A Triangle Model: Environmental Changes Affect Biofilms that Affect Larval Settlement

Biofilms are ubiquitous — covering every exposed surface in marine environment and thus playing a key role in mediating biotic interactions and biogeochemical activities occurring on the surfaces. For the propogates of marine organisms, biofilm attributes serve as inhibitive or inductive cues for the attachment of settling larvae and algal spores of potential colonizers. Microbes in biofilms are not only the sources of chemical cues but also consumers of chemical cues. As microbes in biofilm are very sensitive to changes in ambient environment, the production of chemical cues by the microbes will change in response to spatio-temporal variation of microbial density, community structure, topography, dynamics, and the microbial physiological conditions in biofilms. These lead to changes in physical and chemical biofilm properties and in the bioactivity of biofilm for attachment of marine propogates. While there have been a number of reviews on the effect of biofilms on settlement of marine invertebrate larvae and algal spores, the effects of environmental changes on microbial community structure dynamics and bioactivities of biofilms remain much unexplored. Recent advances in molecular fingerprinting techniques have made it possible to precisely study the linkage between environmentally driven changes in biofilms and larval settlement. We are now gaining a better picture of the triangle relationship between environmental variables, biofilm dynamics and bioactivity, and the behavior of settling larvae or spores of marine organisms. Here, we would like to formally introduce a triangle model to provide a conceptual framework for interactions between environmentally induced biofilm changes that in turn affect the settlement of dispersal propogates.