The effect of surface polymer chain mobility on the settlement of marine larvae

Synthetic polymers, polydimethylsiloxane (a silicone) and polyethylene oxide, exhibit mechanical surface properties which repel fouling organisms. Experimental surfaces were prepared and exposed to marine larvae in the laboratory and the field. Mobility of the polymer surface was measured as either elastic modulus, E$\sp{*}$, or as proportional to receding contact angle by captive bubble technique. Laboratory experiments with Bugula neritina (Bryozoa) larvae showed a decline in larval settlement with an increase in mobility of the surface of silicone samples. A similar settlement pattern was exhibited in the field by Polydora ligni (Polychaeta), Membranipora sp. (Bryozoa), and several Protozoa. Polyethylene oxide samples inhibited settlement of Semibalanus balanoides (Cirripedia) in the field. Similar results in two unrelated compounds suggest a common mechanism. Polymer coatings which are too deformable may place insufficient stress on the mechanosensory cells of a larvae to trigger settlement.