All directors shall serve at the pleasure of the appointing authority; provided, that notwithstanding this section and Section 27122, any director in office on the effective date of this section may continue to serve on the board until the expiration of the term for which he was appointed.

Each appointing authority shall review its appointment or appointments to the board in January every two years, and indicate its desire to retain such director or directors by affirming such retention by the adoption of a resolution, or, in the case of the Mayor of the City and County of San Francisco, by the issuance of a declaration, to that effect.