Distribution, population structure and settlement preference of Tubastraea spp. (Cnidaria: Scleractinia) on rocky shores of the Cagarras Islands Natural Monument and surroundings, Rio de Janeiro, Brazil

Tubastraea coccinea and T. tagusensis are invasive corals that have well-established populations along the broad Brazilian coasta. Over a decade of field surveys (2010–2021) in the Cagarras Islands Natural Monument, a no-take Marine Protected Area (MPA), and surroundings in Rio de Janeiro metropolitan region, the colonization processes of Tubastraea spp. has been followed up. In 2019, Tubastraea spp. population structures were determined by photoquadrats on Comprida (CO) and Cagarra (CA) islands, where patches with the highest coral densities had been detected. In laboratory, Tubastraea spp. planulation was recorded and settlement bioassays were conducted on live crustose coralline algae Lithophyllum spp. (Rhodophyta) compared to respective controls (i.e. dead Lithophyllum spp. fragments). A total of 1908 colonies of Tubastraea spp. were recorded in the photoquadrats, of which T. tagusensis represented practically all colonies (T. coccinea had a single record); thus, the analyses considered the data set for the former. The mean colonies density was 636.0 ± ind.m−2, composed mainly by founder polyps, and the mean cover was similar for CO (9.3%) and CA (13.9%) islands. Most of the founder polyps settled on crustose coralline algae — CCA (63.0%), followed by CCA/Turf (24.4%). Higher incidence of founder polyps on CCA (Lithophyllum spp.) indicates the importance of this algal functional group for the recruitment and colonization of T. tagusensis. Planulation was similar for both species and planulae preferred to settle and metamorphose on live Lithophyllum spp. These results on coral–algae interactions will contribute to enhance control/ management actions of Tubastraea spp. on Brazilian rocky shores.