A Slice of San Francisco Bay

The Academy's project to inventory all the bottom-dwelling animals in the San Francisco Bay, called "SF Bay: 2K," is revealing some interesting creatures.

Sessile animals start out as free-floating plankton and require a surface on which to attach in order to grow and reproduce. They may fasten themselves to anything hard and secure such as rocky bottoms. When an assemblage like this one collected from San Francisco Bay takes up residence on something human-made like ships' hulls, pier pilings, or even ropes, it's called a "fouling community."

Ciona intestinalis, a solitary tunicate and filter feeder, taking water and food particles into one siphon and ejecting the filtered water from another.
Photo credit: Allyn G. Smith


Encrusting sponge typical of those found in San Francisco Bay. Photo credit: Sherry Ballard

Introduced and native organisms typically found in such communities in the Bay include large, balloonlike sea squirts (tunicates) and tiny ones that look like colorful mats of bubbles; shell-dwelling mussels (genus Mytilus); hydroids, which look like small ferns or vines; and various species of colorful sponges and anemones.

This community of creatures is a tiny sample of what SF Bay:2K coordinator Rich Mooi, project managers George Brooks and Roberta Ayres, teachers, students, and several volunteers are finding in the Bay in the Academy's effort to identify and classify all its bottom-dwelling animals.

A small tunicate which develops encrusting colonies. Academy archives, photographer unknown.