    """ calculates the non-living equations for DOM, POM, and nutrients """
    
    # State variables
    o2o = conc[0]              # Dissolved oxygen (mg O_2 m^-3)
    n3n = conc[2]              # Nitrate (mmol N m^-3)
    n4n = conc[3]              # Ammonium (mmol N m^-3)