Long-term coral colonization by an excavating Caribbean sponge

Dead Acropora palmata branches colonized by the excavating sponge Cliona tenuis are prone to dislodgement, breakage, and translocation during heavy surge and swell from storms or hurricanes, favoring the dispersion of this sponge. At Islas del Rosario (Colombia, Caribbean), adult C. tenuis carried by A. palmata fragments that fell onto live massive corals were able to colonize the new coral, subsequently killing live tissue of the newly invaded coral. Corals that recruited onto fallen A. palmata branches overgrown with adult C. tenuis were also invaded once the sponge reached their base. To determine if the incidence of this phenomenon has increased since 2002 when it was first documented, the mode and prevalence of colonization of corals by C. tenuis was again quantified in 2014 on the same reef. Although a trend is difficult to infer from two surveys, the number of coral colonies colonized by C. tenuis doubled by 2014, and new cases of colonization from sponge-carrying A. palmata branches were found. However, the frequency of colonization by adult sponges from A. palmata branches in 2014 was one-half to one-fifth lower than in 2002, demonstrating that other forms of colonization onto massive corals may be increasing, or that storms erase the evidence of adult colonization by translocating vector coral branches, as was observed in one monitored case of transmission. As time passes and the fragmentation and erosion of the reef increases, the evidence of colonization of stony corals by C. tenuis through A. palmata branches vanishes.