Evolucion de la monopolizacion del sustrato arrecifal en las islas del rosario por parte de las esponjas excavadoras-incrustantes del genero cliona.

Evolution of reef substrate monopolization at Rosario Islands by encrusting-excavating sponges of the genus Cliona.- In the Caribbean Sea, brown and black sponges of the genus Cliona (order Hadromerida, family Clionaidae) that both excavate and encrust calcareous substrata, have been monopolizing reef substratum in some coral reef zones during the last four decades. Upon encounter, live coral tissues are undermined and killed. To study the mechanisms of interaction and their effect on reef corals, individuals were marked and followed for 13 months, starting in 2001, and field observations and experiments were carried out at Islas del Rosario (Colombia). It was found that one particular species under study (Cliona tenuis) undermine live coral tissue from below, weakening the polyp skeletal support, and resulting in their retraction or detachment, implying considerable rates of lateral advance for the sponge. One decade later, we intend to evaluate this phenomenon again, to see if average rates of lateral advance of these sponges remained stable for the last years, and if their abundance and cover increased, as predicted by some scientists. Of particular interest are the sectors where C. tenuis has monopolized space in the now dead acropora palmata reef zone, because of the potential for dispersion of this sponge. adjacent massive corals that were invaded from sponge-carrying fragments of dead a. palmata thrown on top of them during storms might be severely affected.