Spread of Caulerpa cylindracea impacts: The colonization of Atlantic intertidal communities

Abstract

The occurrence of the invasive macroalga Caulerpa cylindracea in the intertidal macroalgal communities of the Atlantic Ocean is evaluated here for the first time. The Canary Islands (28.36N, 16.07W) are the only distribution area known in the Atlantic for this species, and the presence of this species has currently only been reported in subtidal environments. The objectives of this study were to determine the variables influencing the species’ abundance in the intertidal zone, to delimit the colonized habitats and to assess its impact on invaded communities. The distance to the lower tidal limit, the sediments abundance and substrate type were the main variables related to the abundance of C. cylindracea. The results show that populations of C. cylindracea are restricted to certain habitats, and the existence of synergies between sedimentation and communities invaded by C. cylindracea, i.e., articulated coralline algae (Corallina caespitosa, Jania adhaerens) on platforms of the lower eulittoral and filamentous algae (Melanothamnus sphaerocarpa) in rocky pools of the middle and upper eulittoral. In these habitats the comparison of the communities impacted and not impacted by C. cylindracea (based on a data set of all species and functional groups) showed changes in the structure of the communities via replacement and a reduction in the native species abundance. However, in terms of the total macrophyte cover, species richness and diversity, no significant changes were detected.