Antagonism between invasive pest corals Tubastraea spp. and the native reef-builder Mussismilia hispida in the southwest Atlantic

The biological invasion of the scleractinian corals Tubastraea coccinea and Tubastraea tagusensis into the Atlantic has resulted in their juxtaposition with native reef corals. We used microcosm and field experiments to investigate and separate the effects of chemical vs. physical mechanisms potentially responsible for observed antagonistic interactions between the invasive corals and the endemic (southwest Atlantic) reef-building coral Mussismilia hispida. In the short term microcosm experiment M. hispida extruded a substantial amount of mesenterial filaments in an aggressive response to proximity to both invasive species within a few hours. However, in the field only the native coral suffered necrosis, which was visible after only four days. The use of physical barriers to separate chemical and physical effects demonstrated that antagonistic effects were far greater in the absence of a physical barrier than in the partial or complete barrier treatments, so although there is evidence that these invasive corals may produce allelochemicals against possible competitors we demonstrated that the main mechanism Tubastraea spp uses to exclude the native coral species is principally a rapid physical response.