January 1, 2010.
Settlement among native and invasive marine organisms in fouling communities was observed at various time intervals in the San Francisco Bay. Many of these well-known, globally invasive organisms grow rapidly and often outcompete or overgrow natives. Settlement plates were placed at three different protected areas within the Bay (Richmond Marina Bay Yacht Club (1), Berkeley Marina (2), and Fort Baker (3)) and scored once a week for 5 weeks. The two larger East Bay sites (1 and 2) showed considerably greater species diversity and abundance in comparison to the smaller site near the mouth of the Bay (site 3). Furthermore, at the Easy Bay sites, algal cover gradually decreased as animal diversity and abundance progressively increased. Species including Didemnum sp., Balanus glandula, Watersipora subtorquata, white encrusting bryozoan, and white branching bryozoan showed significant settlement differences in initial recruitment density on empty plates deployed in the 1st versus the 3rd week. Recruitment on the plates appeared to show a priority effect where the earliest settlers (colonial tunicates and Bugula neritina) were consistently the most abundant species present each subsequent week. Measuring the growth and abundance of the invasive organisms is important to study because they are altering the habitats and opportunities for native organisms to persist.
Romberg Tiburon Center for Environmental Studies (RTC)