Deep scattering layers (DSLs) play an important role in pelagic food webs, and are inhabited by the world’s most abundant invertebrates. Recent research has begun to reveal latitudinal, longitudinal and bathymetric patterns that overturn the original belief in homogeneous horizontal layers. The Strait of Gibraltar represents one of the most important oceanic gateways in the world and is a key place in the exchange of water masses between the Mediterranean and the Atlantic, but its pelagic ecosystem is poorly known. Its changing bathymetry and associated water currents, both at the surface and in deeper waters, result in a very dynamic environment prone to influence the organisms that inhabit it. Further, the permanent upwelling area in the Alboran Sea and the numerous mud volcanoes that spread around the Gulf of Cadiz are known to provide nutrient remineralization deep in the water column. This study extends knowledge on the spatial dynamics of DSLs layers around the Iberian Peninsula by analysing migrant and non-migrant organisms along a path between the eutrophic upwelling area on the Northwest-Atlantic coast of the Iberian peninsula and the oligotrophic Mediterranean sea on the east side. Four distinct zones were encountered (Atlantic waters, Gulf of Cadiz, Alboran Sea and Mediterranean waters). A 7–8 months time lag with primary production was found for surface and migrant layers that are closely linked to surface dynamics, although upwelling diversity is reflected in their distribution patterns. Patchiness in migrant species west of the Iberian peninsula could be related to intermittent pulses of chlorophyll as well as to eddies developed in the Gulf of Cadiz. On the other hand, non-migratory layers are hardly connected with surface dynamics and are more influenced by deeper processes such as deep currents, intermediate nepheloid layers or water masses boundaries. This study provides further insight into the environmental variables relevant in the interaction between physical and biological processes in the mesopelagic realm. It emphasizes clear differences in the way migrant and non-migrant organisms are linked to the seascape, and presents areas with very distinct distributions and proportions between the two groups. All the above should be taken into account when making global assumptions about mesopelagic species as well as when planning surveys with scattered stations employing tools such as net or optic samplings.

深散射层（DSL）在远洋食物网中发挥着重要作用，并且栖息着世界上最丰富的无脊椎动物。最近的研究已经开始揭示纬度、纵向和测深模式，这些模式推翻了均匀水平层的原始信念。直布罗陀海峡是世界上最重要的海洋门户之一，也是地中海和大西洋之间水团交换的关键场所，但其中上层生态系统却鲜为人知。无论是在表面还是在更深的水域，其不断变化的水深测量和相关的水流导致了一个非常动态的环境，容易影响居住在其中的生物。此外，阿尔沃兰海的永久上升流区域和加的斯湾周围分布的众多泥火山可以在水体深处提供营养物再矿化。这项研究通过分析伊比利亚半岛西北大西洋海岸富营养化上升流区域和东侧贫营养地中海之间路径上的迁徙和非迁徙生物，扩展了对伊比利亚半岛周围DSL层空间动态的了解。 。遇到了四个不同的区域（大西洋水域、加的斯湾、阿尔沃兰海和地中海水域）。尽管上升流的多样性反映在其分布模式中，但与地表动态密切相关的地表层和迁移层的初级生产存在 7-8 个月的时间滞后。伊比利亚半岛以西迁徙物种的斑块状分布可能与叶绿素的间歇性脉冲以及加的斯湾形成的涡流有关。另一方面，非迁移层与地表动力学几乎没有联系，而更多地受到更深层次过程的影响，例如深海流、中间霞云层或水团边界。这项研究提供了对中层领域物理和生物过程之间相互作用相关的环境变量的进一步见解。它强调了迁徙生物和非迁徙生物与海景的联系方式的明显差异，并呈现了两个群体之间分布和比例截然不同的区域。在对中层物种进行全球假设时，以及在规划使用网络或光学采样等工具对分散站点进行调查时，应考虑到上述所有内容。