Vivendo com o inimigo: competição entre os corais invasores Tubastraea spp. e a esponja Desmapsamma anchorata na Baía de Ilha Grande, RJ

Abstract

Invasive species have transformed many ecosystems through changes in community structure, food chain, nutrient cycling and sedimentation. The interspecific competition often occurs between native and introduced species, and is a key process in the efficiency of invasion. This competition may result in changes in the role of species within the community and change ecosystem processes. The corals Tubastraea tagusensis and Tubastraea coccinea invaded Brazil in the 80s, and are favored by the lack of predators in the local biota, with an sponge Desmapsamma anchorata the only organism identified as an inhibitor of the growth and development of these corals. The objectives of this study is: 1) quantify and classify five categories of interaction: overgrowth, contour, peripheral contact, interactions with up to 5cm, and 5 to 10cm distance between sponges and Tubastraea spp. in the Ilha Grande Bay, 2) Describe the mechanisms used in the competition between the sponge D. anchorata and Tubastraea corals (physical or chemical?) 3) Describe the dynamic growth of the sponge D. anchorata in relation to abiotic factors. Were found 37 sponge species interacting with Tubastraea spp., and only 12 of those species interact more than 10% of the total interactions were observed. The peripheral contact and interaction of up to 5 cm were the most commonly found types of interaction. D. anchorata was a sponge that had more overlap contact. It was not observed significant effects of Tubastraea spp. extracts on D. anchorata and also not in extracts of D. anchorata on the metabolism of corals. The overlap was the main mechanism used in defense against the invasive coral, while Tubastraea spp. used physical and probably chemical defense. D. anchorata showed no relationship between growth and abiotic factors and showed growth at different rates during different months, with a peak in September decreasing until his death in December. In the case of competition between invasive Tubastraea spp. and the sponge D. anchorata , the hypothesis of biotic control cannot be taken into consideration, because the corals Tubastraea spp. have demonstrated ability to expand and colonize new sites very quickly. However, as observed in this study and other studies, the sponge wins the competition with the invaders corals