Wednesday, August 8, 2007: 9:20 AM
Almaden Blrm II, San Jose Hilton
Catherine E. de Rivera, Environmental Sciences & Management, Portland State University, Portland, OR, Edwin D. Grosholz, Environmental Science and Policy, Bodega Marine Laboratory, University of California, Davis, Davis, CA and Gregory M. Ruiz, Smithsonian Environmental Research Center, Edgewater, MD
Despite the importance of invasions, few studies have explored their consequences in marine systems beyond simple numerical impacts on native species. We surveyed the marine invasions literature and found nearly 95% of studies measured only one type of impact with the majority being numerical impacts. Moreover, most studies on invader impacts have been short term. To demonstrate that invaders can produce a broader range of impacts, we combined fourteen years of field surveys with manipulative experiments to examine multiple impacts a nonindigenous crab, Carcinus maenas, has had on a native shore crab, Hemigrapsus oregonensis, in central California. In addition to numerical impacts, we found a 60% reduction in body size as well as an eighteen-fold upward shift in the tidal distribution of H. oregonensis. Similar to studies of the persistent impacts of invasive plants on native species, we found that the effects of C. maenas on H. oregonensis -- changes in abundance, body size, and tidal distribution -- persisted for nearly a decade after the peak abundances of C. maenas. Lagged recovery of these attributes may have long-term negative effects on population growth.
