The effects of small fish presence on a species-poor community dominated by omnivores: Example of a size-based trophic cascade

► A small fish produces a trophic cascade on plankton of a Mediterranean salt marsh. ► Omnivory has an important role in these food webs. ► The trophic cascade is a result of size-dependent interactions amongst organisms. ► Aphanius iberus has weak but positive effect on macrophyte biomass.