I have been reading some literature on measurements related to biofilms.
In some articles the word "substrate" seems to stand for the material on which a biofilm is growing. In other articles, it seems to stand for the nutrients that are freely floating in (say water) where the biofilm is growing, and which then diffuse into the biofilm and which it uses to grow.
Have I misunderstood something or are both of these meanings in active use? Is there a disciplinary or some other difference that determines who uses which term?
- The review article  uses substrate to mean freely floating nutrietnts. Also, searching for "substrate loading" or "substrate loading rate" or such (on Google scholar) gives examples of substrate as something that is fed to the biofilm.
- For example Wikipedia uses the other meaning of substrate: https://en.wikipedia.org/wiki/Substrate . Scientific literature with this meaning can be related to how easily biofilms detach from a given material in the presence of shear forces.
 Harald Horn and Susanne Lackner. Modeling of biofilm systems: A review. In Kai Muffler and Roland Ulber, editors, Productive Biofilms, pages 53–76. Springer International Publishing, Cham, 2014.