Cambio temporal en la estructura de la comunidad coralina del área de santa marta - Parque Nacional Natural Tayrona (Caribe Colombiano)

Several predictions have been made, about magnitude and direction of temporal changes in the coral community structure, during the last decade. However, few studies have demonstrated it quantitatively. In order to document such changes, the coral community structure was studied in four continental reefs in the Colombian Caribbean, two in the Santa Marta region: Punta Betín (PB) and Morro Grande Island (MO), and two in the Tayrona National Natural Park (PNNT): Granate cove (GR) and Gayraca bay (GA). Coral composition and cover were quantified in 2002 and compared to base line studies from 1989 (PB, MO & GR) and from 1992 (GA). These variables were quantified by 20 m linear transects between 1.5 m and 29 m depth. After a decade, all reefs lost in average 13.8 % absolute coral cover (with respect to the total of the bottom) and 42 % relative coral cover (with respect to the total of coral bottom). Composition changed through time in the four sampled reefs by decreasing the number of genera and increasing the number of species. The change in genera ranged between 8 and 18% and in species between 27 and 68 % due to the presence/absence of species in samples. Nevertheless, neither the richness nor the diversity showed significant differences for any of the reefs. Montastrea cavernosa y M. annularis are still the dominant species in the community with relative coral cover higher than 20 %. Quantified richness and absolute coral cover during 2002 followed the degradation gradient documented in the past, being the values smaller in the Santa Marta's reefs and higher in the Tayrona's. However, absolute percentage coral cover lost showed an inverse pattern, being PB (6 %) the least affected, followed by MO (12.6 %), GR (14.6 %) and being GA (22 %) the most affected. Dead coral in PB and MO was replaced by sponges which cover increased significantly over time; meanwhile in GR and GA, dead coral doesn't seem to have been replaced by other groups. The scleractinian coral cover lost suggests a significant temporal change in the community structure toward a grater degradation state, which might be shifting reef's function.