I'm the tooth decay angel, a right-winger who won't compromise on morning shampooing, but there's nothing that can't be washed away with body soap.
This time, I'm going to continue introducing the biggest challenge of my life.
The ecosystem of Mini-Earth is maintained by the circulation of various substances in a sealed aquarium.
The circulation of oxygen and carbon, or "respiration and photosynthesis," is something that immediately comes to mind. However, when planning an experiment that lasts for 10 years or so, and with soil, that is, when there are anaerobic areas in the aquarium, I thought it would be insufficient if I didn't also consider the circulation of nitrogen.
Oxygen and carbon cycle 1
Oxygen consumption and carbon dioxide generation by respiration in animals, etc.
Oxygen generation and carbon fixation by photosynthesis in plants.
Animal respiration (omitted).
Oxygen and carbon cycle
(food chain) 2
Animals eat plant remains and new shoots. Or they eat phytoplankton.
Carbohydrates, which are products of photosynthesis, and nitrogen from plants are absorbed by animals.
Animals excrete ammonia Nitrogen cycle
When animals die, they are decomposed by microorganisms, and oxygen is consumed in the process, often producing carbon dioxide, but I think hydrogen sulfide is also produced in anaerobic environments.
Nitrogen cycle 1
(The accepted theory on water production)
Animals release ammonium ions.
Bacteria convert them to nitrite ions.
Another bacteria convert them to nitrate ions.
Plants absorb them as nutrients.
Phytoplankton and new shoots are eaten by animals.
Animals absorb them.
Nitrogen cycle 2
In the nitrogen cycle 1, some of the nitrogen is released as nitrogen molecules by the action of anaerobic bacteria.
This is what is called denitrification, and it is what aquarists who aim to have a water-change-free aquarium have been pursuing.
Although it is a naturally occurring reaction, it is generally thought that it is not easy to cause or control it on a large scale.
Denitrification does not occur on a large scale unless it is intended, but if the Mini-Earth experiment continues for about 10 years, there is a possibility that nitrogen molecules will gradually accumulate in the atmosphere.
Some kind of mechanism is needed to return nitrogen to the water!
That is Azolla.
This duckweed lives in symbiosis with cyanobacteria, and despite being an aquatic plant, it is able to fix nitrogen (absorb nitrogen molecules from the air as nutrients).
Note: One type of Azolla is designated as a specified invasive species and is prohibited from using in aquariums.
The Azolla used in this experiment was determined to be a domestic species.
Nitrogen cycle 2 + α
In the nitrogen cycle 1, some of the nitrogen is released as nitrogen molecules by the action of anaerobic bacteria.
However, some of this is taken up by azolla and is returned to the water when the azolla dies or is eaten by aquatic organisms.
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