All officers and employees of the Geo. L. Smith II Georgia World Congress Center Authority, established by Code Section 10-9-3, who are not already members of the retirement system may elect to become members on or after April 1, 1977. Any officer or employee of the authority who is already a member of the retirement system by virtue of services with another employer shall be entitled to credit for his services and shall not suffer any loss of such credit to which he is otherwise entitled. There shall be paid from funds appropriated or otherwise available for the operation of the Geo. L. Smith II Georgia World Congress Center Authority all employer contributions required under this chapter, including employer social security contributions. The commencement date shall be April 1, 1977.