Mapping marine plankton abundance along ecological gradients in the South Brazilian Shelf.

Plankton communities form the foundation of marine food webs, determining the ecosystem carrying capacity and the services they provide. Their spatial distribution patterns are highly dynamic, influenced by ocean stratification, mixed layer depth, and nutrient availability. In this study, we combined an advanced imaging system with a machine learning model to explore how environmental factors shape plankton distribution on the South Brazilian Shelf. We selected four representative categories (Rhizaria, Diatoms, Copepoda and Gelatinous) to encompass the broader diversity of planktonic groups. Our three-dimensional predictions highlight depth as a key driver for all plankton categories, while revealing taxon-specific responses to water column stratification. Gelatinous are notably confined to the mixed layer and dominate oligotrophic regions, irrespective of coastal nutrient availability. In contrast, copepods exhibit a heterogeneous and continuous distribution, with higher abundances near nutrient-rich coastal areas. These contrasting patterns underscore the intricate dynamics of plankton communities and reinforce the need for detailed investigations to better understand their ecological roles and responses to environmental changes.