Diving into warming oceans: Assessing 3D climatically suitable foraging areas of loggerhead sea turtles under climate change

Abstract

Climate change impacts on marine species have been mainly studied considering only the sea surface despite the fact that most species depend on habitats at different depths. With sea temperatures warming unevenly across depths, identifying critical marine habitats while considering the three-dimensionality of the seascape is a major conservation challenge. Unfortunately, this research field remains largely unexplored and only few examples permit the identification of vertically coherent areas. Here, we developed a climate niche-based framework to delineate critical areas across different depths and assess their consistency over space and time. We use loggerhead sea turtles as a model species to identify climatic suitable areas for the present and future three-dimensional marine space of the Mediterranean Sea, using temperatures from three bathymetric layers of 5 m, 25 m and bottom neritic waters. We analyzed both juvenile and adult sea turtles, which use different depth-related habitats. Our analysis revealed that the coherence among thermal suitable habitats of different depths varied across the different life stages. Although near-surface habitats of juvenile sea turtles spanned across a vast area of the Mediterranean, their water-column habitats were spatially restricted. Near-surface, deep and water-column habitats of adults shared similar distribution patterns. Under future conditions, all types of three-dimensional habitats seemed to primarily maintain thermal stability, however, even opposite changes were predicted for different depths. Our study provides an advanced spatial mapping of sea turtle habitats, highlighting the significance of the three-dimensional marine space and how the selection and combination of specific bathymetric zones may impact patterns in distribution.