Distribution of the cyanobacterium Richelia intracellularis as an epiphyte of the diatom Chaetoceros compressus in the western Pacific Ocean

The few available records on the association of the diazotroph heterocystous cyanobacterium Richelia intracellularis epiphytically with Chaetoceros compressus are restricted to the Indian and western Pacific Oceans, whereas the association of R. intracellularis as an endosymbiont in other diatoms is ubiquitous in warm oceans. From ten cruises in the western Pacific Ocean, the Richelia-Chaetoceros consortia were exclusively observed in the periphery of the geographic proliferations of C. compressus, coinciding with the overlapping area of the populations of asymbiotic C. compressus and R. intracellularis as an endosymbiont in Rhizosolenia clevei.