Global Patterns in Marine Phytoplankton Diversity inferred from Species Distribution Modeling

Oceanic phytoplankton comprise a phylogenetically diverse array of taxa, but their diversity patterns on the global scale are currently poorly understood. We provide a global description of phytoplankton diversity by means of quantifying species richness as a function of environmental parameters using species distribution models (SDMs) and presence observations from the Global Biodiversity Information Facility (GBIF) and the MARine Ecosystem DATa (MAREDAT) project. Model set-ups of differing complexity are used to characterize the richness of functional (e.g., silicifiers, calcifiers) and taxonomic phytoplankton units (e.g., diatoms, coccolithophores, or cyanobacteria). Our results show that the ecological niches of major phytoplankton taxa are sequentially shifted along the temperature gradient and that latitudinal richness gradients and their respective drivers differ between diatoms and coccolithophores. Total integrated phytoplankton diversity varies strongly as a function of ocean basin, latitude and season, highlighting that possible links between diversity and ecosystem function may need to be investigated across a range of different spatio-temporal scales.