Microbial films, which develop on submerged artificial surfaces, elicit variable
responses in settling invertebrate larvae. There is no information on the response
of the larvae of the tropical fouling barnacle,
Balanus reticulatus
to biofilms. Therefore, the influence of biofilms and their components
(such as bacteria, diatoms and bacterial exopolymer) on settlement of cyprid larvae
of
B. reticulatus has been studied. Biofilms significantly reduced
larval settlement when compared to clean polystyrene surfaces (control). No significant
correlation was found between percentage settlement and biofilm age. Inhibition or
induction of settlement was observed, depending on the cell density and growth phase of
the bacterial films. Diatom films, regardless of cell density, were inhibitory to
cypris settlement. Bacterial exopolymers did not influence settlement at low
concentrations (0.001 to 0.0001 %), but inhibited settlement at higher concentrations
(0.1 to 0.01%). Our study indicates that presence of natural biofilms and their
components such as bacteria, diatoms and bacterial exopolymers on polystyrene render
an otherwise attractive surface unsuitable for settlement by larvae of
B. reticulatus.
