Structure and temporal dynamics of a seaweed assemblage dominated by the invasive lineage 2 of Asparagopsis taxiformis (Bonnemaisoniaceae, Rhodophyta) in the Alboran Sea

Asparagopsis taxiformis is a rhodophycean species composed of six genetic lineages, one of which is considered a relevant invasive component of the Mediterranean flora. In the present study we describe seasonal changes of the structure and biomass of the native community associated to Asparagopsis taxiformis in Granada (Southern Spain). Native community was represented by 18 Rhodophyta, 3 Chlorophyta and 4 Ochrophyta species. Biomass was dominated by A. taxiformis and Halopteris filicina. While in January A. taxiformis accounted for only 16% of the community biomass, an explosive dominance was observed only two months later, representing more than 90% of the algal biomass. Furthermore, low and generally stable values of species richness, Shannon’s diversity index and evenness were recorded during the study period. Given that A. taxiformis gametophytes are present year round, they are likely to pose a constant stress to native community development. This survey provides baseline information of macroalgal community structure useful for further studies to assess the true impact of the invasive lineage of A. taxiformis.