PARENT SESSION
Contributed Oral Session 9: Marine Ecology: Disturbance; Dispersal; Recruitment
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 519 A, Level 5, Palais des congrès de Montréal
Differences in successional forces in a marine fouling community are ameliorated over time.
terHorst, Casey*,1, 2, Dudgeon, Steve2, 1 Florida State University, Tallahassee, Florida, USA2 California State University, Northridge, Northridge, California, USA
ABSTRACT- Competition and colonization are important forces governing succession in many communities. However, the relative importance of each of these forces varies both temporally and spatially. Disturbances create patches of different sizes and spatial patterns, within which the relative importance of competition and colonization may vary depending on resources, edge effects, and the successional state of the patch. Community composition and resource levels change throughout succession, altering the role that competition and colonization play. Settlement plates were deployed off Santa Catalina Island, California and a fouling community was allowed to establish. Disturbances varying in magnitude and spatial pattern were imposed in situ and the abundance of each species was recorded for six months within the disturbed patches, as well as in undisturbed control patches. Percent covers of the two most abundant species were initially higher in larger disturbances and lower in smaller disturbances. Later in succession, there was no difference in species abundances between disturbance treatments. Early in succession, colonization likely controls abundances in large disturbances, where resources (i.e space, in such sessile organisms) are plentiful. However, as resources become depleted, the role of colonization is usurped by competition. In small disturbances, competition is likely more important since resources are limiting even early in succession. Watersipora subtorquata was the most abundant species in all treatments. Despite reported invasions in the eastern and southwestern Pacific, including northern and central California, W. subtorquata has not been previously documented in southern California. If W. subtorquata is a poor competitor, it is only likely to invade successfully when colonization is favored. Large disturbances that create such conditions are rare in southern California, but may be more frequent in northern and central California, and may explain the success of the invasive species on the settlement plates and in these other regions.
Key words: succession, competition, colonization, Watersipora subtorquata