This project described how habitat cascades supported on rocky shore by brown canopy-forming seaweeds were shaped in presence of epiphytes, respectively as primary and secondary habitat formers. In line with the other projects, here I tested how the presence of the secondary habitat former can create habitat cascades and affect the local epifaunal. Nevertheless, in this project the two key features consisted in (i) testing the effects of three similar looking primary habitat formers simultaneously (the brown seaweeds Cystophora spp.) and (ii) testing the effects of ecologically more similar primary and secondary habitat formers compared to the previous projects (here both seaweeds), i.e., able to provide analogous benefits.
This study described a rocky shore habitat cascade, based on the interaction between the seaweeds Cystophora spp. and the epiphytes naturally supported, addressing the following hypothesis:
(1) three congeneric Cystophora species support similar abundances, taxonomic richness and community structure of gastropods;
(2) presence of epiphytes on Cystophora changes community structures and increases abundances and richness of gastropods, i.e. that epiphytes provide HC on Cystophora species;
(3) these HCs occur over a wide range of spatio-temporal conditions, including across latitudes and between reefs and seasons;
(4) epiphyte biomass and epiphyte ‘type’ (here whatever the epiphyte is alive or an artificial mimic) modify the strength of HCs, with larger gastropod abundances and richness for living and abundant epiphytes (in part because many gastropods are herbivores that may consume the epiphyte);
(5) the gastropod communities and habitat cascades associated with Cystophora host are very different when compared with gastropods communities associated with the morphologically and taxonomically very different H. banksii host.