Diazotroph community succession during the VAHINE mesocosm experiment (New Caledonia lagoon)

A study conducted in the low-nutrient, low-chlorophyll waters of the Noumea lagoon (New Caledonia) revealed that unicellular cyanobacterial Group C (UCYN-C) exhibited rapid growth under specific conditions, reaching among the highest net growth rates reported for diazotrophs. The VAHINE mesocosm experiment demonstrated that UCYN-C became dominant in response to fertilization with dissolved inorganic phosphate (DIP), despite low abundances outside the mesocosms. This suggests that DIP fertilization and increasing temperatures created favorable conditions for UCYN-C growth, while other diazotrophs like heterocyst-forming Richelia associated with Rhizosolenia (Het-1) dominated early in the experiment. The study also highlighted a diverse field population of diazotrophs in the lagoon, including two ecotypes of Braarudosphaera bigelowii symbiont unicellular group A (UCYN-A), with UCYN-A2 being more abundant than UCYN-A1.

Turk-Kubo, K. A., Frank, I. E., Hogan, M. E., Desnues, A., Bonnet, S., & Zehr, J. P. (2015). Diazotroph community succession during the VAHINE mesocosm experiment (New Caledonia lagoon). Biogeosciences, 12(24), 7435–7452. https://doi.org/10.5194/bg-12-7435-2015