Any person eligible to vote for the election of a member of the board of trustees and who meets the qualifications for the office may seek election to the office and serve if elected. For purposes of determining eligibility to seek office as a member of the board of trustees, the required creditable service in "the system" shall include each system administered by the board of trustees in which the person is a member. The members described above and serving on the board on June 30, 1989, shall continue to serve on the board until the expiration of their terms.