Mapping global phytoplankton community structure and diversity from space for ecosystem insights

Phytoplankton are essential to marine ecosystems and the global carbon cycle, with their structure, diversity, and functions influenced by a complex mix of biotic and abiotic factors. Yet, the link between phytoplankton diversity and ecosystem functioning is still poorly understood, largely due to limited data on global phytoplankton diversity patterns. This study uses satellite-based measurements, machine learning, and metagenomic datasets from Tara Oceans to bridge the gap between genetic information and global-scale ocean monitoring from space. This approach allows us to map phytoplankton groups and their environmental drivers, providing a new lens for defining marine biogeographical provinces. Our findings suggest that the relationship between phytoplankton diversity and ecosystem functioning in terms of primary production varies globally, revealing three distinct regimes: negative correlations in high-latitude, nutrient-rich ecosystems; positive but saturating effects near nutrient-rich coastal areas; and strong positive links in nutrient-poor, open-ocean regions. By establishing these relationships, our work paves the way for further remote-sensing-based biodiversity assessments. Ultimately, this research offers a framework for understanding and predicting ecosystem responses to global change, which can support sustainable ocean management and conservation strategies.