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Competition for CH4 and O2

This section discusses how the model handles competition for the limited resources of methane (CH4) and oxygen (O2) between different processes.

Key points:

- For each time step, the model calculates the unlimited demand for CH4 and O2 in each depth interval.
- If the total demand for one of the species exceeds the available amount, the demand from each associated sink process is scaled down proportionally to ensure non-negative concentrations.
- Since methanotrophs are limited by both CH4 and O2, the more limiting factor is applied first, and then the limitations are scaled back for the other processes.
- The competition is designed so that the sinks cannot exceed the available concentrations over the time step.
- If negative concentrations occur after the transport step, the O2 concentrations are reset to zero, and the CH4 surface flux is adjusted, setting the concentration to zero if the adjustment is not too large.

The key purpose is to ensure that the sinks do not deplete the available CH4 and O2 beyond what is physically possible, while balancing the demands of the different processes.