OCEANARIUM A unique free-living geniculate coralline algal bed formation Frederico Tapajós de Souza Tâmega 1 & Gabriela Hannah Holligan Perna 1 & Paula Spotorno-Oliveira 1 & Rafael Riosmena-Rodríguez 2 & José Eduardo de Arruda Gonçalves 1 Received: 28 October 2015 /Revised: 14 March 2016 /Accepted: 24 March 2016 # Senckenberg Gesellschaft für Naturforschung and Springer-Verlag Berlin Heidelberg 2016 Geniculate coralline algae (GCA) are a major group of calcar- eous red algae (Corallinaceae, Rhodophyceae) with world- wide distribution, and of great importance for reef ecosystems (Benedetti-Cecchi and Cinelli 1994; Asnaghi et al. 2015) and their associated biodiversity (Chapman et al. 2005). Extensive surveys along the Arraial do Cabo Bay (23° S 42° W; Fig. 1a), SE Brazil, have shown the presence of the first record of five unique free-living GCA beds (Fig. 1b) comparable to rhodolith beds (Foster 2001). The algal beds range from depths of 6 to 20 m and are associated with gravels, coarse to fine sand and rhodoliths. The structure of the free-living GCA are uni or multi-specific and are com- posed by three species of GCA: Amphiroa beauvoisii, Jania adhaerens and Jania capillacea. These previously unknown coralline algal beds are of significance because of the branched structure thalli (Fig. 1c, d), which influences the abundance and richness of associated organisms by providing more space, refuge and resources (Steller et al. 2003). The morphology is spheroidal (Fig. 1e), comparable to the rhodolith growth form of non-geniculate coralline algae (NGCA) from shallow-water, high-hydrodynamic beds (Steller et al. 2003). Rhodolith beds formed by NGCA are well known; howev- er, GCA beds creating this unique structural formation have been previously undocumented worldwide. This newly de- scribed benthic environment may increase carbon fixation as well as habitat, refuge and grazing areas for juvenile fishes and invertebrates (Figs. 1f–i). Communicated by P. Martinez Arbizu * Frederico Tapajós de Souza Tâmega fredtamega@gmail.com 1 Departamento de Oceanografia, Instituto de Estudos do Mar Almirante Paulo Moreira, Rua Kioto 253, 28930-000 Arraial do Cabo, RJ, Brazil 2 Programa de Investigación em Botánica Marina, Departamento de Biología Marina, Universidad Autónoma de Baja California Sur, Apartado postal 19-B, 23080 La Paz, BCS, Mexico Mar Biodiv DOI 10.1007/s12526-016-0487-0