Abstract:
Botrylloides violaceus, a colonial ascidian, is a cosmopolitan invader of fouling communities on man-made structures in harbors including Oregon’s Coos Estuary. This study documents seasonal and spatial patterns of B. violaceus distribution, assesses the impact of abiotic factors on this distribution, and characterizes the demography of this population and its interactions with other fouling organisms. I surveyed five fouling communities on docks in the Coos Estuary, and observed B. violaceus at all sites except Isthmus Slough in the upper bay. In laboratory experiments B. violaceus survived temperatures up to 27 degrees centrigrade and salinities down to 25 psu, indicating that temperature and salinity do not limit its distribution to the lower bay as hypothesized. Botrylloides violaceus overgrew all fouling species encountered on settlement plates except for sponge Halichondria bowerbanki. Understanding the interactions between B. violaceus and its abiotic and biotic surroundings is critical for improving invasive species management in the Coos Estuary.
