Dispersal of post-larval macrobenthos in subtidal sedimentary habitats: Roles of vertical diel migration, water column, bedload transport and biological traitsʹ expression

Post-larval dispersal along the sediment–water interface is an important process in the dynamics of macrobenthic populations and communities in marine sublittoral sediments. However, the modes of post-larval dispersal in low energy sublittoral habitats have been poorly documented. Herein we examined the specific dispersal mechanisms (diel vertical migration, water column, and bedload transport) and corresponding biological traits of the dispersing assemblage. At two sublittoral sites (sheltered and exposed) along the northern coast of Chile, we installed different trap types that capture benthic organisms with specific modes of dispersal (active emergence and passive water column drifting) and also by a combination of mechanisms (bedload transport, passive suspension and settlement from the water column). Our results show that even though there were common species in all types of traps, the post-larval macrobenthic assemblage depended on specific mechanisms of dispersal. At the sheltered site, abundant emerging taxa colonized sediments that were placed 0.5 m above the bottom and bedload-transported invertebrates appeared to be associated to the passive drifting of macroalgae. At the exposed site, assemblage dispersal was driven by specific mechanisms e.g. bedload transport and active emergence. At both sites the biological traits “small size, swimming, hard exoskeleton, free living and surface position” were associated to water column and bedload dispersal. This study highlights the importance of (i) the water–sediment interface for dispersal of post-larvae in sublittoral soft-bottom habitat, and (ii) a specific set of biological traits when dispersing either along the bottom or through the water column.