A district may raise revenue by levy of an annual tax not to exceed forty-five cents per thousand dollars of assessed value against the assessed valuation of the taxable property in such port district for general port purposes, including the establishment of a capital improvement fund for future capital improvements, except that any levy for the payment of the principal and interest of the general bonded indebtedness of the port district shall be in excess of any levy made by the port district under the forty-five cents per thousand dollars of assessed value limitation. The levy shall be made and taxes collected in the manner provided for the levy and collection of taxes in school districts of the first class.