Inhibition and facilitation of settlement of epifaunal marine invertebrate larvae by microbial biofilm cues

Abstract

The methodologies applied in laboratory and field studies of the effects of biofilm cues on marine invertebrate larval settlement on hard substrata are briefly reviewed and some of the general problems (such as experimental repeatability, handling effects) that may be encountered, and the ecological representativeness of the species utilized are discussed. The review focuses also on the range of bioassay approaches and highlights the wide range of larval densities, substrata and biofilm sources that have been variously applied. It is important to consider all of these features in any attempt at formulating general principles and trends relating to larval settlement responses in natural assemblages. This review also highlights the prevalence of reports of facilitatory, rather than neutral or inhibitory, effects amongst the various species investigated and considers the possible role(s) of larva‐larva interactions, cue perception distances, hierarchical effects and whether or not biofilm cues are surface‐bound or waterborne in determining and affecting these responses. With specific reference to natural hard substratum assemblages, the putative adaptive significance of biofilm‐mediated facilitation and inhibition of larval settlement is assessed and additional possible lines of future research are suggested.