物网中。本研究首次提供了整个欧亚海盆（Eurasian Basin）冰下动物群分布与冰下生境环境特征的区域尺度记录。本次采样采用水面与冰下拖网（Surface and Under-Ice Trawl）完成，拖网搭载了传感器阵列，可在拖网作业期间记录海冰厚度及其他物理参数。我们识别出两类环境域，其分布大致与南森海盆（Nansen Basin）和阿蒙森海盆（Amundsen Basin）相契合。南森海盆环境域相较于阿蒙森海盆环境域，具有更厚的海冰覆盖、更高的表层盐度以及更高的硝酸根+亚硝酸根浓度。整个欧亚海盆内共发现物种丰富的冰下群落，涵盖28个物种。群落结构的变化体现了优势物种相对贡献的差异。桡足类（Copepods，包括北极大哲水蚤<Calanus hyperboreus>和格陵兰大哲水蚤<C. glacialis>）在南森海盆环境域中占据优势；在阿蒙森海盆环境域中，端足类（Amphipods，包括Apherusa glacialis和Themisto libellula）占据主导地位。北极鳕（Boreogadus saida）在整个采样区域均有分布。在冰覆盖站位以与冰共生的端足类占优，而在邻近的无冰站位，群落优势类群突变为浮游端足类（T. libellula），这一现象凸显了海冰对表层群落小规模分布格局的决定性影响。本次观测到的群落组成对不同环境域的响应，表明随着北冰洋持续变化，北极海洋生态系统可能发生长期改变。