Unraveling Variations in Deep Scattering Layers: Insights from the Iberian Peninsula waters and Beyond

Marian Peña

The vertical distribution of deep scattering layers has been mainly linked to light, oxygen, and nutrient levels in the literature, while their intensity is often described in terms of surface temperature and primary production. However, recent studies reveal variations based on latitude and longitude, bathymetry, and, more importantly, on migration behaviour, that is, genus or families. This talk aims to summarize the current knowledge adding some new discoveries around the Iberian peninsula. Upwelling characteristics, currents, salinity, spiciness and intermediate nepheloid layers will be also discussed. Research around the Iberian Peninsula identified four main zones: Atlantic waters, Gulf of Cadiz, Alboran Sea, and Mediterranean waters. Species in contact with the surface (epipelagic or migratory species) within these zones are related to local primary production while no correlation is found for non-migratory species, more influenced by deeper processes that are probably intricately linked to more distant shore processes. Recognizing these differences is crucial for understanding ocean life in the meso- and bathypelagic zone as well as for global model tuning. Finally, patchiness versus continuous layers in the mesopelagic community and potential causes will be highlighted.