Overlooked and widespread pennate diatom-diazotroph symbioses in the sea

Abstract

Nitrogen depletion in the ocean provides a favourable niche for nitrogen-fixing cyanobacteria, which can form symbioses with eukaryotic algae. This study reports the discovery of two distinct marine pennate diatom–diazotroph symbioses, which had previously only been observed in freshwater environments and represent an overlooked but widespread source of bioavailable nitrogen in marine habitats.