Some types of cyanobacteria can thrive anywhere there is light, moisture and CO2,even polar bear coats.
Cyanobacteria and diazotrophs like them are often credited with enabling life on the planet. Primordial slime ; they not only oxygenate via photosynthesis but they also uniquely fix nitrogen ,created in the stars, from the athmosphere and bring it into the food chain where it is used for creating proteins and things like dna.It helps to think of the nitrogen( nitrification/ denitrification cycle ) as a circle rather than a line ending with N2 ,nitrogen gas since the gas is drawn back in eventually via the action of the diazoroph's nitrogenase enzyme.
Cyanobacteria form heterocysts in their biomass. These are anoxic chambers where an enzyme uniquely produced by these bacteria called nitrogenase which does not work in the presence of oxygen , fixes the nitrogen to hydrogen bringing into the food chain. It does this by breaking the strong bond between the 2 nitrogen atoms that form N2, nitrogen gas and making N available which links up with H forming things like ammonia NH3/4 thus making essential nitrogen bio available.
So cyano not only consumes nitrogen and phosphate when it's available ; it can produce fixed nitrogen and add it to the system when its not readily available.
Having said that I suspect the cyano sometimes reported with carbon dosing has less to do with nitrogen deficiencies than it does with the by products of activity by other bacteria which may be feeding it or by less phytoplankton and other competitors for nutrients hanging around or upwelling on rock surfaces or substrates. .
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