Exotic sun corals or cup corals (Tubastraea coccinea Lesson, 1829 and T. tagusensis Wells, 1982) have invaded sessile biological communities on rocky shores at Ilha Grande Bay, Rio de Janeiro, Brazil. Artificial structures (piers, docks or decks) were selected at four sites in Ilha Grande and compared with natural substrates on the adjacent rocky shore by quantifying the density of each species of Tubastraea, as well as the percentage coverage of the benthic biota. The overall average density of Tubastraea tagusensis was 80.3 individuals.m-2, about double that of T. coccinea. Both invasive species modified the structure of the invaded communities as relative abundance and richness of the species changed due to their presence. Tubastraea coccinea was more abundant on artificial substrates than on natural ones but no difference was detected in the abundance of Tubastraea tagusensis between substrates. The abundance of both species also varied with depth and site and a positive relation between artificial substratum age and abundance of the corals was observed. Apparently T. tagusensis is competitively superior to T. coccinea with a greater ability to occupy/invade native communities on natural substrates. Both species showed high competitive potential and can use artificial substrates to start to establish in new areas.
Biological invasion; competition; community; density; Scleratinia
