Attachment of Balanus amphitrite larvae to biofilms originating from contrasting environments

Abstract

This study examined the attachment response of Balanus amphitrite larvae to bacteria- dominated biofilms originating from 4 sites of varying environmental conditions in the intertidal region of subtropical Hong Kong waters and during 2 seasons (winter and summer), under both laboratory and field conditions. Using multiple fingerprinting techniques (terminal restriction frag- ment length polymorphism, denaturing gradient gel electrophoresis and fluorescence in situ hybri- dization), we observed differences in the bacterial community composition of biofilms originating from the 4 sites. These biofilm samples were used to study the linkage between spatial changes in bacterial communities of biofilms and larval choice at the time of attachment. It was hypothesized that cyprids can distinguish biofilms originating from habitats that support higher recruitment. Both laboratory and field multiple-choice bioassays demonstrated that cyprids preferred to attach on biofilms originating from habitats where recruitment, juvenile growth and survival were the highest, thereby accepting the hypothesis proposed. This study did not identify particular bacterial species or groups in biofilms that attract or inhibit larval attachment, but we could correlate site-specific varia- tions in bacterial community composition with larval choice, whereas bacterial abundance in biofilms was less important in this regard. Overall, this study highlights the significance of site-specific variation in biofilms on larval recruitment and demonstrated the discriminative behavior of barnacle larvae to biofilms originating from contrasting environments in the intertidal region. Thus, attach- ment cues from biofilms may also play a significant role in generating spatial variation in larval recruitment.