nodularia nodularia nodularia is a genus of filamentous nitrogen-fixing cyanobacteria, or blue-green algae. they occur mainly in brackish or salinic waters, such as the hypersaline makgadikgadi pans, the peel-harvey estuary in western australia or the baltic sea. nodularia cells occasionally form heavy algal blooms. some strains produce a cyanotoxin called nodularin r, which is harmful to humans. nodularia satellite image of a large bloom of nodularia swirling in the baltic sea scientific classification domain: bacteria phylum: cyanobacteria class: cyanophyceae order: nostocales family: aphanizomenonaceae genus: nodulariamertens 1822 species nodularia armorica nodularia harveyana nodularia sphaerocarpa nodularia spumigena the type species for the genus is nodularia spumigena mertens ex bornet & flahault, 1886. morphology nodularia may form solitary filaments or groups of filaments. they reproduce by the formation of hormogonia, filament breakage, and by akinetes .