Appointments and promotions in the service of a statutory strong-mayor-council city shall be made solely on the basis of merit and fitness; and removals, demotions, suspensions and layoffs shall be made solely for the good of the service. The council by ordinance may establish a merit system and provide for its organization and functioning, and provide for personnel administration and regulations of personnel matters. If and when the council establishes a merit system, it shall create a personnel department, the head of which shall be a personnel director appointed by the mayor for an indefinite term. The mayor may serve also as personnel director.