Distributions and Abundances of Sublineages of the N 2 -Fixing Cyanobacterium Candidatus Atelocyanobacterium thalassa (UCYN-A) in the New Caledonian Coral Lagoon

Nitrogen (N ) fixation is a major source of nitrogen that supports primary production in the vast oligotrophic areas of the world's oceans. The Western Tropical South Pacific has recently been identified as a hotspot for N fixation. In the Noumea lagoon (New Caledonia), high abundances of the unicellular N -fixing cyanobacteria group A (UCYN-A), coupled with daytime N fixation rates associated with the