Title: Recolonization of intertidal macroalgae in relation to gap size and molluscan herbivory on a rocky shore on the east coast of southern Africa
Abstract: The low intertidal on rocky shores in the Transkei region of southern Africa is characterized by extensive turfs of coralline algae.These turfs are punctuated by small gaps maintained by patellid limpets.Recolonization of macroalgae in experimentally cleared gaps of different sizes (0.5, 0.125 and 0.03 m2) was monitored over 1 yr in an initial experiment and then repeated and monitored over a 2 yr period.All quadrats were rapidly recolon~zed by a g r e e d b r o w n algal component, consisting of Ralfsia spp., Ulva spp.. Enteromorpha spp.and Iyengaria sp.Although this component remained dominant there was some growth of coralline algae (Arthrocardia spp.and Jania spp.).Rate of recolonization was directly related to gap size, with the smallest gaps remaining relatively free of algae, and the largest showing greatest recovery after 12 mo.Even after 24 mo, however, the total algal cover was only between 10 and 50 % of that in undisturbed control quadrats.Grazer density (Patella longicosta, P oculus, Oxystele tabularis) was highest in small gaps and there was a direct relationship between the number of grazers and the ratio of bare rock to algae.A model of the interactions between grazers and algae 1s discussed in terms of human exploitation of patellid l ~m p e t s and the implications of this for lowshore community structure.