Records of backscatter and vertical velocity obtained from moored Acoustic Doppler Current Profilers (ADCP) enabled new insights into the dynamics of deep scattering layers (DSLs) and diel vertical migration (DVM) of mesopelagic biomass between these deep layers and the near-surface photic zone in the southern Norwegian Sea. The DSL exhibits characteristic vertical movement on inter-monthly time scales, which is associated with undulations of the main pycnocline between the warm Atlantic water and the underlying colder water masses. Timing of the DVM is closely linked to the day-night light cycle—decent from the photic zone just before sunrise and ascent immediately after sunset. Seasonal variations are also evident, with the highest DVM activity and lowest depth averaged mean volume backscatter strength (MVBS) during spring. This suggests that both oceanographic and optical conditions are driving the complex dynamics of pelagic and mesopelagic activity in this region. We hypothesize that the increased abundance of calanoid copepods in the near-surface layer during spring increases the motivation for vertical migration of pelagic and mesopelagic species, which therefore can explain the increased DVM activity during this season.

中文翻译：

---

来自挪威南部 ADCP 后向散射数据的远洋和中远洋散射体的垂直迁移

从系泊的声学多普勒海流剖面仪 (ADCP) 获得的反向散射和垂直速度记录使我们能够对深散射层 (DSL) 的动力学和这些深层与近地表光带之间的中层生物量的垂直迁移 (DVM) 的动力学有了新的认识在挪威南部海域。DSL 在月间时间尺度上表现出特征性的垂直运动，这与温暖的大西洋水和下方较冷的水团之间的主要火山口的波动有关。DVM 的时间与昼夜光循环密切相关——在日出前的光区和日落后立即上升。季节性变化也很明显，春季 DVM 活动最高，深度平均平均体积反向散射强度 (MVBS) 最低。这表明海洋和光学条件正在推动该地区中上层和中层活动的复杂动态。我们假设春季近地表层中海藻类桡足类丰度的增加增加了远洋和中远洋物种垂直迁移的动力，因此可以解释这个季节 DVM 活动的增加。