Abstract In 2016, approximately 1800 previously unobserved seabed domes were found in high-resolution acoustic soundings of the Lumparn Bay in the Aland Islands, northern Baltic Sea. As similar geological features have only rarely been reported in earlier literature globally, the aim of this study was to characterize the domes, to investigate their geochemical composition, as well as to determine if they had any effects on the composition of the benthic fauna. The domes were generally about 1 m high and had a diameter of 20–30 m, while the largest ones were up 60 m in diameter. The domes resembled the initial processes in pockmark formation where gas is trapped under the sediment surface, doming the sediment upwards. However, no pockmarks were found in the area, indicating that doming does not result in pockmark formation. High sulphur concentrations indicate hydrogen sulphide formation within the dome field area while large zones with acoustic blanketing (acoustic interference) also indicate the occurrence of gas, most likely formed in biogenic processes. Concentrations of chromium, copper, cadmium, zinc, lead, mercury and arsenic showed some differences in character between the domes and reference sites. In general concentrations varied less in the domes and were somewhat higher in the reference sites. Comparison with sediment data from the Gulf of Finland revealed that heavy metal concentrations were on low levels in the Lumparn Bay. The non-metric multidimensional scaling (NMDS) showed some, although not significant, differences between the benthic invertebrate communities of the domes and the reference sites.

中文翻译：

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波罗的海北部奥兰群岛 Lumparn 湾气穹的分布和特征

摘要 2016 年，在波罗的海北部奥兰群岛 Lumparn 湾的高分辨率声学探测中发现了大约 1800 个以前未观察到的海底圆顶。由于类似的地质特征在全球早期文献中很少报道，因此本研究的目的是描述圆顶的特征，调查它们的地球化学成分，以及确定它们是否对底栖动物群的组成有任何影响。圆顶一般高约 1 m，直径为 20-30 m，而最大的圆顶直径可达 60 m。圆顶类似于麻点形成的初始过程，其中气体被困在沉积物表面下，使沉积物向上形成圆顶。然而，在该区域没有发现麻点，表明圆顶不会导致麻点形成。高硫浓度表明在穹顶区域内形成了硫化氢，而具有声覆盖（声干扰）的大区域也表明存在气体，最有可能在生物成因过程中形成。铬、铜、镉、锌、铅、汞和砷的浓度在圆顶和参考点之间显示出一些不同的特性。一般而言，圆顶中的浓度变化较小，而参考点中的浓度略高。与芬兰湾的沉积物数据进行比较后发现，Lumparn 湾的重金属浓度处于较低水平。非度量多维标度 (NMDS) 显示圆顶和参考地点的底栖无脊椎动物群落之间存在一些尽管不显着的差异。