Impact of invasive corals Tubastraea spp. on native coral recruitment

Understanding how invasive species affect ecosystem processes of coral reefs can assist reef conservation. Recruitment is a key population parameter and an important consideration in the invasive potential of non-native species. We evaluated the effects of the invasive corals Tubastraea tagusensis and T. coccinea on native coral recruitment and adult populations within distinct habitats in a southwestern Atlantic reef off the Brazilian coast. We investigated the relationships adult-adult and adult-recruit between invasive and native corals. Sixty experimental plates (20 x 20 cm) were installed for 13 mo in 2 reef habitats (reef wall and reef top) along a gradient of Tubastraea invasion. Using zero-inflated negative binomial regression models, we found that native recruit density declined with increased cover of adult invasive corals. Additionally, native adult coral cover also declined with elevated invasive cover. No significant differences were observed for native recruits (density) between habitats (reef wall and reef top) along the gradient of invasion. However, differences of native and invasive adult coral cover were found between habitats, with native coral more often found on the reef top and invasive coral widely dominant on the reef wall. Furthermore, the relationship between invasive recruitment and adult cover was significant on the reef wall. These findings reveal that coral recruitment is generally inversely related to the cover of the invasive coral Tubastraea. Unless management actions are undertaken to slow the invasion of Tubastraea, it will likely continue to impact native corals and degrade the natural values of the reef ecosystems they support.