The city council in a city under the commission plan of government shall have, possess, and exercise, by itself or through such methods as it may provide, all executive or legislative or judicial powers and duties previously held, possessed, or exercised under the then existing laws governing such city, by the mayor, mayor and city council, water commissioners, water board, water and light commissioner, board of fire and police commissioners, park commissioners, or park board. The powers, duties, and office of all such boards and the members thereof shall cease and terminate, and the powers and duties and officers of all other boards created by statute for the government of any such city shall also cease and terminate. Nothing contained in this section shall be so construed as to interfere with the powers, duties, authority, and privileges that have been, are, or may be hereafter conferred and imposed upon the water board in cities of the metropolitan class as prescribed by law nor of any office or officer named in the Constitution of Nebraska exercising office, powers, or functions within any such city. Such city council, upon taking office, shall have and may exercise all executive or legislative or judicial powers possessed or exercised by any other officer or board provided by law for or within any such city, except officers named in the Constitution of Nebraska.