LAUSR

Abstract In temperate regions, macroalgae are naturally abundant habitat builders for many organisms of ecological and economic importance. Hence, macroalgae are good targets for monitoring studies based on colonization processes as, through them, it is possible to sample the epifauna that uses them as habitat. Nevertheless, macroalgae collection may not be sustainable, can compromise the survival of the target macroalgae populations and destroy fragile or threatened communities. The search for an adequate procedure that can overcome the problems related to destructive quantitative sampling of the epifauna associated with macroalgae and the development of a methodology that can be used for comparative macrofauna monitoring, regardless of the location, were the motivations for this study. The evaluation of the mobile epifauna associated with Artificial Substrates (AS) with different degrees of complexity and natural subtidal macroalgae was implemented, as a means to evaluate the viability of AS as an alternative approach for epifauna monitoring. Cystoseira baccata and Halidrys siliquosa were chosen as natural macroalgae. The hypotheses tested were (1) macroalgae and AS with similar structure will support similar assemblages of mobile epifauna; (2) different complexity AS will shelter different assemblages of mobile epifauna. The results obtained after 3 and 6 months showed that AS and macroalgae, both with similar structure, supported different assemblages of mobile epifauna, differing also when the time factor is considered. Moreover, different complexity AS supported different epifaunal assemblages. Our results also show that a period of colonization of 3 months was enough to accurately discriminate locations but the 3 additional months reinforce these differences and provide more coherent results with the species colonizing natural macroalgae in both locations studied. Hence, AS could be used as a valid, replicable, standard and representative alternative tool for monitoring studies.