> In the wild, the limiting nutrient for cyanobacteria is often iron or nitrogen.
How can nitrogen be a limiting factor if ~78% of air is nitrogen? I'm assuming they also take the CO2 out of the air, which just makes up 0.04%.
How can nitrogen be a limiting factor if ~78% of air is nitrogen? I'm assuming they also take the CO2 out of the air, which just makes up 0.04%.
Taking up inorganic nitrogen is called nitrogen fixation and takes a bunch of machinery and energy. Also, oxygen inhibits the process, so for photosynthetic bacteria a bunch of extra steps have to be taken to compartmentalize photosynthesis and nitrogen fixation. So not all cyanobacteria can do it, and even the ones who are able to will prefer to take up organic nitrogen if available, and they grow slower when they have to use N2.
Nitrogen in air is not normally available to organisms. The triple bond between the 2 nitrogen atoms is very strong and takes a good deal of energy to break. Some bacteria can do this, and legumes famously have evolved to house bacteria capable of fixing nitrogen in their roots.
The main way we get nitrogen to agricultural plants today is by the industrial production of ammonia, which takes enormous amounts of energy and lots of fossil fuels as presently implemented.