No improvements shall be acquired or constructed by the port district unless such improvements shall, when completed, be the property of such port district, the county in which such port district is located, any commercial waterway district created within its boundaries, any city within such port district, the state of Michigan, or the United States of America, and the funds of such port district may be expended in the acquirement or construction of any harbor improvement embraced in such general plan adopted as in this act provided, in conjunction with the county in which such port district is located, any commercial waterway district created within its boundaries, any city in such port district, the state of Michigan, or the United States of America, or any or all of them.