Initial contact, exploration and attachment of barnacle (Balanus amphitrite) cyprids settling in flow

Settlement responses of barnacle (Balanus amphitrite ) cyprids to boundary-layer flows were examined in laboratory flume-experiments. The leading-edge configuration of flat plates was altered in order to manipulate flows without changing surface topography or free-stream velocity. Settlement along the plates correlated strongly with downstream gradients in shear stress. Analyses of video images taken during the experiments indicate that cyprids first contact plates in regions where plate-ward advection is high, and subsequent exploratory movement along the plate is oriented with flow direction at the plate surface. After exploration, cyprids reject a surface more frequently in a fast flow (10 cm/s free-stream velocity) than in a slow flow (5 cm/s), but rejection occurs in shear stresses well below the threshold that would prevent attachment and exploration.