C. proteus is a serious fouling organism. This species potentially threatens to alter natural substrates through dense colonisation, which could lead to habitat conversion, alter settlement patterns of native species and exclude algal grazers such as opihi (limpets). Competition for space with native invertebrates in the high intertidal zone is also likely to occur (DeFelice et al. 2001). At high densities the barnacle appears to negatively impact the limpet Siphonaria normalis in Hawaii (Zabin 2005).
No Impact information recorded for Chthamalus proteus