Substrate type as a selective tool against colonization by non-native sessile invertebrates

Abstract

Different substrates of varying composition, color, texture and orientation may selectively influence recruitment of sessile invertebrates and thereby influence the resultant community. Thus substrates may act as a barrier to the establishment of non-indigenous species (NIS). In southern Brazil, granite is the main rock forming natural rocky walls that are available for encrusting organisms. In this study we tested whether granite selectively influences recruitment and impedes colonization by introduced and cryptogenic species that are already established on artificial substrates within the region. Plates of rough cut granite and of polyethylene were made available each month under a pier at a yacht club in Paranaguá Bay. A community is already established on concrete columns and fiber glass floats on the piers. After one, two and twelve months, the faunal composition of the plates was compared between the two treatments and other artificial substrates. Granite was recruited by all the seven introduced species found in the Bay and by 18 of 26 cryptogenic species and therefore is ineffective as a barrier to NIS colonization.