Marine community effects of two colonial zoanthids in intertidal habitats of the Canary Islands

Rising ocean temperatures as consequence of climate change has led to increased populations of species with tropical affinities, generating a tropicalization process of the biota. In this sense, an increase in populations of the zoanthids Palythoa canariensis and Zoanthus sp. is expected for the Canary Islands being able to change local habitats and biodiversity. Within this study the potential of these species to modify the composition of their associated fauna in intertidal pools of the Canaries was assessed. The composition and biodiversity of communities in intertidal habitats dominated by P. canariensis and Zoanthus sp. were compared with habitats dominated by macroalgae. Samples were collected in order to quantify the mesofauna, and coverage of algae and zoanthids colonies were assessed. Results showed significant differences in the composition of the associated fauna between both kind of habitats, as well as an increase in species diversity and richness in habitats dominated by colonies of both zoanthids. The high potential of P. canariensis and especially of Zoanthus sp. to transform the habitat and associated communities of invertebrates in intertidal environments of the Canary Islands was demonstrated. Given the expected climate change scenario for the future that will benefit the expansion of these key zoanthids, important changes in the biodiversity and potential alterations in natural ecosystems are expected for the Archipelago.