A dogwhelk eating a barnacle.

Really small barnacles run the risk of being eaten by e.g. rough periwinkles and common periwinkles. Algae, waving back and forth in the waves also pose a threat by wearing on the foundation upon which the barnacle sits. Algae can also cover possible sites upon which the barnacle might attach itself.
    Onchidoris bilamellata and the green leaf worm Eulalia viridis also eat barnacles, aswell as some fish e.g. ballen wrasse .
    The Northern rock barnacle tolerates the cold very well, but ice is a real threat. Wave action upon the ice can cause a grinding effect which scapes away barnacles living close to the mean water level. First, during the spring, when the larvae have attached themselves to the rocks and grown a little, you are able to see the white belts along the cliffs again.

Kicks in its food