Occurrence of cyanobacteria - diatom symbiosis in the Bay of Bengal: Implications in biogeochemistry

Abstract

Diazotrophs (N sub(2) fixing organisms), mainly belonging to cyanobacteria, form a major group of phytoplankton in nutrient poor oligotrophic oceans. These organisms support non-diazotrophic phytoplankton community and primary production by the release of fixed nitrogen (N sub(2)) into the marine environment and thereby play an important role in the biogeochemistry of oligotrophic environments. Trichodesmium spp., a colony-forming cyanobacterium and Richelia intracellularis Schmidt, a cyanobacterial endosymbiont of several diatom genera, are the most important diazotrophs accounting for approx. 63% of pelagic N sub(2) -fixation in the world’s oceans. However, information on R. intracellularis is lacking, even though its distribution is widespread.