Marine biofouling field tests, settlement assay and footprint micromorphology of cyprid larvae of Balanus amphitrite on model surfaces

Atomic force microscopy (AFM), laboratory settlement assays and field tests were used to correlate cyprid footprint (FP) morphology with the behaviour of cyprids on different substrata. AFM imaging under laboratory conditions revealed more porous and larger FPs on glass exposing a CH3-surface than on aminosilane functionalised (NH2-) surfaces. The secreted FP volume was found to be similar on both substrata (2.1-2.6m3). Laboratory settlement assays and marine field tests were performed on three substrata, viz. untreated clean glass, NH2-glass, and CH3-glass. The results distinguished settlement preferences for NH2-glass and untreated glass over CH3-terminated surfaces, suggesting that cyprids favour settling on hydrophilic over hydrophobic surfaces. On combining observations from different length scales, it is speculated that the confined FP size on NH2-glass may induce a higher concentration of the settlement inducing protein complex. Settlement may be further facilitated by a stronger adherence of FP adhesives to the NH2-surface via Coulombic interactions.