Barnacles, limpets and periwinkles: the effects of direct and indirect interactions on cyprid settlement and success

It is concluded that periwinkles can affect the settlement and success of barnacles directly through biological disturbance (i.e. surface ablation). However, although limpets may have a direct negative effect on barnacle settlement and success, at low to medium densities, limpets can positively indirectly influence the cyprid settlement and success. This effect operates at a factor greater than that afforded by the direct negative effects of periwinkles in a mixed-species treatment. These results illustrate how the indirect effects of one species on another can have a more important structuring effect than those derived from direct effects alone.