Modes of Byssal Failure in Forced Detachment of Zebra Mussels

Abstract

Microscopic observations of the detached byssal apparatus have confirmed that the substrate plays a direct role in determining the strength of adhesion of zebra mussels. Depending on the material, 20–95% of byssal plaques detached intact due to failure of the adhesive bond with the substrate. The forces required to remove individual mussels from plates of stainless steel, mild steel, polyvinylchloride (PVC), Teflon and concrete were measured using both a direct tensile pull-off test and a wall-jet apparatus in which mussels are swept from the substrate using a jet of water. In each case the detached mussels were subsequently dissected in order to determine the mode of failure of the byssal apparatus, i.e., thread rupture, plaque adhesive failure, and root failure. It was found that the force required to detach the mussels varied significantly among the different materials and was directly proportional to the percentage of broken byssal threads.